[1000mp] Hum on phonepatch input-FT-1000MP

[Jim W7RY]

I just hooked mine up for a contest voice recorder to use with my Writelog 
contest logging recorder.

Here is what I ended up with.

100 ohm resistor across the output of the sound card. Then 10K ohm resistor 
in each leg. Then a Radio Shack 1:1 transformer. Then a 470 ohm resistor 
accross the output of the transformer and onto the phone patch input of the 
radio. Built it on a piece of Radio Shack perf board.

No hum. I do have a little RF getting into things when I run 1500 watts. 
Have not trouble shot it yet though.


I hope you can decipher that.

73
Jim W7RY


At 05:14 PM 11/22/2004, Ronald Walters wrote:
>The soundcard software program that I occasional run needs USB,
>it is MT63 by IZ8BLY, unfortunately my old MP does not have the CPU upgrade
>that allows for the packet mode USB but only LSB.
>
>For the record I use the packet input for all other soundcard modes and they
>work great without any hum, however if I use the phone patch input on the
>back of the MP I can hear some hum.  I am using isolation transformers for
>all inputs to and from the MP to the computer.
>
>Question?  Does anyone know if there is a load requirement for the phone
>patch input.
>
>I am using a Radio Shack 1:1 isolation transformers, any suggestions?
>Should I isolate the transformer with a cap?  Any parallel resistor network
>required?
>
>Ron W4LDE
>
>
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