[Elecraft] FW: [K3] K3 Off Grid

[WILLIS COOKE]

Most Engineers including me like lots of meters and we have the voltage and current instantaneous meters on our power supplies.  The metering on the K3 is redundant with the meters on the power supply.  A 50% duty cycle on transmit is way too much current.  Holding your key down 50% of the time will not make you very popular and will not yield a good fist.  About 30 to 35 % duty is a pretty good fist but you need to listen almost half the time if you are an excellent CW operator sending CQ and not getting any pile ups, so your duty cycle will vary from the hunt and pounce operator with less than 5% to the contest operator who holds a frequency and has a good answer rate which will have a duty cycle of maybe 15%.  A good contest operator will need several rotors and a 1500 watt (or more) amp which are hardly candidates for battery power.  So if you assume no rotary antenna and low power, you are good for a 48 hour contest with a good deep cycle
 battery starting at full charge.  Do you have a good battery with full charge?  That is entirely a different matter!
 
Willis 'Cookie' Cooke, TDXS DX Chairman
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart


________________________________
 From: Chester Alderman <aldermant at windstream.net>
To: elecraft at mailman.qth.net 
Sent: Wednesday, March 5, 2014 4:47 PM
Subject: [Elecraft] FW:  [K3] K3 Off Grid
 

Gosh Engineers...why not just suggest to Paul that he use the most simple
method of finding out the voltage and current the K3 draws by pressing the
K3's METER button????

73,
Tom - W4BQF



-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Lynn W. Taylor,
WB6UUT
Sent: Wednesday, March 5, 2014 5:23 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] [K3] K3 Off Grid

Here is how I'd do it, your mileage may vary.

I'd measure the power draw at 100 watts key-down, and the power draw for
receive.

I'd assume 50% duty cycle.  You can skip a lot of math by either ignoring
the receive power draw (if it's low enough) and dividing by two, or adding
them together and dividing by two (averaging them together).

Multiply that number by the number of hours you need to be able to operate
-- and that's your target capacity in amp-hours.

That should over estimate the battery, so if that size wasn't economical,
I'd buy one slightly smaller.

That should insure that the battery does the job for years, even when it's
starting to fail.  It should also make sure you can keep operating if the
emergency was longer than initially planned.

Yes, there are a lot of factors, like operating mode that this appears to
ignore.  I'm simply assuming things like full power or nothing when the
operator might be running SSB or PSK-31 at 20 watts.

I'm also ignoring portability, which I would not do if I was operating for
fun.

73 -- Lynn

On 3/5/2014 1:15 PM, Steve Baum wrote:
> There are so many things to consider when you try to calculate battery 
> requirements for emergency operation, is it really possible to 
> accurately predict how long a given battery will last?

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html