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 Post subject: Need help identifying military HF transceiver
PostPosted: Mar Sun 10, 2019 2:55 pm 
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Joined: Jan Mon 28, 2013 9:35 pm
Posts: 1460
Location: Santa Rosa, CA
I've owned this radio for many years now and despite asking
just about everyone that knows something about military radios,
have been unable to identify the model or manufacturer.

Some details;
All solid state with LED display, synthesized
freq range approx 1 MC to 28 MC
Modes include AM, FSK, chirp, SSB, CW and FM
transmitter only puts out a few watts, mic input on panel
originally 115vac, 400 Hz (I've put in a 60 Hz transformer)
no hint of manufacturer or even where an ID plate might have been

While it works the sensitvity is poor and audio distorted so hoping
to find a manual. Thats why I need to identify what the model number is.
TIA
Steve W6SSP


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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Mon 11, 2019 1:06 pm 
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Someone removed the military ID plate? I would think that would be a mandatory specification for a mil set. A photo of the internals might help identify a possible maker in some cases.

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Tue 12, 2019 1:34 pm 
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This may be a commercial rig....

Press Wireless?

...Jim

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Tue 12, 2019 9:30 pm 
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Location: Houston, texas
There should be date codes on some of the components.
You still have that 400Hz transformer? There just might be a model number on that that the vendor might tell you who it was made for


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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Wed 13, 2019 2:18 am 
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Location: Santa Rosa, CA
I have the 400 Hz power transformer but no clues of who made that
either. As I had mentioned not only is there no ID plate but no hint that
there ever was one such as glue, faded paint or screw holes. I've looked
inside and out but can find no clues there either.

Sure there are date codes on the components but that won't tell
me much except about when it was made.

And this looks like a production unit, not a prototype.

Still hoping someone recognizes it. A friend mentioned it appears to
be made the same way the T-368 is so looking at that now.
Steve

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Wed 13, 2019 4:40 am 
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Location: Norfolk, VA
It's certainly not any ARC-, ART-, GRC- or GRT- prefixed unit that I've ever seen. A peek inside will tell - 13499 anywhere, and it's Collins. The receiver frequency "window" looks very Collins-like to me. I did Comm-Nav in two tours, and have seen quite a bit. Being at a MAC hub gave me a peek at what the USAF was using too. I've never seen anything like your transceiver.

Could be a trainer, a Commercial Aviation unit, purpose-built for NASA, or even for maritime use. Heck, even some dirigibles were HF equipped for over-ocean comms.

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Wed 13, 2019 1:13 pm 
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I might be wrong, but wasn't 400 Hz used in aircraft?

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Wed 13, 2019 5:51 pm 
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Les Locklear wrote:
I might be wrong, but wasn't 400 Hz used in aircraft?


Yes, and also in some US Navy maritime (ships use) stuff - it allowed a smaller parts footprint. It's not cut-and-dry as to actual use with 400Hz powered military electronics.

Maritime-only stuff was simply 60Hz.

Dual use stuff was either 400Hz, or run off a 28V converter-rectifier. The UPX-72 R/T was the same APX-72 R/T used in aircraft - same 400Hz supply, although many ships ran their transponder off 28V. We had a ARC-159 UHF radio on the bridge of the Forrestal - run off 28V. It replaced an older ARC-51A that ran on.....400Hz. Any aviation-capable ship is going to have a 400Hz Generator.

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Wed 13, 2019 6:08 pm 
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The use of 400Hz for electrical devices in planes reduces weight dramatically. Most of you have seen the difference between w 25Hz transformer and a 60Hz transformer. At 400Hz the amount of iron needed in transformers and motors is reduced by a factor of 7 to 8 of what is needed at 60Hz. Every piece of AF AC equipment I have had has been 400Hz, except for bench equipment. I think the Navy also used some, but all of the shipboard equipment I have had was 60Hz. In the Army, the only 400Hz equipment I know of was in Nike missile batteries. I think most civilian aircraft AC has been 400Hz until the last few decades.

This unit is puzzling. The only untagged military style equipment I have run into has been black radios, but they are at least marked with a manufacturer and model number somewhere. State Department equipment was a mixed bag, but I never saw any 400Hz radios. Based on my experience, my guess is a 1970s era civilian aircraft radio. However, by then, most didn't look like bench or 19 inch rack equipment.

