[ARC5] ARC5 Digest, Vol 129, Issue 40

Phillip Carpenter carpenterpa at tds.net
Fri Oct 17 08:34:40 EDT 2014


Pat,

The photo submission to the group was rejected by the moderator as too large a file. I selected a large pixel format that went over the 50KB limit. I have resubmitted the photo as a small pixel file attachment so we'll see if it makes it to the group to see this time.

I'm working on tracing the circuit out and am about half way through. I'll post it to the group for comment as soon as I finish getting all the values noted and hookup connections ironed out.

Respectfully,

Phil, W4RTX

Sent from my iPhone

> On Oct 17, 2014, at 8:23 AM, Paddy Ryan <pei7cn at eircom.net> wrote:
> 
> Miniature tube conversion:
> 
> This is interesting but alas I cannot see the picture?
> 
> He uses 7 tubes in place of the 6 octals. I take it that he uses the 6C4 as a separate osc into the 6BE6 and the H6s for rf and if amp? Is the 12AX7 used as 1/2 af preamp and 1/2 bfo? Then the 6AQ5 af  output from the AX7?
> 
> I am familiar with the 'repackaged' one from the 1957 QST book and as Ken says it uses Octals and has a noise limiter circuit added but the miniaturised one seems to be quite different from this..by the way you haven't said how good it works?
> 
> A circuit would be great!
> 
> 73 de Pat/EI7CN
> 
> -----Original Message----- From: arc5-request at mailman.qth.net
> Sent: Thursday, October 16, 2014 9:59 PM
> To: arc5 at mailman.qth.net
> Subject: ARC5 Digest, Vol 129, Issue 40
> 
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> Today's Topics:
> 
>  1. Miniature Tube Rebuild of ARC-5 BC-453 Receiver
>     (Phillip Carpenter)
>  2. Re: Miniature Tube Rebuild of ARC-5 BC-453 Receiver
>     (Kenneth G. Gordon)
>  3. Re: ARC-5s at 10 meters (was 400784741321) (Kenneth G. Gordon)
>  4. Hacked ARC-5s at 10 meters - more (Kenneth G. Gordon)
>  5. Re: Four pin VT-25/52 to nine pin miniature adapter prototype
>     (mstangelo at comcast.net)
>  6. Re: 400784741321 (john rose)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Thu, 16 Oct 2014 13:48:50 -0400
> From: Phillip Carpenter <carpenterpa at tds.net>
> To: ARC-5 Mail List <arc5 at mailman.qth.net>, Ken Gordon
> <kgordon2006 at frontier.com>
> Subject: [ARC5] Miniature Tube Rebuild of ARC-5 BC-453 Receiver
> Message-ID: <07BA54ED-52EA-4771-91D6-79355F987319 at tds.net>
> Content-Type: text/plain; charset=us-ascii
> 
> I picked up a BC-453 that was completely rebuilt by some Ham back in the 1960s. It works but needs tweaking and realignment. The Ham rebuilt the radio using mostly original parts but used the miniature tube versions of the octal tubes and added a built in power supply and AF amplifier with speaker.
> 
> The receiver's tube complement includes: 6C4, 6BE6, 3-6BH6s, 12AX7, and 6AQ5. Zener diodes are used in the power supply with a Triad R-10A power transformer.
> 
> The receiver is neatly built. Does anyone know of any articles of a Ham doing an ARC-5 receiver conversion to miniature tubes?
> 
> I'm in the process of tracing out the circuit but it would be helpful if anyone can shed more light on this repackaged Command Set receiver or knew the Ham who built it.
> 
> Phillip, W4RTX
> 
> Sent from my iPhone
> 
> ------------------------------
> 
> Message: 2
> Date: Thu, 16 Oct 2014 12:01:04 -0700
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> To: ARC5 <arc5 at mailman.qth.net>
> Subject: Re: [ARC5] Miniature Tube Rebuild of ARC-5 BC-453 Receiver
> Message-ID: <544015F0.7278.2CFCA3D3 at kgordon2006.frontier.com>
> Content-Type: text/plain; charset=US-ASCII
> 
>> On 16 Oct 2014 at 13:48, Phillip Carpenter wrote:
>> 
>> I picked up a BC-453 that was completely rebuilt by some Ham back in the 1960s.
>> It works but needs tweaking and realignment. The Ham rebuilt the radio using
>> mostly original parts but used the miniature tube versions of the octal tubes
>> and added a built in power supply and AF amplifier with speaker.
>> 
>> The receiver's tube complement includes: 6C4, 6BE6, 3-6BH6s, 12AX7, and 6AQ5.
>> Zener diodes are used in the power supply with a Triad R-10A power transformer.
>> 
>> The receiver is neatly built.
> 
> Yes, it sure is. Thank you for the photo. I have never seen such a
> modification
