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swr goes up on antenna
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Ralph Mowery
Dec 17, 2014, 7:34:22 PM12/17/14
to
I have a home buit version of the Carolina Windom. An off center fed
antenna about 120 feet long with a 4:1 voltage balun and from the feedpoint
it goes to an inline ferrite bead choke 20 feet from the feed point, then 80
feet of rg-8 to the shack.
The balun is suspose to be rated for 3 kw. It does have 2 cores in it.
By tests, I know if I run ssb at over 800 watts the balun will heat up and
change the swr.
I have noticed lately that running just 100 watts ssb on 80 meters the swr
seems to be going up to about 2:1 and the rig cuts the power back as
expected as I talk from a starting point of 1:1. That has hapened for the
last two mornings. I don't recall it doing that before. The antenna has
been up for several years. It is just over 1:1 when normal on the frequency
I most often operate on. Today in the afternoon when 80 meters was dead I
transmitted a carrier for about 5 minuits and let off to ID, then another
carrier for about 5 minuits and the swr did not change.
Any ideas why the swr went up for the last two mornings, but did not seem to
go up this afternoon ?
---
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antenna about 120 feet long with a 4:1 voltage balun and from the feedpoint
it goes to an inline ferrite bead choke 20 feet from the feed point, then 80
feet of rg-8 to the shack.
The balun is suspose to be rated for 3 kw. It does have 2 cores in it.
By tests, I know if I run ssb at over 800 watts the balun will heat up and
change the swr.
I have noticed lately that running just 100 watts ssb on 80 meters the swr
seems to be going up to about 2:1 and the rig cuts the power back as
expected as I talk from a starting point of 1:1. That has hapened for the
last two mornings. I don't recall it doing that before. The antenna has
been up for several years. It is just over 1:1 when normal on the frequency
I most often operate on. Today in the afternoon when 80 meters was dead I
transmitted a carrier for about 5 minuits and let off to ID, then another
carrier for about 5 minuits and the swr did not change.
Any ideas why the swr went up for the last two mornings, but did not seem to
go up this afternoon ?
---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com
Channel Jumper
Dec 18, 2014, 3:13:00 PM12/18/14
to
I'm not quite sure, but I don't think that it is legal, according to the
Part 97 to transmit a carrier without saying anything.
One other thing - as Columbo would say, the SWR meter does not indicate
resonance, it only tells you what the feed line tells it. By changing
the length of the coax you can make the antenna appear as being resonant
or non resonant, even though the antenna may or may not be a perfect 50
ohm load.
Instead of taking down the antenna and looking at the components, you
chose to visit this forum and ask us to look into our crystal ball for a
solution to your problem.
There is no way for sure for us to know how the PL connectors were
installed, the condition of the coax you used for a feed line, the
condition of the coax you used to build the antenna and the soldered
connectors in between each and every junction.
ONE guess would be that you have a intermittent loose connection and
today it chose to work and tomorrow when it rains, snows, wind blows
etc, it might not make contact and present a high swr as you put it.
Find someone with an antenna analyzer to diagnose your problem for you.
--
Channel Jumper
John S
Dec 18, 2014, 4:13:33 PM12/18/14
to
On 12/18/2014 2:12 PM, Channel Jumper wrote:
> I'm not quite sure, but I don't think that it is legal, according to the
> Part 97 to transmit a carrier without saying anything.
FCC demands that you must issue your call sign within the period
> I'm not quite sure, but I don't think that it is legal, according to the
> Part 97 to transmit a carrier without saying anything.
required after beginning your transmission as he did.
> One other thing - as Columbo would say, the SWR meter does not indicate
> resonance, it only tells you what the feed line tells it. By changing
> the length of the coax you can make the antenna appear as being resonant
> or non resonant, even though the antenna may or may not be a perfect 50
> ohm load.
accepted terminology. Your second sentence is inaccurate and is in
conflict with your first sentence.
> Instead of taking down the antenna and looking at the components, you
> chose to visit this forum and ask us to look into our crystal ball for a
> solution to your problem.
it show your superiority over everyone else here.
> There is no way for sure for us to know how the PL connectors were
> installed, the condition of the coax you used for a feed line, the
> condition of the coax you used to build the antenna and the soldered
> connectors in between each and every junction.
problem handed to you(and the person next to you) on a platter? You
don't really know how to help him, in other words.
> ONE guess would be that you have a intermittent loose connection and
> today it chose to work and tomorrow when it rains, snows, wind blows
> etc, it might not make contact and present a high swr as you put it.
for him? How would you suggest making tests or measurements that you
think could be problems?
