[Elecraft] K3 Birdies

[Giuliano]

My K3, 10w Kit version haven't remarkable Birdies, but
I am to order the second receiver unit KRX3.
So my question is: is the new option responsible of more Birdies?
thanks for any answer
73
I0cg
Italy



> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 10 Feb 2009 09:09:35 -0800
> From: wayne burdick <n6kr at elecraft.com>
> Subject: [Elecraft] K3 Birdies:  firmware-based fix in progress
> To: Elecraft Reflector <Elecraft at mailman.qth.net>
> Message-ID: <59aa74da58ea67722f9def82c0e2acf8 at elecraft.com>
> Content-Type: text/plain; charset=US-ASCII; format=flowed
>
> The K3 is a down-conversion superhet that uses high-level signal 
> injection to achieve its excellent dynamic range. Short of adding many 
> more pounds of shielding and elaborate cable dressing, there's no way 
> to completely eliminate the few spurious signals that rise above the 
> noise floor.
>
> These "Fast-tuning" birdies result from UHF harmonics of the signal 
> sources that leak back into the main mixer. In some cases they combine 
> and end up in either the I.F. or R.F./image range of the receiver. 
> Typically, they involve 9th-order or higher harmonics of the VFO. 
> That's what makes them "fast": if you move the VFO 100 Hz, the pitch of 
> the birdie will shift on the order of 1 to 2 kHz.
>
> While it is possible to attenuate some spurious responses by moving 
> coax cables around, there is a firmware-based approach that we're 
> working on. The general idea is to shift the 1st LO and BFO a small 
> amount, simultaneously, when the VFO is tuned to specific frequencies. 
> If the shift is small relative to the communications bandwidth in use, 
> it will hardly be noticeable when the VFO is tuned over a "mapped out" 
> spot in the tuning range.
>
> I have this new firmware nearly completed, and in early tests, it 
> appears to work very well. Fast-tuning birdies that are mapped out 
> pretty much disappear as the VFO is tuned over them. The upshot is that 
> you can have your cake (outstanding dynamic range in a rig that weighs 
> less than 10 pounds) and eat it, too (no annoying birdies).
>
> If you'd like to try a field-test version of K3 firmware that includes 
> this new feature, please e-mail me directly.
>
> 73,
> Wayne
> N6KR
>
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> http://www.elecraft.com
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