NVIS and VHF?
'Captain' Kirk DeHaan
reliably. It's cloudy now so I'm and getting a bit of ducting but I
have a lot of trees, mostly poplars, in the direct path. I would have a
line of sight if not for the trees as I'm up enough in altitude. I can
cut the trees, they're mine, but finding the right ones is difficult and
i don't want to waste the whole grove.
I go from keying the repeater with no intelligible signal to not being
able to hit it. Today I actually have an S meter reading due to the
clouds. I am currently using a J-pole and will put up a Yagi soon but
wonder if NVIS would work on 2m? I have only seen references to it
being applied in HF.
'Captain' Kirk DeHaan
N6SXR
Geoffrey S. Mendelson
> I'm living in a wooded area and am trying to hit our club repeater
> reliably. It's cloudy now so I'm and getting a bit of ducting but I
> have a lot of trees, mostly poplars, in the direct path. I would have a
> line of sight if not for the trees as I'm up enough in altitude. I can
> cut the trees, they're mine, but finding the right ones is difficult and
> i don't want to waste the whole grove.
Wait for winter and use a beam antenna to locate the tree(s) that need to be
trimmed.
If a 10 element beam won't "blast" through the trees in the summer, it should
get you down to a line of 1 or two trees that need to be cut.
A more radio oriented project would be to put a 6m or 10m input on the
repeater. 10m should groundwave over the trees anyway. It's easy enough to
test.
10m inputs are IMHO neat, at the top of the sunspot cycle, they give your
repeater worldwide input. At that point a 10m output would be good too, but
for now, it's not much of a problem.
Geoff.
--
Geoffrey S. Mendelson N3OWJ/4X1GM
It's amazing how many people have no clue what the word "contiguous" means. :-(
Wimpie
wrote:
Hello,
The repeater antenna will probably have most of its radiation in the
horizontal plane and 145 MHz is far above the critical frequency, so
your rays will leave earth.
Did you monitor the signal for several time (also winter and rain) to
assess the real influence of the trees? Do you have any possibility to
move the J-pole to another place?
As you can open the repeater now and then, some 10 dB additional gain
will certainly help you to get above the FM-knee (assuming that you
can get the beam at same height as the J-pole. Nice thing is, it will
also improve reception.
With kind regards,
Wim
PA3DJS
www.tetech.nl
remove abc first in case of PM
Sal M. Onella
wrote:
I can't see that NVIS has any VHF backers.
Can you exploit Google Maps, satellite view, to establish a precise
line bearing from your antenna to the repeater site? If you need even
more help than you get from your new yagi, then such a line bearing
will help identify your "trouble trees."
I had to do it for a new FD site a few years ago. We're in San Diego
and I wanted to work 2m into Los Angeles. First, I used a protractor
to determine LA was X-degrees True (whatever it was) from us; next, on
a close-up print of the FD site, I plotted that same line bearing from
the antenna site to obvious local landmarks which we then used on the
the ground for pointing the 2m beam.
This is not the only approach, but it got me what I needed.
"Sal"
(KD6VKW)
John KD5YI
Your yagi may fix your problem completely. Other things to consider:
* Try moving your existing antenna. Even a small movement may cure the
problem as you may have cancelling reflections at times. There is almost
always a "sweet spot" somewhere in the vicinity.
* Try tilting your antenna to 45 degrees and see if that helps. It might
improve reception due to the random polarization of the incoming signal
caused by the trees.
Note: do this on a day when the signal is either weak or non-existent.
You can always apologize for kerchunking. Or, use your S-meter if you
have one.
Cheers & Good Luck,
John
KD5YI
John KD5YI
Addendum: If you can add even a foot or two your antenna height, it may
make a world of difference.
Cheers,
John
KD5YI
Allodoxaphobia
> 10m inputs are IMHO neat, at the top of the sunspot cycle,
> they give your repeater worldwide input.
s/input/QRM/
Jeff Liebermann
<capt...@ncc-1701a.net> wrote:
>I'm living in a wooded area and am trying to hit our club repeater
>reliably.
I live in a dense mostly redwood forest. Signals vary from full
quieting to not copyable. We also have two co-channel repeaters
sharing the frequency, that also vary radically in strength. I can
often point my 5 element 2m beam in a totally insane direction, and
improve the signal.
>I go from keying the repeater with no intelligible signal to not being
>able to hit it. Today I actually have an S meter reading due to the
>clouds. I am currently using a J-pole and will put up a Yagi soon but
>wonder if NVIS would work on 2m? I have only seen references to it
>being applied in HF.
I just love technical posting with no numbers. It would be helpful if
you would offer a clue as to the distance you're trying to cover, what
manner of impervious to RF dirt is along the line of sight, antenna at
the repeater, power levels, etc. For extra credit, if you disclose
these plus your exact location, the repeater's exact location, and I
will contrive a Radio-Mobile path profile from you to the repeater.
That should give you a clue as to what challenges you are facing.
<http://www.cplus.org/rmw/english1.html>
It will look something like this:
<http://802.11junk.com/jeffl/coverage/RST/RST-KCRA.jpg>
As for a seat-of-the-pants guess as to a solution, I don't like J-pole
antennas. Actually, the antenna is fine, but the way most people
build, tune, and position them, is what I find disgusting. The lack
of any commercially manufactured J-pole antennas (other than the
American Legion J-poles) should offer a clue. Plenty of plans:
<http://www.google.com/search?q=j-pole+antenna&hl=en&prmd=ivns&tbm=isch>
but nothing from a commercial antenna manufactory.
In my never humble opinion, if you can barely talk to the repeater
with a J-pole, then a yagi will offer a substantial improvement. The
problem is how much gain is going to be needed to make it reliable. My
guess(tm) is that the J-pole has a gain of about 2.5dBi (opinions vary
on the gain), and that you'll need about 5dB more gain to get a decent
link. That means you'll need a yagi with about 7.5dBi of gain. That
can be done with a 5 element 2m yagi. Obviously, more gain is better
as is more altitude.
Good luck.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Jeff Liebermann
wrote:
>* Try moving your existing antenna. Even a small movement may cure the
>problem as you may have cancelling reflections at times. There is almost
>always a "sweet spot" somewhere in the vicinity.
I beg to differ. I have about 30 years experience in dealing with
propogation through a dense redwood forest (Ben Lomond CA). The trees
in my area are about 120ft high. While moving the antenna around may
temporarily improve the signal quality by reducing frequency selective
fading, multipath, reflections, and just plain bad luck, they do not
tend to remain improved. Trees grow and move around. What works well
now, will probably not work well tomorrow.
I gave up on fixed antenna mounts for my rooftop verticals. (Well, I
have one mounted on a tripod, but that was before I realized what was
happening). Most of my verticals are mounted on 2x12 planks, held
down to the roof with sand bags, concrete blocks, and buckets full of
water. Every few months, I move the antennas around to see if I can
improve the signals to specific repeaters.
>* Try tilting your antenna to 45 degrees and see if that helps. It might
>improve reception due to the random polarization of the incoming signal
>caused by the trees.
I beg to differ again. Tree trunks are mostly water and do an
impressive job of simulating a slot type polarization filter at 2m and
440Mhz frequencies. Leaves and branches will pass RF fairly well, but
not tree trunks. I've played with both polarizations, circular
polarization:
<http://802.11junk.com/jeffl/circular-polarization/>
and some diversity reception. Empirically, signals are about 6dB
stronger going through the trees vertically polarized, than
horizontal. The effect continues up to at least 2.4GHz. Above that,
at 5.7GHz, the signals seem to be going through the holes between the
leaves.
I must admit that I haven't actually tried 45 degrees on 2m or 440Mhz,
but I don't think it will help much. Still, it's an easy thing to
try.
>Note: do this on a day when the signal is either weak or non-existent.
>You can always apologize for kerchunking. Or, use your S-meter if you
>have one.
Do it on a windy day, when the trees are moving around, so you can see
how much it will change.
>Cheers & Good Luck,
>John
>KD5YI
--
John KD5YI
> On Sun, 22 May 2011 17:55:16 -0500, John KD5YI<sop...@invalid.org>
> wrote:
>
>> * Try moving your existing antenna. Even a small movement may cure the
>> problem as you may have cancelling reflections at times. There is almost
>> always a "sweet spot" somewhere in the vicinity.
>
> I beg to differ. I have about 30 years experience in dealing with
> propogation through a dense redwood forest (Ben Lomond CA). The trees
> in my area are about 120ft high. While moving the antenna around may
> temporarily improve the signal quality by reducing frequency selective
> fading, multipath, reflections, and just plain bad luck, they do not
> tend to remain improved. Trees grow and move around. What works well
> now, will probably not work well tomorrow.
You may be right, Jeff. But he may not have 120ft redwoods around and,
after all, this is a temporary fix until his yagi comes in.
