K3 birdies - question?

[Eric Scace K3NA]

Hi David --

   It was my oversight not to sent the concept to the reflector.

   However I will note that it takes a substantial amount of ferrite to
develop serious Z at HF.  I'm skeptical that a few beads at each end
will have a material effect... but perhaps someone will give it a go and
report a result.

   I also must recognize that the idea leakage is picked up on the
shield and conducted to an undesirable location is also speculative.  If
pickup is coming from the KREF or KSYN boards, then another approach
would be to place a shield around the offending (radiating) board.  But
that's a more complex task to try and raises issues of heat capture.

-- Eric

-------- Original Message --------
Subject: Re: [Elecraft] K3 birdies - question?
Date: Thu, 5 Mar 2009 17:19:34 -0000
From: David Cutter <[hidden email]>
To: <[hidden email]>
References:
<[hidden email]>
<[hidden email]>



Eric

That's an even better idea.  The tiny connector on the end will allow quite
a small bead/tube to be used.  This can then be taped or heat shrink and
somehow supported to stop it clunking about.

Thanks for the idea, why not put it on the reflector?

David
G3UNA

----- Original Message -----
From: "Eric Scace K3NA" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, March 05, 2009 4:22 PM
Subject: Re: [Elecraft] K3 birdies - question?

>I wonder if a string of suitable ferrite beads would be enough Z to kill
>anything on the shield of these short cables.  One would need to protect
>the ferrite from touching the circuit boards...
>
> on 09 Mar 05 05:24 [hidden email] said the following:
>> So, could we use the good old methods of wrapping the coax around a
>> suitable toroid.  That would mean a longer cable at which point I would
>> invest in a better quality cable if I were doing it and I'm tempted to do
>> so to get the best chance of cracking the main issues we are addressing.
>>
>> David
>> G3UNA
>>
>> ---- Geoffrey Mackenzie-Kennedy <[hidden email]> wrote:
>>> David,
>>>
>>> Double shielded coax would certainly reduce leakage from the coax, and
>>> is a good investment in my opinion. However its use might not have too
>>> much impact on the receiver's birdie problem, because many of the
>>> "rogue" signals involved are probably flowing on the outside of the
>>> coax's braid, certainly if the coax emerges from some enclosure through
>>> a hole.
>>>
>>> The usual cause of a receiver birdie is that some response of the
>>> receiver is "hearing" some oscillator or a harmonic, or some mixing
>>> product of two or more oscillators, contained within the receiver. In a
>>> down conversion HF receiver, the great majority of the receiver's
>>> responses, therefore the "rogue signals", that cause birdie problems are
>>> at HF and up to low/ mid VHF, which means that choking off coax runs
>>> within a receiver becomes cumbersome.
>>>
>>> 73,
>>>
>>> Geoff
>>> GM4ESD
>>>
>>> David Cutter wrote on Wednesday, March 04, 2009, at 10:32 AM:
>>>
>>>
>>>> I also wonder if it would be worthwhile buying higher spec coax.  Don't
>>>> know what is used in the K3, but for the lengths involved it would be
>>>> worth the investment to get short cables made in say LMR100 or RG142
>>>> etc if it's not already
>>>>
>>>> David
>>>> G3UNA
>>>>
>>>

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