[ARC5] T22 transmitter

[Mark K3MSB]

I also use an variable capacitor and 4:1 UNUN.  Works very well into 50 ohm
coax.

73 Mark K3MSB

On Fri, Feb 7, 2020, 10:56 AM J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:

> The ARC-5 transmitters were originally designed to load into "short
> antennas" which are low impedance and capacitive.
>
> The spec was 5 to 12 ohms resistance with capacitive reactance of up to
> around 500 ohms, which was to be "tuned out" with the roller inductor.
>
> Here is the absolute min/max spec :
>
> [image: Inline image]
>
>
> As Dave says, You can't just hook it up to a 50 ohm cable.
> For the 40 meter transmitter, I use the the 50pf vacuum cap in the antenna
> switch in series with the antenna connection.
> I also use a 4:1 unun with the lo Z side on the antenna termininal. As
> long as the impedance presented by the cable is around 50 ohms or less. (
> antenna less than quarter wave high) . It would be better if I used a 9:1,
> but haven't got around to it, because sometimes the antenna impedance I use
> may be greater than 50 ohms which puts it "out of range".
>
> Your mileage may vary...
>
> On Friday, February 7, 2020, 7:42:17 AM EST, 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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