#32001

I bought my first piece of radio equipment in 1957 at age 14, an
R-26/ARC-5 command set receiver. I still have it but haven't used it
for years.

I'm pondering working up a power supply for it to get it back on the
air, probably paired with my Multi-Elmac AF-67 transmitter, which is
usually paired with my S-40B.

In looking over the schematic of the R-26 and thinking about the recent
discussions of the circuitry of the S-20R and S-40B, I note a lot of
similarity between the command set receiver and the Hallicrafters. The
command set uses 12 volt tubes while the two Halli receivers use 6 volt
tubes, some of them equivalent except for the filament voltage.

The R-26 includes no band switching and covers 3-6 MHz which are the
main differences between it and the two Hallicrafters receivers. The IF
frequency in the R-26 is also much higher, at 1415 kHz, not a practical
frequency for the bandswitched Hallis with coverage down to the low end
of the BC band.

The most interesting (to me) similarity is the use of "gimmick"
capacitors in all three receivers to couple the BFO signal to the
transmission path:

S-20R C15 twisted leads to form small capacity
S-40B C38 2 mmf. "Gimmick" (in schematic)
twisted wire assembly (in parts list)
R-26 C33 <2 mmf. wiring capacitance

The S-20R also uses a "gimmick" to couple the high frequency oscillator
signal in the mixer stage (C38).

I haven't looked in detail at other makes of receivers from the '30 and
'40s, but I wonder whether the S-20R and the R-26 were just reflecting
similarities due to good engineering practice of that era, or did
someone from Hallicrafters influence the design?

73,

Maynard
W6PAP

#32005

Could not speak to who influenced the design of the Command receivers but a word of caution. If you have followed their history, be aware of the likely failure of those neat looking can bypass capacitors. My BC-453 began experiencing failure of those decades ago after 10 years of excellent service starting in the mid 60's.

Before applying a new power supply it might be wise to just go ahead and replace all of those with new ceramic bypasses. The oil filled cans deteriorate even when not in use and go dead short. I was able to see the burn paths clearly through the mica after failures.

Otherwise, enjoy the restoration. No reason it should not still be a good performer.

73 ... Ed, WA9GQK

On Friday, March 14, 2025 at 05:08:41 PM CDT, Maynard Wright via groups.io <m-wright@...> wrote:

I bought my first piece of radio equipment in 1957 at age 14, an
R-26/ARC-5 command set receiver. I still have it but haven't used it
for years.

I'm pondering working up a power supply for it to get it back on the
air, probably paired with my Multi-Elmac AF-67 transmitter, which is
usually paired with my S-40B.

In looking over the schematic of the R-26 and thinking about the recent
discussions of the circuitry of the S-20R and S-40B, I note a lot of
similarity between the command set receiver and the Hallicrafters. The
command set uses 12 volt tubes while the two Halli receivers use 6 volt
tubes, some of them equivalent except for the filament voltage.

The R-26 includes no band switching and covers 3-6 MHz which are the
main differences between it and the two Hallicrafters receivers. The IF
frequency in the R-26 is also much higher, at 1415 kHz, not a practical
frequency for the bandswitched Hallis with coverage down to the low end
of the BC band.

The most interesting (to me) similarity is the use of "gimmick"
capacitors in all three receivers to couple the BFO signal to the
transmission path:

S-20R C15 twisted leads to form small capacity
S-40B C38 2 mmf. "Gimmick" (in schematic)
twisted wire assembly (in parts list)
R-26 C33 <2 mmf. wiring capacitance

The S-20R also uses a "gimmick" to couple the high frequency oscillator
signal in the mixer stage (C38).

I haven't looked in detail at other makes of receivers from the '30 and
'40s, but I wonder whether the S-20R and the R-26 were just reflecting
similarities due to good engineering practice of that era, or did
someone from Hallicrafters influence the design?

73,

Maynard
W6PAP

#32006

开云体育

Maynard ??there is a bit of stuff here? Rr the ?R26 and others

I am visitor no?

See also ??????

Schematic ?? ??but very hard to read

?

I see a wiring diagram on? Page pdf 195 ??in? ?? no OCR? and

Pdf page 142 has schematic? ,here is a fragment

?

I know NOTHING about this stuff, ?so I hope it might help

Show quoted text

From: [email protected] [mailto:[email protected]] On Behalf Of Maynard Wright via groups.io
Sent: Friday, March 14, 2025 6:11 PM
To: [email protected]
Subject: [HallicraftersRadios] S-20R, S-40B, R-26/ARC-5

?

I bought my first piece of radio equipment in 1957 at age 14, an
R-26/ARC-5 command set receiver. I still have it but haven't used it
for years.

I'm pondering working up a power supply for it to get it back on the
air, probably paired with my Multi-Elmac AF-67 transmitter, which is
usually paired with my S-40B.

