[Elecraft] OT: K3 and antenna questions

[Don Wilhelm]

Dave,

Yes, the law of reciprocity applies on both TX and RX, but the K3 has a 
better receiver,  so it is entirely possible for you to hear ones that 
you cannot work.  His signal report to you indicates that is likely the 
case.

Try your antenna without the balun - you should not notice heating at 5 
watts unless there is considerable loss (maybe it was the sun shining on 
the balun :-) ).  Usually in multi-band QRP field operations, a slightly 
unbalanced antenna radiation pattern is not a problem.  If you end up 
with hot RF on the chassis, you can alter the feedline length to bring 
the impedance down and make the antenna easier to feed.  Your current 
radiator plus feedline might have a high impedance at the rig end on 40 
meters and up (the total feedline plus one leg of the antenna is near a 
half wave on 40m).

73,
Don W3FPR

Dave Van Wallaghen wrote:
> I apologize for the bandwidth, but I really trust the sources of info here
> and it may help someone else starting out like me with specific K3 info and
> antenna theory.
>
> I've been playing around with my K3 in a portable capacity out in my yard.
> Here is the setup:
>
> -K3 running @ 5W
> -Antenna: 66' doublet made from 28g wire fed with open feedline made from
> same, spaced apart with wood dowels 3" wide. It is placed up in a tree about
> 35' up with the ends coming down in an inverted v fashion.
> -The antenna is fed to a BL2 with a 12" piece of coax to the K3.
>
> I used a similar setup last summer with my K2 and had what I thought was
> pretty good success. In trying to evaluate this setup, I usually call CQ as
> opposed to answering one. This way I know that if I get a reply, the other
> op heard me. During the exchange I will state my power info to which I
> usually get positive comments about the K3 and/or the antenna setup - or
> they quickly sign off (not sure why they do that if I got a 599 report). 
>
> Yesterday, I was tuning around 40m when I heard a station calling CQ - QRP
> on 7.059. He was a 479 here so I thought I would give him a call back. He
> answered and gave me a report of 359. After the initial exchange, he stated
> he could not copy me - we tried a couple more times and then signed off. He
> was a definite solid copy on my end with the S-meter hitting S1-3 at times
> with some QSB. It was like this the whole time. 
>
> Now my questions: 
> 1 - with my antenna setup tuned with the KAT3, knowing that we were both at
> 5 watts, is it possible for the antenna to be more efficient at receiving
> than transmitting? I guess I always thought that if an antenna "system" is
> matched then the energy transfer is reciprocated for rcv and xmt. 
>
> 2 - with all the great receiver reports I've read on the K3 - could it be
> that I was simply hearing him better with my K3 than whatever he was using
> (unfortunately I don't know what he used as we never got that far in the
> QSO)?
>
> 3 - I did notice after the QSO that the balun was a little warm. If there
> are transmission losses in the balun, would there not be reciprocated losses
> on the receive side?
>
> If you feel this is not list appropriate, please reply to me privately. 
>   
>