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Author Topic: Staions hear me, but I can't hear them  (Read 8925 times)
W0FM
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Posts: 2055




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« Reply #15 on: June 13, 2013, 11:00:56 AM »

John, 

You mentioned that you were considering changing to an Alpha-Delta DX-EE antenna.  I have one of those in my attic.  It is a decent antenna and will give you access to three additional HF bands (40, 20 and 15).  But it technically should not make a difference on 10 Meters over your current resonant 10 Meter dipole.  That's because the 10-Meter element on the DX-EE is a resonant 10-Meter dipole.  And a wire dipole, cut to frequency, is a wire dipole cut to frequency.
And, as for the insulation on your dipole wire being the problem?  VERY unlikely. Good luck. 

Keep chunking away.

73,

Terry, WØFM
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KD2CJJ
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Posts: 369




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« Reply #16 on: June 13, 2013, 12:20:48 PM »

It doesnt look like that unit has reactance.  reactance is the imaginary part of impedance.  Impedance (Z) = R +jX    On most antenna analyzers they breaker down Impedance into its components.  Just because you have a 50Ohm impedance and a 1:1 SWR doesnt mean that your antenna is resonant.  Where jX is 0 is the point at which your antenna is resonant.  jX is made up of capacitive reactance and inductive reactance - they will cancel them selves out when the antenna is resonant.  A conjugate match is where R = 50 Ohms and jX = 0 thus your impedance will be 50 Ohms.

Anyway... Im still learning but see if your analyzer has values of X without the tuner.  The tuner compensates for any impedance issues which in theory should fix any resonance issues; in other words there is a slim chance this is your issue since your using a tuner but it would be better to rule out the antenna since its an easy exercise.  Also test it with the tuner in line to make sure the tune is properly happening.  If its a built in tuner unfortunately it wont be possible to test.

I would agree though with the others it could be a receiver issue also... and most likely the issue.



Thanks Mike... I have no knowledge of antenna reactance, so I will have to look into that.  Yes I do have an antenna analyzer (YouKits FG-01 http://www.tentec.com/products/FG%252d01-Antenna-Analyzer.html) so I hope it has reactance on it.  I think it shows the SWR curve and impedance.... not sure if the impedance is the same or can help me find the answer.  So are you saying that I need to get the reactance down to 0 and if so how does one do that (any good reading material that you could point me to?)

My rig is a Kenwood TS-440S.

Thanks,
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73

Mike
KD2CJJ
KD8TZC
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Posts: 67




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« Reply #17 on: June 13, 2013, 01:52:06 PM »

Okay, hooked up my analyzer before the line gets to the tuner... the Z value is > 350 (the highest value the analyzer goes up to), so I think that is part of the issue.  I would think I would want to see a Z of 50 (or close to it).  What are causes of high impedance?

Next test I want to do is hook a dummy load up at the end of the feed line in the attic and see what I get.  And I would also like to just attach a patch cable up in the attic from the antenna directly to the analyzer and see what it reads....  Hmmmm

I hate not knowing what causes these things...

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John - KD8TZC
WB2WIK
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Posts: 20595




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« Reply #18 on: June 13, 2013, 02:11:33 PM »

Could be that there is some corrosion or poor connection in your antenna system that transmit breaks down but receive cannot.

Anything's possible, but that's a real stretch. Wink

I'll bet the RX sensitivity is down on the 440S, this wouldn't be an unusual problem.  Doesn't mean it's "dead," just degraded.
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KD2CJJ
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Posts: 369




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« Reply #19 on: June 13, 2013, 02:12:38 PM »

Yes... it is very high BUT its not outside the abilities of your tuner... But that still wont tell us whether its resonant or not.  Just knowing Z only tells you if you have a good match or not.

Does the analyzer break it down by R and X values?

Okay, hooked up my analyzer before the line gets to the tuner... the Z value is > 350 (the highest value the analyzer goes up to), so I think that is part of the issue.  I would think I would want to see a Z of 50 (or close to it).  What are causes of high impedance?

Next test I want to do is hook a dummy load up at the end of the feed line in the attic and see what I get.  And I would also like to just attach a patch cable up in the attic from the antenna directly to the analyzer and see what it reads....  Hmmmm

I hate not knowing what causes these things...


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73

Mike
KD2CJJ
WB2WIK
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Posts: 20595




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« Reply #20 on: June 13, 2013, 02:26:28 PM »

Okay, hooked up my analyzer before the line gets to the tuner... the Z value is > 350 (the highest value the analyzer goes up to), so I think that is part of the issue.  I would think I would want to see a Z of 50 (or close to it).  What are causes of high impedance?

Next test I want to do is hook a dummy load up at the end of the feed line in the attic and see what I get.  And I would also like to just attach a patch cable up in the attic from the antenna directly to the analyzer and see what it reads....  Hmmmm

I hate not knowing what causes these things...



