tech stuff – Page 65 – Engineering Radio

Nautel V-40 FM transmitter

Yesterday, I threw out a transmitter. I know there is probably some radio station out there that may have been able to use a 5 KW FM transmitter but believe me, not that one. There are limits to how much you can help out a fellow broadcaster. Donating an FM transmitter that never really worked right in the first place is counterproductive.

Anyway, to demonstrate that I am not a total heel, here is my favorite brand of transmitter, Nautel:

Nautel V-40 transmitter (4 V-10 transmitters combined)

I like Nautel because they are rugged, reliable, and good-looking. Okay, good-looking is low on the list of transmitter attributes, however, you have to admit, it is good looking. It is also good sounding. The night we switched over from the long-in-the-tooth BE FM30A to the Nautel V-40 I noticed a marked improvement in the station’s sound. It was like somebody switched off the background noise generator.

As the caption states, this is 4 V-10 transmitters combined with an ERI magic T combiner. It is set up so that if any one transmitter fails or reduces power, the magic T combiner automatically adjusts for minimum rejected power, then the SC-1 controller turns up the other three transmitters to maintain the station’s Transmitter Power Output (TPO).

In this case the TPO is 28 KW, which is getting into the semi serious range for an FM station. Nautel has updated their transmitter line, which now consists of the NV series transmitter. The differences mainly have to do with the IPA module/PA module interchangeability (not interchangeable in the V series, fully interchangeable in the NV series) and the “Advanced User Interface.” I don’t know, fancy touch screens are optional on FM transmitters as far as I am concerned. It’s the underlying RF generating sections that I am most concerned about.

Another view. Just for the useless trivia that is in it, the “V” in these transmitter names stands for “Virtuoso.”

Gates FM5G transmitter

Takes its rightful place in the world today, the scrap heap:

As EDWARD I of ENGLAND once said, “A man does good business to rid himself of a turd.”

Of course, he was speaking about Scotsman John Balliol and not some old cranky FM transmitter, but I understand that feeling. The Gates and later Harris transmitters always seemed to be somewhat less than top-notch. The 5G was no exception to this rule. The final step for tuning the transmitter was to turn off the lights in the room and look down through the screen on top to make sure there were no little arcs in the PA tuning section. It also had a way of self-oscillating, which could make for some exciting tuning.

Gates FM-5G transmitter prior to disassembly

Goodbye, I will not miss you.

In one of my past jobs, I worked in a RCA town. I worked there long after the broadcast arm of that company went out of business, however, all of the broadcast transmitters, AM, FM, TV were made by RCA. I had an RCA FM-20ES1 which was 22 years old, built like a tank and just kept going along. I think that transmitter was finally destroyed in a fire, caused by it’s replacement transmitter.

Old Collins, Contenental, RCA and even Broadcast Electronics transmitters had some heft to them. Of course, not every RCA transmitter was well thought out, the amplifuze series of AM transmitters were a maintenance nightmare.

Lightning strikes

For about 4 years, I lived in a house next to a four hundred-foot radio tower. Although I never actually saw lightning strike the tower, I heard it several times. Like everything else, after a while, you get used to it.

This is a video of lightning hitting the WSIX STL tower in Nashville, TN. The camera work is a little unsteady, the strike occurs around the 1:36 mark:

Yep, that is what it is like.

Module swap guys

Gone is the day when the radio station engineer had to troubleshoot down to the component level, often crawling in and out of transmitters to get at the suspected part. I for one, spent many a long night at a transmitter site chasing some weird combination of symptoms down to the $0.34 1N914 diode in the directional coupler (see previous post about the MW-50).

It is a skill set now mostly confined to manufacturers’ repair departments, for which they charge a pretty penny. Nowadays, the technician simply slides out one module or circuit card and slides in another. If that doesn’t fix it, panic ensues. I know of several class C FM radio stations that are now relying on the computer guy to fix transmitters, because, you know, it’s cheaper.

To be fair, most engineers are contractors and many of those simply do not have the time to troubleshoot to the component level. So, they ship everything back to the factory and then pass the cost on to their client.

Then of course, most circuit boards these days are surface mount systems, which are hard to work on if you don’t have the right tools. Normally an expensive temperature-controlled soldering station is required, as well as a magnifying glass.

All of these things combine to make circuit board work something to be outsourced. Unfortunately, a night spent troubleshooting was often a great learning experience. I have done some of my best work when my back was up against a wall and I was out of options.

I make the attempt to fix things locally unless the transmitter or other item is under warranty or not having a spare/attempting to troubleshoot will take the station off the air. I think it is important to keep abreast of technology and keep my troubleshooting skills up to par. Besides, I find it gratifying that at least I can still fix things.