> Find someone with an antenna analyzer to diagnose your problem for you.
for weeks with an analyzer in your hands waiting for the first sign of
intermittent connections. Then what? Your measurements have already told
you have a problem. Forget that Channel Jumper non-ham idiot. You are
much more capable than him.
Try some more things and report back. Shake your feeder (you know what I
mean) and have someone watch your meter. Look at each end of both the
feeder and antenna to make sure you have no corrupted insulators or
limbs touching. With a digital ohmmeter, you can measure resistance
across the insulators (power off, of course). The idea is: can I find a
way to measure something using what tools I have to give me a lead to
the problem? Keep looking.
The group would love to help, I'm sure. There are lots of gurus here.
Good Luck!
Dave Platt
Dec 18, 2014, 5:08:08 PM12/18/14
to
In article <Channel.Jum...@radiobanter.com>,
Part 97 does allow you to make brief one-way transmissions, for the
purpose of making adjustments to your station. Evaluating SWR or
adjusting a tuner would fall into this category.
The test transmission itself can be pretty much anything, as long as
it does not violate any other terms of Part 97 (i.e. no foul language,
no music, no interference with other stations on the frequency, and
transmitted in a frequency allowed by your license privileges).
A "blank" CW carrier need not violate any of these. And, in fact,
that's just what many modern radios transmit whenever you hit the "tune"
button to adjust the auto-tuner.
You're still required to identify yourself somehow (verbally or CW)
every ten minutes and at the end of the transmission. So, you do have
to "say something", but you don't have to do it as part of the test
carrier transmission itself... just do it when you're done, or after
ten minutes (whichever comes sooner).
Channel Jumper <Channel.Jum...@radiobanter.com> wrote:
>
>I'm not quite sure, but I don't think that it is legal, according to the
>Part 97 to transmit a carrier without saying anything.
That is an over-generalization.
>
>I'm not quite sure, but I don't think that it is legal, according to the
>Part 97 to transmit a carrier without saying anything.
Part 97 does allow you to make brief one-way transmissions, for the
purpose of making adjustments to your station. Evaluating SWR or
adjusting a tuner would fall into this category.
The test transmission itself can be pretty much anything, as long as
it does not violate any other terms of Part 97 (i.e. no foul language,
no music, no interference with other stations on the frequency, and
transmitted in a frequency allowed by your license privileges).
A "blank" CW carrier need not violate any of these. And, in fact,
that's just what many modern radios transmit whenever you hit the "tune"
button to adjust the auto-tuner.
You're still required to identify yourself somehow (verbally or CW)
every ten minutes and at the end of the transmission. So, you do have
to "say something", but you don't have to do it as part of the test
carrier transmission itself... just do it when you're done, or after
ten minutes (whichever comes sooner).
nm...@wt.net
Dec 18, 2014, 5:46:22 PM12/18/14
to
Maybe moisture freezing, and then melting, or wet moisture that
later dries out. Just a guess though..
If that balun warms up, it's adding a substantial amount of loss.
Not really related to your problem, but I hate to see perfectly useful
RF turn to heat. :|
Also kind of verifies my theory of the cause of the loss I saw when
using one of those antennas at a field day several years ago.
I had compared it to a regular coax fed dipole, and it was way
down from the dipole.
I always blamed the voltage balun it used, and your experience sort of
verifies that assumption.
Ralph Mowery
Dec 18, 2014, 6:05:35 PM12/18/14
to
<nm...@wt.net> wrote in message
news:73dc7f34-4b81-432c...@googlegroups.com...
>> Hard to say really, but sounds sort of moisture related..
> Maybe moisture freezing, and then melting, or wet moisture that
> later dries out. Just a guess though..
> If that balun warms up, it's adding a substantial amount of loss.
> Not really related to your problem, but I hate to see perfectly useful
> RF turn to heat. :|
> Also kind of verifies my theory of the cause of the loss I saw when
> using one of those antennas at a field day several years ago.
> I had compared it to a regular coax fed dipole, and it was way
> down from the dipole.
> I always blamed the voltage balun it used, and your experience sort of
> verifies that assumption.
>
While some of the RF is converted to heat, I also have a 80 meter dipole at
> Maybe moisture freezing, and then melting, or wet moisture that
> later dries out. Just a guess though..
> If that balun warms up, it's adding a substantial amount of loss.
> Not really related to your problem, but I hate to see perfectly useful
> RF turn to heat. :|
> Also kind of verifies my theory of the cause of the loss I saw when
> using one of those antennas at a field day several years ago.
