[Elecraft] K144XV receive gain

Wed Nov 10 15:32:57 EST 2010

Hi Don,
thanks for discussion entry!

What is stated in IARU document is
"On the bands above 144 MHz this available power shall be -93 dBm"

I am afraid that "above 144" means above 144.000 let say 144.010 etc.

In one link you sent (thanks!) there is written:

"For the VHF / UHF bands, an ‘S9’ signal strength is a receiver input
power of ‘-93 dBm’. This is a level of ‘5mV’ in 50W at the receiver's
antenna input assuming the input impedance of the receiver is 50W."

No doubts (on my side) 144MHz band is VHF ;-)

My comment was mainly about what level correspond S9 on K3/K144XV now
and then what level should be as S9. And if this "gain" problem is
really lower gain or onky S-levels interpretation problem.
That´s it, hope somebody will report some real measured values.

73!
Lexa,  -dst-

2010/11/10 Don Nelson <n0ye at comcast.net>:
> 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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