[ARC5] Power supply for chirp-free op. ?

[Dennis Monticelli]

I use a T-22 on 40M regularly and chirp management is largely a
function of supply regulation.  The osc voltage is easily regulated
via a VR tube and this is step 1.  The next step would be to regulate
the screens of the 1625, again a VR tube stack suffices.  The final
step (a lot of work and usually unnecessary) is to regulate the HV.
One by one, I added all this regulation, but left switches to defeat
HV/Screen regulation when I wanted the orginal character of the signal
to come through :-)

I forgot to mention that my relays were also missing when I acquired
the modified T-22.  I ended up allowing the osc to run continuously
and then key the cathodes of the PA.

The series cap trick worked well enough for loading, but take note of
where you place it.   It needs to go directly at the output connector
and not on the other side of the roller inductor.  If you place it on
that other side, the roller inductor's parasitic capacitance to ground
will alter the impedance at the very high impedance node defined by
the series resonant circuit you are trying to create.  It will load up
better if you place the cap in series right at the connector.  50pF is
not critical; nything from 50 to 100pF will work.  Use a good HV
transmitting cap.

There are other output configurations that could be used without undue
modifications, but the series cap is simple and effective.

Have fun.  Maybe I will hear you on the air.  ARC-5 to ARC-5 QSO's are special.

Denny AE6C

On 9/29/07, Mike Morrow <kk5f at earthlink.net> wrote:
> Doug wrote:
>
> >If you folks know of a way of getting chirp-free operation without the relay
> >as well as a way to use the unit without a tuner into a 50 ohm load that
> >info would be helpful as well.
>
> Doug,
>
> This relay has nothing to do with chirp when the transmitter is used *as intended* by the set designers.  This relay and the antenna connect relay are transmitter select relays that are energized continuously as long as the transmitter is selected for use on the control box (i.e., transmitter in rack position one is selected when the control box's selector switch is at the number one position).  They do not cycle as the mic PTT or Morse key is cycled.  The original design keys the HV supplies to the transmitter with a HV keying relay in the modulator unit.
>
> Keying a command transmitter with the relays in the transmitter is a ham innovation which is outside the intended function of the original design.  You could make your unit function in the original manner by wiring the circuits (PA cathodes and oscillator HV) as if the (missing) relay were energized, then key the HV inputs to the transmitter with an external relay.
>
> I find it very interesting when this historic equipment is operated today as near as possible to the same manner as it was in original service.
>
> Mike / KK5F
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