KPFK Transmitter Tour

A brief look at the KPFK transmitter facility at Mt. Wilson, 5700 feet above Los Angeles. We just finished adding a new antenna system, so the site is a mess at the moment.

The main transmitter is an Armstrong 60000FMT, and the backup transmitter is an older CCA 20000GS. KPFK operates with 110,000 watts ERP (effective radiated power). The new antenna is a Shively 6814-5R.9SS, a high power, reduced wave-spaced design, which allows more power to the audience and less energy on the ground below the tower. The standby antenna is a Jampro 4 bay high power model, and at the very top of the tower is a single bay Shively 6814 backup. The big reddish covers are for ice protection, which is very important up at Mt. Wilson. The winter of 2008 brought lots of ice and snow, and lots of damage to adjacent transmitter sites up there. KPFK did fine, except for one of the STL (Studio-transmitter link) dishes that has a bent feed horn (scheduled for replacement this spring).

The guy you can see evading the camera is Bob Conger, the chief engineer at KPFK. He keeps the whole thing running smoothly.

Category:

Science & Technology

Tags:

• electronics
• mechanics
• radio
• transmitter
• KPFK
• Los
• Angeles

[letseeitplease]

that was a real nice tour of the transmitter site and seeing all those towers, thats kind of like being there for me, i was wondering how you radio and tv people that work on the equipment, how you walk around in the transmitter area without getting radiotion poison or getting burned from rf energy,, i saw the sign that said do not enter high rf energy,,, please notice i am just a viewer, so thats why i was asking, thanks for any response, and thanks for posting your video

[donmussell12]

The RFR levels at this site do not exceed Federal standards, so it is considered safe as a working environment. Across the street is a private residence where a CalTrans worker and his family lives. There is no such thing as radiation poisoning when around radio and TV transmitters. It is electromagnetic energy, not gamma radiation that is produced by these stations. Apples and oranges... 40 years of studies have not found any long-term harmful effects from radio-frequency energy.

[drradio2003]

I have a 10kw armstrong runing in elko nv. I hate it, and it's not even from the usa. its from itly. get a nother CCA and combine it. Vand J electronics can build you one, the original engineers from CCA when bernie wise used to own it. now he has energy onix in valitia ny. good god buy american! harris or broadcast electronice, continental, even a nautel. good video tho!

[donmussell12]

As usual, put two engineers in a room and get 10 different opinions. This setup is running good, on the air since July of 2002. I can live with this. I don't want to deal with Bernie ever again.

[donmussell12]

There are three parts to the air system. We have a big filtered blower that sends filtered air into the building at 8,000 CFM. The exhaust hood has a blower that pulls air from the building at 6,000 CFM. And an internal air conditioner that cools the building in summer. Because the site is nearly 6,000 feet above sea level, it mostly stays cool, and only gets warm outside about 40 to 60 days a year. The rest of the time, fresh (filtered) air keeps things nice inside.

[donmussell12]

Because of the location of Mt. Wilson, 5,700 feet above Los Angeles, a high gain antenna is not effective at reaching the service area, which is well below the mountain. A low gain, wide aperture antenna is required to send the signal down enough to reach the audience. Hence, the four bay antenna and high transmitter power.

[Arabhacks]

Yes, the modern stuff just sits there.

I remember seeing old AM transmitters with mercury rectifiers that would take the 3 phase and modulate to the sound of music.

But this was another era altogether.

No more water cooling ponds, etc.

[douro20]

"spare Cathermine under bench"- what's that about?

[BudWiser999]

Armstrong would turn over in his grave if he knew his name was on that piece of "junque".

Kind of like Chrysler going to "Fix it Again Tony"!

[RadioHamGuy]

Thanks for posting, fun to see. I remember visiting Mt. Wilson in the early 1980's with a video camera of the time, and as soon as I got near the site, there was so much RF floating around that my video camera would not work at all, the picture was wiped out.

[nnndIT]

I'm surprised the CIA hasn't blown that place up yet. They must be busy elsewhere.

[NoPlaceForLoafers]

Oh, I get it.

Those gigantic copper drainpipes are actually the conductors for the antenna feed...

Jesus.

[nakayle]

Appreciate the tour but these new solid-state xmtrs just don't excite me like big glowing bottles in the old tube jobs. During the 1970s I maintained a RCA BTA-50H Ampliphase. 4CX5000s drove two 6696 triodes running 15.3-KV at 4.4-amps. Our back-up use mercury rectifiers which were fun to watch- they had a blue glow that pulsated with the modulation. Visitors always thought that was neat. Today's mosfet xmtrs may be efficient and low-maintenance but not very much to look at.

[uploadJ]

@donmussell12

Thanks for the info on air handling; I was wondering how that was being done at +5000 feet MSL on Mt Wilson. And thanks for the video tour; no time in this lifetime to make a tour like this in person!

[Meowbay]

@drradio2003 Bernie Wise is an idiot and suffers from delusions of grandeur.

[handsupbud]

I seen a broken wire so that might be your problem.