Re: HP8640B Signal Generator
Yes, the vernier works perfectly. That was the pot on the rear of the attenuator that I changed.
I'm not too happy with the RF output on the low ranges and I need to work through all the meter adjustment pots and maybe bridge the 30pF on my RF detector with say 2.2nF or something greater. More experimenting needed.
Today I connected it to a spectrum analyser and realised the shortcomings re harmonics although only the ranges 500KHz to 4MHz are a problem.
I don't have the doubler fitted, in fact I don't really have a requirement up in those regions so won't miss it. I do have Option 001.
Signal generator output voltage is always a puzzle to me. Is the figure on the meter the open circuit voltage and, if connected to an external 50 ohm load, is this recorded externally as half that on the attenuator dial, and proportionally the number of dBm. Is the level indicated on the meter different to measured output power on a 50 ohm spectrum analyser?
The meter read 0dBm and the SA read +6.54dBm.. Then again I haven't gone through the calibration exercise so 0dBm on the meter could well be wrong...I suppose the handbook will cover this?
I haven't confirmed all the modulation bits and bobs work yet, but I did check wbfm on a broadcast receiver in passing and it worked OK. In fact when I tuned off a local FM broadcast to check it, a voice in Spanish came up... must be the weather, or maybe global warming?
Allan
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