[Elecraft] Input vs. output power question

[Stephen W. Kercel]

Bekir:

The technical answer to your question is as follows. The loss of your 
coax depends on the SWR and frequency. 45 meters of CQ125 (a high 
quality version of RG-58) at 14 MHz with an SWR of 2:1 has an 
idealized loss of 2.7 dB. If you request 9.5 Watts on your K2, you 
would get close to 5 Watts at the antenna.

There is an excellent coax loss calculator at:

http://www.ocarc.ca/coax.htm

HOWEVER, please note N7XY's post. As with virtually all contests, the 
IARU contest counts QRP as 5 Watts at the transmitter output rather 
than the antenna input.

K2s tends to heat up a bit (with a consequent rise in power out) 
after the first few seconds of operation. I find that I need to set 
my requested power at 4.5 Watts to assure 5 watts after the first few 
characters on CW. Other list members tell me that this is typical 
behavior of normally functioning K2s.

Good luck in IARU. Perhaps I'll see you there.

73,

Steve Kercel
AA4AK



At 04:37 AM 7/6/2006, Bekir Kemal Ataman wrote:
>I intend to join the IARU HF contest in the QRP category (i.e. 5 
>watts output).
>
>I have got a RG58 going to my inverted V antenna. The coax is about 45
>meters in length (roughly 135 feet).
>
>How much power should I request from my K2 to get 5 watts output from the
>antenna?
>
>73!
>de TA2RX
>
>----------------------------------
>Bekir Kemal Ataman
>ArchiMac BBS Sysop & Webmaster <http://www.archimac.org/>
>
>
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