[HBR] Need help with noise

[Ian Wilson]

I noticed somewhat belatedly that the HR-10 coils for 40 and 80m on
the plate side have a 2.2k resistor in parallel with each, presumably
to stop the original 6BZ6 from taking off. Removing this causes the
6EJ7 to become untamable, so I have some work to do there.

With the RF amp replaced by a 5pF capacitor (turning the two LCs
into a sort of double tuned preselector), the receiver behaves way
better, with what I regard as normal S/N for a not-very-narrow BW
system (the IF filter is 2.5kHz wide).

My intention for the RF amplifier was to provide a small amount of
gain (for poor antennas) with a manual RF gain control to act as an
attenuator for strong signals. I expect the 6EJ7 to have good intermod
characteristics, if I can get it tamed.

Will get back to this receiver in a week or two. I think it will work a lot
better if I can, indeed, rethink the front end.

73, ian K3IMW



On Fri, Jan 17, 2014 at 7:04 AM, Mike Hanz <aaf-radio-1 at aafradio.org> wrote:

> On 1/17/2014 9:28 AM, Walt Hutchens wrote:
>
>> The mixer is the most likely victim and in my
>> opinion the Pullen has a kick me sign on it.
>>
>
> I've never had a problem with getting the Pullen circuit to work well, but
> I've probably simply been lucky with component selection and voltages.
>  Just curious, Walt - have you ever thought about using the variable mu
> capability of a 6ES8 in a Pullen mixer with AGC?  Keats Pullen mentioned
> the possibility to me at a hamfest years ago but had no data on it.
>  Perhaps a balanced mixer using two 6ES8s to eliminate the even order
> harmonics and gain varied with AGC?  It would still need a 6ES8 preselector
> in front like the G2DAF design, of course.
>
>      Very 73,
>  - Mike  KC4TOS
>
>
>
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