[ARC5] Fw: Model 19 MKll

Tue Feb 23 23:13:53 EST 2010

If your feed-through signal is 50dB down that's doing well.  Spurs and
harmonics should also be at least 50dB down.

I use all the regulation techniques you mentioned, Henry.

The Osc is regulated by two stacked 105V reg tubes. The PA Screen is
regulated by stacking a zener on top of the regulator tube stack and then
buffering with a single transistor.  The PA Plate uses a homebrew transistor
feedback regulator because a triode pass device wouldn't fit on the chassis
as a retrofit.

Dennis

On Tue, Feb 23, 2010 at 3:12 AM, Henry Mei'l's <meils at get2net.dk> wrote:

> OK Dennis
> You're right about the poor match-capacity path  between osc and PA BUT
> I've
> been told in several QSOs that my backwave was quite readable
> though never told how many S-units or dB down. Do you use VR tubes, zeners
> on all B+ voltages and or a triode regulator for the plates?
> I also use a foot switch when I operate with my TCS - when not in QSK mode.
> Thanks for the info.
> Henry
>
> ----- 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 10:56 AM
> Subject: Re: [ARC5] Fw: Model 19 MKll
>
>
> > 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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