> 
>> Does anyone know of any articles of a Ham doing an
>> ARC-5 receiver conversion to miniature tubes?
> 
> No, although there is an article, "The ARC-5 Repackaged" in one of the
> Surplus destruction manuals in which someone repackaged a BC-453 onto a
> 3" high rack-panel. But he used the octal tubes.
> 
>> I'm in the process of tracing out the circuit but it would be helpful if anyone
>> can shed more light on this repackaged Command Set receiver or knew the Ham who
>> built it.
> 
> I would have no idea. Perhaps someone else here?
> 
> It was very well done, IMHO.
> 
> Ken W7EKB
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Thu, 16 Oct 2014 12:09:29 -0700
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> To: ARC5 <arc5 at mailman.qth.net>
> Subject: Re: [ARC5] ARC-5s at 10 meters (was 400784741321)
> Message-ID: <544017E9.12483.2D0456C6 at kgordon2006.frontier.com>
> Content-Type: text/plain; charset=US-ASCII
> 
>> On 16 Oct 2014 at 7:27, Ian Wilson wrote:
>> 
>> I would be surprised if the Q of a solenoid in the HF region increases
>> with frequency - for Cu, the skin depth between 1MHz and 10MHz
>> decreases by a factor of more than 3; so, as a first-order approximation,
>> the Q at 28MHz would be close to the Q at 8MHz (the increase in wL
>> is more or less cancelled by the increase in r).
> 
> Thanks, Ian. However, I suspect that Neil didn't mean that the "Q" increased
> with frequency, but simply that the increase in frequency didn't affect the
> circuit "Q". Your and his explanation coincide.
> 
>> 
>> In practice I suspect that the Q drops off faster than this because of
>> the effects of distributed capacitance (which in effect requires more
>> turns to achieve the desired inductance at higher frequencies, hence
>> yet more loss).
> 
> Yes. I had thought of that too, and had wondered about it.
> 
>> The combination of tube gain falling off above about 10MHz together
>> with losses in coil switching is presumably responsible for the "deaf
>> as a post" performance for some classic boatanchor receivers above
>> 20m....
> 
> Which brings up an interesting point: after I had finally gotten my hacked
> BC-454 to work properly at 10 meters, I was very surprised to find that the
> sensitivity at 10 meters was quite adequate. Although I will have to go back
> to review my notes, I recall that around a 1 microvolt signal was being easily
> copied there.
> 
> There was, of course, considerable noise, most probably from that horrid
> 12K8 mixer, but the signal was easily discernible, and this was with the
> original 12SK7s in it.
> 
> Ken W7EKB
> 
> 
> ------------------------------
> 
> Message: 4
> Date: Thu, 16 Oct 2014 12:16:00 -0700
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> To: ARC5 <arc5 at mailman.qth.net>
> Subject: [ARC5] Hacked ARC-5s at 10 meters - more
> Message-ID: <54401970.27705.2D0A4E3D at kgordon2006.frontier.com>
> Content-Type: text/plain; charset=US-ASCII
> 
> All this discussion brings up in my mind another question: it has been
> suggested that when the 12SK7s are replaced with 12SG7s, the overall
> internally generated noise level drops significantly.
> 
> I have tried this, and found it to be true for frequencies at 6 MHz and above,
> but that it really didn't do much at MF or even on 80 meters.
> 
> As I have repeatedly said, as far as I'm concerned, the primary source of
> receiver noise is that damned 12K8 mixer, which Terman's lists as the very
> noisiest mixer tube in his list at an ENR of 280,000 ohms.
> 
> However, in reviewing the characteristics of the 12SK7 and the 12SG7, there
> are noticeable differences.
> 
> For one thing, when I use a 12SG7 in the RF amp, in most cases, I can no
> longer peak the antenna trimmer: it is swung way over at one limit and
> obviously needs to go further.
> 
> Does anyone know what minor changes in biasing, let's say, that one would
> do to correct this?
> 
> Ken W7EKB
> Kenneth G. Gordon W7EKB
> 
> "Courage is being scared to death but saddling up anyway."--- John   Wayne
> 
> 
> 
> ------------------------------
> 
> Message: 5
> Date: Thu, 16 Oct 2014 19:25:17 +0000 (UTC)
> From: mstangelo at comcast.net
> To: Ben Hall <kd5byb at gmail.com>
> Cc: ARC-5 <arc5 at mailman.qth.net>
