#620

Episode 620
I measure the return loss of a 2M J-pole antenna using a return loss bridge and a coupler. A spectrum analyzer with tracking generator is used.
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[@Koerperklaus3000]

Great video, so close to daily problems in ham radio life. Very helpful!

[@t1d100]

I am not a radio guy and know nothing of antennas. However, I watched the video, because I know that you make great videos and I will learn something. You did not disappoint! Kudos. And, yes, it was all easily understandable.

[@PapasDino]

Actually you made the topic a bit clearer! Thanks for sharing and Happy Thanksgiving!

[@vidasvv]

Nice job on ur demonstration !!! TNX 4 the upload !

[@lordgarak]

I have one of those bridges and it's been a total mystery as to what port is what on it. I've had it for years. Mine has the sharpie mark on it too. Just yesterday I was connecting it up to the NanoVNA and trying to figure it out which port is which. Even looking at the PCB I couldn't figure it out. After watching one of your other videos on bridges and this video it's now making sense. Thanks and 73, VE1LX

[@mikefahmie7506]

One difference I see is that, when using the bridge, the generator always see at least a 100 Ω load despite what the DUT looks like. With the Directional Coupler, the generator essentially see's the unbuffered impedance of the DUT. This may cause some uncertainty in the excitation voltage, it can be minimized with an attenuator at the couplers end of the generator cable.

[@johnlegros1586]

rewindme 40 years back , thanks ! I used bridges for greater sensitivty at the time , using Telonic sweeper and RF detector, most important is to have good matching on all ports except the DUT , usually bridges have wider bw ...

[@mariofilippi3539]

Been a ham for four plus decades and was always confused about return loss bridges vs directional couplers. Your video was superb in explaining the differences. One thing - couplers are much cheaper than return loss bridges so why spend the extra money? Thanks very much and 73's.

[@HelmutTschemernjak]

Very cool, thank you for educating us. Great stuff. Regards from Germany. Why not to add a PayPal Link, I am happy to support your Lab within payments from time to time. Patron is is not perfect for me because I don't like to have regular payments. In case you have a good source for the bridge and/or coupler, a URL in the description would be great.

[@FUNKLABOR_DL1LEP]

Great! I tried the Adalm Pluto with Software 'Satsagen' as Generator - it works great! Greets , DL1LEP Jens

[@johnham9256]

good video. what's inside the coupler?

[@deanlaclair265]

What is the impedance of your generator? did you use an attenuator inline? Thanks for video

[@jdmccorful]

Hmmmn ,,,, alot to learn on my part.

[@w2aew]

I was surprised that the coupler gave you essentially the same output level as the bridge. Just luck (or good planning) that the coupler's fwd coupling ratio matched the bridge's ratio?

[@IMSAIGuy]

must be. I expected the bridge to be more output.

[@sebastianocoppolella7637]

@@IMSAIGuy Hello Usually the RF bridge has a greater loss of passage but has a better directivity and therefore more precise and suitable for measuring DUT of high Return Loss, the Chinese one I don't think has good parameters. Just today I uploaded a video where I make precision measurements using a VNA with measure S21 + external bridge and the errors are predictable with some precision as they depend on the amplitude and phase of the direct and reflected signals encountered in the bridge or coupler directional. With this system I am able to obtain a greater precision than an S11 measurement, precisely because of the directivity of the bridge of the VNA instrument.

[@chrislemus9392]

Very cool

[@SpinStar1956]

Really good video, because I've heard these "RF-Experts" tout one or the other. The only thing that I was concerned about (since I really only mess with HF) is the low-frequency limit, that on the couple was 10MHz. What if you want to have something that would work even to a very low IF of say 50KHz? The reason I ask is, could this technique be used for interstage impedance-matching? Do you have a video on construction of both of these? Anyway, thee RF videos are really helpful and you seem to cover well the traps that are so easy to fall into for us casual RF's! Thanks & 73...

[@IMSAIGuy]

get a NanoVNA they just use a bridge circuit inside. will operate to 10khz I believe

[@SpinStar1956]

@@IMSAIGuy OK great suggestion, I was just trying to learn how to make these things to some degree of usability, but needed the low frequency response. Thank you anyway. 73…

[@IMSAIGuy]

if you want to experiment, here is schematics: kzbin.info/www/bejne/r3iuiHWmnLNrhrc it is a simple resistive bridge that is used to measure amplitude and phase. the hardware is easy

[@IMSAIGuy]

same used in LCR meters: kzbin.info/www/bejne/e5XJZ2tso8p0jtU

[@macstan9717]

nie widać kabli lączących i urządzeń...

[@galileo_rs]

AFAIK both are essentially the same thing.

[@galileo_rs]

@@psehorne Besides the fact that you do not understand how these work, there is an edit button on the comments.

[@galileo_rs]

@@psehorne Could not care less, there is plenty of resources online to educate yourself on the basic.

[@galileo_rs]

@@psehorne What is in it for me to provide you with basic education?

[@galileo_rs]

@@psehorne Bravo, now what is a dual directional coupler. 17dB of RL is pretty bad for a 50Ω load.

[@galileo_rs]

@@psehorne Using other peoples comebacks is a bit pathetic. Anyway figuring out this one is the next step in your educational path.