[AMRadio] New Project

[Jack Dayton]

Catch ya on 29.050 :-)

Jack



________________________________
From: John Coleman <jc at pctechref.com>
To: 'Discussion of AM Radio in the Amateur Service' <amradio at mailman.qth.net>
Sent: Saturday, October 15, 2011 1:58 PM
Subject: [AMRadio] New Project

Well there will be many folks that will say "why bother", but I have a
little project in mind that I have been discussing with Geoff, W5OMR.  It is
just a little fun and learning project.
I want to build a push pull class C rig using a single 6SN7.

Max Plate Dissipation is 7.5 watts for both sections or 5 watts for each
So I plan to dissipate about 3 watts per section

Peak voltage rating is very high on the 6SN7 as is the peak current -
something like 1200 volts and 300mils.

I think I will run each section it at 400V on the plate and 30mils of plate
current.  That's 12 watts input per section or 24 watts input total.  This
should yield about 18 watts output.

The load reflection from the Tank is calculated 
Lz = Eb/2Ib = 400/.06 = 6666 ohms

I'll figure the tank circuit from that later.

At 400 Volts Eb, the charts show cutoff at about -30 to -40 volts grid bias

Class C is usually biased about 3 X cutoff so I will apply -100 to -120
volts regulated to the grid RF choke and drive it till I get max output at
60 mils plate current and then about 1.2 times more drive from my
experience. And then measure the grid current.  I'm expecting it to be about
5 mils of grid current, but that is just a guess.  I'll calculate a grid
leak from these findings for later use.

Anyone got any other ideas or experience with these little triodes as class
C devices.

John, WA5BXO






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