> I had compared it to a regular coax fed dipole, and it was way
> down from the dipole.
> I always blamed the voltage balun it used, and your experience sort of
> verifies that assumption.
>
the same height and at right angles to the OCF antenna. Switching back and
forth between them, the OCF is usually beter. In a few cases the plane 80
mete dipole without a blun will work beter on 80 meters.
Just a few months ago I hung an 18 and 24 MHz dipole about 6 inches bleow
the 80 meter dipole and fed off the same coax. Still the OCF is usually
beter.
The ends of both antennas are about 50 to 60 feet off the ground and not
suported in the middle or at the feed point.
Jeff Liebermann
Dec 18, 2014, 7:17:23 PM12/18/14
to
On Thu, 18 Dec 2014 20:12:53 +0000, Channel Jumper
<Channel.Jum...@radiobanter.com> wrote:
>I'm not quite sure, but I don't think that it is legal, according to the
>Part 97 to transmit a carrier without saying anything.
Wrong.
<Channel.Jum...@radiobanter.com> wrote:
>I'm not quite sure, but I don't think that it is legal, according to the
>Part 97 to transmit a carrier without saying anything.
Part 97.305(a)(b)
(a) Except as specified elsewhere in this part, an amateur
station may transmit a CW emission on any frequency authorized
to the control operator.
(b) A station may transmit a test emission on any frequency
authorized to the control operator for brief periods for
experimental purposes,...
<http://www.hallikainen.org/FCC/FccRules/2013/97/305/index.php>
Actually, you're half right. Much of what I hear on the air is
seriously lacking in content and only a little better than not saying
anything.
--
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
Message has been deleted
nm...@wt.net
Dec 19, 2014, 6:51:07 AM12/19/14
to
On Thursday, December 18, 2014 5:05:35 PM UTC-6, Ralph Mowery wrote:
> While some of the RF is converted to heat, I also have a 80 meter dipole at
> the same height and at right angles to the OCF antenna. Switching back and
> forth between them, the OCF is usually beter. In a few cases the plane 80
> mete dipole without a blun will work beter on 80 meters.
>
> Just a few months ago I hung an 18 and 24 MHz dipole about 6 inches bleow
> the 80 meter dipole and fed off the same coax. Still the OCF is usually
> beter.
>
> The ends of both antennas are about 50 to 60 feet off the ground and not
> suported in the middle or at the feed point.
I was thinking in terms of 80m. I suppose it's possible the windom
> While some of the RF is converted to heat, I also have a 80 meter dipole at
> the same height and at right angles to the OCF antenna. Switching back and
> forth between them, the OCF is usually beter. In a few cases the plane 80
> mete dipole without a blun will work beter on 80 meters.
>
> Just a few months ago I hung an 18 and 24 MHz dipole about 6 inches bleow
> the 80 meter dipole and fed off the same coax. Still the OCF is usually
> beter.
>
> The ends of both antennas are about 50 to 60 feet off the ground and not
> suported in the middle or at the feed point.
could be better on some of the other bands. IE: a 80 dipole is not
going to be too good on 40m unless you use a low loss method of feeding
the high Z antenna.
nm...@wt.net
Dec 19, 2014, 7:01:56 AM12/19/14
to
On Thursday, December 18, 2014 2:13:00 PM UTC-6, Channel Jumper wrote:
> One other thing - as Columbo would say, the SWR meter does not indicate
> resonance, it only tells you what the feed line tells it. By changing
> the length of the coax you can make the antenna appear as being resonant
> or non resonant, even though the antenna may or may not be a perfect 50
> ohm load.
If changing the length of the coax makes large changes in the SWR,
> One other thing - as Columbo would say, the SWR meter does not indicate
> resonance, it only tells you what the feed line tells it. By changing
> the length of the coax you can make the antenna appear as being resonant
> or non resonant, even though the antenna may or may not be a perfect 50
> ohm load.
that just shows you have poor decoupling from the antenna to the
feed line. Need a balun or choke, or a better balun or choke than
what is being used.
What you state is largely a CB radio wives tale, due to most of them
not properly decoupling the antenna from the line.
With proper decoupling, the length of the coax will have little
bearing on the SWR seen at the rig. It will be the same as what is
seen at the antenna input, minus any decrease in SWR due to coax
loss. IE: very high coax loss can make anything look good at the rig.
Jerry Stuckle
Dec 19, 2014, 11:14:39 AM12/19/14
to
On 12/19/2014 2:33 AM, Jeff wrote:
>> By changing
>> the length of the coax you can make the antenna appear as being resonant
>> or non resonant, even though the antenna may or may not be a perfect 50
>> ohm load.
