The AM Forum

Recently I posed a question about signal monitors, which cleared up some questions for me but raised others.

I was advised to steer clear of the signal monitor devices, mostly because they just do that and little else.  I was told I should get an oscilloscope instead.  This makes sense and I heeded this advice.

Some also told me that I should get a spectrum analyser.  I understand that a spectrum analyser is, in the end, an oscilloscope with a frequency sweep circuit used to display signal gain across a frequency range.  And I understand how useful they can be.  But I don't know if they can be used as a straight oscilloscope and also, thus, a signal monitor.  Can they?

Also, if I am looking to be able to monitor transmitted AM signals up to 2m, should I be looking for a 150MHz scope or something even higher?

Dave, to monitor 2 M signals you'll need a 400 MHz scope or better.  Probably not worth it.  And unless you're doing a lot of building and experimenting, a spectrum analyzer isn't going to be a good investment.  You can get a decent scope that will work fine at HF for $10 at any hamfest.  The cheapest spectrum analyzers around go for $200+, and they work poorly for signal monitors as their sweep is usually free-running and in any case is difficult to sync to the incoming signal.  The display is the AM detected RF signal and is usually logarithmic rather than linear (although this is USUALLY switchable).

Hope this helps.  73 John

Keep your eyes open at the flea markets. I bought a TEK 7904 for $75 and spent another $150 for plug ins. It can easily see a
1 GHz. carrier
A scope like that is a real find and sure a good class e learning tool.