Wanted: Talking House ATU

Not to disappoint, but I've been looking for a used TH ATU as well ... for over a year. I hope you can find one.

Maybe, a better request would be for the schematics of the tuning network for the TH transmitters. This would allow those of us with electronic backgrounds to scope out the circuit to build a similar device and a list of components needed to complete the project. A picture is worth a thousand words; the schematic diagram.

Even a person who owns one of the boxes could draw a diagram from the inner workings and get you close to what you need. Or maybe, someone here could take a few pictures of the innards of the device so that the schematics could be produced and possibly a working prototype. Just a few suggestions.

The schematic for the ATU has been posted here or at least a link to it.

I've looked inside mine and it uses the same tuning method as the TH transmitter, minus the drive motor plus a bandswitch and meter circuit.

Looks like it would not be to difficult to build one. The easiest way might be to buy a junk TH transmitter and remove the tuning assembly. Then build the peaking meter circuit and stick it all in a box.

Well, sure, I suppose if you're circuit-savvy, that could certainly be done, but since it isn't the part number for the TH, then I'd bet using it would blow the FCC Part 15 certification.

The ATU simply provides a means to properly tune the external antenna to the transmitter, nothing more. The ATU does not produce the 100mW signal, the transmitter does. The ATU cannot increase the 100mW RF signal at all, though it can affect how effectively that 100mW RF signal transfers to the piece of wire. If anything...and in worse case scenario..the ATU can seriously dampen the energy transfer efficiency to a point where even that pre-set 100mW signal is shunted down to nothing.

The ATU can also perform a 2nd task..and that is to keep that piece of wire resonating at the operating frequency thereby keeping spurious down to the required specs at the measuring point away from the radiator or at the ATU's output connector.

I do not believe that adding an ATU designed for those types of transmitters that later models or earlier models did not include would change anything regarding certification. Remember that the certification merely confirms that the unit does not throw out more signal than it should and does not throw out a spectrum full of junk or occupy too much bandwidth or drift all over the place. If anything when an inspection were to take place on such an installation, it would pass muster and probably beat its previous specs when it did not have the ATU added.

RFB

The ATU does not produce the 100mW signal, the transmitter does. The ATU cannot increase the 100mW RF signal at all, though it can affect how effectively that 100mW RF signal transfers to the piece of wire.

True, in part because there is no 100 mW RF signal. There is an RF signal of some lesser mW because the DC input power to the final RF amplifier section is limited to 100 mW. Estimates of the RF output range from 10 mW to 30 mW, depending on the efficiencies utilizing that 100 mW DC input power.

Other than that, absolutely!