Thanks Steve. I'm not sure how a watt meter is more useful than a vna in
this instance. If the vna is showing me a good match the watt meter will
agree. If the watt meter shows no power going in, it will not tell me
anything above it. With a vna at least I know the direction to go to, how
far I am and do on.
Having said that I do have a Bird watt meter, but it has so239 plugs so I
didn't really consider it aporopriate when I'm trying to get best swr match
possible (not so much the plugs themselves but the short leads with even
more pl259/so239 plugs. I'd have to use to connect to sma). It'd be: a sma
to so239 adapter -> pl259 to pl259 cable -> so239 input of bird wattmeter -
so239 output -> pl259 to pl259 cable and finally so239 to sma adapter. I
though this would be completely pointless at 70cm. That entire stack would
probably have swr of 3 by itself.
As for other meters I have pretty good hp power meters with probes from
-20dBm down to -75dBm (nothing higher though). Whenever I need to measure
high power I just put few high power attenuators together and use my hp
meter with -20dBm to 15dBm probe. I also have a directional splitter and an
rf probe so I guess could hook up both meters and see both power going in
and out.... But I'm not seeing the point at the moment .
I spent entire day messing with components. Trying different coax lengst
including too long ones and too short. Moving this or that cap half an inch
left or right. Adding 1.2pF here or there. I can get great swr at 460mhz. I
can get very good swr at 390Mhz. But for some bloody reason it is hard as
hell to make it work I between on 435mhz. And when I finally did manage to
get 1.9swr it was so narrow it was 4 by the time I went to 430mhz.
So, yes, a bit more difficult than expected. I though "hey, as I'm waiting
for replacement transistors let's build this kit that's supposed to work
immediately (and go back to my 1w amps tomorrow). 3 days later I'm still
troubleshooting the kit amp.... I guess I underestimated the challenge. No
surprise there are a total of three people on the Internet that can
actually show one working.
73, Lukasz
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|