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N2CQ QRP Contest Calendar: July 19 - Aug 21, 2006

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Ken Newman-2

N2CQ QRP Contest Calendar: July 19 - Aug 21, 2006

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
N2CQ QRP CONTEST CALENDAR
July 19 - Aug 21, 2006
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Summer FOX Hunt - QRP 20M CW
UTC: Every Fri thru August 18, 0100z to 0229z
EDT: Every Thur thru August 17, 9 PM to 1029 PM
Info: http://www.qrpfoxhunt.org/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAQCC Straight Key/Bug Sprint *** QRP CONTEST! ***
EDT: Jul 19, 8:30 PM to 10:30 PM
UTC: Jul 20, 0030z to 0230z
Rules: http://www.arm-tek.net/~yoel/contests.html
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
VK/trans-Tasman Contests (160m CW) ... QRP Category
Jul 22, 0800z to 1400z
Rules: http://home.primus.com.au/vktasman/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Islands On The Air Contest (CW/SSB) ... QRP Category
Jul 29, 1200z to Jul 30, 1200z
Rules: http://www.contesting.co.uk/hfcc/calendar.shtml
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Flight of the Bumblebees (CW) ... QRP Contest!
Jul 30, 1700z to 2100z
Rules: http://www.arsqrp.com/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ten-Ten QSO Party (PH) ... QRP Category
Aug 5, 0001z to Aug 6, 2359z
Rules: http://www.ten-ten.org/calendar.html
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
TARA "Grid Dip" Contest (PSK/RTTY) ... QRP Category
Aug 5, 0000z to 2400z
Rules: http://www.n2ty.org/seasons/tara_seasons.html
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
EUROPEAN HF CHAMPIONSHIP (PH/CW) (EU work EU) Low Power Category
Aug 5, 1200z to 2359z
Rules: http://lea.hamradio.si/~scc/euhfcrules.htm
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ARRL UHF Contest ... Low Power Category
Aug 5, 1800z to Aug 6, 1800z
Rules: http://www.arrl.org/contests/calendar.html?year=2006
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
North American QSO Party (CW) ... 100W Max. (/QRP noted on entry)
Aug 5, 1800z to Aug 6, 0600z
Rules: http://www.ncjweb.com/naqprules.php
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Adventure Radio Spartan Sprint (CW) *** QRP CONTEST! ***
Aug 8, 0100z to 0300z (First Monday 9 PM EDT)
Rules: http://www.arsqrp.com/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAQCC Straight Key/Bug Sprint (CW) *** QRP Contest ***
EDT: Aug 8, 8:30 PM to 10:30 PM
UTC: Aug 9, 0030Z to 0230Z
Rules: http://www.arm-tek.net/~yoel/contests.html
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Worked All Europe DX Contest (CW) ... 100W category
Aug 12, 0000z to Aug 13, 2359z
Rules: http://www.darc.de/referate/dx/xedcwr.htm
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Maryland/DC QSO Party (SSB/CW) ... QRP Category
Aug 12, 1600z to Aug 13, 0400z
Aug 13, 1600z to Aug 13, 2359z
Rules: http://www.w3cwc.org
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SARTG WW RTTY Contest ... Low Power Category
Aug 19, 0000z to 0800z
Aug 19, 1600z to 2400z
Aug 20, 0800z to 1600z
Rules: http://www.sartg.com/contest/wwrules.htm
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
QRP ARCI Silent Key Memorial Contest (CW) *** QRP CONTEST! ***
Aug 19, 1500z to 1800z
Rules: http://www.qrparci.org
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
?BUBBA Summer QRP Sprint *** QRP CONTEST! ***
Aug 19, 1600z to 2200z
Rules: http://www.azscqrpions.org
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
North American QSO Party (SSB) ... 100W Max. (/QRP noted on entry)
Aug 19, 1800z to Aug 20, 0600z
Rules: http://www.ncjweb.com/naqprules.php
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NJ QSO Party (CW/SSB)
Aug 19, 2000z to Aug 20, 0700z
Aug 20, 1300z to Aug 21, 0200z
Rules: http://www.qsl.net/w2rj/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
RUN FOR THE BACON (CW) *** QRP CONTEST ***
EDT: Aug 20, 9 PM to 11 PM
UTC: Aug 21, 0100z 0300z
Rules: http://fpqrp.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thanks to SM3CER, WA7BNM, N0AX(ARRL) and others
for assistance in compiling this calendar.

