Re: [Elecraft] [K2] Spurious emission in SSB

[Steve Kavanagh via Elecraft]

Chris 

Is the frequency separation exactly 900 kHz?  If a bit more, perhaps the 
oscillator in the KSB2 MCU (U1/Z1) at (nominally) 4 MHz is coupling into the IF 
(nominally 4.915 MHz) path on the same board, on the output side of the crystal 
filter).  Problems with grounding, bypass capacitors and long leads might do 
this.  I have a vague recollection that the instructions for early KSB2 board 
assembly did not involve grounding the filter crystal cases and later 
instructions did.  That shouldn't directly affect that coupling but it might 
generally help provide a generally more solid ground.

There are other 4 MHz oscillators in the K2 that might couple in, too, but 
since the problem only exists on SSB, it seems this one would be a more likely 
culprit.

Could re-aligning the 10 metre bandpass filter (K2 RF Board) help?

Generic ITU Radio Regulations require -43 dB dBc or better spurious levels at 1 
watt output, so one hopes it could meet that. Of course if you are running a 
couple of hundred watts for 23 cm EME, you are required to do better!  Of 
course, you could get 3 dB better signal-to-spurious level just by going up to 
2 watts.

I use a K2 (with an internally mounted 2 m transverter) in my 10 GHz setupI 
suppose I ought to check for that issue, if I can borrow a spectrum analyzer.  
But then...who would actually hear me, or have a problem with, a mW level 
signal at 10.3672 GHz and a beamwidth of 3 degrees?

73,
Steve VE3SMA
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[Elecraft] Any problems with this 6m setup with KPA500?

[Steve Kavanagh via Elecraft]

A few of us are planning an multi-operator operation for next weekend's CQ WW 
VHF contest, cobbling together equipment from different places.  I am wondering 
if there are any potential issues (most likely with switching timing) with the 
following potential setup for six metres:

Radio: K2 (QRP+KXV60, with ground-on-transmit T/R keying output), 8R hold ON, 
with some reasonable release time for semi-break-in CW) 

Transverter: homebrew, 10 watts out max., relay switched, but the relay is 
faster than the K2, so no sequencer needed normally

Intermediate amplifier: an ancient Lunar 6M10-120P, which is an RF-sensed only 
(no T/R input available) 100-watt class amp, with K2 drive set to give around 
30 watts output.  Up to this point the setup has been tested and works fine.

Final amplifier: KPA500

I'd plan on adding a second T/R output from the K2 somehow, so the transverter 
and KPA500 can be keyed at the same time.

Modes of operation: CW, SSB, FT8, FT4?, MSK144.

I haven't quite got my head around what would happen on non-CW modes where the 
release delay for the T/R output is zero.  In this case the transverter and 
KPA500 will switch from transmit to receive before the intermediate amplifier 
does (using its own internal delay timing).  Is that likely to cause any 
issues?  Any other timing problems you can think of?  Do I need a sequencer?

Would the KPA500 survive 100 watts input if, for some reason, the drive level 
is set too high by mistake?  My understanding is that it should initially 
switch in an attenuator and then hard-fault (switch to straight-through 
operation).  Correct?

73,
Steve VE3SMA
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[Elecraft] [K2] Erratic tuning solved, I think

[Steve Kavanagh via Elecraft]

I took the front panel and control boards off the RF board and reassembled 
themthe intermittent lack of response to tuning knob returned after a 
couple of minutes.

So I tried Don's first couple of steps (reflowing solder on encoder lead and 
front panel board U3) and that seems to have done the trick. Thanks, Don!

Just before I did this I also noted that when the tuning was not working the 
ENC A (or B, I didn't note which) was at a constant 4.3 V instead of switching 
between 5 V and something below 1 V as the tuning knob was turned, and that the 
overall power supply current dropped either 20 or 40 mA from the normal value.  
I am not sure quite what wasn't getting current but the solder reflow seems to 
have stopped it from happening.

Now if only I had gotten to this before last weekend's contest!

73,
Steve VE3SMA
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Re: [Elecraft] Erratic tuning on K2

[Steve Kavanagh via Elecraft]

 Thanks for pointing out the likely culprits, Don. That's quite a record of 
repair jobs...it's no wonder you know your way around the K2!

