- April 14, 2009 at 11:54 pm #7262jpjanzeKeymaster
Total posts : 500
i got a talking house 2 off ebay, but did not get a power supply with it. what are the power requirements? Volts?, Current?, AC/DC?, Pos. or Neg. Tip?April 15, 2009 at 3:07 am #17248mram1500Guest
Total posts : 45366
Measured output, open circuit, is 14.3 VDC, tip positive.
Judging by the physical size of the wall wart I’d say 750 to 1000 mA.
There is no spec on the wall wart other than “Custom R.E.I. Power Supply” and the usual warning that using any other power supply voids your warranty and may damage your transmitter.
The Talking House supply has a 3 pin AC connection. The AC ground pin connects directly to the negative side of the DC connection to provide an RF ground.
I suppose you could run a separate ground to the chassi if your supply doesn’t provide that.April 15, 2009 at 7:10 pm #17249Radio JoeGuest
Total posts : 45366
On the back of the Talking house I have there is a label which reads the transmitter requires 18 Volts DC. I don’t use the power supply provided by TH for hum reasons so I use a voltage regulator and two 12 volt rechargeable 7.5 AH batteries.
I have found that if you run 12 volts on the Talking House transmitter it will at times not frequency lock and drift up a bit in frequency over time. I have not had any of those problems running 18 volts DC from my supply.
I did test to see what the rf out power did as I varied the voltage from 12V on up, and the rf out stayed constant at 100 mw after 12 volts so there is internal voltage regulation on the rf section.
14 volts should run the transmitter fine. I don’t know why they mark the transmitter at 18 volts it works fine at 13.8, but at 12 volts the frequency stability problem may occur in some models. I only had this happen on the one I’m using, a TH 4.
Here is a link: http://i425.photobucket.com/albums/pp339/JoeChezk/100_3508.jpg of the power supply I use, I have an “on board charger” for my system. When I push the on/off button located on the box below the charger, the LED goes from RED to Yellow, (to indicate charge in progress).
I have built a circuit so that when in charge mode, this will parallel the two lead acid cells so the 12 volt charger connects to them in parallel and charges them both at the same time.
The charger is a smart type which regulates the charge and goes to an “standbyl” mode when the batteries are fully charged. The batteries give me about 18 hours of run time before voltage drops below 13 volts. When in the run position, the circuit will connect the cells in series for 24 volts which is down regulated to 18 volts by the box with the volt meter on it.April 16, 2009 at 3:33 am #17250mram1500Guest
Total posts : 45366
I’m curious to know if you found it necessary to ground the case of the TH? The power supply that comes with the TH provides grounding through the AC ground pin.
I suppose you may inadvertantly ground through the audio connection. Or, maybe you are using the external antenna connection and ground through the coax.
I had a little hum on one installation where the wall wart was plugged into a UPS with surge protection. Moving the wall wart to a regular AC outlet almost completely eliminated the hum. This particular setup was using the auto tuner and inside wire antenna.April 16, 2009 at 3:10 pm #17251Radio JoeGuest
Total posts : 45366
Hello MRAM 1500 KHz!
On your grounding question, I have the case for the transmitter grounded to a cold water pipe located nearby. This is about the best ground you can get.
I use an external antenna for my set up which is outside the house. I had a lot of RF hum problems until I got the antenna outside. It’s a ten foot antenna, (or so). I use a crystal radio loop stick type coil with a variable ferrite slug for tuning the outside wire antenna. I have three picture links for you to look at.
One is a good shot of the tuner box (outside of it) and two of the complete (station) The one picture of the station which has the CB and other things in it is an older picture but shows the tuner box better, the latest picture has the equalizer and Sima SVS 4 audio switcher/ volume stabilizer but you really can’t see the antenna tuner box in that picture. I use the Sima switcher for different audio inputs and the volume stabilizer option really works out good for leveling out volume variations in sources, not to mention compressing the audio if that is what you want to do.
If you look at the picture (s), you can see the small black box on the piece of plywood mounted on the wall, on the right hand side, this box contains the antenna loop stick, and this box is my antenna tuner. That small box has the crystal radio loop stick antenna in it which I tune the outside wire antenna with.
I use a simple CB type field strength meter for tuning for maximum signal, and tune the loop stick for max output. Some loss I suppose from using a ferrite loop stick rather than an air wound coil, but it can’t be much more loss than the built in tuner, which I am not using with the outside antenna. The reason for that is the built in tuner won’t adjust fully for the outside antenna. (In my installation anyway)
I do ground both the transmitter box and the end of the coax feed at the antenna tuner box, if you look you can also see the ground on the tuner box, it is the lower black banana jack on the box.
I have found that hum can still show up in the house depending which appliance or lights in the house are on, it’s really screwy in that respect, but outside or in the car once you get away from the electrical system of the house your good to go.
I have also found that of the few Talking house units I have used, that most will not hum at all if switched to the digital message mode, but all I have tested when switched to live in, contain some low level hum. I even tried shorting out the line in or live in jack and you still get hum so must be some design problem inside. Kind of disgusting but appears to be an inherent problem. The hum is not noticeable when normal level audio is present but without audio input you can hear it. Any other questions please feel free to ask!
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