Have a look at the Ailtech 757 where he first mixer is an HP comb generator driven beyond its normal specs.
On Sunday, December 15, 2019, 5:33:12 PM GMT+1, Staffan <testjarfalla63@...> wrote:
Hello,
I'm working on fixing a VNA with a comb mixer (input 360 - 540 MHz) as the first stage, covering 270 MHz - 20 GHz (sic). It seems the driver amp was off tuning and only output approximately 22-23 dBm at best.
Finding out that it was the driver was the tricky thing, retuning it was maybe too simple. It now outputs 30-31 dBm over most of the range and the question is: can this power level be too high for the mixer input? I see no simple way of controlling output power.?
The schematics of the PA (output stage) is fairly similar to the amp in the comb generator of the 8569A (schematics A42).
The reason for the question to be off topic is that the driver sits in a Wiltron 37247A VNA...
I will ask in the Wiltron group also, but have hope that someone here may be able to tell whether this _type_ of mixers typically handle these levels or if I should (how?) reduce the output level. Any hints are very much appreciated. I - unfortunately - have no HP VNA so I don't know where to look, but guess instruments from the 80s and 90s generally were built this way? Anyone knows an HP unit that may have the same type of mixer and if so, its input drive level?
I'm keen on installing the amp, but would hate to destroy the following mixer just because I was too quick on testing...
In my world one watt is very high power. Googling SRD mixers indicate that these are OK levels, but perhaps in the upper range?
Again, any comments welcome!
Regards,
? Staffan
