Tom That is a shame.? I was just wondering if you had made any progress.? Perhaps a list member up in the north-west area of the country would be interested in having a go at it?? How far are you from the Canadian border?
I'm in Arkansas over 2000 miles away from you so that would be a lot of shipping expense for me to take a look at it.? That said, the furthest I have done a repair was for a gentleman in Fukushima, Japan. Regards, Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
I certainly appreciate all the advice, hints and overall help I received in my attempt to resurrect this fine old survivor but, for me at least, I think the journey is over. Properly servicing the mixer section means that the LO coil assembly will have to be sufficiently lifted or even removed from the chassis. I found that doing so is beyond my ability. This assembly is connected to the main tuning capacitor by a connection that I am unable to de-solder in such a tight spot. It would take a heftier soldering iron than either one of the two I have, and even if I could, I doubt my ability to reconnect it. I'm a hobbyist, not a technician with the experience to deal with such a challenge.
?
It's a pity--I think this receiver would be very serviceable if repaired, and be capable of performing as well as most vintage, single conversion receivers lacking a crystal filter. So, back on the shelf it goes. I'll hold on to it for a while--after all, not too many people are going to want to tackle a receiver with challenges like this one.
?
Thanks again,
?
Tom
On 03/09/2025 6:11 PM PDT don Root <drootofallevil@...> wrote:
?
?
Jim & Tom?
The Hexode signal grid has a max? or min? voltage of -3? presumably to the cathode [depends who you read] , but my conclusion from a Sylvania ??blurb? is that it can go as positive as -3 volts, and as negative as -30 where there is little transconductance, and so is often connected to the AVC, but apparently not in the S-20R. but that does not help the situation.
As Jim says, on band 1 ?there is no ground, and I say there is no control of THAT grid voltage by ground, AVC or other, so it floats. On the other bands the bottoms of ?3,2,1 can be grounded [all depending] providing a DC ground ?but it goes thru the coil{s} so is strange to me. But band 1 is a real mystery to me too. ?
?
Tom, I suggested a test for the bandswitch area? was it not practicle? ?
?
?
That is interesting.? The tube manual indicates that -3 volts should be there.? Have you replaced C5 and C8?? Minor leakage in either could cancel the expected negative bias on G3 of the 6K8.? From the QST article, I expect that there are unintended interactions when the expected voltages are out of spec.
In looking at the schematic for the umpteenth time, I see how the upper band tank coils are returned to ground through switch 7D rotor that shorts the bottom of the band coils to ground.? Not sure how L13 is grounded when the band switch is in the BCB setting.? If you measure the DC resistance from the grid cap to ground you should measure R12 (33 ohms +/- 20%) plus the coil resistance for each band switch setting.? Is this the case???
Measuring from the switch side of R12, you should measure just the tank coil resistance to ground.? That resistance should increase as the band switch connects to the next lower tank coil.? If you don't see the coil resistance then perhaps the oscillator stator sections of either C1 or C2 is grounded?
Likewise, the switch side of C37 should measure the LO coil resistance to ground for each band switch setting.? Like the above, each lower band coil resistance will be higher.? Is this the case?
Remote troubleshooting is a s-l-o-w process,
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Sunday, March 9, 2025 at 11:47:14 AM CDT, Allthumbs via groups.io <btse1@...> wrote:
Thank you, Jim. The 6K8 control grid (grid cap) measures 0.00 vdc, pretty much as expected.
