[Elecraft] Rob Sherwood's K3 test data -- quick summary

[AD6XY - Mike]

Did Rob comment on pops and transients generated in the AGC and DSP?

That was  the subject of his presentation at Dayton 2007, where he gave 
many examples to show that "New IF DSP designs [can] seriously 
exaggerate transient noise on weak signals... Some DSP radios make QRN 
much worse."
http://www.sherweng.com/documents/Dayton2007w.pdf

He also said, "I can’t wait to listen to the K3 to see if they got it 
right." And...?

...Ian will be very pleased should he have already ordered one...

This is excellent news, especially that -138 dB phase noise at 10kHz result.
I know Elecraft are mainly HF enthusiasts and concentrate on specifications
relevant to HF, like the dynamic range for signals 2kHz away. To me using
SSB at VHF and up this is fairly irrelevant. What I care about is the
dynamic range outside the roofing filter - say from 10kHz to 500kHz away
Assuming the radio is designed well this is mainly a function of the LO
phase noise. 

One problem with many radios, even the K2, is the performance far out from
the pass band. This is a real issue in contests at VHF in Europe where at a
good site there are often many very strong signals over 100dB above the
noise floor. Hopefully a transverter plus the K3 with its much better phase
noise results will be an improvement over the current VHF radios.

Typically at VHF the signal you want to work is at or below the noise floor,
perhaps -140 dBm and the other local contest groups are more like -30 dBm or
even worse if only a few miles away on the next hill. Mast head pre-amps
required to maintain a low noise figure don't help here.  Obviously you
don't operate too close in frequency to them, but a dynamic range of 120 dB
is desirable far out. I don't know of any receivers that manage this but 104
dB is pretty good and 10 dB better than the K2.

None of this helps of course if it is the transmitter that has the phase
noise, but if the K3 turns out really good in this respect, all the major
contest groups, the ones with the biggest signals, will start using K3s.


Mike
-- 
View this message in context: http://www.nabble.com/Rob-Sherwood%27s-K3-test-data----quick-summary-tp15392290p15402165.html
Sent from the Elecraft mailing list archive at Nabble.com.