[AMRadio] Valiant progress

Jim candela jcandela at prodigy.net
Sun Aug 28 14:04:48 EDT 2005


   Hear are the RCA data sheets from each typ of 6146. I haven't looked, but
maybe the mystery will reveal itself from the specifications.




I know from my 20a projects that using an EL34 / 6CA7 at RF up to 20 meters
is a formidable challenge, and not all EL-34's are the same. I was able to
get up to 50 watts peak with a single tube, and that was considerable PD
over-rate of the tube, and hence the little computer fan to cool it. I idled
at 40 ma cathode, and 600 volts plate w/o dc thermal run-away using a
Svetlana EL-34.



-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of John Lawson
Sent: Sunday, August 28, 2005 11:15 AM
To: amradio at mailman.qth.net
Subject: [AMRadio] Valiant progress

Thanks to Jim, Larry et. al. for the great advice on my Valiant
restoration project.

   I'm very interested in the common wisdom re: the 6146 variants that
'work' in this rig.

   Now, I've been a boatanchor fan since they were state of the art - have
done quite a bit of tube design, mostly audio though, and I do have quite
extensive documentation on most tubes made in the last 100 years.

   So really there's probably no excuse for this question other than
laziness - what exactly are the 6146 characteristics that the Valiant
design "favors" over the other variants? A freind who has re-built a lot
of these rigs says to only use 'plain' ones.  In my ignorance, I bought a
nice full set of 'W's and the transmitter wouldn't even resonate on
any band. ;{}  I put three 'B' s in the finals, and we're where we are now
- OK on 20M and above, 'runs away' below that.

    What do y'all recommend for Valiant finals / modulator tubes?

   On the HV B+ filter issue - mine are iffy, were replaced sometime in
it's history, but I'm going to renew them - what is the recomendation for
a more 'modern' replacement - keeping in mind that I'm looking for the
best AM fidelity I can squeeze out of this rig.


John  KB6SCO
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