It's still a mystery why others hear you fine when you don't hear them, though: Wouldn't matter what the antenna SWR is.

For your dipole to be 350 Ohms, something's very wrong.  What's the overall length of the dipole?  Is it fed in the center?  It's hard for a 1/2-wave center-fed dipole to be anything like 350 Ohms, even when influenced by attic materials and other stuff.  Usually somewhere between 25 and 100 Ohms, unless it's cut to entirely the wrong length...
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KH2G
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« Reply #21 on: June 13, 2013, 03:35:25 PM »

Fast test is to rig a wire vertical even in the operating room and see if the polarity is the difference. Go from there.
73
Dick
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KD8TZC
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Posts: 67




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« Reply #22 on: June 13, 2013, 03:46:39 PM »

Fast test is to rig a wire vertical even in the operating room and see if the polarity is the difference. Go from there.
73
Dick
What!?

I'm going to get my dummy load out and the analyzer and start to see if there is a bad segment of the line someplace.  It goes from the basement up to the attic where I have an Ameritron antenna switch.  From there it goes to the balun and antenna.  Something has to be funny somewhere in that mix

I also have a G5RV Jr up there that is not hooked up right now.  I'll hook that up to the switch and see what kind of reading I get with that.
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John - KD8TZC
KD2CJJ
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Posts: 369




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« Reply #23 on: June 13, 2013, 05:19:19 PM »

Not the case...  You can get an impedance match which will show a low or high swr but not be resonant.

I had this issue so I am telling you from experience. People could hear me but I could not hear them.   I went crazy trying to figure this out.. My analyzer told me the whole story...  My reactance was off the chart which led me to tune the antenna into resonance.

Is your noise level higher with the tuner tuned or with out the tuner?  It should be higher with the tuner tuned since you said your z is not near 50ohms. No matter how out of tune the antnenna is a tuner if it has enough capacitance and inductance it should bring the antnenna into resonance and be a near conjugate match.
The tuner should mask any antenna issues if it is working and ultimately should give the antnenna some ears; transmit is a different story since there will be losses on the feedline.

Does the analyzer show the R value of Z?

Too bad your analyzer doesn't show reactance...  Can you borrow one that has reactance (X)?

What brand and model tuner are you using?

Do like you said and check your feed line.  Check your dummy load with a short patch cable into your analyzer. Should read 52ohms or so for Z.  Then attach your dummy load on one side of your feedline and analyzer on the other.  There should be no change.  52 or so ohms.

Next to test losses in the line (since your analyzer doesn't have this.) take your Swr meter and put it right before the dummy load on the antenna side. Use am or cw ....  Note the power... It will be lower than at the operating position due to losses in the feedline but how much.  It should not be more than a few watts loss.  Anything more means issues with the feedline or its crap feedline.

Okay, hooked up my analyzer before the line gets to the tuner... the Z value is > 350 (the highest value the analyzer goes up to), so I think that is part of the issue.  I would think I would want to see a Z of 50 (or close to it).  What are causes of high impedance?

Next test I want to do is hook a dummy load up at the end of the feed line in the attic and see what I get.  And I would also like to just attach a patch cable up in the attic from the antenna directly to the analyzer and see what it reads....  Hmmmm

I hate not knowing what causes these things...



It's still a mystery why others hear you fine when you don't hear them, though: Wouldn't matter what the antenna SWR is.

For your dipole to be 350 Ohms, something's very wrong.  What's the overall length of the dipole?  Is it fed in the center?  It's hard for a 1/2-wave center-fed dipole to be anything like 350 Ohms, even when influenced by attic materials and other stuff.  Usually somewhere between 25 and 100 Ohms, unless it's cut to entirely the wrong length...
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73

Mike
KD2CJJ
KD8TZC
Member

Posts: 67




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« Reply #24 on: June 14, 2013, 05:37:54 AM »

No, my analyzer only has Z (which I thought was found by adding reactance to known impedance of the line... so if I measure my line and I know it is 50 ohms, and lets say the Z reading is 350 ohms, then wouldn't the reactace be 300?)

Okay, so this is what I did last night.  I tested each component that I could.  Line checked out fine from the shack to the attic.  Z was 52 with a 50 Ohm dummy load.  I tested it through the Ameritron sw, and SWR was 1:1 (or darn close) and 28.450 MHz.  I then disconnected the antenna from the feedline and just tested that (with the balun connected) and everything was skyhigh.  I took the unit out of the attic (as it was getting really warm) and disassembled the antenna.  I cut two new lines at 17' 4" total length (or 8' 8" for each leg of the dipole) and then attached them to the balun.  Skyhigh results still.  I then took one of those adapters that allow you to connect PL259 connectors to dipoles that have the two bolts on the side, and hooked the antenna to that (bypassing the balun) and bam... the impedance came down a bit to about 200.  That still seems quite high though so I don't know if this is a balun issue or a wire issue.

