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Old 13th Jun 2018, 11:09 am   #2
Radio Wrangler
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,763
Default Re: Scope specification for FM use?

10.7MHz for the IF, but it would be good to have several harmonics so you can see IF waveforms being compressed by the limiters so a 50MHz scope works well unless you want to see the local oscillator. Scopes don't stop dead at the quoted bandwidth, that number is the minimum frequency of the 3dB point. A 100MHz scope will show the LO signal and the RF (if the latter is big enough) though the voltage measurement accuracy will be a bit off.

I've used 50MHz and 100MHz scopes and never had any problems.

On the second hand market, they all seem to be in the same price bracket, so you may as well have something decent.

Tek scopes like Fluke meters carry premium prices.
HP scopes are good and lack the Tek premium price because there is a legend that HP scopes don't trigger. Oddly, all mine have no problems and the legend lets me pick them up quite cheaply. Hameg are Rohde & Schwarz and are good too.

The Tek 465 family and the HP1740 are quite portable and fairly small, and are pretty comprehensively equipped. The HP doesn't need a fan, while the Tek fan can be a bit noisy in a quiet room. I have a couple of each.

Philips made some reasonable ones and some not so good ones, but I don't know my way around them. The old Cossor CDU150 is reasonable. But there's a good following on here of Tel?HP/Hammeg so knowledge and the odd part are available.

David
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