[Elecraft] KX-1 Ferrite question - background info for the request..

[Jack Smith]

In the 2-4 MHz band, if one absolutely must use a ferrite core for some 
reason or other, Fair-Rite 61 material would be a  reasonable choice. 
You might expect a Q in the 150 range, depending on inductance, wire 
size, number turns, etc. Type 43 Material at that frequency would make 
an excellent dummy load, and that's said with only very small exaggeration.

Powdered iron is a much better choice for this application in many 
respects, including temperature stability, Q, less chance of 
irreversible damage, etc.

Air wound inductors are even better but size is obviously a 
consideration. With either ferrite or powdered iron, the larger the core 
the better off you'll be when used for antenna matching or inductive 
loading.

Jack


Dave G. wrote:
> For those that might be ibnterested....
>
> FWIW - Using a KX-1+KXAT1, I'm trying to find a way to adapt the 
> (standard?) 
> ~26ft wire with 16ft counterpoise to work on 3.55Mhz...
>
> Here's what I've been thinking...
>
> I was initially considering modding the internal KAT1 toroids. The trick 
> there would be to get the three toroids to cover the whole KX-1 range.. the 
> probable outcome would not being able to get below an SWRof 2:1 or 3:1 
> on many frequencies with the existing antennae
> .
> But I remember (when I was G3UTY)  being mobile in London, UK  on 
> 160M with 10W. We used center-loaded 
> 8ft whips. Very large inefficient coils but we still managed to work the 
> european continent...
>
> So here's the situation, as I see it, looking at efficiensy and current/voltage 
> distribution;  and bearing in mind that, typically, most /P is done with 25-
> 40ft of wire.
>
> 1) End loading with L+C is probably out due to exremely high voltages and 
> also that's the end needed to hang the wire in the trees/fishing rod/etc... it is 
> still a possibilty.
>
> 2) Center loading with L only would be the next best. Middle range voltages 
> and current but it would mean hanging a small weight in the middle of a 
> length of (usually) very light wire. Might not be a practical solution..
>
> 3) Bottom loading which, in this case, is at the KX1 BNC connector....
> This gives the L minimum voltage with high current but also has the lowest 
> radiation efficiency. Hanging an extra bit of weight on the BNC connector 
> might not be such a good idea! So perhaps a short length of RG174 which 
> connects to the L (or an LC) circuit would be the best idea but /P operators 
> might 
> not appreciate carring an extra bit of wire in their Go pack!
>
> 4) Adding a coil to the counterpoise... in effect making the KX-1 directly 
> feeding an OCF ---- needs more thought  ;^-|
>
> Any opinions?? Thoughts? Suggestion?? 
> Ooops, better careful answering the latter  <Grin>
>
>
> --
> Dave G.   KK7SS
> '65 MK III Sprite in Richland, WA
>
> If life begins at 50, why am I falling apart ?!
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