[AMRadio] Class C modulation

[Todd Bigelow - PS]

Just slightly orange, Jay? Mine used to get *quite* orange and pulsate with the
voice peaks. In fact, when I first got the rig and powered it up, they got just
plain orange and tossed fuses left and right, due to a lack of bias from an open
4-pie choke just behind the front panel. Luckily the wire was broken just at the
point where it was soldered to the terminal on the choke, so I didn't even have
to look for a new one. Thanks to Mr. Bill Wheeler, K0DEW for the help on that
one. I called him, we both got our schematics out and went through until
we(okay, he) found a likely suspect.

What the old timers told me was that using 4-400s in place of the 4-250s
wouldn't give me more power, it would just allow the transmitter to loaf along
with perhaps a 'mild' glow of the plates and less strain on the rig overall. As
explained, the 4-400C was the best choice, and the 4-400 series in general was
just a more stout or 'rugged' version of the 4-250, lending itself better to the
higher power requirements that came along after the 4-250.

*shrug* I haven't a clue. I had the assitance of a former broadcast engineer in
getting the rig online, so I figured he knew his stuff(he's a ham as well). And
of course, some really good suggestions from Uncle Ed WA3PUN and the gang down
his way the first night I dared to transmit. Hey, these 'suggestions' didn't
require drilling any holes, and are reversible, so...

After moving to my new home, the old girl was back to spitting out 15 amp fuses.
I need to set some time aside and dig into it a bit more. Something either got
jostled in the move (only about 15 slow, careful miles)or decided to go south in
the time it sat unused.

I do recall that the 4-250s seemed prone to shorts, though. Just reach in with a
broom handle and rap 'em a bit and they were fine....

73 de Todd/'Boomer'  KA1KAQ

Jay Bromley wrote:

> Hi John and all,
> I had some 4-250s in the final of my old KW-1, then later switched them out
> to 4-400s.  While I liked the looks of the slightly orange plates of the
> 4-250s and under modulation the 4-250s getting brighter in color, the 4-400
> seemed to work better with the 810s modulators.  I can't show any proof, but
> it just seem to modulate and have more headroom.  Was this in my head??  All
> I had to go by was my monitor scope.
>
> 73 de jay/w5jay..