WITT is full steam ahead now that everything is (apparently) working properly. However , inbetween songs, or while we fo the the mics I hear a bad hum coming through. I can the music problem, by crossfading. Any thoughts on getting rid of the hum I get whenever the music is not playing?
WITT is full steam ahead now that everything is (apparently) working properly. However , inbetween songs, or while we fo the the mics I hear a bad hum coming through. I can the music problem, by crossfading. Any thoughts on getting rid of the hum I get whenever the music is not playing?
There is an old saying which goes "it is humming because it is happy".
I have the same problem with the SSTRAN and I think it is due to ground loops in the audio feed from my sound card. A quick fix is to turn the compression control CCW (all the way if needed). This doesn't fix the problem but it will give a very nice hum free signal until you can locate the source of the hum.
If you still have a lot of hum after this adjustment, there is something seriously wrong with the audio circuit.
Neil
OK...here's an edit. After I posted this I checked the compression adjustment on my tx and found that the hum is gone regardless of the setting. I now have it about half way up and the performance is super. Low volume stuff gets boosted to high levels.
I think my hum problem fixed itself! Not really. My audio feed goes to several things and I have built a parallel RCA jack manifold. It is not in a box and I think the "hot" line was touching something nearby or I had a bad cable since I have replaced a few in the circuit. Even brand new patch cables can be bad right out of the box.
Dam, I cant spell worth a (bleep) eh?
Anyway, I think I'm not explaining myself correctly. I'm not having a hum problem while I'm broadcasting. Its only when the music is not playing. When it is playing everythings perfect, no hum at all. The problem is, when the music stops, the hum begins. This is also a problem while trying to talk without music underneath me.
Or think of it this way. How would I broadcast compleat silence?
Hi,
The way the compression works in the SSTRAN is complicated because there are several things going on at once. The processing limits the peak amplitude so the tx does not overmodulate. The compression control adjusts for low volume content by boosting the gain to keep a high modulation percentage with low audio volume..
What is happening is that the compression circuit is monitoring the audio level. When this level is low such as when the music ends the circuit boosts the gain. So if your audio is buzzing along at a certain level the gain is set accordingly and if your audio is strong the hum is reduced because the gain is reduced. When the level is low, the gain is increased and and any hum is amplified. That is why you are hearing the hum on low audio. This is signal to noise ratio. When the signal goes down, the noise doesn't and when the circuit adjusts to the lower signal it does so by boosting the gain and thus the hum.
Again, turn the compression control all the way down and you will hear the difference. When you find the source of the hum, it will work properly with the compression control turned up.
Neil
Maby once I have a proper ground system in place it would help. Right now I just use ground from the electrical outlet.
I got alot of good ideas. Problem is, most of em suck.
George Carlin (WINO)
Referring to your sig, using an electrical outlet ground might be one of those ideas that suck 🙂 If the hum is a fairly low frequency, constant hummmmmm, you might be picking up the 60 Hz of the AC wiring. The reason you only hear it when there's no music might be because the modulation section of your transmitter only modulates the hum when there's no other audio signal to work with. If the outlet ground is the source, you could remove your audio chain entrely and still get the hummmmmmm.
A good ground is hard to find, but an AC outlet ground isn't even a real RF ground option, so you won't be giving up anything if you just pull that.
A proper ground is ideal, but any true earth connection is better than what you're working with now. Metal water pipe, metal fence post, metal stair railing, a whole bunch of wire laying on the floor of the garage, all of these are far better than an outlet ground. I have soldered a short length of wire to a 36" X 1/8" solid brass hobby and craft rod (hardware store, $2.00) and drove that into the garden outside my apartment window for a great start on a ground, not ideal, but far better than an outlet. I think, strictly speaking, electrical code and all that, you're not even supposed to do that with an outlet ground...
Suggestion: Get the mixer board or the source of content as far away from the xmtr and tx antenna as possible! I had a problem with this in one of my set ups. I changed my patch cords to 20' long ones from the mixer to the xmtr to keep them rf's from getting into my input stuff..
Also, try a counterpoise ground. Take a piece of copper wire, any kind, around 8-10 ft. long and connect this to your mixer board ground. Just sting it along the baseboard of your studio room, trying to keep it as straight as possible. Listen to a dead carrier while moving the wire around and you may find that magic spot where it goes away..
I had an issue where the mic cord was acting like an antenna. When I faded my live mic in, I would get a "Hum" or a "Buzz". The counterpoise ground took care of it. Also, keep the gain of the mike on the mixer down as low as possible. Leave the mic "Hot" if this is when you hear the problem while putting the countrepoise ground wire in the studio..
"What are these rf's and how do they do that..?"