Please foreward the contest info you sponsor to [hidden email] and
we will post it and give it more publicity.
Anyone may use this "N2CQ QRP Contest Calendar" for your website,
newsletter, e-mail list or other media as you choose.
(Include a credit to the source of this material of course.)
72 de
Ken Newman - N2CQ

http://www.amqrp.org/contesting/contesting.html
http://www.n3epa.org/Pages/Contest/contest.htm

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Don Ehrlich-2

K2/100 SSB ALC Problem

I almost never use SSB mode so have a lot still to discover about my K2 in
ssb mode.

I was on 40 meters ssb last night at 20 watts or so and found that the rig
kept rebooting. It was caused by an output that was actually well over 100
watts.

Later, connected to a dummy load and monitoring output with a scope across
the load I found that.

1 The rig always turns on with the metering set to RF mode ... just as
the manual says.

2 With the metering in RF mode the power is not controlled at all. No
matter where the power level is set (11 to 100 watts with the KPA100
engaged) the output peaks at over 100 watts. When I switch the bar display
to ALC the output is controlled as I would expect ... at whatever the power
has been set to.

3 CW mode is normal.

I had thought that ALC would be active and in control even when the metering
is set to display power instead of ALC level but that does not seem to be
the case.

I'm using an Icom IC-HM7 mobile mike (amplified). It seems to have about
the right amount of output because, at low power settings, the ALC display
shows a *lot* of ALC (all bars lit most of the time) but at 100 watts the
ALC display barely flickers which indicates that the mic barely has enough
output to drive the rig to 100 watts.

Don K7FJ

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Don Ehrlich-2

K2/100 SSB ALC Problem(Revised)

I just discovered that the behavior described below only occurs at turn-on.
Changing to ALC display causes results in normal control of power level as
described but if I then switch back to RF display then power control
*remains* normal. Only when I turn the rig off and back on again does the
power go out of control.

Don K7FJ
-------------------

>I almost never use SSB mode so have a lot still to discover about my K2 in
>ssb mode.
>
> I was on 40 meters ssb last night at 20 watts or so and found that the rig
> kept rebooting. It was caused by an output that was actually well over
> 100 watts.
>
> Later, connected to a dummy load and monitoring output with a scope across
> the load I found that.
>
> 1 The rig always turns on with the metering set to RF mode ... just as
> the manual says.
>
> 2 With the metering in RF mode the power is not controlled at all. No
> matter where the power level is set (11 to 100 watts with the KPA100
> engaged) the output peaks at over 100 watts. When I switch the bar
> display to ALC the output is controlled as I would expect ... at whatever
> the power has been set to.
>
> 3 CW mode is normal.
>
>
> I had thought that ALC would be active and in control even when the
> metering is set to display power instead of ALC level but that does not
> seem to be the case.
>
> I'm using an Icom IC-HM7 mobile mike (amplified). It seems to have about
> the right amount of output because, at low power settings, the ALC display
> shows a *lot* of ALC (all bars lit most of the time) but at 100 watts the
> ALC display barely flickers which indicates that the mic barely has enough
> output to drive the rig to 100 watts.
>
> Don K7FJ

Ken Wagner K3IU

RE: K2/100 SSB ALC Problem(Revised)

