Rob Sherwood's K3 test data -- quick summary

[wayne burdick]

Rob Sherwood, NC0B, an independent and well-known receiver performance
specialist, has completed his K3 receiver tests. We're pleased with the
results, which will place the K3 at the top of his comparison chart.

Rob will be updating his web site in a few days. For now, I'll just
mention a couple of his numbers (with his permission).

Elecraft K3, S/N 00149, 20 meters, preamp off:       

   Dynamic Range 20 kHz          104 dB
   Dynamic Range 5 kHz           102 
   Dynamic Range 2 kHz           101*

* with 200 Hz 5-pole filter

   Blocking above noise floor at 100 kHz spacing, AGC On:  140 dB
   Phase noise (normalized) at 10 kHz spacing:  138 dBc/Hz

Rob performs some tests differently that we (and the ARRL) do, but in
general we're all in close agreement. Note that the unit under test had
only Elecraft 5-pole filters. Our tests show the 8-pole filters to be
as good or better, and we sent some of them to Rob to test when he gets
a chance.

73,
Wayne
N6KR


---

http://www.elecraft.com

       
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[gm3sek]

Wayne Burdick wrote:

>Rob Sherwood, NC0B, an independent and well-known receiver performance
>specialist, has completed his K3 receiver tests. We're pleased with the
>results, which will place the K3 at the top of his comparison chart.
>
>Rob will be updating his web site in a few days. For now, I'll just
>mention a couple of his numbers (with his permission).
>
>Elecraft K3, S/N 00149, 20 meters, preamp off:       
>
>  Dynamic Range 20 kHz          104 dB
>  Dynamic Range 5 kHz           102 
>  Dynamic Range 2 kHz           101*
>
>* with 200 Hz 5-pole filter
>
>  Blocking above noise floor at 100 kHz spacing, AGC On:  140 dB
>  Phase noise (normalized) at 10 kHz spacing:  138 dBc/Hz
>
>Rob performs some tests differently that we (and the ARRL) do, but in
>general we're all in close agreement. Note that the unit under test had
>only Elecraft 5-pole filters. Our tests show the 8-pole filters to be
>as good or better, and we sent some of them to Rob to test when he gets
>a chance.

Very good!

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...?


--

73 from Ian GM3SEK
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Buck - k4ia]

In a message dated 2/10/2008 3:17:39 A.M.  Eastern Standard Time,
[hidden email] writes:
New IF DSP designs [can]  seriously
exaggerate transient noise on weak signals... Some DSP radios make  QRN
much worse."

I certainly felt that way when listening on the  Orion.  The AGC was never
right.  Users tried adjusting the Hang,  Slope, Delay and Threshold to no avail.
 The radio always sounded  noisy.  

Unless my ears deceive me, I think the K3 is much  better.  Will have to wait
for the empirical data because I don't have an  analog radio to compare.

k4ia
"Buck" K3 #101
Fredericksburg, VA  




**************Biggest Grammy Award surprises of all time on AOL Music.    
(http://music.aol.com/grammys/pictures/never-won-a-grammy?NCID=aolcmp003000000025
48)
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Barry N1EU]

FWIW, my initial listening isn't hearing much difference between the Orion and K3 on transient response.  So far, static bursts are sounding pronounced on both radios to my ears.  

73,
Barry N1EU

K4IA wrote

In a message dated 2/10/2008 3:17:39 A.M.  Eastern Standard Time,
[e-mail] writes:
New IF DSP designs [can]  seriously
exaggerate transient noise on weak signals... Some DSP radios make  QRN
much worse."

I certainly felt that way when listening on the  Orion.  The AGC was never
right.  Users tried adjusting the Hang,  Slope, Delay and Threshold to no avail.
 The radio always sounded  noisy.  

Unless my ears deceive me, I think the K3 is much  better.  Will have to wait
for the empirical data because I don't have an  analog radio to compare.

[Ken, KA0W]

Yes, the Orion (II) is a "little" unpleasant to listen to unless one perhaps adjusts RF gain down.  I enjoyed the excellent filtering on the Orion II when comparing the modified FT-1000D and Pro III, but the Orion II felt "unfinished" for the year and a half I had it. Yes, can maybe blame the agc, but that is not an acceptable excuse for noise. There is a lot more to a radio than excellent filtering. One has to listen to it too.
   
  Ken, KA0W
   
   
   
 

[hidden email] wrote:
  In a message dated 2/10/2008 3:17:39 A.M. Eastern Standard Time,
[hidden email] writes:
New IF DSP designs [can] seriously
exaggerate transient noise on weak signals... Some DSP radios make QRN
much worse."

I certainly felt that way when listening on the Orion. The AGC was never
right. Users tried adjusting the Hang, Slope, Delay and Threshold to no avail.
The radio always sounded noisy.

Unless my ears deceive me, I think the K3 is much better. Will have to wait
for the empirical data because I don't have an analog radio to compare.

k4ia
"Buck" K3 #101
Fredericksburg, VA




**************Biggest Grammy Award surprises of all time on AOL Music.
(http://music.aol.com/grammys/pictures/never-won-a-grammy?NCID=aolcmp003000000025
48)
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft 

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[wayne burdick]

Rob Sherwood wrote:

> Subject:  SSB passband.
> When one uses the PBT function, does the DSP work in such a way as to
> keep the filtering centered in the roofing filter window, or do you
> start to run up against the edge of the roofing filter?

In SSB modes, the DSP passband is always "virtually" centered in the
roofing filter. That is, if you SHIFT the DSP passband in either
direction, the center of the roofing filter and DSP IF are kept
aligned. (In CW mode it's more complicated; we had to choose between
putting the DSP passband in the center of the roofing filter, or
sliding down until it hits the lower edge of the roofing filter. We
chose the latter, with intent to maximize opposite sideband rejection.)

When shifting the DSP passband downward, you reach a point where the
following criteria is no longer met:

      DSP center >= crystal filter bandwidth / 2 + margin

In this case, the low edge of the requested DSP passband would pass
through F = zero (at AF). Since this makes no sense functionally, we
start truncating the DSP's IF and AF passbands on the low end. But
because we're still shifting the crystal filter and DSP passbands
downward, the desired goal -- removing high-pitched QRM -- is achieved.

In the above equation, "margin" is at present 0.2 kHz. It could be made
user-programmable by mode, and this is on the firmware list. For SSB,
you might prefer to have the margin be zero; this would in effect shift
the default passband 200 Hz lower. (Everything, including this, is a
Small Matter of Programming; but we have to carefully re-test the
effect of any changes, so they won't happen overnight.)

73,
Wayne
N6KR

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[AD6XY]

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

[David Cutter]

It's not just vhf contesters who have a problem, we also have 59+60 to 66dB
signals from broadcast stations on 40m (and don't forget those nasty
sidebands)
-10 to -5dBm is not unusual from a high dipole.

David
G3UNA


snip from AD6XY:

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
--  

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Darwin, Keith]

Actually, Wayne, you have it upside down.  The K3 topping Rod's chart
simply validates his testing methods.

:-)

- Keith N1AS -
- K2 5411.ssb.100 -
- K3 Wave 3 -

-----Original Message-----
From: wayne burdick

Rob Sherwood, NC0B, an independent and well-known receiver performance
specialist, has completed his K3 receiver tests. We're pleased with the
results, which will place the K3 at the top of his comparison chart.
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com