Hey everyone
I recently bought the I AM Outdoor unit. The new one with the white box and the junction box. It came with 75 feet of cat 5 cable. When I got it home I turned it on inside just to make sure everything worked and it sounded great! There was no hum in it and sound was good for that transmitter. I then started putting my transmitter at the location I wanted on the side of the house. I ended up using most of that Cat 5 cable,I am wondering if this could be the cause of the hum? It is stretched the majority of the way. Also I havent hooked it to a good ground yet. This may also be the cause? I do have a wire running from the little lug on the bottom of the box to a nearby faucet right now, until I can get some time to work with it. The noise just frustates me. I am just wanting some other answers to make sure I am not missing something. Any suggestions or help. Thanks everyone. I do not like hum and I would think with it being grounded in the box it should not have this issue??
Aside from poor power supplies, I've found that most hum conditions occur due to issues in the audio - you could try getting a ground isolator and see if that helps.
TH's are unbalanced audio. that long of an unbalanced run close to even a 100mW am transmitter with a short radiator is going to cause hum. poor grounding is also likely an issue
best cure i can offer is a henry matchbox at the transmitter end and running balanced all the way to the match box with a short run of unbalnced.
also a really good ground with a ground plane under it will help things.
Yeah, I know humming on your station is no good. I do my station on FM(Canada) but have the same thing. The wallwarts used to power these are the main cause of this. I found the switching ones used for laptops(block style) work best. The wholehouse transmitter works with a USB charger type 5 volt adaptor and some are better than others. Still have to use some ferrite clamps on the power cord and audio line in cord. The laptop style blocks come in voltages close to the 18Volts used by the TH transmitter. If those suggestions don't work you can get a much better power supply...not a wallwart but a "real" power supply from an electronics component store or online. If you powered the TH from three 6 volt lantern batteries you would have no hum which proves that not properly filtered 60HZ A/C is the culptit.
Mark
First identify the audio frequency of the hum. If it's a 60Hz AC hum, then it's likely disparities between the audio ground, the transmitter chassis ground, and/or the faucet. I'd remove the TX faucet ground first because, assuming a single faucet, you may have connected the transmitter chassis ground to both hot (goes to the water heater which likely has it's own ground) and cold pipes, or the pipes may be PVC somewhere in line, in which case of course there is no ground at all. If you want to ground the chassis to a pipe, it must be only the cold water, preferably where it enters the house, and it must be metal all the way under the ground.
Another method might be to connect it to a ground rod or grid which serves the house electric or, even better, its own ground rod, at least 8' or more deep.
If the power supply is not properly filtered it can generate hum, but not necessarily at 60 Hz.
There is no such thing as a perfect ground...there is almost always a leak somewhere, hopefully negligable. If the audio common ground is from a sound source which is plugged into a different outlet than the TX, it could create a disparity causing a potential, i.e., flow across the chassis, often a source of hum.
Others have brought up bal/unbal situation, correctly assigning the possibility of hum to the susceptability of unbalanced line. However, it seems the unit may be getting both power and audio through twisted pairs of ethernet cable which is (or should be) balanced, a fairly common practice in home entertainment systems today, but in this case it should be SHIELDED (the thicker stranded wires), not the unshielded thinner cable used to lay built in in-wall ethernet sockets.
If I truly had my 'druthers I would like to carry my audio in digital optical cable, which is not vulnerable to EMI, but in lieu of that, I'll likely use industrial grade ethernet cable (Cat 7A...with the outer yellow jacket) for both power supply and audio...each of the twisted pairs have their own separate shield, plus the whole cable is also shielded...very stable and tough enough...but kinda pricey.
HTH...
I have a hum right now that I've identified as coming from a switching power supply which powers a wi-fi audio receiver that provides the audio for the AMT5000 transmitter.
After ruling out the DC power connection and the audio line, it turns out the switching supply is injecting a buzz straight into the household AC wiring.
I'm going to loop the AC cord a few times through a toroid in hopes of reducing the hum.
An interesting observation is that the hum only appears on radios oriented in a certain direction; if the radio is turned 45-degrees, the hum disappears. Therefore it seems to have its own polar angle.
Outside the building the buzz is not heard at all on the radio station, which tells us that it is not modulating the carrier.
I too have encountered hum in the studio that isn't being broadcast out very far. I.e., close in, the radios are picking it up from house wiring independent of the broadcast signal.
Also, I called the power company because I've recently detected significantly more noise on the power lines than there was a couple of years ago. I think the data being sent on the power lines is much more, and wider band, and at least responsible for some of it ('leaking' out), if not the total culprit. Has anyone else noticed this in your respective areas?