Very interesting. I also seldom use SSB, but I did a test on 5413 and see
the same thing. I have the K2/100 connected to a 50 ohm DL through a Diamond
SX-200 power meter. When I first turn the K2/100 "on" with the power control
set to 15-20 watts, mode LSB and "ahhhhhh" into the mic, I get 100 Watts PEP
out. If I then switch to ALC on the display, and do the same "ahhhhh", the
power is pulled down to the 15-20 watts output. Switching back to RF display
produces the same 15-20 watts PEP output. Turning power OFF and then ON
without changing the RF/ALC display results in full power out. I also note
that if the power control is turned up to 100 watts and then back down to 20
the ALD then brings the power down to 20 watts, or so, without having to
change to ALC display.

So I am seeing 2 things that "fix" the anomaly... 1)Switching to ALC display
and 2) Adjusting the power control

Wonder if there is anyone else out there who sees this ????

73, Ken K3IU

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don
Sent: Monday, July 31, 2006 12:30 PM
To: List Elecraft
Subject: [Elecraft] K2/100 SSB ALC Problem(Revised)

I just discovered that the behavior described below only occurs at turn-on.
Changing to ALC display causes results in normal control of power level as
described but if I then switch back to RF display then power control
*remains* normal. Only when I turn the rig off and back on again does the
power go out of control.

Don K7FJ
-------------------

>I almost never use SSB mode so have a lot still to discover about my K2
>in ssb mode.
>
> I was on 40 meters ssb last night at 20 watts or so and found that the
> rig kept rebooting. It was caused by an output that was actually well
> over 100 watts.
>
> Later, connected to a dummy load and monitoring output with a scope
> across the load I found that.
>
> 1 The rig always turns on with the metering set to RF mode ...
> just as the manual says.
>
> 2 With the metering in RF mode the power is not controlled at all.
> No matter where the power level is set (11 to 100 watts with the KPA100
> engaged) the output peaks at over 100 watts. When I switch the bar
> display to ALC the output is controlled as I would expect ... at
> whatever the power has been set to.
>
> 3 CW mode is normal.
>
>
> I had thought that ALC would be active and in control even when the
> metering is set to display power instead of ALC level but that does
> not seem to be the case.
>
> I'm using an Icom IC-HM7 mobile mike (amplified). It seems to have
> about the right amount of output because, at low power settings, the
> ALC display shows a *lot* of ALC (all bars lit most of the time) but
> at 100 watts the ALC display barely flickers which indicates that the
> mic barely has enough output to drive the rig to 100 watts.
>
> Don K7FJ

Tom Arntzen

Re: K2/100 SSB ALC Problem(Revised)

----- Original Message -----
From: "Ken K3IU" <[hidden email]>
To: "'Don'" <[hidden email]>; "'List Elecraft'"
<[hidden email]>
Sent: Monday, July 31, 2006 7:16 PM
Subject: RE: [Elecraft] K2/100 SSB ALC Problem(Revised)

> Very interesting. I also seldom use SSB, but I did a test on 5413 and see
> the same thing. I have the K2/100 connected to a 50 ohm DL through a
> Diamond
> SX-200 power meter. When I first turn the K2/100 "on" with the power
> control

Hi!
I did have the same problem on my K2/100 a while ago.
It occures on 40,80 and possible 160 also.
The problem is easy to fix with alcmod on the KSB2.
Email Gary at support for next step.
Meanwhile placing the rig in vox or alcreading will cause the rig to stick
to it's requested power.
You can still use PTT while in voxmode.
If by any means necessary Mail me off reflector and I can dig into my
archive for component changes.
But I don't know if there has been any changes to the mod since I did them
so I think there would be smart to check with Gary.

Good luck all

tom.arntzen(at)monet.no
LA1PHA

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Ron D'Eau Claire-2

RE: K2/100 SSB ALC Problem(Revised)

In reply to this post by Ken Wagner K3IU

Egad. Made the same test and it acts that way on 7 MHz for me too (as well
as 60 meters) on ol' S/N1289 with Rev 2.04/1.09 firmware. The other bands
seem okay.

