[Elecraft] K144XV receive gain

Alan Bloom n1al at cds1.net
Wed Nov 10 12:09:07 EST 2010 

> To me 
> the IARU states that the -93 dBm is valid above the whole 2m band and 
> therefore does not include the 2m band.

I scratched my head over that one.  Then I looked again at the IARU's
wording and I think I see what you mean:

"3. On the bands above 144 MHz this available power shall be -93 dBm, "

If they had said "On the bands above the 144 MHz BAND ..." then I would
agree with you, but I think it's clear that they intended that 144-148
MHz be included in "the bands above 144 MHz".

The bigger question is what to do about the 50 MHz band.  The IARU
recommendation specifies:

"2. On the bands below 30 MHz a meter deviation of S-9 corresponds to an
available power of -73 dBm ..."

but does not say what to do between 30 and 144 MHz.  I have seen it
stated that most people assume it should be -93 dBm because 50 MHz is a
VHF band, but AFIK it's not official.

Alan


On Wed, 2010-11-10 at 09:34 -0700, Don Nelson wrote:
> Hi all,
> 
> I know this is a nit.
> 
> But the IARU state that the S9 signal level is -93 dBm for frequencies 
> above 144 MHz. I for one did not know that the -73 dBm was only valid 
> for lower bands until taking a look at the IARU recommendations. To me 
> the IARU states that the -93 dBm is valid above the whole 2m band and 
> therefore does not include the 2m band.
> 
> The IARU recommendation R.1 is found at web page 
> http://www.algonet.se/~k-jarl/ssa/IARU/smeter.html.
> 
> Another reference is at 
> http://webpages.charter.net/dig2bn/RF%20Comm-Elec%20Course%20Student%20Study%20Guides/S-Meter%20Calibration%20&%20IARU%20Standards.pdf 
> <http://webpages.charter.net/dig2bn/RF%20Comm-Elec%20Course%20Student%20Study%20Guides/S-Meter%20Calibration%20&%20IARU%20Standards.pdf>
> 
> Don, N0YE
> 
> 
> 
> 
> 
> 
> 
> On 11/10/2010 1:58 AM, Alexandr Kobranov wrote:
> > Keep in mind that on VHF and up S9 on S-meter is by definition as
> > -93dBm on input (5uV) - it is 20dB difference from HF bands.
> > I suppose it is respected for K3/P3 K144XV setup.
> > Are there some exact valus (MDS, NF, S9 level) for old and new
> > firmware versions? Maybe I missed them, let me know out of list in
> > such case...
> >
> > 73!
> >
> > Lexa, OK1DST
> > K3/100 #727
> >
> >
> >
> >
> > Dne 10.11.2010 4:55, N6JW napsal(a):
> >> I can certainly confirm this receive gain overcorrection problem on 2m.
> >>
> >> The "cpu sleep on rx" upgrade really helped cut back on the birdies.
> >> Thanks!
> >>
> >> But the overcorrection of the 2m gain compensation stands out like a sore
> >> thumb, particularly when one can actually see the relative amplitude of the
> >> signal on the P3.  Of course, this is "just a small matter of programming!"
> >> and I'm sure we will get it right in due course.
> >>
> >> Thanks&   73
> >>
> >> John, N6JW
> >>
> >>
> >>
> >> Jeff Cochrane - VK4BOF wrote:
> >>> Hi Terry,
> >>> Thanks very much for posting of those figures.
> >>> Although I do not have test gear that can back those numbers up I can say
> >>> that from my extensive on air testing that indeed, the 2M gain reduction
> >>> was overdone and to somewhere in the region your figures are showing.
> >>> The local (60+Km away) 2M FM repeater was normally S9+30db on earlier
> >>> firmware releases (around release 3.97 or so) on my K3 and once I got to
> >>> firmware revision 4.05 it had dropped to S9+5db, now that I am at revision
> >>> 4.14 it is now S5!
> >>> Nothing has changed at the repeater and all other radios tried with the
> >>> same antenna at my location show at least S9+20db signal strength. (And
> >>> usually full scale, it is an exceptional repeater, over 1500ft high and
> >>> with 50watts output to a 6+db gain antenna, it is almost full scale on my
> >>> handheld in the back yard here!)
> >>> Even allowing that the other radios have optomistic S meters I cannot
> >>> believe that they are all out by so much and by such a consistant amount.
> >>>
> >>> The overdoing of the 2m gain reduction has been the subject of a few
> >>> emails I have sent to Elecraft and to this reflector and to date I have
> >>> not heard an answer on the subject.
> >>>
> >>> Jeff Cochrane - VK4BOF
> >>> Innisfail, QLD, Australia
> >>> Elecraft K3# 4257
> >>>
> >>>     ----- Original Message -----
> >>>     From: w8zn at comcast.net
> >>>     To: elecraft at mailman.qth.net
> >>>     Sent: Wednesday, November 10, 2010 11:18 AM
> >>>     Subject: [Elecraft] K144XV receive gain
> >>>
> >>>
> >>>     After seeing several postings about the K144xv gain and experiencing
> >>> issues myself, I did some testing.
> >>>
> >>>     Comparing a K3/K144XV on 2m vs 6m.
> >>>
> >>>     On version 3.97 firmware, on 6m -87dbm yielded a S9 signal with the PR6
> >>> preamp in but the internal preamp off - best setting. On 2m, this yielded
> >>> a S9+5 signal with the internal preamp still off.
> >>>
> >>>     After loading 4.12 or higher, the same -87dbm gave the same S9 on 6m but
> >>> now only S5 on 2m and still only S7 with the internal preamp on. To
> >>> achieve the same S9 reading, I had to increase the signal level to -72dbm
> >>> with the internal preamp off. The release notes for 4.12 reference a gain
> >>> change on the K144xv and by the results of the 3.97 test I agree, there
> >>> was too much gain but instead of dropping 6 db or so, it appears that they
> >>> dropped 15db. Hopefully this will be rectified in the near future.
> >>>
> >>>     Terry Price - W8ZN  ex K8ISK
> >>>
> >>>
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