> Subject: Re: [ARC5] Four pin VT-25/52 to nine pin miniature adapter
> prototype
> Message-ID:
> <336210093.6971915.1413487517561.JavaMail.root at comcast.net>
> Content-Type: text/plain; charset=utf-8
> 
> Nice!
> 
> Where did you find the 4 pin plug?
> 
> Mike N2MS
> ----- Original Message -----
> From: Ben Hall <kd5byb at gmail.com>
> To: ARC-5 <arc5 at mailman.qth.net>
> Sent: Thu, 16 Oct 2014 00:57:01 -0000 (UTC)
> Subject: [ARC5] Four pin VT-25/52 to nine pin miniature adapter prototype
> 
> Good evening all,
> 
> Assembled a quick prototype this evening:
> 
> <http://www.kd5byb.net/BC230/proto1.jpg>
> 
> Once the superglue is dry, I'll do a fit check in my BC-230.  :)
> 
> Thanks much and 73,
> ben, kd5byb
> 
> 
> 
> ------------------------------
> 
> Message: 6
> Date: Thu, 16 Oct 2014 19:48:46 +0000
> From: john rose <brokenthumb at live.com>
> To: AKLDGUY . <neilb0627 at gmail.com>
> Cc: arc5 <arc5 at mailman.qth.net>
> Subject: Re: [ARC5] 400784741321
> Message-ID: <BLU404-EAS110E6BE429DDB3DFA3A0ADCDAAB0 at phx.gbl>
> Content-Type: text/plain; charset="utf-8"
> 
> Your assumption that ARC used the condenser (part #6558) from the 6 to 9.1 (#46106) rig is incorrect. The RAV (#46109) which tunes 20 to 27 mcs uses a unique condenser (#4609). While Ken was telling us about his struggle with the 3 to 6 rig, some pix of this unique item were posted (constructed of ?unobtainium?). Ken was working with a BC454 which uses another condenser (#4601).
> 
> BTW the IF of the 20/27 rig is 4200 kcs and Mr. White very nicely outlined why this is so in the article Command Set Receivers for all Frequencies. Has anyone here seen any of these for sale lately?
> 
> 
> 
> From: AKLDGUY .
> Sent: ?Thursday?, ?October? ?16?, ?2014 ?3?:?04? ?AM
> To: kgordon2006 at frontier.com, arc5
> 
> 
> 
> 
> 
>> I completely rewound all three inductors in the receiver following the
> article
>> that Gordon White wrote some time ago entitled, "Command Receivers for
>> All Frequencies", in which article Gordon described and listed the turns
> on
>> the coils that ARC came up with for THEIR early HF receivers up to 27 MHz.
>> 
>> I used ARC's 27 MHz data, in fact, as the starting point for my coils.
> 
> OK, you rewound the coils on the basis of A.R.C.'s data.
> 
> Q is the reactance of either the inductor or capacitance at resonance,
> divided
> by the series resistance, which in this case is in the coil if we ignore
> other very
> small losses.
> 
> In my suggested modification (no modification of the coil) the Q is more
> than
> tripled by going from 7-9 to 28-30 MHz because the coil reactance more than
> triples. The higher Q at the higher frequency means the selectivity curve
> is the
> same as at the lower frequency. The curve will be the same number of dB down
> at the same frequency offset at both 9 MHz and 30 MHz.
> 
> There would therefore seem to be no good reason for taking turns off the
> coils.
> Why did A.R.C. use reduced turns? Probably because they were faced with a
> too large value of tuning gang (no smaller gang available), so they used a
> large
> amount of **parallel** capacitance across the gang to reduce its tuning
> range
> and reduced the number of turns to compensate.
> 
>> Now I WILL say that your method would most certainly eliminate the
>> necessity for removing any plates from the capacitors, but I STILL say,
> that
>> the inductances would have to be "adjusted" also in order to maintain
> circuit
>> "Q".
> 
> Yes, my method does eliminate the need to remove plates, but the selectivity
> self-adjusts by virtue of the rise in Q as described above. A Q of 100 at 9
> MHz
> (easily possible) becomes a Q of more than 300 at 30 MHz, and the
> selectivity
> (percentage change) at both bands is the same.
> 
> I'd suggest that anyone contemplating modifying a 6-9.1 Mc/s receiver for
> 10m
> try my suggestion first. You have nothing to lose. It's simple and
> reversible. Use
> very good quality capacitors and let them cool before evaluating.
> 
> 73 de Neil ZL1ANM
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> 
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> ------------------------------
> 
> End of ARC5 Digest, Vol 129, Issue 40
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