[Elecraft] [K3] KAT3 and 160 with 40m long doublet

[Fred Jensen]

On 1/2/2011 2:39 PM, Tony Estep wrote:

> A short antenna just presents a
> capacitive reactance (a -j value) to the tuner, which in my experience the
> KAT3 has always been able to deal with.

Well ... I think it sort of depends on the antenna and the length of the 
feedline if it's surge impedance isn't matched to the antenna feedpoint. 
  Short Marconi-T's and Inv-L's typically will have some inductive 
reactance when fed at the bottom, hence the usual series cap.  And, what 
Z appears at the TX end of the coax depends both on the mismatch at the 
feedpoint, and the length of the coax.  W3FPR has suggested multiple 
times that, if all you're looking for is a match by the KAT3 so your K3 
will be happy and exude power, try adding 1/8 wave of coax to the line.

Of course, just getting a KAT3 match doesn't mean you're getting a lot 
of power into a short antenna or that it will radiate [or receive] well.

I guess there's a reason why those old coastal marine stations had such 
huge antennas :-)

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org