I figured it was unlikely to be the encoder but I thought I'd check just in 
case.

73,
Steve VE3SMA
 On Monday, June 10, 2019, 10:21:10 a.m. EDT, Don Wilhelm 
 wrote:  
 
 Steve,

It is rare to find a faulty encoder.  Those encoders are the optical 
type and almost never fail.  I have seen only one failure in the time I 
was repairing K2s and I have dealt with over 1000 repairs.

I would first reflow the soldering on the encoder wires and Front panel 
U3 as well as P1, RF Board J7 and Control Board P2.  Also reflow Control 
Board U6 pins 8 and 16.

73,
Don W3FPR

On 6/10/2019 9:09 AM, Steve Kavanagh via Elecraft wrote:
> One of my K2's has developed a problem where it is (somewhat intermittently) 
> unresponsive to turning the tuning knob.  Turning the knob may or may not, at 
> different times, cause the radio to change frequency.  Pushing on the 
> case/panels and tapping the tuning knob sometimes seem to help, so I am 
> suspicious of the board-mating connectors and solder joints for the encoder. 
> This happens regardless of tuning step size or VFO A/B choice and does not 
> affect the RIT.
> 
> A few questions before I tear into it:
> 
  
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[Elecraft] Erratic tuning on K2

[Steve Kavanagh via Elecraft]

One of my K2's has developed a problem where it is (somewhat intermittently) 
unresponsive to turning the tuning knob.  Turning the knob may or may not, at 
different times, cause the radio to change frequency.  Pushing on the 
case/panels and tapping the tuning knob sometimes seem to help, so I am 
suspicious of the board-mating connectors and solder joints for the encoder. 
This happens regardless of tuning step size or VFO A/B choice and does not 
affect the RIT.

A few questions before I tear into it:

Do the encoders ever wear out?

Has this happened to others, and if so, what have the fixes involved?

This K2 has seen a lot of use in the field and mobile as well as at home so 
humidity- or vibration/shock-induced problems are quite possible.

73,
Steve VE3SMA
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[Elecraft] K4? Or K2S?

[Steve Kavanagh via Elecraft]

If Elecraft had a rig that was an update to the K2 (same size box with no jacks 
on the sides, and all in one box unlike the KX3+KXPA100) with the following 
features, I'd be interested. I find the form factor of the K2 ideal for a rig 
that wears many different hats in the shack and portable.

(1) 6 metres included at 100 W level in the single box
(2) 100 watt capability at ~50% duty cycle all day, suitable for RTTY, FT8, 
MSK144, etc. (optional external fan?)
(3) More reliable headphone jack
(4) Eliminate the nasty stray-RF sensitivity of the XV60 transmit output 
(simple firmware or hardware mods would do it)
(5) USB control and audio interface

Other desirable features (in no particular order) would be

(6) tuning knob without the sharp edges and with a dimple
(7) reduced audio hiss at CW bandwidths, without sacrificing bandwidth on SSB 
and digital modes
(8) DSP filtering of some sort (no longer available for the K2)
(9) QRP or 100 watt versions available as now
(10) support for a few more transverter bands than the K2
(11) optional internal transverters for 2m (and higher?) in the QRP top
(12) more strip-proof threads when changing tops.
(13) improved phase noise (I have had no issues but some European VHFers find 
it too high with transverters)
(14) GPS option for high frequency accuracy, perhaps with 10 MHz output for 
transverters, and time output for computer
(15) general coverage receive
(16) AM (at least receiving) and FM capability
(17) Eliminate the strong 10m birdie from the KPA100 HV supply

It would be good to keep many characteristics of the K2, such as

(15) low power consumption
(16) wide power supply voltage range
(17) reasonably good receiver strong signal performance without spending the 
money needed to be state-of-the-art
(18) keyer speed knob on front panel
(19) configurable with options as each user requires

Kind of somewhere between an IC-7300 and a TS-590SG as far as ham-band 
capabilities are concerned but with the flexible configuration of the K2 and 
properly Elecraft-style thought-out details like no transmit spikes, proper 
timing of transmissions versus amp/transverter key output, etc.  And much 
cheaper than the K3S (somehow!).

