Home › Forums › temp › Hum-free, Indoor LPAM transmission – even possible? › Hello,
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I have a SSTRAN AMT-3000 and it is perfect, so don’t give up….yours will be also.
The usual cause for hum is what is called a ground loop. This translates to having more than one ground in the system. I am a bit surprised that you have a hum problem with only a wire antenna. There is the possibility that something is wrong with the power supply to your transmitter, or something is not right with the wiring on your board, but there are simpler things to try first before tearing into your unit. Try what was suggested about unplugging the audio and report back here.
Also, start with all front panel controls set to counter clockwise positions. Is the signal clean?
In my experience, if the “compression” control is set too high, you will get hum.
I think your problem is that the front panel controls are not set right. Try it with the “modulation” and “compression” pots set CCW and work only with the “gain” control. Let us know what you find.
I also have some antique radios and it is possible that your signal is just overloading the receivers. Their AGCs are not the best. Does your transmitter signal sound OK on a modern receiver?
If you try these tests and post what you find, I and others here can probably help you.