[AMRadio] Re: Minature Mobile Transmitter


Mike Dorworth,K4XM k4xm at arczip.com
Mon Oct 3 20:03:09 EDT 2005


The resting current is total for both sections. 10 ma would be 1.5 watts per
section at 300 volts. Peak current is 35 ma total for the two sections.
Works very well. Tube life not a problem. These were used for years in
mobile requiring a total of 100 ma for final, osc and modulator. The last
ten ma were taken from a large output capacitor when total current was about
110 ma on a 100 ma system.A single 12AU7 was used for mic preamp and driver,
consumed about 4 ma. Current was measured in mills by each ma Not a single
one was wasted. 6 volt cars were lucky to have a 15 to 30 amp Generator.
Even as late as the mid fifties on 12 volt cars a 35 amp alternator was
special factory order. No one wasted MA in mobile. Hence the zero bias
tubes, 1635 and 12AX7. A 1635 will modulate 100 percent a 50 watt rig and
automatically hi level clip and increase talk power without splatter.The
Johnson Mobile used bias for the modulator, look up the circuit on BAMA!

----- Original Message ----- 
From: "Patrick Jankowiak" <recycler at swbell.net>
To: <amradio at mailman.qth.net>
Sent: Monday, October 03, 2005 7:06 PM
Subject: [AMRadio] Re: Minature Mobile Transmitter


> What I don't get is the tube current ratings, and, was tube life a
concern?
>
> 300V zero bias gets you 8mA per section, and is also 2.4 watts
dissipation!
> I suppose these are the ICAS ratings :-P
>
> -and that's zero signal. The curve is very linear from 2mA to 8mA and even
> pretty good down to 1mA idling current.  -but those would take bias.
>
> PJ
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