All we have to go on is the face of the radio. The knob style doesn't ring any bells and the meter hole is an odd shape, but I don't recall seeing it elsewhere.

John


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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Fri 15, 2019 2:16 am 
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While I was looking at the use of knobs as clues on this transceiver last night, I noticed something I have rarely run into- CHIRP. FM CHIRP to be precise. The theory appeared in the early 1950s.

I think it was first applied to RADAR around 1960. I think the Air Force first used it in RADAR in the mid 1960s. I learned of it in a military RADAR class in the early 1970s. As used in RADAR in its early days, it was a sweep signal. The RADARS used some number of specific channels within the sweep. The improvement in range was multiplied by the number of channels used, which was a huge improvement. I got disconnected from RADAR issues in the 1970s, but I ran into it again around 2008. I had a neighbor who managed development of the AEGIS RADAR through its shipboard testing phase, which ended just a few years ago. Through him, I was reintroduced to CHIRP.

I don't think this transceiver has anything to do with RADAR, but at least 2 other uses are made of it, one is within spread-spectrum technology. The other is a form of FM radio communication. Besides the increased range the signal is also less susceptible to jamming. I think the FM communication aspect grew out of communication needs within NASA, not to be confused with the military Commercially Hosted Infrared Project.

CHIRP seems to be clue to follow, as I don't think much of that type of equipment exists.

This is a related use of CHIRP:

https://pdfs.semanticscholar.org/0078/45f372f849c6bb24731eba80c7a568d01a40.pdf


John


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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Fri 15, 2019 3:56 am 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: Norfolk, VA
Superretrodyne wrote:
The use of 400Hz for electrical devices in planes reduces weight dramatically. Most of you have seen the difference between w 25Hz transformer and a 60Hz transformer. At 400Hz the amount of iron needed in transformers and motors is reduced by a factor of 7 to 8 of what is needed at 60Hz. Every piece of AF AC equipment I have had has been 400Hz, except for bench equipment. I think the Navy also used some, but all of the shipboard equipment I have had was 60Hz. In the Army, the only 400Hz equipment I know of was in Nike missile batteries. I think most civilian aircraft AC has been 400Hz until the last few decades.

This unit is puzzling. The only untagged military style equipment I have run into has been black radios, but they are at least marked with a manufacturer and model number somewhere. State Department equipment was a mixed bag, but I never saw any 400Hz radios. Based on my experience, my guess is a 1970s era civilian aircraft radio. However, by then, most didn't look like bench or 19 inch rack equipment.

All we have to go on is the face of the radio. The knob style doesn't ring any bells and the meter hole is an odd shape, but I don't recall seeing it elsewhere.

John


Most Navy "equipment specific" aviation support equipment (read:bench testers/bench equipment) were 400Hz - because they also provided power to the Unit Under Test, which was........ 400Hz powered, just as in the aircraft. This worked well except for the bench cooling fans - most were "whiney" 400Hz units that would drive you nuts after even a few minutes. :x

Again, 400Hz equipment is almost always an enigma, and except for the obvious, not a real clue, as it could be installed anywhere 400Hz was available - Shore, Air, Shipboard (Aviation-capable, which is 75% of the Navy). Those using 400Hz power:

Civil Aircraft
Commercial Aircraft
Shore Stations, especially those with an airfield or maintenance facility
Aviation Maintenance Training Facilities
Military Aircraft
ATC facilities
Simulators and Trainers
Aviation Capable Naval Ships
Civil Maritime, Aviation capable (includes oil platforms, and anything else that can land a helo)

I can think of only one tester that didn't connect to 400Hz - the AIC-14 Intercommunication Test set (AIM-3), as the AIC amps and controls were mostly 28V bus.

Military Aviation HF was used mainly for over-ocean and over-the-horizon comms, so whatever it;s installed in was usually a long-haul or command and control aircraft.

That said, I think the unit above was either commercial, black-ops, or for low-rate production, non-NATO use, as in a refueling tanker, or an auxiliary aircraft.

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Fri 15, 2019 4:00 am 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 4681
Location: Norfolk, VA
zarco wrote:
I have the 400 Hz power transformer but no clues of who made that
either. As I had mentioned not only is there no ID plate but no hint that
there ever was one such as glue, faded paint or screw holes. I've looked
inside and out but can find no clues there either.

