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Author Topic: Staions hear me, but I can't hear them  (Read 8280 times)
KD8TZC
Member

Posts: 67




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« Reply #30 on: June 14, 2013, 08:34:39 AM »

Okay, let's forget about the G5RV... I'm not using it and only have it and so mentioned it.  Also, I removed it from the attic yesterday as we will be using it on field day.

Yes, I made the transmission lines.  I tested all of them with the analyzer and a dummy load and they all have very low SWR (close to 1:1) and all approx 50 ohms resistance... so with all that, I would think the connections are okay.  If I made a bad presumption, please say so as I am trying to learn, and also tell me how I should properly test them (please not that the main transmission line goes from the basement up two floors and into the attic via a PVC pipe that was installed in the house for this purpose.  I can't use a multitester to test anything now that it is installed - since it spans from the basement to attic, OR is there a way to do that given how it is installed?).

I still don't understand what the cause of the high impedance though when just adding the antenna.  Too me, it seems the only thing that could be causing this is the wire (correct me if I'm wrong).  I can reduce the length of each leg of the antenna by folding them back, but according to my analyzer, it was crappy across the entire spectrum, so I don't know if reducing will do much... I'll try it though.

Yes, I know doing this on the ground is not ideal... I didn't have a way to suspend anything last night and was sort of in a rush.  I'll see if I can support it this weekend when I am working on it to see what I can get.

Thanks all...
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John - KD8TZC
WB6BYU
Member

Posts: 13045




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« Reply #31 on: June 14, 2013, 08:49:45 AM »

Quote from: KD8TZC

I still don't understand what the cause of the high impedance though when just adding the antenna.  Too me, it seems the only thing that could be causing this is the wire (correct me if I'm wrong).  I can reduce the length of each leg of the antenna by folding them back, but according to my analyzer, it was crappy across the entire spectrum, so I don't know if reducing will do much...



So as I understand it, you tested the coax by putting a dummy load on the far end and
it was OK.  When you added the wires the SWR was very high.  When you used a
commercial dipole center insulator to connect the wires it was lower.

What sort of balun are you using at the feedpoint?  It should be a 1 : 1 rather than
a 4 : 1.

If not, how are you connecting the wires?

There's nothing wrong with using zip cord for the antenna.  (I've even used it as feedline.)
But from your description so far it sounds as though the problem is where the wires
connect to the feedline.  What happens if you use the commercial dipole center insulator
in the attic?

Oh, and the best use of the antenna analyzer i this case is to check the SWR across a
wide frequency range to see where the minimum point is - that tells you how to adjust
your antenna.  The resistance/reactance readings will vary with the length of the feedline
and can lead you astray if you aren't careful.
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KD8TZC
Member

Posts: 67




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« Reply #32 on: June 14, 2013, 09:08:50 AM »

As stated before, I was using a 1:1 balun up in the attic.

Yes, I did try  a commercial center insulator.  It was from my G5RV antenna (see the following link and you will see the white center insulator at the end of the ladder line.  I disconnected this from the G5RV and connected it to my home brew dipolehttp://www.aesham.com/images/products/raog5rv_junior.jpg).  Again, it did bring the Impedance down a bit, but it was still quite high.  Is that okay, or do I want to be as close to 50 ohms as possible to make it resonant?
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John - KD8TZC
WX7G
Member

Posts: 5922




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« Reply #33 on: June 14, 2013, 09:20:14 AM »

Antenna issue:

At the dipole resonant frequency your antenna analyzer will indicate the lowest impedance. I suspect the resonant frequency is well below the 10 meter band. Find out where the lowest impedance is and if it is below the 10 meter band start trimming the antenna length.

I do think your receiver is the cause of the 10 meter RX/TX discrepancy and not the antenna. One way to check this is to substitute another receiver.
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KD8TZC
Member

Posts: 67




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« Reply #34 on: June 14, 2013, 09:29:23 AM »

I do think your receiver is the cause of the 10 meter RX/TX discrepancy and not the antenna. One way to check this is to substitute another receiver.