73,
Steve VE3SMA



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[Elecraft] [K2] External Fan Hum

[Steve Kavanagh via Elecraft]

I was experimenting with an external 120V AC fan to improve the cooling of the 
KPA100 during CW Sweepstakes this past weekend.  The cooling worked fine but 
the fan caused some hum on received signals (and presumably my transmitted 
signal as well).  Placing the fan towards the right and back (away from the 
speaker) reduced the hum to a pretty-much unnoticeable level for CW, though 
through careful checking on a very strong signal I could still detect it by 
ear.  I haven't tried it yet but I suspect it isn't good enough for FT8.

I assume the K2VCOSHLDKIT would fix this.  But I also noticed, going through 
the archives that Eric had suggested a DC fan in the same location.  Does 
anyone know if I might expect less hum from a 12V DC fan?

73,
Steve VE3SMA
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Re: [Elecraft] [VHFcontesting] Alternate FT8 frequencies on 50 MHz during contests ?

[Steve Kavanagh via Elecraft]

 Hi Mike
Yes, the idea of frequencies for intercontinental DX seems to have taken off, 
but not, so far, the idea of a separate frequency for contest mode, which was 
WB5JJJ's suggestion.
73,Steve VE3SMA
On Saturday, July 7, 2018, 7:43:42 a.m. EDT, Michael Walker 
 wrote:  
 
 Steve
It did get traction.
I routinely now see FT8 signals on 50.313, 50.323 and even 50.333 at times when 
the band is open over the Atlantic.
Mike va3mw

On Sat, Jul 7, 2018 at 6:43 AM, Steve Kavanagh via Elecraft 
 wrote:

Mark

As you may know, WB5JJJ suggested using a separate frequency on 6m for contest 
mode FT8, and leaving 50.313 for those running normal FT8 format.  I tend to 
think this might work out fairly well, but it didn't gain much traction on the 
WSJT group where he posted the suggestion.

But this wouldn't necessarily result in much less QRM/pile-up depth...perhaps a 
factor of two reduction


73,
Steve VE3SMA
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Re: [Elecraft] [VHFcontesting] Alternate FT8 frequencies on 50 MHz during contests ?

[Steve Kavanagh via Elecraft]

Mark

As you may know, WB5JJJ suggested using a separate frequency on 6m for contest 
mode FT8, and leaving 50.313 for those running normal FT8 format.  I tend to 
think this might work out fairly well, but it didn't gain much traction on the 
WSJT group where he posted the suggestion.

But this wouldn't necessarily result in much less QRM/pile-up depth...perhaps a 
factor of two reduction


73,
Steve VE3SMA
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Re: [Elecraft] Laptop Power Supplies

[Steve Kavanagh via Elecraft]

My old HP supply is marked 18.5V 3.5A.  My wife's newer HP is 19.5V 2.31 A.  
The two DC plugs are very different (not sure how to specify them).  that could 
be an interesting product.  Mind you, experiments have shown that my laptop 
creates a bit of RFI from every port (USBs, audio etc.) and the screen, not 
just the power supply. But every bit that is quieter ought to help. 

73,
Steve VE3SMA
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Re: [Elecraft] [K2] Using the K2 above 29 MHz

[Steve Kavanagh via Elecraft]

I made some measurements on my K2/K60XV.  It seems the bandpass filter does cut 
off just above 28.8 MHz and the available 1 mW output from the K60XV drops 
markedly starting around 29 MHz. It would not be practical to use this output 
unless the bandpass filter were retuned.  

At the QRP antenna jack, using WSJT (and therefore presumably SSB) the power 
remains constant (when set for 2 watts) up to at least 29.4, so it seems the 
power control algorithm is doing its job.  On CW, however, when raising the 
frequency the power drops.  When starting at 29.4 MHz and going down, the power 
goes up well above 2 W.  It can be reset to 2 W by moving the power knob off 
the 2 watt setting and back again.  This isn't very practical in real 
operation, so once again, the conclusion is that to operate above 29 MHz the 
bandpass filter would need to be retuned.

73,
Steve VE3SMA
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Re: [Elecraft] [K2] Using the K2 above 29 MHz

[Steve Kavanagh via Elecraft]

OK, Dave.  Yes, I am somewhat familiar with DEMI's predecessor of the K60XV.  
It had no Elecraft-style power control, so it wouldn't surprise me if the power 
fell off with frequency above 29 MHz.  I guess I should test the 29+ MHz output 
level of the K60XV in the K2 I have with one installed.

