KX1 #01221 Alive but shy of stated power?

[Jeremy Cowgar-2]

Enjoyed putting my KX1 together and tuning around the bands but when it
comes to transmitting, I'm wonder if something is slightly wrong or no.

Power out:

13.5v: 40m = 3.8w (39ppv), 20m = 3.06 (35ppv)
9v: 40m = 1.32w (23ppv), 20m = 2.25 (30ppv)

The 9v 20m output is strange to me. Have checked current draw yet, I
gotta get some sleep (built all last night, 6:30am here now).

Any ideas?

Jeremy
KB8LFA

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[Coote, Jay]

Jeremy and List;
Your KX-1 turned out better than mine.  My 10 MHz band is weak and noisy
on receive plus I had the following transmitter problems:
I had 4 watts/7MHz and 10 MHz,  2.6 watts/14 MHz at 13.8V;   1.4
watts/7MHz and 0.8 watts/14 MHz at 9.0V.
I've tried the changes in R11 and R30 to increase power output, however
this just increases power and does nothing for my 14 MHz power roll-off.
Mine obviously does not meet spec and it is good to have suggestions on
what to try next from Elecraft.  I've heard of people getting 4 watts or
more, nearly flat across all three bands.  That power rise on 14 MHz at
9V does sound odd... I would have guessed it to be around 1 watt.  Is
your power supply at 9V delivering enough current or is there a voltage
drop- possibly preventing a relay from opening/closing and changing the
specs of the RF filters on the PA?... A guess.  
Jay
W6CJ

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jeremy Cowgar
Sent: Thursday, August 04, 2005 3:28 AM
To: [hidden email]
Subject: [Elecraft] KX1 #01221 Alive but shy of stated power?

Enjoyed putting my KX1 together and tuning around the bands but when it
comes to transmitting, I'm wonder if something is slightly wrong or no.

Power out:

13.5v: 40m = 3.8w (39ppv), 20m = 3.06 (35ppv)
9v: 40m = 1.32w (23ppv), 20m = 2.25 (30ppv)

The 9v 20m output is strange to me. Have checked current draw yet, I
gotta get some sleep (built all last night, 6:30am here now).

Any ideas?

Jeremy
KB8LFA

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[Grif-2]

> WHAT are the changes to R11 and R30???? Everyone is referring to them, but
> no-one has said what they are!!
>
> Grif, KF4JG
>
> ----- Original Message -----
> From: "Coote, Jay" <[hidden email]>
> To: "Jeremy Cowgar" <[hidden email]>; <[hidden email]>
> Sent: Thursday, August 04, 2005 10:04 AM
> Subject: RE: [Elecraft] KX1 #01221 Alive but shy of stated power?
>
>
> Jeremy and List;
> Your KX-1 turned out better than mine.  My 10 MHz band is weak and noisy
> on receive plus I had the following transmitter problems:
> I had 4 watts/7MHz and 10 MHz,  2.6 watts/14 MHz at 13.8V;   1.4
> watts/7MHz and 0.8 watts/14 MHz at 9.0V.
> I've tried the changes in R11 and R30 to increase power output, however
> this just increases power and does nothing for my 14 MHz power roll-off.
> Mine obviously does not meet spec and it is good to have suggestions on
> what to try next from Elecraft.  I've heard of people getting 4 watts or
> more, nearly flat across all three bands.  That power rise on 14 MHz at
> 9V does sound odd... I would have guessed it to be around 1 watt.  Is
> your power supply at 9V delivering enough current or is there a voltage
> drop- possibly preventing a relay from opening/closing and changing the
> specs of the RF filters on the PA?... A guess.
> Jay
> W6CJ
>
>

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[Jeremy Cowgar-2]

Why the difference, they are all the same rig why would it change from
rig to rig?