--
don??? va3drl
|
Tom,? well we all get worn down and discouraged when things beat us. Also, after concentrating on something, it is hard to see the forest ?for the trees.? So perhaps it is time for a break.? Most of us just dab in this, and learn bits and pieces from here and there. Maybe we [ me anyhow] speak over your head, since we as individuals don’t know “just what you know”. That is always a problem. It is best to speak up; this is not a competition, it is a mutual assistance group of non-professionals down to first time dabblers. ?While you have your nose in the Rosin smoke, I’m looking into info on the 6K8? and other converters, and so learning a little bit. ? For some time in the future, as to your problem , that cap must be C7 a 2200??F [or these days maybe 2200pF] connected to the cathode? and not C37 connected to the bandswitch.? You had a good voltage on the cathode, so it [and C8] don’t seem to be shorted and my guess is they are ok but cant be sure. ? I wonder if you understood the simple resistance tests on the coil area? that I sent before. ??? -- don??? va3drl
|
Re: SX-62 alignment instructions
Oh Jim, my ONLY intent of this was? about removing a tube or otherwise preventing an antenna input while at the same time? using the mixer tube as a buffer between the Sig generator and the first IF transformer.?? There are different methods all depending on the circuit and its accessible points. ?It is part of my response to his original question. ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Sunday, March 16, 2025 4:32 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-62 alignment instructions? Your IF alignment instructions are missing an important caveat.? You must lower the SG output to below where the AVC begins to operate.? Not doing so will cause the IFTs to be misaligned.? With the volume and RF gain controls at maximum, the SG modulation should be heard but just barely over the background noise as the IF alignment progresses.?? Better to measure the voltage at the speaker terminals and not rely too much on one's hearing, especially as we get older, right Richard?.? This IF alignment method would be useable for all superhetrodyne receivers, not just hallicrafters. Might as well mention that if the radio has a crystal filter in the IF chain, the frequency that this crystal passes through the filter is used to align the IFTs, not the SG dial reading. -- don??? va3drl
|
Re: SX-62 alignment instructions
Thanks, I tried(the correct way), but I'm having issues with the FM, it has so much gain in FM that the oscillator stops, until I reduce the RF gain, I have to align it on 2-3? on the RF gain to get anything out of it. going to start over and try again.
toggle quoted message
Show quoted text
Scott, as an aside, this is what they say for the S-20R .. they use the converter but disconnect it from upstream.
?
Thanks!, I didn't look up which pin did what, I thought it could have been the plate, and pulling the tube would isolate the RF coming in. SX-62B
Scott, It is a SX-62 {no suffix} ?
Since the signal is injected on the grid, it would seem the tube would have to be in service. ??
?
--
don??? va3drl
|
Re: SX-62 alignment instructions
Don Your IF alignment instructions are missing an important caveat.? You must lower the SG output to below where the AVC begins to operate.? Not doing so will cause the IFTs to be misaligned.? With the volume and RF gain controls at maximum, the SG modulation should be heard but just barely over the background noise as the IF alignment progresses.??
Better to measure the voltage at the speaker terminals and not rely too much on one's hearing, especially as we get older, right Richard?.? This IF alignment method would be useable for all superhetrodyne receivers, not just hallicrafters.
Might as well mention that if the radio has a crystal filter in the IF chain, the frequency that this crystal passes through the filter is used to align the IFTs, not the SG dial reading. Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
Scott, as an aside, this is what they say for the S-20R .. they use the converter but disconnect it from upstream. 
From: [email protected] [mailto:[email protected]] On Behalf Of Scott Petersen via groups.io
Sent: Saturday, March 15, 2025 2:48 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-62 alignment instructions ? Thanks!, I didn't look up which pin did what, I thought it could have been the plate, and pulling the tube would isolate the RF coming in. SX-62B
Scott, It is a SX-62 {no suffix} ? Since the signal is injected on the grid, it would seem the tube would have to be in service. ?? ?
--
don??? va3drl
|
SR-160 Vernier Dial Lubricaion
Hi All,
?
I am restoring an SR-160 that has been dormant for some time.? The vernier dial does rotate through it's full rotation but does so sluggishly, getting stuck periodically.? Does anyone have any suggestions regarding lubrication of the vernier dial mechanism (type of lubricant, places to lubricate, etc)?
?
--
|
I certainly appreciate all the advice, hints and overall help I received in my attempt to resurrect this fine old survivor but, for me at least, I think the journey is over. Properly servicing the mixer section means that the LO coil assembly will have to be sufficiently lifted or even removed from the chassis. I found that doing so is beyond my ability. This assembly is connected to the main tuning capacitor by a connection that I am unable to de-solder in such a tight spot. It would take a heftier soldering iron than either one of the two I have, and even if I could, I doubt my ability to reconnect it. I'm a hobbyist, not a technician with the experience to deal with such a challenge.
?
It's a pity--I think this receiver would be very serviceable if repaired, and be capable of performing as well as most vintage, single conversion receivers lacking a crystal filter. So, back on the shelf it goes. I'll hold on to it for a while--after all, not too many people are going to want to tackle a receiver with challenges like this one.
?
Thanks again,
?
Tom
On 03/09/2025 6:11 PM PDT don Root <drootofallevil@...> wrote:
?
?
Jim & Tom?
The Hexode signal grid has a max? or min? voltage of -3? presumably to the cathode [depends who you read] , but my conclusion from a Sylvania ??blurb? is that it can go as positive as -3 volts, and as negative as -30 where there is little transconductance, and so is often connected to the AVC, but apparently not in the S-20R. but that does not help the situation.