Thanks for your info.

73,
Steve VE3SMA

On Sat, 5/19/18, Dave Sublette <k4to.d...@gmail.com> wrote:

 Subject: Re: [Elecraft] [K2] Using the K2 above 29 MHz
 To: "Steve Kavanagh" <skavanag...@yahoo.ca>
 Received: Saturday, May 19, 2018, 4:54 PM
 
 Well now
 -- I don't think I was using the K60XV.  When Steve
 Kostro developed the DEMI board, it just was wired into some
 point on the  output chain.  He changed the ON/OFF Power
 switch on the back to select either the HF QRP signal or the
 output of the transverter board at the BNC connector.  The
 output of the transverter was about 22 dBm or 220
 mw.
 Dave
 
 
 On Sat, May
 19, 2018 at 3:39 PM Steve Kavanagh <skavanag...@yahoo.ca>
 wrote:
 Thanks,
 Dave.  
 
 
 
 Were you using a K60XV transverter interface or the QRP
 antenna jack for transmit output (and if the latter, at what
 power level) ?
 
 
 
 73,
 
 Steve VE3SMA
 
 
 
 On Sat, 5/19/18, Dave Sublette <k4to.d...@gmail.com>
 wrote:
 
 
 
  Subject: Re: [Elecraft] [K2] Using the K2 above 29 MHz
 
  To: "Steve Kavanagh" <skavanag...@yahoo.ca>
 
  Cc: "Elecraft Discussion List" <elecraft@mailman.qth.net>
 
  Received: Saturday, May 19, 2018, 2:12 PM
 
 
 
  I have
 
  used my K2 with a DEMI 2M transverter board in it to
 drive
 
  transverters from 902 through  10368 MHz for many
 years. 
 
  When I used it to drive both 902 and 903 MHz portions
 of
 
  that band, the output was very much lower when 29MHz was
 in
 
  use for 903.  I can't say whether it was due to the
 29
 
  MHz IF or the 144MHz transverter output.  I didn't
 pay
 
  much attention to spurs as 902/903 is a trashy band
 
  anyway.  I have made many nice QSOs with the setup.
 
  73,
 
  Dave, K4TO
 
  On Sat, May 19,
 
  2018 at 1:18 PM Steve Kavanagh via Elecraft <elecraft@mailman.qth.net>
 
  wrote:
 
  The K2 is specified to operate
 
  on 10m only up to 28.8 MHz.  While contemplating
 possible
 
  future VHF rigs for a multi-operator multi-band
 environment,
 
  I have wondered about using a K2 as an IF for VHF
 
  transverters at around 29-29.4 MHz (to avoid
 interference
 
  with bands using 28 MHz IF).
 
 
 
 
 
 
 
  Both of my K2s seem to operate (VFO synthesizer works) up
 to
 
  30 MHz.  At 29.5 MHz the available transmit power (QRP)
 is
 
  starting to drop off and this is quite noticeable at 30
 
  MHz.  The QRP PA efficiency drops off somewhat as
 well. 
 
  There are a few receive birdies on the 100 watt radio,
 but
 
  the QRP one is pretty quiet - nothing that should be
 
  noticeable under the extra noise coming from a
 
  transverter.  Turning the preamp on makes extra noise as
 it
 
  should (but it is after the bandpass filters so that
 
  doesn't mean a whole lot).  But it seems that it
 should
 
  work ok as long as I don't want more than 4-5 watts
 
  (most likely I'd use a K60XV), perhaps with a bit
 of
 
  bandpass filter tweaking.
 
 
 
 
 
 
 
  Are there any caveats that I am unaware of?  Spurious
 
  emissions, perhaps?  Has anyone tried using their K2
 above
 
  29 MHz?
 
 
 
 
 
 
 
  73,
 
 
 
  Steve VE3SMA
 
 
 
  __
 
 
 
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  Home: http://mailman.qth.net/mailman/listinfo/elecraft
 
 
 
  Help: http://mailman.qth.net/mmfaq.htm
 
 
 
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Re: [Elecraft] [K2] Using the K2 above 29 MHz

[Steve Kavanagh via Elecraft]

Thanks, Dave.  

