How To Test Radio Repeater Power, Sensitivity and Desense (Revised Version)

[@PowderMill]

Nice video… I must haveI missed it 4 years ago. But, as I’m always late for everything, it’s probably about time it popped up in my “Recommended” list. LOL It’s a rainy, cold and miserable for us old-timers w/arthritis (I’m actually only 58, but FEEL much older as I have Ankylosing Spondylitis), so it’s a perfect day for binge-watching RF videos. 😊 73 + Thanks!

[@PowderMill]

Forgot to mention: My Wife and kids are rapidly tiring of my selections and now wondering…. What’s the set of videos for a miserable weather Sunday? I initially selected either Quantar pre-selector tuning -OR- Finding a PEP modification kit for an older TeleWave 44D watt meter. ⚠️ Absolutely NO “Rom Coms”!! The womenfolk took advantage of my feeble mind and my lack of current “Girly Stuff” knowledge and terminology. They tricked me last time!! “ROM COM” = Most definitely *NOT* topics dealing with memory and communications.!! 🤣 Thank you for your content!

[@jorgezuni2818]

So the bigger the - 120 dbm is a greater Receiver sensitivity then let’s say -70 dbm ???

[@jbx907]

when can we buy that coupler, i have a separate signal gen.

[@RadioTech7388]

The correct and only way to do the test is as follows: 1. Set up the RX test with sig gen and monitor the RX audio for SINAD and test without the TX running. eg. -120 dBm gives say 20 dB SINAD. Then whilst measuring the RX SINAD switch the TX on and note any changes in the RX SINAD say for example you measure -118 dBm so a change of 2 dB. From this you can conclude the de-sensing is measured at 2 dB.

[@patiocooking]

As a field tech I always start with doing desense checks over the air before I touch any of the connections.

[@johnkresek871]

I'd like to add what I believe to be a constructive comment about the desense test that will make it a useful test (Your test really just measured the isolation of your Iso-T and that is really not all that important). Your second desense test would normally be to test how the noise floor at a site affects the receive sensitivity for this installation. For the second desense test that you did using the Iso-T or whatever you prefer to call it, you did not complete the second step in that procedure which is to replace the 50 ohm dummy load with the actual antenna. Desense due to the noise floor at a com-site will be the difference in test generator signal level required for the same indication that you had with the dummy load. Some might insist that a 12 dB SINAD test is the "proper way" but as you did it where you listen to signal as it opens the squelch you will probably get about the same results once you become familiar with what to listen for by ear.

[@kd5yut]

perfect

[@mgcostello]

Hello Mr Repeater. Great video for a novice. I have a question. If I want to test the whole system, including the antenna, installed at a site, how should I do it? Can I get a signal generator/amp and antenna and broadcast to and receive from the repeater, and check sensitivity levels, output frequency and power?

[@glenng.8254]

You need to test each sector individually, starting at the antenna and working out to the receiver, then the transmitter.

[@samuel5038]

Saludos amigo desde la repuplica de Ecuador, me compré ese Monitor de servicio ifr1600s, estoy empezando con las comunicaciones y deseo que me guie como ajustar un duplexor para usarlo en un repetidor vhf, como ajustar la pantalla para una mejor visualizacion de as curvas. exitos

[@enzopulido2579]

Hi how can you avoid desensitization in a Mobile communications Van where 3-4 vhf radios might transmit 2 at a time and receive 2 at a time. How should I separate the mobile antenna?

[@MrRepeater]

You need a set of filters on each receiver.