Συντήρηση δυο Ραδιοφωνικών Δεκτών Αμερικανικής Κατασκευής. Η εταιρία Collins των ΗΠΑ είναι μια από τις καλύτερες. Ο Δέκτης αυτός είναι ένα απο τα ποιό επιτυχημένα μοντέλα . Θεωρείται ενα σημείο αναφοράς για όσους γνωρίζουν τα θέμα των Τηλεπικοινωνιών.
Πριν την συντήρηση κατάλαβα οτι χρειάζονται αλλαγη ή πρόσθεση κάποιων υλικών. Αυτα αναζητήθηκαν στο εξωτερικο και αγοράσθηκαν.
Αγοράσθηκαν καινούργιοι πυκνωτές ειδικοί για τα μηχανηματα αυτα αφού παραγγέλθηκαν απο την Γερμανία.
Βρεθηκε το Relay μεταγωγής κεραίας και αγοράσθηκε μεταχειρισμένο καθως και τα βυσματα υποδοχων rf.
Αντικαταστάθηκαν στο ένα οι λυχνιες 26Z5W με διόδους.
Throughout 28 years I am radio-amateur, i gained two used receivers Collins R-390A.
Used them during summer holidays at the wife's (sv7dna) born house, 900 Km south of our home.
Its time to restore them .
The R-390A military shortwave radio receiver was the result of a project undertaken by the U.S. army signal corp in 1954 to replace the existing R-390 receiver then in use. The R-390 had done its job so well that the Corps decided continued use of this type of receiver necessitated an improved, reduced-cost version.There are many references to the R390A in the open literature during this period; a picture of the receiver appeared in the May 1959 issue of the amateur radio magazine QST.
Total production of the R-390A (as determined by the high serial numbers noted) is over 55,000 units. Initial production started in 1955 and ran through approximately 1970, and then was restarted in 1984 by Fowler Industries for Avondale Shipyards. Manufacturers and their approximate production numbers are:
Tuning of the R-390A's radio frequency and intermediate frequency front end is synchronized by means of an ingenious mechanical system of racks, gears, and cams. When the front panel tuning controls are rotated, this system raises and lowers ferrite slugs in and out of the receiver's tuning coils. This ensures that all front-end circuits are tracked, meaning all circuits are tuned to the correct frequency to maintain excellent selectivity and sensitivity. The receiver's construction is modular for easy servicing. Each major area of the receiver is contained in easily removable subassemblies, and these can be repaired or replaced as needs be. Though the R-390A is mechanically and electrically complex, alignment and servicing were designed to follow simplified procedures published by the Signal Corps.
Pictures - videos after Restoration των δεκτών
40 m reception
Am Reception
LSB Reception
εικόνες Μετα την συντήρηση:
Ο δέκτης εχει ακουστική έξοδο 600 Ω και γι αυτό στο Μεγάφωνο χρειάζεται μετασχηματιστής Διαμορφώσεως
Receiver B
CW RECEPTION
ΟΙ ΠΑΡΑΚΑΤΩ ΕΙΚΟΝΕΣ ΕΙΝΑΙ ΠΡΙΝ ΤΗΝ ΣΥΝΤΗΡΗΣΗ
BELOW ARE PICTURES BEFORE RESTORATION
The tr switching missing
too grease
new tubes
cables
decided to ask friend's help .
Είχα και άλλους κάτοικους που κάνανε χρήση των Δεκτών για κατοικία. Δουλεύανε και τότε πάντως..
βλέπετε οτι έχει μπει ένα καθαριστικό υγρό και έχει αφαιθεί για ώρες για να γίνει σε βάθος καθαρισμός
i found co-users of my Collins
wasp's nest
all out for relocation of units
dust grease and fluff
founded original t/r switch (not cheap) before
after
Caps not good needed Recaping
new capacitors RECAPING (not cheap, came from Germany)
tests
Laundry
washing
at the dryer greek sun / στον ελληνικό ήλιο για στέγνωμα/
to be continue
Ευχαριστώ τον κ. Ιωάννη Ιγγλλεζάκη για το ρελε και για όσα έκανε απο πλευράς του.
Read lower more story R-725/URR
CIA's model of R390A
Remember, you can only use AM reception on this type of Dual Diversity. That's because CW or SSB reception requires the BFO to be in operation and the BFO dominates the detectors and spoils the diversity effect. For RTTY reception special TUs were used, like the CV-116 that was designed for diversity RTTY. Diversity CW reception required Tone Keyers.
So, give Dual Diversity reception a try if you can. It's interesting and sometimes beneficial to copy.
R-389/URR - LF Receiver
Πριν την συντήρηση κατάλαβα οτι χρειάζονται αλλαγη ή πρόσθεση κάποιων υλικών. Αυτα αναζητήθηκαν στο εξωτερικο και αγοράσθηκαν.
Αγοράσθηκαν καινούργιοι πυκνωτές ειδικοί για τα μηχανηματα αυτα αφού παραγγέλθηκαν απο την Γερμανία.
Βρεθηκε το Relay μεταγωγής κεραίας και αγοράσθηκε μεταχειρισμένο καθως και τα βυσματα υποδοχων rf.
Αντικαταστάθηκαν στο ένα οι λυχνιες 26Z5W με διόδους.
Throughout 28 years I am radio-amateur, i gained two used receivers Collins R-390A.
Used them during summer holidays at the wife's (sv7dna) born house, 900 Km south of our home.
Its time to restore them .
The R-390A military shortwave radio receiver was the result of a project undertaken by the U.S. army signal corp in 1954 to replace the existing R-390 receiver then in use. The R-390 had done its job so well that the Corps decided continued use of this type of receiver necessitated an improved, reduced-cost version.There are many references to the R390A in the open literature during this period; a picture of the receiver appeared in the May 1959 issue of the amateur radio magazine QST.
