Need a Cheif Engineer...

[Thom Rounds]

At some point in the next 10 years I suspect the need for AM directional engineers, and transmitter engineers will be just about completely gone. When the auto manufacturers start putting internet in the cars, broadcasting is dead. There will still be a need for studio engineers, but not for transmitters. I recently got an Iphone, I listen to music, to internet radio and I don't loose the signal unless I am driving between dead zones. Once the holes are filled in with cell towers, and the car makers put the internet in the cars, it is done!

Hmmn... seems we've heard this before:

TV would be the death of radio.

FM radio would be the death of AM radio.

Cable TV would be the death of broadcast TV.

Sattelite TV would be the death of Cable TV.

HD Radio would be the death of AM and FM radio.

Sattelite radio would be the death of terrestrial radio.

And now... the internet will be the death of people needing transmitters for anything.

Of all these "x will be the death of y" scenarios put forth over the years, zero of them actually came true.

TV didn't kill radio, it merely changed the programming style. FM radio didn't kill AM radio, it merely changed the dialscape. Cable TV didn't kill broadcast TV, it merely changed shape of the programming. Sattelite TV didn't kill Cable TV, it merely provided another option. HD Radio is enjoying all the demand of AM Stereo. Sattelite radio hasn't killed terrestrial radio, in fact it's providing some terrestrial stations with feeds they didn't have before.

It will take a lot longer than ten years for any need for broadcast services vanishes from the face of the globe because of the internet, or anything else.

One thing you'll notice about these broadcast radio or TV "killers" is that they have one thing broadcast services do not have: a subscription fee. The same is true of any Internet provider, you have to pay for the service. Internet feeds are no more likely to kill broadcast radio than sattelite radio. All they will do is provide another option.

For those not living in The Big City, wireless internet is nowhere near as reliable as even sattelite radio is. Some areas of the country face serious topographical challenges that makes covering every square inch of land at microwave frequencies impossible. After all these years, there are still large swaths of land in the continental U.S. where you simply can't get cell service, let alone internet-capable cell service. Those areas are still well-served by terrestrial radio.

Until you can call broadcast radio/TV itself obsolete (and have it actually come true this time), there will still be a need for broadcast engineers. No, you're not going to get rich doing it, and chances are you'll have to have more than one station or group as clients in order to keep it lucrative, sometimes even doing it as a second job.

We just refurbished the mortal remains of a Harris FM-25K and converted it to single-phase for one client, so I beg to differ with those saying that there are no real engineers out there anymore, or that nobody is being trained under them. There certainly is a need for engineers, and a young crowd who would really enjoy working as one (no matter what you think they want), but who would want to become one when those they might learn from turn their noses up when someone says they're looking for one?

Am I the only one who sees this attitude as a bit self-defeating?

--Thom Rounds

 

[ChiefEngineer]

Croseley spent how much to build the 500kw WLW transmitter? Tube changes were 30k supposedly. This was in the depression.

TV created changes and so it goes.

I am sad to see the old WIBC 1070 now at less than a 2, 1.2 I think. AM stations as a whole are not worth much because their programming is horrible. FM is tracking the same way.

Remember the 1970's when everyone on AM dumped music (with high ratings in many cases) because this was 'the thing to do".

I can't tell you the last time I heard something incredible on a local station or Sirius or XM or the inernet. The TV clips can only point to Tina Fey doing a comic impression of Sarah Palin as one of the high points of last year. I remember the dancing guy on youtube and the latest Barack the Magic politician.

Yawn. Just waiting to hear or see something exciting in any medium. Media overload equals media complacency.

 

[littlejohn]

The thought of single -phasing a 25K is mind boggling, the first boggle being 'why'. Did you go the whole mile and rebuild it with the original drive amps and splitter/combiner? "Numbers matching" as it were?
I had serial #5 of the 25K manymany moons ago. It was underwhelming in pretty much every way.
I'm not tknocking the exercise as an exercise, it's just there's gotta be something better out there for the service.

 

[Thom Rounds]

The thought of single -phasing a 25K is mind boggling, the first boggle being 'why'. Did you go the whole mile and rebuild it with the original drive amps and splitter/combiner? "Numbers matching" as it were?
I had serial #5 of the 25K manymany moons ago. It was underwhelming in pretty much every way.
I'm not tknocking the exercise as an exercise, it's just there's gotta be something better out there for the service.

The same reason anything happens in radio: money.

