Login  Register

Re: Fw: K3/K144XV/P3 Signal Strength Readings

Posted by Alan Bloom-2 on Jan 24, 2011; 3:26am
URL: http://elecraft.85.s1.nabble.com/Fw-K3-K144XV-P3-Signal-Strength-Readings-tp5937006p5954098.html

I realize that IARU Region 1 recommendations officially apply only to
Region 1 (Europe, Africa, Middle East, N. Asia) but since I don't know
of any other official recommendation that's the one I used for the P3.

I was not privy to the IARU committee's deliberations, so I don't know
why they recommended S9 = -73 dBm on HF and S9 = -93 dBm on VHF and
above, but I can speculate. One reason may be the fact that antenna
noise levels (and signal levels for that matter) are generally much
lover above 144 MHz than below 30 MHz so it makes sense to adjust the
S-unit scale downward.

Another reason may be that most VHF/UHF transverters have gain and 20 dB
is probably a representative value. So the S meter on the HF transceiver
typically will read about 20 dB higher when the transverter is being
used.

My understanding is that is exactly how the K3 works now.  However,
since the gain of the K144XV is actually around 25 dB, that results in
S9 = -98 dBm rather than -93 dBm.  I believe it is on Wayne's list to
correct that in K3 firmware.

Alan N1AL




On Sun, 2011-01-23 at 02:51 +0000, VR2BrettGraham wrote:

> G3UCK now at least has ex-VR2BG to talk to:
>
> > Very interesting, Brett, and thank you for your comments and the
> > research you have done. I *was* beginning to feel a little isolated by
> > lack of comment from anyone hihi! Although I did receive one reply
> > offlist reporting experience similiar to mine.
>
> The Brand-E community is rather USA-centric, in case you have not
> noticed ;^).  You bring up something that falls in the
> something-is-other-than-fantastic category & that is not conducive to
> cheerleading or provides an opportunity to express economic patriotism,
> hence you were ignored.  Hence your posts, my post & nothing else but
> somebody saying "Yeah, I noticed the same thing" to you directly.  Is a
> bit of a shame, because it gets in the way of sorting out a product that
> has things that need sorting out.
>
> > I was not aware of the 1990 Torremolinos recommendation as such but a
> > recent thread here on the reflector
> > http://mailman.qth.net/pipermail/elecraft/2011-January/143651.html 
> > noted the ambiguity about 6m and Alan Bloom of Elecraft concluded that
> > it was generally accepted that it should be treated as in the -93dbm
> > category like 2m. However, you are correct to point out that it is a
> > Region 1 (ie EU) recommendation and I have not been able find out
> > whether or not there are similar or different recommendations for
> > Regions 2 and 3.
> >
> > Compared with my FT847 (another rig that straddles the -73/-93dbm
> > boundary) the S meter on the K144XV/K3 reads low on 2m and there have
> > been a number of postings on the reflector from at least two of the
> > IARU regions, if not all three, by people who feel that at present it
> > reads low compared with what they are used to on other rigs. This
> > suggests to me that other commercial rigs for 2m do use the -93dbm
> > standard - as the P3 now does. Unfortunately I do not have any test
> > gear that will produce a known 50 microvolts or 5 microvolts on 2m to
> > do some checking. I accept that this doesn't seem to accord with your
> > findings on your rig, Brett, if I properly understand them. As general
> > comment, though, the rig doesn't seem to show enough difference in db
> > between S1 and S9 on the bands you mention.
>
> It was the FT-847 that I was describing - one product from one
> manufacturer with Brand-Y's rather peculiar approach to R&D is obviously
> not the best way to judge overall state-of-play of the industry, but it
> is a start & I believe a more thorough look at how products are set up &
> how they actually perform will find not many following this
> Recommendation (do the likes of the really good, long established &
> respected transverter manufacturers really add 20 dB gain to the output
> of their products in order to comply?).
>
> S-meters are of course S-meters, we both I suspect are long enough in
> the tooth to understand their limitations, but a 20 dB delta is not
> insignificant & I really do wonder about this Recommendation that is so
> old, may not be followed & we cannot now see for ourselves why it is we
> were told things should be this way.
>
> It merits looking at further, especially if as I suspect (though my
> experience is only from IARU R3 & what they get up to in their
> conferences), there was zero involvement of anyone other than national
> societies in drafting it.   To anyone with a relevant professional
> background, this point alone is a bit of a show-stopper.
>
> 73, ex-VR2BG/p.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html


______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html