Hoping I am doing something stupid but I really suspect its a faulty radion.
The power supply is a RS35M and seems to be functioning fine
However they are known to sometimes have failed capacitors that can cause hum when they get a bit older... suggest if you have a scope look at the power supply to see if it is clean...
Is the hum on receive too or only when in transmit mode?
Suggest you read my paper on "How to Build a Quiet Station"
Unfortunately things like Ethernet Cables and Computers pick up RF even when transmitting small amounts of power..
Heading to the USC / Nebraska Holiday Bowl Game Now.. GO TROJANS>.. 73's
Rich, I cant recall and cant check because I have the radio remotely on my LAN and using DAX for all the audio so I cant check. Are you getting hum during receive or just transmit?
You could disconnect everything on the rear panel except the Ethernet cable and power to see if that eliminates a possible ground loop.
Then try dropping the 63 Hz level all the way down. Check your Tx audio level on voice peaks. The meter should never go red or over the 0 dB mark. Make these adjustments with the processor/compressor OFF. Then add the compression without adjusting the Mike levels any more. Just a start. Let me know what you find.
The only thing connected to back of radio is the power, feedline and Ethernet.
I notice the noise/hum is more pronounced on the Heil 780 than the hand mic.
Noise is same into dummy load and 1/2 wave and does not change when I move the power level from left to right (full power).
It is not 60 cycle and sounds more "juhhhhhhh" .
I just ran a ground wire between PC and 6300 and picked up more noise that sounded more 60 cycle.
This forum is great !
No change in noise with power change. I using headphones and monitor to test.
Yes the downward expander takes it out but trying to find culprit of the noise.
Not running and EQ at the moment. No compressor either and noise is there even with mic level at 75 % on level meter.
Just noticed noticed noise is there with Downward expander on when I am talking but it does take it out when I am not.
Even though I got a hum report first day I am not sure I actually have that. I am going to test online shortly.
I just recorded my audio via SmartSDR even though I am not sure that is a valid test and it sound clean. I tried listening my signal on my 7800 but its hard to tell.
Very bassy for sure.
I think your seeing normal operation as far as whats displayed. What your seeing with the microphone level indicator is normal. My radio shows the same indication in receive with no microphone connected. What the meter is indicating is the "Peak" reading currently seen. which is a reading of current microphone level is "Less than -40 dBm" in other words its saying that it doesn't see a signal. I've got the 20 dBm boost enabled so in my case its indicating that it see's no signal above a -60 dBm. If the downward expander is enabled, that reading amounts to "Zero". when I disable the downward expander the peak bar fluctuates between -40 and -30 dBm with a mic connected and selected and my normal mic level setting of 75 what its hearing is the receive audio coming out of the speakers if I mute the speakers, the level drops to "Peak is less than -40 dBm" again. Record your audio and listen to it if you suspect RF or hum on your transmit audio. Hum from speakers and headphones indicates a ground loop, do you have everything grounded properly?
I am pretty sure everything is grounded well. The basic rundown is Astron supply, powerpoles on everything. No wall warts for anything. Everything with a ground lug like tuners, radios, amp, etc is ground to a bus bar on back of desk which goes to a 8' ground rod 6' outside shack. That ground rod is bonded back to dual ground rods at panel as well a UFER ground (new code thing).
So I think I am OK but I have to agree the headphones deal sounds like ground loop at this point.
One more question. If I turn on DAX I can receive though PC but have no audio control from SmartSDR at that point. Just PC soundcard control. Normal?
Jay - NO5J