[AMRadio] New Project

[John Coleman]

For me, it's not about the power but the construction and how to arrive at
the parameters, such as bias, grid current, etc.  I'm not locked in at the
voltages and current I mentioned earlier, just a starting point.
The main thing here, is to try to construct it as much as is possible with
home made parts.  I want to do it with split stator capacitors, swinging
link tanks and all, but miniaturized.  Fully metered, no meter switches.  I
was thinking of building the plug in coil assembles using small banana plug
and jacks.  There are any number of ways to make the variably caps for cross
neutralization.  The split stator capacitors will be a pain though.

John, WA5BXO 
********************
-----Original Message-----
From: Brett Gazdzinski [mailto:Brett.Gazdzinski at verizon.net] 
Sent: Sunday, October 16, 2011 3:59 PM
To: jc at pctechref.com; Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] New Project

Why bother?
Because its fun.

The only problem using octal tubes is the plate and grids are close and all 
under the chassis.
That is not as much of a problem with push pull since you can neutralize 
them brute force.

A pair of 2E26's would be fun.

I always used to joke on the air I was going to build a water cooled 6aq5 
rig...

Brett
N2DTS

----- Original Message ----- 
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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