[AMRadio] filament voltages

Roger Agnew k1kq at motorhomesusa.com
Tue Aug 17 20:59:25 EDT 2004


You got it right!

An old AM/FM Broadcaster,

Roger Agnew
K1KQ - Austin, TX

----- Original Message ----- 
From: "Donald Chester" <k4kyv at hotmail.com>
To: <amradio at mailman.qth.net>
Sent: Tuesday, August 17, 2004 6:08 PM
Subject: Re: [AMRadio] filament voltages

> >> > >Of course, we know that running voltages that are too high will kill
> >>the
> > > >life expectancy of the tube, by why is running too little voltage bad
> >for the
> > > >tube, if it's developing full emmission at a lower voltage?
> > >
> If the lower filament voltage does not affect the emission of the cathode
> peak plate current, it will not harm the tube.  But even if the average
> plate current seems normal, but the lower filament voltage limits the peak
> even slightly, tube life will suffer.
> The procedure with an AM transmitter is to modulate the transmitter to its
> maximum positive peak capability, with full filament voltage.  Then reduce
> the filament voltage until you begin to notice a dropoff of the positive
> peaks.  Run the filament voltage back up just past the point where
> peaks are fully restored.  The point is to run the filament just above the
> first indication that the cathode is being starved of emission.
> Don K4KYV
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