Hamstick dipole for 80m
JN
80m (3,5 MHz)
I plan a Hamstick dipole for Digimodes and CW for say 3560 kHz.
What is the best way to lower the resonance frequency
Some type of capasitive loading at the end of base(coil) section
or an inductance at center wich could maybe also function as impedance
transformer?
What is the feedpoint resistance of Hamstick dipole?
Any ideas or experiences?
73 Jouko OH5RM
Cecil Moore
A hamstick has measured 12 dB down from a screwdriver
during 75m mobile CA antenna shootouts. That screwdriver
was about 10 dB down from a 1/2WL dipole. A 75m hamstick
is little better than a dummy load having a radiation
resistance of maybe 0.5 ohm and an efficiency in the
ballpark of 1%, i.e. 100 watts in, 1 watt out.
That said, the best way to accomplish what you are trying
to do is to use extenders on the bottom sections. The
longer the section underneath the coil, the greater the
radiation efficiency. I have extenders in 1, 2, 3, 4, 5,
and 6 foot lengths. They really come in handy for antenna
experiments.
If you could use 6 foot base extenders, that would make
the dipole 8+6+6+8 = ~28 feet long overall. Assuming you
could get that antenna up at a decent height (50+ feet),
I think the performance might be "not bad".
--
73, Cecil http://www.w5dxp.com
John Passaneau
news:47e8e5d4$0$23840$9b53...@news.fv.fi:
Hi Jouko:
I ran a “ham stick” dipole for a while and was able to compare it to a
full size dipole when I put one up. To compare the two antennas, a “ham
stick” dipole at 25’ verses a full size dipole at 35’. On 80/75m the “ham
stick” was down about 20db from the dipole. The 2:1 SWR bandwidth was
about 65KHz for the “ham stick” verses about 200+Khz for the dipole. The
way to get a “ham stick” down the bottom of 80m is to lengthen the whip
that sticks out the top. I can’t remember how much but it was not much.
The Z of a whip of the length of a “ham stick” should be only a few ohms,
but they are close to 50 Ohms when used as a dipole. The difference
between 50 Ohms and the modeled 2 to 3 Ohms is the loss in the coils.
The long, small diameter coils made with small gage wire cause most of
the loss. The “ham stick” dipole is better than no antenna but not by
much on 80m. As you go up in frequency the performance of dipoles made
out mobile antennas improve. On 40m my “ham stick” dipole was 12db down
from a full size dipole and on 20m and above it was less than an S-unit
down. Note that I’m talking about dipoles made out “ham sticks” made for
the respective bands, not using a tuner. Using a turner is a waste of
time as you move farther away from the center frequency the loss goes way
up and your signal goes away! I still use my 80m “ham sticks” but not as
dipole. I have them ground mounted with 4 10’ radials each, spaced 1/16
wavelength apart and feed 90 deg. out of phase. This makes a directional
receive antenna for the DX window on 80m that rivals a beverage antenna.
It makes DXing on 80m fun. The only disadvantage is that unlike a
beverage it only works over about a 65Khz chunk of the band.
John Passaneau, W3JXP
Buck
The ham stick dipole isn't very great for 80 meters. I know from
experience that the hustler mobile antenna works better than the ham
stick on 75 meters. I have used the ham stick on 80 meters mobile
with an antenna tuner. The antenna tuner gave me a much broader
bandwidth as far as SWR is concerned without having to retune.
On the other hand, you are not operating mobile. I don't know how
this compares. I know when I did it, it gave me a very weak, but
readable signal. I had a ground rod in the ground below my window. I
connected the shield side of my coax to the ground stake and the
center to one end of a long spool of wire. I stretched the wire out
about 1/4 wave on the ground and checked the SWR. It was flat on the
frequency I wanted (I got lucky) so I checked into the then GA SSB Net
on 3975. I was weak, but readable and could pass my traffic.
If you can make loading coils, make a couple with large diameters.