Were you using a K60XV transverter interface or the QRP antenna jack for 
transmit output (and if the latter, at what power level) ?

73,
Steve VE3SMA

On Sat, 5/19/18, Dave Sublette <k4to.d...@gmail.com> wrote:

 Subject: Re: [Elecraft] [K2] Using the K2 above 29 MHz
 To: "Steve Kavanagh" <skavanag...@yahoo.ca>
 Cc: "Elecraft Discussion List" <elecraft@mailman.qth.net>
 Received: Saturday, May 19, 2018, 2:12 PM
 
 I have
 used my K2 with a DEMI 2M transverter board in it to drive
 transverters from 902 through  10368 MHz for many years. 
 When I used it to drive both 902 and 903 MHz portions of
 that band, the output was very much lower when 29MHz was in
 use for 903.  I can't say whether it was due to the 29
 MHz IF or the 144MHz transverter output.  I didn't pay
 much attention to spurs as 902/903 is a trashy band
 anyway.  I have made many nice QSOs with the setup.
 73,
 Dave, K4TO
 On Sat, May 19,
 2018 at 1:18 PM Steve Kavanagh via Elecraft <elecraft@mailman.qth.net>
 wrote:
 The K2 is specified to operate
 on 10m only up to 28.8 MHz.  While contemplating possible
 future VHF rigs for a multi-operator multi-band environment,
 I have wondered about using a K2 as an IF for VHF
 transverters at around 29-29.4 MHz (to avoid interference
 with bands using 28 MHz IF).
 
 
 
 Both of my K2s seem to operate (VFO synthesizer works) up to
 30 MHz.  At 29.5 MHz the available transmit power (QRP) is
 starting to drop off and this is quite noticeable at 30
 MHz.  The QRP PA efficiency drops off somewhat as well. 
 There are a few receive birdies on the 100 watt radio, but
 the QRP one is pretty quiet - nothing that should be
 noticeable under the extra noise coming from a
 transverter.  Turning the preamp on makes extra noise as it
 should (but it is after the bandpass filters so that
 doesn't mean a whole lot).  But it seems that it should
 work ok as long as I don't want more than 4-5 watts
 (most likely I'd use a K60XV), perhaps with a bit of
 bandpass filter tweaking.
 
 
 
 Are there any caveats that I am unaware of?  Spurious
 emissions, perhaps?  Has anyone tried using their K2 above
 29 MHz?
 
 
 
 73,
 
 Steve VE3SMA
 
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[Elecraft] [K2] Using the K2 above 29 MHz

[Steve Kavanagh via Elecraft]

The K2 is specified to operate on 10m only up to 28.8 MHz.  While contemplating 
possible future VHF rigs for a multi-operator multi-band environment, I have 
wondered about using a K2 as an IF for VHF transverters at around 29-29.4 MHz 
(to avoid interference with bands using 28 MHz IF).

Both of my K2s seem to operate (VFO synthesizer works) up to 30 MHz.  At 29.5 
MHz the available transmit power (QRP) is starting to drop off and this is 
quite noticeable at 30 MHz.  The QRP PA efficiency drops off somewhat as well.  
There are a few receive birdies on the 100 watt radio, but the QRP one is 
pretty quiet - nothing that should be noticeable under the extra noise coming 
from a transverter.  Turning the preamp on makes extra noise as it should (but 
it is after the bandpass filters so that doesn't mean a whole lot).  But it 
seems that it should work ok as long as I don't want more than 4-5 watts (most 
likely I'd use a K60XV), perhaps with a bit of bandpass filter tweaking.

Are there any caveats that I am unaware of?  Spurious emissions, perhaps?  Has 
anyone tried using their K2 above 29 MHz?

73,
Steve VE3SMA
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Re: [Elecraft] Modifying the K2 for use as an IF radio for the microwave bands

[Steve Kavanagh via Elecraft]

There's been several good points made about my K2 internal 2m transverter 
project...here's a bit of my thinking about why I went the way I did:

(1) Using an alternate transverter (VE3SYB) - I did consider the Transverters 
Unlimited board from the Ukraine to potentially give me more output, but in any 
case it would require some modification to reduce the output from several watts 
to 100 mW.  In the end, since I had acquired the quasi-DEMI transverter at a 
flea market already, I decided just to go with it.  

