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35, you promised to test the A99, but the weather was bad.

It's actually been really nice here today, perfect antenna testing weather, however I'm finishing the interior decorating today as my relatives from CA are arriving tomorrow morning, so that will be another couple of weeks without radio, maybe I can rope my cousin into testing the antenna with me, in fact if I get him to suggest it to my wife I'll get the green light, she can go shopping with his wife and daughters, or whatever women do :D

Currently using my phone to grab a peak of the web whilst holding a paint brush in the other hand, must dash :whistle:

When I get a chance later I'll have a look at your reply in detail ;)
 
remember the a99's so239 connector is not the antenna's feed-point when you are cutting 1/2wave lines for testing the 1/2wave repeater idea
 
remember the a99's so239 connector is not the antenna's feed-point when you are cutting 1/2wave lines for testing the 1/2wave repeater idea

I know you have stated this idea before Bob, and I didn't even think about it when I tested, I just used the line because it was convenient. I was hoping that 35, would do the 1/2 wave test like he said he would.

My match was off as you can see. I wasn't actually testing for the 1/2 wave idea perse. I did figure it would be close however. I just posted what the VA1 showed at the three frequencies around CB. I was hoping, if possible, to show 35 that his earlier situation at the match might have been a fluke, and the A99 at the feed point did not typically produce an irregular curve...as his test had noted when testing with and without a feed line. I did duplicate his previous test using and antenna without a mast however, but I wasn't up to doing a lot work either.

I agree that the physical feed point is further up inside the antenna. The other end where the RG8x is attached to the coil is the feed point I think. I measured that coax at 11." Does that sound about right, so should I shorten the jumper 11" inches or double the length to 22" inches...to get back down to the VA1 so to speak?

This idea may be the gospel truth, but I've never tested the idea. Have you tested it, or is it just your observation as to what looks to be going on there? If you tested, did your test indicate a notable difference that you could easily detect with this amount of error...if you didn't account for the extra coax?

This afternoon, I wasn't feeling bad yet, and it cooled off a little. So, I put the A99 on a mast, attached using a 24" piece of Delrin to isolate it from the mast. I checked the match directly at the SO239 as best I could for resonance, and with the antenna base about 6' feet above the Earth. It seemed to resonate best at about 27.500, where the rings were set. I screwed the rings down closer to the middle, or maybe a bit lower, until I saw the best SWR and value for Z=50 at 27.205. The value of X=-20 was also indicated, so I still had a complex impedance, even though the value of Z=50, reactance was off a bit. Maybe that is as good as it will get...being that close to the ground, and with the analyzer not being directly at the real feed point as you suggest. Maybe this is also why this antenna generally looks to show a complex impedance, and not being as good as one would wish or expect. I think that is also close to what 35, reported the other day at about 10' feet.

I say my A99 now appears resonant at 27.205, but that is just a guess, and the reactance doesn't support that idea, so I call it a complex impedance situation.

I still have a vague recollection that I've seen a near perfect match on this very same A99 scanning the VA1 at the feed point before, but it was up about 15' feet high I think. Do any of the guys over in your area do any analyzer testing on the A99 that you know of?

I'm sorta' waiting on 35.

BTW, do you have any opinion as to why 35's VNA might have shown those erratic results when he had his bluetooth setup at the fed point?
 
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i would say shortening your 1/2wave jumper by the length of the coax from the so239 to the feed-point would be closer to having an electrical 1/2wave between your va1 and the feed-point but you will always have the bump where the the end of the internal coax is split and soldered to the so239.
 
i would say shortening your 1/2wave jumper by the length of the coax from the so239 to the feed-point would be closer to having an electrical 1/2wave between your va1 and the feed-point but you will always have the bump where the the end of the internal coax is split and soldered to the so239.

I agree Bob, this connector will make some very small technical difference, but IMO...if what you're suggesting is enough difference to matter, then all of our coax use with these connectors attached properly would be questionable.
 
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Well guys I decided to do my test of my A99, with and without a feed line again. This time I isolated the antenna from the mast, just in case that made the difference in what I saw testing this same idea several year ago.

Here is a video I did today in about an hour that shows what I saw.

All I'm trying to do is to check and see if we don't have a feed line or a mast on the A99, will it ill-effect the match...since according to many claims this end fed half wave must have the other half of the antenna to work right.

I recall that Northern35, did this test with his analyzer a while back, but his results were way off. I think that is exactly what he was expecting to happen. I also guess that convinced many that my idea was not so good, so I decided to try the comparison test again, and do a video to see if I could duplicate what I originally saw and here are those results.

What do you think?