> I gave up on fixed antenna mounts for my rooftop verticals. (Well, I
> have one mounted on a tripod, but that was before I realized what was
> happening). Most of my verticals are mounted on 2x12 planks, held
> down to the roof with sand bags, concrete blocks, and buckets full of
> water. Every few months, I move the antennas around to see if I can
> improve the signals to specific repeaters.
Good for you! Pat yourself on the back.
>> * Try tilting your antenna to 45 degrees and see if that helps. It might
>> improve reception due to the random polarization of the incoming signal
>> caused by the trees.
>
> I beg to differ again. Tree trunks are mostly water and do an
> impressive job of simulating a slot type polarization filter at 2m and
> 440Mhz frequencies. Leaves and branches will pass RF fairly well, but
> not tree trunks. I've played with both polarizations, circular
> polarization:
> <http://802.11junk.com/jeffl/circular-polarization/>
> and some diversity reception. Empirically, signals are about 6dB
> stronger going through the trees vertically polarized, than
> horizontal. The effect continues up to at least 2.4GHz. Above that,
> at 5.7GHz, the signals seem to be going through the holes between the
> leaves.
>
> I must admit that I haven't actually tried 45 degrees on 2m or 440Mhz,
> but I don't think it will help much. Still, it's an easy thing to
> try.
You spent more words debunking the suggestion than admitting that you
don't really know whether it could help or not. Good move. And, by the
way, I have experience to the contrary at both 144 and 444 MHz. It all
depends on the location of the source and the receiver. At 2 meters,
some rotation of the antenna can sometimes be helpful. Note that we are
not concerned with GHz.
John
Jeff Liebermann
wrote:
>You may be right, Jeff. But he may not have 120ft redwoods around and,
>after all, this is a temporary fix until his yagi comes in.
30 years of trying to maintain a stable signal to several distant
repeaters is sufficient to convince me. Trees move and grow, causing
signals to change.
Also, temporary is a rather useless term. In my experience, if it
works, it's permanent.
>Good for you! Pat yourself on the back.
Thank you for the traditional contentious remark.
>You spent more words debunking the suggestion than admitting that you
>don't really know whether it could help or not.
True. I spent more words explaining why I suspect it will not work,
what I expect will happen, and a bit of substantiation. I consider
this a substantial improvement over the traditional one-line
pontification.
>Good move. And, by the
>way, I have experience to the contrary at both 144 and 444 MHz. It all
>depends on the location of the source and the receiver. At 2 meters,
>some rotation of the antenna can sometimes be helpful.
Perhaps it would be helpful if you read what I had written. I said
that rotating the antenna might help temporarily, but that movements
of the trees, tree growth, swaying branches in the wind, and possibly
sources of reflections, will soon negate any temporary benefits. If
the yagi is going to arrive shortly, then tilting the antenna is
probably a useful exercise.
> Note that we are not concerned with GHz.
Topic drift follows:
Since you mentioned GHz, one of the other problems with living in the
deep dark forest is that DBS satellite dish reception is a problem. I
hacked an 8ft diameter hole in the tree canopy by lopping off some
branches at about the 80ft level, through which I point my DirecTV
dish. Every year, the trees grow a little, requiring that I move the
dish around my roof. During the twice annual solar satellite outage:
<http://en.wikipedia.org/wiki/Sun_outage>
Twice a year, I photograph the sunlight shining through the hole and
onto the dish and roof. If there are shadows of branches on the dish,
I move it to a better location.
<http://www.11junk.com/jeffl/pics/DBS/>
Note the shadow at 12 o'clock on the dish.
Jeff
If you have line of sight to the repeater I find it hard to believe that
a few trees will cause you problems at 2m.
NVIS will not work at vhf it is an HF mode. 2m signals go straight
through the atmosphere they are not reflected back down.
You don't say how far away the trees are, but if they *really are* the
cause of you problems, if they are at any distance then they will
probably all have to go to give any sort of Fresnel zone clearance at 2m.
A simple map and compass will give you the bearing to the repeater, but
perhaps you would be better off running a propagation prediction program
such as Radiomobile to see if it is actually the terrain rather than the
trees that are the problem.
73
Jeff
Jeff Liebermann
wrote:
>You may be right, Jeff. But he may not have 120ft redwoods around and,
>after all, this is a temporary fix until his yagi comes in.
Ummm... I don't think the yagi is on order.
<http://www.k7jep.org/node/107>
#Begin speculation();
His area has a variety of repeaters available:
<http://www.k7jep.org/node/107>
I would guess(tm) N7JCT 145.230 on Schweitzer Mtn. Idaho.
<http://www.repeaterbook.com/beta/repeaters/details.php?ID=64&state_id=16>
Plugging the coordinates 48.367500 -116.628326 into Google Earth gives
me a view of the area. It seems to be in the middle of a ski resort,
that has been cleared of most trees and is full of trails. Plenty of
trees both up and down the slope, but not around the probable location
of the repeater. I can't identify the trees from the photo, but my
guess(tm) is Lodgepole Pine at about 60ft. The location is not at the
top of the hill and also has hills shading the view for about 270
degrees. I don't think this is going to be a foliage penetration
issue.
KML file for Google Earth:
<http://802.11junk.com/jeffl/kml/N7JCT possible location.kml>
JPG for those without Google Earth:
<http://802.11junk.com/jeffl/kml/N7JCT possible location.jpg>
Blundering forward, N6SXR is shown as getting his snail mail in
Sandpoint ID a distance of about 7 miles. However, there's quite a
bit of dirt in the way, which will be a problem.
<http://802.11junk.com/jeffl/kml/N6SXR to N6JCT.jpg>
At 7 miles, it should be possible on VHF, even with 450ft of dirt in
the way. My guess(tm) is that there's something wrong with the home
made J-pole, coax, radio, or all the aformentioned.
Again, this is a guess(tm) of both the repeater and it's location and
just might be totally wrong.
#End speculation();
John KD5YI
> On Sun, 22 May 2011 20:56:52 -0500, John KD5YI<sop...@invalid.org>
> wrote:
>
>> You may be right, Jeff. But he may not have 120ft redwoods around and,
>> after all, this is a temporary fix until his yagi comes in.
>
> 30 years of trying to maintain a stable signal to several distant
> repeaters is sufficient to convince me. Trees move and grow, causing
> signals to change.
>
> Also, temporary is a rather useless term. In my experience, if it
> works, it's permanent.
The OP already said he will be putting up a yagi. Anthing he does
between now and then is temporary.
>> Good for you! Pat yourself on the back.
>
> Thank you for the traditional contentious remark.
You earned it.
>> You spent more words debunking the suggestion than admitting that you
>> don't really know whether it could help or not.
>
> True. I spent more words explaining why I suspect it will not work,
> what I expect will happen, and a bit of substantiation. I consider
> this a substantial improvement over the traditional one-line
> pontification.
I find it more useful to encourage experimentation rather than the opposite.
>> Good move. And, by the
>> way, I have experience to the contrary at both 144 and 444 MHz. It all
>> depends on the location of the source and the receiver. At 2 meters,
>> some rotation of the antenna can sometimes be helpful.
>
> Perhaps it would be helpful if you read what I had written. I said
> that rotating the antenna might help temporarily, but that movements
> of the trees, tree growth, swaying branches in the wind, and possibly
> sources of reflections, will soon negate any temporary benefits. If
> the yagi is going to arrive shortly, then tilting the antenna is
> probably a useful exercise.
I did read what you had written. So?
>> Note that we are not concerned with GHz.
>
> Topic drift follows:
> Since you mentioned GHz,
*You* are the one who brought it up:
"The effect continues up to at least 2.4GHz. Above that,
at 5.7GHz, the signals seem to be going through the holes between the
leaves."
Perhaps you should read what you wrote.
John
John KD5YI
> On Sun, 22 May 2011 20:56:52 -0500, John KD5YI<sop...@invalid.org>
> wrote:
>
>> You may be right, Jeff. But he may not have 120ft redwoods around and,
>> after all, this is a temporary fix until his yagi comes in.
>
> Ummm... I don't think the yagi is on order.
Now you are just being argumentative. I never said it was on order. The
OP said he was planning to put one up. Therefore, it will most likely
come in some day.
I'll bet you are still waiting for your boat to come in.
Jeff Liebermann
wrote:
>On 5/23/2011 10:46 AM, Jeff Liebermann wrote:
>> On Sun, 22 May 2011 20:56:52 -0500, John KD5YI<sop...@invalid.org>
>> wrote:
>>
>>> You may be right, Jeff. But he may not have 120ft redwoods around and,
>>> after all, this is a temporary fix until his yagi comes in.
>>
>> Ummm... I don't think the yagi is on order.
>Now you are just being argumentative.
Not really. Methinks that you're being overly defensive. My litmus
test is "duz it answer the OP's question"? If not, you're wasting
your bytes. By asking for help with the design and contruction of a
yagi, it appears that the author is planning to build his own yagi. I
haven't seen any mention of a structure, pole, or tower, so that will
also need to be constructed. Perhaps also a rotator. Methinks
temporary might be a long time.
