On 10 August 2013 19:59, Brooke Clarke <[email protected]> wrote: > Hi: > > This is an interesting type of VNA where they independently change the LO > and detector DDS clocks to fill in what otherwise would be nulls thus > extending the frequency coverage. 20 minutes into the video they talk about > comparing two Rb sources. > HAMRADIO 2012 DG8SAQ VNWA UK HD (2012) > http://www.youtube.com/watch?v=C94J4AutCRc
An interesting idea, though I am a bit sceptical. At such small phases, things like changes in temperature of cables have an effect on measurements of phase on a VNA. One can measure something as simple as a short circuit, and will see some drift with temperature, yet I use expensive VNA grade cables on a VNA costing much more than the VWNA. The method assumes the only cause of a measured phase difference between the two oscillators is their frequency drift, but there are other reasons too. I sold me 300 kHz to 3 GHz VNA last week. Someone picks it up tommorow. A 10 MHz reference is too low for my 8720D, which covers 50 MHz to 20 GHz. I wonder if this would work on the inevitable harmonics present, or if one put it into something like a mixer which is non-linear. I must admit I have been tempted to buy one of the VWNAs. I see some results on an earler model, and they looked poor above about 600 MHz, when harmonics of the oscillator are used. I belive they have improved things, but in any case it would compliment my HP, so I really only need something below 50 MHz. > Brooke Clarke Dave _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