The larger the better. Center load each element and make them so you
can tap to the coil. This will work better than the ham stick. You
may find that tapping at two different points works better for you so
you have a bit of an offset in the electrical lengths of the antennas
on either side of the coax. This is because the impedance of a
shortened dipole antenna is lower than 50 ohms. The offset finds a
better match.
Hope this helps.
Buck
N4PGW
--
73 for now
Buck, N4PGW
"Small - broadband - efficient: pick any two."
JN
They are quite in balance with the information I have red from net.
The antenna which I am planning is for portable use and should be
easy to erect and transport.
Your remarks led me to some comments:
- Yes the efficiency on 80m may be too low, because of small size.
- Adding center extenders could help but then 75m hamsticks are out of 80m
band
- By using 40m hamsticks and maybe center loading coil and extenders tuning
to 80m possible?
- Then also operating on 40m without extenders OK
- 80 operation only needed for domestic qsos, no DX
- On 30m and 20m hamstick dipole would work OK
Any comments on these?
73 Jouko OH5RM
Ed_G
>
> If you could use 6 foot base extenders, that would make
> the dipole 8+6+6+8 = ~28 feet long overall. Assuming you
> could get that antenna up at a decent height (50+ feet),
> I think the performance might be "not bad".
Cecil, I would be interested in finding out what you are using for
base extenders..... varying lengths of ? with 3/8"-24 female one end, male
another. You make something, or is something commercially available?
Ed K7AAT
HRBE
I had the same problem, despite assurances from the wholesaler in the USA
where I bought the the two Hamsticks, they were resonant at their lowest at
3750 kHz. I needed to operate them at a lower frequency of no more than 3650
kHz
I tried extending the stainless steel "stinger" but I couldn't find anything
long enough.
Then I tried a disk of aluminium 1.6mm x 75 mm in diameter, fitted between
the stainless whip and the antenna proper, and that reduced the resonanant
frequency to 3575 kHz, adjusting the stinger length was necessary of course.
You may have to make the diameter of the disk slightly larger to get it to
resonate at the lower frequency, just a matter of cut and try.
Using my MFJ Analyser, the feedpoint resistance was close to 50 ohms.
It was a very simple fix!
73
John VK2KCE
"JN" <jn...@vfemail.net> wrote in message
news:47e8e5d4$0$23840$9b53...@news.fv.fi...
Buck
>- Yes the efficiency on 80m may be too low, because of small size.
>- Adding center extenders could help but then 75m hamsticks are out of 80m
>band
>- By using 40m hamsticks and maybe center loading coil and extenders tuning
>to 80m possible?
>- Then also operating on 40m without extenders OK
>- 80 operation only needed for domestic qsos, no DX
>- On 30m and 20m hamstick dipole would work OK
>
>Any comments on these?
>
>73 Jouko OH5RM
>
>
Ok, the antenna is portable. Toss a wire over a couple of tree limbs
and either use full-sized 80 meter dipole, or load it with loading
coils. If you load the antenna with coils located at the end point of
40 meters, you may find yourself with a dual band antenna -- 40/80.
Since you are operating primarily local 80 meter operation, any height
above ground up to about 20 feet will result in NVIS, pretty good
signal there.
You could also try a tree-limb somewhat vertical. Drop a short ground
rod into the ground, tap shield to that and toss other end of 65 foot
wire (plus or minus) over a tree limb. It will operate, but not
perfect. However, it should work as well or better than the
hamsticks.
Just another thot
Buck
JN
Yes I think using capasitive loading at the end of coil parts is the right
way to move the frequency.
What kind of results did you get with the hamstick dipole?
OK 50Ohm feedpoint resistance. I thought it is lower, but maybe it is so
due to high loss resistance in coils.