>
> Incorrect, changing the length of the feeder will not change the SWR
>> By changing
>> the length of the coax you can make the antenna appear as being resonant
>> or non resonant, even though the antenna may or may not be a perfect 50
>> ohm load.
>
> beyond any extra loss in the cable. It will change the phase of the
> mismatch that is all; (rotate around a constant VSWR circle on a Smith
> Chart).
>
> Jeff
>
Incorrect. The basic VSWR meter measures the voltage, not the power.
And if the SWR is other than 1:1, this voltage will change depending on
the distance to the mismatch.
Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
But a shorted 1/4 wavelength coax shows an open (infinite impedance).
Somewhere in between (I'm not going to bother to figure out exactly
where because it's not that important) it will show an effective 50 ohm
impedance.
Coax length is unimportant when you have a 1:1 SWR, but if you don't,
the coax will act as a matching network. And length will affect the
overall system.
--
==================
Remove the "x" from my email address
Jerry, AI0K
jstu...@attglobal.net
==================
John S
Dec 19, 2014, 11:33:34 AM12/19/14
to
On 12/19/2014 10:14 AM, Jerry Stuckle wrote:
> On 12/19/2014 2:33 AM, Jeff wrote:
>>> By changing
>>> the length of the coax you can make the antenna appear as being resonant
>>> or non resonant, even though the antenna may or may not be a perfect 50
>>> ohm load.
>>
>> Incorrect, changing the length of the feeder will not change the SWR
>> beyond any extra loss in the cable. It will change the phase of the
>> mismatch that is all; (rotate around a constant VSWR circle on a Smith
>> Chart).
>>
>> Jeff
>>
>
> Incorrect. The basic VSWR meter measures the voltage, not the power.
> And if the SWR is other than 1:1, this voltage will change depending on
> the distance to the mismatch.
>
> Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
> But a shorted 1/4 wavelength coax shows an open (infinite impedance).
> Somewhere in between (I'm not going to bother to figure out exactly
> where because it's not that important) it will show an effective 50 ohm
> impedance.
Please bother. It is important to me to understand these things. And are
> On 12/19/2014 2:33 AM, Jeff wrote:
>>> By changing
>>> the length of the coax you can make the antenna appear as being resonant
>>> or non resonant, even though the antenna may or may not be a perfect 50
>>> ohm load.
>>
>> Incorrect, changing the length of the feeder will not change the SWR
>> beyond any extra loss in the cable. It will change the phase of the
>> mismatch that is all; (rotate around a constant VSWR circle on a Smith
>> Chart).
>>
>> Jeff
>>
>
> Incorrect. The basic VSWR meter measures the voltage, not the power.
> And if the SWR is other than 1:1, this voltage will change depending on
> the distance to the mismatch.
>
> Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
> But a shorted 1/4 wavelength coax shows an open (infinite impedance).
> Somewhere in between (I'm not going to bother to figure out exactly
> where because it's not that important) it will show an effective 50 ohm
> impedance.
you saying that there is a length of transmission line that will satisfy
both the shorted and open conditions. What do you mean by "effective"?
Are the lengths different in the two cases? Please help and thanks.
Wayne
Dec 19, 2014, 12:10:41 PM12/19/14
to
"Jerry Stuckle" wrote in message news:m71isp$m0n$1...@dont-email.me...
On 12/19/2014 2:33 AM, Jeff wrote:
>> By changing
>> the length of the coax you can make the antenna appear as being resonant
>> or non resonant, even though the antenna may or may not be a perfect 50
>> ohm load.
>
> Incorrect, changing the length of the feeder will not change the SWR
> beyond any extra loss in the cable. It will change the phase of the
> mismatch that is all; (rotate around a constant VSWR circle on a Smith
> Chart).
>
> Jeff
>
# And if the SWR is other than 1:1, this voltage will change depending on
# the distance to the mismatch.
But isn't it still Vmax over Vmin, regardless of where that happens on the
feedline?
# Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
# But a shorted 1/4 wavelength coax shows an open (infinite impedance).
# Somewhere in between (I'm not going to bother to figure out exactly
# where because it's not that important) it will show an effective 50 ohm
# impedance.
# Coax length is unimportant when you have a 1:1 SWR, but if you don't,
# the coax will act as a matching network. And length will affect the
# overall system.
I always understood the VSWR to be constant with the feedline length moving
the parameters around the Smith chart constant VSWR circle.
Thus it is possible by changing length to provide an antenna tuner with R
and X values that the tuner can handle better.
