Glimpses of Meridian, Mississippi

Flame Fest on the AM Dial!!!

A long time ago (summer 2004) - in a field far away (just south of I20)...
An AM Transmitter decides it's been "lonely" long enough...

This story - tough told "first person" by an inanimate object - so obviously "tongue in cheek" -- is, however - a true story. The events happened (pretty much) as told... This was originally part of another radio oriented page - but with the above story about things "high voltage" - it's thought a story about high voltage "run amok" might be fun... And besides -- where else but Meridian - would one find an anceint "beast" the likes of an MW5 still on the air???!!!

Nobody loves me.
Nobody pays any attention to me. It gets lonely out here in this isolated field - save for the occasional kids parking -
or hunters chasing a deer through here --

NOBODY comes to visit.

No-one, that is - unless I throw a fit.

WM5 transmitter filter flash-over
And boy - did I throw a dandy this past Friday afternoon. I planned it pretty well -
I waited until after 4PM - then started throwing flames.

WM5 transmitter filter flash-over
WM5 transmitter filter flash-over
WM5 transmitter filter flash-over
WM5 transmitter filter flash-over
(L3 70Khz PDM filter coil. This has (depending on modulation level) between 10KV and 15KV at 70Khz on it - up to an amp (audio) through it - this is in the "modulation chain" - in the cathode circuit of the PA (power amplifier))

(Collateral damage to this capacitor)

WM5 transmitter filter flash-over
(Debris scattered over the lower modulator deck. Notice the shorting stick - this is one of two permanently mounted / wired shorting sticks -- often called "Jesus sticks" -- 'cause forgetting to use them can get you to meet Jesus real quick in one of these.)

WM5 transmitter filter flash-over
(Debris even all the way over into the PA side of the chest.)

WM5 transmitter filter flash-over
(Crud even down into the high voltage supply - those green (and one black) things are the 12 phase 15KV 1.1Amp high voltage supply - the huge (1000 pounds) main transformer is behind them. The solenoid above left is one of two safety shorting "relays" to protect people working on the transmitter.)

Sure enough - within a few minutes - the owner and the engineer showed up - checked some stuff - and shut off the power. Not what I had in mind. I wanted to visit - and they turned me off completely. NOT FAIR!!!!

I thought by waiting so late on Friday - they'd fuss with me over the weekend...

I slept until around 2:30PM the next day (Saturday, June 19) when suddenly I woke up. All the nasty dirt, crud and muck had been cleaned out of me - the debris from my flame-fest was all gone - the part I'd taken my ire out on had been replaced with a brand-new one. How on earth did they get that part so fast?

(Thanks to Harris Broadcasting -- including Jim Swift, Vicky and all those nice people - and of course FedEx - when it absolutely positively had to be here - it was!)

(Lower modulator deck from the front of the transmitter.
The big gray "can" is an 8UF 20,000 filter capacitor for the 15KV DC plate supply- with the replacement filter coil mounted between it and the plate of the modulator tube. There are three such "filter coils" that form the pdm modulator filter for the cathode of the PA tube.)

(Closeup of the new filter from Harris Broadcasting)

(Upper modulator deck cleaned up. The coil on the right is the third (final) filter coil - that connects directly to the modulator's plate. The modulator is "hard switched" at 70khz - the duty cycle (in response to the audio) determining how "hard" the modulator conducts. The "harder" it conducts - the more power through the PA - the more output from the transmitter.)

(Upper Power Amp Deck cleaned up.
The PA's cathode is "loaded" by the modulator (through those filter coils)
while the plate is fed directly by the 15KV DC power supply through a matching network.)

(Lower PA / Grid tuning assembly cleaned up. Since the cathode of the PA varies from
(approx.) 10-15KV (putting 0 - 5KV across the PA)
the grid circuit has to "float" with the cathode.
Needless to say - any contamination in any of these areas that could arc over -
would - making for another disaster)

(Lower modulator deck / arc suppression / blower supply deck cleaned up)

At least the engineer and a technician were fusing over me - cleaning, replacing things, checking readings - and FINALLY - POWER - throttled back for sure - but back on the air. For the next hour - the engineer fussed over me - peaked grid drive - dipped my plate - set the HV to 5000V - then loading to 5000W - finally - full power!

He stayed a while then went away. But then about 4PM he came again - checked and fussed. Tweaked some more. Gee - it was so great to have some one care. I guess I'll settle in for a few weeks - I heard the engineer comment my PA was getting long in the tooth - drive was falling off a bit- so he'll be back in not too long to take care of that. He better be - or I'll find something else to throw a flame fest at...

Yeah - I got their attention - they're not going to ignore me - at least for a while - I've got 'em worried good!!

Harris Transmitter model MW5 modded to "B"; 5KW 1390 WMER AM Meridian, MS 39301.

Broadcast Services Division; Common Cents Computers
Randy Guttery, Chief Engineer - FCC General Radio Telephone License w/ RADAR endorsement.
Sherry Guttery, Technician.

All images copyright © 2004 Randy & Sherry Guttery. Page Copyright © 2011 Common Cents Computers

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