[AMRadio] Re: VK1 813 rig

Brett gazdzinski brett.gazdzinski at verizonbusiness.com
Mon Jul 30 09:06:00 EDT 2007

A 4D32 is good for about 100 watts of carrier out,
but to get good modulation peaks, they seem to like higher plate
voltages, above 800 volts say.

I am not sure if it's the screen or a lack of peak emission, but
I find if you run them at say 600 volts they just don't make a lot
of positive peaks.

Between say 900 and 1250 volts, they make plenty of positive
peaks though!

In my case, they really seem to love the 1250 volts, and I have tried
them at 1500.

At 1250, I run them at about 100 ma per tube and they seem
to run cool...no color on the plates, no forced air.

You can run them at 600 volts and 200 ma per tube, and
they do fine, except the positive peaks maybe...



> -----Original Message-----
> From: amradio-bounces at mailman.qth.net 
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Geoff/W5OMR
> Sent: Friday, July 27, 2007 3:30 AM
> To: Discussion of AM Radio in the Amateur Service
> Subject: Re: [AMRadio] Re: VK1 813 rig
> DOXEMF at aol.com wrote:
> > Jim Candela writes:
> >>  used an outboard power supply for the 8417's producing 
> about 550 volts and 300v (regulated). I could get about 150 
> watts output pretty easy with that rig and still have good AM 
> performance. I had a 125w Stancor polypedance mod 
> transformer. This was a 160-40 rig only.<
> >>     
> >
> > I see, you didn't get 100% mod with that low of a supply.
> >   
> he got -more- than 100% modulation out of that rig.  The 
> 8417's were the 
> modulators, modulating a single 813.  Worked like a hose, from what I 
> remember.  He might have had (4) 8417's
> > Been thinking of squeezing a pair of 4D32s ala Bretts final
> > sort of so as to keep the voltage lower but current up. The 
> stock VK supply has at least 500 ma available without the 
> onboard modulators.
> >   
> Pair of 4D32's?  That'd be around 200 ~ 250w, right?  Pair of 811's.  
> They're just great tubes, for class B stuff.
> --
> 73
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