Topics

General Radio 874 Connector, inner conductor "bendies"

Roy Thistle
 

Hi All:
Apologies, if this has been covered (there are a lot of posts on 874!).. but the picture on Tekwiki of the GR-874 (the one with the plug facing the viewer... so you can see into it)… well that picture shows two of the leaves of the center conductor, bent in at the corners, and so having little "bendies" barbs, or tangs. (You have to see the picture!).
http://w140.com/tekwiki/wiki/GR-874_connector.
My initial question is… Is that normal, or is the center conductor of the connector damaged? (You can see a bit of those "bendies" on the leaves of the outer conductor, in the picture, too.) My initial guess is the matching, inserter GR-874, after being rotated, and mated, has damaged the insertee? If so, how does the mated pair maintain 50 ohms?
Best regards and wishes.
Roy

george edmonds
 

Hi Roy

These are hermaphrodite connectors and the picture that you refer to does not appear damaged.

73 George G6HIG On Tuesday, August 6, 2019, 10:44:41 PM GMT+1, Roy Thistle <roy.thistle@...> wrote:

Hi All:
Apologies, if this has been covered (there are a lot of posts on 874!).. but the picture on Tekwiki of the GR-874 (the one with the plug facing the viewer... so you can see into it)… well that picture shows two of the leaves of the center conductor, bent in at the corners, and so having little "bendies" barbs, or tangs. (You have to see the picture!).
http://w140.com/tekwiki/wiki/GR-874_connector.
My initial question is… Is that normal, or is the center conductor of the connector damaged? (You can see a bit of those "bendies" on the leaves of the outer conductor, in the picture, too.) My initial guess is the matching, inserter GR-874, after being rotated, and mated, has damaged the insertee?  If so, how does the mated pair maintain 50 ohms?
Best regards and wishes.
Roy

Merchison Burke
 

I don't see any bending. What I see are the sharp edges have been chamfered which makes it easy to mate with another GR874 connector. All my GR874 connectors look the same.

On 2019-Aug-06 5:44 PM, Roy Thistle wrote:
Hi All:
Apologies, if this has been covered (there are a lot of posts on 874!).. but the picture on Tekwiki of the GR-874 (the one with the plug facing the viewer... so you can see into it)??? well that picture shows two of the leaves of the center conductor, bent in at the corners, and so having little "bendies" barbs, or tangs. (You have to see the picture!).
http://w140.com/tekwiki/wiki/GR-874_connector.
My initial question is??? Is that normal, or is the center conductor of the connector damaged? (You can see a bit of those "bendies" on the leaves of the outer conductor, in the picture, too.) My initial guess is the matching, inserter GR-874, after being rotated, and mated, has damaged the insertee? If so, how does the mated pair maintain 50 ohms?
Best regards and wishes.
Roy



---
This email has been checked for viruses by AVG.
https://www.avg.com

Richard Knoppow
 

I looked at a couple of 874 s just now. The tips of the small center contacts are pointed and slightly tapered toward the center. The larger of the center contacts are tapered toward the inside and slightly bent outward so that the opposing contacts slide over each other and form a continuous tube. Its somewhat the same as the outside contacts.
While the photo may be an optical illusion it does not look right. I don't think the connector was twisted but someone may have put a 274 banana plug into it and bent it. The 274 _can_ be used on an 874 but one must be careful not to stress it. The design is such that the outer shell makes contact first and pretty much prevents the mating plugs from being twisted.
The 874 is a pretty good connector but has the disadvantage of not having a precise reference plane. They can act as a short sliding line. Even when locked the reference plane is uncertain.

On 8/6/2019 2:44 PM, Roy Thistle wrote:
Hi All:
Apologies, if this has been covered (there are a lot of posts on 874!).. but the picture on Tekwiki of the GR-874 (the one with the plug facing the viewer... so you can see into it)… well that picture shows two of the leaves of the center conductor, bent in at the corners, and so having little "bendies" barbs, or tangs. (You have to see the picture!).
http://w140.com/tekwiki/wiki/GR-874_connector.
My initial question is… Is that normal, or is the center conductor of the connector damaged? (You can see a bit of those "bendies" on the leaves of the outer conductor, in the picture, too.) My initial guess is the matching, inserter GR-874, after being rotated, and mated, has damaged the insertee? If so, how does the mated pair maintain 50 ohms?
Best regards and wishes.
Roy
--
Richard Knoppow
dickburk@...
WB6KBL

Richard Knoppow
 

FWIW a description of the 874 appeared in the General Radio Experimenter
https://www.ietlabs.com/pdf/GR_Experimenters/1948/GenRad_Experimenter_Oct_1948.pdf
The patent appears at:
https://patentimages.storage.googleapis.com/22/e8/ad/433a7c35082ad9/US2548457.pdf
This has a fairly detailed drawing.