A99 test with my VA1 analyzer - YouTube

Here are my dummy load testing notes:

View attachment A99 notes on VA1 analyzer.pdf
 
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For a half wavelength antenna I am no longer sure that you need that "other half" that I have personally said myself in the past you need. Marconi's video reminded me of a diagram I've seen where an end fed half wavelength antenna is coming off of a single feed from a parallel feedline, and the other feed is not used (or it just stops). After doing some looking around I have found those diagrams and did some reading.

In the third edition ARRL antenna book it talks about feeding a half wavelength antenna with parallel feedline. It doesn't have an "other half" attached to the other wire in the feedline, that wire simply stops where the half wavelength antenna begins. It also shows diagrams that show the current layout for a correct and both incorrect (long and short) versions of such an antenna. It also talks about using a quarter wavelength multiple of feedline for connecting such an antenna to a tuning device for easier tuning. Yes, I said quarter wavelength multiple there, not half wavelength multiple.

If I get some time tomorrow I'll see about typing it in and scanning in the two figures to see if it is relevant to the discussion.


The DB
 
If northern35 got different readings than you; then perhaps he needed to play with the tuning rings on it until he found the sweet spot. After all, those rings are on that for that expressed purpose of tuning the antenna. Maybe he didn't bother or there was something wrong with the antenna/needed a'fixin.

I trust your readings were correct and your method looked sound.

The EFHW was designed to come up with all of the right readings; but that doesn't necessarily mean that it is as efficient as it could be when real power is applied to it. In the real world using it, it would have to use a piece of coax to transmit with - of course. It would use the shield of the coax as a ground plane; but we already know this.

Kinda like what DB said on a similar thread a couple of weeks ago. Any antenna wants to behave like a dipole, as it will need some type of return path. Pardon my paraphrase; but this is so. There are exceptions - of course ('J-pole').

Wasn't northern35 supposed to document the difference between what you did and then adding the required ground planes, coax choke, and insulate the mast by using a fiberglass pole 1/4 wavelength long and then compare; or did I miss something?
 
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If northern35 got different readings than you; then perhaps he needed to play with the tuning rings on it until he found the sweet spot. After all, those rings are on that for that expressed purpose of tuning the antenna. Maybe he didn't bother or there was something wrong with the antenna/needed a'fixin.

I trust your readings are correct and your method looked sound.

The EFHW was designed to come up with all of the right readings; but that doesn't necessarily mean that it is as efficient as it could be when real power is applied to it. In the real world using it, it would have to use a piece of coax to transmit with - of course. It would use the shield of the coax as a ground plane; but we already know this.

Kinda like what DB said on a similar thread a couple of weeks ago. Any antenna wants to behave like a dipole, as it will need some type of return path. Pardon my paraphrase; but this is so. Wasn't northern35 supposed to document the difference between what you did and then adding the required ground planes, coax choke, and insulate the mast by using a fiberglass pole 1/4 wavelength long and then compare; or did I miss something?

I think you pretty much covered the situation Robb.

I still believe the idea that was presented here by: Steve Yates where he is suggesting and showing his work and testing...that an EFHW only needs approximately .05wl of wire to provide the necessary return current path. So, if he's wrong then I'm wrong.

If you will read his attached published work article you'll see there are plenty of opinions that suggest the EFHW will not work at all, forget the coax shield or the mast.

Thanks for your comments Robb and theDB.

Note: I will be posting this information in a new thread of its own in order to follow up if there is any interest.
 
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Just read that link you put up on Steve Yates; thanks.

Saw that part about the return path length for the EFHW. It may well be correct. But here we go again, in real world applications these antennas have always been stinkers, as far as CB operators using the A99 and throwing off massive CMC's.

Began to re-think what could be the real cause to this CMC dilemma. Perhaps those who use this antenna are using improperly modified radios that are throwing off harmonics and spurious transmissions; then these out of band freqs are being transmitted through this antenna. In which case, the A99 antenna is broad-banded. But not as broad-banded as the signals presented to the antenna from these modified radios that are giving off freqs below and above ('spurious and harmonic') of what this antenna was designed and tuned for. These can only become the CMC's; unless I failed to see something else.

Of course, if one uses an antenna analyzer they will never see these issues. Simply because it doesn't put out enough power and therefore not enough spurious or harmonic freqs emissions. Its use did create an honest but sterile environment; not a real-world use scenario. Must be the CB operator running a nasty radio. That is how I reason the disparaging differences.

These spurious and harmonic radiations may end up as the cause for these EFHW CMC's. Or any antenna - for that matter. In which case, a choke built and tuned for 27mhz may well not be effective with the freqs being presented to it. Just some thoughts . . .
 