Channel Jumper
Dec 19, 2014, 12:13:01 PM12/19/14
to
'Jeff Liebermann[_2_ Wrote:
> ;832323']On Thu, 18 Dec 2014 20:12:53 +0000, Channel Jumper
> Channel.Jum...@radiobanter.com wrote:
> -
> I'm not quite sure, but I don't think that it is legal, according to
> the
> Part 97 to transmit a carrier without saying anything.-
> the
>
> Wrong.
>
> Part 97.305(a)(b)
> (a) Except as specified elsewhere in this part, an amateur
> station may transmit a CW emission on any frequency authorized
> to the control operator.
>
> UH - he wasn't transmitting a CW emission, he was throwing a dead
> Wrong.
>
> Part 97.305(a)(b)
> (a) Except as specified elsewhere in this part, an amateur
> station may transmit a CW emission on any frequency authorized
> to the control operator.
>
> carrier - can you read?
>
> (b) A station may transmit a test emission on any frequency
> authorized to the control operator for brief periods for
> experimental purposes,...
> YES - Brief Periods! 10 minutes is not a brief period!
> (b) A station may transmit a test emission on any frequency
> authorized to the control operator for brief periods for
> experimental purposes,...
>
> http://www.hallikainen.org/FCC/FccRules/2013/97/305/index.php
>
> Actually, you're half right. Much of what I hear on the air is
> seriously lacking in content and only a little better than not saying
> anything.
>
> --
> 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
Sorry Jeff, but you just shot yourself in the foot!
> http://www.hallikainen.org/FCC/FccRules/2013/97/305/index.php
>
> Actually, you're half right. Much of what I hear on the air is
> seriously lacking in content and only a little better than not saying
> anything.
>
> --
> 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
If you transmit a dead carrier and you don't say anything you are in
fact violating the Part 97! All you people did was reaffirm what I had
already said. The sad fact is that we give out licenses like lolly pops
at a barber shop with no real instruction involved and once a person
gets a license they automatically think that they don't need to know the
rules or anything that they learned to pass the exam to get the
license.
Had we had real Elmer's when we gave out those licenses, we wouldn't
have 90% of the garbage we hear today on the HF radio!
As far as amplifiers goes, yes I can see someone using a amplifier on
160 meters in the summertime, but the rest of the time, all they are
doing is broadcasting - not really serving any purpose.
If the OP bought a commercial OCFD in the first place - he wouldn't have
these problems.
The people that made comments about their OCFD out performing a center
cut dipole for X frequency doesn't understand how a OCFD works.
If you have a 80m OCFD and you use it on 10 meters, it acts like a 8
wavelength long 10m dipole. You actually get a realization of GAIN from
the OCFD when you use it on 40 or 20 or 10m...
Unfortunately in my book to realize gain you must give up something in
one direction to improve your signal in another. So the term GAIN
really isn't relevant here. Instead of using the term GAIN I should say
improvement, because improvement would be a more relative term.
--
Channel Jumper
John S
Dec 19, 2014, 1:01:11 PM12/19/14
to
Jeff Liebermann
Dec 19, 2014, 1:06:41 PM12/19/14
to
On Fri, 19 Dec 2014 16:38:58 +0000, Channel Jumper
<Channel.Jum...@radiobanter.com> wrote:
>If you transmit a dead carrier and you don't say anything you are in
>fact violating the Part 97!
As long as you identify yourself at the end of the transmission (and
<Channel.Jum...@radiobanter.com> wrote:
>If you transmit a dead carrier and you don't say anything you are in
>fact violating the Part 97!
every 10 minutes), and not interfering with anyone, methinks it's
legal.
There's no lower limit on the speed of a CW transmission.
Let's do the math for the MINIMUM Morse code speed:
<http://www.w8ji.com/cw_bandwidth_described.htm>
1 / (0.002 WPM * 0.83 baud/wpm) = 602 seconds (10 mins)
So, if I were experimenting with ultra narrow band long range Morse
code or data transmission, that requires that I send very slowly, my
MINIMUM speed would be 0.002 words per minute before one needs to
identify.
Disclaimer: I am not an attorney.
Ralph Mowery
Dec 19, 2014, 1:15:57 PM12/19/14
to
"Channel Jumper" <Channel.Jum...@radiobanter.com> wrote in message
news:Channel.Jum...@radiobanter.com...
>
> Sorry Jeff, but you just shot yourself in the foot!