As Jim says, on band 1 ?there is no ground, and I say there is no control of THAT grid voltage by ground, AVC or other, so it floats. On the other bands the bottoms of ?3,2,1 can be grounded [all depending] providing a DC ground ?but it goes thru the coil{s} so is strange to me. But band 1 is a real mystery to me too. ?
?
Tom, I suggested a test for the bandswitch area? was it not practicle? ?
?
?
That is interesting.? The tube manual indicates that -3 volts should be there.? Have you replaced C5 and C8?? Minor leakage in either could cancel the expected negative bias on G3 of the 6K8.? From the QST article, I expect that there are unintended interactions when the expected voltages are out of spec.
In looking at the schematic for the umpteenth time, I see how the upper band tank coils are returned to ground through switch 7D rotor that shorts the bottom of the band coils to ground.? Not sure how L13 is grounded when the band switch is in the BCB setting.? If you measure the DC resistance from the grid cap to ground you should measure R12 (33 ohms +/- 20%) plus the coil resistance for each band switch setting.? Is this the case???
Measuring from the switch side of R12, you should measure just the tank coil resistance to ground.? That resistance should increase as the band switch connects to the next lower tank coil.? If you don't see the coil resistance then perhaps the oscillator stator sections of either C1 or C2 is grounded?
Likewise, the switch side of C37 should measure the LO coil resistance to ground for each band switch setting.? Like the above, each lower band coil resistance will be higher.? Is this the case?
Remote troubleshooting is a s-l-o-w process,
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Sunday, March 9, 2025 at 11:47:14 AM CDT, Allthumbs via groups.io <btse1@...> wrote:
Thank you, Jim. The 6K8 control grid (grid cap) measures 0.00 vdc, pretty much as expected.
--
don??? va3drl
|
Re: SX-62 alignment instructions
Scott, as an aside, this is what they say for the S-20R .. they use the converter but disconnect it from upstream. 
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Scott Petersen via groups.io
Sent: Saturday, March 15, 2025 2:48 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-62 alignment instructions? Thanks!, I didn't look up which pin did what, I thought it could have been the plate, and pulling the tube would isolate the RF coming in. SX-62B
Scott, It is a SX-62 {no suffix} ? Since the signal is injected on the grid, it would seem the tube would have to be in service. ?? ? -- don??? va3drl
|
Re: Interesting observation concerning crystals...
All boxed up and ready to go out in the mail tomorrow.? You'll get a notice from my Pirateship account.
73 - Steve, KW4H
On Saturday, March 15th, 2025 at 9:58 PM, Tom Smith <n5ama@...> wrote:
Hi Steve,
I’ll put a check in the mail to you tomorrow for three of them. Thanks for making them available.
?
Tom N5AMA
|
Re: WTB SR-160 Front Panel
Walt is **THE MAN** !!!
73/jeff/ac0c
alpha-charlie-zero-charlie
On 3/15/2025 1:44 PM, Scott WA9WFA via
groups.io wrote:
toggle quoted message
Show quoted text
First off, I need to apologize to the guys here
that responded to my SR-500 Tornado and SR-160 WTB post and
didn’t hear back from me. ?I was on the road.
Next, while on the road, I stopped by Walt
Cates' QTH in Kansas City where I had the pleasure of meeting
him and buying his SR-500 Tornado and PS-500AC. ?It’s in my
shack and on the air. ?My first contact was with W1AW believe
it or not. ?
For several years Walt has been looking for an
SR-160 panel to replace this SR-500 panel. ?The Tornado panel
is the same as the 160 with the exception of the metal Tornado
label below the escutcheon. ?The metal label is removable.
?Walt wasn’t able to find one in all those years, but I
thought I would continue the search, so I know it’s a long
shot.
I just can’t leave a radio alone but prefer to
spiff up and putter with them. ?I think this would be a fun
spiff up project if a panel can be located. ?If not, fine, I
am delighted with the radio never-the-less! ?
73, Scott WA9WFA
|
Re: Interesting observation concerning crystals...
Hi Steve,
I’ll put a check in the mail to you tomorrow for three of them. Thanks for making them available.
?
Tom N5AMA
|
Re: WTB SR-160 Front Panel
Greetings,
I am not sure if this thread regarding
a front panel applies to Scott or Walt, but I would be willing to
swap an SR-160 panel for an SR-500 panel. My SR-160 was not
original when I got it as it had a solid state VFO (while a great
addition, it was not "stock"). Subsequently, I did the mods that
were implemented when the SR-160 was turned into the SR-500 by
Hallicrafters so it is neither a stock SR-160 nor SR-500.
