[BC] BC-1G Advice/alternative tubes

[dynotherm at earthlink.net]

-----Original Message-----
>From: Bob Groome <bobgroome at yahoo.com>
>Subject: Re: [BC] BC-1G Advice
>
>Bauer Xmitter Co started out with 4-400's went
>5-500's then back to 4-400's as I recall. The
>offered field kits for the changes. Don't know
>what other boxes these would work in, but you
>could check with Bauer (they are still in
>business in Texas).

The change in load line between 4-400 and 5-500
is very small thus the impedance presented to
the modulator similar. The main difference is
the filament voltage and current. 

Unless different PA tube types operate at essentially
similar Ep and Ip constants the Rp will not be close
hence the impedance presented to the modulator 
would be a mismatch and modulation will suffer to
some extent.

By eliminating iron, PDM does simplify the power
portion of the circuitry.

Phil Alexander, CSRE, AMD