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joseph2010 · October 3rd 12, 08:51 PM

Quote:

Originally Posted by Ralph Mowery

"joseph2010" wrote in message
...

I have an old Magnadyne SWR-72 for 11 meter (CB). I want to modify it
so I can use it on 2 meter (VHF).

The only frequency sensitive components I can see are a couple .001 caps
in parallel with a couple 150 ohm resistors. Can i change the meter's
frequency response by changing the RC combination in the circuit?

I would submit a photo but I don't know how to attach to this message.
Thanks in advance.

That appears to be the same as several types of SWR meters with a differant
name. Most of them were rated to go to 150 mhz. Some were in about the same
box with two meters on the box and no forward/reverse switch. I have used
one up to 220 mhz and it seemed ok for adjusting for minimum SWR. They will
not work at all at 440 mhz for swr.

The resistor is to match the internal line to the impedance. The .001 cap
is just an RF bypass. The main things that determin the frequency are the
two wires that are parallel to the wire going from the centers of the two
pl259 connectors. If too short, they will not pick up enough signal to set
the meter to full scale. If too long, they will not respond to the
direction of the forward to reverse power.

If the meter is built like that, it will probably work from 0 meters to two
meters just as it is.

Ralph, Thanks for your informative reply. You're right, there were several manufacturers that made these units (Midland, Pace, Numark, etc.). I did try to hook it up, but the SWR was 1.3:1 (almost the same as I got with a dummy load), which I thought was too good to be true, but maybe it was due to the low wattage being used (4 watts). I'll get some proper cables built and go from there. Thanks again.