I'm not a SSB operator either so I never noticed it.

Ron AC7AC

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Ken K3IU
Sent: Monday, July 31, 2006 10:17 AM
To: 'Don'; 'List Elecraft'
Subject: RE: [Elecraft] K2/100 SSB ALC Problem(Revised)

Very interesting. I also seldom use SSB, but I did a test on 5413 and see
the same thing. I have the K2/100 connected to a 50 ohm DL through a Diamond
SX-200 power meter. When I first turn the K2/100 "on" with the power control
set to 15-20 watts, mode LSB and "ahhhhhh" into the mic, I get 100 Watts PEP
out. If I then switch to ALC on the display, and do the same "ahhhhh", the
power is pulled down to the 15-20 watts output. Switching back to RF display
produces the same 15-20 watts PEP output. Turning power OFF and then ON
without changing the RF/ALC display results in full power out. I also note
that if the power control is turned up to 100 watts and then back down to 20
the ALD then brings the power down to 20 watts, or so, without having to
change to ALC display.

So I am seeing 2 things that "fix" the anomaly... 1)Switching to ALC display
and 2) Adjusting the power control

Wonder if there is anyone else out there who sees this ????

73, Ken K3IU

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don
Sent: Monday, July 31, 2006 12:30 PM
To: List Elecraft
Subject: [Elecraft] K2/100 SSB ALC Problem(Revised)

I just discovered that the behavior described below only occurs at turn-on.
Changing to ALC display causes results in normal control of power level as
described but if I then switch back to RF display then power control
*remains* normal. Only when I turn the rig off and back on again does the
power go out of control.

Don K7FJ
-------------------

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PE1E

Unique synthesizer LO ?

Maybe not the cleverest question of the year but I cannot resolve this one
myself and I'm eager to understand.

It is said that the synthesized LO of the K2 is of a unique design.
Though, when I compare the LO phase noise specs of the K2 and the AOR7030,
the latter seems to show much better specs.

What makes the K2 synthesizer so special ?
I'd appreciate any comment.

Peter, PE1E

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Don Wilhelm-3

RE: Unique synthesizer LO ?

Peter,

Let's see if I can help. I think of the PLL and VCO in two separate pieces.
The VCO and the PLL chip (U4) lock the VCO in 5 KHz steps. The PLL
reference oscillator provides the fundemantal clocking and frequency control
for the 5 KHz steps. The VFO range for each band is chosen by switching in
the proper capacitor shown in the schematic area labeled VFO Range
Selection, and frequency excursions (in the 5 kHz increments) is done by
controlling the voltage on the varactor diodes.

The frequency increments between these 5 kHz steps is done by 'pulling' the
PLL Reference Oscillator crystal, so the VCO output shifts in smaller than 5
kHz increments because of the change in the reference frequency while the
PLL synthesizer chip and the VCO loop are still locked onto the same
division ratio.

This may be a simplified viewpoint of the operation, but it has been
sufficient for my troubleshooting purposes - if the problem is gross
frequency errors, the source can be found in the VCO and synthesizer loop,
and small variations in frequency are usually found in the PLL Reference
oscillator.

Of course the control is all done from the microprocessor. It uses values
stored in the EEPROM during CAL PLL along with the frequency that the
operator dials in to apply the proper values to the DAC which in turn
produce a specific voltage that is to be applied to the varactors to create
the correct frequency output.

It works well and produces relatively low phase noise. Phase lock at 5 kHz
increments is easier to maintain than attempting to lock at a 10 Hz
increment. I believe the prime contributor to phase noise should be the PLL
reference oscillator phase noise, although there will be some noise
contribution from the VCO lock control. I have not analyzed the phase noise
aspects of the K2 in detail, so this is just speculation on my part, if
anyone else has done phase noise analysis, perhaps they will provide a more
definitive answer.