Total production of the R-390A (as determined by the high serial numbers noted) is over 55,000 units. Initial production started in 1955 and ran through approximately 1970, and then was restarted in 1984 by Fowler Industries for Avondale Shipyards. Manufacturers and their approximate production numbers are:
- Collins Radio Company 6,363
- Electronic Assistance Corp 15,338 (includes Dittmore Freimuth marked radios)
- Capehart 4,242
- Motorola 14,873
- Stewart Warner 6,631
- Amelco/Teledyne/Imperial 7,958 (these companies were related through acquisitions)
- Fowler Industries 5
Design
The R-390A is a general coverage radio receiver capable of receiving AM, CW, and frequency shift keying signals. Its tuning range is from 500 Khz to 32 mhz, in 32 one-megahertz bands. The circuit is the superheterodyne type, double conversion above 8 MHz, below which triple conversion is used. It employs 26 vacuum tubes (6AK6 x 3, 5654 x 2, 12AU7/5814A x 2, 26Z5W x 2, 3TF7 x 1, 6BA6/5749W x 6, 6C4/6100 x 3, 6DC6 x 1, 0A2 x 1), a larger than normal count for most general-coverage receivers. The receiver weighs 85 pounds and can be operated on 120 volt or 240 volt supplies. It fits neatly into a 10.5 inch-tall standard 19 inch equipment rack.Tuning of the R-390A's radio frequency and intermediate frequency front end is synchronized by means of an ingenious mechanical system of racks, gears, and cams. When the front panel tuning controls are rotated, this system raises and lowers ferrite slugs in and out of the receiver's tuning coils. This ensures that all front-end circuits are tracked, meaning all circuits are tuned to the correct frequency to maintain excellent selectivity and sensitivity. The receiver's construction is modular for easy servicing. Each major area of the receiver is contained in easily removable subassemblies, and these can be repaired or replaced as needs be. Though the R-390A is mechanically and electrically complex, alignment and servicing were designed to follow simplified procedures published by the Signal Corps.
Pictures - videos after Restoration των δεκτών
40 m reception
Am Reception
LSB Reception
εικόνες Μετα την συντήρηση:
Ο δέκτης εχει ακουστική έξοδο 600 Ω και γι αυτό στο Μεγάφωνο χρειάζεται μετασχηματιστής Διαμορφώσεως
Receiver B
CW RECEPTION
ΟΙ ΠΑΡΑΚΑΤΩ ΕΙΚΟΝΕΣ ΕΙΝΑΙ ΠΡΙΝ ΤΗΝ ΣΥΝΤΗΡΗΣΗ
BELOW ARE PICTURES BEFORE RESTORATION
The tr switching missing
new tubes
decided to ask friend's help .
Είχα και άλλους κάτοικους που κάνανε χρήση των Δεκτών για κατοικία. Δουλεύανε και τότε πάντως..
βλέπετε οτι έχει μπει ένα καθαριστικό υγρό και έχει αφαιθεί για ώρες για να γίνει σε βάθος καθαρισμός
i found co-users of my Collins
wasp's nest
all out for relocation of units
founded original t/r switch (not cheap) before
Caps not good needed Recaping
tests
washing
at the dryer greek sun / στον ελληνικό ήλιο για στέγνωμα/
to be continue
Ευχαριστώ τον κ. Ιωάννη Ιγγλλεζάκη για το ρελε και για όσα έκανε απο πλευράς του.
Read lower more story R-725/URR
CIA's model of R390A
Arvin
Industries, Inc. - R-725/URR
Here is the story, from Henry Rogers at the Western Radio Museum here: http://www.radioblvd.com/MilitaryCommunicationsGear.htm
Scroll down...
The R-725/URR is a 1967 Electronic Assistance Corporation-built R-390A receiver that was modified (in 1967) by Arvin Industries, Inc. for the USAF to use in semi-portable radio direction finding systems. Each R-725 receiver had the following modifications installed. First, the standard R-390A IF module was replaced with a new manufacture Series 500 IF module built by Arvin Industries or Servo Electronics. The Series 500 IF module was essentially a R-390 IF module (six IF amplifiers with no mechanical filters) that had minor updates to coax connectors to allow the Series 500 IF module to be installed with no modifications to the R-390A circuitry. However, further design development for the R-725 modification turned up a 60hz modulation problem that required additional modifications. A small chassis is mounted in the main frame space directly in front of the power supply module. This chassis has a 25vac transformer, two resistors and a connector-harness. This was a "hum-bucking" transformer that basically disconnected the VFO tube, the BFO tube and the ballast tube and powered the tube heaters with a "floating" 25vac (not referenced to chassis) and then used the resistive divider connected to B+ to "swamp" the AC with DC. The result was these tube heaters and ballast tube series string operated on +25vdc. To further protect the PTO from 60hz hum pickup, the entire PTO case had a grounded ferrous metal shield installed. The final modification was to the IF Output connector. The larger Series 500 IF module prevented connecting the IF Output cable to the back connector due to lack of clearance. A special "low profile" right-angle coax fitting was installed that allowed the IF Output to be available at the back panel. The contract number for the R-725/URR was DAAB05-67-C-2338 with a total number of receivers modified being less than 300.
