Rob, I can't believe you have not received an answer to your questions.
Maybe you have, bypassing the reflector. I keep a word document on info re
transmitting tubes. It has excerpts from postings which I am interested in.
Here is a quote from it.
" With a thoriated-tungsten cathode, there is virtually no increase in
output if the filament potential is increased above what is needed to
secure maximal PEP. The technique for adjusting filament potential is
exceedingly simple -- i.e., decrease fil. potential until PEP barely
drops. Increase fil. potential by 2%. By using this technique, up to
20k-hours of operation can be had between recarburizations."
I have seen similar info many places on the internet. It is widely
accepted that the life of direct heated tubes decreases rapidly as filament
voltage is increased and the above quoted technique is the way to go.
73, Dan, N5AR
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
Behalf Of rob
Sent: Tuesday, May 09, 2006 7:22 PM
To: amps@contesting.com
Subject: [Amps] 3-1000Z - Filament Voltage
Greetings,
I have a Harris RF-104 with a 3-1000Z tube. I have several questions
regarding the filament voltage.
The Eimac spec. sheet that I have lists the filament voltage as a nominal
value of 7.5 volts with no min or max values
shown (unlike the 3-500Z spec. sheet which has min/max values). The Harris
RF-104 that houses and powers the
tube has a spec. of 7.8 volts. As I've had to adjust the filament
transformer taps to achieve 7.8 volts (due to different
line voltage here), I was wondering if:
1. There a preferred voltage to run the filament at?
2. There a loss of tube life running the filament voltage too low or high?
3. There a practical tolerance for the filament voltage?
Any information would be appreciated.
... 73
Rob Brennen VE6TR
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