RMCA MOPA transmitter

[W3GMS]

I am trying to get some documentation on this transmitter.  As you can see the panel and front controls are all there, but a lot of the components inside are long gone.  Meter Id's indicate this set was manufactured by the Radio Marine Corporation of America for Marine use.  Small size and simple topology leads one to believe it may have been used for emergency use.  Knobs suggest vintage between 1925 and 1935.  Tube shelf has space for one oscillator and two amplifier tubes.  

The idea behind this project is to get enough information on it to be able to restore it.  

Any information on this would be appreciated!  

Joe, W3GMS

[W3RSW]

Neat Joe. Wonder if it's a lifeboat or small craft transmitter?
Where are the tube socket holes or were the sockets raised on stand-offs originally?
The rF ammeter goes to 5 amps and the compensation circuitry seems to be intact. The far left ant. Control goes to a variometer apparently. Nice compoments.  Even if you find no further info., wouldn't take to much to lash up something.

Appears to be a predecessor to the ET8025 emer xmitter using instant heating 1624 tubes. That one uses two as MO and four as PA.  This one might use one as Osc. And two as PA.

Sittin' outside w/ my iPad on one gorgeous day over here.

[W3GMS]

Hi Rick,

Thanks for your comments on the transmitter. 

The tube sockets on this unit were surface mounted type and not the one where a hole is punched.  If you look carefully, you will see 2 holes to accommodate 6-32 screws for each tube location.  The surface mount style sockets also give us a clue as to the period of the piece.

I found a Maritime Collectors group out on the West Coast and a friend contacted them and they never heard of it.  It seemed their knowledge base was about 10 years later and going forward in time. 

So depending on what can be located will determine if there is any hope of bringing this piece back to life. 

73,
Joe, GMS   

[K4RT]

Joe,

I hope you're able to find what you need. You've probably already seen this web site http://www.imradioha.org/RMCA.htm ... but if not, it might be worth making contact with them in your search for documentation.

Comparing the two photos, the variable capacitor behind the panel that appears to be connected to the knob labeled "ANT. SER. COND." has beige or gold colored plates. Do you know if that is the color of the metal or a coating on the plates?  I have seen that before - in a WW2 Navy receiver - and assumed it had something to do with preventing rust or corrosion, but did not make a close inspection.

73,
Brad

[N8ETQ]

Hey Joe,

     Years ago I had an RMCA ET-8019 TX. It stood
about 3 ft. tall. Pair of 813's. It was missing
the exciter.  No power supply either, the juice
was originally supplied by a Motor-Generator on the
ship. No modulator even though it had a "MCW"
position. I was told that for MCW they just dumped
unfiltered DC to the finals.

     I scrounged up a Heath mobile rig with a 807
final (Don't recall the name) I was planning to use
for an exciter.

     Anyway I don't know where he is now. He's been
gone for a while.  Ship TX's of the day ran on 500KC
and parts of the 2, 4, 6, 8 and 12 MC Marine bands.
I still listen to CAMSLANT on 8764 Up with a R-1051
for the high seas forecast during Hurricane season's.
Been pretty slow the last few years though.

http://www.nws.noaa.gov/om/marine/hfvoice.htm


GL with the thing,

73

/Dan

[W3RSW]

Brad and all, that's the site I found the ET 8025 circuit diagram as well as manuals, etc for several more modern rack mounted, shipboard rigs.  Same variometer output or very similar model with MOPA circuit which led me to believe Joe's is an earlier version but With half the later model's doubled up tubes in each stage.

Looks like a fun project Joe. The ET 8025 should give you lots of hints on how the antenna coupling, etc. was lashed up.

[W3GMS]

Thanks for all the replies! 

Brad, that is the material of the plates so its all natural!

I did check that website you have the link for and this version is to old for them to know anything about it. 

I was thinking about it possible advertised in some early magazine but not sure which ones would have carried it, if any. 

It was mentioned to me that maybe some of the early sterling technical publications may have a picture of it.  They did that from time to time. 

Joe, GMS   

[W7TFO]

Joe,

Keep in mind RMCA was just a division of RCA, so a similar rig may have been produced in parallel.

73DG

[W3GMS]

Joe,

Keep in mind RMCA was just a division of RCA, so a similar rig may have been produced in parallel.

73DG

Thanks Dennis that is an excellent suggestion and may help in finding some documentation for this piece.

73,
Joe, GMS