The Non-Secret R-725 Story - The purpose of the R-725 mods was for compatibility with military portable direction finders that used four vertical antennae per installation along with three receivers. The DF system used went back to the Bellini-Tosi type of DF set-up that used two crossed loop antennae with a rotating loop inside to create a radio-goniometer. Bellini and Tosi had discovered that crossed loop antennae would "re-radiate" the signal they were receiving within the small field inside the antenna's space. The "re-radiated" signal retained all of the directional properties of the original signal and could be measured for varying signal intensity dependent on direction. The crossed loop antenna size didn't affect the frequency of operation allowing for reduction in the size of DF loops on LW. The original Bellini-Tosi system dated from around 1900 and the system was sold to the Marconi Company around 1907. By the early twenties, vacuum tube amplifiers were being added to increase performance capabilities of the DF antennae systems. The most common B-T DF systems used the crossed loops but some larger systems used the four-square vertical antenna system. This system was developed by Adcock during WWI and because the connections to and from the four square verticals were underground it didn't respond to skywave propagation and allowed ground wave DFing over long distances. The B-T DF and Adcock systems continued to evolve and improve with the systems being used throughout WWII. During WWII, oscilloscope displays began to be used for direction indications. After WWII, larger DF systems continued to be developed up to the mammoth "elephant cage" antennae ("Wullenweber" was the actual name) that were over a thousand feet in diameter and consisted of several "rings" of circular antennae all working to provide accurate DFing over great distances and wide frequency spans. By the 1990s, most of these large arrays were becoming obsolete and nowadays most have been dismantled.
The mechanical filters used in the R-390A resulted in signal path phase shifts that caused errors to show up in the DFing electronics. When used with the four square antennas, the low frequency modulation added via the radio-goniometer interacted with the mechanical filters creating the error. Early versions of this DF set-up had used R-390 receivers and the radio-goniometer was located quite a distance from the receivers to reduce any interference. In the 1960s, the USAF wanted to reduce the size of the entire DF system so it could be towed around on a trailered hut. This meant the radio-goniometer had to be in the same room as the receivers. This was going to require some protection to certain receiver circuits. The R-390 had been out of production for several years, so the solution was to design the new portable system to use modified R-390A receivers that could be easily purchased. Arvin Industries was the main contractor with Servo also doing some rework. The modified receivers would have the Series 500 IF module, essentially a R-390 IF module that was slightly updated to not require any rework to the R-390A receiver it was installed into. That eliminated the mechanical filter phase shift problem. Additionally, with the close proximity to the radio-goniometer, a 60hz hum appeared on the PTO tube filament and that also interfered with the LF modulation of the DF system. A special "hum bucker" chassis was added to the receiver that essentially operated the VFO tube, the BFO tube and the 3TF7 Ballast tube on +25vdc. Also, a grounded ferrous metal shield was added to the PTO housing to prevent hum "pick up." Arvin bought new R-390A receivers in 1967 direct from Electronic Assistance Corporation and the modifications were installed at Arvin. When complete, the receiver was tagged as "R-725/URR." The tags will generally show Arvin Industries as the contractor but sometimes Servo Electronics will be encountered. Arvin ink-stamped a serial number on each Series 500 IF module and when that module was installed into the receiver that same serial number was stamped onto the front panel data plate.
The Secret Project - Was there another purpose that was the "real" reason that the R-725 was created? According to an article that appeared in Electric Radio in January 2006 by Chuck Teeters, there was a "top secret" purpose for the R-725 and the receiver "mods" were primarily created for that "secret" project. The R-725 was a product that resulted from the Cold War jamming that was common between the USA and the USSR. In the mid-to-late 1960s, the NSA, the USAF and the Signal Corps were developing a new system called "Tropicom" that was an upgrade to the antennas and transmitters to improve HF communications for the military. The Tropicom upgrades also included the incorporation of the "F9c" anti-jamming/crypto system. The F9c system used a spread spectrum transmission of digital noise and signal that ran through a digital encrypo-key generator that had 144 stages of looped-feedback that also fed through phase modulators to maintain proper phase relationships of the signal and noise. When recombined at the receive end the signal to noise extracted the signal and left the noise and any jamming attempts far below the signal level. Since the system used spread spectrum, the signal couldn't be detected without the proper combination of equipment and decryption and that left any jamming attempts at just "blind" shots. However, when the F9c was used with a R-390A on the receive end, the phase changes in the mechanical filters interfered with the recombination process and the system didn't work. When used with R-390s with a standard IF amplifier circuit, the F9c system worked fine.
Since the R-390 receivers dated from the early-1950s, there were only a limited supply of those receivers still available and those that were available needed constant maintenance. The ultimate solution was to have new R-390A receivers with newly-built R-390 IF modules installed available for the Tropicom system.
In order to keep the F9c project "secret," the actual use of the R-725 couldn't be known to those outside the Tropicom project. Since there really was the Adcock DF system upgrades that really did need a non-mechanical filter type R-390A, the R-725 was directed to be built for the DF purpose only. However, those running the F9c project had the R-725 order quantity doubled and half of the R-725 receivers were procured for F9c use while the other half went to the DF systems. The secret classification stayed on with the F9c system and it was used for quite a long period with many upgrades over the years. So, even though half of the R-725 receivers were used in direction finders, the other half had a "secret life" used in the anti-jamming/crypto communications world of the NSA, the USAF and the Signal Corps.
Performance - The R-725/URR is very much like listening to a R-390 receiver. The modifications to the VFO-BFO heaters using the "hum-bucker" are not audible. The big change is the Series 500 IF module. With six IF amplifiers, the R-725 has plenty of gain. So much, that most strong signals will push the Carrier Level meter to 70db or 80db and then if the receiver is tuned off of the signal, the meter drops to 20db or less. I have the IF gain reduced by 40%. Audio sounds slightly different than the R-390A with mechanical filters but still there is lots of selectivity and QRM is not a problem. The R-725 is basically like having an R-390 without all of the maintenance headaches.
Scroll down...
