[AMRadio] Re: 4-65's

[Brett gazdzinski]

> > 
> Yes, but they're such a cute little toob. Actually I'm still 
> trying to 
> decide whether it will be the pair of 4-65s or a single 813.

The 813 will do 300 watts out at 2000 volts 200 ma all day long.
They also work well at lower voltages.

> 
> > If you were to build an RF deck that ran 3000 volts, its best to
> > build a modulator that runs 3000 volts, otherwise the mod 
> transformer
> > has a huge voltage difference between primary and secondary.
> > 
> 
> In my (planned) dual 4-65 rig*, I will run a 2500V common supply for 
> both the 811 modulators and the RF PA. I've run 811s at 2500V before, 
> and as long as you don't exceed plate dissipation ratings, they seem 
> perfectly happy about it.

I would use a pair of 100TH's or 100TL's rather than abuse 811's.
The 100TH makes a good match for the 4-65, both are rated to 3000 volts.

I would trade you some 100TH's for 811A's but I don't think tubes 
ship well, especially 100TH tubes.


> 
> *Actually, I'm still trying to decide whether it will be the pair of 
> 4-65s or a single 813.
>> You would need a multimatch mod transformer so you could 
> turn it around.
> > 
> Or, if you do it that way, flip around the primary and secondary 
> (assuming the secondary has a center-tap). Or is that what 
> you mean by 
> "turn it around?"

Yes. A regular mod trans usually does not have a tapped secondary.

I know how it goes, sometimes you have to build a rig to use some
really neat parts or tubes!

Brett
N2DTS