So, a little testing was done. I think I need to do some alterations to get this thing in spec.
I had a play with a simple trimpot from Vcc to the invert input, but it severely reduced the sensitivity. The best I could get was about 765MHz to 2430MHz. I think there's some magic in the ... I'll have to figure it out (Unless anyone has some insights?)
I also used the tracking generator on my Siglent VNA that is good to 3.2GHz as a function generator to test the input sensitivity without the trimpot or any input bias. (Set VNA span to 0 and the center frequency becomes your frequency output setting).
I hooked it all up with my E4418B power meter and 8481A power sensor to see what dBm level the counter display became unstable and made this graph:
I'm thinking that I might need to add in a third stage of amplification to boost the signal to the prescaler at the higher frequencies (I think the prescaler gets a bit deaf up there)?
Unfortunately the highest bandwidth scope I have is a TDS794D at 2GHz, so it's a little hard to scope the input to the prescaler directly to see what's going on. Any ideas on how to see the signal level there?
Jared
Jared Cabot