There was a topic started 'over there' by wdcx about the Talking House power supply, but I thought it was apropos enough to continue over here (considering that Mighty1650 asked a question which has yet to be answered).
The Talking House power supply is prone to hum, as it is grounded to the electrical outlet to which it is plugged in. Computers and other electrically noisy devices, if they are on the same circuit, are usually the cause. John asked if it could be because the device (and power supply) is rated at 18 volts. I have tried running the TH on 12 volts, and it does work (how well in terms of range, I never measured); I also noted no increase or decrease in hum.
To eliminate the hum generated by noise, you can usually experiment and try plugging in the wall wart to other outlets on different circuits, but sometimes an entire room (i.e., your studio, with all its devices) is covered by a single circuit.
You CAN ground the Talking House by other means. Someone 'over there' states, it would then not be 'complaint', which is NOT necessarily true. You would be potentially voiding the certification, but really, all the certification means is that the transmitter can be sold in the U.S. You as the operator are still responsible for ensuring that it is 'complaint' (compliant) with Part 15.
Probably the best way to do that would be to run a short ground wire from the chassis to a good ground - the antenna + feedline (none if you are using the wire antenna) + ground wire has to be at most 3 meters in length (regardless of what that length was when the Talking House was certified - the antenna + the length of the ground wire in the power lead is probably greater than 3 meters even in its certified state, and heaven forbid if you plug in an extension cord or power bar).
Hum can also be generated in the audio feed, so I always use a ground isolator. And if you do ground the transmitter by the chassis, you can use a better quality power supply that is better filtered. You can also thread torroids over the power lead (no matter what you use), and it does make a difference.
Thanks for the comments Artisan. I have experimented with a TenTec switched mode power supply that I use for my ham radio gear. The output is 13.8 regulated. Barely audible noise.
Hi Guys: I have the Talking house Ver. 5.0 & the I.A.M. Radio Tx.
1) Sometimes chaging location will get rid of the hum.
2) Sometimes moving power cord around will sometime get rid of hum.
3) Sometime doing changes, doesn't work at all.
4) I went from 3 to 2 pronge input and it reduce hum a little, But hum was still there.
I have tried these with my 2 transmitters.
Power supply insides.
I have taken taken the power supply appart and this is what i found inside.
1) The input side is well built.
2) The output is poorly designed.
a) It has only 4 diodes, 2 toroids and that's it !
b) 1st toroid has 2 seperate windings on 1 toroid core.(Wrap on Round Core )
c) 2nd toroid has a couple of wraps before exits out of power supply
( wraped on rectangle core ).
Another issue i found on my power supply was that the ground wire was sheared off.
So need to check the ground with a meter one end of the 3 prong ( round ) to end of power supply cord ( outside ring ).
If Broken you will need a small deep nut driver to take apart, Keeping the back to you then look for a brown wire you will see go from front to back of power supply on right hand side,that's your ground wire.
As for power supply tx input voltage goes, It goes to a voltage regulated transistor inside tx and it it regulated out to the circuit inside.
NOTE: Allot of the voltage regulated transistors will take a wide input voltage and reduce the ouput voltage to 1 steady output voltage to circuit.
In my own opion you should use a well regulated power supply.
Hope this helps
Station 8
Thats some fascinating insight on the TH Powersupply's guts Station8.
Thank you for the grounding information. On a Side note, I seem to recall the TH PS likes to spark on chassis contact.
It makes me nervous floating enclosures and circuitry so I use a different method. In my "high efficiency" solid state transmitters the RF output to the antenna is not referenced to power or circuit ground. This is done by using a RF toroid transformer to drive the antenna system. This allows a different ground (radials) to be used for the RF separate from the power/audio grounds.
I recently added a link coil coupling to my "vacuum state" transmitter for this same reason. With both designs the hum is greatly reduced and is not audible outside my house. Inside the house there are hum hot spots as I move around, generally near power wiring in the walls and near wall warts. It does appear that isolating the RF return from the antenna system breaks RF ground loops and reduces hum. It is not difficult to move the receiver a bit while indoors to find a spot with no hum at all.
Neil
While looking up iAM and Talking House transmitter on youtube I did see where someone used a 3 prong to 2 prong adapter and claimed their range was double what it was with the third prong in tact. It makes me wonder how this happened but if it helps hum too it could have a good use. Also Station8 and I are working as a team and when he has his prototype ATU/Antenna system done this could be something to check as he has had audio issues in his house due to the junk that the power company in his area puts out. I do know he has told me some computers will wreck havoc on he Audio section of the Talking House or iAM transmitter. He suggested to me to try and clear up the audio to move it away from the computer. You may need to get a longer patch cord. Let me know your results guys.
Also saw on a site about hum in this transmitter.....at the audio in jack, find the trace on the board that is ground. Open the trace with an exacto-knife and bridge the open line with a .5uH inductor(if I remember correctly), by exposing a little of the copper on each side of the open part and soldering it there. This has worked too. But some of the hum is caused by the A/C wiring around you indoors.
Mark
Best way to get rid of the hum is have an outside antenna fed by coax from the transmitter. The hum we hear in my findings is usually caused by inside the house wiring modulating on the RF. Turn on or off an appliance here or there in the house and hum changes. This can change from day to day on what you do or dont do to cause or get rid of the hum. I realize it can be the power supply but even when I run off a battery for testing for hum I would get hum. I did an experiment once (wire antenna in attic) I ran off batteries and pullled the main breaker to the breaker box so no power in the house and NO HUM, you energize the house and you got hum again depending on what is turned on or off in the house. Running an outside antenna helps a lot too, but the same thing but to a lesser degree can happen with hum there if your near power lines. Thats all I know about it.
Radio Joe
I connected to a TenTec Ham radio supply. No hum.