The R-725/URR is a 1967 Electronic Assistance Corporation-built R-390A receiver that was modified (in 1967) by Arvin Industries, Inc. for the USAF to use in semi-portable radio direction finding systems. Each R-725 receiver had the following modifications installed. First, the standard R-390A IF module was replaced with a new manufacture Series 500 IF module built by Arvin Industries or Servo Electronics. The Series 500 IF module was essentially a R-390 IF module (six IF amplifiers with no mechanical filters) that had minor updates to coax connectors to allow the Series 500 IF module to be installed with no modifications to the R-390A circuitry. However, further design development for the R-725 modification turned up a 60hz modulation problem that required additional modifications. A small chassis is mounted in the main frame space directly in front of the power supply module. This chassis has a 25vac transformer, two resistors and a connector-harness. This was a "hum-bucking" transformer that basically disconnected the VFO tube, the BFO tube and the ballast tube and powered the tube heaters with a "floating" 25vac (not referenced to chassis) and then used the resistive divider connected to B+ to "swamp" the AC with DC. The result was these tube heaters and ballast tube series string operated on +25vdc. To further protect the PTO from 60hz hum pickup, the entire PTO case had a grounded ferrous metal shield installed. The final modification was to the IF Output connector. The larger Series 500 IF module prevented connecting the IF Output cable to the back connector due to lack of clearance. A special "low profile" right-angle coax fitting was installed that allowed the IF Output to be available at the back panel. The contract number for the R-725/URR was DAAB05-67-C-2338 with a total number of receivers modified being less than 300.
The Non-Secret R-725 Story - The purpose of the R-725 mods was for compatibility with military portable direction finders that used four vertical antennae per installation along with three receivers. The DF system used went back to the Bellini-Tosi type of DF set-up that used two crossed loop antennae with a rotating loop inside to create a radio-goniometer. Bellini and Tosi had discovered that crossed loop antennae would "re-radiate" the signal they were receiving within the small field inside the antenna's space. The "re-radiated" signal retained all of the directional properties of the original signal and could be measured for varying signal intensity dependent on direction. The crossed loop antenna size didn't affect the frequency of operation allowing for reduction in the size of DF loops on LW. The original Bellini-Tosi system dated from around 1900 and the system was sold to the Marconi Company around 1907. By the early twenties, vacuum tube amplifiers were being added to increase performance capabilities of the DF antennae systems. The most common B-T DF systems used the crossed loops but some larger systems used the four-square vertical antenna system. This system was developed by Adcock during WWI and because the connections to and from the four square verticals were underground it didn't respond to skywave propagation and allowed ground wave DFing over long distances. The B-T DF and Adcock systems continued to evolve and improve with the systems being used throughout WWII. During WWII, oscilloscope displays began to be used for direction indications. After WWII, larger DF systems continued to be developed up to the mammoth "elephant cage" antennae ("Wullenweber" was the actual name) that were over a thousand feet in diameter and consisted of several "rings" of circular antennae all working to provide accurate DFing over great distances and wide frequency spans. By the 1990s, most of these large arrays were becoming obsolete and nowadays most have been dismantled.
The mechanical filters used in the R-390A resulted in signal path phase shifts that caused errors to show up in the DFing electronics. When used with the four square antennas, the low frequency modulation added via the radio-goniometer interacted with the mechanical filters creating the error. Early versions of this DF set-up had used R-390 receivers and the radio-goniometer was located quite a distance from the receivers to reduce any interference. In the 1960s, the USAF wanted to reduce the size of the entire DF system so it could be towed around on a trailered hut. This meant the radio-goniometer had to be in the same room as the receivers. This was going to require some protection to certain receiver circuits. The R-390 had been out of production for several years, so the solution was to design the new portable system to use modified R-390A receivers that could be easily purchased. Arvin Industries was the main contractor with Servo also doing some rework. The modified receivers would have the Series 500 IF module, essentially a R-390 IF module that was slightly updated to not require any rework to the R-390A receiver it was installed into. That eliminated the mechanical filter phase shift problem. Additionally, with the close proximity to the radio-goniometer, a 60hz hum appeared on the PTO tube filament and that also interfered with the LF modulation of the DF system. A special "hum bucker" chassis was added to the receiver that essentially operated the VFO tube, the BFO tube and the 3TF7 Ballast tube on +25vdc. Also, a grounded ferrous metal shield was added to the PTO housing to prevent hum "pick up." Arvin bought new R-390A receivers in 1967 direct from Electronic Assistance Corporation and the modifications were installed at Arvin. When complete, the receiver was tagged as "R-725/URR." The tags will generally show Arvin Industries as the contractor but sometimes Servo Electronics will be encountered. Arvin ink-stamped a serial number on each Series 500 IF module and when that module was installed into the receiver that same serial number was stamped onto the front panel data plate.
The Secret Project - Was there another purpose that was the "real" reason that the R-725 was created? According to an article that appeared in Electric Radio in January 2006 by Chuck Teeters, there was a "top secret" purpose for the R-725 and the receiver "mods" were primarily created for that "secret" project. The R-725 was a product that resulted from the Cold War jamming that was common between the USA and the USSR. In the mid-to-late 1960s, the NSA, the USAF and the Signal Corps were developing a new system called "Tropicom" that was an upgrade to the antennas and transmitters to improve HF communications for the military. The Tropicom upgrades also included the incorporation of the "F9c" anti-jamming/crypto system. The F9c system used a spread spectrum transmission of digital noise and signal that ran through a digital encrypo-key generator that had 144 stages of looped-feedback that also fed through phase modulators to maintain proper phase relationships of the signal and noise. When recombined at the receive end the signal to noise extracted the signal and left the noise and any jamming attempts far below the signal level. Since the system used spread spectrum, the signal couldn't be detected without the proper combination of equipment and decryption and that left any jamming attempts at just "blind" shots. However, when the F9c was used with a R-390A on the receive end, the phase changes in the mechanical filters interfered with the recombination process and the system didn't work. When used with R-390s with a standard IF amplifier circuit, the F9c system worked fine.
