[Milsurplus] Milsurplus Digest, Vol 115, Issue 5

Mon Nov 4 12:39:39 EST 2013

Gord:

The only comments I have are as follows:

I would prefer Lisbon Bakery small dinner rolls to Costco's. Mainly on 
flavour.
If it would be possible to preheat the plates/soup bowls prior to 
serving as it keeps the contents warmer for a much longer period of time.

I will prepare signs and tickets and get a note in L&W as soon as Derek 
confirms the soup source and availability.

Ralph

On 11/4/2013 12:00 PM, milsurplus-request at mailman.qth.net wrote:
> Send Milsurplus mailing list submissions to
> 	milsurplus at mailman.qth.net
>
> To subscribe or unsubscribe via the World Wide Web, visit
> 	http://mailman.qth.net/mailman/listinfo/milsurplus
> or, via email, send a message with subject or body 'help' to
> 	milsurplus-request at mailman.qth.net
>
> You can reach the person managing the list at
> 	milsurplus-owner at mailman.qth.net
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of Milsurplus digest..."
>
>
> Today's Topics:
>
>     1. Re: BC-312  tuning backlash (J. Forster)
>     2. Crawfish Boil: BC-375 on 30 Back in Business (David Stinson)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 4 Nov 2013 04:49:09 -0800 (PST)
> From: "J. Forster" <jfor at quikus.com>
> To: "Hue Miller" <kargo_cult at msn.com>
> Cc: milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] BC-312  tuning backlash
> Message-ID:
> 	<22109.12.226.214.5.1383569349.squirrel at popaccts.quikus.com>
> Content-Type: text/plain;charset=iso-8859-1
>
> In the early days of surplus, after WWII, there was a lot of
> misinformation published, especially in the ham press.
>
> -John
>
> ==================
>
>
>
>
>> Many thanks to those who wrote to assure me that backlash is not
>> a universal problem with BC-312 type receivers. I wonder what
>> the 'Hints and Kinks' based their statement on. Perhaps because of
>> the H&K's early surplus-era date, 1949, they had a limited sample
>> to judge from?
>> Thanks particularly to Dennis, W7QHO, who exactly addressed the
>> issue. I repeat his comment for those on a list which may not
>> receive these posts.
>> -Hue Miller
>>
>> "Subject: Re: [Milsurplus] BC-312 tuning backlash
>>
>> No, backlash not a problem except in the earliest BC-312/342 models.
>> There is a large spring loaded gear behind the front panel that is
>> engaged by two pinions, one that is driven by the "Fast Tuning" knob
>> and the other by the "Vernier" dial.  The procedure is to back-off on
>> the engagement of the Fast Tuning pinion just past the point which
>> allows the spring loading on the large gear to become fully applied to
>> the Vernier pinion.  This is done by means of an eccentrically
>> drilled  bushing on the Fast Tuning shaft which is locked in place by
>> a hold-down collar accessible behind the front panel Fast Tuning
>> knob.  The two halves of the spring loaded gear must not be stuck
>> together, of course, and all the gears in the chain should be clean
>> and carefully lubricated.   In some cases the end loading of the
>> ganged variable tuning capacitor may have to be adjusted (adjustment
>> screw located in the oscillator compartment).
>>
>> There is a problem with very early models where the hold-down collar
>> for the Fast Tuning shaft bushing is located on the back side of the
>> front panel and is not accessible for adjustment.  I have 1938 BC-342A
>> like this.  :^(
>>
>> Dennis D.  W7QHO
>> Glendale, CA "
>>
>> ______________________________________________________________
>> Milsurplus mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Milsurplus at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Mon, 4 Nov 2013 08:07:15 -0600
> From: "David Stinson" <arc5 at ix.netcom.com>
> To: <milsurplus at mailman.qth.net>
> Subject: [Milsurplus] Crawfish Boil: BC-375 on 30 Back in Business
> Message-ID: <743B6E72A72843BB968CE641AEB73C0B at CompaqSR5710F>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> 	reply-type=original
>
> Re: BC-375 Tube Substitution
> and Keying Progress Report 11-04-2013
>
> Finally replicated the success with the BC-375 on 30 meters.
> I was going to address the drift/chirp problems separately
> from that of the tube substitution, but the two issues are linked.
>
> As you know, I had some success in making the 375 useable on
> both 40 and 30 meters. The original problem is both fast drift
> and chirp when trying to use the rig above 75 meters.
> Here is what a BC-375 with 211 tubes in "all original" mode,
> using the PE-73 dynamotor at 1000 V B+
> and with a stock TU-10 tuning drawer tuned (at first ;-) to
> 10.108 KC delivering 50 watts into a dummy load:
>
