[ARC5] Re: Power supply for chirp-free op

Sat Sep 29 15:17:20 EDT 2007

I have a T-19 and T-22 on a twin rack with the MD-7, completely unmodified 
and it performs very well, I have phone contacts as far as Holland and CW 
into USSR using a 16foot antenna strung from the top of the RE-2 to the top 
of the bathroom door across the hallway from the shack. QTH is south coast 
of the UK. no appreciable chirps but just enough to give a nice 
characteristic, something of which is lost with modern radio, it does get 
you noticed and running near QRP you need that sometimes. Personally I like 
the little bit of chirp these give and certainly adds a talking point. I run 
these from a 28volts supply from two boat batteries and a regulated charger, 
I use good fat low volts feed wire to the power supply modulator, this is 
where most problems start by losing the power before it gets there in most 
installations. I screened the cables from the MD-7 to the transmit rack and 
that stopped any problems there. Just check out the capacitances and 
resistors in the MD-7 just to make sure they are not too wild, some of these 
components can be 10 times wide of what they originally were esp caps; once 
they dry out they lose their capacity badly, resistors also tend to go high 
or o/c. (bad caps can cause bad chirps). When the sunspots get better I am 
sure trans-Atlantic QSO's will happen again, I have some old '50's QSL cards 
from a SK that have BC-459's etc on the transmit gear and 'gd copy' 
'Stateside!, 73 Max M0GHQ
----- Original Message ----- 
From: <arc5-request at mailman.qth.net>
To: <arc5 at mailman.qth.net>
Sent: Saturday, September 29, 2007 7:16 PM
Subject: ARC5 Digest, Vol 44, Issue 27


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> Today's Topics:
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>   1. Re: Power supply for chirp-free op. ? (Mike Morrow)
>   2. Re: Power supply for chirp-free op. ? (Dennis Monticelli)
>   3. Re: Power supply for chirp-free op. ?
>      (Unserviceable but Repairable)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 29 Sep 2007 11:12:24 -0500 (GMT-05:00)
> From: Mike Morrow <kk5f at earthlink.net>
> Subject: Re: [ARC5] Power supply for chirp-free op. ?
> To: arc5 at mailman.qth.net
> Message-ID:
> <17581230.1191082344998.JavaMail.root at elwamui-rustique.atl.sa.earthlink.net>
>
> Content-Type: text/plain; charset=UTF-8
>
> 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
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 29 Sep 2007 09:54:12 -0700
> From: "Dennis Monticelli" <dennis.monticelli at gmail.com>
> Subject: Re: [ARC5] Power supply for chirp-free op. ?
> To: "Mike Morrow" <kk5f at arrl.net>
> Cc: arc5 at mailman.qth.net
> Message-ID:
> <2e972efa0709290954r6f278df8qe22bef997b06dff1 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> 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
>> _______________________________________________
>> ARC5 mailing list
>> ARC5 at mailman.qth.net
>> http://mailman.qth.net/mailman/listinfo/arc5
>>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 29 Sep 2007 14:11:24 -0400 (EDT)
> From: Unserviceable but Repairable <cosmoline at aa4rm.ba-watch.org>
> Subject: Re: [ARC5] Power supply for chirp-free op. ?
> To: dougforbes at dslextreme.com, jfor at quik.com
> Cc: arc5 at mailman.qth.net
> Message-ID: <200709291811.l8TIBOLO012029 at fracas.netboobie.org>
>
> Yo Doug
>
> Gyro Gearloose wrote:
>
>>...blah...This is to create a series resonant circuit with the 
>>roll-a-ductor
>>....
>
> This doean't check out
>
> Doug you need a series capacitor OK, prolly 150pf on 40.  It's to
> tune out the link's inductive reactance
>
> The roller inductor has to be twisted back to the left side, i.e.
> zero inductance.  Read out of circuit
>
> In gi service, the antenna began at the output lug and, since it's 
> fuselage-
> perpendicular component was real short, it looked capacitive & hence the
> needed series inductance - like the whip base-loads in HF mobile
>
> Any old way, put a 50 ohm dummy between that 150 pf variable & ground
> & twist the variable & the '459 link control 'til you get power
> you & the p-s allow
>
> 1946-9 handbooks all contained the method & basis since so many link-
> coupled OT & surplus tx-s began running w. coax.
>
> Apparrently not covered in Ken Burns' latest though
>
>   Marty
>
> PS There's whopping 22V across that dummy R @ 50w.  Perhaps scary
>    to OSHA & Gyro
>
> PPS: that little relay wasn't meant for keying, rather B+ "bus select"
>     so only that TX was getting the juice.  Same went for the "rocker
>     arm" antenna relay - antenna "bus select"
>
>     B+ was relay-keyed back in BC-456/MD7 modurator.
>
>     Just hook rig back up & see how she sounds... mebbbe letting
>     1626 run continuously & keying the 1625 cathodes
>
>     Let the flames begin
>
>
> ------------------------------
>
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> End of ARC5 Digest, Vol 44, Issue 27
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