On 8/6/2019 3:24 PM, Richard Knoppow wrote:
    I looked at a couple of 874 s just now.
--
Richard Knoppow
dickburk@...
WB6KBL

Dale H. Cook
 

On 8/6/2019 5:44 PM, Roy Thistle wrote:

My initial question is… Is that normal, or is the center conductor of the connector damaged?
I would pretty much have to look at the actual connector to tell whether that is a trick of lighting or signs of damage. There are no "bendies" on the leaves of a GR-874 inner conductor, just on the outer conductor. You couldn't have anything bent outwards on the inner conductor in any case as that would cause an impedance bump in the skin effect flow of current.

My initial guess is the matching, inserter GR-874, after being rotated, and mated, has damaged the insertee?
GR-874 connectors are not rotated. They are inserted straight into each other and held by friction. GR later introduced locking rings to prevent accidental separation, but GR-874 connectors with or without locking rings will mate with each other.

If so, how does the mated pair maintain 50 ohms?
They do do by presenting smooth surfaces on the outside of the inner conductor and the inside of the outer conductor the same way that any RF connector must do to provide constant impedance.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/

 

Hi Roy,

The design of the GR-874 is unique (except for its bigger brother) in the electronics industry. It is brilliant design which is why it has lasted so long.
The connectors are hermaphroditic, in other words it has both male and female parts so they can mate to themselves. There is no need for male plugs and female sockets.

To insure the outer leaves are positioned properly with each other it was necessary to place a slight outward bend (or flare) at the end of two opposite outer leaves on each GR-874 connector. This simple mechanical feature insure that the leaves properly position themselves with respect to each other each time you mate two GR-874 connectors. You will notice this also requires you to orient the connectors with a 90 degree turn between them so the leaves with the flair are always opposite leaves with no flair. This wasn't necessary to do for the leaves of the inner conductor. Instead two of the inner leaves are positioned ever so slightly inward closer to the center. This insures the leaves from the other connector (rotated 90 degrees) which our further out from the center will mate perfectly with them. The result is that the outer leaves form a circular pressurized contact with each other and the inner leaves do the same. The circular design with simple mechanical self-alignment insured excellent performance past 7GHz. They are rugged as well, and didn't require any special locking mechanism. GR manufactured numerous adapters, terminators, extenders, power splitters, detectors, slotted lines, tunable filters, etc. with these connectors on them so it quickly became the standard HF connector in the electronics industry.

For more information see the article in the GR Experimenter from 1949 which introduced the GR-874:
https://www.ietlabs.com/pdf/GR_Experimenters/1948/GenRad_Experimenter_Oct_1948.pdf

To see some of the hundreds of things made with GR-874 connectors take a look at this 20 page long excerpt from the GR 1975 catalog:
https://www.ietlabs.com/pdf/Datasheets/874.pdf

General Radio made outstanding products. Few companies make products that ae still in use 75 or 100 years after they were designed. The Variac was one of their designs from 1934. They licensed the design to several other companies but the original design was so perfect that the other manufacturers always followed the same design principles. The Variac has been in widespread use for 85 years. I'll bet that at least 50% of the TekScopes members have one and that it gets used. GR-874 connectors aren't quite that old - only 70 years now - but they too are still in widespread use.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy Thistle
Sent: Tuesday, August 06, 2019 2:45 PM
To: TekScopes@groups.io
Subject: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

Hi All:
Apologies, if this has been covered (there are a lot of posts on 874!).. but the picture on Tekwiki of the GR-874 (the one with the plug facing the viewer... so you can see into it)… well that picture shows two of the leaves of the center conductor, bent in at the corners, and so having little "bendies" barbs, or tangs. (You have to see the picture!).
http://w140.com/tekwiki/wiki/GR-874_connector.
My initial question is… Is that normal, or is the center conductor of the connector damaged? (You can see a bit of those "bendies" on the leaves of the outer conductor, in the picture, too.) My initial guess is the matching, inserter GR-874, after being rotated, and mated, has damaged the insertee? If so, how does the mated pair maintain 50 ohms?
Best regards and wishes.
Roy




--
Dennis Tillman W7PF
TekScopes Moderator

Jim Ford
 

Hi, Dennis.

Interesting to know about GR and the 874 connectors. I'm a bit too young to have seen much GR equipment in use (I'm 54, born in 1965), but I have run across the 874's a few times in my career. Along with the APC 7mm connectors, they are the only genderless RF/microwave connectors I know of. I've avoided both in my garage lab, in favor of SMA, BNC, and type N, since all of those are much more common. Someday I may extend my collection to APC 3.5 mm and 2.92 mm (K connectors) to go to higher frequencies while still remaining mechanically compatible with SMA. Too darned expensive to go to the incompatible 1.85 mm and 1.0 mm (about $1k apiece! Yikes!) I think 40 GHz with the K connectors is a good place to stop!

