Can I measure sensitivity of a ham radio without a radio tester - Page 1
Forum section: electronics / rf-microwave

author: OE2WHP
author_rank: Regular Contributor
timestamp: November 29, 2017, 12:00:08 am
content: Hi,I am wondering if it is possible to measure snsitivity of a ham radio receiver without all the expensive gear. What I have on hand is an oscilloscope an arb sig gen., a Fluke 45 bench meter capable of RMS measurements, a Rigol spectrum analyzer but no radio tester, distortion meter or stuff like that.Is it possible to measure the 12dB SINAD sensitivity with my equipment? I didn't find a way but I'm far from being an expert.Thanks for your kind support.

author: denverpilot
author_rank: Regular Contributor
timestamp: November 29, 2017, 05:29:59 am
content: I think with rudimentary gear you can do *comparison* with a known sensitivity receiver, but it would be difficult to do a *measurement*, if that makes sense. But with a known sensitivity receiver you should be able to tell if a rig is operating nearly as well as the other.How accurate do you want to be?I found an out of cal older Motorola Service Monitor online for $300. Asked a friend who had more money and nicer gear than I did at the time to put it back to back with his HP and see if it was accurate. It was “close enough” for everything I was doing to within a dB of error, maximum.It was old and had analog CRT and analog pots including the very precise one for the signal generator’s output marked in dB, analog meters, but everything worked on it. It was a risk buying it, but I talked to the owner and they’d taken care of it, they’d just moved on to nicer gear. It didn’t go very high in frequency but I didn’t need to do anything in the GHz at the time. UHF was plenty high.

author: chrisl
author_rank: Regular Contributor
timestamp: November 29, 2017, 08:55:06 am
content: http://comtekk.us/sinad.htmYou can download their trial SW to try out. They also have $39 non-commercial license as well - you need to be a licensed ham operator.I used it a few years ago, and it worked well. I installed it on an old XP laptop and left it on for 3 months or so without rebooting.When I finally rebooted the machine it complained about the trail license being expired.

author: RFDUK
author_rank: Regular Contributor
timestamp: November 29, 2017, 09:58:07 am
content: Sounds like the thing you don't have at the moment is a calibrated signal generator. Useful older sig gens from LF to 1 GHz can be had on ebay for £100 upwards.If the receiver under test has SSB, AM or CW demodulators, then an inexpensive calibrated noise source can be used. Your Fluke with RMS would be used to measure noise on the receiver audio output. Seehttp://www.g8fek.comRXGen and other sources.Noise sources are NOT suitable for testing receivers with only FM demodulators though.

author: CJay
author_rank: Super Contributor
timestamp: November 29, 2017, 11:16:56 am
content: Quote from: RFDUK on November 29, 2017, 09:58:07 amBut is the calibrated signal source important if he can measure the output of the signal generator using the spectrum analyser?If that's the case then I *think* he's also got most of what he needs for FM too, just needs to add a pass filter for 1KHz to be able to measure SINAD?(think we've chatted at a rally or two BTW, impressive range of bits you sell, I keep meaning to buy one of the noise sources)

author: cdev
author_rank: Super Contributor
timestamp: November 29, 2017, 02:48:16 pm
content: You can do a very dirty AB test using CATV antenna switches and splitters and a variable attenuator, to compare to any other receiver. Using the same antenna and switching between multiple receivers using the same software.(if you are using an SDR that makes it easier.) If you are using a regular receiver, and want to know its weak points, getting an RTLSDR which accepts HF would be helpful as you can use it to examine the IF output.If you have any receiver you want to troubleshoot or evaluate, or fix problems with, tapping into its IF chain with an SDR is super useful.Also, you can set up a panadaptor for most superhet receivers that way.Its easier to tell what interference is and make guesses about its cause if you can see it. So an SDR that covers the range its IF covers is valuable.

author: David Hess
author_rank: Super Contributor
timestamp: November 30, 2017, 07:09:15 pm
content: You can do it with a square wave comb generator, calibrated RF attenuator, and good cables and maybe a shielded enclosure to prevent leakage around the RF attenuator. Measure the high absolute output of the comb generator, calculate the amplitude of the harmonic that the receiver will pick up, and use the RF attenuator to provide a calibrated low level signal to the receiver.