[MRCA] Vibrators

[Mike Morrow]

Ken wrote:

>I have a circa 1941 RCA RVT-15A  Aircraft transmitter. 

That would actually be "AVT-15A."

>This rig is in good shape visually as well as it's matching
RVT-20-A1 receiver. 

That would actually be "AVT-20-A1."  The usual matching receiver in civil air service is the LF/MF AVR-15, a beacon band receiver, which allowed the classic 278 kc (tower)/3105 kc (aircraft) communications combo.  But the Signal Corps seems to have purchased a number of them for use with the MF/HF AVR-20-A in 6 vdc and 12 vdc versions.  The power supply in the transmitter was used to supply the receiver as well.  Most AVT-15 sets that I've seen were 6 vdc versions.

>I would love to get this set back on the air it will make a nice
>little ten watt, or so AM station.for 80 meters.

One thing to keep in mind is that the AVT-15 is a *modulated oscillator* design.  The set has only two tubes, both 6L6, one of which is the AF modulator, the other is the RF oscillator.  There is no PA stage, so changes in antenna loading and modulating the oscillator can introduce FM and frequency changes.

A slightly later transmitter that replaced the AVT-15 is the AVT-112.  It uses 6V6 tubes in a MOPA circuit, with the PA being plate modulated.  This unit is the same size as the AVR-20-A receiver, and it is a very decent design.  The only downside is that the vibrator power supply AVA-126 is external, about the same size as the transmitter.  These are found in 6, 12, and rarely 24 vdc versions.  The 12 vdc version seems most common.  The AVT-112 is much more common than the AVT-15, but it's a much better unit too.

I believe that a common USAAF light observation aircraft radio installation would consist of the RCA AVT-112 MF/HF transmitter, RCA AVR-20 MF/HF receiver, Setchel-Carlson Model 512 LF/MF beacon receiver, all supplied by a AVA-126 power supply set for 12 vdc.  

73,
Mike / KK5F