Regarding the Variac, I don't have one but do have a Staco model 500B autotransformer that I rescued from the dumpster at Raytheon where I work. I haven't used it for anything yet, but someday (in retirement?) I want to use it to work on vacuum tube audio and guitar amplifiers. I remember seeing at least one Variac, along with a very large Tek scope on a cart (maybe a 555?), and a large amount of HP gear, including a Nixie tube frequency counter and a waveguide frequency meter (a bizarre-looking glass cylinder with a big black knob on top), among other waveguide gear in my dad's microwave spectroscopy lab back in the 1970's. I guess growing up with all that cool Tek and HP equipment was part of why I became an EE. I actually started out in biochem in college but quickly switched to EE.

Anyway, I mostly wanted to get in the bit about the Staco autotransformer. IIRC, I saw them on eBay for about $200. Score!

Jim Ford

------ Original Message ------
From: "Dennis Tillman W7PF" <@Dennis_Tillman_W7PF>
To: TekScopes@groups.io
Sent: 8/10/2019 4:55:40 PM
Subject: Re: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

Hi Roy,

The design of the GR-874 is unique (except for its bigger brother) in the electronics industry. It is brilliant design which is why it has lasted so long.
The connectors are hermaphroditic, in other words it has both male and female parts so they can mate to themselves. There is no need for male plugs and female sockets.

To insure the outer leaves are positioned properly with each other it was necessary to place a slight outward bend (or flare) at the end of two opposite outer leaves on each GR-874 connector. This simple mechanical feature insure that the leaves properly position themselves with respect to each other each time you mate two GR-874 connectors. You will notice this also requires you to orient the connectors with a 90 degree turn between them so the leaves with the flair are always opposite leaves with no flair. This wasn't necessary to do for the leaves of the inner conductor. Instead two of the inner leaves are positioned ever so slightly inward closer to the center. This insures the leaves from the other connector (rotated 90 degrees) which our further out from the center will mate perfectly with them. The result is that the outer leaves form a circular pressurized contact with each other and the inner leaves do the same. The circular design with simple mechanical self-alignment insured excellent performance past 7GHz. They are rugged as well, and didn't require any special locking mechanism. GR manufactured numerous adapters, terminators, extenders, power splitters, detectors, slotted lines, tunable filters, etc. with these connectors on them so it quickly became the standard HF connector in the electronics industry.

For more information see the article in the GR Experimenter from 1949 which introduced the GR-874:
https://www.ietlabs.com/pdf/GR_Experimenters/1948/GenRad_Experimenter_Oct_1948.pdf

To see some of the hundreds of things made with GR-874 connectors take a look at this 20 page long excerpt from the GR 1975 catalog:
https://www.ietlabs.com/pdf/Datasheets/874.pdf

General Radio made outstanding products. Few companies make products that ae still in use 75 or 100 years after they were designed. The Variac was one of their designs from 1934. They licensed the design to several other companies but the original design was so perfect that the other manufacturers always followed the same design principles. The Variac has been in widespread use for 85 years. I'll bet that at least 50% of the TekScopes members have one and that it gets used. GR-874 connectors aren't quite that old - only 70 years now - but they too are still in widespread use.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy Thistle
Sent: Tuesday, August 06, 2019 2:45 PM
To: TekScopes@groups.io
Subject: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

Hi All:
Apologies, if this has been covered (there are a lot of posts on 874!).. but the picture on Tekwiki of the GR-874 (the one with the plug facing the viewer... so you can see into it)… well that picture shows two of the leaves of the center conductor, bent in at the corners, and so having little "bendies" barbs, or tangs. (You have to see the picture!).
http://w140.com/tekwiki/wiki/GR-874_connector.
My initial question is… Is that normal, or is the center conductor of the connector damaged? (You can see a bit of those "bendies" on the leaves of the outer conductor, in the picture, too.) My initial guess is the matching, inserter GR-874, after being rotated, and mated, has damaged the insertee? If so, how does the mated pair maintain 50 ohms?
Best regards and wishes.
Roy




--
Dennis Tillman W7PF
TekScopes Moderator


 

Hi Jim,

GR connectors are more common in Europe than in the US where they have been experiencing a slow phase out. SMA is a very inexpensive design with excellent HF performance. Their size is a big plus too. But before SMA came along GR was a reasonably priced way to get good HF performance. BNC cables are unreliable above 1GHz due to the poor tolerances of the connectors and the unreliable quality standards followed by most cable manufacturers who seem to be more concerned with cutting costs to the bone.

