[AMRadio] Fun with 4D32's...


Brett gazdzinski brett.gazdzinski at verizonbusiness.com
Tue Jan 2 09:11:04 EST 2007


I looked at the homebrew pair of 4D32 rf deck over the holidays,
and since there was room on the deck, and I had a socket and
plenty of 4D32's, I installed a 3rd one.

It worked out very well, I now get 300 watts of carrier and
1200 watts pep out, running the rf deck and modulator
at 1250 volts.
The power supply is good for the power, but a separate
power supply for the modulator would be nice, and increase
the peak power through better regulation.

I also ran the pair of 813's, and had some odd stuff
going on, peak power was down, power cord got warm, 
15 amp ckt breaker would blow after an old buzzard,
and I found the shunt on the plate voltage meter on 
the power supply was off and reading about 700 volts low,
so I was running the 813's at 350ma and about 2800
volts, I think the meter reads more off the higher
the voltage, and an indicated 2000 volts is something
like 3000 volts!
No wonder the power cord got warm!

I got to fix the meter on the power supply, but
look at the volt meter on the RF deck for now.

I also tried out the push pull parallel 100TH mod deck,
which happens to be a perfect match to the mod iron
at 2250 volts, 10,400 ohms.
It took more driving power then the 4x150a mod deck
but sounded good....

With 4 100TH plates behind glass glowing orange, I
get radiant heat for the shack!

I have been looking at balanced antenna tuners, I think
I need to build a big one, somehow making a huge coil
out of copper tubing.

The design in the ARRL handbook uses one B+W 
3 inch coil stock with 2 tapped link coils switched
in series or parallel, with tuning cap, and
the output coils are tapped for each band.
I don't want to have to move jumpers and so on,
so I like that design, but a 3 inch coil of 
number 14 is good for 250 watts of AM carrier per the 
book!

How to make a nice coil of the size needed?

Brett
N2DTS






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