> If you transmit a dead carrier and you don't say anything you are in
> fact violating the Part 97! All you people did was reaffirm what I had
> already said. The sad fact is that we give out licenses like lolly pops
> at a barber shop with no real instruction involved and once a person
> gets a license they automatically think that they don't need to know the
> rules or anything that they learned to pass the exam to get the
> license.
> Had we had real Elmer's when we gave out those licenses, we wouldn't
> have 90% of the garbage we hear today on the HF radio!
>
> As far as amplifiers goes, yes I can see someone using a amplifier on
> 160 meters in the summertime, but the rest of the time, all they are
> doing is broadcasting - not really serving any purpose.
> If the OP bought a commercial OCFD in the first place - he wouldn't have
> these problems.
>
> The people that made comments about their OCFD out performing a center
> cut dipole for X frequency doesn't understand how a OCFD works.
> If you have a 80m OCFD and you use it on 10 meters, it acts like a 8
> wavelength long 10m dipole. You actually get a realization of GAIN from
> the OCFD when you use it on 40 or 20 or 10m...
>
> Unfortunately in my book to realize gain you must give up something in
> one direction to improve your signal in another. So the term GAIN
> really isn't relevant here. Instead of using the term GAIN I should say
> improvement, because improvement would be a more relative term.
>
>
Yes, I got my ham license out of the same Cracker Jack box that I got my
> Sorry Jeff, but you just shot yourself in the foot!
> If you transmit a dead carrier and you don't say anything you are in
> fact violating the Part 97! All you people did was reaffirm what I had
> already said. The sad fact is that we give out licenses like lolly pops
> at a barber shop with no real instruction involved and once a person
> gets a license they automatically think that they don't need to know the
> rules or anything that they learned to pass the exam to get the
> license.
> Had we had real Elmer's when we gave out those licenses, we wouldn't
> have 90% of the garbage we hear today on the HF radio!
>
> As far as amplifiers goes, yes I can see someone using a amplifier on
> 160 meters in the summertime, but the rest of the time, all they are
> doing is broadcasting - not really serving any purpose.
> If the OP bought a commercial OCFD in the first place - he wouldn't have
> these problems.
>
> The people that made comments about their OCFD out performing a center
> cut dipole for X frequency doesn't understand how a OCFD works.
> If you have a 80m OCFD and you use it on 10 meters, it acts like a 8
> wavelength long 10m dipole. You actually get a realization of GAIN from
> the OCFD when you use it on 40 or 20 or 10m...
>
> Unfortunately in my book to realize gain you must give up something in
> one direction to improve your signal in another. So the term GAIN
> really isn't relevant here. Instead of using the term GAIN I should say
> improvement, because improvement would be a more relative term.
>
>
First Class Phone license out of around 1972.
The OCF I have is home built, but the blaun was bought. It does not take
too much to add about 40 feet of wire to one side and 80 feet to the other
side.
The testing I did was on 80 meters around 2 or 3 in the afteroon. The band
was almost dead, Not a signal within 50 khz of either side of where I was
testing. I did ID and ask if the frequency was in useseveral times during
the test.
Ham radio is partly for testing and experminenting. That is what I was
doing for about the 10 minuits total.
You can look in the books and theory and everything else, but unless you put
up several antennas and compair them in the same area like I have , it is
all just a guess. The ground, trees,and atmosphere are almost impossiable
to modle on a computer for every location. The OCF I was compairing was to
an 80 meter dipole on 80 meters only, not other bands. Without being able
to rotate an anenna, you have to take what you get as far as where the main
lobe of the signal goes.
Most of the ones that complain about amplifiers not being needed are the
ones that don't have one,but wish they did. I seldom run one,but at times
it does make a big differance in making good contacts and not. Same as with
a beam. People with poor antennas say they can work all they can hear,but
they do not realise they are not hearing much either. I don't knock people
with poor antennas. At one time I did not have a very good antenna system
either. Lived on a small lot without any trees and the best I could do was
a dipole up about 20 feet. Still had fun with what I had.
The name is real and the call is KU4PT, unlike some that post on here witout
a real name or showing a call.
Jerry Stuckle
Dec 19, 2014, 9:09:00 PM12/19/14
to
On 12/19/2014 12:10 PM, Wayne wrote:
>
>
> "Jerry Stuckle" wrote in message news:m71isp$m0n$1...@dont-email.me...
>
> On 12/19/2014 2:33 AM, Jeff wrote:
>>> By changing
>>> the length of the coax you can make the antenna appear as being resonant
>>> or non resonant, even though the antenna may or may not be a perfect 50
>>> ohm load.
>>
>> Incorrect, changing the length of the feeder will not change the SWR
>> beyond any extra loss in the cable. It will change the phase of the
>> mismatch that is all; (rotate around a constant VSWR circle on a Smith
>> Chart).
