[Elecraft] K2 S/N 4787 First QSO

[rrkrr]

The Sherwood Engineering data says that for the 2 kHz spacing dynamic 
range test, the K2's performance was limited not by nonlinearity 
(intermodulation distortion) but by the K2's oscillator phase noise 
sidebands.  The same table says the same thing about the Ten Tec Orion's 
performance in the 10 kHz spacing dynamic range test, and it is listed 
as the top performer in their table.  I think this data speaks more to 
the excellent wide dynamic range performance of these radios more than 
to the inferiority of their phase noise performance.

The Sherwood "Receiver Test Data Table" has a column labeled "LO Noise 
Spacing" and another column labeled "kHz" immediately to the right.  For 
the K2 data near the top of the spreadsheet, I interpret the entries in 
these columns as meaning that the single sideband phase noise power (in 
a 1 Hz bandwidth) for the K2's oscillator spectrum is -123 dB relative 
to the oscillator carrier power at 10 kHz away from the carrier 
frequency (someone please tell me if I'm wrong).  This is not too shabby 
considering the price of the K2. 

Cost is an important consideration.  Poseidon Scientific Instruments of 
Perth, Austrailia builds sapphire loaded cavity resonator microwave 
oscillators which are quite popular with high resolution, high dynamic 
range radar system designers.  These sport SSB phase noise performance 
of better than -145 dBc/Hz at only 1 kHz from the carrier at 10 GHz 
carrier frequency!  These can be used with regenerative frequency 
dividers to produce even more phenomenal performance at lower (read HF) 
frequencies, since the phase noise sideband spectrum extent also gets 
divided by the same ratio as the carrier frequency.  If you plan to get 
one to replace your K2's oscillator, you might wish to know that they 
cost more than $100k each.  You might also wish to know that if you 
actually want to measure the phase noise of one of these, you'll need 
another oscillator phse locked to the first one, with as good or better 
phase noise performance, not to mention a pretty fancy low frequency 
spectrum analyzer and a few other peripherals, which means you'll need 
to spend more than $200k.

Given that I'm only looking for weak CW signals on 40 Meters in the 
presence of QRM from another ham a mile away from me, and not trying to 
extract the doppler shifted radar pulse echo of a gnat at 200 miles 
range from that of the mountain behind him, I'll stick with my original 
K2 oscillator at about 0.5% of the cost.....

Bob
WB4TGG


G3VVT at aol.com wrote:

> 
>In a message dated 16/03/05 22:48:02 GMT Standard Time, g4bjm at hotmail.com  
>writes:
>
>The K2's  I've tested fall down on LO 
>phase noise performance.  Also note that  the K2 measurements on the Sherwood 
>web site state that the receiver  performance is limited by phase noise.  I 
>agree the RX works very  well, but I've attracted comments on the air (when 
>running QRO) re  transmitted phase noise.
>
>
>------------------------------------------------
> 
>I wonder if there is an obsession with numbers. To place the matter in  
>perspective, the Sherwood Engineering web site does list the K2 which  is serial 
>#3170 or about 2 years old? as being the 7th from the  top of all the ham radio 
>receivers tested. The aspect of the  effects of phase noise being only one of 
>many parameters that determine the  final result.
> 
>I would presume that to measure phase noise needs the resources of a well  
>equipped professional lab. Whilst personally I am well equipped to carry out  
>servicing of radios from HF through to UHF, cannot even really scratch the  
>surface in terms of measuring phase noise. The professional communications  
>systems servicing organisation I worked for despite being well equipped for  testing 
>from HF though to microwave in the field had little that could be used  
>seriously for testing phase noise except for probably some rather expensive HP  
>spectrum analysers that were issued only recently to maintain a new 8GHz digital  
>microwave system.
> 
>Before slagging the K2 one should take more seriously what it represents in  
>terms of outlay, costing only a fraction of cheapest HF transceivers available 
> on the market. Admittedly you have to build it yourself, but still the  
>performance of the K2 as what it was primarily designed for, a QRP CW  transceiver 
>takes a heck of a lot of beating. There are shortcoming that occur  with the 
>additional added components, though even these have been mitigated by  later 
>modifications.
> 
>Do the persons reporting phase noise on K2 TX really know what they are  
>talking about or just pushing out some mumbo jumbo that just happens to be the  
>popular quotation of the day? To be frank most hams including myself  would 
>probably not be be aware what phase noise is even if it jumped out and bit  them.
> 
>Bob, G3VVT
>K2 #4168
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