If the 'Robert' in your email is meant
for me, you can reach me directly at rwkembel at comcast dot net.
Bob,? K7DYB
On 3/15/2025 7:45 PM, Scott WA9WFA via
groups.io wrote:
toggle quoted message
Show quoted text
Hi Robert, I was unable to find your personal email to take
this discussion off line. ?Please drop me an email at wa9wfa at
gmail dot com. ? Here is an internet photo of an SR-160.
?Thanks. ?73, Scott WA9WFA
?
?
?
?
?
?
?
|
Re: WTB SR-160 Front Panel
Hi Robert, I was unable to find your personal email to take this discussion off line. ?Please drop me an email at wa9wfa at gmail dot com. ? Here is an internet photo of an SR-160. ?Thanks. ?73, Scott WA9WFA
?
?
?
?
?
?
?
|
Re: WTB SR-160 Front Panel
Scott, I may have a parts SR160 around here.? Please send me a pic? of the panel, make it easier to look at the shelves. THanks Robert
On Saturday, March 15, 2025 at 02:45:00 PM EDT, Scott WA9WFA via groups.io <whitebear1122@...> wrote:
First off, I need to apologize to the guys here that responded to my SR-500 Tornado and SR-160 WTB post and didn’t hear back from me. ?I was on the road.
Next, while on the road, I stopped by Walt Cates' QTH in Kansas City where I had the pleasure of meeting him and buying his SR-500 Tornado and PS-500AC. ?It’s in my shack and on the air. ?My first contact was with W1AW believe it or not. ?
For several years Walt has been looking for an SR-160 panel to replace this SR-500 panel. ?The Tornado panel is the same as the 160 with the exception of the metal Tornado label below the escutcheon. ?The metal label is removable. ?Walt wasn’t able to find one in all those years, but I thought I would continue the search, so I know it’s a long shot.
I just can’t leave a radio alone but prefer to spiff up and putter with them. ?I think this would be a fun spiff up project if a panel can be located. ?If not, fine, I am delighted with the radio never-the-less! ?
73, Scott WA9WFA
|
Re: SX-62 alignment instructions
Thanks!, I didn't look up which pin did what, I thought it could have been the plate, and pulling the tube would isolate the RF coming in. SX-62B
toggle quoted message
Show quoted text
Scott, It is a SX-62 {no suffix} ?
Since the signal is injected on the grid, it would seem the tube would have to be in service. ??
?
?
In the instructions it says to connect a .1mfd capacitor to pin 1 of the 7F8, do I leave the tube in circuit, or put the lead directly in the socket?
Should I remove the chassis side cover, or will it make a difference to the alignment, same with the RF shield under the IF's?
|
First off, I need to apologize to the guys here that responded to my SR-500 Tornado and SR-160 WTB post and didn’t hear back from me. ?I was on the road.
Next, while on the road, I stopped by Walt Cates' QTH in Kansas City where I had the pleasure of meeting him and buying his SR-500 Tornado and PS-500AC. ?It’s in my shack and on the air. ?My first contact was with W1AW believe it or not. ?
For several years Walt has been looking for an SR-160 panel to replace this SR-500 panel. ?The Tornado panel is the same as the 160 with the exception of the metal Tornado label below the escutcheon. ?The metal label is removable. ?Walt wasn’t able to find one in all those years, but I thought I would continue the search, so I know it’s a long shot.
I just can’t leave a radio alone but prefer to spiff up and putter with them. ?I think this would be a fun spiff up project if a panel can be located. ?If not, fine, I am delighted with the radio never-the-less! ?
73, Scott WA9WFA
|
Re: SX-62 alignment instructions
Scott, It is a SX-62 {no suffix} ? Since the signal is injected on the grid, it would seem the tube would have to be in service. ?? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Scott Petersen via groups.io
Sent: Friday, March 14, 2025 6:57 PM
To: [email protected]
Subject: [HallicraftersRadios] SX-62 alignment instructions? In the instructions it says to connect a .1mfd capacitor to pin 1 of the 7F8, do I leave the tube in circuit, or put the lead directly in the socket? Should I remove the chassis side cover, or will it make a difference to the alignment, same with the RF shield under the IF's? -- don??? va3drl
|
Re: S-20R, S-40B, R-26/ARC-5
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
toggle quoted message
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
|
Re: S-20R, S-40B, R-26/ARC-5
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
toggle quoted message
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
|
Re: S-20R, S-40B, R-26/ARC-5
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
|
Jim Whartenby
don Root
Allthumbs
Robert Kembel