I think it would be pushing the state-of-the-art in high-level mixer technology 
to make a mixer which would directly take ~ 1 watt in and produce 100 mW out at 
144 MHz, without either pre-attenuation or post-amplification, but it might 
just be possible.

(2) Using the K60XV transverter interface (W3FPR) - I thought about that option 
and eventually decided against it, primarily because of the extreme sensitivity 
of the K60XV output to RF signals getting into it and causing the K2 receiver 
to shut down (an odd quirk of the circuitry and firmware). Using a modified 
version is an interesting possibility which didn't occur to me - maybe enough 
space could be freed up to build a filter or buffer amp on the original board 
to fix that problem! I do have a K60XV in my other K2 which I have used with 
good results on 50/144/222/432 MHz, but it does require an external filter on 
the output RF jack to prevent weirdness from happening when other nearby 
transmitters are active!

(3) K1WHS interface (K1WHS) - I suspect this is much the same as what DEMI made 
for a while before the K60XV came out (and it was much cheaper than the K60XV, 
too).  N2CEI was nice enough to give me one after they stopped producing them.  
I tried it but decided I missed the full Elecraft-style front panel RF power 
control which it did not support.  I recall Dave telling me years ago that the 
K2 made a pretty good IF radio, so it's been in my mind since then!  I can 
confirm that I too get a group of strong birdies near 145.1 MHz, but as I am 
using 144.1 MHz as my IF this is not a problem for me.

(4) Internal 630m transverter (KE6US) - sounds like a great project! For 2200m, 
maybe not, as one might want better frequency accuracy in such a narrow band 
than the K2 can provide.

73,
Steve VE3SMA
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[Elecraft] Modifying the K2 for use as an IF radio for the microwave bands

[Steve Kavanagh via Elecraft]

For a while now I've been working on a project to install a low power 2 metre 
transverter inside an Elecraft K2, in order to use it as an IF transceiver with 
transverters for the microwave bands.  I got it done this summer and used it on 
10 GHz during the ARRL 10 GHz and Up Contest, as a "plug-and-play" replacement 
for one of my aging FT-290Rs.  I have just finished writing this project up, as 
it may be of interest to other microwavers.  The description is at  

http://www.qsl.net/ve3sma/TheK290RProject.pdf .  

Happy reading!

73,
Steve VE3SMA
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Re: [Elecraft] K3: 2 meter SSB/CW Capability Questions

[Steve Kavanagh via Elecraft]

Phil

One possible way to make a decision is to consider whether or not you might 
want to try meteor scatter on 2m using MSK144.  The recommended absolute 
frequency accuracy for that mode is 25 Hz (though I think you'd get away with 
80 Hz). This is a real challenge at 2m and the XV144 isn't really up to it, 
though I have managed a few MS QSOs using a K2/XV144/amp combo.

73,
Steve VE3SMA
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[Elecraft] [K2] Frequency Calibration using WWV Audio Tones

[Steve Kavanagh via Elecraft]

I was wondering if anyone had tried doing the reference oscillator frequency 
calibration for a K2 without the rather troublesome step of accurate 
zero-beating by feeding the 500/600 Hz audio tones from WWV/WWVH to a computer 
sound card or smart phone spectrum analyzer, or similar program?  It's pretty 
easy to read these audio frequencies out to a precision of 1 Hz or so using 
Spectran or Spectrogram, for example. 

Right now, I'm seeing both WWV and WWVH tones (at the same time!) on my 
computer screen (within a few Hz of the correct audio frequencies), with the K2 
tuned to 15000.24 kHz, so it really ought to be re-calibrated.

Are there any issues with this option, before I start into the whole process? 

73,
Steve VE3SMA
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Re: [Elecraft] MH4 Microphone Questions

[Steve Kavanagh via Elecraft]

Thanks, Wayne.  Very tempting!

73,
Steve VE3SMA

On Sun, 9/3/17, Wayne Burdick  wrote:

  > Can anyone confirm that the dimensions match?  
 
