[ARC5] T22 transmitter

[Dennis Monticelli]

Peter,

Congrats on your pristine T-22.  It will give you much pleasure putting it
on the air and you should be able to do so with only minimally invasive
reversible changes.  The ARC5 reflector is indeed the right place and there
is tons of material to research.  I suggest you do some reading starting
with Dave Stinson's primer.

I have a T-22 and can share what I did for antenna coupling.  If you tack
270pF from the output of the variometer to ground (there is a solder
terminal right at the bottom of that coil's secondary) and then use a
series 100pF,   it will load up with the rollerductor right in the middle.
You may wish to redip the plate via the variable cap that is mechanically
lock tuned.  Of course the shunt cap will assist with reduction of the
higher order harmonics. I have a spectrum analyzer) and checked that.  It's
important to filter and/or shield the leads going in and out of the rig.  I
measured harmonics up through VHF.  I guess the WW2 flight crews were
forbidden from watching Hogan's Hero's on Ch 2 while on a mission :-)

Finally, don't apply power until you assess the quality of the HV bathtub
cap in the rear.  It is probably bad.

Dennis AE6C




On Fri, Feb 7, 2020 at 4:42 AM David Stinson <arc5 at ix.netcom.com> wrote:

> Good Morning, Peter.
> I believe the work has been done, but I don't remember where
> may have seen it.  Frankly, I consider it "over-thinking the problem."
> I've run the rigs into spectrum analysers using the series-cap
> and found them very clean.  I don't think going to a more complex
> solution will yield a meaningful improvement.
> However- "each to his own" of course.
>
> There is an active, long-standing "ARC-5" email reflector
> at arc5 at mailman.qth.net with some excellent people.
> For a broader milradio group, there are:
>
> milsurplus at mailman.qth.net
> MMRCG at groups.io
>
> GL OM ES 73 DE Dave AB5S
>
> On 2/5/2020 9:35 AM, Peter Bertini wrote:
> > Hello Dave
> >
> > Has anyone ever come up with a more precise estimate for the T22
> > transmitter antenna impedance?
> >
> > I have one that looks like it just left the factory, and I intend to
> > get it on the air using you suggestions
> > to keep it original.  It is an extremely nice black wrinkle painted
> > original,  with a lot of red factory labels.
> > I have to research its age and lineage.
> >
> > I've read the advice concerning a series cap to cancel the rotary
> > inductor and link inductance... however
> > I suspect it would also be easy to tack in two high voltage micas to
> > convert the rotary inductor into
> > a Pi matching network, which should give a better matching range and
> > better harmonic suppression.
> > The caps could be easily removed by a purist in the future without
> > affecting its value as an artifact.
> >
> > I am also looking for parts from junkers to restore several other
> > transmitters and receivers, are they any
> > groups that cater to ARC-5 fanatics?
> >
> > Any thoughts?
> >
> > Peter W1BR
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