[Elecraft] Tunable carrier (birdie) 20445khz

[Don Wilhelm]

Ron and I will have to just disagree with the definition of a "birdie" - 
and it is only a matter of definition.

My definition is the result of multiples of the various signals and 
oscillator frequencies present in the receiver, and since they are 
always multiples greater than 1 of any signal (or oscillator), will 
always result in a fast tuning response.

OTOH, there are unavoidable mixing products in any down-conversion 
receiver that will tune as a normal signal.  The goal of the designer is 
to choose the IF frequencies to keep those spurious responses out of the 
bands of interest to the target users - in this case, the ham bands.

So, if your definition of "birdies" agrees with Ron's, so be it - I will 
continue to refer to extraneous direct mixing products (those responses 
that do not produce fast tuning signals) as spurious responses.  It is 
just a matter of definition.

BTW, this is one of the advantages of up-conversion - those direct 
responses are so far away from the desired signal that they do not 
become troublesome, but up-conversion designs have their own share of 
troublesome problems.

73,
Don W3FPR


On 8/20/2011 8:06 PM, Ron D'Eau Claire wrote:
> I show one birdie here. It's a "normal tuning" (not double rate) birdie which, with great respect for Don, I will disagree with him and say that not all birdies tune at accelerated rates if one defines a birdie as an internally-generated unwanted signal. That birdie is at about -100 dBm.
>
> If I turn on the preamp and connect a dummy load, a row of lower level birdies does appear, but they are completely buried in normal band noise (here at -140 dBm) with an antenna connected.
>
> As others pointed out, you can try moving TMP cables or, more simply, applying the "birdie removal" software. The latter does not cause a hole at that frequency. It just moves the oscillator frequencies around as you tune to that frequency so that when you are tuned there the birdie is somewhere else.
>
> Ron AC7AC
>
> -----Original Message-----
>
> Thanks for the suggestions guys - for those of you with P3's - tune to
> 20445.11 on CW nor mode and take a look with the span on the P3 set at
> 200khz. A regular picket fence of birdies! (at least on my K3)
>
> 73 Gill
>
>
> --
>
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