I really like this idea, but I don't have the $$ in the bank to do it... Sad

The thing that stinks is I can't test the rig until next Wed when we have our 10M net... and there is nothing on 10M it seems (except some PSK and CW from time to time).
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John - KD8TZC
WB6BYU
Member

Posts: 13045




Ignore
« Reply #35 on: June 14, 2013, 09:43:31 AM »

Can you make a schedule with a local ham to test it out?

Or even take it over to the other ham's house and compare the radios side-by-side
on the same antenna.  There is a lot of help that is best provided in person rather
than over the internet, as some faults (such as the RIT or VF0 A/B controls set
wrong) that might be obvious to an experienced ham but that we can't see at this
distance.
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AE5QB
Member

Posts: 269




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« Reply #36 on: June 14, 2013, 10:34:44 AM »

Interesting thread. 

IMO there is something very basic wrong here.  I doubt if it is a receiver problem or an antenna problem.  I think it is an issue with the way the radio is set up or something simple with the antenna.  I like the previous suggestion of getting some help.  I have worked in electronics for 50 years and troubleshooting problems is a whole lot easier when you have a shelf full of spare parts to swap in and out to eliminate.  It seems you have some friends on the net who could help tremendously.  Have them come to you or as has been suggested, take your rig to their shack and try out a known good antenna system.  Don't worry about time and don't get frustrated.  If next Wednesday is the best you can do, then so be it.  But I am willing to bet there is someone reasonably close to you who would be willing to help out this weekend.

If you can't find someone to help you out, my suggestion at this point it to go minimalist.  Re-read your rig's manual.  Do a factory reset on it or read through the manual very thoroughly and manually reset everything back to the starting positions.  The previous post is a very real possibility.  We have all inadvertently had a feature turned on that shouldn't be or one turned of that should be on.     

Take your rig to the park along with a short piece of coax and a wire dipole.  A 10 meter dipole is not very long so it should be easy to either pull it out of your attic or make a new one from some scrap wire.   Trying to work from the basement to the attic can be very frustrating.  Hang the dipole in a tree and test it with the antenna analyzer.  Trim for resonance wherever you want it to be.  Now connect the radio and see what the SWR is.  It should be the same as indicated on the antenna analyzer.  Go from there.

I have learned in 50 years of electronics from TV's to U.S. Navy radars and missile fire control systems to check the obvious first and then go from most likely to least likely.  A radio failure is possible, but it would be low on my list of probable causes at this point.  You learn these things from trial by fire so hopefully some our experiences can shorten the learning curve for you.  IMO you have something very basic amiss here and some simple troubleshooting will help figure out what it is.

If nothing else, take some pictures of the front and back of your rig, every connection point between the radio and the antenna, and pictures of the antenna with some references that we can use to determine lengths, and I bet we can figure this out.  After all, this ain't rocket science...oh wait a minute, yes it is.

Never give up!

Tom/AE5QB
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WB6BYU
Member

Posts: 13045




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« Reply #37 on: June 14, 2013, 10:47:03 AM »

Quote from: WX7G

At the dipole resonant frequency your antenna analyzer will indicate the lowest impedance.



Not necessarily if he is measuring at the shack end of the coax.

It is easy to construct an example:  Say that the antenna is resonant at 28.5 MHz, where
the impedance is 50 ohms and the SWR is 1 : 1.  Then the SWR rises to 5 : 1 at 27 MHz,
where the length of the coax is such that the impedance is 10 ohms at the shack end.
The lowest impedance (10 ohms) would be at 27 MHz even though the antenna is resonant
at 28.5 MHz.
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KD2CJJ
Member

Posts: 369




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« Reply #38 on: June 14, 2013, 11:05:35 AM »

I agree with some of the good advice.  My observation and suggestions:

1.  Where is your lowest impedance (Z)?  If your lowest impedance is not near 50 Ohms AND its not within the band you want then you have a major issue with the antenna system.  If your lowest impedance reading is near 50 Ohms and NOT within the band lengthening or shorting the antenna by small amounts can  move that point into the band.  As an example if your lowest impedance is at 13.900Mhz and you want it to be 14.250Mhz then you will need to shorten the ends... if its above 15Mhz and you want to lower it then lengthen the ends... You can use the fold back method but its not exact when you cut them...  Dont cut about 5% until you retest if you want to use the fold back method and then cut... its not exact.

