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.
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
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.
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 ...
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.
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.
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 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.
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 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…
if you want to experiment, here is schematics: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-yGKWBpgN8PU.html it is a simple resistive bridge that is used to measure amplitude and phase. the hardware is easy