Jeremy
KB8LFA

Coote, Jay wrote:

>Jeremy and List;
>Your KX-1 turned out better than mine.  My 10 MHz band is weak and noisy
>on receive plus I had the following transmitter problems:
>I had 4 watts/7MHz and 10 MHz,  2.6 watts/14 MHz at 13.8V;   1.4
>watts/7MHz and 0.8 watts/14 MHz at 9.0V.
>I've tried the changes in R11 and R30 to increase power output, however
>this just increases power and does nothing for my 14 MHz power roll-off.
>Mine obviously does not meet spec and it is good to have suggestions on
>what to try next from Elecraft.  I've heard of people getting 4 watts or
>more, nearly flat across all three bands.  That power rise on 14 MHz at
>9V does sound odd... I would have guessed it to be around 1 watt.  Is
>your power supply at 9V delivering enough current or is there a voltage
>drop- possibly preventing a relay from opening/closing and changing the
>specs of the RF filters on the PA?... A guess.  
>  
>

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[David F. Reed]

Jeremy,

think of mechanical tolerance issues for a minute; let's say, a shaft
and a bearing for example; take 1/4 inch diameter, with some tolerance
and take the specifications; imagine the diameter specs are .250 inch,
but to make sure it fits, the hole in the bearing might be specified at
0.251 +/- .002, and the shaft might be specified at 0.249 +/- .001  so
as you grab parts out of bins, these tolerances vary, so you could end
up with bearings ranging from 0.249 to 0.253 inches, and shafts ranging
in diameter from 0.248 to 0.250; if the parts are from opposite ends of
variance, they are either loose, or too tight; and some are just right.

Take it to an electrical circuit; the parts have tolerances too, and for
caps and inductors, the resulting resonant frequencies are different;
now take the toroids; how evenly the windings are spaced affects it
somewhat in value.  The transistors will vary in parameters also, having
slightly different gain and requiring slightly different biasing to get
that gain.

This is why the circuits have adjustments, such as the trimmer caps and
resistors; so that you can get these circuits to perform "as designed".  
Imagine now that all of the components have some tolerances, and you can
see that "plug and play" is not so easy in the analog world, and we end
up with these variations.

Then there is the measurement issue on top of that; our watt meters have
the same issues, and calibration issues as well; so we might all be
using the same watt meter, and if I take my radio to all of us, it will
measure slightly different output, based on slightly different
temperature, slightly different impedance of load, slightly different
supply voltage, and variations in watt meters.

That is where knowing the resolution and accuracy of the test equipment
come to play.

Probably more than you wanted to know, but there are a lot of variables
contributing to the variations reported, to say nothing of damaged parts
and shorts and stuff that throw it all off.

73 de W5SV, Dave

Jeremy Cowgar wrote:

> Why the difference, they are all the same rig why would it change from
> rig to rig?
>
> Jeremy
> KB8LFA

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[Jeremy Cowgar-2]

>
>
>  
>
>>WHAT are the changes to R11 and R30???? Everyone is referring to them, but
>>no-one has said what they are!!
>>
I was reading past posts about the KX1 and stumbled across this post:

http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-11/msg01045.html

--------

*To*: [hidden email] <mailto:Elecraft%40mailman.qth.net>
*Subject*: Re: [Elecraft] KX1 Power Measurements by band
*From*: [hidden email] <mailto:DYARNES%40aol.com>
*Date*: Sat, 29 Nov 2003 09:12:05 EST

Add me to the list of those experiencing low power output.  I was getting
under 2 watts on 40, and just over 2 watts on 30 and 20.  Gary suggested I
increase R30 to 27 ohms and decrease R11 to between 3.3 ohms and 5.6 ohms
(after
first suggesting I check the toroids, etc.).  I made the above changes and my
power out went to about 2.5 on 40, and just over 3 watts on 30 and 20.  I had
been behind in monitoring the reflector, and now I see the other comments about
low power.  I had gathered from my exchanges with Gary that I wasn't the only
one with this problem.  So, I guess I will dig back in and up the value for R30
a bit more.  Thanks to the NorCal resistor kit, I have a nice supply.  Then,
hopefully, squeezing the turns on L2 will be necessary (it wasn't before
obviously).  My guess is, though, that I still won't get to the power levels
that
Ron and Phil are reporting.  We'll see.

I am also noticing the lack of audio output that others mentioned, although
on 40 it seems pretty good.  It's just on 30 and 20 that it seems a little
"light".  But the RX doesn't seem to miss much sensitivity wise.  Pretty darn
good
RX design I'd say.  Everything else seems to be working like a charm!