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Just thought I'd drop a line to say I haven't forgotten the project, time is not something I'm endowed with at the moment, currently working six 12 hour shifts a week means I'm certainly not going to do anything this month, however I've got a couple of weeks leave coming up at the beginning of September so there's a chance I'll be able to retest then.

Just to clarify I believe the spikes in the no coax test to be as a result of wind, nothing nefarious, the VNA was used in exactly the same manner for the other tests, other than connected to coax, still using bluetooth and with me around 15' away from the antenna.

When I do get round to testing there's another element to the test I'd like to add, and that's feedline current sensing, a simple home brew current sensing probe, I'll squeeze some watts up the pipeline for this though. It was Tom Rauch's comments that made me consider the latter in this article:

End fed 1/2 wave matching

If we truncate a counterpoise, we greatly increase voltage on the counterpoise and the side of any matching system connected to the counterpoise. Voltage increases enough to allow the "countering" current to flow into whatever is around the feedpoint, including the feedline, as displacement or conducted currents, or a combination of the two.

The fact the feeder becomes involved does not mean the antenna will abruptly stop working. A seriously truncated counterpoise just means the system is ripe for increased feedline common mode problems.
 
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Just thought I'd drop a line to say I haven't forgotten the project, time is not something I'm endowed with at the moment, currently working six 12 hour shifts a week means I'm certainly not going to do anything this month, however I've got a couple of weeks leave coming up at the beginning of September so there's a chance I'll be able to retest then.

Just to clarify I believe the spikes in the no coax test to be as a result of wind, nothing nefarious, the VNA was used in exactly the same manner for the other tests, other than connected to coax, still using bluetooth and with me around 15' away from the antenna.

When I do get round to testing there's another element to the test I'd like to add, and that's feedline current sensing, a simple home brew current sensing probe, I'll squeeze some watts up the pipeline for this though. It was Tom Rauch's comments that made me consider the latter in this article:

End fed 1/2 wave matching

Sounds like a plan to me 35.

I've seen my VA1 go wild and crazy too. I just thought it was some strong signals in the area...so I waited and tried again latter.

I don't think I can do such testing here, but your idea may possibly provide additional elements to what is really going on and needs to be understood too.
 
im not sure what it is you want anybody with an analyser to confirm eddie?,

i don't see anything odd in your test, id expect about the same if i hooked my minivna to an a99 like that,

the a99 has the coax braid from feedpoint to s0239 and back up the tube as a counterpoise, its not possible to do a no counterpoise direct fed test on an a99 or imax without dismantling the antenna.
 
im not sure what it is you want anybody with an analyser to confirm eddie?,

i don't see anything odd in your test, id expect about the same if i hooked my minivna to an a99 like that,

the a99 has the coax braid from feedpoint to s0239 and back up the tube as a counterpoise, its not possible to do a no counterpoise direct fed test on an a99 or imax without dismantling the antenna.

Yep Bob, we've talked about your idea before, several times, and to be accurate you are probably right technically, the real A99/Imax feed point is located up inside the mounting base and not at the SO239 where the feed line connects. And, Steve Yates reports that an EFHW without a counterpoise, as he describes in several shapes and designs, theoretically will not work either unless the matching is right and shows to be resonant and resistive. He says if this matching is not done correctly...then the system will find something for the return path for currents to respond to that won't work without issues. He further adds that it is similar to a counterpoise, but there will likely be some bad issues pop up.

I look as this issue this way. For years I've heard guys claim that the A99 uses the feed line as the counterpoise for this EFHW radiator and that is simply why we hear so many bad reports. The key word here is feed line, and herein lies a distinction that IMO is suggesting the idea about FL on the A99 has either been proclaimed as CB/Ham BS for years, or the Solarcon design works just like Yates talks about. IMO, if this is not the case then the story about the A99/Imax is probably misunderstood...so we hear a lot of complaining about the A99/Imax radiating from the feed line. According to Yates it is true that an EFHW can respond just like the stories we hear tends to suggest, but if the antenna system is done right...that is not the case. I believe the Solarcon's design is probably a good design that sometimes is not right on the money...due to bad construction techniques like I found...a bad solder job.

Bob, if we had argued before Steve Yates did his work on the EFHW, that the counterpoise in this case...only needs to be .05wl long in order for a resonant and resistive EFHW to work effectively, and thus not respond with any of the bad issues we hear talked about in the CB/Ham world...do you think anybody would have listened? Probably no one would pay us any attention, nor consider any other explanation.

