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Re: KXB30 sensitivity better than KXB3080?

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Martin (VA3SIE)

Re: KXB30 sensitivity better than KXB3080?

Hi, Don.

Well I finally did get around to checking out the KX1 with a signal generator.

Here are the signal levels at which I can barely distinguish a signal:

80m -126dBm
40m -130dBm
30m -107dBm
20m -120dBm

So, 30m does appear to have a problem.

I'll have to try re-tweaking the 30m trimmers, but it's interesting
that 80m has much better sensitivity than 30m. The KXB3080 manual
indicates that peaking the 30m trimmers affects 80m as well, so you'd
think that if 30m was poor 80m ought to be poor as well.

The KXB3080 manual indicates that on 30m, C3 and C4 come into play.
I'm unclear if on 80m C1 and C4 remain in play, or if they are
replaced by C2 and C5 (ie. are there any trimmer capacitors in play on
80m?) If both trimmers are out of play on 80m that would certainly
indicate that I simply need to find a non-metallic screw-driver and
peak the caps. If however the trimmers remain in play on 80m, and my
80m performance is pretty good, then perhaps either or both trimmer
caps are defective.

Anyway, next step is re-tweaking those caps!

Thanks,
Martin.
VA3SIE.

> Martin,
>
> I would be hesitant to make comparisons based on signals on the air.
> The signal propagation can make a big difference.
>
> If you have a signal generator that will produce a measurable (and
> repeatable output, that can be used for a valid comparison.
>
> Normally, the 30 meter signals are as good or better with the 3080
> option as they were with the 30 meter option. You may have a problem,
> but first try adjusting the 30 meter trimmers. For accuracy in
> adjustment, they must be adjusted with an insulated screwdriver blade -
> even a metallic screwdriver wrapped with tape will cause some de-tuning
> during adjustment and you must find the proper tuning point by trial and
> error.
>
> 73,
> Don W3FPR
>
> Martin (VA3SIE) wrote:
> > Hi,
> >
> > I wonder if anyone else has an observation about the sensitivity of
> > the KX1 on 30m with the original 30m board compared to the 30 & 80m
> > board? I've noticed that signals are not as strong on 30m now with
> > the new board. For example, the RTTY station on 10100kHz is at best a
> > 4x5 whereas it used to be 5x9. I can only hear the strongest CW
> > stations.
> >
> > 20m & 40m are as good as before.
> >
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Don Wilhelm-4

Re: KXB30 sensitivity better than KXB3080?

Martin,

Yes, peak the trimmers on 30 meters - use a fully insulated tool (like a
ceramic or hard plastic screwdriver) for the most precise tuning. If
there is anything metallic on the screwdriver, your hand capacity will
have an effect while tuning. If you only have a metallic tool, wrap the
shaft with tape and tune a little at a time and try with each trial
until it seems to be at the optimum setting.

The 30 meter trimmers are not in the active part of the circuit on 80.
The 80 meter receiver front end tuning is broad and the capacitors that
tune it down to 80 are fixed 300 pf caps.

73,
Don W3FPR

Martin (VA3SIE) wrote:

> Hi, Don.
>
> Well I finally did get around to checking out the KX1 with a signal generator.
>
> Here are the signal levels at which I can barely distinguish a signal:
>
> 80m -126dBm
> 40m -130dBm
> 30m -107dBm
> 20m -120dBm
>
> So, 30m does appear to have a problem.
>
> I'll have to try re-tweaking the 30m trimmers, but it's interesting
> that 80m has much better sensitivity than 30m. The KXB3080 manual
> indicates that peaking the 30m trimmers affects 80m as well, so you'd
> think that if 30m was poor 80m ought to be poor as well.
>
> The KXB3080 manual indicates that on 30m, C3 and C4 come into play.
> I'm unclear if on 80m C1 and C4 remain in play, or if they are
> replaced by C2 and C5 (ie. are there any trimmer capacitors in play on
> 80m?) If both trimmers are out of play on 80m that would certainly
> indicate that I simply need to find a non-metallic screw-driver and
> peak the caps. If however the trimmers remain in play on 80m, and my
> 80m performance is pretty good, then perhaps either or both trimmer
> caps are defective.
>
> Anyway, next step is re-tweaking those caps!
>
> Thanks,
> Martin.
> VA3SIE.
>
>