[Elecraft] KX1 Power Measurement

Sat Nov 29 13:11:00 2003

I have made measurements of my KX1 since changing the value of R30 from 22
ohms to 33 ohms. I used a WM2 watt meter into a good 50 ohm dummy load. I
find my readings to be in line with what the manual states now. Both the KX1
power output and the watt meter agree. Antenna tuner is in the CAL mode for
these results.

Power supply 14.1 volts not transmitting
20 meters 3.5 watts
40 meters 4.0 watts
30 meters 4.5 watts

Internal batteries 8.6 volts
20 meters .9 watts
40 meters 1.1 watts
30 meters 1.4 watts

Before changing R30 without 30 meter module or ATU
Power Supply 13.5 volts
20 meters 2.5 watts
40 meters 3.2 watts

Internal Batteries 9 volts
20 Meters .75 watts
40 meters 1.2 watts

I am extremely pleased with the rig. It receives well and is a blast to
operate. Ron did an outstanding job with the manual. In my case changing R30
to 33 ohms made the difference I was looking for. I am within specs of what
the manual states for output power. I have no stability issues with the
output. I am getting great signal reports with very good sounding transmit
audio. I do agree with Ron's previous comments about being careful if you
decide to change the value of R30 and stability issues. I also want to
caution everyone as Phil and I have found out. It is not easy to replace R30
once it is installed. It would be very easy to damage a relay, trim cap and
possible other components be careful. One other word of caution be sure to
do the resistance check on either solder pad for toroid L3 and ground. (See
page 55 in the manual) If you do not do this check every time the top cover
is removed and installed you can damage the final and other components if
there is a short to ground!

Thanks Ron for all your input and hard work with the KX1
Glenn Maclean WA7SPY

----- Original Message ----- 
From: "Phil Wheeler" <[email protected]>
To: "John C Ceccherelli" <[email protected]>
Cc: <[email protected]>
Sent: Saturday, November 29, 2003 09:40
Subject: Re: [Elecraft] KX1 Power Measurement

> John,
>
> A few years back Steve Weber kitted a digital qrp (0-10 W) wattmeter
> which is very accurate and includes a precise dummy load internally.  It
> beats anything else out there in the qrp range and likely does better
> than I could with my scope. It is what I use when I really care about
> understanding my test outputs accurately.  Since it is not inline (no
> antenna port with the dummy load internal) it is only good for testing.
>
> Your three-band outputs are surpisingly close -- perhaps too close,
> since the manual says L2 should be adjusted so that 20 m output is 0.3
> to 0.6 W less than on 40 m.  OTOH -- my 20 m output appears to low in
> comparison to 40 m -- and I am going to recheck the transformer (since
> that is the only toroid I've not triple checked).
>
> But in reality and for what we are about, your values or mine should
> certainly get the job done.  BTW -- my results were with a 13.8 V supply
> but 13.6 displayed at the rig -- which I assume is what you mean by 13.6
> V below.  I assume, also, that you are using the default value of R30
> (22 ohms): True?
>
> The variances in reported output of the KX1 are not all that
> surprising.  I suspect much of it is differences in measurement using
> different meters, as you suggest.  But surely that does not explain the
> ratio differences (4.1/4.1/4.0 in your case vs. 4.5/5.0/3.4 in my case
> and 4.1/4.8/3.8 in Ron's case).  Interestingly, only Ron's value have 20
> m in the 0.3 to 0.6 W less than 40 m mentioned in the manual; my
> difference is much more and yours only 0.1 W.
>
> Now - back to the shack :-)  I want to get the ATU and battery supply
> finished today.
>
> 73,  Phil
>
> John C Ceccherelli wrote:
>
> >
> >
> >My KX1 (s/n 179) at 13.6 Volts puts out the following
> >
> >40M - 4.1 W
> >30M - 4.1 W
> >20M - 4.0 W
> >
> >With fresh alkyline batteries it's about 1.5 watts.  Maybe a tad lower on
> >20 M but I haven't put a scope to it.
> >
> >I have found that every watt meter I have is grossly inaccurate at some
> >part of the scale.  i.e, adjust it to be accurate at full deflection and
> >it's way off mid-scale etc.  If you have a calibrated oscilloscope or RF
> >voltmeter, you stand a better chance of know what your actual power
output
> >really is.  Most people agree that the Oak Hills QRP wattmeter is
accurate
> >but I don't have one so can't say from personal experience.
> >
> >I would suggest that if you're really hung up about power output, obtain
or
> >borrow accurate equipment to make the measurement.  SWR/Wattmeters are
> >usually way off particularly at QRP power levels.
> >
> >N2XE
> >
> >John Ceccherelli
> >
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> >
> >
>
>
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