Dave W7AQK


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[Jeremy Cowgar-2]

>>> WHAT are the changes to R11 and R30???? Everyone is referring to
>>> them, but
>>> no-one has said what they are!!
>>>
> I was reading past posts about the KX1 and stumbled across this post:
>
> http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-11/msg01045.html
>
I also read quite a bit about compressing L2 to 70% or so instead of 90%
for low power problems. Have not tried either, but compressing L2 seems
like a much easier task than swapping the resistors. I will try that
tonight and let people know how I fare.

Jeremy
KB8LFA

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[Ron D'Eau Claire-2]

Jeremy, KB8LFA wrote:
I also read quite a bit about compressing L2 to 70% or so instead of 90%
for low power problems. Have not tried either, but compressing L2 seems
like a much easier task than swapping the resistors. I will try that
tonight and let people know how I fare.

---------------------------------------

The purpose of adjusting L2 spacing is to change the roll-off characteristic
of the output low-pass filter. It won't do much (or anything) for the output
on 40.

If the output on 20 meters is more than about 0.6 watts LOWER than the
output 40, squeezing the turns on L2 will often increase the 20 meter output
by changing the high-frequency roll-off characteristic of the filter.

It's a BAD idea to try to get as much output on 20 as you have on 40. If the
20 meter output is more than about 0.3 watts below the output on 40, your
output filter is NOT attenuating the harmonics like it should. You are
emitting excessive harmonic energy. The KX1 was designed to be a 'clean' rig
and to be clean the 20 meter output must be 0.3 to 0.6 watts lower than the
output on 40.  

About those two resistors, the original recommendation came from Gary I
believe. Changing them will increase the overall  output of the KX1 on all
bands if it is below spec. He's quoted as saying:

"...reducing R11 in Q5's emitter to 3.3 to 5.6 ohms and increasing R30 on
Q6's base to 27-33 ohms... R30 should not be made larger than 33 ohms to
prevent problem when the atu operates, and unless a spectrum analyzer is
available to check the
transmitter output for purity."


Ron AC7AC



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[Coote, Jay]

 
Jeremy and List;
(See below)
My guess on power variations would be:
1.  Core/winding variations in the RF PA output inductors and capacitors
2.  Variations in the DDS lowpass filter inductors/caps
3.  Variations in freq response of Q4, Q5 or Q6
4.  Bad Q6

Jay
W6CJ
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jeremy Cowgar
Sent: Thursday, August 04, 2005 8:20 AM
To: [hidden email]
Subject: Re: [Elecraft] KX1 #01221 Alive but shy of stated power?

Why the difference, they are all the same rig why would it change from
rig to rig?

Jeremy
KB8LFA

Coote, Jay wrote:

>Jeremy and List;
>Your KX-1 turned out better than mine.  My 10 MHz band is weak and
>noisy on receive plus I had the following transmitter problems:
>I had 4 watts/7MHz and 10 MHz,  2.6 watts/14 MHz at 13.8V;   1.4
>watts/7MHz and 0.8 watts/14 MHz at 9.0V.
>I've tried the changes in R11 and R30 to increase power output, however

>this just increases power and does nothing for my 14 MHz power
roll-off.
>Mine obviously does not meet spec and it is good to have suggestions on

>what to try next from Elecraft.  I've heard of people getting 4 watts
>or more, nearly flat across all three bands.  That power rise on 14 MHz

>at 9V does sound odd... I would have guessed it to be around 1 watt.  
>Is your power supply at 9V delivering enough current or is there a
>voltage
>drop- possibly preventing a relay from opening/closing and changing the

>specs of the RF filters on the PA?... A guess.
>  
>

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[Mike Morrow-3]

Grif wrote:

> WHAT are the changes to R11 and R30???? Everyone is referring to them, but
> no-one has said what they are!!

Must be a dark secret, Grif.  Nobody seems to want to tell, apparently least of all the folks who report having performed the mods!

I'd help if I knew...but I don't have a KX1.

I looked at KX1-related info on the elecraft web site (Tech Notes and Builder's Resources), but there seems to be *NOTHING* there at all.  Nada.  Zip.  Null.  Zero.  That is most odd, considering that the KX1 has been out for two years.

