[HBR] Fwd: Re: dual triode mixer - Pullen Mixer Notes

[donald haworth]

Thanks, Paul.  I have read the Pullen information.  I had built the mixer,
as described for the Collins receiver, using a 6es8.  My results were
so-so.  I did not see a great deal of improvement over a conventional 6be6
circuit-note this was used in a home-built superhet-not in the Collins
radio.  Walt's mixer circuit differs from the Pullen in that the plates are
tied together-therefor at the same potential, the Pullen drops the plate
voltage to the second triode by about 1/3, one could almost say it looks
like a cathode follower, but the Keets Pullen reference shows otherwise.
-As I understand it, Walt is using a dual triode, cathode(s) to ground via
a 470 ohm resistor.  The plates are tied together, then to the IF tank.
One grid is fed signal, the other is fed the LO signal.  Each grid has a
100k resistor to ground, as well.  From what Walt has posted, it seems to
be a good mixer.  I would like to know just how the thing works.  I also
would like to know what would work best--lo mu-- high mu dual triode- if a
tube with high transconductance would work better......I was thinking of
using two 6gk5's--super high gm- but I can find very little info on 'dual
triode mixers'--other than the Pullen info...
-best 73's
Thanks for you response!
Don

On Sat, Nov 19, 2011 at 8:25 PM, Paul Dulaff <pdulaff at embarqmail.com> wrote:

> Here is the link:
>
> http://aafradio.org/docs/Pullen.htm
>
> Paul - WB2NMI
>
> ----- Forwarded Message -----
> From: Paul Dulaff <pdulaff at embarqmail.com>
> To: HBR Receiver List <hbr at mailman.qth.net>
> Sent: Sat, 19 Nov 2011 20:24:02 -0500 (EST)
> Subject: Re: [HBR] dual triode mixer - Pullen Mixer Notes
>
> Donald
>
> I have attached a link to information on the Pullen Mixer. This is a dual
> triode configuration. The link contains information on theory of operation,
> correct design and biasing. Information is also listed for the reworked 1st
> mixer for the 75A-4 using this approach. I understand this implimentation
> works very well.
>
> Paul - WB2NMI
>
>
> ----- Original Message -----
> From: donald haworth <donmhaworth at gmail.com>
> To: HBR Receiver List <hbr at mailman.qth.net>
> Sent: Sat, 19 Nov 2011 14:46:11 -0500 (EST)
> Subject: Re: [HBR] dual triode mixer
>
> Walt.
> Can you tell me where I can find more info about the dual triode mixer?  I
> am planning to use a 6gm8....Can you tell me what led you to using the dual
> triode, rather than, say, a pentagrid type?
> -Sorry for all the dumb questions....but it just seems 'to good to be
> true'.  I really would like to know how the thing works.....I was also
> thinking of using two 6gk5's-a very high gm tube-
> -Your thoughts, please...
> Thanks Don (wb0rai) in Nashville
>
> On Mon, Nov 14, 2011 at 8:18 PM, Walt Hutchens <waltah at earthlink.net>
> wrote:
>
> > Donald:
> >
> > > As I understand it-both cathodes go to ground via a 470 ohm
> > > resistor, and the plates are tied together and go to B+ via the tank
> ckt.
> > > Unlike the Pullen which has different plate voltage on the two plates.
> >  Is
> > > that correct?
> >
> > That's it.  Couldn't be much simpler!
> >
> > Walt
> > KJ4KV
> >
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