73,
Don W3FPR

> -----Original Message-----

> Maybe not the cleverest question of the year but I cannot resolve this one
> myself and I'm eager to understand.
>
> It is said that the synthesized LO of the K2 is of a unique design.
> Though, when I compare the LO phase noise specs of the K2 and the AOR7030,
> the latter seems to show much better specs.
>
> What makes the K2 synthesizer so special ?
> I'd appreciate any comment.
>
> Peter, PE1E
>

wayne burdick

Re: Unique synthesizer LO ?

Administrator

In reply to this post by PE1E

PE1E wrote:
>

> It is said that the synthesized LO of the K2 is of a unique design.
> Though, when I compare the LO phase noise specs of the K2 and the
> AOR7030,
> the latter seems to show much better specs.

Hi Peter,

Eric (WA6HHQ) and I designed the K2's synthesizer, so I'll try to
answer your questions.

When we designed the K2 synth we were faced with some difficult
criteria. Since the rig is a kit, we wanted to keep cost and complexity
low and avoid using surface-mount parts. And since it's targeted at
portable operation, we also needed to minimize current drain. But we
also needed a reasonably high-performance synthesizer to match the
possibilities of our down-conversion superhet receive architecture.

For all of the above reasons, we decided against using a DDS (direct
digital synthesizer). "High-performance" DDS chips generally are
expensive, have high current drain, and require a lot of support
circuitry. And lately just about all of them are fine-pitch SMDs. In
1998 when we first started prototyping synthesizers, the choices
considerably bleaker.

DDS chips have a bigger problem, which for a rig like the K2 was not
acceptable: close-in spurs that could compromise performance in high
QRM conditions. These spurs can be managed by adding a lot of
additional filtering and various techniques that are
component-intensive. For example, putting a PLL after the DDS will
help, but without great care, this can actually make things worse (the
PLL can multiply or fold back in spurs that occur way outside the DDS's
nominal output frequency). As is clearly shown in QST reviews of radios
that use DDS without a PLL (e.g., the SDR-1000), a simple low-pass
filter won't do the trick either. Numerous large spurs can be seen near
the carrier in phase noise plots of these radios. But a bare DDS is a
good choice for an "SDR," since it permits the very fast, very accurate
tuning needed for sophisticated digital modes.

I'm not familiar with the AOR7030's synth design. But if it uses a DDS,
it must either be managing the spurs as I mentioned above, or it has a
*lot* of spurs. You won't necessarily see then in the phase-noise plot;
doing the phase-noise sweeps with a typical bandwidth of 100 Hz won't
show any but the largest spurs (such as the loop spur shown in the
AOR7030's plot). But you'll hear them in the form of reciprocal mixing.

Back to the K2. Since we were avoiding DDS, we used a clean VCXO as the
PLL reference oscillator, tuning over a small range. To tune the
oscillator, we used a 12-bit DAC driving varactor diodes, and (as you
may recall) there's a calibration pass where we measure the VCXO and
store constants to tune it over its full range.

Again, I'm not familiar with the AOR design, but over the range we
typically measure (carrier + 2 kHz to 20 kHz), their "smoothed" phase
noise appears to be similar to the K2's. I don't know what bandwidth
they used for their phase-noise plots, so it's hard to say whether
they're mitigating DDS spurs or not. As I mentioned, they can be hidden
by the analyzer's bandwidth. (Note that the upper curve of the two
shown for the AOR7030 is the one I'm referring to. They provided an
additional "far out" curve below it, and we don't have a plot of this
type available for the K2.)

The other piece of the puzzle was the VCO. Somehow, using a minimum of
parts, we had to make the VCO cover 9 or 10 bands. The resulting
circuit, with three latching relays to switch fixed capacitors and
varactors, and only one VCO inductor, did the trick.

