On Thu, 04 Feb 1999 00:33:29 +0000 w7iuv@axtek.com (Larry Molitor)
writes:
>
>The need to add my $0.02 to this thread has become overwhelming. So
>here is
>something that at least a few of you might appreciate.
>
>I copied this chart out of a book some 25 or 30 years ago. I don't
>recall
>the title and recently a search failed to find said book in my
>library. No
>matter, I made copies of this chart and keep one in my desk at work,
>one in
>my shack file, and one posted next to the TP dispenser in the head.
>
>Those of you who are clever enough to keep your email software set to
>display a fixed font may actually see this in table format.
>
>
>TUBE Ep Ip Cathode ohms
>
>811A 1250 175 320
> 1700 160 320
>
>572B/T160L 2400 250 215
>
>813 2000 200 270
> 2500 200 270
>
>3-400Z/8163 2000 400 120
> 2500 400 120
> 3000 333 120
>
>3-500Z 2000 400 115
> 2500 400 115
> 3000 370 115
>
>3-1000Z 2500 800 65
> 3000 670 65
> 3500 750 65
>
>3CX1000A7 2500 875 41
> 3000 800 42
>
>4-125A 2000 105 340
> 2500 110 340
> 3000 115 340
>
>4-400A 2000 265 160
> 2500 270 150
> 3000 330 140
>
>4-1000A 3000 700 104
> 4000 675 106
> 5000 540 110
>
>
>Subject to any typos I may have made, this is an abbreviated version
>of the
>chart I copied many years ago.
>
>Obviously the tetrodes are Triode-Connected-Grounded-Grid. The only
>claim I
>can make is that the data has been spot on for all the tubes I've
>tried.
>It's so close that I no longer put adjustments on the components in
>the
>cathode pi-net.
>
>By the way, leave the damn tube in the socket when you measure the
>network
>match. Why tack in a cap to synthesize the tube capacitance when you
>have
>the real thing. Besides, why put more wear on the socket contacts. I
>always
>have the whole thing together including the entire anode compartment
>before
>doing the cathode network.
>
>Using this method, I can usually turn on the amp and not see the SWR
>meter
>on the exciter even wiggle at full power out. While other methods may
>have
>some theoretical advantage, they have no practical merit in my
>not-so-humble-opinion.
>
>I hope someone gets a little use out of this, it took me a long time
>to
>type it all in with two fingers.
Thanks for all the typing Larry. I believe that info came from a CQ
article by Bill Orr back in the mid 60's. Some other charts are in
various versions of the ARRL SSB manual but Orr by far often puts out
more info in one article than the ARRL does in a manual.
I stay out of these input network debates since I have always followed
the same approach as you with nary a problem. Seldom have I seen so many
complicate such a seemingly simple issue.
BTW, Omega Electronics sells a complete input network that is relay
switched. It is available pre-wired for several popular tubes or a
"universal" version is available. A real no brainer for those without
gobs of test equipment or the time to reinvent the wheel.
73 Carl KM1H
>
>73,
>
>Larry - W7IUV
>w7iuv@axtek.com
>http://www.axtek.com/w7iuv
>
>
>
>
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>
>
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