>>
>> Jeff
>>
>
> # Incorrect. The basic VSWR meter measures the voltage, not the power.
> # And if the SWR is other than 1:1, this voltage will change depending on
> # the distance to the mismatch.
>
> But isn't it still Vmax over Vmin, regardless of where that happens on
> the feedline?
>
Yes, but that changes along the coax, depending on the length from the
>
>
> "Jerry Stuckle" wrote in message news:m71isp$m0n$1...@dont-email.me...
>
> On 12/19/2014 2:33 AM, Jeff wrote:
>>> By changing
>>> the length of the coax you can make the antenna appear as being resonant
>>> or non resonant, even though the antenna may or may not be a perfect 50
>>> ohm load.
>>
>> Incorrect, changing the length of the feeder will not change the SWR
>> beyond any extra loss in the cable. It will change the phase of the
>> mismatch that is all; (rotate around a constant VSWR circle on a Smith
>> Chart).
>>
>> Jeff
>>
>
> # Incorrect. The basic VSWR meter measures the voltage, not the power.
> # And if the SWR is other than 1:1, this voltage will change depending on
> # the distance to the mismatch.
>
> But isn't it still Vmax over Vmin, regardless of where that happens on
> the feedline?
>
mismatch.
>
> # Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
> # But a shorted 1/4 wavelength coax shows an open (infinite impedance).
> # Somewhere in between (I'm not going to bother to figure out exactly
> # where because it's not that important) it will show an effective 50 ohm
> # impedance.
>
> # Coax length is unimportant when you have a 1:1 SWR, but if you don't,
> # the coax will act as a matching network. And length will affect the
> # overall system.
>
> I always understood the VSWR to be constant with the feedline length
> moving the parameters around the Smith chart constant VSWR circle.
>
> Thus it is possible by changing length to provide an antenna tuner with
> R and X values that the tuner can handle better.
>
>
A transmission line connected to a load of a different impedance will
act as an impedance transformer. The actual impedance at the source
will be different than that at the load, depending on the load
impedance, the transmission line impedance and the length of the
transmission line. This is why changing the length of the coax allows
the tuner to work better.
Also since impedance is a function for the R and X values, when these
change, the impedance changes.
Yes, changing the length of the coax does move the parameters around the
Smith chart in a circle, but it is not a constant VSWR circle. Plot it
out and you will see the impedance changes, depending on the length of
the coax.
Message has been deleted
John S
Dec 20, 2014, 6:36:39 AM12/20/14
to
On 12/19/2014 10:14 AM, Jerry Stuckle wrote:
> On 12/19/2014 2:33 AM, Jeff wrote:
>>> By changing
>>> the length of the coax you can make the antenna appear as being resonant
>>> or non resonant, even though the antenna may or may not be a perfect 50
>>> ohm load.
>>
>> Incorrect, changing the length of the feeder will not change the SWR
>> beyond any extra loss in the cable. It will change the phase of the
>> mismatch that is all; (rotate around a constant VSWR circle on a Smith
>> Chart).
>>
>> Jeff
>>
>
> Incorrect. The basic VSWR meter measures the voltage, not the power.
> And if the SWR is other than 1:1, this voltage will change depending on
> the distance to the mismatch.
>
> Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
> But a shorted 1/4 wavelength coax shows an open (infinite impedance).
> Somewhere in between (I'm not going to bother to figure out exactly
> where because it's not that important) it will show an effective 50 ohm
> impedance.
With a short, an open, or with what kind of load?
>>> By changing
>>> the length of the coax you can make the antenna appear as being resonant
>>> or non resonant, even though the antenna may or may not be a perfect 50
>>> ohm load.
>>
>> Incorrect, changing the length of the feeder will not change the SWR
>> beyond any extra loss in the cable. It will change the phase of the
>> mismatch that is all; (rotate around a constant VSWR circle on a Smith
>> Chart).
>>
>> Jeff
>>
>
> Incorrect. The basic VSWR meter measures the voltage, not the power.
> And if the SWR is other than 1:1, this voltage will change depending on
> the distance to the mismatch.
>
> Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
> But a shorted 1/4 wavelength coax shows an open (infinite impedance).
> Somewhere in between (I'm not going to bother to figure out exactly
> where because it's not that important) it will show an effective 50 ohm
> impedance.
Message has been deleted
John S
Dec 20, 2014, 11:21:37 AM12/20/14
to
> No, VSWR is not constant along the length of the feedline.
attenuation, the SWR spirals inward. Consider either a very lossy or a
very long line. No matter what is attached at the load end, the source
will see the line characteristic impedance called "surge impedance" of
the line.