73 Jouko OH5RM
Cecil Moore
> - Adding center extenders could help but then 75m hamsticks are out of 80m
This is not necessarily true. Since the length of
the top stinger has a much greater effect on resonant
frequency than the length of the bottom section, you
can increase that bottom section length by a large
amount and then adjust the top stinger length by a
smaller amount to achieve the desired resonant
frequency. And you are going down in frequency to
the CW portion of 80m.
For instance, you might extend the bottom portion
by 6 feet and only have to shorten the top stinger
by 2 feet. (When you shorten the stinger, you may
have to hacksaw off a portion to keep the stinger
bottom from residing in the middle of the loading
coil.)
Let's say you have an eight foot long base-loaded
mobile antenna. You decide to move the loading coil
farther up the antenna to the center-loaded position.
If you keep the *same length and same coil*, the resonant
frequency will increase. You have to add more stinger
length to bring it back to the original resonant
frequency (or more coil). Moving the fixed coil farther
away from the feedpoint requires the antenna length to
be increased. That fact works in your favor.
Since the additional bottom section is moving the
fixed loading coil farther away from the feedpoint,
the above effect will occur for your extended
configuration. Experiment with it and see what
happens. You could just use wire for the
experimentation and hang it between two supports.
-----/////-----+-----FP-----+-----/////-----
hamstick wire wire hamstick
Cecil Moore
> Cecil, I would be interested in finding out what you are using for
> base extenders..... varying lengths of ? with 3/8"-24 female one end, male
> another. You make something, or is something commercially available?
Hustler makes various extender sections. I have
2 foot and 5 foot sections from Hustler.
Most of my extender sections are from Henry, the
Texas Bugcatcher guy. They are the "BASE MAST"
sections available in lengths from 1/2 foot to
5 feet and special lengths can be ordered.
http://www.texasbugcatcher.com/
JN
"Cecil Moore" >
> Experiment with it and see what
> happens. You could just use wire for the
> experimentation and hang it between two supports.
>
> -----/////-----+-----FP-----+-----/////-----
> hamstick wire wire hamstick
>
> --
> 73, Cecil http://www.w5dxp.com
I have no hamsticks yet, but maybe I could use some simulation like this:
http://www.k7mem.150m.com/Electronic_Notebook/antennas/shortant.html
73 Jouko OH5RM
Cecil Moore
If you use a fiberglass rod for the coil form similar
to the hamstick fiberglass rod and wind the same number
of turns of the same size wire on it, it should work.
But if you are going to go to that trouble, you might
as well wind high-Q coils.
In fact, if you replace the 75m hamstick coils with
large-diameter high-Q coils, you can probably increase
your radiated power by 1000%, i.e. 10 dB :-).
Ed_G
>
> Most of my extender sections are from Henry, the
> Texas Bugcatcher guy. They are the "BASE MAST"
> sections available in lengths from 1/2 foot to
> 5 feet and special lengths can be ordered.
>
> http://www.texasbugcatcher.com/
Thanks. Looked it up.... nice selection. I'll be looking into this.
Ed
nm...@wt.net
>
> Hustler makes various extender sections. I have
> 2 foot and 5 foot sections from Hustler.
>
> Most of my extender sections are from Henry, the
> Texas Bugcatcher guy. They are the "BASE MAST"
> sections available in lengths from 1/2 foot to
> 5 feet and special lengths can be ordered.
>
I have a hustler 3 footer I use all the time..
Really cranks the performance up when you are
parked and can use a taller whip.
My normal whip is 11 ft, exactly center loaded,
and the mast makes it 14, with the coil at 8 ft.
I wish I had a 5 foot version. Might have to get
one of those for industrial strength use. :/
Of course, if I had another 5 ft mast, I'd end up
coupling them together and having 8 ft. :)
There is no such thing as overkill with a
stationary mobile setup. lol
An 8 ft mast would give me a total height of
19 ft, and the coil would be at 13 ft.