73,
Wayne
N6KR

---

http://www.elecraft.com

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wayne burdick

Re: Unique synthesizer LO ? [additional data]

Administrator

In reply to this post by PE1E

Peter,

I took a closer look at the AOR 7030 phase noise plot. Out to 5 kHz or
so the K2 is noticeably better (11 dB better at 2 kHz). Farther out the
7030 has the advantage. But remember that the 7030 measurements were
made in receive mode, whereas the K2's were made in transmit mode,
where all sources contribute to raise the noise floor. Hence the term
"composite" used by QST in their product reviews.

2kHz 4 6
K2 -115 -125 -128
7030 -104 -120 -128

73,
Wayne
N6KR

PE1E wrote:

> It is said that the synthesized LO of the K2 is of a unique design.
> Though, when I compare the LO phase noise specs of the K2 and the
> AOR7030,
> the latter seems to show much better specs.

---

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PE1E

Re: Unique synthesizer LO ?

In reply to this post by wayne burdick

Wayne,

Thanks for your dedicated response to my phase noise question.
I understand now why and how K2's LO design differs from the usual.

Indeed, I noticed that at less than 5 KHz/dbc your VCXO+DAC>varicaps
approach show less oscillator noise than the famous AOR7030 design (
the7030Plus should be even bit better ).
However, after 15 KHz/dBc the AOR 7030 graph claims a 10 dB better phase
noise.
Though, I see on the 7030's graphs the DDS spurs where you are talking about
( and as you suggest, more spurs may remain unseen ).
Besides, I presume the more the sweep goes to the right the less reciprocal
mixing will occur / harm.

I may frankly confess that I am gladly surprised by your extensive an
dedicated effort you make for me to explain things.
If this an omen of Elecraft's customer service, I may have taken the right
decision to buy a K2.

I was so fortunate to buy today a high S/N completely built/aligned/tested
K2 ( ssb+nb+160Rx ) from a nice US person.
He built many K2's before and sold them.

Since I want more options I just ordered with you the DSP, the internal ATU,
the RS232 i'face and the internal battery options.
This nice OM will built all of these options for me.
So, shortly I will own a K2+ which will enrichten my life :-)

Thanks again,
Peter PE1E
Amsterdam.

----- Original Message -----
From: "wayne burdick" <[hidden email]>
To: "PE1E" <[hidden email]>
Cc: "'List Elecraft'" <[hidden email]>
Sent: Tuesday, August 01, 2006 6:11 AM
Subject: Re: Unique synthesizer LO ?

