Fw: K2 Tuner?

[Jim AB3CV]

Don/Leigh

Thanks for the quick replies.

I'll try the K2/KAT2 nekkid for this Thursday's 20m fox hunt unless I can
adapt one of my ferrite bead coax chokes by then. I normally use a remote
tuner but it has died again, this time outside the warrantee period. I plan
to return it to see what they say but I'm not optimistic.

I'm going to try using a T1 as my remote tuner in any case. As a first try
I'll just connect my feedline from the antenna to a BNC-bindingpost adapter
to see how it tunes. I can insert a BL2 which I've ordered set at 1:1. I'll
also add a ferrite bead coax choke for good measure to reduce any common
mode currents on the coax from the shack to the tuner. I'll probably try the
ferrite bead choke first.

73

jim ab3cv

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[AC7AC]

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[Don Wilhelm-3]

Ron and all,

Thanks for 'singing my song'.  I have long advocated that the
antenna/feedline system is influenced by the electrical position of the
(electrical) ends of the antenna than any other factor.  No matter how
you analyze an antenna, the current at the end of an antenna wire must
be zero.  Think about it and you perhaps come to the realization that it
is a fact and is more of an influence in determining antenna balance
that any balun or other choking device.

Where a choke balun is important is in decoupling the *outside* of the
coax braid from the current on the inside of the braid.  Even in coax,
the current is balanced if you consider the current on the center
conductor and the inside of the shield.  However, when the current on
the inside of the shield reaches the end of the coax, it finds 2
conductors - one is the antenna wire or one side of a parallel feedline,
and the other is the outside of the coax shield.  The RF current will
dutifully split onto both conductors if there is no means to prevent it.
  So the result can be that RF is coupled back to the operating position
on the outside of the coax shield.  That can unbalance the currents on
the antenna or parallel feedline since the 'end' of that side of the
antenna has changed into a complex form rather than a simple length of wire.

Think about it a while and you may come to the same conclusions.

73,
Don W3FPR


Ron D'Eau Claire wrote:
> snip...
> I have measured the current in each leg of the feed line with an unbalanced
> tuner and no balun and found it very well balanced. The balance in the
> currents seems to have a lot more to do with the load (antenna) than the
> source.
snip ...
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[Jim AB3CV]

Just got in from the porch where the windowline is being fed directly by the
K2 via a BNC-banana jack adapter.

Antenna tuned to less than 1.4:1 from 160 to 10 around the usual QRP CW
watering holes.

That is good enough for now until I can get the stuff together for remoting
the T1.

73

jim ab3cv

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[Leigh L. Klotz Jr WA5ZNU]

That will work OK for QRP battery portable, but it is floating your rig
chassis above RF ground.  In the shack with a power supply, the power
supply and its ground will become part of your antenna and will radiate,
perhaps degrading performance.

To see the effect, test if you get different SWR (or RX sound) when
touching the rig vs. not touching it.  A balun even at the base of the
rig, or on a short coax jumper, will eliminate these effects.

73,
Leigh/WA5ZNU
On Wed, 1 Aug 2007 12:44 pm, Jim Miller wrote:

> Just got in from the porch where the windowline is being fed directly
> by the
> K2 via a BNC-banana jack adapter.
>
> Antenna tuned to less than 1.4:1 from 160 to 10 around the usual QRP CW
> watering holes.
>
> That is good enough for now until I can get the stuff together for
> remoting
> the T1.

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[Jim AB3CV]

i agree a balun is preferred. i ordered a bl2 last night which i'll use in
1:1 mode.

it will get used on the k2 for now and eventually on the remoted t1.

73

jim ab3cv

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