[ARC5] Fw: Model 19 MKll
Henry Mei'l's
meils at get2net.dk
Tue Feb 23 06:12:02 EST 2010
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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