[AMRadio] New Project

Mon Oct 17 08:51:38 EDT 2011

I wish that someone would drop by and look over my assortment of BW 
coils/split stator capacitors, etc.  I still have several kw butterfly 
capacitors and KW coil sets. But, no one knows the way to "Santa Fe" or 
Sidman, PA.

Could ship but then I would have to take pictures, haggle prices, myriad of 
emails back and forth, etc. etc.

Love
David Knepper, W3CRA/W3ST
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----- Original Message ----- 
From: "John Coleman" <jc at pctechref.com>
To: "'Discussion of AM Radio in the Amateur Service'" 
<amradio at mailman.qth.net>
Sent: Monday, October 17, 2011 8:36 AM
Subject: Re: [AMRadio] New Project

> 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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