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Well Rabbit.
He had no explanation as to how he went about figuring what he did.
The model he is basing it on is a single solid element
The Archer is 2 separate driven elements being combined together using dissimilar materials.
The guy types like 91xg without the rambling.
Oh, OK. That would mean your explanation is better than his.:smile



The first image shows a Gamma Match. It is a way to match a dipole to a coax line, but there is no balun. The position of the tap is adjusted to match the impedance of the feedline. The capacitor cancels out the reactance of the gamma rod.



In photo 2 I see a 3/4 wave folded dipole connected to a coax line. The folded dipole is a balanced element; the coax is an unbalanced line. I see no Gamma Match or balun. Usually, a 300 balanced line or a 4:1 balun is connected to the DE.



Is photo 3 his antenna?

That's not a Gamma Match. I can't tell what's on top. It looks like the DE is a rod dipole split in the center. The coax, which is an unbalanced line, is connected to a dipole, which is a balanced element. I see no Gamma Match or balun.

And, what is that extra wire?

Just because the gentleman got it to work, doesn't mean it's the best way to do it.

Gain tests and SWR measurements would be needed to document any improvement.

I'm not impressed with his design.
 

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Gamma matches are common with Ham radio antennas. My 10-meter beam uses two, one for horizontal polarization and one for vertical polarization (duplicate sets of orthogonal elements). I have two 2-meter beams that also use them for matching. Since they provide “narrow” matching, usually, they are adjusted by exciting with a low power transmitter and adjusted for lowest SWR (Standing Wave Ratio) at the center of the band (or at the preferred operating frequency). The 10-Meter HAM band is only ~1.7 MHz wide and the 2- Meter HAM band is only ~4 MHZ wide. Compare that to the bandwidth of a single TV channel @ 6 MHz and I don’t think a Gamma match would be desirable for a TV antenna.
 

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I don’t think a Gamma match would be desirable for a TV antenna.
Hello, Pete; good to hear from you. I hope you are staying well.

Yeah, the gamma match isn't very suitable for a TV antenna, except maybe for a single channel Yagi.

I sent an email to you about your SDR tutorial. I see it is no longer on HighDef because that forum folded. I should have made a copy of your excellent thread.

I was hoping you would reconstruct a short version of your tutorial on this forum or AVS so that I could send people to it for help with the DIY software.
 

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Rabbit 73,

Yes, we're staying as safe as we can. Unfortunately, I didn't save any of the material I wrote over the years so I wouldn't know where to begin. I had links to the various topics I wrote about that I referred to instead of having to re-research them again. Len also asked for a tutorial. Sorry to see HighDef forum go away. It was a valuable source of information.
 

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Unfortunately, I didn't save any of the material I wrote over the years so I wouldn't know where to begin.....Len also asked for a tutorial. Sorry to see HighDef forum go away. It was a valuable source of information.
I understand.
This is a little off-topic, but while I have your attention:
I think I will now recommend the SDRplay RSP1a instead of the RTL-SDR dongle because so many people have trouble with the dongle open-source DIY spectrum analyzer software. The RSP1a is a little more expensive, but it is within the budget of a dedicated hobbyist. It has a 10 MHz bandwidth with the SDRuno software that is able to show a whole channel and there is ready-to-use spectrum analyzer software that can show a wider span.



 

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Rabbit73,

I agree that the Radio Spectrum Processor 1A14-bit SDR is a much better unit than RTL-SDR dongles I bought. The dynamic range of the 14 Bit A/D, wide bandwidth and HF range coverage make it worth the $ 119.95 HRO charges.

I paid $6-$7 for my units and mostly use SDR# for listening to FM radio. I did set-up two to follow trunking radio signals and frequently use RTLSDR Scanner for looking @ off-the-air signals, comparing antenna signal strength differences, filter attenuation etc. I actually find RTLSDR Scanner easier to use for quick comparisons than my HP 8590 Spectrum Analyzer.
 