A Variac is the most enduring, reliable, and practical, design variation of a autotransformer. GR licensed their Variac design to several other companies. Staco is one I see regularly, Powerstat is another one. There is also GE, Superior Electric, and a company bought the Variac name and named themselves Variac, Inc. They make Variacs themselves.

The design is always identical to the original. Only the details change such as the power rating (300VA, 500VA, 600VA, 1KVA, 2KVA, etc), the voltage rating (120VAC, 240VAC, 440VAC), the frequency its designed for (50Hz, 60 Hz, 400Hz) and the enclosure. Some have meters most do not. New ones these days have digital panel meters.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jim Ford
Sent: Saturday, August 10, 2019 11:13 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

Hi, Dennis.

Interesting to know about GR and the 874 connectors. I'm a bit too young to have seen much GR equipment in use (I'm 54, born in 1965), but I have run across the 874's a few times in my career. Along with the APC 7mm connectors, they are the only genderless RF/microwave connectors I know of. I've avoided both in my garage lab, in favor of SMA, BNC, and type N, since all of those are much more common. Someday I may extend my collection to APC 3.5 mm and 2.92 mm (K connectors) to go to higher frequencies while still remaining mechanically compatible with SMA. Too darned expensive to go to the incompatible 1.85 mm and 1.0 mm (about $1k apiece! Yikes!) I think 40 GHz with the K connectors is a good place to stop!

Regarding the Variac, I don't have one but do have a Staco model 500B autotransformer that I rescued from the dumpster at Raytheon where I work. I haven't used it for anything yet, but someday (in retirement?) I want to use it to work on vacuum tube audio and guitar amplifiers. I remember seeing at least one Variac, along with a very large Tek scope on a cart (maybe a 555?), and a large amount of HP gear, including a Nixie tube frequency counter and a waveguide frequency meter (a bizarre-looking glass cylinder with a big black knob on top), among other waveguide gear in my dad's microwave spectroscopy lab back in the 1970's. I guess growing up with all that cool Tek and HP equipment was part of why I became an EE. I actually started out in biochem in college but quickly switched to EE.

Anyway, I mostly wanted to get in the bit about the Staco autotransformer. IIRC, I saw them on eBay for about $200. Score!

Jim Ford

------ Original Message ------
From: "Dennis Tillman W7PF" <@Dennis_Tillman_W7PF>
To: TekScopes@groups.io
Sent: 8/10/2019 4:55:40 PM
Subject: Re: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

Hi Roy,

The design of the GR-874 is unique (except for its bigger brother) in the electronics industry. It is brilliant design which is why it has lasted so long.
The connectors are hermaphroditic, in other words it has both male and female parts so they can mate to themselves. There is no need for male plugs and female sockets.

To insure the outer leaves are positioned properly with each other it was necessary to place a slight outward bend (or flare) at the end of two opposite outer leaves on each GR-874 connector. This simple mechanical feature insure that the leaves properly position themselves with respect to each other each time you mate two GR-874 connectors. You will notice this also requires you to orient the connectors with a 90 degree turn between them so the leaves with the flair are always opposite leaves with no flair. This wasn't necessary to do for the leaves of the inner conductor. Instead two of the inner leaves are positioned ever so slightly inward closer to the center. This insures the leaves from the other connector (rotated 90 degrees) which our further out from the center will mate perfectly with them. The result is that the outer leaves form a circular pressurized contact with each other and the inner leaves do the same. The circular design with simple mechanical self-alignment insured excellent performance past 7GHz. They are rugged as well, and didn't require any special locking mechanism. GR manufactured numerous adapters, terminators, extenders, power splitters, detectors, slotted lines, tunable filters, etc. with these connectors on them so it quickly became the standard HF connector in the electronics industry.

For more information see the article in the GR Experimenter from 1949 which introduced the GR-874:
https://www.ietlabs.com/pdf/GR_Experimenters/1948/GenRad_Experimenter_O
ct_1948.pdf

To see some of the hundreds of things made with GR-874 connectors take a look at this 20 page long excerpt from the GR 1975 catalog:
https://www.ietlabs.com/pdf/Datasheets/874.pdf

General Radio made outstanding products. Few companies make products that ae still in use 75 or 100 years after they were designed. The Variac was one of their designs from 1934. They licensed the design to several other companies but the original design was so perfect that the other manufacturers always followed the same design principles. The Variac has been in widespread use for 85 years. I'll bet that at least 50% of the TekScopes members have one and that it gets used. GR-874 connectors aren't quite that old - only 70 years now - but they too are still in widespread use.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy
Thistle
Sent: Tuesday, August 06, 2019 2:45 PM
To: TekScopes@groups.io
Subject: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