>I never said it was on order. The
>OP said he was planning to put one up. Therefore, it will most likely
>come in some day.
At this point, I think were suppose to debate the definition of
temporary. I think I'll pass.
>I'll bet you are still waiting for your boat to come in.
Nope, no waiting. I let the computah do that for me.
<http://www.marinetraffic.com/ais/>
The station I'm slightly involved with is at:
<http://www.marinetraffic.com/ais/stationdetails.aspx?station_id=112>
Watching the VHF propagation effects are fascinating.
Jim Lux
For this kind of thing "RadioMobile" from VE2DBE is the application of
choice. It will load the SRTM terrain DEMs, etc. and plot out the path
quite nicely.
http://www.cplus.org/rmw/english1.html
But, if you can get in sometimes, but not others, the next question is,
"can you hear it"?
How long is your coax?
If more than 20 ft, are you running a preamp?
Getting 10-15 dB gain over a jpole would be easy with a moderate length
Yagi. A M2 2M4 (4 elements, $115) is about 10dBi. A 2M9($240) is about
14dBi
Wimpie
wrote:
Hello,
As you can see from the replies, we are in the speculation phase. If
you would like to receive more specialized feedback, you should
provide us with more details about the path, antenna height, nearby
obstacles, vegetation in between, etc (maybe some pictures).
As we are discussing 2 m wavelength, obstacles that may be optically
in the path may introduce less attenuation then expected, but
obstacles that are outside the optical path can still introduce
attenuation.
At 10m (33ft) from your antenna, the first Fresnel zone is about 9m
(30 ft) wide. In addition, the tree attenuation at these frequencies
is not that high. I think of 0.15 dB/m (I hope somebody can confirm
this). It can be less due to diffraction (bending) of the waves around
and over the trees.
I am almost sure, removing some poplar treetops at 10m from your
antenna or more will not change the situation from marginal to good
(because of the relative low attenuation).
Just to be curious, what type of poplar do you have at your site.
'Captain' Kirk DeHaan
> On Sun, 22 May 2011 20:56:52 -0500, John KD5YI<sop...@invalid.org>
> wrote:
>
>> You may be right, Jeff. But he may not have 120ft redwoods around and,
>> after all, this is a temporary fix until his yagi comes in.
>
> Ummm... I don't think the yagi is on order.
> <http://www.k7jep.org/node/107>
This is the repeater I am trying to access, 146.780, K7JEP. I have been
playing with Google Earth and getting coordinates so I can go over to my
neighbors property and stand on the ridge between our properties and see
if I can see the repeater and my house. Hopefully that will help me
locate the suspect trees.
>
> #Begin speculation();
>
> His area has a variety of repeaters available:
> <http://www.k7jep.org/node/107>
> I would guess(tm) N7JCT 145.230 on Schweitzer Mtn. Idaho.
This repeater is 59 on signal. I have direct line of site with no
obstructions.
> <http://www.repeaterbook.com/beta/repeaters/details.php?ID=64&state_id=16>
> Plugging the coordinates 48.367500 -116.628326 into Google Earth gives
> me a view of the area. It seems to be in the middle of a ski resort,
> that has been cleared of most trees and is full of trails. Plenty of
> trees both up and down the slope, but not around the probable location
> of the repeater. I can't identify the trees from the photo, but my
> guess(tm) is Lodgepole Pine at about 60ft. The location is not at the
> top of the hill and also has hills shading the view for about 270
> degrees. I don't think this is going to be a foliage penetration
> issue.
>
> KML file for Google Earth:
> <http://802.11junk.com/jeffl/kml/N7JCT possible location.kml>
> JPG for those without Google Earth:
> <http://802.11junk.com/jeffl/kml/N7JCT possible location.jpg>
>
> Blundering forward, N6SXR is shown as getting his snail mail in
> Sandpoint ID a distance of about 7 miles. However, there's quite a
> bit of dirt in the way, which will be a problem.
> <http://802.11junk.com/jeffl/kml/N6SXR to N6JCT.jpg>
Addresses here are not all they seem. My physical address is 14 miles
north even though the postal idiots label it in Sandpoint. Approx
location... lat 48.494070 lon -116.447788. You'll see my crazy driveway
and the house. The J-pole sits about 30' above the house. Plenty of
trees in sight.
>
> At 7 miles, it should be possible on VHF, even with 450ft of dirt in
> the way. My guess(tm) is that there's something wrong with the home
> made J-pole, coax, radio, or all the aformentioned.
>
> Again, this is a guess(tm) of both the repeater and it's location and
> just might be totally wrong.
>
> #End speculation();
>
>
--
'Captain' Kirk DeHaan
N6SXR
"Beam me up Scotty, there's no intelligent life here"
'Captain' Kirk DeHaan
> On Sun, 22 May 2011 11:04:10 -0700, 'Captain' Kirk DeHaan
> <capt...@ncc-1701a.net> wrote:
>
>> I'm living in a wooded area and am trying to hit our club repeater
>> reliably.
>
> I live in a dense mostly redwood forest. Signals vary from full
> quieting to not copyable. We also have two co-channel repeaters
> sharing the frequency, that also vary radically in strength. I can
> often point my 5 element 2m beam in a totally insane direction, and
> improve the signal.
>
>> I go from keying the repeater with no intelligible signal to not being
>> able to hit it. Today I actually have an S meter reading due to the
>> clouds. I am currently using a J-pole and will put up a Yagi soon but
>> wonder if NVIS would work on 2m? I have only seen references to it
>> being applied in HF.
>
> I just love technical posting with no numbers. It would be helpful if
> you would offer a clue as to the distance you're trying to cover, what
> manner of impervious to RF dirt is along the line of sight, antenna at
> the repeater, power levels, etc. For extra credit, if you disclose
> these plus your exact location, the repeater's exact location, and I
> will contrive a Radio-Mobile path profile from you to the repeater.
> That should give you a clue as to what challenges you are facing.
The repeater, 146.780, in on Gold Mtn., 48.219713, -116.482883 I do not
know the specs of the repeater. I am at 48.494070, -116.447788, at
2300' using an American Legion J-pole. It has worked very well in the
past but this is the first time it has been up in 15 years. It hits the
145.230 repeater on Schweitzer 59. I'm running a Kenwood 721 at 25
watts trying to hit the 780 repeater. Schweitzer can be hit at 5 watts
no problem.
> <http://www.cplus.org/rmw/english1.html>
> It will look something like this:
> <http://802.11junk.com/jeffl/coverage/RST/RST-KCRA.jpg>
>
> As for a seat-of-the-pants guess as to a solution, I don't like J-pole
> antennas. Actually, the antenna is fine, but the way most people
> build, tune, and position them, is what I find disgusting. The lack
> of any commercially manufactured J-pole antennas (other than the
> American Legion J-poles) should offer a clue. Plenty of plans:
> <http://www.google.com/search?q=j-pole+antenna&hl=en&prmd=ivns&tbm=isch>
> but nothing from a commercial antenna manufactory.
>
> In my never humble opinion, if you can barely talk to the repeater
> with a J-pole, then a yagi will offer a substantial improvement. The
> problem is how much gain is going to be needed to make it reliable. My
> guess(tm) is that the J-pole has a gain of about 2.5dBi (opinions vary
> on the gain), and that you'll need about 5dB more gain to get a decent
> link. That means you'll need a yagi with about 7.5dBi of gain. That
> can be done with a 5 element 2m yagi. Obviously, more gain is better
> as is more altitude.
>
> Good luck.
--
John KD5YI
According to his lat/lon numbers, he is 19 miles from the repeater and
its bearing is 185 degrees (ref true north) from him. The repeater is
about 2000 feet above him (not including the tower height). He is in a
valley that has little altitude variation until his signal reaches the
mountain.
This info is available from Google Earth using his numbers.
All of this leads me to think that something else is wrong. I can hit a
repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft
tower. My antenna (half wave end-fed dipole) is on a 20 ft mast.
I have tons of deciduous trees between me and the repeater but the
signal is always solid with no noise on it (I don't have an S-meter) and
I have never had a report of noise on my signal until I tried to carry
on a conversation with 200 mw output power.
Cheers,
John
nm...@wt.net
with it. That should get you over the hump well
enough to use the repeater.
You probably don't even need a rotor.
Just aim it at the bad machine, and if the
other one is as good as you say, it will likely
be usable even aimed at the other one.
Or you could use a switch to go back to the
vertical. If the coax run is long, don't use
thin coax like RG-58 or it's ilk. I consider
RG-8/213 types the minimum for anything semi
critical. And you can get better than that.
Doesn't pay to use a gain antenna if you lose
a large chunk of it in feed line losses.
Wimpie
Hello John,
With Google maps, results (distance and bearing) are similar (based on
the data given by Kirk).
If the trees south of his antenna are the problem (I am not
convinced), he needs to cut lots of them. They are about 150m from
his antenna, and at that distance first Fresnel zone width is about
30m (100ft).
