[ARC5] Fw: Model 19 MKll

Tue Feb 23 04:56:03 EST 2010

Good questions, Henry.  I will try to answer them and also pass along some
other details on the setup to satisfy your curiosity.

With a cathode keyed PA the forward transfer of oscillator energy through
the tube inter-electrode capacitance into the output tank (which is a bad
impedance match to this leaking signal) is normally rather low and in my
particular situation measured well within acceptable FCC limits.

As for the adjusting for the difference in frequency between receive and
transmit, I use a spotting switch.  The spotting switch keys the PA while
simultaneously switching the output power from antenna to a dummy load.  As
long as the antenna is close to 50 ohms (which it is in my case because I
use a tuner), the spotting frequency is very close to the actual transmit
frequency.  The actual frequency shift in my setup is closer to 2.5KHz when
fully loaded to 50W plate input (for 30W output) and that is far enough away
from the receiver passband to make the backwave inaudible during receive
periods. Full voltage regulation of osc, PA screen and PA plate allows the
frequency pulling to take place so quickly this "chirp" is inaudible.  I
have also asked a nearby ham to listen closely for the FM sidebands the
pulling creates and these effects are also inaudible.  But what IS audible
are key clicks.   The clicks were cleaned up by simply using a little
shaping on the high voltage keying transistor switch that interfaces my
straight key or paddle to the PA cathode potential.  Finally, I needed some
simple filtering of the power lines and keying line to keep harmonic energy
within the box.  BTW these mods are not intrusive, are reversible, and were
implemented on a rig that had already undergone the standard ham conversion
by a previous owner.

I have used this T-22 with a dipole on a regular basis over several years
for DX'ing and contesting as well as casual operation.  A foot-switch
actuated T/R relay provides the rapid timing control needed for contesting
and chasing DX.  It was a lot of fun on 40M this past weekend during the
ARRL DX Contest.

Dennis AE6C

On Tue, Feb 23, 2010 at 1:10 AM, Henry Mei'l's <meils at get2net.dk> wrote:

> Dennis
> Is your transmitting freq 2 kHz off your receiving freq.? -- How do you
> adjust for the difference when you go from receive to transmit anf how do
> you know that your not sending a backwavce 2 kHz away from your key-down
> freq. ?
> Henry -OZ1UF
>
> ----- Original Message -----
> From: "Dennis Monticelli" <dennis.monticelli at gmail.com>
> To: "Discussion of AN/ARC-5 military radio equipment."
> <arc5 at mailman.qth.net>
> Sent: Tuesday, February 23, 2010 9:16 AM
> Subject: Re: [ARC5] Fw: Model 19 MKll
>
>
> > With my T-22 the continuously running oscillator (it runs during receive
> > periods as well) does not create a backwave issue because the PA pulls
> the
> > osc about 2KHz upon key down.  Regulation of all voltages eliminates
> > chirp.
> >
> > Dennis AE6C
> >
> > On Mon, Feb 22, 2010 at 11:17 PM, Henry Mei'l's <meils at get2net.dk>
> wrote:
> >
> >> Hi Meyer and everyone else
> >> I used the method of running the a keying (T/R) relay in series with the
> >> 1625 cathodes of my ARC-5 xmtrs back in the 50's. It does gives you
> >> cathode
> >> bias-but you do lose some power because of the voltage drop, depending
> on
> >> the relay coil resistance- I suppose you could have a pair of contacts
> >> that
> >> short out the relay coil when it kicks in- wonder what that would do to
> >> the
> >> signal (a kind of burp?).
> >>
> >> Of course, with the oscillator running, you wont be able to work QSK and
> >> you
> >> probably will have a readable backwave -- I do when keying the cathodes
> >> of
> >> my TCS final, with oscillator and multiplier stage unkeyed -- same with
> >> the
> >> ARC-5's  I keyed that way.
> >> You all are probably  aware of all this-- so call it nostalgia.
> >>
> >> 73s, Henry
> >>
> >> ----- Original Message -----
> >> From: "Meyer Gottesman" <wrecktech at yahoo.com>
> >> To: "Discussion of AN/ARC-5 military radio equipment."
> >> <arc5 at mailman.qth.net>
> >> Sent: Tuesday, February 23, 2010 12:52 AM
> >> Subject: Re: [ARC5] Fw: Model 19 MKll
> >>
> >>
> >> I stripped the usesless UHF out of my WS 19 also. The 80 and 40 CW
> >> performance is FB. As said before, the only nasty element is the CW
> >> keying
> >> being at +275 volts. The R/T relay can become the 807 cathode resistor.
> >> If
> >> the VFO runs all the time when transmitting and ONLY the 807 cathode is
> >> keyed, there should be little or no chirp and I do not recall the drift
> >> being too bad.
> >>
> >> 73,
> >>
> >> Meyer Gottesman, W6GIV
> >> Macon, GA
> >>
> >>
> >>
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