> PE1E wrote:
> >
>
> > It is said that the synthesized LO of the K2 is of a unique design.
> > Though, when I compare the LO phase noise specs of the K2 and the
> > AOR7030,
> > the latter seems to show much better specs.
>
> Hi Peter,
>
> Eric (WA6HHQ) and I designed the K2's synthesizer, so I'll try to
> answer your questions.
>
> When we designed the K2 synth we were faced with some difficult
> criteria. Since the rig is a kit, we wanted to keep cost and complexity
> low and avoid using surface-mount parts. And since it's targeted at
> portable operation, we also needed to minimize current drain. But we
> also needed a reasonably high-performance synthesizer to match the
> possibilities of our down-conversion superhet receive architecture.
>
> For all of the above reasons, we decided against using a DDS (direct
> digital synthesizer). "High-performance" DDS chips generally are
> expensive, have high current drain, and require a lot of support
> circuitry. And lately just about all of them are fine-pitch SMDs. In
> 1998 when we first started prototyping synthesizers, the choices
> considerably bleaker.
>
> DDS chips have a bigger problem, which for a rig like the K2 was not
> acceptable: close-in spurs that could compromise performance in high
> QRM conditions. These spurs can be managed by adding a lot of
> additional filtering and various techniques that are
> component-intensive. For example, putting a PLL after the DDS will
> help, but without great care, this can actually make things worse (the
> PLL can multiply or fold back in spurs that occur way outside the DDS's
> nominal output frequency). As is clearly shown in QST reviews of radios
> that use DDS without a PLL (e.g., the SDR-1000), a simple low-pass
> filter won't do the trick either. Numerous large spurs can be seen near
> the carrier in phase noise plots of these radios. But a bare DDS is a
> good choice for an "SDR," since it permits the very fast, very accurate
> tuning needed for sophisticated digital modes.
>
> I'm not familiar with the AOR7030's synth design. But if it uses a DDS,
> it must either be managing the spurs as I mentioned above, or it has a
> *lot* of spurs. You won't necessarily see then in the phase-noise plot;
> doing the phase-noise sweeps with a typical bandwidth of 100 Hz won't
> show any but the largest spurs (such as the loop spur shown in the
> AOR7030's plot). But you'll hear them in the form of reciprocal mixing.
>
> Back to the K2. Since we were avoiding DDS, we used a clean VCXO as the
> PLL reference oscillator, tuning over a small range. To tune the
> oscillator, we used a 12-bit DAC driving varactor diodes, and (as you
> may recall) there's a calibration pass where we measure the VCXO and
> store constants to tune it over its full range.
>
> Again, I'm not familiar with the AOR design, but over the range we
> typically measure (carrier + 2 kHz to 20 kHz), their "smoothed" phase
> noise appears to be similar to the K2's. I don't know what bandwidth
> they used for their phase-noise plots, so it's hard to say whether
> they're mitigating DDS spurs or not. As I mentioned, they can be hidden
> by the analyzer's bandwidth. (Note that the upper curve of the two
> shown for the AOR7030 is the one I'm referring to. They provided an
> additional "far out" curve below it, and we don't have a plot of this
> type available for the K2.)
>
> The other piece of the puzzle was the VCO. Somehow, using a minimum of
> parts, we had to make the VCO cover 9 or 10 bands. The resulting
> circuit, with three latching relays to switch fixed capacitors and
> varactors, and only one VCO inductor, did the trick.
>
> 73,
> Wayne
> N6KR
>
> ---
>
> http://www.elecraft.com
>
>

wayne burdick

Re: Unique synthesizer LO ?

Administrator

Hi Peter,

Thanks for your kind comments, and I hope you enjoy your new K2.

> Indeed, I noticed that at less than 5 KHz/dbc your VCXO+DAC>varicaps
> approach show less oscillator noise than the famous AOR7030 design (
> the7030Plus should be even bit better ).
> However, after 15 KHz/dBc the AOR 7030 graph claims a 10 dB better
> phase
> noise.

This is because the AOR data was taken in receive mode. The K2 phase
noise data is from a transmit composite noise test. In transmit mode
the noise floor is affected by a number of other factors, and the noise
is generally worse than on receive.

73,
Wayne
N6KR

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John, KI6WX

Re: Unique synthesizer LO ?

In reply to this post by PE1E

Peter;
I have posted on the web a detailed set of measurements of the K2 phase
noise, both in receive and transmit. The measurements cover a frequency
range of 20 Hz to 45 kHz. These measurements can be viewed at:

http://home.pacbell.net/johngreb/k2phasenoise.pdf

The ARRL composite transmit noise measurements that were published in QST
are in errror and show less noise than reality. The transmit phase noise
measurements in the above document are the correct phase noise measurements,
but they do not include any amplitude noise that might be on the transmit
carrier.

The K2 oscillator phase noise is good for a simple low-current synthesizer,
but there are ways to make it better. I note some of those in the above
document. A re-designed K2 RF board could drop the phase noise by at least
10 dB, which would improve the 5 kHz two-tone third-order dynamic range 6
dB.
-John
KI6WX

wayne burdick

Re: Unique synthesizer LO ?

Administrator

John, KI6WX wrote:

>
> The ARRL composite transmit noise measurements that were published in
> QST are in error....