It seems flat when looking to the activities in the valley. I hope
somebody can make a path profile and loss simulation to see what is
the real obstacle.
'Captain' Kirk DeHaan
I was up on my neighbors property along the path to the repeater and the
quantity of trees is a lot more than I had remembered. Since this is
tree growing/logging country it is not feasible for me to be cutting
huge amounts of trees. The deciduous can go but there are to many
conifers on both properties to cut just for signal. You are correct on
the distance to the grove and it is the, I believe, the only impediment.
>
> It seems flat when looking to the activities in the valley. I hope
> somebody can make a path profile and loss simulation to see what is
> the real obstacle.
I download the Radio Mobile SW that someone suggested but am still
trying to figure out how to use it.
>
> With kind regards,
>
>
> Wim
> PA3DJS
'Captain' Kirk DeHaan
There may well be something wrong with the antenna. I don't have an SWR
meter handy but will try and borrow one from a club member. The J-pole
was beat around quite a bit over the years but since the radio has a
limiting circuit if the SWR is too far out of whack I am assuming it is
fairly close. It will transmit of full power. I'm using 75' of
professionally assembled RG8X which is required to get from the radio to
the antenna.
>
> I have tons of deciduous trees between me and the repeater but the
> signal is always solid with no noise on it (I don't have an S-meter) and
> I have never had a report of noise on my signal until I tried to carry
> on a conversation with 200 mw output power.
Not to make light, one of these poplars is tons in itself. They are
easily 70' tall and 24" diameter. I truly appreciate all the help from
everyone.
>
> Cheers,
> John
Jeff Liebermann
<capt...@ncc-1701a.net> wrote:
>You'll see my crazy driveway
>and the house. The J-pole sits about 30' above the house. Plenty of
>trees in sight.
That's quite a drive. Thanks for the numbers. I've ignored the
antenna heights as they don't seem to make much difference. 31 km (19
mile) path length. The K7JEP repeater seems to be on a wide flat part
of a hilltop. Pointing downward, it may not clear the edge of the
flat part if the antenna isn't high enough. Difficult to tell without
photos or numbers. Not much you can do at your end to fix that. Any
chance you have a photo of the K7JEP repeater antenna location?
Otherwise, the path is line-o-sight, and should be quite usable with
your American Legion J-Pole. Of course, a yagi would be better, but I
think tinkering with your J-pole, coax, connectors, and radio may be a
better solution (assuming the repeater is working properly).
KML file:
<http://802.11junk.com/jeffl/kml/N6SXR-to-K7JEP.kml>
JPG image:
<http://802.11junk.com/jeffl/kml/N6SXR-to-K7JEP.jpg>
Hint: In Google Earth, enable 3D. When you have the KML file
displayed, stomp on the MIDDLE mouse button to tilt the image.
Jeff Liebermann
<capt...@ncc-1701a.net> wrote:
>I download the Radio Mobile SW that someone suggested but am still
>trying to figure out how to use it.
Radio-Mobile will give you the expected coverage area and signal
strengths from your location. However, it's a tricky program to
master and will require some patience and practice. There are
tutorials. For example:
<http://www.pizon.org/radio-mobile-tutorial/index.html>
<http://www.bcwireless.net/moin.cgi/RadioMobile/Tutorial>
<http://radiomobile.pe1mew.nl/>
etc.
Also check YouTube for various video tutorials.
Jeff Liebermann
<capt...@ncc-1701a.net> wrote:
>There may well be something wrong with the antenna. I don't have an SWR
>meter handy but will try and borrow one from a club member. The J-pole
>was beat around quite a bit over the years but since the radio has a
>limiting circuit if the SWR is too far out of whack I am assuming it is
>fairly close. It will transmit of full power.
The American Legion J-pole is rather critical, especially the dual
band flavor. The vertical section of electrical wire between the coax
connector and the part where it's wound around the driven element is
the tuning adjustment. Move it slightly and it's mistuned. You'll
need a VSWR meter to re-tune it.
>I'm using 75' of
>professionally assembled RG8X which is required to get from the radio to
>the antenna.
RX-8x is 4.5dB loss per 100ft. Half your power is being lost in the
coax.
'Captain' Kirk DeHaan
> On Mon, 23 May 2011 15:53:28 -0700, 'Captain' Kirk DeHaan
> <capt...@ncc-1701a.net> wrote:
>
>> You'll see my crazy driveway
>> and the house. The J-pole sits about 30' above the house. Plenty of
>> trees in sight.
>
> That's quite a drive. Thanks for the numbers. I've ignored the
> antenna heights as they don't seem to make much difference. 31 km (19
> mile) path length. The K7JEP repeater seems to be on a wide flat part
> of a hilltop. Pointing downward, it may not clear the edge of the
> flat part if the antenna isn't high enough. Difficult to tell without
> photos or numbers. Not much you can do at your end to fix that. Any
> chance you have a photo of the K7JEP repeater antenna location?
>
> Otherwise, the path is line-o-sight, and should be quite usable with
> your American Legion J-Pole. Of course, a yagi would be better, but I
> think tinkering with your J-pole, coax, connectors, and radio may be a
> better solution (assuming the repeater is working properly).
I have heard from a club member that the repeater is weak and it has
been overrun by one on the coast! He is much farther away than me and
in a much less desirable location, signal wise.
I have been out of HAM radio for about 15 years so am having to relearn
quite a lot. Had a brain injury, doh!, so lot's of what I knew went bye
bye. Lot's of holes in the memory. I will find out about the repeater
during the next club meeting. Specs and all.
>
> KML file:
> <http://802.11junk.com/jeffl/kml/N6SXR-to-K7JEP.kml>
>
> JPG image:
> <http://802.11junk.com/jeffl/kml/N6SXR-to-K7JEP.jpg>
>
> Hint: In Google Earth, enable 3D. When you have the KML file
> displayed, stomp on the MIDDLE mouse button to tilt the image.
--
Dave Platt
'Captain' Kirk DeHaan <capt...@ncc-1701a.net> wrote:
>> All of this leads me to think that something else is wrong. I can hit a
>> repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft
>> tower. My antenna (half wave end-fed dipole) is on a 20 ft mast.
>
>There may well be something wrong with the antenna. I don't have an SWR
>meter handy but will try and borrow one from a club member. The J-pole
>was beat around quite a bit over the years but since the radio has a
>limiting circuit if the SWR is too far out of whack I am assuming it is
>fairly close. It will transmit of full power.
One of the things to know about the American Legion J-pole (and most
vaguely-similar J-poles) is that it has no feedline or mount-point
isolation to speak of. The outside of the feedline coax, and any pipe
or tower or other metal to which you strap the antenna, become part of
the antenna's ground system, and can radiate a significant amount of
RF. This can interact with the RF coming from the main radiator, and
significantly alter the antenna's pattern... it no longer behaves like
an idealized half-wave vertical radiator.
In most installations this doesn't seem to matter all that much... but
it's possible that you've got some sort of weird interaction (feedline
emissions, reflections from the ground or nearby metal, etc.) which is
creating a null in the antenna's pattern in just the wrong direction.
If this is an issue (not all that likely but perhaps possible) you
could insulate the antenna from the mounting mask, and install a choke
(e.g. a few ferrite cores) on the feedline just below the antenna.
Also, the American Legion J-poles are subject to a couple of forms of
mechanical/electrical failure after a few years. The plastic
insulator which spaces apart the radiator and matching arm can degrade
(UV from sunlight is the main offendor, I believe) and crack, allowing
the two arms to change spacing. More subtly, the connection between
the two arms and the metal base can degrade... it's aluminum-to-
aluminum using a set-screw, and the connection can loosen and corrode.
It might be worth checking the spacer (replace if necessary), and
checking and tuning up the set-screw connections (squirt with Liquid
Wrench if necessary, loosen and remove, take out the rods, clean the
ends of the rods and the mounting holes in the place, dab with NoAlOx
or a similar corrosion-blocker, reassemble and tighten).
> I'm using 75' of
>professionally assembled RG8X which is required to get from the radio to
>the antenna.
That's probably costing you about half of your power (assuming a
typical RG8X-type coax). Some lower-loss types (e.g. LMR-240 are
better than this.
--
Dave Platt <dpl...@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Dave Platt
John KD5YI <sop...@invalid.org> wrote:
>All of this leads me to think that something else is wrong. I can hit a
>repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft
>tower. My antenna (half wave end-fed dipole) is on a 20 ft mast.
I wonder whether he might have his antenna sitting in a particularly
deep multipath cancellation null.
I help run a repeater located about 4 miles from my house, which is up
at about 80' AGL on a hospital roof. There's an office building
blocking direct line-of-sight path from my house to the repeater.
For a few weeks, several years ago, I found myself unable to
successfully open up the repeater using my base station, even while
transmitting 50 watts of power from a good-quality commercial 2-meter
antenna located a few feet above my roofline. Had no trouble with any
other repeater in the area, or with simplex operations. The
feedline/antenna system measured out just fine... no reflected power
worth speaking about.
