Posted by
David Dietrich on
Jan 11, 2012; 2:05am
URL: http://elecraft.85.s1.nabble.com/K2-power-out-accurate-tp7174240p7174601.html
Hi Don!
As always, thanks for the reply and info...Much appreciated. I am fairly confident of the Wattmeter's readings. It is an Oak Hills Research QRP Wattmeter. I spent a good 1/2 hour getting the correct readings for alignment with my DMM once the kit was finished. My dummy load is from Oak Hills Research as well, and I built it right around the time I built the Wattmeter this past spring. Again, when I made my final measurements with my DMM, I got a reading of 49.9 Ohms.
Concerning the Wattmeter, I checked power readings into the Wattmeter using the load with my other HF gear. My Norcal 40A was reading 3 W at key down, my Yaesu was reading within a Watt of the meter, and so was my ICOM. I checked my ICOM against my antenna tuner too, and it was almost spot on. However, I did notice that my K1 was only putting out 1 W per the meter at full drive, but that is an issue for another thread.
I was in CW mode when I was noticing this. My K2/10 has the KAT2 installed. I am just wondering if we did something wrong yesterday. We spent a good 3 hours on the procedure.
73,
David
KC9EHQ
________________________________
From: Don Wilhelm <
[hidden email]>
To: David Dietrich <
[hidden email]>
Cc: "
[hidden email]" <
[hidden email]>
Sent: Tuesday, January 10, 2012 6:03 PM
Subject: Re: [Elecraft] K2 power out accurate?
David,
Yes, I have several "ideas". First of all, how confident are you of your QRP wattmeter readings? Know that typical wattmeters can be in error by as much as 20% of full scale - if the full scale is 10 watts, that is a 2 watt potential error *anywhere* on the meter scale. Secondly, what is the actual impedance of your dummy load?
If your dummy load is a good 50 ohm resistive load, I would state that the K2 power indication is more accurate than any external wattmeter - OTOH, if the dummy load is not 50 ohms resistive (check with an antenna analyzer), then your readings can be "all over the map".
The base K2 power output reading is only accurate if you are driving a load that is 50+j0 - in other words, a perfect 50 ohm load. If one adds the KAT2 or the KAT100 or the KPA100, then that situation changes because those options add a real wattmeter - the basic K2 uses an RF voltage detector which is accurate, but only into a 50 ohm resistive load. In all my testing of the K2 (going on 7 years now), I have found that the K2 power indication is better than most wattmeters - given the condition that the dummy load is a good 50 ohm pure resistive load - in other words, a precision dummy load.
Sources of dummy loads meeting my requirements for measurement accuracy, try Ridge Equipment
https://www.ridgeequipment.com/store/index.html. They have dummy loads accurate enough for measurement purposes - many "dummy loads" are sufficient for providing a load on a transceiver, but may not be of "measurement quality".
73,
Don W3FPR
On 1/10/2012 6:23 PM, David Dietrich wrote:
> Hello All!
>
> My friend and I spent yesterday aligning my Norcal 40A and recently finished K2/10 #7164. We really did not play too much with the K2 after we finished aligning as we were also working on some other things in my shack.
>
> When I was starting to really get to know the ins and outs of the radio, I noticed that the power out indicated on the display when you adjust the power knob is much higher as indicated on my QRP Wattmeter. I set the radio to around 2.0 W, and the Wattmeter is showing around 5W. When I was at about 5-6 W, I pinned the needle on the Wattmeter. We followed the manual to a "T" and used a frequency counter, my Wattmeter, a 'scope, and signal generator to do the alignment.
>
> Any ideas?
>
> Thanks& 73,
>
> David
> KC9EHQ
>
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html