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I did set-up two to follow trunking radio signals and frequently use RTLSDR Scanner for looking @ off-the-air signals, comparing antenna signal strength differences, filter attenuation etc. I actually find RTLSDR Scanner easier to use for quick comparisons than my HP 8590 Spectrum Analyzer.
The first part of your tutorial thread still exists in an archive.

I made a post about it on the Antenna Thread at AVS, post #18476 of 18495, 05-14-2020, 08:49 PM

This is an image from your first post; it didn't show unless you were signed in:

 

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rabbit73,

I couldn't find anything. If you've found some of my RTLSDR posts pleas feel free to re-post them for everyone. Thanks, Pete.
 

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Oh, OK. That would mean your explanation is better than his.:smile



The first image shows a Gamma Match. It is a way to match a dipole to a coax line, but there is no balun. The position of the tap is adjusted to match the impedance of the feedline. The capacitor cancels out the reactance of the gamma rod.



In photo 2 I see a 3/4 wave folded dipole connected to a coax line. The folded dipole is a balanced element; the coax is an unbalanced line. I see no Gamma Match or balun. Usually, a 300 balanced line or a 4:1 balun is connected to the DE.



Is photo 3 his antenna?

That's not a Gamma Match. I can't tell what's on top. It looks like the DE is a rod dipole split in the center. The coax, which is an unbalanced line, is connected to a dipole, which is a balanced element. I see no Gamma Match or balun.

And, what is that extra wire?

Just because the gentleman got it to work, doesn't mean it's the best way to do it.

Gain tests and SWR measurements would be needed to document any improvement.

I'm not impressed with his design.
Well he sure was. :)
 

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I understand.
This is a little off-topic, but while I have your attention:
I think I will now recommend the SDRplay RSP1a instead of the RTL-SDR dongle because so many people have trouble with the dongle open-source DIY spectrum analyzer software. The RSP1a is a little more expensive, but it is within the budget of a dedicated hobbyist. It has a 10 MHz bandwidth with the SDRuno software that is able to show a whole channel and there is ready-to-use spectrum analyzer software that can show a wider span.



I understand.
This is a little off-topic, but while I have your attention:
I think I will now recommend the SDRplay RSP1a instead of the RTL-SDR dongle because so many people have trouble with the dongle open-source DIY spectrum analyzer software. The RSP1a is a little more expensive, but it is within the budget of a dedicated hobbyist. It has a 10 MHz bandwidth with the SDRuno software that is able to show a whole channel and there is ready-to-use spectrum analyzer software that can show a wider span.



Glad I stopped in.
I am about to pull the trigger on NooElec NESDR Smart v4.
Made in the USA.
Not sure what the learning curve is going to be.
 

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It certainly isn't a true PCB balun. Its just a ferrite bead attached to a board.
 

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It certainly isn't a true PCB balun. Its just a ferrite bead attached to a board.
True. Which there is nothing wrong with. I find it interesting that a ferrite balun is being produced on a pcb board. Perhaps testing has found that the old ferrite actually has better performance characteristics.
 

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I understand.
This is a little off-topic, but while I have your attention:
I think I will now recommend the SDRplay RSP1a instead of the RTL-SDR dongle because so many people have trouble with the dongle open-source DIY spectrum analyzer software. The RSP1a is a little more expensive, but it is within the budget of a dedicated hobbyist. It has a 10 MHz bandwidth with the SDRuno software that is able to show a whole channel and there is ready-to-use spectrum analyzer software that can show a wider span.
I am currently looking at this one. NANOVNA Bundle.
NOOElec is supposedly manufacturing in the USA and Canada.

There are a lot of Chinese clones out there from different companies with all sorts of different quality control standards.

I am running down so more info from them. However among the things it can do is Full plots, VSWR, smith charts and s parameters.
I believe it can also plat the radiation patterns.



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