That would brown the food on 75/40 m... :-
JN
I first took total lenght 16 FT (2x hamstick), at 4MHz loading coils near
feedpoint calculated to be abt. 60 mikroH
Then I took total lenght 28 FT (8+6/FP/6+8) coils then moved to almost
center of elements. at 4MHz calculated 56 mikroH
and the same configuration at 3.56 MHz calculated 71MikroH for each coil.
Now 75m hamsicks seem to have abt. 60mikroH coils.
If you use 2x6Ft extenders at center you need 71 mikroH to resonate at
3.56Mhz.
This simulation uses 甸umped coils not helical like in hamstick, but I think
it is possible to use 75m sticks with extenders and still you need to lower
the resonance for 80m CW use.
73 Jouko OH5RM
"JN" <jn...@vfemail.net> wrote in message
news:47ea8e39$0$14990$9b53...@news.fv.fi...
Cecil Moore
> Now 75m hamsicks seem to have abt. 60mikroH coils.
> If you use 2x6Ft extenders at center you need 71 mikroH to resonate at
> 3.56Mhz.
Which gives you incentive to replace the hamstick
coils with relatively high-Q coils and thus increase
your radiation efficiency by magnitudes.
Michael Coslo
How do you adjust the coil at that height? Of course I find that I
choose and spend most of my time on one band per mobile session, so
maybe it isn't a big problem.
- 73 de Mike N3LI -
nm...@wt.net
>
> How do you adjust the coil at that height? Of course I find that I
> choose and spend most of my time on one band per mobile session, so
> maybe it isn't a big problem.
>
> - 73 de Mike N3LI -
Well, I only have a few taps on the coil, so I don't have to change
all that often. I might have three taps for 80m, a couple for 40m,
one each for the rest of the bands..
I'll tune the antenna in the normal 11 ft mode, using the usual
tap for the freq I'm using, and then I add the 3 ft mast.
I'll stay on the same coil tap, but shorten the stinger a couple
of inches or so.
I'm on 80 or 40 most all the time, so I don't have to change
but maybe twice a day.. 40 all day, and then I'll switch to
75 at night when it gets dark.
Cecil Moore
> ... I'll switch to 75 at night when it gets dark.
What do you switch to at night when it doesn't
get dark? :-)
Michael Coslo
> nm...@wt.net wrote:
>> ... I'll switch to 75 at night when it gets dark.
>
> What do you switch to at night when it doesn't
> get dark? :-)
Dammit Cecil - not when I'm drinking coffee! hehehe 8^)
nm...@wt.net
HRBE
I made up a 4 band "spider" mount, to which you can screw in 4 sets of
hamsticks. I have a full set of hamstick whips from 80m down to 6m.
So I have a multiband hamstick dipole array!
When one thinks about the feedpoint impedance, even without the capacitive
disk, it certainly should be lower, but as I am using them at 7 metres from
groundlevel in a portable situation, I use a small antenna tuner.
At that height, they act like a "cloud warmer" or a NVIS antenna, so at 80m
its good for up to 350km. I haven't really given the other frequencies a try
yet.
Let me know I can email you with a few pics of my multiband "spider mount",
as I have a small lathe and milling machine in my workshop, it wasn't hard
to make.
73
de VK2KCE John
"JN" <jn...@vfemail.net> wrote in message
news:47ea1536$0$14987$9b53...@news.fv.fi...
Bryan
> nm5k wrote:
The Hustler MO-1 and MO-2 masts have a hinge at 15" and 27" above the bottom
end: http://www.new-tronics.com/main/html/mobile__hf.html
They're 54" tall. The MO-3 is also 54" tall but doesn't have the hinge.
The MO-4 is 22" tall (no hinge).
73,
Bryan WA7PRC
Jon Kåre Hellan
> nm...@wt.net wrote:
>> ... I'll switch to 75 at night when it gets dark.
>
> What do you switch to at night when it doesn't
> get dark? :-)
Why the smiley?