As I said in a previous post, I'm just using 14 gauge AWG zip cord.  I like this better than the solid core wire as it is more flexible, but could this be causing the issues with the impedance?  The SWR was a little high( ~4:1) at 28.450, but that was when I was measuring it on the driveway (not up in the air) and I need to tune it up in the attic.

With that said... what is the impedance value telling me on the analyzer?

I'm going to see if I can find another analyzer that I can use... I really wish I wouldn't have bought this YouKits one.  I already had one flake out on me and have to returned for a replacement.  The RigExperts AA-30 was just about the same price and has a lot more features.
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John - KD8TZC
AC2EU
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« Reply #25 on: June 14, 2013, 06:09:27 AM »

I have a G5rv jr I just put up and so far it's working great. I get 10 - 80 meters with my tuner. First 15 minutes of having it up I made several dx contacts on 20 meters.

Imagine what you could do with a "real" antenna!  Grin
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W5DXP
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« Reply #26 on: June 14, 2013, 06:15:34 AM »

... that was when I was measuring it on the driveway (not up in the air) ...

Not a good idea. Tie it to something to get it at least 10' off the ground and in the clear. Testing an antenna laying on the ground can cause symptoms that mask the actual problems.

I suspect that other stations are hearing your common-mode feedline radiation, i.e. that your RF is not reaching the dipole. From your measurements, it sounds like the balun is non-functional on 10m. As a test, I would try it without the balun in the circuit.

Not the problem, but 8'8" per side is a little too long for insulated wire on 28.4 MHz and may be the cause of your 200 ohm reading. 8' per side would probably be better.

Imagine what you could do with a "real" antenna!  Grin

The G5RVjr is a good performer on 40m, 20m, and 10m - but not 15m nor the WARC bands. On 20m, the SWR on the coax is probably around 3:1 or less. At a height of 36', EZNEC sez it has a gain of 8dBi at a TOA of 27 deg rivaling a 1/2WL resonant dipole.
« Last Edit: June 14, 2013, 06:26:00 AM by W5DXP » Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
AC2EU
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Posts: 398


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« Reply #27 on: June 14, 2013, 06:28:57 AM »

Fast test is to rig a wire vertical even in the operating room and see if the polarity is the difference. Go from there.
73
Dick
What!?

I'm going to get my dummy load out and the analyzer and start to see if there is a bad segment of the line someplace.  It goes from the basement up to the attic where I have an Ameritron antenna switch.  From there it goes to the balun and antenna.  Something has to be funny somewhere in that mix

I also have a G5RV Jr up there that is not hooked up right now.  I'll hook that up to the switch and see what kind of reading I get with that.

Did you make your coax cables or buy them? I have helped many hams with antenna problems and the most common is badly soldered pl259 s . In your case, the wind couldn't have damaged the antenna uless there was some connection or surrounding coupling issue. 350 ohms is definitely wrong for a resonant dipole which an out side installation at quarter wave height should be around 73 ohms more or less. Your mileage may vary...

The G5RV is not a resonant dipole. It's impedance is all over the place, depending on what band you are on. Very inefficient.
Your best bet is to fix the resonant dipole. Perhaps the G5rv is interacting with the dipole? If you find no other issues with the coax or antenna, try removing the G5rV. Two antennas in close proximity is not a good thing.  Sad
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W0FM
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Posts: 2055




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« Reply #28 on: June 14, 2013, 07:10:59 AM »

John,

Don't fret over the 14ga ZIP cord.  I have made many antennas over 50 years using lamp cord and, unless you have something poorly soldered, the zip cord should not be an issue.  It can be an issue with regards to longevity when installed outside in extreme weather conditions.  Hopefully, you have none of that in your attic.  ;o)

73,

Terry, WØFM
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W5DXP
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« Reply #29 on: June 14, 2013, 08:20:10 AM »

The G5RV is not a resonant dipole. It's impedance is all over the place, depending on what band you are on. Very inefficient.

Such a statement is partly true and partly myth. An EZNEC simulation of a 51' G5RVjr fed with 17 ft. of VF=0.85, Z0=300 ohm ladder-line yields the following results:

Freq, SWR on coax, Impedance at 1:1 choke
7.16 MHz, 3.3:1, 15 ohms (same as a standard G5RV on 80m)
14.27 MHz, 1.9:1, 27 ohms (same as a standard G5RV on 40m)
28.0 MHz, 2:1, 90+j30 ohms (same as a standard G5RV on 20m)

Why would it be "very inefficient" under the above conditions for which it was designed to be relatively efficient? Exactly where are the losses that make it "very inefficient"? (No fair quoting losses on 30m for which is was NOT designed). Smiley
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
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