If your LOWEST impedance is 350 Ohms (which based on reading the manual of your analyzer Z IS the lowest Impedance) and is outside your band then that is a problem - for sure your antenna is no where near resonance NOR is it a match - in other words its like having the feedline with nothing attached to it (not even a dummy load).

2.  I agree with another point that its your common mode current that is radiating.  Thank you for articulating what I did not in my original threads.  Even though your tuner can give you a near perfect match, if the antenna is so far out of resonance its the common mode that is radiating and why people can hear you but you cant hear them - Essentially its radiating from the feed-line.  

With all this, I am still concerned that your tuner would not mask the issue - Good tuners can tune a light bulb and have a somewhat effective receive and transmit.  If that is the case then we can for sure there is something wrong with your antenna but we almost have to question your tuner.  What are the odds that your tuner is not tuning the antenna properly?  There have been cases that older LDG tuners would tune the antenna with a proper SWR but the antenna was no where near resonance thus you didnt hear anything.

Here are your options:

1.  Borrow any other antenna that when using your analyzer shows a proper impedance match - rule out antenna system
2.  Borrow another receiver and use a A/B switch to compare - rule out radio

Presumed Facts based on discussion:
Your antenna is not resonant - Open Question is where your lowest Impedance? Is it within or near the band.
Your feed line system is OK.
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73

Mike
KD2CJJ
AC2EU
Member

Posts: 343


WWW

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« Reply #39 on: June 14, 2013, 11:28:52 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

Oh man! we can really go down a long and bumpy road on this one!
Just for starters:
EZNEC is OK, but we both know that real world results differ.
I have tested some full sized G5RV installations with an analyzer and I felt that they were way overrated. In fact, dismal.
That's not to say that you won't make contacts with it. Lots of guys who have good antennas but use QRP power manage to contact most of the world. 100 watts into a G5RV on most bands will probably radiate in QRP class, the rest is circulating in the tuner.
Also, most tuners are more efficient tuning into a higher than nominal impedance than lower.

Don't take my word for it, here's another ham who did measurements:
http://www.karinya.net/g3txq/g5rv/

I have resonant dipoles on 160, 80,40, and 20. You can see and hear the signal strength change as I switch though them to the correct one for the band. Several S units difference on weak signals plus no tuner needed unless I'm at the extreme ends of the band on 80.  I tune the harmonics for the remaining bands.

Hey, but to each his own!  Grin

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AC2EU
Member

Posts: 343


WWW

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« Reply #40 on: June 14, 2013, 11:49:27 AM »

Okay, let's forget about the G5RV... I'm not using it and only have it and so mentioned it.  Also, I removed it from the attic yesterday as we will be using it on field day.

Yes, I made the transmission lines.  I tested all of them with the analyzer and a dummy load and they all have very low SWR (close to 1:1) and all approx 50 ohms resistance... so with all that, I would think the connections are okay.  If I made a bad presumption, please say so as I am trying to learn, and also tell me how I should properly test them (please not that the main transmission line goes from the basement up two floors and into the attic via a PVC pipe that was installed in the house for this purpose.  I can't use a multitester to test anything now that it is installed - since it spans from the basement to attic, OR is there a way to do that given how it is installed?).

I still don't understand what the cause of the high impedance though when just adding the antenna.  Too me, it seems the only thing that could be causing this is the wire (correct me if I'm wrong).  I can reduce the length of each leg of the antenna by folding them back, but according to my analyzer, it was crappy across the entire spectrum, so I don't know if reducing will do much... I'll try it though.

