Posted by
Geoffrey Mackenzie-Kennedy-2 on
Nov 16, 2006; 11:13am
URL: http://elecraft.85.s1.nabble.com/KXB3080-Same-output-power-on-40m-as-20m-How-to-fix-tp395463p395466.html
Martin VA3SIE wrote:
> I placed a scanner across the room (with a 2m rubber duck antenna)
> from the KX1 driving a magnetic loop antenna tuned to 7040kHz and
> transmitted on 7040kHz. The scanner showed full scale deflection. I
> then tuned the scanner to the 1st harmonic 14080kHz and the scanner
> 'S' meter was maybe 4/5ths deflected.
>
> I know that isn't very scientific, it may be telling me the harmonic
> suppression isn't good or maybe it's not. I don't have anything
> sophisticated like a spectrum analyzer to do a proper analysis of the
> relative strength of the 1st harmonic versus the fundamental.
-------------------------------------------------------------------------
Martin,
Your magnetic loop antenna could be confusing your measurement using the
scanner because a magnetic loop exhibits narrow bandwidth, and in normal use
would act as a filter reducing the radiated level of the 20m harmonic.
Before I am flamed on this I know that there are many 'buts' and 'ifs' :-).
When using your scanner it would be better to drive the Tx into a dummy
load, and position the scanner plus rubber duck so that you get * no more*
than half scale deflection of its 'S' meter on 7040 kHz.to avoid any
possibility of overloading the scanner, then compare that reading with the
scanner's 'S' meter reading on 14080 kHz. It would be better to have the Tx
in its case when doing this to avoid any direct radiation from the PA etc
being picked up by the scanner. This measurement will give you a useful
indication but not a precise figure.
Sorry but I am unable to comment on the KXB3080 since I do not have one.
73,
Geoff
GM4ESD
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