Since the R-390 receivers dated from the early-1950s, there were only a limited supply of those receivers still available and those that were available needed constant maintenance. The ultimate solution was to have new R-390A receivers with newly-built R-390 IF modules installed available for the Tropicom system.
In order to keep the F9c project "secret," the actual use of the R-725 couldn't be known to those outside the Tropicom project. Since there really was the Adcock DF system upgrades that really did need a non-mechanical filter type R-390A, the R-725 was directed to be built for the DF purpose only. However, those running the F9c project had the R-725 order quantity doubled and half of the R-725 receivers were procured for F9c use while the other half went to the DF systems. The secret classification stayed on with the F9c system and it was used for quite a long period with many upgrades over the years. So, even though half of the R-725 receivers were used in direction finders, the other half had a "secret life" used in the anti-jamming/crypto communications world of the NSA, the USAF and the Signal Corps.
Performance - The R-725/URR is very much like listening to a R-390 receiver. The modifications to the VFO-BFO heaters using the "hum-bucker" are not audible. The big change is the Series 500 IF module. With six IF amplifiers, the R-725 has plenty of gain. So much, that most strong signals will push the Carrier Level meter to 70db or 80db and then if the receiver is tuned off of the signal, the meter drops to 20db or less. I have the IF gain reduced by 40%. Audio sounds slightly different than the R-390A with mechanical filters but still there is lots of selectivity and QRM is not a problem. The R-725 is basically like having an R-390 without all of the maintenance headaches.
IF
Creating an Authentic Arvin R-725/URR
I wasn't really looking for another project but when
nearly all of
the parts turned up in a trade, well,...I couldn't help myself.
Finding the
Parts - I received an e-mail from an audiophile-collector friend of mine asking if I'd be interested
in purchasing all of his R-390A parts. There was a main frame with most of the
modules, another RF deck, an Audio deck, PS deck, PTO and a front panel,
all for $100. It sounded like a good deal so I went over and picked them
up. When I got the parts home and closely inspected them I discovered
that the main frame was a '67 EAC that had the R-725 mods installed. The
main frame still had the Arvin Series 500 IF module installed. The Series 500
modules were built
by Arvin specifically for the R-725/URR.
Essentially, the Series 500 IF deck is just like the IF
deck used in the R-390. Six stages of IF amplification and no mechanical
filters. The original R-390 IF deck used BNC connectors for input and
output but the R-390A used BNC Junior connectors. The Series 500 uses
BNC Junior connectors to match the R-390A and also the new versions
performed any other changes necessary to make the Series 500 just a
"drop in" conversion for the R-390A.
Among the other R-390A parts was a Cosmos PTO that had a
ferrous metal shield installed around the outer shield-can. There was
also a mod to the PTO that had an extra wire exiting from the PTO tube
socket area. Another part that was included (but wasn't installed in the
main frame) was a small chassis with a
25vac transformer mounted on top and a couple of resistors underneath.
Unfortunately, someone had severely damaged the R-725
main frame. One side looked like it had been hit with an axe. Some of
the harnesses had been "chopped" to remove their Amphenol connectors.
The front panel was missing. The Veeder-Root counter was missing.
Luckily, the special added harness for the addition of the small
25vac transformer chassis was still present although it had been cut for
some reason. At least the harness was all there but bifurcated.
I was missing the correct data plate since the original
front panel was missing from the junk R-725 main frame. In early
February 2018, I received a data plate for an Arvin R-725 from Moe Sellali
CN8HD/W9, in Chicago, who is an ardent R-725 enthusiast. Moe told me
that my Series 500 IF module should have a serial number ink-stamped on
the rear of the chassis. According to Moe, when Arvin completed the R-725 mods to each '67 EAC
R-390A, this was the serial number that was stamped on the front panel
data plate. My Series 500 was stamped "074" so Moe sent me the R-725
data plate with "74" as the serial number. >>>
photo : The Arivn R-725/URR built from the 1967 EAC R-390A SN: 974 with the installation of an Arvin Series 500 IF deck,
the hum bucker chassis, the special PTO, IF output conx and the Arvin SN: 74 data plate.
From the top, the most apparent R-725 addition is the Series 500 IF
module. Note how the input and output coaxial cables connect to the
mounting bracket for the Meter and IF Gain potentiometers. Also, note
that the rear panel IF output requires a special right-angle coaxial
fitting with the cable routed to J14 on the rear left corner. Also, the Amphenol power
connector is turned 90 degrees from the standard R-390A IF deck.
Purpose of the
R-725 Modifications - For Adcock Direction Finders - or - Was that just
a Cover Story?
- The usual purpose that is given for the R-725 mods was for compatibility with military
portable direction finders that used four vertical antennae per installation
along with three receivers. The DF system used went back to the Bellini-Tosi
type of DF set-up that used two crossed loop antennae with a rotating
loop inside to create a radio-goniometer. Bellini and Tosi had
discovered that crossed loop antennae would "re-radiate" the signal they
were receiving within the small field inside the antenna's space. The
"re-radiated" signal retained all of the directional properties of the
original signal and could be measured for varying signal intensity
dependent on direction. The crossed loop antenna size didn't affect it
frequency of operation allowing for reduction in the size of DF loops on
LW. Of course, the original Bellini-Tosi
system dated from around 1900 and the system was sold to the Marconi Company
around 1907. By the early twenties, vacuum tube amplifiers were being
added to increase performance capabilities of the DF antennae systems. The
most common B-T DF systems used the crossed loops but some larger
systems used the four-square vertical antenna system and a rotational
loop (the goniometer) within the square. This system was
developed by Adcock during WWI and because the connections to and from the four square verticals were underground it didn't
respond to skywave propagation and allowed ground wave DFing over long
distances. The B-T DF and Adcock systems continued to evolve and improve
and the systems were used
throughout WWII. During WWII, oscilloscope displays began to be used for
direction indications. After WWII, larger DF systems continued to be
developed up to the mammoth "elephant cage" antennae
("Wullenweber" was the actual name) that were over a
thousand feet in diameter and consisted of several "rings" of circular
antennae all working to provide accurate DFing over great distances and
wide frequency spans. By the 1990s, most of these large arrays were
becoming obsolete and nowadays most have been dismantled.