I moved the antenna mast about 2' to one side, and was then able to
open up the repeater full-quieting with 100 milliwatts.
All I can figure is that there must have been a *very* deep multipath
cancellation effect playing out... maybe interference between a
edge-diffraction path involving the office building, and reflections
from nearby trees. Moving the antenna a fraction of a wavelength
changed the path lengths enough to eliminate the cancellation (or
reduce it by a large factor).
John KD5YI
> I have heard from a club member that the repeater is weak and it has
> been overrun by one on the coast! He is much farther away than me and in
> a much less desirable location, signal wise.
>
> I have been out of HAM radio for about 15 years so am having to relearn
> quite a lot. Had a brain injury, doh!, so lot's of what I knew went bye
> bye. Lot's of holes in the memory. I will find out about the repeater
> during the next club meeting. Specs and all.
Sounds great, Kirk. I'll bet they will fix you up right away.
Hang in there.
Cheers,
John
Jeff Liebermann
<capt...@ncc-1701a.net> wrote:
>I have heard from a club member that the repeater is weak and it has
>been overrun by one on the coast! He is much farther away than me and
>in a much less desirable location, signal wise.
Ok. Might be a sick repeater. That would explain quite a bit.
>I have been out of HAM radio for about 15 years so am having to relearn
>quite a lot. Had a brain injury, doh!, so lot's of what I knew went bye
>bye. Lot's of holes in the memory.
I have a slight idea of what's that's like. I had a triple bypass
operation in 2002. They're not sure what happened but the result is
that my memory around that time is like Swiss cheese. It's a mix of
things that happened that I don't remember, and things I remember that
never happened. Fortunately, things got better after about a year for
me. Hopefully, you'll do as well. Also, my neighbor had a brain
tumor removed. She's fine, but has the same scrambled memory problem.
I gave up ham radio from about 1975 to 1992. I was working designing
radios and working in commercial 2way. The last thing I needed was
ham radio after hours. Welcome back.
>I will find out about the repeater
>during the next club meeting. Specs and all.
Good idea. I assumed that you had already done that. If the specs on
the repeater (tx power, feed line losses, antenna gain, antenna
height, lat-long) were known on the repeater, I can calculate the
signal strength you should expect at your end.
John KD5YI
That is always a possibility, Dave. I have seen similar situations and I
am not surprised at your findings. It is one reason I suggested moving
his antenna, even slightly.
His latest post may also indicate that there is a repeater problem. So,
I hope he posts his findings after his meeting with his club.
Cheers,
John
Jim Lux
>
>> I'm using 75' of
>> professionally assembled RG8X which is required to get from the radio to
>> the antenna.
>
> That's probably costing you about half of your power (assuming a
> typical RG8X-type coax). Some lower-loss types (e.g. LMR-240 are
> better than this.
>
The results are all over the map. A piece of Cable TV cable might not
be a bad choice, if you can scrounge one. The 75 ohms probably isn't a
big deal.
At 144 MHz, bigger in diameter almost always beats fancier dielectric
(that is, the .405 inch RG-8, RG-213 flavors will usually beat any of
the quarter inch cables (RG-6, RG-8X, LMR240, etc.) because dielectric
losses aren't a big driver.. it's the IR loss in the center conductor.
RG-11, for instance, has less than 1.2dB loss for a matched 75 foot
line, and for the 1.5:1 mismatch, the loss only goes up 0.1 dB. (RG-11
type coax has a solid dielectric, and is pretty darn rugged stuff)
75 feet, at 144 MHz
LMR240 - 2.2 dB
Belden 8215 (RG-6A) - 2.5 dB
Belden 9258 (RG-8x) - 3.0 dB
Tandy RG-8x - 3.1 dB
Belden 8267 (RG-213) - 1.9 dB
Wireman CQ110 (RG-213) - 1.6 dB
Belden 8237 (RG-8) - 1.7 dB
belden 8213 (RG-11) = 1.2dB
John KD5YI
Huh? 75 ft of RG-11 has almost 8dB of loss at 146MHz. 75 ft of LMR240
has 9.7dB of loss at 146 MHz.
I won't go through your entire list.
Check out http://www.vk1od.net/calc/tl/tllc.php
Cheers,
John
Ralph Mowery
"John KD5YI" <sop...@invalid.org> wrote in message
news:irhhrc$ee1$1...@dont-email.me...
>>
>> 75 feet, at 144 MHz
>> LMR240 - 2.2 dB
>> Belden 8215 (RG-6A) - 2.5 dB
>> Belden 9258 (RG-8x) - 3.0 dB
>> Tandy RG-8x - 3.1 dB
>> Belden 8267 (RG-213) - 1.9 dB
>> Wireman CQ110 (RG-213) - 1.6 dB
>> Belden 8237 (RG-8) - 1.7 dB
>> belden 8213 (RG-11) = 1.2dB
>>
>
> Huh? 75 ft of RG-11 has almost 8dB of loss at 146MHz. 75 ft of LMR240 has
> 9.7dB of loss at 146 MHz.
>
> I won't go through your entire list.
>
> Check out http://www.vk1od.net/calc/tl/tllc.php
>
> Cheers,
> John
>
John you need to see where you went wrong. The numbers Jim listed are
either correct or very close. I did not bother to do the calculations, but
looking at a 100 foot chart, the numbers are very close and no where near
the numbers you have.
I thought you may have looked at the web page and missed it defauls to
meters, but that does not seem to be the case to me.
John KD5YI
You are correct, Ralph, and I apologize to the group for my error. I did
indeed put meters rather than feet into the calculator.
Again, my apologies, and thanks, Ralph, for correcting me.
Cheers,
John
'Captain' Kirk DeHaan
It is mounted on an angle bracket about 12" from a mast 20' above my
metal roof. The mast is isolated from roof but is not yet grounded.
>
> Also, the American Legion J-poles are subject to a couple of forms of
> mechanical/electrical failure after a few years. The plastic
> insulator which spaces apart the radiator and matching arm can degrade
> (UV from sunlight is the main offendor, I believe) and crack, allowing
> the two arms to change spacing. More subtly, the connection between
> the two arms and the metal base can degrade... it's aluminum-to-
> aluminum using a set-screw, and the connection can loosen and corrode.
My spacer basically disintegrated. I replaced it with 1/2" pvc pipe. I
measured the spacing at the base and got it as close as possible.
I will check out the other connections. There is obvious aluminum oxide
on the assembly so it is very possible it is down between the parts.
I'll get up on my steep metal roof after the rains stop. :-)
>
> It might be worth checking the spacer (replace if necessary), and
> checking and tuning up the set-screw connections (squirt with Liquid
> Wrench if necessary, loosen and remove, take out the rods, clean the
> ends of the rods and the mounting holes in the place, dab with NoAlOx
> or a similar corrosion-blocker, reassemble and tighten).
>
>> I'm using 75' of
>> professionally assembled RG8X which is required to get from the radio to
>> the antenna.
>
> That's probably costing you about half of your power (assuming a
> typical RG8X-type coax). Some lower-loss types (e.g. LMR-240 are
> better than this.
>
Thanks for the suggestions.
Jim Lux
That's what I used..
Sure you got feet and not meters?
B9219, 75ft, 146 MHz = 1.811dB
John KD5YI
Yes, Jim, Ralph pointed that out to me yesterday and I posted an apology
to him. I see that I should also analogize to you for my mistake.
Thanks to you both.
John
John KD5YI
> Thanks to you both. Apologize
>
> John
Jim Lux
Darn newsreader that didn't have all the messages loaded.. I saw Ralph's
comment and your reply. Such is life..
Now, if you want some high loss coax.. can I interest you in some tiny
coax made of stainless steel? It's for cryogenic applications so it has
very, very low thermal conductivity, but it also has really high loss. I
don't think you want to be running kilowatts (or even watts) through it.
John KD5YI
Well, thanks, Jim, for your kind offer. However I have plenty of lossy
cable now. I only use in the lab because other options are difficult to
handle.
Cheers,
John
tom
According to the loss calculator at Times Microwave the loss at 144 MHz
for a 75 length of LMR 240 is 2.952. 100 METERS is 9.687.
Perhaps you misread.
tom
K0TAR
tom
Oops, needed to do this one level up. Should have responded to John.
tom
K0TAR
Sal M. Onella
> a *very* deep multipath
> cancellation effect playing out... maybe interference between a
> edge-diffraction path involving the office building, and reflections
> from nearby trees.
Not a Sea Story and relevant to my learning an important multipath
lesson:
In 1974, I was on an aircraft carrier at a pier in Long Beach
Shipyard. Ship's TV sigs not so good, so I ran a cable from the CPO
lounge TV out and up to a flight deck catwalk. On the catwalk, I
mounted a small all-channel antenna on a mast strapped to the rail.
