 | TALES
OF TWO TRANSMITTERS RESCUES OF CLASSIC BROADCAST RIGS 2 — Harris/Gates BC1H1 |
 1. BC1H | I saw an ad for this on the AM Forum. Bill Kleronomos, KD0HG, in Denver, knew of a station that was soon to be retiring their Gates BC1H1 backup. It was located in an access-unfriendly building. KVCU 1190 had the rig removed from the site using professional riggers from Majestic Rigging and Transportation. It was waiting in their warehouse NE of Denver, when I set out on July 4, 2007. This second broadcast rig was a bit easier to haul. For one thing, I now have a trailer and newer truck. I made good time and spent Independence night at a motel nearby. I watched fireworks from my window, but was too excited to care. I watched television until I could fall asleep. It was like the night before a good hamfest. |  2. In warehouse  3. Rear view |
 4.
Magnetics safely packed | Early the next morning, I drove to the warehouse where I began removing the iron from the base, this time in three pieces, a HV transformer, modulation transformer, and modulation reactor. Harris Corporation in Quincy had value-engineered the venerable BC1 series to practically nothing. It was relatively lightweight, and only slightly larger than the Power Rock 1kW transmitter. But it still had the bare essential components. |  5. After removing iron components |
 6. Rescue was simplified when the Majestic guys loaded the transmitter this way | The BC1H1 was the last of the Gates line to use four 833 triodes with a plate modulation transformer and class B audio. It was replaced by the solid state MW1 in the mid-1970s. It has a pair of 807s for RF drivers, with everything else done using silicon devices. Other than having a built-in dummy load, it was similar in design to the very popular BC1G. A fixed protective grid bias voltage was supplied to the final tubes in the "H". I am guessing that Harris didn’t sell as many "H" models, although the profit margin should have been higher for them. BC1T and BC1G can also be found in the corners and backrooms of numerous 1 kW stations, and are somewhat heavier, with more substantial components in some sections. The earlier the vintage, the bigger and heavier they are. |
 7.
KD0HG holding a spare 833A | The transmitter, minus transformers, tubes and crystals, was wrapped in commercial shrinkwrap, and then covered with a tarpaulin while placed on a blanket in the trailer. It's just taking a long-deserved nap for the ride to a new home. |  8.
K5PRO with his sleeping transmitter |
 9. La Veta Pass, CO - 9413' elevation | Another trip over La Veta Pass, this time about 5PM. It was no strain with the Tacoma, with a lot more umph than the old S10 in the earlier transmitter rescue. Finally, I reached home that evening, to find that friends had planned to use my trailer the next morning to haul rafts to a nearby river. The river runners were waiting for me to unload, so that simplified unloading. I immediately had the bodies needed to offload the BC1H1 onto a pallet in my garage/workshop. The photo shows it before being unwrapped and cleaned, adjacent to the working 314R1. |
 10. BC1H1 adjacent to 314R1 | The transmitter appears intact, only needing some cleaning and a new viewing window in front of the 833s. A mica capacitor had exploded sometime in the past, and sprayed molten solder onto the polycarbonate window, melting holes in it. It’s parked on 1190 KHz right now, and I am just finishing a dolly for it, similar to what I made for the 314R1 four years ago. In the future I hope to report it working, and accomplish frequency changes to both rigs. Information on conversion of this transmitter (and others) can be found in the following issues of Electric Radio magazine: #197 (Oct., 2005), #198 (Nov., 2005) and #206 (July, 2006). Information on ordering back issues is at the ER website. |
For further information on the BC1H, here are some links (all in Adobe pdf format). A manual for the BC1H (with 807 audio driver tubes) can be gotten from the Harris Broadcast Communications support webpages.
BC1H1 main schematic
BC1H1 audio driver schematic
BC1H1 control schematic
Complete BC1H brochure [2.7 MB file]
BC1H overall schematic
Frequency change and audio driver testing note from Harris [~1 MB file]
Product support discontinuance notice
I have rescued, relocated and plan to reuse these two transmitters. They use different technology to generate AM, but both appear to have been good performers. They will be on-air again, as time permits - all they require is floor space right now. They are just a sampling of what can be found, from manufacturers such as Harris/Gates, Collins, RCA, Continental, GE, Raytheon, CCA, Bauer, Wilkinson, McMartin, Western Electric, and others. Have fun, and always remain cautious of the high voltages insid. Cheating a door interlock while energizing HV can be deadly - so don't be tempted to do it!
73,
K5PRO