[HBR] Birdies

[Ian Wilson]

Sometimes it can be very difficult to tell which signals are causing
the interference. High harmonics of the BFO can mix with lower
harmonics of some other oscillator, for example. You can sometimes
get a clue by observing how fast a birdie moves relative to the tuning
control - a fast-moving birdie indicates a multiple of your variable
oscillator is involved.

There are programs that will calculate mixing terms that fall within a
given window, but in a typical superhet there are too many such
windows, and the number of potential interferers is just too large
to manage (in my limited and frustrated experience, anyway!).

73, ian K3IMW


On Mon, Jan 12, 2015 at 8:08 AM, Brian Burns <brian at lessonsinlutherie.com>
wrote:

> Hello All,
>
>
>
> Thanks to the generosity of Larry Baker WB5OFD I'll be getting an HBR-8 by
> UPS this afternoon. Larry describes it as " rather beat-up", and "It would
> probably make a good parts rig for a new build from original parts."
>
>
>
> I'll have a good look at it to see if it's worth re-furbishing, or whether
> I
> should start from scratch. In either case, I'm interested in knowing how to
> keep the "birdies" in their cages. That might even be an appropriate
> metaphor, as I suspect that one answer is shielding, though with a bit
> tighter mesh than you find in a bird cage.
>
>
>
> With the commercially made receivers that I have used, even single
> conversion, the extraneous whistles on the higher bands due to local
> oscillator harmonics have been quite annoying. So, any suggestions that you
> might have for mechanical or electrical configurations to quiet our "fine
> feathered friends" would be most appreciated.
>
>
>
> Cheers,
>
>
>
> Brian
>
>
>
>
>
>
>
> ---
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