Can I use a tracking generator in place of a sweep generator? - Page 1
Forum section: electronics / rf-microwave

author: N0NB
author_rank: Contributor
timestamp: December 22, 2021, 05:50:49 pm
content: I am working through alignment of a Kenwood TS-130SE I bought earlier this year. The service manual specifies a sweep generator and oscilloscope to align the various bandpass filters. While I have a decent enough 'scope, I lack the sweep generator.I do have a communications service monitor that has a tracking generator. Is there a reason I cannot use the tracking generator to do the alignment?

author: 9aplus
author_rank: Regular Contributor
timestamp: December 22, 2021, 06:06:54 pm
content: In case that your tracking generator covers needed freq you can use it with service monitorin spectral analyzer mode - all in case that resolution is fine enough.In that case your scope can not be used, because you are missing proper time base source.On the other hand if you put scope on low time base and tracking generator in slow sweep -you still have some amplitude indication of bandpass response.

author: bob91343
author_rank: Super Contributor
timestamp: December 22, 2021, 06:45:55 pm
content: The tracking generator should work as long as the amplitude is proper. However I do question the need for alignment. If the radio works, don't fix it. Those adjustments rarely, if ever, need tweaking.

author: xmo
author_rank: Regular Contributor
timestamp: December 23, 2021, 12:22:50 am
content: Several considerationsThe instructions will tell you where the sweep generator connects and where an RF probe is put to monitor.If the monitor point is at the same frequency as the point where the signal is inserted - your SA/TG will work fine.If there is any up or down frequency conversion between those points - you have a problem. A broadband RF oscilloscope probe doesn't care about that but your SA/TG does unless it has offset capability.Also, remember that the drawings of scope traces in the manual show linear response but your SA/TG will start out with a log display unless you change it.

author: N0NB
author_rank: Contributor
timestamp: December 23, 2021, 12:56:51 am
content: Thanks for that feedback. It is very valuable as I hadn't considered the frequency conversion possibility. I will study the manual on this.Part of the reason I am going through it is because while it does receive "fair" I think it could be improved. I recall back in the early '90s going through the alignment procedure that was in the operator's manual for the TS-830S that I had. That radio wasn't even ten years old at the time and the alignment made a very noticeable improvement to the receiver.As this '130 is nearly 40 years old and as I have no idea of its history and since the S meter was nearly unresponsive, I think just going through it would be a good exercise. Already I have found the carrier board frequencies needed some touch up but the VFO is spot on.

author: N0NB
author_rank: Contributor
timestamp: December 23, 2021, 01:26:30 pm
content: Yes, there is a frequency conversion in the signal path so I've purchased a used BJ Precision 4045 sweep/function generator. It's more test gear. What's not to like?

author: bob91343
author_rank: Super Contributor
timestamp: December 23, 2021, 06:28:15 pm
content: One way to tell if the filters need alignment is to measure the sensitivity across the band. If it's more sensitive at one end than the other, or changes substantially when changing bands, it may need alignment.The alignment adjusts for constant sensitivity across each band.When I say 'band' I refer to the passband of the filter, which gets switched at various points in the tuning range.This is not a simple issue, so alignment should not be attempted unless you know what you are doing.

author: xmo
author_rank: Regular Contributor
timestamp: December 23, 2021, 08:02:35 pm
content: The 4045 looks like a nice unit. EEVblog is the home of "It's more test gear. What's not to like? "-----------------Bob's cautions are prudent. Especially when starting an alignment process with an unfamiliar instrument. Your initial display should look very close to the expected waveform before you touch any adjustment.If you find one that looks a little off, tweak that. Major movement of any adjustment should not be necessary. After tweaking just one, test the unit to see if things have improved for that one. Then proceed to do the others.Good luck.