 They do. It’s the same size as our MH3, used with the KX2 and KX3.
  
 > Has anyone tried out the MH4 for audio quality yet?
 
 We’ve done a lot of in-house testing of the MH4, and it works great. This
 isn’t surprising given that it’s the same element we used in the MH3.
 
 73,
 Wayne
 N6KR
  
 
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[Elecraft] MH4 Microphone Questions

[Steve Kavanagh via Elecraft]

I find the MH2 a bit on the large side for my hands, so the MH4 looks 
interesting to me.  The case appears to be identical to the Icom HM-36,which I 
use with one of my K2s and find very comfortable to hold.  

Can anyone confirm that the dimensions match?  

Has anyone tried out the MH4 for audio quality yet?

73,
Steve VE3SMA
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Re: [Elecraft] [K2] Sensitivity Spec

[Steve Kavanagh via Elecraft]

Thanks for your comments, Don.  When you test K2's, can I assume you have the 
signal generator connected directly to the K2 (or through an attenuator) with 
no antenna connected?

Normally, one might hope that a preamp would provide some improvement in 
receiver noise figure (and hence MDS, sensitivity, noise floor), or there isn't 
much point in having it. I've never run into an intermodulation or blocking 
problem on 10 GHz (sideband noise issues tend to dominate the *rare* strong 
signal scenario) so I expect to leave the K2 preamp on in an attempt to 
maximize the sensitivity 

I agree that most often transverters have lots of gain but I noticed, with the 
particular combination I have, that the increase in receiver noise output 
resulting from turning on both the 10 GHz-to-144 MHz and the 144 MHz-to-28 MHz 
transverters was only about 7 dB (K2 preamp on, AGC off) compared to the K2 
alone, rather less than usually seems to be the case, so I was afraid that the 
front end noise might not dominate the overall receiver noise.  The 
intermediate transverter does have relatively low gain, by design.  With a 
couple of tweaks and a minor repair in the transverters I've now increased this 
ratio by a couple of dB.

Since the 10 GHz transverter noise figure was measured by the manufacturer at 
1.2 dB and the K2 is something closer to 10 dB the increase in noise may not 
have to be all that much for the system to be working right.  I haven't felt up 
to doing all the necessary math this week to make sure, especially without a 
reliable number for the K2 noise figure.  Most likely I'll try it out in the 10 
GHz and Up contest this weekend and if it proves to be deaf compared to others' 
rigs, I'll have to delve deeper.

73,
Steve VE3SMA

On Tue, 8/15/17, Don Wilhelm <donw...@embarqmail.com> wrote:

 Subject: Re: [Elecraft] [K2] Sensitivity Spec
 To: "Steve Kavanagh" <skavanag...@yahoo.ca>, elecraft@mailman.qth.net
 Received: Tuesday, August 15, 2017, 8:29 PM
 
 Steve,
 
 Typically, the receiver is limited by the noise
 floor, so the MDS will 
 not change much
 whether the preamp is on or off.  While the preamp will 
 increase the strength of the signals, it also
 adds to the noise floor.
 
 Generally a transverter will have a low noise
 preamp with plenty of 
 gain, so there is
 usually no advantage in running the transceiver with 
 the preamp on.  Use your ears while listening
 to a strong signal to see 
 if you can detect
 overload of the receiver preamp - if so turn it off, 
 but if there is no overload distortion, you can
 leave it on.
 
 Typical MDS
 measurements are made at 500 Hz.
 I typically
 do a quick test of the sensitivity of K2s that I repair.  A
 
 -130dBm signal should be detectable above
 the receiver noise floor.  For 
 that test,
 I have observed that it makes little difference whether the
 
 preamp is on or off.  So I would suggest
 you test whether strong signal 
 performance
 is better with the preamp on or off.  My wager is that you
 
 will choose to leave it off unless your
 transverter(s) have negative 
 gain on RX.
 
 73,
 Don
 W3FPR
 
 On 8/15/2017 4:10 PM, Steve
 Kavanagh via Elecraft wrote:
 > I'm
 just trying to evaluate if I have the gain distribution
 right for a K2 used as an IF for a 10 GHz transverter,
 through a 2 m transverter mounted inside the QRP top.  The
 K2 manual gives a specification for the MDS but fails to
 define the bandwidth at which it is measured. 
 Sherwood's receiver table lists some measured values at
 500 Hz bandwidth but fails to note whether the preamp is on
 or off for these measurements.  So I am not quite sure what
 the sensitivity should be.
 