In contrast, K1 and K2 owners will find a wealth of info there.

73,
Mike / KK5F
 
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[Coote, Jay]

Hi All,
Maybe my emails were not getting through.
R11 and R30 mods in the KX-1 will increase output power but won't do
amything for low transmitter power on 20M (etc).
R11 can be changed to 3.3-5.6 ohms and R30 can be changed to 27-33 Ohms
but do not exceed 33 ohms.  I have this from Elecraft.  After the mod
you may have to back down R4 to keep power output below 4 watts.  The
KX-1 is not designed to take 5 watts
Jay
W6CJ

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Mike Morrow
Sent: Thursday, August 04, 2005 10:37 AM
To: Grif; [hidden email]
Subject: Re: [Elecraft] KX1 #01221 Alive but shy of stated power?

Grif wrote:

> WHAT are the changes to R11 and R30???? Everyone is referring to them,

> but no-one has said what they are!!

Must be a dark secret, Grif.  Nobody seems to want to tell, apparently
least of all the folks who report having performed the mods!

I'd help if I knew...but I don't have a KX1.

I looked at KX1-related info on the elecraft web site (Tech Notes and
Builder's Resources), but there seems to be *NOTHING* there at all.
Nada.  Zip.  Null.  Zero.  That is most odd, considering that the KX1
has been out for two years.

In contrast, K1 and K2 owners will find a wealth of info there.

73,
Mike / KK5F
 
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[Bill Johnson-10]

Bill


....

>> WHAT are the changes to R11 and R30???? Everyone is referring to them,
but
>> no-one has said what they are!!

>Must be a dark secret, Grif.  Nobody seems to want to tell, apparently
>least of all the folks who report having performed the mods!
....

A small difference in power isn't worth consideration vs the importance of a
clean signal.  A change from 4 w to 2 w is only 3 db which is not notable
for audio difference. Thus some of us who have owned for the entire time
haven't paid any long lasting attention.  I have never operated any QRP rig
at it's full power.  The reduced power has a huge advantage in battery life
and has little to no impact on the receiving station's ability to copy.  

Bill
K9YEQ
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[WA7SPY]

Bill Johnson wrote:

>Bill
>
>
>....
>
>  
>
>>>WHAT are the changes to R11 and R30???? Everyone is referring to them,
>>>      
>>>
>but
>  
>
>>>no-one has said what they are!!
>>>      
>>>
>
>  
>
>>Must be a dark secret, Grif.  Nobody seems to want to tell, apparently
>>least of all the folks who report having performed the mods!
>>    
>>
>....
>
>A small difference in power isn't worth consideration vs the importance of a
>clean signal.  A change from 4 w to 2 w is only 3 db which is not notable
>for audio difference. Thus some of us who have owned for the entire time
>haven't paid any long lasting attention.  I have never operated any QRP rig
>at it's full power.  The reduced power has a huge advantage in battery life
>and has little to no impact on the receiving station's ability to copy.  
>
>Bill
>K9YEQ
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>
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>Elecraft web page: http://www.elecraft.com
>  
>

I do not have a KX1 anymore. It is a long story. I was able to dig
through my old sent email messages. I purchased and built an early
serial number KX1. I hope this help you.
Glenn Maclean WA7SPY
Sacramento, CA

Here is what Gary at Elecraft had to say. I went by his guide lines. 33
ohms worked well in my case. Your milage may very. Yes it is OK to
change R30 do not go any more than 47 ohms. (See below)
 
Hi All;
Here is the comments from Gary at Elecraft concerning the Low Power
conidition of the KX-1.

Those output levels are typical and are pretty normal. You will only get
3-4w if 13.8 to 14.0VDC is used, and the load is a good 50 ohm non-reactive
match.

The KX1 is not designed to produce 4-5w (or more) like the K1 can, as it
has
a much simpler transmitter and is optimized for mainly portable and battery
use.

If all parts are correct, you can safely increase R30 at the base of the PA
transistor Q6, but not more than 33-47 ohms or increased spurious output
will result. 33 ohms would be a good first value to try.


--
73, Gary AB7MY

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