[Milsurplus] Re: TA2J High Power Tx in Catalina

[Hue Miller]

----- Original Message ----- 
From: "Mike Hanz" <AAF-Radio-1@cox.net>

> >I ask, does it use simply a tapped coil as the output, like the BC-230
> >or the GF, for example?
> >
> 
> Well, in a way.  It has eight detachable roller coils similar to those 
> in a command transmitter, but with *two* roller taps (plus a grounded 
> end.)  One tap is for feeding the output of the 803 PA plate into the 
> inductor (through a .004uF coupling cap), and the other tap feeds the 
> antenna.  B+ is fed through the RF choke seen at the top in the "left 
> interior view."  Through a procedure that is too convoluted to quote 
> here, you fiddle with the two rollers to match the antenna (which must 
> be at *least* 250pF to resonate.)  You can also strap a 100pF fixed 
> shunt cap into the circuit for certain conditions.  For series 
> capacitance (above 7.5MHz) you need to buy the "Type MT-36C Series 
> Antenna Loading Unit," which may have been a clever marketing ploy to 
> get you to spend more money at Bendix.  It's a unit the same size as the 
> TA-2J!

Then it uses the same primitive harmonic-prone circuit as much earlier
transmitters, yes? Do you have any comment on the actual harmonic
levels to be expected? I 'believe' the situation is only really bad when
using a high impedance antenna, one that is tapped well up on the
coil, and the antenna also happens to be high impedance resonant
at some odd harmonic.

> >Also- Mike or anyone else - the RDF-1, the HF predecessor to the DU,
> >which tuned to 8000 kcs. - do you have any idea how far down the
> >reception with it would be, from a standard wire antenna of say, 30 ft. ?
> >I mean in the B position, receiving totally on the loop alone, say on
> >80 or 40 ?
> >
> 
> Sure!  Just as soon as you define what "how far down"; "reception with 
> it"; and associated receiver actually means. <grin>  I have no clue what 
> you are talking about in technical terms.

I meant, when receiving solely on the loop, i.e. "B" "bearing" function, as
compared to receiving solely on a fixed wire antenna, how many S or db
down might you expect the reception to be. As i recall, there is only enuff
gain in the one-triode amplifier to compensate for capacitive shunt loss in
the coax to the receiver, per the Navy manual.
Hue