Hi All:
Apologies, if this has been covered (there are a lot of posts on 874!).. but the picture on Tekwiki of the GR-874 (the one with the plug facing the viewer... so you can see into it)… well that picture shows two of the leaves of the center conductor, bent in at the corners, and so having little "bendies" barbs, or tangs. (You have to see the picture!).
http://w140.com/tekwiki/wiki/GR-874_connector.
My initial question is… Is that normal, or is the center conductor of the connector damaged? (You can see a bit of those "bendies" on the leaves of the outer conductor, in the picture, too.) My initial guess is the matching, inserter GR-874, after being rotated, and mated, has damaged the insertee? If so, how does the mated pair maintain 50 ohms?
Best regards and wishes.
Roy




--
Dennis Tillman W7PF
TekScopes Moderator







--
Dennis Tillman W7PF
TekScopes Moderator

Dale H. Cook
 

On 8/10/2019 7:55 PM, Dennis Tillman W7PF wrote:

General Radio made outstanding products. Few companies make products that ae still in use 75 or 100 years after they were designed.
Dennis is correct. The oldest GR instrument in use on my bench is a Type1231-B Amplifier and Null Detector and its accessory Type 1231-P2 Tuned Circuit, both ca. 1950 (my 1231-B is the early design). They are used as the detector for audio-frequency measurements with my GR Type 1603-A Z-Y Bridge. In the field I frequently use my GR Type 1606-A RF Bridge and Type 1330-A Bridge Oscillator (both ca. 1960) for making impedance measurements on AM broadcast antenna systems. I have many other GR instruments, such as my Type 1602-AB UHF Admittance Meter, that see only occasional use in the field. Over the years I have accumulated a large tackle case of 874 cables, adapters, and other accessories, as well as some NOS 874 connectors for repair purposes. I used one of those NOS connectors several years ago when restoring a GR Type 805-C Standard Signal Generator which someone had butchered by replacing its 874 output connector with an SO-239.

I have owned even older GR instruments - I owned and regularly used, from ca. 1978 to ca. 2000, a GR Type 605-A Standard Signal Generator (ca. 1939), which was replaced by the 805-C. I own some GR decade resistors ca. 1930.

The Variac has been in widespread use for 85 years. I'll bet that at least 50% of the TekScopes members have one and that it gets used.
One of my three is on the bench in a custom enclosure with fusing, metering, and an isolation transformer.

GR-874 connectors aren't quite that old - only 70 years now - but they too are still in widespread use.
In addition to my dozens of GR-made 874 items I have nine Tek-branded 874 items, some of which see occasional use in the shop or the field.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/

Dale H. Cook
 

On 8/11/2019 2:12 AM, Jim Ford wrote:

Along with the APC 7mm connectors, they are the only genderless RF/microwave connectors I know of.  I've avoided both in my garage lab, in favor of SMA, BNC, and type N, since all of those are much more common.
Because I own a number of GR instruments that use 874 output connectors I have many 874 cables as well as many GR between-series adapters to adapt 874 to BNC, N, PL-259/SO-239, and a few others.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/

 

Dale's post reminded me that I neglected to mention that GR made many laboratory standard capacitors, inductors, resistors, and other things. As Dale pointed out so well their instruments are still in use because they were designed to be laboratory standards.

Starting around the 1960s GR became self-conscious about the appearance of their instruments so they modernized them. They are still unique in appearance to this day. The most obvious change was the meters. They abandoned the usual round or square shape of panel meters in favor of a unique almost oval shape. They chose a light gray color scheme for their instruments. The color and shape of their knobs changed as well. As a result it is easy to spot a GR product to this day.

The electronics industry lost a great company when they went out of business.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dale H. Cook
Sent: Sunday, August 11, 2019 4:52 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

On 8/10/2019 7:55 PM, Dennis Tillman W7PF wrote:

General Radio made outstanding products. Few companies make products that ae still in use 75 or 100 years after they were designed.
Dennis is correct. The oldest GR instrument in use on my bench is a Type1231-B Amplifier and Null Detector and its accessory Type 1231-P2 Tuned Circuit, both ca. 1950 (my 1231-B is the early design). They are used as the detector for audio-frequency measurements with my GR Type 1603-A Z-Y Bridge. In the field I frequently use my GR Type 1606-A RF Bridge and Type 1330-A Bridge Oscillator (both ca. 1960) for making impedance measurements on AM broadcast antenna systems. I have many other GR instruments, such as my Type 1602-AB UHF Admittance Meter, that see only occasional use in the field. Over the years I have accumulated a large tackle case of 874 cables, adapters, and other accessories, as well as some NOS 874 connectors for repair purposes. I used one of those NOS connectors several years ago when restoring a GR Type 805-C Standard Signal Generator which someone had butchered by replacing its 874 output connector with an SO-239.

