I have to slip a plug in here for my new wattmeter kits... specifically
the LP-200 dummy load/wattmeter. You can read about it at
www.telepostinc.com. It's like a DL1 on steroids. It includes a 30W
dummy load, with a variable speed fan option for 100W continuous rating.
It doesn't get nearly as hot as a DL1, even without the fan, but more to
the point, it's microprocessor controlled, has digital readout,
frequency and temperature compensation, and will accurately display
power from 1mW to 120W. It makes a great addition to any bench. I
started shipping these about a week ago.
I also have a handheld digital wattmeter (LP-300) for field use that
will work at QRPp thru 100W that's real slick and will be out in a few
weeks, and a high-end digital meter (LP-100) that will go on sale this
week, that is based on my cover article in the Jan/Feb QEX. One unique
feature of the LP-100 is the ability to display complex impedance, in
addition to lots of other professional features.
The LP-100 and LP-300 feature a nifty peak responding bargraph display
that will follow voice peaks, and display power and SWR simultaneously
in both analog and numeric form. The LP-300 can not only be used for
antenna tuning, but as a realtime monitor for field operating. It has a
battery life of 25-100 hours depending on type of battery and backlight
usage. It also has a 12v jack for external power. The LP-100 uses a
superfast PLED display, and has lots of unique features.
They're all kits, and cover a range of needs. There are links to all
three on the above webpage, as well as a link to a comparison matrix of
the three. I will be at Dayton with a booth showing these and more.
Larry N8LP
ww.telepostinc.com
Don Brown wrote:
Hi
I will throw my two cents worth. I agree with everything Don is saying here
however there are several other ways to get a reasonably accurate power out
measurement on a K2 or K2/100. The simplest and maybe least expensive is the
Elecraft DL1 dummy load kit. This dummy load will handle 20 watts and
includes a built in RF probe to measure the power out. You just connect a
voltmeter to the probe out test points and use the included graph to convert
the DC voltage to watts. Everyone building a K2 should have one of these
simple dummy loads/RF indicator kits for calibration and tune up.
Another method is to use the new Elecraft CP1 directional coupler/power pick
off. With it you can use a QRP watt meter like the OHR WM-2 to measure up to
100 watts. You connect the K2/100 to the CP1 and then out of the CP1 to a
dummy load that can handle 100 watts like the Tentec 300 watt load or the
OHR 100 watt load. Then the forward pick off from the CP1 goes to the WM-2
set on 1 watt if you built the CP1 for 20 db or the 100 mW range if you
built the CP1 for 30 db. The WM-2 will read 0-100 watts. If you don't have a
watt meter then you can do the same thing with a scope and a little math by
connecting the scope across the forward terminator resistor on the CP1. You
should be able to do the same with a RF probe and a DC voltmeter with the 20
db version of the CP1. The 30 DB version may have too low of output for the
30 DB version for use with a RF probe.
I also wrote an article several years ago on how to convert the OHR 100 watt
dummy load into a 100 watt Pi attenuator with a 20 db down output. This can
be used with a scope or QRP watt meter to measure 0-100 watts. I will repost
the instructions if anyone is interested.
Thanks
The other Don
Don Brown
KD5NDB
----- Original Message -----
From: "Don Wilhelm" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; <elecraft@mailman.qth.net>
Sent: Wednesday, February 22, 2006 6:42 PM
Subject: RE: [Elecraft] Re: K2 Power Callibration
John,
One must be careful not to zap the diode in the RF Probe - so measuring
directly across the dummy load is good only up to 20 watts or so. A
'scope
with a proper probe will handle the full 100 watts of the KPA100 easily.
Builders may not have a known good 'scope, and the RF Probe method must be
used with some intelligence - many folks do not know the accuracy of their
dummy load at the frequency of operation - and both the 'scope and RF
Probe
methods are highly dependent on knowing the accuracy of the dummy load -
it
must be entirely resistive for accurate results.
Yes, I feel that my 'scope and 1% 50 ohm dummy load (checked for both R
and
X on several antenna analyzers) will provide better than 5% accuracy for
any
wattmeter that I calibrate by that method. Of course, I can do a more
accurate job at 30 watts or lower because I can read the voltage
differences
on my 'scope face with greater precision (the 10 volts per division scale)
and at higher power, I end up at the 20 or 50 volts per division scale and
the interpolation becomes more coarse.
73,
Don W3FPR
Elecraft web page: http://www.elecraft.com
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
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: Elecraft@mailman.qth.net
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
