On Sunday, November 2, 2003, at 09:48 AM, RFlabnotes@aol.com wrote:
I have an old 30L1, which has been in and out of use here for some
time. It
has also been the cite of several interesting ( and not always
successful!)
enhancements. I found it quite easy to modify the meter circuitry to
read grid
current, in place of the infamous 'TUNE' position. This, along with a
wattmeter
in the feedline, makes it possible to quickly and easily get it
optimized at
full output without hosing the 811A (or 572) grids.
*** The problem is not with the 811A grids, it's melting holes in the
811A plates/anodes due to the increased velocity of electrons because
Collins Radio used more than the rated anode V.
If you are interested, drop
me a line and I will send a copy of the page in my lab notebook which
documents this, as well as data for conversion to 572's for 1KW+
output.
*** Eric -- T160L/572Bs and 811As use the same filament, and therefore
have the same peak emissive ability. For SSB, up to c. 1800VDC, there
is no difference in PEP output between an 811A and a 572B. The
advantage of a 572B is that its graphite anode is good for 2400VDC, a
potential that will easily damage the thin metal anode of an 811A.
Eric von Valtier K8LV
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Rich Measures, AG6K, 805.386.3734. www.somis.org/
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