The only available power at the new site is single-phase. The engineering insultant they originally hired to plan the project wanted to sell them a brand new Harris Platinum-series HD-ready flash-bang bells-and-whistles transmitter, which goes for around $60,000.

They already had the FM-25K, which was originally slated to replace another of their FMs (a much-abused Gates 10-G) in a three-phase-equipped building. It was a bit cheaper than the new Harris: they got the 25K for $500.

Why only $500, I'm sure you're asking? It hadn't been used as an actual transmitter in years. The previous owner was using only the PA section as a 100 MHz square-wave amplifier for driving a laser. They re-wired it for fixed full bias (-500V) and externally fed the screen supply (with God-only-knows what). They said they were never happy with the output waveform, and I discovered the transmitter was appearently never happy with the input waveform, either: a toroid doughnut around the filament jumpers got very hot from RF and cooked its way through the insulation (it would seem they didn't understand the importance of the cathode inductance, they left the tube socket exactly the way Harris set it for 104.5 MHz, so the filament supply got hot with RF at 100 MHz).

So there was the challenge: cheap, half-dead Harris FM-25K; new site with no three-phase primaries within miles. Fortunately, the CP was for 22kW ERP, and we were able to shoehorn a 7-bay half-wave-spaced Shively into the available tower space, so we only needed about 11-12 kW.

Since the PA Plate and IPA supplies are the only three-phase supplies in the whole transmitter, it was not as tricky as it might sound, just a lot of heavy lifting. It went something like this:

From the PA Plate supply cabinet, we pulled the three-phase transformer, the filter reactor, and one of the rectifier stacks. We then took a 25 KVA pole transformer, pumped out enough oil to get to the tap switch, disconnected the low-voltage center-tap and re-wired it to position "1" of the tap switch to affect a high-voltage center-tap (only to find out the tap switch is not quite at the center of the HV coil), and pumped the oil back in again. This modification allowed us to continue using the high/low power knife switch in the supply cabinet.

After that, we re-installed the original reactor, along with a 5 henry oil-filled Dahl reactor. The oil reactor has a very slow leak, so we put the reactors on the negative side. It ran fine in the positive side of a single-phased McMartin for years with this leak, so we're not too worried about it. Between the two reactors, a total 12uF/10kV, and another 11.5uF/10kV after the second reactor. Pretty much everything after that is stock electrically, though we did have to move a few things around to make room for the pole transformer.

As far as the IPA is concerned, we did manage to get it going on single-phase power by simply cutting the delta-wiring between secondaries 1 and 3, feeding 240V across primaries 1 and 2 (in series), with secondary 3 disconnected. It was a bit under-volted, but it worked. However, two of the IPA modules had one dead transistor each, and it seems like everyone with a 25K has given up on those IPAs, so we just said "screw it" and threw a 500W amp in line after the exciter, which runs very comfortably at 250W. We eventually pulled that transformer, so the IPA/combiner combination is just dead wheight now.

The blower was replaced with a much smaller single-phase unit with the same rotational speed but less horsepower. We'll never need the kind of air the original blower moved anyway: a 4CX20,000 running 12kW will die of boredom long before it dies of stress. The filament seal is the biggest concern in that situation, and there's plenty of air for that.

Beyond that, it was all the usual things you'd do to bring an old disused transmitter back to life and get it tuned up (screen and bias supplies, input stripline, output cavity sizing, boring stuff like that).

With the knife switch in the half-power position, we've been getting 2.2 amps at 3200V, and around 5.5kW on the external wattmeter, so it all works pretty much as we planned. Once the 200A service is lit, we'll throw the switch to the full HV secondary, and set the unit to run 2.5 amps or so at 6300-6400V (with the off-center tap it's hard to tell what the voltage will be), 11kW TPO into 220' of 2.25" air-dielectric heliax will give us 10kW at the antenna, for a total of 22kW ERP, right on the money.

So... it was fun, but to be honest, it doesn't hold a candle to WBCQ's single-phased Gates 50-S on 7415 kHz. That is, by far, the manliest single-phase supply I've ever seen in person.

A big undertaking, yes; but even after you figure in our time and parts, we easily saved this customer close to $55,000 on this job alone. That's something I can take pride in, the customer can be thrilled about, and makes the whole thing worth every ounce of hassle.

--Thom Rounds

 

[littlejohn]

Like I say, as an exercise.........
Sounds like a fun challenge. What kinda numbers you get out of it? Noise and the like..

 

[greg.hahn]

That's a great story Thom! Wow....what fun.