The mechanical filters used in the R-390A resulted in
signal path phase shifts that caused errors to show up in the DFing
electronics. When used with the four square
antennas, the low frequency modulation added via the radio-goniometer
interacted with the mechanical filters creating the error. Early
versions of
this DF set-up had used R-390 receivers and the radio-goniometer was
located quite a distance from the receivers to reduce any
interference. In the 1960s, the USAF wanted to reduce the size of the
entire DF system so it
could be towed around on a trailered hut. This meant the
radio-goniometer
had to be in the same room as the receivers. This was going to require
some protection to certain receiver circuits. The R-390 had been out
of
production for several years, so the solution was to design the new
portable system to use modified R-390A receivers that could be easily
purchased. Arvin Industries was the main contractor with Servo also
doing some rework. The modified receivers would have the Series 500 IF
module, essentially a R-390 IF module that was slightly updated to not
require any rework to the R-390A receiver it was installed into. That
eliminated the mechanical filter phase shift problem. Additionally,
with
the close proximity to the radio-goniometer, a 60hz hum appeared on
the PTO tube
filament and that also interfered with the LF
modulation of the DF system. A special "hum bucker" chassis was added
to the receiver
that essentially operated the VFO tube, the BFO tube and the 3TF7
Ballast tube on +25vdc. Also, a grounded ferrous metal shield was
added
to the PTO housing to prevent hum "pick up."
Arvin bought new R-390A receivers in 1967 from Electronic Assistance
Corporation and the modifications were installed and, when complete,
the
receiver was tagged as "R-725/URR." The tags will generally show Arvin
Industries as the contractor but sometimes Servo will be encountered.
The quantity of R-725/URR receivers needed by the USAF was fairly
small
(less than 300, according to Moe) and thus today the R-725 is seldom
encountered.
Contact number on the R-725/URR was DAAB05-67-C-2338.
However, was there another purpose that was the "real"
reason that the R-725 was created? According to an article that appeared
in Electric Radio in January 2006 by Chuck Teeters, there was a "top secret" purpose
for the R-725 and the receiver "mods" were initially created for that
"secret" project. The R-725 was a product resulting from the Cold War
jamming that was common between the USA and the USSR. In the mid-to-late
1960s, there was a new system that was being
developed called "Tropicom" that was an upgrade to the antennas and
transmitters to improve HF communications for the military. The upgrades
also included the incorporation of the "F9c" anti-jamming/crypto
system. The F9c system used a spread spectrum transmission of digital
noise and signal that ran through a digital encrypo-key generator that
had 144 stages of looped-feedback that also fed through phase modulators
to maintain proper phase relationships of the signal and noise. When
used with a R-390A on the receive end, the phase changes in the
mechanical filters interfered with the recombination process and the
system didn't work. When used with R-390s with a standard IF amplifier
circuit, the F9c system worked fine. Since the R-390 dated from the
early-1950s, there was only a limited supply of those receivers still
available and those that were available needed constant maintenance. The
ultimate solution was to have new R-390A receivers built with new-build R-390 IF
modules installed.
In order to keep the F9c project "secret," the actual
use of the R-725 couldn't be known to those outside the project. Since
there really was the Adcock DF system upgrades that really did need a
non-mechanical filter type R-390A, the R-725 was directed to be built
for the DF purpose only. However, those running the F9c project had the
R-725 order quantity doubled and half of the R-725 receivers were
procured for F9c use while the other half went to the DF systems. The
secret classification stayed on with the F9c system and it was used for
quite a long period with many upgrades over the years. So, even though
half of the R-725 receivers were used in direct finders, the other half
had a "secret life" used in the anti-jamming/crypto communications world
of the NSA, USAF and the Signal Corps.
Testing the
R-390A with a Series 500 IF Module - With the donation of the Arvin R-725 data plate it
looked like I had all of the parts to build-up a R-725 if I could supply
a complete 1967 EAC R-390A. According to Moe, when Arvin built-up the
R-725 receivers they purchased new '67 EAC R-390As direct from EAC to
fulfill the contract, thus all Arvin R-725s are converted '67 EAC R-390A
receivers. I decided to use my '67 EAC SN: 974 R-390A because this receiver
had recently been partially "cannibalized" to complete another EAC R-390A. I
needed to replace a defective RF transformer on the 2-4mc antenna stage
and do some minor alignments. Luckily, the "junk" R-725 RF deck supplied a good RF
transformer. The first step was to check out and test the Series 500
IF module. One of the IF
transformer cans was severely dented and needed "body work" to correct.
All of the tubes were missing. I checked over the underneath and all
components appeared to be in good shape. I gave the Band Width switch a DeOxit
treatment. I needed tubes and tube shields. I found all of the tubes in
my tube storage. The shields were "borrowed" from the EAC IF
deck as was the 3TF7. The Series 500 is a "tight fit" but it does
fit (see above photo.) The chassis is somewhat longer so the captive screws are located on
the chassis rather than on the flange. The Band Width and BFO shafts are
shorter than on the standard IF deck. The input and output coax
connectors are in a different location but the cables reach easily.
There is no clearance for the rear IF output cable as it is directly
behind one of the 12AU7 tubes. The junk R-725 main
frame even
had the rear IF output connector totally removed. A special connector is
required for the IF output on the R-725 conversion. The Amphenol
connector has to be turned 90 degrees but everything lines up and there
is ample flexibility to allow for this connection.
