[AMRadio] 4-65's


Geoff/W5OMR ars.w5omr at gmail.com
Thu Apr 5 12:43:43 EDT 2007


Jim Candela wrote:
> Geoff,
>
>    I used a pair of 4-65's in a Globe Champion 350 conversion from AX9909's. This was kind of tricky to do, but since I had the tubes, and the sockets were the same, i gave it a try.
>
> Some recollections from that conversion:
>
> The 4-65 is a Higher voltage, and lower current tube. In class C service, the efficiency is really great at 3kv plate voltage, and is diminished at lower voltages.
>
> Used 4-65's like a lot of thoriated tungsten tubes have a filament that is very brittle, and therefore shipping them is risky since the filament might be rattling around when you take them out of the box. The 304 TL is also a good example of this.
>
> In the Globe 350, with a beefed up plate supply (~ 1500v instead of 1000), I could easily run 500 watts DC input at about 80% efficiency, The in/out ratio was pretty constant from 160-10m. The tubes had little color. The only fly in this conversion was that I wired the two tube filaments in series to use the existing 12 volts AC for the 9909's. This resulted in some 60 hz cathode modulation making the rig sound like a BC-610 running on the internal VFO.
>   

Good to hear from you, Jim.

I'm not too interested in running a pair of 'em in the final... 150/200w 
seems to be all that's needed around here to talk locally, and perhaps 
greater distances when conditions permit.  I can't remember the last 
time I had the 250TH rig up to 500w DC input.  Hell, I think I might do 
that, tonight.

anyone up for some late-night AM?  I'll be on post 12midnight Central 
time on 3.881 or 82, providing there's not a lot of hearable traffic on 
3.885.

Oh, I can hear the groans, now; "Not in the AM Ghetto!" ... and it might 
prove out that I'll probably move down to 3.725, but we'll see how the 
'Magnolia Net' is going, at midnight.

Besides that, I ain't skert!  Bring 'em on.

--
73 = Best Regards





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