On Thu April 6 2006 09:17 am, Dr. Gerald N. Johnson wrote:
> On Wed, 2006-04-05 at 18:27 -1000, Ken Brown wrote:
> > No reason you cannot use a good stable Ten-Tec transceiver in CW mode as
> > a VFO to have some degree of frequency agility. You're going to have to
> > work on the tank circuit a bit to get it to 160 or 75 meters anyway, so
> > why not make it tunable.
> >
> > I'm thinking an RCA BT1K. Push Pull 833s modulated by Push Pull 833s.
> > It's only a kW. Since it is a 50s vintage TX, 50's vintage ham power
> > limits should be appropriate way to maintain purity and stability to a
> > level the state of the art permits. And it will fit in a one car garage.
> >
> > DE N6KB
>
> Gates and Collins all made a pair of 833s modulated by a pair of 833s.
> More likely paralleled in the PA.
>
> 50's vintage ham limit were PA plate input power ignoring the peaks from
> modulation. A pair off 833s ought to run 1800 watts PA input to get 1 KW
> RF carrier with a peak power output of 2 KW. Today with the peak power
> output limited to 1.5 KW, its still not legal. I'm sure it can be backed
> off a bit though that wasn't type approved. It would be easier to back
> off the power of a tetrode or pentode PA by lowering the PA screen
> voltage.
>
> These rigs are all tunable from outside the box, probably hidden behind
> a door.
Jerry's comment about using a TT rig as a VFO might be worth exploring for
those who are interested in doing something like this. BTW as I recall many of
the 1KW AM transmitters had multiple primary taps on the HV power transformer
to facilitate "pre-sunrise" operation at reduced power (usually 250 or 500W)
so reducing the power to meet amateur limits might not be too hard to
accomplish.
Also, I had to think about this for a minute -- I believe Ken is mixing his
transmitter models (not that it's any big deal, just brings back memories HI
HI!!) RCA used _4-400s_ in the BTA 1R transmitter at the small-town AM
station I worked for early in my broadcast career. The _Gates_ BC-1J at the
other station in town (and the model K, if there was one as I would assume)
used 833s. There are quite a few guys putting these old transmitters on 160 &
75M AM as the following link documents:
http://www.rwonline.com/reference-room/special-report/rwf-chromeJune20.shtml
Looks like things have to a certain extent come full circle given the stories
years ago about old-timer BC chief engineers who were also hams tuning their
station's transmitter up on 160M at night after the station signed off :-)
--
73, Al
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