I have owned even older GR instruments - I owned and regularly used, from ca. 1978 to ca. 2000, a GR Type 605-A Standard Signal Generator (ca. 1939), which was replaced by the 805-C. I own some GR decade resistors ca. 1930.

The Variac has been in widespread use for 85 years. I'll bet that at least 50% of the TekScopes members have one and that it gets used.
One of my three is on the bench in a custom enclosure with fusing, metering, and an isolation transformer.

GR-874 connectors aren't quite that old - only 70 years now - but they too are still in widespread use.
In addition to my dozens of GR-made 874 items I have nine Tek-branded
874 items, some of which see occasional use in the shop or the field.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA https://plymouthcolony.net/starcity/radios/





--
Dennis Tillman W7PF
TekScopes Moderator

Dale H. Cook
 

On 8/11/2019 1:36 PM, Dennis Tillman W7PF wrote:

The electronics industry lost a great company when they went out of business.
I agree - I have been collecting and using GR instruments for more than 40 years, and collecting and using HP instruments almost as long. The only Tek instruments that I own are my 453 'scope (second version with the FETs but still using pencil HV rectifiers) and my 1503 TDR (as Scotty said in the Star Trek Next Gen episode "Relics" "no A, B, C, or D"). Mine is the unlettered original 1503 with a CRT, not the (frequently failed or failing) LCD screen used in the later, lettered, versions. I have gotten rid of or am getting rid of almost all of my vacuum tube HP instruments (except my working 434A calorimetric power meter and its parts junker) - most of the HP that I now use is from the '70s, which I use in shop and field. The Tek 453 is the shop scope and the 1503 TDR travels with me for field work. The GR instruments used in the field are used little enough that they live at home.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/

ebrucehunter
 

This discussion of General Radio 874 connectors reminded me of an situation I encountered in the 1960s when my employer acquired a used General Radio VHF signal generator in a nice varnished Mahogany case. Unfortunately it had what turned out to be a General Radio type 774 output connector, instead of an 874, UHF, or type-N.  When I called the GR representative for help, he told me GR still reluctantly made available an adapter from the 774 to the 874 type that was available, but not advertised in the catalog.

The 774-series connectors were the predecessors of the 874-type and best described as a banana plug encased with an outer shield.  They were not hermaphroditic.
The 874 connectors were a quantum leap over their predecessor.  They were very convenient to use, not easily damaged, and showed little wear with use.  And they had a wide range of compatible accessories.  But their undoing began as communications moved to ever higher frequencies. The 874 connectors began to show VSWR and repeatability problems above 6 or 7 GHz or so and were replaced by type-N and SMA connectors for applications above 8 or 10 GHz. 

Nevertheless, for frequencies up to 1 or 2 GHz,  their convenience of use remains unparalleled. 

Bruce Hunter

Dale H. Cook
 

On 8/11/2019 4:08 PM, Bruce Hunter wrote:

The 774-series connectors were the predecessors of the 874-type and best described as a banana plug encased with an outer shield.  They were not hermaphroditic.
The Type 774 connectors were used on many GR instruments from its introduction in 1941 until it was supplanted by the Type 874. The 774 was a constant impedance connector which was used for the generator and detector connections of two of the first instruments using it - the Type 821-A Twin-T Impedance Measuring Circuit and the Type 916-A Radio-Frequency Bridge. About 1951 the lower frequency Type 916-AL was introduced with 874 connectors and at that time the 916-A was changed to 874 connectors. Introduced at that time were two other instruments that would not have worked well (if at all) with the 774 connectors - the Type 1601-A V-H-F Bridge (yes, it was hyphenated in the catalog and manual) and the Type 1602-A U-H-F Admittance Meter (ditto).
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/

Dave Seiter
 

Speaking of the 874 connectors, were the 125 ohm versions ever used for anything unrelated to the 519s, or by anyone outside of Tek?
-Dave

On Sunday, August 11, 2019, 05:12:44 PM PDT, Dale H. Cook <bridgewaterma@...> wrote:

On 8/11/2019 4:08 PM, Bruce Hunter  wrote:

The 774-series connectors were the predecessors of the 874-type and best described as a banana plug encased with an outer shield.  They were not hermaphroditic.