Yes, I know doing this on the ground is not ideal... I didn't have a way to suspend anything last night and was sort of in a rush.  I'll see if I can support it this weekend when I am working on it to see what I can get.

Thanks all...

OK, two more questions:
How long is the dipole end to end? it should in the realm of 468/f (in MHZ) feet.
What type coax and how long? Is that all there is between the shack and balun? No ladder line, etc?

Also sometimes the commercial baluns fail (it  happened to me, intermittent due to cold solder joint interanally). Try coax direct to the antenna.
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W0FM
Member

Posts: 2054




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« Reply #41 on: June 14, 2013, 11:52:23 AM »

I still can't get my head around why you feel you need a tuner for a 10M resonant dipole.  If it is that far off, then prune it (or extend it) for resonance.  No tuner necessary.  I have found that folding excess insulated wire back on itself to adjust the length of a dipole for resonance is not a good approach.  If you have 8', 8" of wire per side (I believe that's what you said), then run the end of the wire through the hole in the end insulator, wrap once around the element wire and let the last 10-12 inches dangle down.  Then it is a simple matter to trim a half inch or so at a time from each end.  No unwrapping and rewrapping.  A 1:1 balun is certainly a good idea.  Don't lose that.

That said, your antenna would need to be WAY out of resonance to experience what you are describing.  Almost any old hank of wire will receive on 10M.  Something else is wrong here.



Terry, WØFM
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WH7DX
Member

Posts: 1029




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« Reply #42 on: June 14, 2013, 12:22:03 PM »

I agree with Tom,

Take the rig to the park.  Test it outside your current environment.   Put a temporary antenna outside for a few hours to test.. whatever it takes.   If you have an upstairs room.. put the Center Connector on a broom stick and pull the lines to the side outside the house etc.. 

I laid a 10M dipole on my wood deck when I first started - to see what I could hear, draped it over the sides and it picked up signals well enough 6000+ miles to SA.

If it were me, I'd get a new wire for 10M and center connector.   I'd check the coax with a Voltage/Ohm meter.   Check for resistance in the coax and a short just to rule it out.   You shouldn't have any resistance for short coax. 

Make the wire 9 ft long on each side.   You can fold it back onto itself to tune it if you want (tape it) or just make it 16.5 feet total length.

Give that a try.   Often times, because of a hill right behind me, my signal gets out better than I can receive.   I can be quite strong into Europe but barely hear them.. like 22.

Run through the manual again.   

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KD8TZC
Member

Posts: 67




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« Reply #43 on: June 14, 2013, 02:04:46 PM »

Actually, there might be something else that is the problem... the analyzer.  If when I connect this to any antenna that I have it reads high, all I know is that all my antenna's suck.  Maybe I should take this to someone who has a known good antenna, and better yet an analyzer of their own, and compare.  I have a feeling that this YouKits analyzer may be goofy.  I had to return the first one I had, and this one I notice will "creep up" with the reading if I leave it on for more than a minute or so.  In fact, I have attached it seen an OK SWR curve, turned it off, and then back on again a few minutes later without doing much of anything and will get a totally different curve.  I'm not sure if that is an issue with the unit or maybe I am sitting on a electromagnetic anomaly.

Anyhow, I was thinking of doing the park thing, but that won't tell me anything if I can't get a good reading with the analyzer.
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John - KD8TZC
W5DXP
Member

Posts: 3546


WWW

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« Reply #44 on: June 14, 2013, 04:32:05 PM »

100 watts into a G5RV on most bands will probably radiate in QRP class, ...

Please choose one of the four bands (80m, 40m, 20m, and 12m) where the G5RV is known to work well and show us the math it takes to achieve 13 dB of losses. Such results would be unique in my 60 years as a ham.

Quote
Don't take my word for it, here's another ham who did measurements:
http://www.karinya.net/g3txq/g5rv/

Maybe you should send Steve an email asking him what he thinks about your above posting.
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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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