Military AN/SRT-3
RMCA ET-8010A


600 Meter
CW/MCW TRANSMITTER





The AN/SRT-3 transmitter is an old Radiomarine Corporation of America (RCA) transmitter designed for operation in the Marine Mobile (Shipboard) service. The RCA designation is ET-8010 A, this transmitter consists of a pair of 211s' in the final output stage. The Master Oscillator stage is an 807 and the Buffer-Driver stage also features an  807.  I have endeavoured to change the R.F. section to move it from its' normal frequency range of .35 to .515 Mhz. to coverage of the 1.8 Mhz 160 meter band.

The power supply section consists of 866A rectifiers for the H.V. at 1300 VDC adjustable and a 115 VAC variable transformer for the filament transformer installed in the transmitter, which requires approximately 70 VAC to the unit transformer. A 12 VDC power supply provides for the keying relay in the transmitter. A.C. input power is 115/230V
60 hz. at about 1300 watts.
 
Here are pictures of the unit as purchased on "E-Bay" for $232.00 + 80.00 to ship to Buffalo, New York.





These pictures were distorted on E-Bay to give the impression the unit was larger than it actually is. That didn't matter to
me, I knew what the unit really looked like and I wanted the unit for the express purpose of moving it to 160 Meters and operating it as an AM transmitter.
The power supply (HV) was built in a rack cabinet with casters on its bottom, and a flat plate of plywood on its top,
to replace the louvred top, to allow for the transmitter to be bolted on top of the power supply rack cabinet.

When I got the unit, I really wanted to get it going, so I used the tried and true method of "FORENSIC ENGINEERING",  I got
out my Simpson 260 VOM and buzzed out the lines to determine where everything was
going to and coming from, so I could at least install tubes and put filament voltage on the unit. I used "ORCAD"
to draw schematics of what I thought I had. and fired up the filaments. That was encouraging enough to start on
the power supply for the unit.
After some cleaning and dusting inside the unit, making wiring harnesses to/from the power supply cabinet, The unit
was checked out on the marine frequencies first, and then the transmitter was retuned to the 160 meter band.
I got a copy of the schematic and operating info from "Marc" VE3GIX and made sure all was in order with the transmitter.

Here is page "1" of the schematic.
Here is page "2" of the schematic.

Here are my orcad drawings for comparing, this is what I found out with my Simpson VOM.
Oscillator, buffer/driver, PA, H.V. power supply
I also had to buy a couple of aluminum panels for the unit as the E-Bay seller, would not provide them,(Sigh)!
Here is the unit as it appears now on 160 meters, minus the sides so you can see the "INNARDS" of the transmitter


those 211s' make a real warm glow in the shack, See ya on 160 meter AM.

Possibility of Amateur Operators, getting a portion of the 600 Meter band, has prompted me to rewire to
its original form this transmitter. Follows are the notes and changes as they were put in effect.

For monitoring the oscillator and multiplier/driver stages,  there are banana jacks mounted for plug in meters.
The oscillator requires a 0 - 15 MA meter, and the multiplier requires a 0 - 50 MA meter. I wanted to put
them on a single panel and mount them in the power/control cabinet that the unit sits on. I got a 5.25 inch
panel to mount the meters on.


             Punched it out, mounted the meters and we are all set!





The 211/VT-4C
PA
Compartment





Note the five (5) coils in the upper left for the 5 "Channels".





The Oscillator is at the bottom, and the driver is just above.
only two of the tuning coils are visible in this shot.


NOTE: The 600 Meter Research Group license was approved, and I scrambled to undo the changes to the
SRT-3 transmitter, and put it back onto the 600 meter band.

With the New interest on the Glow-Bugs Listserver, I decided to make the SRT-3 back into a "LOWFER"
transmitter. If we don't get use of the "Old Marine Radio Band", I still have the easily installed changes to put
this transmitter back on 160. The front panel control for changing the frequency is marked with "Brass" channel
plates that specify where the transmitter is operating. The oscillator section can use crystals or operate as a "MOPA"
for use in "LOWFER" applications I chose to run in mopa mode, as the tuning gives great latitude in the frequency range and is also quite stable for AM/CW/MCW operation. My beacon keyline is controlled by a AEA PK-232 driving the
keying relay circuit to the transmitter. The antenna connection wants to see a 4 ohm antenna at 1300-1500 uuF  (750uuF recommended)
antenna as a load/output radiator. I have provided a 100 foot flat-top with 3 lines evenly spaced across 3 two foot
lengths of 2 inch dia PVC pipe, with three down leads joined 10 feet below the flat-top going to a single wire which
is the lead-in wire for the antenna connection to the transmitter, standby for reports once the license is OK again.


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