> http://home.netcom.com/~arc5/BC375/375baseline.mp3
>
> My investigation has revealed several causes for this behavior:
>
> 1. A+ Filament Buss Sag.
> The 211 Oscillator is a directly-heated filament tube.
> When the transmitter is keyed, the A+ buss will sag
> a small amount due both to the extra current drawn by the
> dynamotor and from I/R losses in the A+ supply cabling
> to the transmitter- a good reason to use the larger wire GE
> said to use there. Even a 1% drop in A+ (about a quarter of a volt)
> will create a marked frequency drift when on 7 or 10 MC.
> I proved this by tube substitutions. The 211 has a large filament
> that has a good deal of "thermal inertia." The 1625 (cathode to heater)
> has much less of this property. It will drifter further and faster
> if the A+ buss sags. The 837 tube, with a much bigger filament/
> cathode at near twice the current and thus, with more thermal inertia
> than the 1625, falls between the two, strengthening the hypothesis.
> As soon as I can fit it in the budget, I'll be ordering buck regulators
> to fix the A+ buss sag and see if this helps.
> Until these arrive,
> I'll concentrate on the other problems while using the 211s.
>
> 2. Thermal Drift
> At full 1000 VDC B+, the 70-year-old frequency-determining
> components heat-up and drift, so the oscillator drifts.
> Some of the old transmitting micas have started leaking a little
> (some a lot). When hit with 1000 volts, they heat and drift.
> Even a small amount of heating and drift at 10.1 MC will walk
> your rig right down to WWV.
> Reducing the B+ to 500 VDC cured that problem.
> The BC-375 uses a floating B- supply, keying by grounding
> part of the grid resistor, thus removing cut-off bias from the tubes.
> Here is a simplified diagram of 375 keying:
>
> http://home.netcom.com/~arc5/BC375/375keying.jpg
>
> I pulled the fuses on the PE-73, lifted the B- brush on
> a DY-8/ARC-5 transmitter dynamotor
> and jumpered it into the circuit box of the PE-73.
> This worked a treat. Here is the BC-375 on 10.108 KC,
> delivering 20 watts to a dummy load,
> using the 211s and 500 VDC B+.
> Chirp was still a problem, but
> there's no longer any chance of QRMing WWV.
> Note that the clicking noise you hear is not "key clicks,"
> but the keying relay.
> Note that the frequency jumps you hear are a Hi-Z intermit in the
> keying relay I haven't yet addressed, so please try to ignore them::
>
> http://home.netcom.com/~arc5/BC375/375origkeying.mp3
>
> 3. Keying Sequence.
> When adjusted according to the GE 375 manual procedure,
> the keying relay brings-up the transmitter first, then connects
> the antenna. This is a certain recipe for chirp.
> The GE engineers were smart men- they had to know this.
> Was it done this way to make the 375 easier to pick-out in
> a noisy receiver? Who knows? I thought about re-adjusting
> the relay to attach the load *before* turning-on the transmitter.
> But that would be assuming I know more than the engineers
> and I don't. Whacks and hacks are verbotten, so what to do?
> The solution was to use the original keying line as a "transmit"
> switch and key the B- lead, similar to what is done
> with an ARC-5 transmitter. While there is still some
> residual chirp, I think you'll like what you hear from
> this this BC-375 on 10.108 KC, 211 tubes, 500 VDC B+
> keyed via the B- lead, delivering 20 watts to a dummy load.
> No keying shaping or spark suppression were used for this test
> (will work on that):
>
> http://home.netcom.com/~arc5/BC375/375biaskey.mp3
>
> No; it's not "break-in keying," but come one, guys-
> are you really talking about running a traffic net with a BC-375?
> "Can't have everything" ;-)
>
> So a 500-600 VDC supply (the higher you go, them
> more drift you will introduce) able to deliver 250 mA
> without fainting, a good keying relay with spark/click suppression
> and 6-8 amps of 24 VDC (plus the right connectors from Steve ;-)
> and you're on your way with the BC-375 even on 30 meters.
>
> Next:
> Regulating the filament buss and trying the 7984 tubes,
> which will have to wait until next paycheck.
> Nice thing about pentodes/tetrodes in this service:
> I can disconnect the screen lead (like in Drakes) and
> watch the output scope while tweeking the Neutralizing cap
> for minium. Works great. 1625s are about 45 degress from 211s.
>
> Gonna work me some 30 meter DX with a war vet
> designed in 1928.... sweeeeeeet....
>
> GL OM ES 73 DE Dave AB5S
>
>
>
> ------------------------------
>
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>
>
> End of Milsurplus Digest, Vol 115, Issue 5
> ******************************************
>
>
>

-- 
USE Morse code and baffle NSA.