"Major Samwells" wrote in message
...
I'm trying to get some accurate power readings with a low power rig (5 W)
and an RF Ammeter. The trouble is that the ammeter doesn't read quite up
to the highest level of the transmitter and I need to reduce the power to
the meter by about half. I'm thinking a 3 dB attenuator, but how am I
going to find the oddball resistances and what about resistor wattage? Is
there any other way to reduce power to the meter? Need something simple,
quick-- but accurate. Thanks.


I'm not sure there are any simple answers to obtaining "accurate" power
readings
with an "inline" RF Ammeter. (due to variable input and output impedances
and response
of MOST RF Ammeters, and such). However it is relatively easy to increase
the
range of an RF Ammeter by shunting it (paralleling it) with a low
resistance, low
impedance resistor made from a short length of wire. (bailing wire, iron,
fence or
what have you)
The Ammeter will have a very low resistance to begin with, so a very
low resistance
homemade shunt wire resistor can be fairly short, and length determined by
quick
experimentation. Run RF through the meter and take a reading at almost (or
at) the
top end of the scale. Then temporarily jumper the meter with the homemade
shunt
and adjust it's length until the meter reads half scale (if you want to
double the meter's
range), and tighten things up. Done. At less than 5 watts you can do this
hot, with your
fingers. (assuming your final is not a tube type with plate voltage
appearing at the
antenna terminal... YIKES!!!!!
Results will definitely not be accurate, but should be repeatable for
most comparative purposes.

That's my story, and I'm sticking to it.

Old Chief Lynn, W7LTQ