Dear Andy,

Me to. Broadcaster, I mean. Am 64. Working on my last station, and first TV.

I'm writing to you asking how well will a pair of 4-400's in parallel do in at 76-82 MHz? I'm thinking 500 watts modulated with 8vsb, atsc. Need 1.20 kW. Four 4-400 in parallel? .....

Why Am I Building Such A Thing? I need to replace the amps that came with our transmitter.

I paid slightly less than the price of a space shuttle for our DTV transmitter. Modulator, encoders, combiner and mask filter work great.

The four power amps, 300 watts each, use three MRF-151G's each. Each MRF-151G runs at 40 volts 5.0 amps.

SWR's 1:1.04.

Transistors don't wear out?

These do. At 40 volts & 5.0 amps, they don't short, they don't open, but twelve new MRF-151G's make power for about eight months. Drive them harder ? They make power .....for about an hour till they blow up.

Cooling ? If this type-accepted, type approved transmitter wasn't bolted to the floor, it would hover!

I know solid state xmtrs
are used by nearly all stations. I don't think you can buy one that's other than all solid state. Had no trouble with the Harris (Gates Air) 5kw solid state AM, but the MW5 was also trouble free. (Have an MW-1 parked in my barn if
someone needs one).

So, your opinion please. Senile? or can I solve this cronic problem with four 4-400's?

Oh! Almost forgot! I found a way to get vastly improved tube life from 4-400's. Ever since I bought a station, they last up to 300% longer than when I was CE....


Joe Jurkenas
WEXZ-LD
Bangor, ME