The transmitters (Mt. Wilson) were located away from that side. All
very good pictures. In about two months, when the ship moved into
drydock, it was turned 180, so I rotated our TV antenna to
compensate. No good. Signals arriving across the flight deck were
all awful. Unwatchable.
I suspected reflections from the flight deck, so I moved the antenna
all the way aft, where it was receiving through clear air again.
Bingo! Even through the added 150' of cable I needed, we got our nice
pictures back.
"Sal"
JIMMIE
wrote:
> I'm living in a wooded area and am trying to hit our club repeater
> reliably. It's cloudy now so I'm and getting a bit of ducting but I
> have a lot of trees, mostly poplars, in the direct path. I would have a
> line of sight if not for the trees as I'm up enough in altitude. I can
> cut the trees, they're mine, but finding the right ones is difficult and
> i don't want to waste the whole grove.
>
> I go from keying the repeater with no intelligible signal to not being
> able to hit it. Today I actually have an S meter reading due to the
> clouds. I am currently using a J-pole and will put up a Yagi soon but
> wonder if NVIS would work on 2m? I have only seen references to it
> being applied in HF.
>
> 'Captain' Kirk DeHaan
> N6SXR
Im convinced that my J antenna that I used while camping radiated
mostly verticaly. The situation sounds very similar to yours. I
couldnt hit the repeater back home with 50 watts using the J- while
my wife could make contacts on her HT on the same repeater, Her
antenna was either a telescoping .5 wl or 5/8 wl connected directly to
her HT.
Jimmie
Wimpie
I sent you a PM with a result from Radio Mobile.
It took a long time to get RMW working, and getting the terrain data
into the SW.
It is 10 years ago that I used RMW and that computer I don’t have
anymore. I had to start from scratch. First checked with Dutch terrain
data to see whether the results are meaningful.
When you look to the path profile, you have a huge margin (received
power -76 dBm). I used 10W into a 2 dBi antenna (on both sides). I
attached the path profile as generated by RMW (Personal Mail only).
Even reducing your antenna height to 1m AGL gives sufficient margin
(Prx -86 dBm). I used 30m AGL for the repeater antenna. You have 1
degree elevation towards the repeater, that is huge (we don't have
that in the Netherlands).
Assuming the data is correct, it is really strange that you can't hit
the repeater. I couldn’t find were to set vegetation and cities, but
even this shouldn't be a problem. I hope some other people can confirm
the results from RMW.
John KD5YI
Hey, Kirk -
After reading Wim's response, I am more convinced than ever that you
have a problem with your antenna, coax, or transceiver.
What type of coax are you using? Could it have gotten water inside? Are
you using the coax that you used 10 years ago?
Try to think of other question similar to these and we'll get to the
bottom of this.
Cheers,
John
'Captain' Kirk DeHaan
John,
I believe it is either the trees or the antenna. The coax is new and
the transceiver worked fine last time I used it. Also works fine with
this setup getting into the repeater on Schweitzer , 145.230, with 5
watts and the signal report from a gentleman I spoke to was 59. That is
a clear shot and a few miles closer. Although the profiles show there
should be a clear shot to the .780 repeater I can gurantee there is a
wall of trees on the first little ridge on the profile. I found that my
club, which I've only been with for a month, has an SWR meter and an
antenna analyzer. I hope to borrow them to see what's up. In the
meantime I will pull the J-pole down and clean it up as suggested.
There is considerable aluminum oxide on the outside of the parts so
there may be some between the base and uprights. When I put it back up
I will move it 180 degrees from it current location. That will only
move it about 2' but who knows.
Wimpie
wrote:
> John KD5YI said the following on 5/26/2011 8:56 PM:
>
>
>
> > On 5/24/2011 11:05 PM, 'Captain' Kirk DeHaan wrote:
> >> Dave Platt said the following on 5/24/2011 2:54 PM:
> John,
>
> I believe it is either the trees or the antenna. The coax is new and
> the transceiver worked fine last time I used it. Also works fine with
> this setup getting into the repeater on Schweitzer , 145.230, with 5
> watts and the signal report from a gentleman I spoke to was 59. That is
> a clear shot and a few miles closer. Although the profiles show there
> should be a clear shot to the .780 repeater I can gurantee there is a
> wall of trees on the first little ridge on the profile.
Are you pointing to the trees that are about 160m south of you and
below (that are also visible in google earth)?
If so, I can't believe that this will put down your signal from about
-76 dBm towards unreadable (so in the -117 dBm range). Reason: the
first Fresnel zone has a diameter of 36m (118ft) at 160m (525ft) from
your antenna and I don't expect all trees are over (for example) 20m
(60ft) height.
> I found that my
> club, which I've only been with for a month, has an SWR meter and an
> antenna analyzer. I hope to borrow them to see what's up. In the
> meantime I will pull the J-pole down and clean it up as suggested.
> There is considerable aluminum oxide on the outside of the parts so
> there may be some between the base and uprights. When I put it back up
> I will move it 180 degrees from it current location. That will only
> move it about 2' but who knows.
>
> --
> 'Captain' Kirk DeHaan
> N6SXR
>
> "Beam me up Scotty, there's no intelligent life here"
Wim
PA3DJS
www.tetech.nl
Ralph Mowery
"'Captain' Kirk DeHaan" <capt...@ncc-1701a.net> wrote in message
news:pZCdnVd2h-> I believe it is either the trees or the antenna. The coax
> the transceiver worked fine last time I used it. Also works fine with
> this setup getting into the repeater on Schweitzer , 145.230, with 5 watts
> and the signal report from a gentleman I spoke to was 59. That is a clear
> shot and a few miles closer. Although the profiles show there should be a
> clear shot to the .780 repeater I can gurantee there is a wall of trees on
> the first little ridge on the profile. I found that my club, which I've
> only been with for a month, has an SWR meter and an antenna analyzer. I
> hope to borrow them to see what's up. In the meantime I will pull the
> J-pole down and clean it up as suggested. There is considerable aluminum
> oxide on the outside of the parts so there may be some between the base
> and uprights. When I put it back up I will move it 180 degrees from it
> current location. That will only move it about 2' but who knows.
>
I may have missed it, but have you tried riding around with a mobile rig and
seeing if you can hit the repeater ?
A SWR meter may not tell you much about the antenna. I think you are using
rg-8x. The coax will have enough loss at 2 meters to give a very low false
reading. YOu can probably unhook the coax from the antenna and only show
about a 3:1 swr.
tom
The antenna itself could not have radiated a significant percentage
vertically if used near the design frequency. It is effectively a half
wave vertical if properly constructed and fed. Fed being the most critical.
If you didn't choke the coax properly and it was parallel to the ground
you may have radiated some towards the zenith. But I doubt it was most.
tom
K0TAR
Wimpie
wrote:
> John KD5YI said the following on 5/26/2011 8:56 PM:
>
>
>
> > On 5/24/2011 11:05 PM, 'Captain' Kirk DeHaan wrote:
> >> Dave Platt said the following on 5/24/2011 2:54 PM:
Hello Kirk,
Did you receive my PM with the path profile and propagation
prediction from RMW?
I now added clutter because of trees (I used 30m high trees with 80%
density). The predicted signal strength goes down from -76 dBm to -81
dBm (10W transmitters into 2 dBi antennes, your height 10m, repeater
heigth 30m).
Jeff (AE6KS) sent me a .kml file with the path profile from you to the
repeater on the hill, there is good agreement between the data I used
in RMW.
So before going to the paper/plywood production plant, you may search
for some other problem.
'Captain' Kirk DeHaan
> I'm living in a wooded area and am trying to hit our club repeater
> reliably. It's cloudy now so I'm and getting a bit of ducting but I have
> a lot of trees, mostly poplars, in the direct path. I would have a line
> of sight if not for the trees as I'm up enough in altitude. I can cut
> the trees, they're mine, but finding the right ones is difficult and i
> don't want to waste the whole grove.
>
> I go from keying the repeater with no intelligible signal to not being
> able to hit it. Today I actually have an S meter reading due to the
> clouds. I am currently using a J-pole and will put up a Yagi soon but
> wonder if NVIS would work on 2m? I have only seen references to it being
> applied in HF.
>
> 'Captain' Kirk DeHaan
> N6SXR
I am still working on finding where the problem is. I pulled the J-pole
down and checked the resistance of the separate connections. I didn't
want to pull it apart if not necessary. Everything showed 0.0 to 0.1
ohms. Seems fine to me. I then cleaned the connector as throughly as
possible using emory cloth inside and dremeled the outside with a fine
wire brush. There was a small amount of oxidation and it appeared much
cleaner and brighter after. I also straightened the two elements but
they were not really that bent. You had to look down the long axis to
see any deviation. They are as straight as they are going to get but I
can't believe that would make much difference.
After all this I put it back up to it's original height. There was not
discernible change. I was almost unreadable at the repeater.