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[Elecraft] [K2] Sensitivity Spec

[Steve Kavanagh via Elecraft]

I'm just trying to evaluate if I have the gain distribution right for a K2 used 
as an IF for a 10 GHz transverter, through a 2 m transverter mounted inside the 
QRP top.  The K2 manual gives a specification for the MDS but fails to define 
the bandwidth at which it is measured.  Sherwood's receiver table lists some 
measured values at 500 Hz bandwidth but fails to note whether the preamp is on 
or off for these measurements.  So I am not quite sure what the sensitivity 
should be.  

Can anyone clarify?

73,
Steve VE3SMA
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[Elecraft] [K2] Odd "Hi Refl"/high current problem only in TUNE

[Steve Kavanagh via Elecraft]

This one cropped up just today, with no significant change in my home station 
setup, using a K2/100 on 40m using a low inverted Vee.

Sometimes (typically every other or every third time, but randomly), when 
pushing (and holding) the tune button with the power set to 11 watts or more, I 
get a high reflected power message on an antenna which is matched at low power. 
 The power supply voltage reads about the normal 14V and the ammeter in the 
power supply is pinned at 25 A (or more) when this happens.  An external SWR 
meter reads lots of reflected power.  Everything unplugged from the rig except 
the power cable and the coax to the external SWR meter/antenna tuner/antenna. 
It's fine on a dummy load.

I'd suspect a simple RF feedback problem, except that with 100 watts of CW 
everything is perfectly normal.  The problem occurs only when using the tune 
button around the nominal tune-mode 20 watts, so the external SWR meter reading 
implies that the PA is probably oscillating at some frequency where the antenna 
is not matched.  I haven't tried any other bands yet, but since there does seem 
to be RF feedback involved, I'm not sure they will tell me much of a diagnostic 
nature.

Any ideas as to what might be happening and how to stop it?

73,
Steve VE3SMA
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Re: [Elecraft] [K2] External amplifier keying circuit question

[Steve Kavanagh via Elecraft]

Initial testing using the two-MOSFET circuit 
(http://www.mmccs.com/mmarc/n0ss/k2_t-r_rly_drvr.pdf ) with two 2N7000s, but 
with R3 removed, indicates that it is working fine, switching a load of about 
50 mA at 12-13V.  I left R2 in.

Thanks all for your comments.

73,
Steve VE3SMA
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Re: [Elecraft] [K2] External amplifier keying circuit question

[Steve Kavanagh via Elecraft]

Thanks, Don.  Good point re the input side...I guess I'm not used to having 
plug-in boards in mind! 

Yes, I was thinking of a pair of 2N7000s - they are fine for the current and 
voltage I need to switch.

73,
Steve VE3SMA

   
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[Elecraft] [K2] External amplifier keying circuit question

[Steve Kavanagh via Elecraft]

 I'm planning to add an external amplifier/transverter keying circuit to one of 
my K2s.  I found two versions on the web, both apparently designed by N0SS 
(SK).  The one on the Elecraft site 
(http://www.elecraft.com/Apps/Amp_keying_ckt.htm ) appears to be his original 
circuit, using a 2N7000 driving a 2N.  The archive of Tom's later kit 
offering (http://www.mmccs.com/mmarc/n0ss/k2_t-r_rly_drvr.pdf ) uses two 
MOSFETs and is capable of keying somewhat higher voltage and current.  But also 
he added a 100k resistor from the input gate (8R) to ground and another from 
the gate of the second MOSFET to ground.
I am trying to figure out if these two 100 k resistors serve any useful purpose 
or if I can happily leave them both out of the 2-MOSFET circuit.  There doesn't 
immediately appear to be any need to pull these gates down as there are several 
loads on the input 8R voltage (on the K2 RF board) which will do that for the 
1st MOSFET, and the 1st MOSFET will pull down the gate of the 2nd one when 
needed.  Maybe something odd will happen on power-up or power-down?
Any thoughts?
73,Steve VE3SMA
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