With power applied, everything came up as expected. The
first thing noticed was that the IF Gain must have been at "maximum" -
it was. After some testing and listening, I reduced the IF gain by about
50 percent. This provided ample IF gain and much lower noise levels.
Carrier Level was adjusted on 15mc to zero with the antenna
disconnected. BFO was zeroed. I didn't do a 455kc IF alignment since
this was just a "check out" but the IF deck already seemed to be
performing better than expected.
Dual
Space Diversity Operation with the R-390A Receivers
If you're lucky enough to own two R-390A
receivers and have room for widely separated antennas, you can easily set
up the pair to operate in Dual Space Diversity. Good separation of the
antennas would be at least one wavelength at the frequency of operation but
usable diversity effect can usually be obtained with closer spacing if
necessary. Space Diversity assumes you will be using two similarly
polarized antenna and are relying only on the phase differences of the
radio wave based on the spacing of the antennas. You can also try "Polar
Diversity" which relies on a vertical antenna for one receiver and a
horizontal antenna for the second receiver. Polar Diversity doesn't
require that the two antennas be separated by great distances and
assumes that there will be a benefit from the reception of two different
polarizations of the incoming radio wave. This assumes that some
splitting and rotation of the
radio wave will occur as it propagates through the ionosphere and is
returned to earth. Generally, space diversity helps with fading signals
and polar diversity helps with phase distortion due to wave rotation.
With either method of Dual Diversity reception, the receiver set-up
is the same. You will be connecting the DIODE LOAD from each receiver
together. The receiver that you plan on operating as the "master" will
have to have the DIODE LOAD terminals jumped while the "slave" receiver
doesn't have the terminals jumped. The "slave" receiver is only
operating to the detector stage and its audio output is not used. You
can connect 500 ohm resistors across the LINE AUDIO and the LOCAL AUDIO
on the "slave" receiver. You will also have to install the jumps to
connect AGC DIV terminals together on each receiver. You will also have
a wire connecting the AGC DIV from each receiver together. A speaker on
the LOCAL AUDIO is only required on the "master"
receiver. To listen to just the "slave" receiver, turn the RF GAIN on
the "master" receiver to 0 and what you hear thru its speaker is the
"slave" receiver. Also, if you want to listen to just the "master"
receiver, turn the "slave" receiver's RF GAIN to 0 and what
you hear thru the speaker is the "master" receiver only. With both
receivers operating and connected to their respective antennas, tune in
a strong shortwave broadcast signal. Have both receivers' RF GAIN set to about 8.
Don't set the RF GAIN on either receiver to "full on" (10) or each
receiver will "fight" the other one for control of the AGC line. By alternately reducing the RF GAIN of each receiver
to 0 you should be able to end up with both
receivers tuned exactly to the signal. Once the SW BC signal is tuned in
on each receiver you will need to "balance" the RF GAINs. Slowly
increase the RF GAIN on the each receiver alternately to the point where
you see the CARRIER LEVEL meter showing some response. Adjust the RF
GAIN on each receiver until you have the highest CARRIER LEVEL readings
on each receiver without one receiver or the other "overloading" the AGC
line. When "overloading" occurs the CARRIER LEVEL meter on one receiver
will drop much lower in its reading and with a reduction in the RF GAIN
of the other receiver you'll see the meter reading jump back up. By
"balancing the receivers" you get the best diversity response and the
best sensitivity. You will note that the two receiver's CARRIER LEVEL
meters will react differently since each receiver is responding to a
phase difference in the radio wave based on the separation of the
antennas. You should see deep fades that cause one CL meter dip while the other
receiver's meter remains
steady.
You should also see a reduction in phase distortion if you are using the
polar diversity set up. Remember, you can only use AM reception on this type of Dual Diversity. That's because CW or SSB reception requires the BFO to be in operation and the BFO dominates the detectors and spoils the diversity effect. For RTTY reception special TUs were used, like the CV-116 that was designed for diversity RTTY. Diversity CW reception required Tone Keyers.
So, give Dual Diversity reception a try if you can. It's interesting and sometimes beneficial to copy.
R-389/URR - LF Receiver
Basic Description -
Electronics - Built along some of the same lines as the
famous R-390 receiver, the Collins R-389 is essentially the LF companion
receiver of the R-390. The receiver tunes from 15kc to 500kc in one tuning range and
500kc to 1500kc in the second tuning range. The R-389 uses very complex
methods, both electronic and mechanical, to achieve its complete MW, LF
and VLF coverage while still utilizing a 455kc IF. The receiver uses 36
tubes within five modules that interconnect and are mounted within the
main frame. The 15kc to 500kc tuning range utilizes five
permeability-tuned RF bands. The 500kc to 1500kc tuning range utilizes
two permeability-tuned RF bands. The motor-driven band switching occurs seamlessly as
the receiver is tuned from the lowest to the highest frequency within
the two tuning ranges.
Two RF amplifiers are used and the first conversion mixes the
incoming RF signal frequency with the VFO (470kc to 1955kc output f)
plus the 10.455mc Crystal Oscillator (8.5mc to 9.985mc resulting f)
to achieve a 10mc IF. The second conversion mixes the 10mc IF with the
same 10.455mc Crystal Oscillator to achieve the 455kc IF. This double
conversion scheme was to allow complete coverage from 15kc to 1500kc
with no gaps in the frequency coverage. Additionally, since the two
mixer stages are 180 degrees out of phase, any drift within the
conversion mixers is cancelled leaving only the VFO drift. This is
similar to how the "drift-cancelling" Wadley Loop operates.