Next I pushed up my mast a few feet more. It is a 50' pushup that
normally requires guy wires. I am not using any so I am leaving
considerable overlap of the sections. I would estimate it is up around
32'. Even in high winds here I saw little deflection with just the
J-pole. The 3 or 4 feet I pushed it up gave me a little bit of
improvement. When I win the lottery I'll get a 100' tower put up.
Guess I'm stuck with this then :-)
I still think it is the trees and have taken a picture from the roof
peak towards the repeater so you can see what I am dealing with.
http://www.ncc-1701a.net/Ham Radio/ForestObstruction.jpg
It is deceiving as there are many more trees behind this line on my
neighbors property. I wouldn't even think of asking him to cut any.
They are money in the bank for him.
John S
Hi, Kirk -
It looks more formidable than I had imagined. I am sure the picture will
generate some comments.
Nobody can say you aren't making maximum effort, for sure.
When will be that club meeting?
73,
John - KD5YI
John S
Kirk -
Do you have parts on hand such as extra coax, connectors, wire, etc?
Although you have done a thorough job of examining your installation, it
behoove you to make a test separate from your present antenna installation.
For example, you could simply strip 1/4WL from the end of a coax feeder
and put that end on the roof temporarily. I know, not the best match,
common mode currents down the line, signal launches upward, etc. But, it
is simple and might tell you something.
Maybe a quick, thrown-together ground plane?
Just a thought.
73,
John
Sal M. Onella
wrote:
> 'Captain' Kirk DeHaan said the following on 5/22/2011 11:04 AM:
>
> > I'm living in a wooded area and am trying to hit our club repeater
> > reliably. It's cloudy now so I'm and getting a bit of ducting but I have
> > a lot of trees, mostly poplars, in the direct path. I would have a line
> > of sight if not for the trees as I'm up enough in altitude. I can cut
> > the trees, they're mine, but finding the right ones is difficult and i
> > don't want to waste the whole grove.
>
> > I go from keying the repeater with no intelligible signal to not being
> > able to hit it. Today I actually have an S meter reading due to the
> > clouds. I am currently using a J-pole and will put up a Yagi soon but
> > wonder if NVIS would work on 2m? I have only seen references to it being
> > applied in HF.
>
> > 'Captain' Kirk DeHaan
> > N6SXR
>
> I am still working on finding where the problem is. I pulled the J-pole
> down and checked the resistance of the separate connections. I didn't
> want to pull it apart if not necessary. Everything showed 0.0 to 0.1
> ohms. Seems fine to me. I then cleaned the connector as throughly as
> possible using emory cloth inside and dremeled the outside with a fine
> wire brush. There was a small amount of oxidation and it appeared much
> cleaner and brighter after. I also straightened the two elements but
> they were not really that bent. You had to look down the long axis to
> see any deviation. They are as straight as they are going to get but I
> can't believe that would make much difference.
I don't think anybody asked you:
How much power are you putting out?
How well do you hear the repeater; are there times when it fades below
squelch while you're listening to other people?
(No, I don't have a 2m PA that I'm trying to unload.)
Sal
'Captain' Kirk DeHaan
My TM-721A is putting out 35 watts. At least that is the spec. The
repeater is always scratchy and barely readable. I've only had one time
when it even showed up on the S meter. That was low clouds so I assume
it was cloud bounce.
Wimpie
wrote:
> John KD5YI said the following on 5/26/2011 8:56 PM:
>
>
>
> > On 5/24/2011 11:05 PM, 'Captain' Kirk DeHaan wrote:
> >> Dave Platt said the following on 5/24/2011 2:54 PM:
Hello Kirk,
If you have access to both ends of the cable and have access to some
VSWR measurement equipment, you may measure following things (and post
them overhere):
VSWR of cable when terminated with a dummy load
VSWR of cable when open
VSWR of cable when short-circuited
VSWR of cable with J-pole antenna
Now reduce the output power of your transceiver to avoid damage
VSWR when nothing connected to the output of the VSWR meter
VSWR when output of VSWR meter is shorted.
Make sure to check the reference (forward) reading after every change
in load, as this may change due to varying load as seen by the
transceiver. You may also do these measurements with the antenna
analyser (preferably both antenna analyser and VSWR meter).
Regarding the trees, it looks dense. Sadly to mention, if it are the
trees, you have to live with this as tree attenuation at 2m is
relatively low and first fresnel zone is relatively large at > 160m.
You need to remove lots of them to get remarkable improvement and you
mentioned that you couldn't remove lots of them because of financial
reasons.
With kind regards,
Wim
PA3DJS
www.tetech.nl
Don't forget to instruct your racing pigeon to remove abc before
letting him cross the Ocean.
Sal M. Onella
wrote:
> Sal M. Onella said the following on 6/1/2011 10:37 PM:
< snip >
> > How much power are you putting out?
>
> > How well do you hear the repeater; are there times when it fades below
> > squelch while you're listening to other people?
>
>
> My TM-721A is putting out 35 watts. At least that is the spec. The
> repeater is always scratchy and barely readable. I've only had one time
> when it even showed up on the S meter. That was low clouds so I assume
> it was cloud bounce.
>
> --
> 'Captain' Kirk DeHaan
You indicated that you're working other repeaters with ease. Blaming
the trees sounds right.
I think a 2m beam is the way to go. I've used one at Field Day for
ten or so years from south of San Diego and easily worked 100 miles
into Los Angeles, simplex, obviously. The improvement in performance
is dramatic with 15 dBi gain, compared to approx 2 dBi gain of an end-
fed dipole, your j-pole. My two beams were less than 50 dollars
apiece at ham swap meets. Mount with elements vertical.
I just did an experiment and, as I expected, a 10 dB increase in
signal strength took me from unreadable to Q5 copy with tolerable
background hiss. (I used switchable attenuators to set up the signal
test conditions and a distant repeater as the test signal.)
If the repeater is no worse than "barely readable," 10 dB should fix
you up.
By the way, the gain effect is not so great that you'd lose the other
repeaters, unless one just happened to hit a deep null by bad luck.
"Sal"
John S
> This is the repeater I am trying to access, 146.780, K7JEP. I have been
> playing with Google Earth and getting coordinates so I can go over to my
> neighbors property and stand on the ridge between our properties and see
> if I can see the repeater and my house. Hopefully that will help me
> locate the suspect trees.
>
Suspend a heavy object from a rope over level ground. If I have plugged
in the correct numbers, the repeater will be on a line drawn by the
shadow of the rope at 12:55. That is, the repeater will be directly
below the sun at that time.
Maybe you can get an idea of the path to the repeater that way.
73,
John
John S
> On 24 mayo, 05:06, John KD5YI<soph...@invalid.org> wrote:
>> On 5/23/2011 5:10 PM, Wimpie wrote:
>>
>>
>>
>>> On 22 mayo, 20:04, 'Captain' Kirk DeHaan<captk...@ncc-1701a.net>
>>> wrote:
>>>> I'm living in a wooded area and am trying to hit our club repeater
>>>> reliably. It's cloudy now so I'm and getting a bit of ducting but I
>>>> have a lot of trees, mostly poplars, in the direct path. I would have a
>>>> line of sight if not for the trees as I'm up enough in altitude. I can
>>>> cut the trees, they're mine, but finding the right ones is difficult and
>>>> i don't want to waste the whole grove.
>>
>>>> I go from keying the repeater with no intelligible signal to not being
>>>> able to hit it. Today I actually have an S meter reading due to the
>>>> clouds. I am currently using a J-pole and will put up a Yagi soon but
>>>> wonder if NVIS would work on 2m? I have only seen references to it
>>>> being applied in HF.
>>
>>>> 'Captain' Kirk DeHaan
>>>> N6SXR
>>
>>
>>> As you can see from the replies, we are in the speculation phase. If
>>> you would like to receive more specialized feedback, you should
>>> provide us with more details about the path, antenna height, nearby
>>> obstacles, vegetation in between, etc (maybe some pictures).
>>
>>> As we are discussing 2 m wavelength, obstacles that may be optically
>>> in the path may introduce less attenuation then expected, but
>>> obstacles that are outside the optical path can still introduce
>>> attenuation.
>>
>>> At 10m (33ft) from your antenna, the first Fresnel zone is about 9m
>>> (30 ft) wide. In addition, the tree attenuation at these frequencies
>>> is not that high. I think of 0.15 dB/m (I hope somebody can confirm
>>> this). It can be less due to diffraction (bending) of the waves around
>>> and over the trees.
>>
>>> I am almost sure, removing some poplar treetops at 10m from your
>>> antenna or more will not change the situation from marginal to good
>>> (because of the relative low attenuation).
>>
>>> Just to be curious, what type of poplar do you have at your site.>> According to his lat/lon numbers, he is 19 miles from the repeater and
>> its bearing is 185 degrees (ref true north) from him. The repeater is
>> about 2000 feet above him (not including the tower height). He is in a
>> valley that has little altitude variation until his signal reaches the
>> mountain.