 

Hi Dave,
If I remember correctly the reason for the 125 ohm connectors was because that was the impedance of the vertical deflection plates. The input signal went directly to the plates. So I would guess the answer is no - there was no other use for 125 ohm connectors

To get 125 ohm characteristic impedance the size of the inner conductor has to be different than for a 50 ohm characteristic impedance so Tek made special 50 ohm to 125 ohm adapters. The 50 ohm GR 874 connector was on one end and the 125 ohm GR connector was at the other end. The 50 ohm end was the standard color of all GR connectors. The 125 ohm end was plated with gold. Because of the gold they were quite eye catching and "unique". The entire set of adapters Tek made for the 519 came in a really beautiful mahogany box. I had one of those boxes with most of the 519 adapters. The box, the adapters, and the 519 are now in Barrie Gilbert's collection of scopes.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Seiter
Sent: Monday, August 12, 2019 9:03 AM

Speaking of the 874 connectors, were the 125 ohm versions ever used for anything unrelated to the 519s, or by anyone outside of Tek?
-Dave


On Sunday, August 11, 2019, 05:12:44 PM PDT, Dale H. Cook <bridgewaterma@...> wrote:

On 8/11/2019 4:08 PM, Bruce Hunter wrote:

The 774-series connectors were the predecessors of the 874-type and best described as a banana plug encased with an outer shield. They were not hermaphroditic.


--
Dennis Tillman W7PF
TekScopes Moderator

Dave Seiter
 

Hi Dennis,
Yes, the inner conductor for the 125ohm version is considerably smaller than the normal version.  I've always wondered if there was another use for them because some of the people selling them think they are made from pure gold (apparently).  The box that's on ebay now has been there since at least 2008.  When I was actively looking for them, they were easy to spot from far away at swap meets due to the gold.  If there was a bin of 874s, I always did a quick scan of all of them because just as you occasionally run across a "normal" 874 that is gold plated, I have found 125 ohm versions that are not gold plated.  (I have a "T" connector sitting on the couch next to me which has no gold at all, even though all three ends are 125 ohm).   Also, the oldest 519 I have has no gold plated connectors at all.  Seems odd to use gold plating as a visual key, but I guess if you're buying a 519, it's nice to have some bling instead of colored plastic.
-Dave

On Monday, August 12, 2019, 09:40:29 AM PDT, Dennis Tillman W7PF <@Dennis_Tillman_W7PF> wrote:

Hi Dave,
If I remember correctly the reason for the 125 ohm connectors was because that was the impedance of the vertical deflection plates. The input signal went directly to the plates. So I would guess the answer is no - there was no other use for 125 ohm connectors

To get 125 ohm characteristic impedance the size of the inner conductor has to be different than for a 50 ohm characteristic impedance so Tek made special 50 ohm to 125 ohm adapters. The 50 ohm GR 874 connector was on one end and the 125 ohm GR connector was at the other end. The 50 ohm end was the standard color of all GR connectors. The 125 ohm end was plated with gold. Because of the gold they were quite eye catching and "unique". The entire set of adapters Tek made for the 519 came in a really beautiful mahogany box. I had one of those boxes with most of the 519 adapters. The box,  the adapters, and the 519 are now in Barrie Gilbert's collection of scopes.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Seiter
Sent: Monday, August 12, 2019 9:03 AM

Speaking of the 874 connectors, were the 125 ohm versions ever used for anything unrelated to the 519s, or by anyone outside of Tek?
-Dave


On Sunday, August 11, 2019, 05:12:44 PM PDT, Dale H. Cook <bridgewaterma@...> wrote:

On 8/11/2019 4:08 PM, Bruce Hunter  wrote:

The 774-series connectors were the predecessors of the 874-type and best described as a banana plug encased with an outer shield.  They were not hermaphroditic.


--
Dennis Tillman W7PF
TekScopes Moderator

 

Hi Dave,

Remember Tek gold plated their PC boards until gold skyrocketed in in price in 1972 or 1973 so I think it was an easy way for Tek to "color code" the adapters so engineers would know which way to connect them. It is definitely not solid gold. Even an idiot could tell that by the weight. There would be a very big difference in mass from the non-gold end to the gold end if it were solid gold.

Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Seiter
Sent: Monday, August 12, 2019 4:41 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

Hi Dennis,
Yes, the inner conductor for the 125ohm version is considerably smaller than the normal version. I've always wondered if there was another use for them because some of the people selling them think they are made from pure gold (apparently). The box that's on ebay now has been there since at least 2008. When I was actively looking for them, they were easy to spot from far away at swap meets due to the gold. If there was a bin of 874s, I always did a quick scan of all of them because just as you occasionally run across a "normal" 874 that is gold plated, I have found 125 ohm versions that are not gold plated. (I have a "T" connector sitting on the couch next to me which has no gold at all, even though all three ends are 125 ohm). Also, the oldest 519 I have has no gold plated connectors at all. Seems odd to use gold plating as a visual key, but I guess if you're buying a 519, it's nice to have some bling instead of colored plastic.
-Dave