And not just for the K2. It turns out that all transmitter phase noise
plots published in QST going back for many years include a 7.5 dB error
in favor of the rigs. The lab has identified this error and corrected
it, so going forward we'll see more accurate numbers.

Much of the error is traceable to a decades-old HP application note
that, apparently, had been taken for gospel.

73,
Wayne
N6KR

> ---

http://www.elecraft.com

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Jack Smith-6

Re: Unique synthesizer LO ?

In reply to this post by John, KI6WX

Nice work. Could you discuss the test setup you used?

I've been contemplating making some phase noise measurements, using the
approach the ARRL used some years ago, HP8640B as the LO, a DBM, low
noise amplifier, etc. so it was useful to see the 8640B data as well.

Jack K8ZOA

John, KI6WX wrote:

> Peter;
> I have posted on the web a detailed set of measurements of the K2
> phase noise, both in receive and transmit. The measurements cover a
> frequency range of 20 Hz to 45 kHz. These measurements can be viewed at:
>
> http://home.pacbell.net/johngreb/k2phasenoise.pdf
>
> The ARRL composite transmit noise measurements that were published in
> QST are in errror and show less noise than reality. The transmit
> phase noise measurements in the above document are the correct phase
> noise measurements, but they do not include any amplitude noise that
> might be on the transmit carrier.
>
> The K2 oscillator phase noise is good for a simple low-current
> synthesizer, but there are ways to make it better. I note some of
> those in the above document. A re-designed K2 RF board could drop the
> phase noise by at least 10 dB, which would improve the 5 kHz two-tone
> third-order dynamic range 6 dB.
> -John
> KI6WX
>
>
>> Maybe not the cleverest question of the year but I cannot resolve
>> this one
>> myself and I'm eager to understand.
>>
>> It is said that the synthesized LO of the K2 is of a unique design.
>> Though, when I compare the LO phase noise specs of the K2 and the
>> AOR7030,
>> the latter seems to show much better specs.
>>
>> What makes the K2 synthesizer so special ?
>> I'd appreciate any comment.
>>
>> Peter, PE1E
>
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>
>

John, KI6WX

Re: Unique synthesizer LO ?

In reply to this post by John, KI6WX

Two additions to my recent posting based on several replies.

The ARRL composite transmit noise test measurements have been 7.5 dB lower
than reality for many years. This is true for all radios, not just the K2.

My comment about improving the phase noise only applies if the RF board is
re-designed. I don't think it is possible to significantly reduce the phase
noise with a mod on the current board.
-John
KI6WX

> Peter;
> I have posted on the web a detailed set of measurements of the K2 phase
> noise, both in receive and transmit. The measurements cover a frequency
> range of 20 Hz to 45 kHz. These measurements can be viewed at:
>
> http://home.pacbell.net/johngreb/k2phasenoise.pdf
>
> The ARRL composite transmit noise measurements that were published in QST
> are in errror and show less noise than reality. The transmit phase noise
> measurements in the above document are the correct phase noise
> measurements, but they do not include any amplitude noise that might be on
> the transmit carrier.
>
> The K2 oscillator phase noise is good for a simple low-current
> synthesizer, but there are ways to make it better. I note some of those
> in the above document. A re-designed K2 RF board could drop the phase
> noise by at least 10 dB, which would improve the 5 kHz two-tone
> third-order dynamic range 6 dB.
> -John
> KI6WX
>
>
>> Maybe not the cleverest question of the year but I cannot resolve this
>> one
>> myself and I'm eager to understand.
>>
>> It is said that the synthesized LO of the K2 is of a unique design.
>> Though, when I compare the LO phase noise specs of the K2 and the
>> AOR7030,
>> the latter seems to show much better specs.
>>
>> What makes the K2 synthesizer so special ?
>> I'd appreciate any comment.
>>
>> Peter, PE1E
>
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