[Elecraft] KPA1500 in the IARU Contest Last weekend

[john at kk9a.com]

That is quite an assumption.  A 2el 40m beam with large efficient  
High-Q loading coils will have less bandwidth than for example one of  
the popular US manufactured beams that use 68 turns of small wire in  
each coil.  The latter is more likely to have heating issues.  I have  
never noticed any SWR changes or amplifier re-tuning with my 40m  
OptiBeams during heavy use.

John KK9A


Jim Miller AB3CV wrote:

Since it is so narrow I suspect it may be a trapped design or have loading
coils which at 1500w may be heating and detuning as a result.

73

jim ab3cv

On Wed, Jul 15, 2020 at 11:45 AM Ray Spreadbury via Elecraft <
elecraft at mailman.qth.net> wrote:

>
>
> A correspondent asked me why I needed to tune a resonant antenna.
> The reason was because although the Yagi was tuned to resonate at about
> 7.130MHz it unfortunately has a rather narrow bandwidth. I needed to
> operate SSB in this contest in ITU Region 1 SSB, which is between 7.080MHz
> and 7.200MHZ. At 7.080MHz the SWR (with tuner bypassed) was 1.75:1 & at
> 7.200 was 1.95:1. I would be operating at power so I preferred to tune for
> 1.1:1.
> Yes I know the Yagi is not very good with that narrow bandwidth, but it is
> what it is. Normally I operate CW only on 40M & tune it to 7.030 with the
> bandwidth covering the preferred Region 1 CW portion of the band ie7.000 to
> 7.040 and the tuner is not needed.
> 73 Ray G3XLG