September 2010
M T W T F S S
« Aug   Oct »
 12345
6789101112
13141516171819
20212223242526
27282930  

Archives

Categories

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 that caused the output power to drop to 10 percent.  The power control is via SCR‘s 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 turns off.  Again, no theatrics;  no big blue flashes, no loud arcs, etc.  Simply turns off the high voltage and lights a LED on the overload board to tell the operator what happened.

Over the las 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 exciter 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 SCR’s exploded while running on generator.  Figured out this was caused by harmonics from the generator exciter.  Replaced the exciter with a different version, no SCR problems 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.

Be Sociable, Share!

2 comments to Continental 816R2 FM transmitter

  • J. Aegerter

    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.

  • Kent Teffeteller

    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.

Axiom


A pessimist sees the glass as half empty. An optimist sees the glass as half full. The engineer sees the glass as twice the size it needs to be.

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
~1st amendment to the United States Constitution

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.
~Benjamin Franklin

The individual has always had to struggle to keep from being overwhelmed by the tribe. To be your own man is hard business. If you try it, you will be lonely often, and sometimes frightened. But no price is too high to pay for the privilege of owning yourself.
~Rudyard Kipling

Everyone has the right to freedom of opinion and expression; this right includes the freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers
~Universal Declaration Of Human Rights, Article 19

...radio was discovered, and not invented, and that these frequencies and principles were always in existence long before man was aware of them. Therefore, no one owns them. They are there as free as sunlight, which is a higher frequency form of the same energy.
~Alan Weiner

Free counters!