Sure there are date codes on the components but that won't tell
me much except about when it was made.

And this looks like a production unit, not a prototype.

Still hoping someone recognizes it. A friend mentioned it appears to
be made the same way the T-368 is so looking at that now.
Steve


A picture of the guts would go a long way, as would any part numbers or inspection stamps.

Clues from the boards - any hermetic parts? Any conformal coatings? Any part numbers on the boards/sub-chassis?

Maker of the the switches?

A pic of the tuning gearing might be the biggest clue - so many are alike that a Collins radio can be picked out, if only by the choice of fasteners....

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Fri 15, 2019 5:28 am 
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Joined: May Wed 23, 2018 6:28 am
Posts: 483
Brian,

I think Steve sees this as a test. He probably already knows where it came from. I think it only exists because of the CHIRP capability, which is unintelligible on non-CHIRP equipment. Since we haven't heard from him, maybe it is a black radio and he has been detained for questioning.

My contact with Navy equipment was 50 years ago with equipment that was older. What I had with Navy tags were RDZ, RBA, TCS, PP-351U, a scope, a frequency counter., and an R-389, which is the only one of the group I held on to. All were 115V 60 cycles. There was a 220V 60 cycle PS for the TCS and the PP-351U could also take 220V 60 cycles. Everything I had that was 400 cycles was AF.

I'm sure your experience is broader and more recent.


John


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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Fri 15, 2019 5:36 am 
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Location: Norfolk, VA
Superretrodyne wrote:
Brian,

I think Steve sees this as a test. He probably already knows where it came from.


John


Nah, he's just waiting for the dollar store to open in the morning to buy camera batteries..... :lol: :mrgreen: :P

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Fri 15, 2019 2:58 pm 
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Joined: Jan Mon 28, 2013 9:35 pm
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Location: Santa Rosa, CA
Sometimes you guys crack me up! No, this isn't a test or an April
fools prank. The pic I posted was taken years ago. This set is hard to
get to now so additional pics will have to wait till things get moved.
And while pics of the inside might be interesting, doubt they
will help with chasing down a model number.

Several interesting points have been brought up; this could be commercial,
as opposed to military equipment and the info about CHIRP mode.
I'm aware of how this mode is used in radar systems and was wondering
how this applies to HF? Possibly converted to baseband which is in the
HF bands?

Some more details;
Internally this unit uses plug in circuit boards for everything.
Each board is approx 4"x5" and there are two rows. It does not
use a microprocessor. All IC's are TTL and tuning is via an RPG
(rotary pulse generator) so no mechanical VFO. The LED display
has a nifty brass or copper screen for RFI. The meter, although it
looks odd is mounted on a sub panel and there is a piece of glass
in front of it. It appears to be a standard Weston type.

Others I've shown this to think it might be part of an ECM (electronic
countermeasures) system. The large rectangular (approx 1.5 x 3")
connector on the back (including many coax connectors) reinforce this.
At the very least an RF power amp for the transmitter was used.
It appears to be locally controlled *only* with no provisions for remote
control that I can see. This was purchased at a SF Bay area swap.
Moffet air field is closeby where P3 Orion aircraft are (were?) based and
these were outfitted for ECM. At least the ones I saw having lived
very close.

But all of this is speculation verging on wild-arse guesses. Still hoping
to find the model number to eventually find documentation.
That may never happen but worth asking.
Steve

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Fri 15, 2019 6:43 pm 
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Location: Norfolk, VA
zarco wrote:
Moffet air field is closeby where P3 Orion aircraft are (were?) based and
these were outfitted for ECM. At least the ones I saw having lived
very close.


Steve


Were. All Naval Patrol Ops were moved to NAS Whidbey Island or MCAS Kaneohe Bay HI about 25 years ago. EP-3's are all out of Whidbey. I visited Whidbey in 2004, but saw very little of the Patrol side of the flightline.

Moffet is all commercial or NASA Ames stuff now, although there are some Army Reservists and ANG folks there.

Perhaps NASA or Commercial? It might help to peruse Janes "Avionics" for the 70s/80s/90s to see what you can find....

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Fri 15, 2019 10:25 pm 
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Glad you made it through interrogation, Steve. No need to deny it, as I know what the penalty for disclosure is.

