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Brian G8MUE · 22nd May 2015, 2:41 pm

Since my post in Aug 2012, I have continued to use my TR4172 despite the 30db deafness. When I switch on and set the centre to 145MHz and the span to 10MHz, the baseline (the middle of the noise fuzz) is at -83db (displayed). Connecting a signal of -50dbm from my HP8654A to input 1, is just visible in the noise. I have no reason to suspect the HP which also agrees with the 50MHz reference output from the TR4172. The input attenuator operates as it should on all steps. The pre-amp at input 2 works as it should.

Without a spare diode ring for the 1st mixer, I am reluctant to open it up. (A deaf SA is better than no SA). I have recently purchased (about £50 from a well known auction site) a "simple spectrum analyser" from Hong Kong. This USB instrument does seem to be able to make useful measurements of signal amplitude and frequency with an effective bandwidth of 250KHz. Frequency coverage is 138MHz to 4.4GHz (which will no doubt tell you which Analog Devices chip is being used). I was looking at the "RF section level diagram", Fig 10-10 in the TR4172 manual, and thinking how much of this I may be able to verify?

I am very interested if you can post or mail me some of the details you have found. Here in Cyprus it gets quite warm (it was 36C last Sunday) and I have found that in a number of instruments that have "plastic foam", the foam has turned to sticky tar. (This includes professional kit from Racal, B&K and HP as well as amateur items such as my KW2000 with its mechanical IF filter supported with plastic foam). Acetone is the only thing that I have found to clean the mess but it also dissolves many wanted items!

22nd May 2015, 2:41 pm	#16
Brian G8MUE Retired Dormant Member Join Date: Aug 2012 Location: Paphos, Cyprus Posts: 3	Re: Spectrum Analyser TR4172 Since my post in Aug 2012, I have continued to use my TR4172 despite the 30db deafness. When I switch on and set the centre to 145MHz and the span to 10MHz, the baseline (the middle of the noise fuzz) is at -83db (displayed). Connecting a signal of -50dbm from my HP8654A to input 1, is just visible in the noise. I have no reason to suspect the HP which also agrees with the 50MHz reference output from the TR4172. The input attenuator operates as it should on all steps. The pre-amp at input 2 works as it should. Without a spare diode ring for the 1st mixer, I am reluctant to open it up. (A deaf SA is better than no SA). I have recently purchased (about £50 from a well known auction site) a "simple spectrum analyser" from Hong Kong. This USB instrument does seem to be able to make useful measurements of signal amplitude and frequency with an effective bandwidth of 250KHz. Frequency coverage is 138MHz to 4.4GHz (which will no doubt tell you which Analog Devices chip is being used). I was looking at the "RF section level diagram", Fig 10-10 in the TR4172 manual, and thinking how much of this I may be able to verify? I am very interested if you can post or mail me some of the details you have found. Here in Cyprus it gets quite warm (it was 36C last Sunday) and I have found that in a number of instruments that have "plastic foam", the foam has turned to sticky tar. (This includes professional kit from Racal, B&K and HP as well as amateur items such as my KW2000 with its mechanical IF filter supported with plastic foam). Acetone is the only thing that I have found to clean the mess but it also dissolves many wanted items!