Re: HP8640B Signal Generator
You're quite right, I can't disagree David.
My main use of a signal generator is simple alignment of commercial superhet receivers, complete with all their failings, so harmonic output doesn't usually worry me.
My Wavetek 2407 and Marconi 2008 have harmonics and usually these are invisible in practice. In fact I've never taken the trouble to measure them.
The HP is of course a loser from the start, generating square waves to produce its outputs. Although I suspect the even harmonics arise from square waves that are asymmetric. In the repair manual it does cover mods to its filters I guess to deal with component ageing but it would be an academic exercise to deal with this and time is quite valuable.
Nice to have would be a tunable band pass filter running say 50KHz to a gig with an out of band response 100dB down. Maybe chuck in an adjustable bandwidth as well.
Having said all this, the last receiver I looked at was a Marconi 730 a TRF design... so simple I found it incredibly boring. What I really like is a challenge, and the 8640B certainly supplied enough..
I can't immediately think of the next project unless it's a little box to extend the 8640B down to zero hertz... like the TF2008.
Allan G3PIY
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