CHIRP is just an odd form of FM modulation. For modulation, it is not related to its use in RADAR. The carrier frequency sweeps a range. The range can be anything, but I would assume in the non-spread-spectrum use, it would be one of the standard bandwidths. The modulation is superimposed on the sweeping carrier, requiring a different kind of detector than normal FM which modulates around a fixed frequency. So, you have the predictable sweep frequency modified by the audio in CHIRP. Demodulation has to extract the audio by detecting the variation from the predictable sweep frequency. The RADAR use is much simpler, just picking some number of frequencies within a sweep to process.

My first thoughts were of Orion or State Department. They both have their oddities. I ruled out State because of the 400Hz. The last time I was on an Orion was 8 years ago. It was upgraded quite a bit from my visits to Moffett in the late 1970s. I said earlier that I thought this was a 1970s unit, which makes sense. The NSA's NESTOR was a failure in the late 1970s in the field (Vietnam). There were rapid increases in secure communication from the mid-1970s forward, but DES wasn't formalized until 1977. Filling the void in the mid 1970s were devices like the CVX-396, but although these existed, they weren't in use until 1980. So there was a period in the 1970s during which it was probably reasonable to use odd solutions to prevent casual interception of unclassified communication.

It seems impossible to find any info on CHIRP on the internet. I swear, I did not make it up. It actually existed, once upon a time. Steve's radio may be the only evidence.

Odd coincidences - I am headed to the west coast next week. My daughter is moving from Palo Alto, near Google/Moffett to DC at the end of the month. Then I am headed north to Beaverton and beyond to the Seattle area where my sister has moved from Whidbey to the other end of the bridge.


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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Sat 16, 2019 1:56 am 
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Location: Seattle WA US
Search on <chirpsounder>

HF chirp sounding for ionospheric measurements was one aspect of early Automatic Link Establishment (ALE) schemes. As the objective was highly reliable, highly secure communications, people with such interests didn't publish a lot about their work.


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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Mar Sun 17, 2019 12:58 am 
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I think you should just send the radio to me so you don't have to worry about it anymore. I would of course pay shipping.

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 Post subject: Re: Need help identifying military HF transceiver
PostPosted: Jun Wed 05, 2019 4:58 am 
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Zarco,

Resurrection

This has nagged me for months.

Quote:
So far, we assumed the chirp transmitter's signal is not modulated, apart from the constant increase in frequency. However, a way has been defined to send some digital data along with the chirp. This is done by having the transmitter transmit during a 1 bit on its normal frequency (although still rising at 100 kHz/s), and during a 0 bit 250 Hz higher. So it's just FSK, albeit with a chirping carrier. The datarate is 55 bits per second; every 6 bits form one character, and the entire message is 40 characters long, so the message is repeated every 40*6/55 = 4.36 seconds.

The idea is that this can be used to simply transmit a short message world wide. Instead of having to find and coordinate a frequency with suitable propagation, the message is repeated all over the HF spectrum, under the assumption that somewhere there is a frequency band which propagates to the intended destination. This is of course a rather inefficient use of spectrum and transmit power.


http://websdr.ewi.utwente.nl:8901/chirps/article/

I have run into this guy on other esoteric issues. I should have thought to look on his site. He says it's FSK and it has similarities, but I found several references to SSB. I have seen a few SDR waterfall images that clearly show a CHIRP signal moving left to right in the frequency spectrum. Unfortunately, I didn't capture them.

So, CHIRP is used for radar, propagation study and an alternative to the numbers stations. I suppose the rise of other spread spectrum methods ended its usefulness in military communications in the 1980s.

This is a circa 1985 ionospheric sounder (ionosonde) receiver:

RADIO RECEIVER (R-2081/TRQ-35(V) ) MODEL RCS-4B
Attachment:
R-2081.jpg
R-2081.jpg [ 128.44 KiB | Viewed 1134 times ]


This is a later RCS-5:
Attachment:
RCS5AF.jpg
RCS5AF.jpg [ 102.66 KiB | Viewed 1134 times ]


This some more info on CHIRP sounding:

https://www.qsl.net/zl1bpu/IONO/chirps.htm

My point is that the sounding issue doesn't seem related to your radio, so I still believe it is intended for CHIRP communication.

John


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