In looking over the schematic of the R-26 and thinking about the recent
discussions of the circuitry of the S-20R and S-40B, I note a lot of
similarity between the command set receiver and the Hallicrafters. The
command set uses 12 volt tubes while the two Halli receivers use 6 volt
tubes, some of them equivalent except for the filament voltage.

The R-26 includes no band switching and covers 3-6 MHz which are the
main differences between it and the two Hallicrafters receivers. The IF
frequency in the R-26 is also much higher, at 1415 kHz, not a practical
frequency for the bandswitched Hallis with coverage down to the low end
of the BC band.

The most interesting (to me) similarity is the use of "gimmick"
capacitors in all three receivers to couple the BFO signal to the
transmission path:

S-20R C15 twisted leads to form small capacity
S-40B C38 2 mmf. "Gimmick" (in schematic)
twisted wire assembly (in parts list)
R-26 C33 <2 mmf. wiring capacitance

The S-20R also uses a "gimmick" to couple the high frequency oscillator
signal in the mixer stage (C38).

I haven't looked in detail at other makes of receivers from the '30 and
'40s, but I wonder whether the S-20R and the R-26 were just reflecting
similarities due to good engineering practice of that era, or did
someone from Hallicrafters influence the design?

73,

Maynard
W6PAP

_._,_._,_

--
don??? va3drl

#32007

Hi, Ed,

Yes, I will replace those capacitors. This is a little different than
the usual recap in that those old capacitors are part of the visual
appeal of the underside of the unit (does that matter? Maybe I'm just
getting too old). So I will replace them electrically but leave the old
ones in place physically. I will, of course, completely disconnect the
old caps as bridging new ones across them won't fix some of the issues
they may have.

I recently recapped my Echophone EC-1A and an S-38 (no suffix) is in the
queue. The command set won't be much different except for the need to
physically mount the new caps.

One of the reasons for saving the old caps is that some folks have
opened the old ones carefully and inserted new caps and then closed
them. There is an article somewhere about how to do that but I think I
will just replace them electrically and leave them in place physically
in case some future owner wants to restore them.

That's sort of the same thing as restuffing an electrolytic can in a
Hallicrafters receiver except that almost nobody will ever see the
underside of an R-26 once the bottom plate is screwed in place.

I have a copy of "Command Sets" by CQ Magazine in 1957 (134 pages) and
it has a wealth of articles and schematics. When there were thousands
of these units available at $5.00 apiece (what I paid in 1957) people
made all sorts of things from them, VFOs for one thing.

73,

Maynard
W6PAP

Show quoted text

On 3/14/25 16:20, edward schumacher wrote:

Could not speak to who influenced the design of the Command receivers
but a word of caution. If you have followed their history, be aware of
the likely failure of those neat looking can bypass capacitors. My
BC-453 began experiencing failure of those decades ago after 10 years of
excellent service starting in the mid 60's.

Before applying a new power supply it might be wise to just go ahead and
replace all of those with new ceramic bypasses. The oil filled cans
deteriorate even when not in use and go dead short. I was able to see
the burn paths clearly through the mica after failures.

Otherwise, enjoy the restoration. No reason it should not still be a
good performer.

73 ... Ed, WA9GQK

On Friday, March 14, 2025 at 05:08:41 PM CDT, Maynard Wright via
groups.io <m-wright@...> wrote:

I bought my first piece of radio equipment in 1957 at age 14, an
R-26/ARC-5 command set receiver. I still have it but haven't used it
for years.

I'm pondering working up a power supply for it to get it back on the
air, probably paired with my Multi-Elmac AF-67 transmitter, which is
usually paired with my S-40B.

In looking over the schematic of the R-26 and thinking about the recent
discussions of the circuitry of the S-20R and S-40B, I note a lot of
similarity between the command set receiver and the Hallicrafters. The
command set uses 12 volt tubes while the two Halli receivers use 6 volt
tubes, some of them equivalent except for the filament voltage.

The R-26 includes no band switching and covers 3-6 MHz which are the
main differences between it and the two Hallicrafters receivers. The IF
frequency in the R-26 is also much higher, at 1415 kHz, not a practical
frequency for the bandswitched Hallis with coverage down to the low end
of the BC band.

The most interesting (to me) similarity is the use of "gimmick"
capacitors in all three receivers to couple the BFO signal to the
transmission path:

S-20R C15 twisted leads to form small capacity
S-40B C38 2 mmf. "Gimmick" (in schematic)
twisted wire assembly (in parts list)
R-26 C33 <2 mmf. wiring capacitance

The S-20R also uses a "gimmick" to couple the high frequency oscillator
signal in the mixer stage (C38).

I haven't looked in detail at other makes of receivers from the '30 and
'40s, but I wonder whether the S-20R and the R-26 were just reflecting
similarities due to good engineering practice of that era, or did
someone from Hallicrafters influence the design?

73,

Maynard
W6PAP