From the second mixer circuit on, the R-389 utilizes the same modules
that are found in the R-390. That would be the six-stage IF module, the
two channel audio and electronic voltage regulator circuit module and
the power supply module. Although the PTO (VFO)
looks exactly like that found in the R-390, it's very different inside
and tunes (in two ranges) from 470kc to 1955kc.
More Details - Physically, the R-389 is the same dimensions as the R-390 and will fit into the CY-917 or CY-979 table cabinets. If installed into a table cabinet, the top and bottom covers should be removed. The receiver weighs 82 pounds but, for easier moving (e.g., up or down stairs,) the power supply and AF module can easily be removed and then the receiver weighs around 65 pounds.
Two antenna connectors are available. Balanced input for 125 ohms input impedance from dipoles or other balanced antennae. Balanced is connected to the primary winding of each antenna coil. Unbalanced input is for random length wire antennae. This input is capacitively-coupled through a .01uf capacitor to the RF amplifier coils. The Unbalanced input impedance is not specified but is probably fairly high assuming that end-fed wires were probably the design target Z. The Balanced input utilizes a "Twin-ax" two-pin coaxial connector and the Unbalanced input utilizes a "C-type" coaxial connector. As mentioned, no antenna trimmer is provided so the antenna impedance should be somewhat matched to the particular antenna input used.
Both audio outputs, Local Audio and Line Audio, are 600 Z ohm outputs and can provide about 500mW on Local and about 10mW on Line. The phone jack doesn't disconnect the audio output (LOCAL) from its respective load. There is a series resistor and a load resistor to the PHONES jack to keep the audio level (5mW) from over-driving the headset if the proper 600 Z phones are used.
The AC power connector is a four-pin military connector that is keyed and held in place with a central screw that has a fold-down, wing-type handle. There are at least two different types that fit,...sort of. The original (CX-1358/U cable + connector PN) connector has a small round cylinder-shaped housing with a cable exit tube on the side. This type will fit in almost any orientation and can be used if the receiver is installed into a table cabinet.
There is also a large square housing with the triangular top type that will only fit in one orientation that won't interfere with the terminal strip or the fuse housing. Although this later and larger connector will fit and can be used, it isn't the original type.
More Details - Physically, the R-389 is the same dimensions as the R-390 and will fit into the CY-917 or CY-979 table cabinets. If installed into a table cabinet, the top and bottom covers should be removed. The receiver weighs 82 pounds but, for easier moving (e.g., up or down stairs,) the power supply and AF module can easily be removed and then the receiver weighs around 65 pounds.
Two antenna connectors are available. Balanced input for 125 ohms input impedance from dipoles or other balanced antennae. Balanced is connected to the primary winding of each antenna coil. Unbalanced input is for random length wire antennae. This input is capacitively-coupled through a .01uf capacitor to the RF amplifier coils. The Unbalanced input impedance is not specified but is probably fairly high assuming that end-fed wires were probably the design target Z. The Balanced input utilizes a "Twin-ax" two-pin coaxial connector and the Unbalanced input utilizes a "C-type" coaxial connector. As mentioned, no antenna trimmer is provided so the antenna impedance should be somewhat matched to the particular antenna input used.
Both audio outputs, Local Audio and Line Audio, are 600 Z ohm outputs and can provide about 500mW on Local and about 10mW on Line. The phone jack doesn't disconnect the audio output (LOCAL) from its respective load. There is a series resistor and a load resistor to the PHONES jack to keep the audio level (5mW) from over-driving the headset if the proper 600 Z phones are used.
The AC power connector is a four-pin military connector that is keyed and held in place with a central screw that has a fold-down, wing-type handle. There are at least two different types that fit,...sort of. The original (CX-1358/U cable + connector PN) connector has a small round cylinder-shaped housing with a cable exit tube on the side. This type will fit in almost any orientation and can be used if the receiver is installed into a table cabinet.
There is also a large square housing with the triangular top type that will only fit in one orientation that won't interfere with the terminal strip or the fuse housing. Although this later and larger connector will fit and can be used, it isn't the original type.
Unlike most other LF and VLF receivers, the R-389 doesn't have any fixed-circuit audio restrictions within the audio module other than the switch-selected Broad-Medium-Narrow. Selecting Broad results in a fairly wide audio bandwidth. Medium is shaped for voice with noisy conditions and Narrow is a bandpass filter at 800hz for CW. The IF bandwidth can be restricted down to 100hz. Both 100hz and 1000hz IF bandwidths use a crystal filter that's onboard the IF module. The 2kc, 4kc and 8kc IF bandwidths are determined by the IF transformers and Q-resistor set-up. For static bursts and other types of atmospheric noise, the dual positive-negative noise limiter is available. When tuning in the AM BC range, the receiver's bandwidth can be increased to 8kc and BROAD and, with no other specific audio restrictions, the resulting audio isn't too bad. However, the audio is more-or-less communications-grade audio so don't expect high fidelity because it isn't. Most listening on LW will usually be using a headset. Most listening on the AM-BC band will be on loudspeaker.
Only one contract for R-389 receivers, Order 14214-PH-51-93, was issued in 1951. Total build was 856 receivers.
Rebuild is Necessary - After using the R-389 for a few weeks it's become apparent that this receiver has not been "gone through" in decades. There apparently was some minor work performed about ten years ago that involved the meters and the dial bezel. However, no thorough inspection or any rework or alignments have been performed for quite a long time. Sensitivity is poor, not even close to spec (2uv.) The motor-drive sometimes "bogs-down" indicating either poor mechanical alignment or lubrication problems (too much grease, as it turned out.) Most of the worm gears and shafts that require lubrication are located under the RF module which has to be removed to perform the lube job. Per the manual, any lubrication should be very light coatings applied with a paint brush with the excess removed afterward. So, as this project gets started I will insert additions regarding the progress here in this section of the R-390A webpage.
