HB9UF: Desense Testing 

Thanks! Let me know if you have any particular questions.

Did you make your ISO-TEE or is this one you purchased? I have seen and I was even given one where the center pin was simply removed.

You are right, those are fairly easy to home-brew using the technique you described. The one I use in the video is purchased though, it is an RFA-4059A that I got from those guys: www.rfparts.com/signal-samplers/rfa4059a.html It came with a nice calibration curve and you can coarsely adjust the coupling because the "tap" slides back and forth before it is fastened, but at the end of the day it's just a glorified version of what you described.

+MrCircuitMatt Normally I would measure SINAD on the AF off the receiver, then adjust the signal generator to a level through the ISO-TEE where I have 12dB SINAD on the receiver without transmitting. Then I fire op the transmitter and then adjusting the signal generator level to 12dB SINAD reading. The level difference between the to measurements is your desensitization level :) Sorry. One port duplex measurement is only an option on the R2600 series service monitor, not on the R2400 series.. My bad. But I have an R2001D/HS service monitor I normally use when I have on-site jobs, so I know the trouble about using an ISO-TEE.. I usually use my Bird 4431 wattmeter with variable RF tap instead off the ISO-TEE.. On the workbench I have the Schlumberger Stabilock 4032, the Stabilock 4040 and the Motorola R2600 service monitor. They all offer one port duplex measurement. I have just finished 2 UHF repeaters for rental :) What type of Procom filter are you using ? 73 de. OZ99DW

+Daniel Wahl Yes I did a similar test as well. I didn't show the whole thing because I think that a video blog is not the proper way to teach people how to build repeaters. This is more of a 'look how I did this, you might find it interesting or have comments' thing and I always enjoy it when it leads to discussions such as that one. Our group does have a service monitor with duplex measurement capabilities -- a R&S CMT54 if memory serves. This is not in my home lab though and I originally wanted to get as much as possible done at my place. This is why I did the two videos on the Bessel-Null method, and only then did this guy drop his old monitor in my driveway. That's why things might look a bit convoluted but I always enjoy experimenting and seeing what can be achieved with amateur-means. The Procom filters are BRBP70/6. I would have made a different choice there but that decision was made by my predecessor in the group and I can't overturn that. Good luck with your repeaters and 73 Matt

Usually it is a matter of improving isolation (or reducing output power)... what duplexer do you have? How much isolation does it have?