[ARC5] FW: Way OT -- SX-28 - ARC5 selectivity
Richard Knoppow
1oldlens1 at ix.netcom.com
Sat Aug 7 22:30:55 EDT 2021
I don't know the whole story about the S-38. You may know it
started out as a version of the Echophone EC-1 but just a little
fancier (four bands instead of three). The original had a (forgot
the tube number) a combination triode and dual diode. H used the
triode as a conventional BFO and the diodes as a noise clipper.
At the time the S-38 came out there was serious inflation and
lots of other economic troubles, many strikes. Things were not
going back to their pre-war condition. I think in order to
maintain the price point something had to change and that
something was to eliminate the "real" BFO and the noise limiter.
I don't know if the idea of a regenerative IF stage was original
with Hallicrafters or not, I suspect not, in any case its evident
that they thought the function was well enough performed by the
makeshift (my term for it) BFO and no one would miss the noise
limiter. So, H saved one tube and its socket and some other
components including a switch. Somewhere there must have been a
cost analysis. It would be interesting to see but I suspect H
business records no longer exist. I think all the manufacturers
guessed wrong about post-war conditions and had to play catch up
to survive. A good example if the Hammarlund HQ-129-X. The model
number came from the originally intended price; $129.00 It lasted
a couple of months and was taken off the market. When it came
back the price had gone up considerably but it was a good
receiver and still a good value so it survived. There are other
examples and some things I have never gotten the whole story
about, such as the redesign of the SP-600 (almost certainly a bad
guess about the market) and why Collins stopped selling through
dealers for a time.
Anyway, I am babbling.
On 8/7/2021 6:31 PM, howard holden wrote:
>
> Interesting that the original S-38 had a BFO oscillator but not
> the succeeding models. In the mid 60s when was stationed at
> Gitmo and had my own station KG4DF, I used a Halli WR-600
> (S-120 with a phony wood grain cabinet) which had a fancier
> version of the regen IF stage of the S-38. Instead of the
> gimmick caps it used a pot from the suppressor to ground to
> control regeneration. Like any scheme of this type it wasn’t
> the greatest, but I used it even on 15M CW. The WR-600 was the
> only SW receiver in the PX that was usable on the ham bands so
> I made it do. One hand on the tuning all the time…..
>
> Howie WB2AWQ
>
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986>
> for Windows 10
>
> *From: *Richard Knoppow <mailto:1oldlens1 at ix.netcom.com>
> *Sent: *Saturday, August 7, 2021 1:25 PM
> *To: *arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net>
> *Subject: *Re: [ARC5] FW: Way OT -- SX-28 - ARC5 selectivity
>
> The S-38A and later had no control other than a switch for
> AM/CW. The AVC was partly shorted by this switch along with
> connecting a feedback circuit. The feedback consisted of a couple
> of "gimmick" wires that coupled the output back to the input of
> the IF amp. I don't remember if there is any procedure for
> adjusting it in the manual. When the switch was thrown the BFO
> came on. I was able to copy CW and even SSB with a lot of
> tweaking. The receiver is not very stable which doesn't help. The
> original S-38 had an additional tube which functioned as a "real"
> BFO and also a noise limiter. That had a pitch control and an
> additional switch for the NL. I have an S-38 but never got around
> to restoring it. My original S-38B is a mess. Been in storage for
> many years. One day I will restore it. It was my first SW receiver.
> I think Hallicrafters might have had a patent on the circuit
> they used but very similar circuits were in a number of other
> receivers so the patent does not seem to have restricted its use.
>
> On 8/7/2021 12:05 PM, Hubert Miller wrote:
> >> On Behalf Of Richard Knoppow
> > I think this is the same trick Hallicrafters used in the
> later S-38 (starting with the S-38A I think) also in the National
> > SW-54 and probably many other receivers. Eliminated needing a
> separate tube for the BFO. If was made regenerative
> >> and the AVC was disabled. On my S-38B it sort of worked.
> > I think that sums it up, it works "sort of". If I'm not
> mistaken, the Star Roamer had AVC plus the regeneration.
> > I tried that once on a Command Sets receiver and found it
> unsatisfactory. There's something goofy about a control
> > that varies selectivity and gain at the same time. It's
> harder, I think, than operating a regenerative receiver.
> > I recall that past articles recommended this also for the ARC-2.
> > And that some Japanese WWII field portable receivers used
> regen IF.
> > Just not what I would recommend.
> > -Hue
> >
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> --
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
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Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL
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