The variation that you see when you change the location of your
instrument is due to common mode current on the outside of the shield of
your coax. It will give you a false indication.
> A transmission line connected to a load of a different impedance
> will act as an impedance transformer.
> The actual impedance at the source> will be different than that at
> the load, depending on the load impedance, the transmission line
> impedance and the length of the transmission line.
> This is why changing the length of the coax allows the tuner to work
> better.
> Also since impedance is a function for the R and X values, when
> these change, the impedance changes.
is called complex notation. When the R and X values change the complex
will change, but not necessarily the absolute value which, unfortately
is also called impedance. Consider that |Z| = sqrt(R^2 + X^2) and note
that this is the MAGNITUDE of the vector and carries no information
about phase. What two values can you put under the radical and have the
same |Z|?
So, do you mean the impedance R+jX or |Z|? They are not the same
although one is derived from the other using Pythagorean's theorum.
Please specify.
> Yes, changing the length of the coax does move the parameters around
> the Smith chart in a circle, but it is not a constant VSWR circle.
> Plot it out and you will see the impedance changes, depending on the
> length of the coax.
transmission lines. As mentioned by Jeff, Wayne, and possibly others, it
diminishes as a function of the transmission line length and loss
(commonly called alpha).
If you want to experiment with Smith charts rapidly and easily, then get
the Smith V3.10 from:
<http://www.fritz.dellsperger.net/>
If you learn to use it, it will open a world that you will become
addicted to.
Wayne
Dec 20, 2014, 11:56:13 AM12/20/14
to
"Jerry Stuckle" wrote in message news:m72ln5$p5$1...@dont-email.me...
On 12/19/2014 12:10 PM, Wayne wrote:
>
>
> "Jerry Stuckle" wrote in message news:m71isp$m0n$1...@dont-email.me...
>
> On 12/19/2014 2:33 AM, Jeff wrote:
>>> By changing
>>> the length of the coax you can make the antenna appear as being resonant
>>> or non resonant, even though the antenna may or may not be a perfect 50
>>> ohm load.
>>
>> Incorrect, changing the length of the feeder will not change the SWR
>> beyond any extra loss in the cable. It will change the phase of the
>> mismatch that is all; (rotate around a constant VSWR circle on a Smith
>> Chart).
>>
>> Jeff
>>
>
> # Incorrect. The basic VSWR meter measures the voltage, not the power.
> # And if the SWR is other than 1:1, this voltage will change depending on
> # the distance to the mismatch.
>
> But isn't it still Vmax over Vmin, regardless of where that happens on
> the feedline?
>
# mismatch.
>
> # Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
> # But a shorted 1/4 wavelength coax shows an open (infinite impedance).
> # Somewhere in between (I'm not going to bother to figure out exactly
> # where because it's not that important) it will show an effective 50 ohm
> # impedance.
>
> # Coax length is unimportant when you have a 1:1 SWR, but if you don't,
> # the coax will act as a matching network. And length will affect the
> # overall system.
>
> I always understood the VSWR to be constant with the feedline length
> moving the parameters around the Smith chart constant VSWR circle.
>
> Thus it is possible by changing length to provide an antenna tuner with
> R and X values that the tuner can handle better.
>
>
# A transmission line connected to a load of a different impedance will
# act as an impedance transformer. The actual impedance at the source
# will be different than that at the load, depending on the load
# impedance, the transmission line impedance and the length of the
# transmission line. This is why changing the length of the coax allows
# the tuner to work better.
# Also since impedance is a function for the R and X values, when these
# change, the impedance changes.
# Yes, changing the length of the coax does move the parameters around the
# Smith chart in a circle, but it is not a constant VSWR circle. Plot it
# out and you will see the impedance changes, depending on the length of
# the coax.
Well, I was talking about "lossless" line. Otherwise, the constant VSWR
circle will spiral inward to the center as the line length is increased.
If you use a crappy lossy line of sufficient length, you can make an open
circuit look like 50 ohms.
John S
Dec 20, 2014, 1:56:26 PM12/20/14
to
Wayne
Dec 20, 2014, 2:40:34 PM12/20/14
to
"John S" wrote in message news:m74go2$ibv$1...@dont-email.me...
source.
Many years ago, I was called in to help set up a HF/VHF comm station in a
large building. The VHF transceiver wasn't working and the VSWR measured
1:1.
So, I climbed up to the roof and found the cable was not connected to the
antenna.
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