US Navy Discriminator Sub-Unit

[0311]

My buddy had this thing in his shop. The unit seems to be in perfect condition. The date stamp on the box is November 28, 1951. I think it is some outdated comm gear, how common are these now-a-days?

 

[Rob Boudrie]

You might want to contact the manufacturer and ask if they have a manual - http://www.hoffmanvideo.com

 

[tele_mark]

Probably used for radio teletype (RTTY), by the description.

 

[appraiser]

good luck finding tubes for that thing.

I miss working on tube radio and TV, the warm glow from a 12BE6..

 

[n1heu]

Part of a kit to change the I/F on a Navy radio receiver. Tubes are still easy to find. Currently the Russians make the best tubes. Chinese second best in my experience.

 

[tele_mark]

Part of a kit to change the I/F on a Navy radio receiver. Tubes are still easy to find. Currently the Russians make the best tubes. Chinese second best in my experience.

Ahhhh, frequency shift as in "transvert", not "FSK".

 

[n1heu]

Most probably is part of a teletype upgrade like tele-mark says.

 

[tele_mark]

Those are some big ass cans, probably potted caps and inductors. This is probably pretty close to the circuit:

 

[tele_mark]

Well, slap my haddock! God, I'm good.

http://www.google.com/search?source=ig&hl=en&rlz=&=&q=cv-89a%2Fura-8a&aq=f&oq=&aqi=

 

[drgrant]

Did Captain Walt give you that?

-Mike

 

[stencil]

The AN/URA-8A, IIRC, accepted single-channel tone-shift (FSK) audio from a (usually SRR-2* or R-390) receiver and provided 30-mA loopcurrent for a single TTY loop. Multiple URA-8's would be stacked and individually tuned to pull subchannels out of a mux package. The pictured subassembly - the discriminator, or tone-shift sensor - was the front end. Nostalgia-inducing, but not otherwise a big market draw.
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[tele_mark]

Here's what it was part of:

http://www.prc68.com/I/CV89A.shtml

Edit: Doing some digging, they were apparently popular with hams in the late 50's, early 60's for RTTY.

 

[tele_mark]

Here's part of the schematic. The SU101 is at the top of the page. Classic FM demodulator, modified to react to mark/space frequencies. Looks like it's set up to act like an op amp comparator on the output?

 

[tele_mark]

The complete unit:

U.S. Navy - CV-89A

The CV-89A was part of the URA-8 diversity RTTY system that was built for the Navy by Hoffman Radio Company. Two CV-89A units were used with a combiner unit to achieve space diversity and reduce fading signals to improve RTTY copy accuracy. Using 15 tubes, the CV-89A is modular in construction. Five modules make up the unit - four are mounted in the chassis and one is mounted in the back of the case. Being an audio discriminator device, the operator has to tune the RTTY signal so the mark and space frequencies straddle the center frequency of the filter selected. Narrow shift center frequency is 1000hz and wide shift is 2000hz. The CV-89A features a built-in oscilloscope display to aid in tuning and determining FSK shift. The oscilloscope display will shift vertical positions with mark and space frequencies and by adjusting the shift knob so the display spreads between the three graduations on the display scale, frequency shift can be measured. The CV-89A requires a separate loop supply in series with the printer magnets. The magnets and loop supply can be connected to the rear A/N MIL connector (14S-9P) or if the TTY/loop is set-up with a single .25" phone plug, it can be inserted into the jack on the front panel behind the small door in the lower right panel. An excellent, easy to use military TU. Built in 1953, this CV-89A is fully functional and provides great copy with any receiver that has a 600 audio line out.

Now hams do this with a computer sound card and a little bit of software. Kind of sad, really.

RYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRY

 

[0311]

My comm knowledge is limited to SINCGARS. Here is the front view.

 

[Gonzo]

Sweet. I love that old stuff. I really feel cheated by getting into electronics in the digital age. The few times I've worked on analog stuff I have a ton of fun, and things are much easier to understand, and you gain a much clearer picture of what's actually going on.

 

[tele_mark]

Sweet. I love that old stuff. I really feel cheated by getting into electronics in the digital age. The few times I've worked on analog stuff I have a ton of fun, and things are much easier to understand, and you gain a much clearer picture of what's actually going on.

Not to mention, there's just more of a sense of accomplishment from working on a piece of electronics that can kill you in a millisecond if you drop your guard and make a mistake. I started out in tube technology as a young teen, and somehow survived, despite taking up to 800V B+ across the chest a few times.

 

[Gonzo]

Not to mention, there's just more of a sense of accomplishment from working on a piece of electronics that can kill you in a millisecond if you drop your guard and make a mistake. I started out in tube technology as a young teen, and somehow survived, despite taking up to 800V B+ across the chest a few times.

Yeah, that too. Touch a circuit card the wrong way and it's fried. Touch any of the old stuff the wrong way and you know it. I actually have a sensitivity to strong electromagnetic fields, which is freeking weird, and makes MRI's fun, but there's been a few times when I've powered up a an old radar T/R and my arm starts twitching. That's when I go all zen with my meter leads.

 

[Squished]

Ooooo tubes....I love tube gear. My tube amp sounds amazing, I wouldn't trade it for equal solid state gear......ever.

Fire it up and watch those tubes glow!

 

[oneswithfunes]

The AN/URA-8A, IIRC, accepted single-channel tone-shift (FSK) audio from a (usually SRR-2* or R-390) receiver and provided 30-mA loopcurrent for a single TTY loop. Multiple URA-8's would be stacked and individually tuned to pull subchannels out of a mux package. The pictured subassembly - the discriminator, or tone-shift sensor - was the front end. Nostalgia-inducing, but not otherwise a big market draw.
.
.

I have a R390 I should pull out of setup again. I love it but don't have space for it.

Sweet. I love that old stuff. I really feel cheated by getting into electronics in the digital age. The few times I've worked on analog stuff I have a ton of fun, and things are much easier to understand, and you gain a much clearer picture of what's actually going on.

You can build stuff on your own. I am going to go get a tube in a minute so I can take a picture and post it for you. It is going to be my next radio project.

Yeah, Touch any of the old stuff the wrong way and you know it.

Touch some of that stuff and that is the last time you touch anything.

 

[oneswithfunes]

Here is my next radio project. Amp for 20m,40m and 160 if I can get it to work. I am think 4kv on plate should do legal limit easy. I have every thing I need except vacuum relays and a new bird slug It is a tetrode but I will do gg. Any guess as to what it is?