Mike:
I am not an expert on these things, but I agree that this doesn't sound
normal, and may be a sign of one or more bad tubes.
As for replacement tubes, I decided to go with 572B's, rather than 811's. I
was advised to bite the bullet and get a matching quod (i.e. set of four
tubes), rather than buying individual replacements. This way, the tubes are
equally used, with less likelihood of causing damage to any remaining good
tubes in the tuning process, and when transmitting.
I got my matching quod of 572B's from RF Parts, back in the Fall of 2009,
for a little over $200.
I could have gotten a set of four 811's for about half the price, but
decided to go with the more robust tubes, especially since I was learning
the tuning process at that time, and wanted to give myself a margin of
error, if you know what I mean.
If you want to contact RF Parts, their phone number is:
(770) 614-7443.
Tom Behler: KB8TYJ
I wouldn't think the price would have changed much between then and now.
Let's see what others with more experience than me might have to say about
this issue.
Tom Behler: KB8TYJ
-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of Michael Ryan
Sent: Sunday, March 16, 2014 3:56 PM
To: [log in to unmask]
Subject: Tuning the 811H
Hi Tom and Alan:=20
As users of the 811H, I'd paid particular attention to my load control =
settings over the weekend and I discovered something strange.=20 =46rom the
starting position, I find that if I rotate the control = counter clock wise,
the pitch on my TW-1 steadily rises.=20 I don't think this is the norm. When
completely tuned, with the max = drive, again if I move the load control
counter clock wise off the 3 = position, again the pitch steadily increases.
I don't think this should = be the case. However, shouldn't I just trust the
TW-1 and adjust the = load and plate controls until the max pitch is
obtained? After tune up, = I'm sure if I do that, the load control will
possibly move down to the 2 = mark. perhaps even lower. I'm also seeing a
reduced output on 20M, 450 = with 60 of drive and that could be an
indication of one of the tubes =
going.=20
I didn't check the SWR between the 102 and amp but after 30 minutes of = 20M
operation yesterday, my 102 was pretty warm to the touch. Allot = warmer
then on 40M or 75M, where I get 600W with 50W of drive. So I may = have a
higher SWR between the rig and amp and this is another sign of a = bad
tube.=20 This isn't good news as RF Parts doesn't have a good supplier of
811s or = 572Bs at the moment and I don't know how good the Chinese made
tubes = really are. Very poor quality from what I've heard.=20
73:=20
Mike VO1AX=20
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