On Monday, August 12, 2019, 09:40:29 AM PDT, Dennis Tillman W7PF <@Dennis_Tillman_W7PF> wrote:

Hi Dave,
If I remember correctly the reason for the 125 ohm connectors was because that was the impedance of the vertical deflection plates. The input signal went directly to the plates. So I would guess the answer is no - there was no other use for 125 ohm connectors

To get 125 ohm characteristic impedance the size of the inner conductor has to be different than for a 50 ohm characteristic impedance so Tek made special 50 ohm to 125 ohm adapters. The 50 ohm GR 874 connector was on one end and the 125 ohm GR connector was at the other end. The 50 ohm end was the standard color of all GR connectors. The 125 ohm end was plated with gold. Because of the gold they were quite eye catching and "unique". The entire set of adapters Tek made for the 519 came in a really beautiful mahogany box. I had one of those boxes with most of the 519 adapters. The box, the adapters, and the 519 are now in Barrie Gilbert's collection of scopes.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Seiter
Sent: Monday, August 12, 2019 9:03 AM

Speaking of the 874 connectors, were the 125 ohm versions ever used for anything unrelated to the 519s, or by anyone outside of Tek?
-Dave


On Sunday, August 11, 2019, 05:12:44 PM PDT, Dale H. Cook <bridgewaterma@...> wrote:

On 8/11/2019 4:08 PM, Bruce Hunter wrote:

The 774-series connectors were the predecessors of the 874-type and best described as a banana plug encased with an outer shield. They were not hermaphroditic.


--
Dennis Tillman W7PF
TekScopes Moderator







--
Dennis Tillman W7PF
TekScopes Moderator

Bill Morton
 

On Aug 13, 2019, at 08:11, Dennis Tillman W7PF <@Dennis_Tillman_W7PF> wrote:

Hi Dave,

Remember Tek gold plated their PC boards until gold skyrocketed in in price in 1972 or 1973 so I think it was an easy way for Tek to "color code" the adapters so engineers would know which way to connect them. It is definitely not solid gold. Even an idiot could tell that by the weight. There would be a very big difference in mass from the non-gold end to the gold end if it were solid gold.

Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Seiter
Sent: Monday, August 12, 2019 4:41 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] General Radio 874 Connector, inner conductor "bendies"

Hi Dennis,
Yes, the inner conductor for the 125ohm version is considerably smaller than the normal version. I've always wondered if there was another use for them because some of the people selling them think they are made from pure gold (apparently). The box that's on ebay now has been there since at least 2008. When I was actively looking for them, they were easy to spot from far away at swap meets due to the gold. If there was a bin of 874s, I always did a quick scan of all of them because just as you occasionally run across a "normal" 874 that is gold plated, I have found 125 ohm versions that are not gold plated. (I have a "T" connector sitting on the couch next to me which has no gold at all, even though all three ends are 125 ohm). Also, the oldest 519 I have has no gold plated connectors at all. Seems odd to use gold plating as a visual key, but I guess if you're buying a 519, it's nice to have some bling instead of colored plastic.
-Dave

On Monday, August 12, 2019, 09:40:29 AM PDT, Dennis Tillman W7PF <@Dennis_Tillman_W7PF> wrote:

Hi Dave,
If I remember correctly the reason for the 125 ohm connectors was because that was the impedance of the vertical deflection plates. The input signal went directly to the plates. So I would guess the answer is no - there was no other use for 125 ohm connectors

To get 125 ohm characteristic impedance the size of the inner conductor has to be different than for a 50 ohm characteristic impedance so Tek made special 50 ohm to 125 ohm adapters. The 50 ohm GR 874 connector was on one end and the 125 ohm GR connector was at the other end. The 50 ohm end was the standard color of all GR connectors. The 125 ohm end was plated with gold. Because of the gold they were quite eye catching and "unique". The entire set of adapters Tek made for the 519 came in a really beautiful mahogany box. I had one of those boxes with most of the 519 adapters. The box, the adapters, and the 519 are now in Barrie Gilbert's collection of scopes.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Seiter
Sent: Monday, August 12, 2019 9:03 AM

Speaking of the 874 connectors, were the 125 ohm versions ever used for anything unrelated to the 519s, or by anyone outside of Tek?
-Dave


On Sunday, August 11, 2019, 05:12:44 PM PDT, Dale H. Cook <bridgewaterma@...> wrote:

On 8/11/2019 4:08 PM, Bruce Hunter wrote:

The 774-series connectors were the predecessors of the 874-type and best described as a banana plug encased with an outer shield. They were not hermaphroditic.


--
Dennis Tillman W7PF
TekScopes Moderator







--
Dennis Tillman W7PF
TekScopes Moderator