AM Transmitters – Page 6 – Engineering Radio

Australian Made Broadcast Equipment

Somebody working to preserve a record of past work:

Some of these have familiar looking cabinets and tube arrangements. They all look like classics to me and it is good that they are being saved. I noticed at the end of the video there is a Harris MW10A. As for the RCA Ampliphase transmitters; I maintained a BTA5J in Harrisburg PA on 580 KHz. It was reliable enough, but I could never keep it sounding good for more than a couple of days.

In any case, a worthwhile effort. More information at: AWA Transmitters.

Harris exits the broadcast industry

When they sold their Broadcast Equipment supply division to SCMS a few years ago, the handwriting was on the wall. Even so, it is a little surprising that they would exit broadcasting altogether.

The decision to divest in no way reflects the quality of the work Broadcast Communications performed in support of our customers and our company. Harris simply determined that Broadcast Communications could provide higher value and operate more effectively under a different ownership model.

They are spinning the broadcast division off to a new owner rather than completely shutting down the operation. In an e-mail received from Harris Morris, President of, Broadcast Communications Division, clients and customers will still receive support for existing products:

In the interim, Broadcast Communications will continue to be a part of Harris Corporation and operate business as usual. Our valued relationships, both longstanding and new, remain our top priority. The global Broadcast Communications team will continue to work diligently to ensure our commitment to our customers and partners remains steadfast, our execution to fulfill commitments is flawless, and our progress against strategic objectives remains focused.

Well, there you have it. This affects such things as Harris transmitters (AM, FM, TV, HF) and support, Harris consoles and studio furniture (previously Pacific Recorders and Engineering or Pacific Research and Engineering, AKA PR&E), and Intraplex STL systems, among others.

What does all this say about the future of terrestrial broadcasting?

We live in interesting times.

Back when transmitters used to look like something

Other than a humming box, that is. RCA broadcast, prior to the period in the seventies just before they went out of business, made some good-looking transmitters:

The Art Deco design was favored for a number of years, especially with the AM units:

Some of these RCA transmitters are still in service as backups.

GE made the BT-25A, which was a 50 KW transmitter in Syracuse, NY for a few years. These units were very similar to the RCA BTA-50 transmitters.

GE BT-25-A looking from the control cabinet

Gates of Parker Gates, pre-Harris, also made some classic transmitters:

Gates BC1J transmitter — Gates BC1J AM transmitter

I remember the BC5P had a similar look, with more transmitter cabinets.

Fritz Bauer made a very solid AM transmitter. Good looking, too. We need more pictures of old transmitters and other hardware.

The Gates BC250GY transmitter

This transmitter is in service at WSBS, Great Barrington, MA as a standby. It was new in January 1975.

Gates BC250GY transmitter, WSBS Great Barrington, MA

This was running into the dummy load for testing, which we try to do periodically.

Gates BC250GY AM transmitter audio section

The audio section is a pair of ~~8008’s~~ 810s running in parallel. This goes through a modulation transformer to the RF section.

The RF section consists of another pair of ~~8008’s~~ 810’s running parallel. The plate voltage for these tubes is 1,250 VDC which is fairly tame, all things considered. The transmitter is dirt simple 250-watt carrier power, 125% positive peak capable. It is not the most efficient unit under the sun but it can still be repaired with off-the-shelf parts.

This is a somewhat faded schematic. The schematic shows a single 833A as the final, however, this particular transmitter has a pair of 810’s for the final, as shown in the above picture. Ham radio operators love these things as they are easy to convert to 160 or 80 meters for AM phone use. The bigger brother to this unit is the Gates BC1G, which is also a pretty simple unit using 833A tubes in parallel with 3,500 VDC plate voltage.