IMO, many are still not giving this phenomenon its due consideration and therefore much misunderstanding still prevails. I've had several A99's over the years with two among them really acting badly...just like stories we here suggest, but I don't think for one minute the problem happens because the antenna needs to use the feed line inorder to make a good match and complete the other half of the antenna. To me the antenna using the feed line as a counterpoise is only a symptom of he problems, and not the cause.

Anybody that reads the Yates report might understand in the reading that if the matching is not pretty much right on the mark...then all the claims for years we've heard regarding how the feed line radiates and serves to provide this EFHW radiator with its necessary other half...suddenly comes into play.

I wasn't talking technical BS or even thinking about what Yates and you have come up with in these ideas. When I got the notion to see if testing an A99 without a feed line attached, really made a noticeable difference in the match, I had no clue what the result might show. But I figured most would have said, "...that will probably mess up the tune...," similar to what Yates tells us can happen... without the counterpoise attached.

Bob in my mind, then and now, I don't think of this except to say, Steve Yates gave me a heads up, that if an EFHW tuning setup is done correctly, then all the CB/Ham BS we've heard for years...just ain't true and won't likely happen.

When I reported my results testing with my VA1 analyzer connected right at the SO239 of my A99, I took some flak "...that this was not possible, because the A99 uses the feed line for it to work." I had no intentions of trying to get your point or the ideas that Yates reported across to anybody, but I thought such a test on video might be helpful. I rectum' I was wrong.:headbang
 
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Yep Bob, we've talked about your idea before, several times, and to be accurate you are probably right technically, the real A99/Imax feed point is located up inside the mounting base and not at the SO239 where the feed line connects. And, Steve Yates reports that an EFHW without a counterpoise, as he describes in several shapes and designs, theoretically will not work either unless the matching is right and shows to be resonant and resistive. He says if this matching is not done correctly...then the system will find something for the return path for currents to respond to that won't work without issues. He further adds that it is similar to a counterpoise, but there will likely be some bad issues pop up.

I look as this issue this way. For years I've heard guys claim that the A99 uses the feed line as the counterpoise for this EFHW radiator and that is simply why we hear so many bad reports. The key word here is feed line, and herein lies a distinction that IMO is suggesting the idea about FL on the A99 has either been proclaimed as CB/Ham BS for years, or the Solarcon design works just like Yates talks about. IMO, if this is not the case then the story about the A99/Imax is probably misunderstood...so we hear a lot of complaining about the A99/Imax radiating from the feed line. According to Yates it is true that an EFHW can respond just like the stories we hear tends to suggest, but if the antenna system is done right...that is not the case. I believe the Solarcon's design is probably a good design that sometimes is not right on the money...due to bad construction techniques like I found...a bad solder job.

Bob, if we had argued before Steve Yates did his work on the EFHW, that the counterpoise in this case...only needs to be .05wl long in order for a resonant and resistive EFHW to work effectively, and thus not respond with any of the bad issues we hear talked about in the CB/Ham world...do you think anybody would have listened? Probably no one would pay us any attention, nor consider any other explanation.

IMO, many are still not giving this phenomenon its due consideration and therefore much misunderstanding still prevails. I've had several A99's over the years with two among them really acting badly...just like stories we here suggest, but I don't think for one minute the problem happens because the antenna needs to use the feed line inorder to make a good match and complete the other half of the antenna. To me the antenna using the feed line as a counterpoise is only a symptom of he problems, and not the cause.

Anybody that reads the Yates report might understand in the reading that if the matching is not pretty much right on the mark...then all the claims for years we've heard regarding how the feed line radiates and serves to provide this EFHW radiator with its necessary other half...suddenly comes into play.

I wasn't talking technical BS or even thinking about what Yates and you have come up with in these ideas. When I got the notion to see if testing an A99 without a feed line attached, really made a noticeable difference in the match, I had no clue what the result might show. But I figured most would have said, "...that will probably mess up the tune...," similar to what Yates tells us can happen... without the counterpoise attached.

Bob in my mind, then and now, I don't think of this except to say, Steve Yates gave me a heads up, that if an EFHW tuning setup is done correctly, then all the CB/Ham BS we've heard for years...just ain't true and won't likely happen.

When I reported my results testing with my VA1 analyzer connected right at the SO239 of my A99, I took some flak "...that this was not possible, because the A99 uses the feed line for it to work." I had no intentions of trying to get your point or the ideas that Yates reported across to anybody, but I thought such a test on video might be helpful. I rectum' I was wrong.:headbang
Marconi. you're so full of shit it oozes out your ass onto the causeway
 

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