>>
>> This info is available from Google Earth using his numbers.
>>
>> All of this leads me to think that something else is wrong. I can hit a
>> repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft
>> tower. My antenna (half wave end-fed dipole) is on a 20 ft mast.
>>
>> signal is always solid with no noise on it (I don't have an S-meter) and
>> I have never had a report of noise on my signal until I tried to carry
>> on a conversation with 200 mw output power.
>>
>> Cheers,
>> John
>
> Hello John,
>
> With Google maps, results (distance and bearing) are similar (based on
> the data given by Kirk).
>
> If the trees south of his antenna are the problem (I am not
> convinced), he needs to cut lots of them. They are about 150m from
> his antenna, and at that distance first Fresnel zone width is about
> 30m (100ft).
>
> It seems flat when looking to the activities in the valley. I hope
> somebody can make a path profile and loss simulation to see what is
> the real obstacle.
>
> With kind regards,
>
>
> Wim
> PA3DJS
Well, I have applied some numbers today and I am changing my mind that
the trees are not the problem.
If my numbers are correct: The repeater, 19 miles away, is 1900 feet
above his elevation. At that distance, the antenna will appear be about
240 feet lower than actual due to earth curvature. That makes the
antenna appear to be about 0.954 degrees above the horizon.
That is equivalent to 60 feet at 3600 feet. In other words, 60 foot
trees closer in will be completely in the way. The hurtful part of this
is that his antenna at 45 feet will have a lowest angle of radiation
(take-off angle) of .7 degrees, right into the near trees. The next lobe
above that is at 2.2 degrees. Between those two lobes is a null.
In short, I think his antenna is in a null. I think the only answer for
his present situation is to raise the antenna another 10 feet.
What do you think?
73,
John
Jeff Liebermann
wrote:
Clever trick, but methinks I have an easier way. I've sighted 1
degree beamwidth microwave dishes this way:
1. Place a road map on a flat surface[1]. If you can't find a road
map, print a Google Maps or equivalent road map on a piece of
paper[2].
2. Pound a nail or push pin into the map at your location.
3. Find a distant mountain, that's also visible. Pound a nail into
the map at its location and sight between the two nails to the distant
mountain.
4. Without moving the map, find the distant repeater location on the
map and pound in a 3rd nail or push pin.
5. Sight from the nail at your location, to the nail at the repeater
location. What you see is where it's located.
[1] Yes, the earth really is flat.
[2] When I didn't have a printed map handy, I've used my laptop LCD
screen and 3ea flat head screws.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
John S
> On Sat, 04 Jun 2011 12:26:33 -0500, John S<sop...@invalid.org>
> wrote:
>
>> On 5/23/2011 5:53 PM, 'Captain' Kirk DeHaan wrote:
>>
>>> This is the repeater I am trying to access, 146.780, K7JEP. I have been
>>> playing with Google Earth and getting coordinates so I can go over to my
>>> neighbors property and stand on the ridge between our properties and see
>>> if I can see the repeater and my house. Hopefully that will help me
>>> locate the suspect trees.
>>>
>>
>> Suspend a heavy object from a rope over level ground. If I have plugged
>> in the correct numbers, the repeater will be on a line drawn by the
>> shadow of the rope at 12:55. That is, the repeater will be directly
>> below the sun at that time.
>>
>> Maybe you can get an idea of the path to the repeater that way.
>>
>> 73,
>> John
>
> Clever trick, but methinks I have an easier way. I've sighted 1
> degree beamwidth microwave dishes this way:
Easier than what I suggested? Actually, all he has to do is step outside
at 12:54 and look at the Sun's location. (I admit it is more accurate to
do this in the winter.)
> 1. Place a road map on a flat surface[1]. If you can't find a road
> map, print a Google Maps or equivalent road map on a piece of
> paper[2].
> 2. Pound a nail or push pin into the map at your location.
> 3. Find a distant mountain, that's also visible. Pound a nail into
> the map at its location and sight between the two nails to the distant
> mountain.
> 4. Without moving the map, find the distant repeater location on the
> map and pound in a 3rd nail or push pin.
> 5. Sight from the nail at your location, to the nail at the repeater
> location. What you see is where it's located.
>
>
> [1] Yes, the earth really is flat.
> [2] When I didn't have a printed map handy, I've used my laptop LCD
> screen and 3ea flat head screws.
I am afraid I cannot tell whether items [1] and [2] are just screwing
with me or that you are sincere.
John
John S
> On 6/4/2011 5:31 PM, Jeff Liebermann wrote:
By the way, Jeff, you have a great deal to offer the group by way of
your vast experience. If I have been disrespectful of that, then I
apologize.
73,
John
Wimpie
Hello John,
This link:
http://www.tetech.nl/divers/Kirk_Repeater_USA_1.png
shows the path profiles with and without trees (from Radio Mobile,
VE2DBE). I will keep it there for some weeks.
I used 30m (98ft) high trees (so they are easy to see).
The trees cover some additional part of the first fresnel zone, but
the average canopy will be lower and the absorption loss is not that
high at 146 MHz.
So yes, there is influence from the trees, but not that much I think.
If you want to get some increase in signal, you need to remove lots of
them, and he don't want to do that. Note that the first trees are
160m away from his antenna (info from google earth, based on data
provided by Kirk).
Jeff Liebermann
wrote:
>Easier than what I suggested? Actually, all he has to do is step outside
>at 12:54 and look at the Sun's location. (I admit it is more accurate to
>do this in the winter.)
Well, your method only works at exactly 12:54PM, requires remembering
daylight savings time, requires dark glasses to avoid blindness, works
badly in fog, need to get it right the first time, and offers no way
to document the results. At 12:54PM, the sun is almost directly over
head with no point of reference, as you would have at the horizon.
Manually translating the sun's overhead direction, to azimuth at the
horizon, requires considerable guesswork. A plumb line might helpful.
Incidentally, trees are a very real problem with antenna sighting:
<http://802.11junk.com/jeffl/pics/DBS/index.html>
That's my view of the DirecTV bird at 101 degrees. The photos were
taken during the bi-annual solar outage, where the sun gets behind the
satellite belt.
<http://en.wikipedia.org/wiki/Solar_outage>
Note the branch shadows on the dish, which are blocking the signal.
>> [1] Yes, the earth really is flat.
>> [2] When I didn't have a printed map handy, I've used my laptop LCD
>> screen and 3ea flat head screws.
>
>I am afraid I cannot tell whether items [1] and [2] are just screwing
>with me or that you are sincere.
As far as this measurement is concerned, the earth is essentially flat
over fairly small areas. No spherical geometry required. Even the
United Nations has adopted the flat earth map for its flag.
<http://upload.wikimedia.org/wikipedia/commons/2/2f/Flag_of_the_United_Nations.svg>
Antarctica is a collection of icicles around the outer edge.
The 2nd item is for real. I was on top of a mountain, trying to aim a
dish without a map. I had Street Atlas USA v5 on my then ancient
Toshiblah 100CS laptop, which I used for my initial bearing. Other
than having a difficult time holding the laptop, problems viewing the
screen in the sunlight, and too short a base line, it worked.
>By the way, Jeff, you have a great deal to offer the group by way of
>your vast experience. If I have been disrespectful of that, then I
>apologize.
Thanks and not a problem. You have a long way to go before such
comments become a problem.
John S
In that case, perhaps it is due to his antenna being at a height that
puts the target into a null. Along with low repeater output power, I
suppose that could cause it.
Thanks, Wim.
73,
John - KD5YI
John S
Okay. I take that back. I just ran a simulation with EZNEC and it shows
twice as much uV available at the receiver than Radio Mobile, so my
conclusion is that a pattern null is not involved. I'm stumped.
73,
John
'Captain' Kirk DeHaan
> reliably. It's cloudy now so I'm and getting a bit of ducting but I have
> a lot of trees, mostly poplars, in the direct path. I would have a line
> of sight if not for the trees as I'm up enough in altitude. I can cut
> the trees, they're mine, but finding the right ones is difficult and i
> don't want to waste the whole grove.
>
> I go from keying the repeater with no intelligible signal to not being
> able to hit it. Today I actually have an S meter reading due to the
> clouds. I am currently using a J-pole and will put up a Yagi soon but
> wonder if NVIS would work on 2m? I have only seen references to it being
> applied in HF.
>
> 'Captain' Kirk DeHaan
> N6SXR
I purchased a 10 element 2m Yagi and installed it today. I can now hit
the repeater in question full quieting. The other benefit is I can hit
the one other repeater that I could not even hear before. I am quite
happy now. :-) Now I don't have to cut down any more trees, other than
those I am selling.
Thanks for all the input from everyone. Problem is solved!
John S
Glad to hear it, Kirk. Good work on your part.
73,
John - KD5YI
Wimpie
wrote:
Hello Kirk,
Thanks for the feedback on the outcome of your experiments, and to
hear that there is no problem anymore.
Wim
PA3DJS
www.tetech.nl