Continental 816R2 FM transmitter

This is perhaps my favorite model FM transmitter, the Continental 816R2:

Continental 812R2A FM transmitter
Continental 812R2A transmitter, on the air

I have known this particular transmitter for almost twenty years.  It was installed new at WFLY 92.3 MHz in August of 1986.  I was reflecting on that today, as I replaced the bad 4CX250B driver tube which caused the output power to drop to 10 percent.  The power control is via SCRs on the HV power supply, not the more common PA screen voltage adjustment.  That means the transmitter comes on with zero PA voltage and ramps up to full power.  It makes the whole thing “smooth” like driving a Mercedes.

I have experienced a few overloads, which usually are accompanied by the room lights dimming slightly and the plate voltage turning off.  Again, no theatrics;  no big blue flashes, no loud arcs, etc.  Simply turns off the high voltage and light a LED on the overload board to tell the operator what happened.

Over the last 20 or so years, I think I have had three out-of-the-ordinary problems with this transmitter:

  1. The power supply pass transistor in the 802 exciters failed.  This is a TO-3 case mounted on a heat sink, something like a 2N2225 I think.  It runs hot.  Anyway, the exciter had no 20-volt supplies, which was pretty easy to diagnose.
  2. The SWR foldback did not work during an ice storm.  This transmitter feeds an ERI antenna without heaters or radomes.  About once every 2-3 years there is an ice buildup, which will cause the transmitter to fold back.  In this case, the transmitter overloaded and went off the air instead.  Traced back to a bad/dirty connector on the directional coupler.
  3. One of the SCRs exploded while running on the generator.  Figured out this was caused by harmonics from the generator exciter.  Replaced the exciter with a different version, no SCR problems were encountered after this fix.

I like the Continental tube-type transmitters, they are solid units that perform well and have years of reliable service if properly maintained.

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2 thoughts on “Continental 816R2 FM transmitter”

  1. Much of that transmitter was originally Collins design, and they knew what they were doing in Cedar Rapids. When Rockwell took it to Texas and later Continental, there really wasn’t much done except for the re-design to eliminate the troublesome pair of 4CX250B IPA tubes. If those tubes weren’t used and a single 4CX1000A was used instead, I doubt the solid state conversion would have ever taken place.

  2. Seconded, this Continental 816R2 was originally an older Collins design. Well built, reliable as a rock most of the time. The only real redesign was eliminating the pair of 4CX250B IPA tubes with a solid state IPA. If the 4CX1000A had been used this would have been a simple one tube final with SS exciter design and it would have stayed pretty much the same. The 2N2265 power supply bypass transistor I have replaced a few of with the one in my care. Have had to replace 2 SCRs along the way and upgrade the exciter once and she still runs dependably as a main. And will be for quite some time. Love this classic transmitter. Have the older Collins variant as a standby too, And it is dependable as the Continental is after the tube IPA stages got upgraded and the exciter by the way.

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