"When I told you to turn off the light at 10:30PM, you were also
supposed to stop reading, dear"
Greetings from 63N. We don't get midnight sun, but we can read a
newspaper all night long.
73
LA4RT Jon
Cecil Moore
> "When I told you to turn off the light at 10:30PM, you were also
> supposed to stop reading, dear"
:-) Do y'all call that night or day?
Jon Kåre Hellan
> Jon Kåre Hellan wrote:
>> "When I told you to turn off the light at 10:30PM, you were also
>> supposed to stop reading, dear"
>
> :-) Do y'all call that night or day?
We'd probably stretch "evening" until midnight. After that it's
"night", no matter how light.
Actually, we don't speak English at all, of course. :-)
Cecil Moore
> Actually, we don't speak English at all, of course. :-)
Us Texans don't palaver English neither.
Fred McKenzie
"HRBE" <hr...@bigpond.net.au> wrote:
> I made up a 4 band "spider" mount, to which you can screw in 4 sets of
> hamsticks. I have a full set of hamstick whips from 80m down to 6m.
>
> So I have a multiband hamstick dipole array!
HRBE-
I think it was the December, 2007, issue of QST that had an article on
the "Octopus" antenna made of 4 pairs of mobile whips for 75/40/20/15
meters. I plan to also add a vertical 10 Meter whip.
I've collected the parts but haven't assembled it yet. It will be
interesting to see how the monstrosity works!
Fred
K4DII
Cecil Moore
> I've collected the parts but haven't assembled it yet. It will be
> interesting to see how the monstrosity works!
Hope you enjoy 75m QRP.
Fred McKenzie
Cecil Moore <nos...@w5dxp.com> wrote:
> Fred McKenzie wrote:
> > I've collected the parts but haven't assembled it yet. It will be
> > interesting to see how the monstrosity works!
>
> Hope you enjoy 75m QRP.
Cecil-
I can appreciate that a mobile whip used on an auto, does not have the
efficiency of a full quarter wave vertical over an array of counterpoise
wires. But it does work.
I want to use a pair of mobile whips as a horizontal dipole. (Or more
in the case of the Octopus.) Are you suggesting that such a dipole on
75 or 40 Meters, will not perform as well as just one of the whips
mounted on an automobile?
Fred
K4DII
Cecil Moore
> I want to use a pair of mobile whips as a horizontal dipole. (Or more
> in the case of the Octopus.) Are you suggesting that such a dipole on
> 75 or 40 Meters, will not perform as well as just one of the whips
> mounted on an automobile?
The radiation resistance of a 75m hamstick is roughly
about 0.5 ohms. The feedpoint impedance is roughly
about 20 ohms if one subtracts out the ground losses.
Very roughly, that would make a 75m hamstick dipole
have a radiation resistance of about 1 ohm and a
feedpoint impedance around 40 ohms. That's about 2.5
watts out for 100 watts in. I would say that qualifies
for QRP and is actually an improvement over a 75m mobile
hamstick with a measured signal strength that is 12 dB
down from a good screwdriver which itself is about 10 dB
down from a 1/2WL dipole.
Almost any other antenna in the world will beat a
75m hamstick dipole. One can radiate ten times as
much power simply by lengthening it by 50% and using
high-Q loading coils.
John Passaneau
@nlpi070.nbdc.sbc.com:
Hi:
As I reported some time ago, I compared Hamstick dipoles to a full size
dipole at about the same height. The Hamstick dipole was about 20d down
from the full size antenna. The 2:1 SWR bandwidth was about 65KHz. They
work as an antenna but are in the better than nothing class.
John Passaneau W3JXP
Cecil Moore
> As I reported some time ago, I compared Hamstick dipoles to a full size
> dipole at about the same height. The Hamstick dipole was about 20d down
> from the full size antenna.
So I was generous in estimating 2.5 watts radiated
out of 100w input. In your case, it was more like
1 watt radiated out of 100w input.