[ARC5] [glowbugradio] Suppressor grids and pentodes.

[Geoff]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "mac" <w7qho at aol.com>
Cc: "ARC-5 Mail List" <arc5 at mailman.qth.net>
Sent: Thursday, January 31, 2013 3:47 PM
Subject: Re: [ARC5] [glowbugradio] Suppressor grids and pentodes.


> On 31 Jan 2013 at 10:35, mac wrote:
>
>> > Ken,
>> >
>> > Presume the authors meant "will oscillate" if left ungrounded and
>> > floating for both DC and RF?
>
> He never menitioned RF...
>
>>  Then I guess they applied a controlled
>> >  positive bias to it and got a controlled regeneration
>> > characteristic?  Suppressor bypassed to ground for RF in this lash-
>> > up?  What was the diode for?  Can you publish the circuit....
>> >
>> > Dennis D.  W7QHO
>> > Glendale, CA
>
> Yes. To all the above questions. The diode was used as a DC controlled
> variable resistor between the suppressor and ground.
>
> The controlling element, a 2K pot, was mounted on the front panel, while 
> the
> diode and the other bits were mounted at the tube socket.
>
> The diode is connected from the suppressor to ground, Cathode towards
> ground. One end of a 1.5 K resistor is connected at the junction of the 
> diode
> and the suppressor. The other end of that resistor is connected to 1) a
> 10MFD 35V cap with its negative end grounded, and 2) to a line connecting
> to the wiper of the 2K pot. The hot end of the pot is connected through a
> dropping resistor (100K in this case) to B+. The cold end of the 2K pot is
> grounded.
>
> There is no RF bypass capacitor "around" the diode, possibly to enhance
> "regeneration". Perhaps it simply wasn't needed. I have not yet tried the
> circuit nor closely examined its operation.
>
> As I have time, I'll publish the schematic and other info on my website at
> www.w7ekb.com/glowbugs/
>
> Kenneth G. Gordon W7EKB


It sounds like a Hallicrafters guy wrote that article.
http://bama.edebris.com/manuals/hallicra/sx140/

Carl