[AMRadio] RE: Yet another receiver update!

[Brett Gazdzinski]

David,
Sorry about the delay.

No, but I used to run a 4-400 modulated by a pair of 100TH
tubes in my 30k-1.

I don't like 4-400's much.

They come alive above 2500 volts, better at 3000.
At lower voltages, they are inefficient, as in the globe
king 500 running them at 1800 volts or so.
540 watts in and 300 out....and that is what I got.
(that stinks)

At 3000 volts, they get up around or over 70%.

In the 30k-1, I ran 2500 volts at 150 ma, 375 watts in,
and I got 300 or more out.

The 100th's are high voltage tubes also and like 2500 or
3000 volts.

I never had a problem with the 30k-1 at that voltage,
but would not like to take things above 2500 volts.

I worry about the mod iron with voltages above 2000 volts.

Mixing a 4-400 running 2500 volts and 805's is probably
not the best bet, as 805's are a lower voltage tube.
Maximum ccs ratings are 1500 volts on 805's.

A pair of 100th's or 100tl's will give you 450 watts
of audio at 3000 volts.

You could run the 4-400 at 500 watts out, and the 100th's
would be plenty to modulate it with!

100th/tl's are fragile tubes though, both the filaments
and the grids...you might not want to get them through
UPS!

You can also modulate 4-400's with 4-400's.
I have heard some good sounding rigs with 4-400 modulators.
Takes a bit of work though...



I much prefer lower voltage tubes, say a pair of 813,s
modulated by whatever you have.
Depending on what you have for modulator tubes, you can run the 
813's anywhere from 1000 to 2500 volts, although 2500
is pushing it.
2000 volts is good, they will do 400 ma all day long,
modulate very nicely with lots of peak power.
My 813 rig can do 650 watts of carrier and its off
the scale of the watt meter at 2000 watts pep.
judging by the way it hits the pin, its way over 2000 watts
pep.

A single 813 modulated by a pair of 811a's would work
at 1500 volts.

There are all sorts of combinations, it should be 
driven by what you have on hand, the power you need,
and what you like.

I don't need much power, I mostly run the push pull
812/811 rig at about 250 or 300 watts.
On 40 that is more than enough.

Brett
N2DTS
 

 
> Brett, heard you on 40 meters yesterday.  Very nice signal here near
> Johnstown, PA
> 
> Question:  Have you ever built a transmitter using 4-400's 
> modulated with
> 810's or should I use 250TH tubes to modulate a pair of 
> 4-400A's.  Thank
> you.
> 
> David Knepper - W3ST
> Publisher of the Collins Journal
> Secretary to the Collins Radio Association
> CRA website:  http://www.collinsra.com
> 
> -----Original Message-----
> From: amradio-admin at mailman.qth.net
> [mailto:amradio-admin at mailman.qth.net]On Behalf Of Brett Gazdzinski
> Sent: Saturday, March 16, 2002 10:53 PM
> To: amradio at mailman.qth.net
> Subject: RE: [AMRadio] RE: Yet another receiver update!
> 
> 
> Bill,
> The little parts look somewhat reasonable in price.
> Better then e bay anyway.
> I found various caps in the junk box, and had ordered some
> npo caps from Mouser...they were not cheap either.
> 
> As for slug tuned coil forms, no place else seems to have
> the big ones.
> 
> All this old stuff is getting expensive, that's just
> something to expect when things are not made anymore...
> 
> Brett
> N2DTS
> 
> >
> > You mean you can't get a lifetime supply of npo variables
> > from a couple
> > old Tectronix scopes (the tube type), especially the plug-in units?
> > Currently these have negative value (they'll pay you to
> > remove them) and
> > are chock full of goodies.
> >
> > Don't pay SS's ripoff prices!!
> >
> > Bill
> 
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