[Elecraft] Power calcs and simple charging mod

[Paul Webb]

HI all

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I have just about finished upgrading my K1 now (4 band module and =
backlight)

The current drain is about 65-75mA ,depending on volume setting about =
70mA
for normal listening.

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I have fitted 2400mA cells that just fit .

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I have checked the current drain at 4 watts from these cells and it =
seems
about 1000mA (1Amp)

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So I have worked the following out but would just like a check done=20

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Irx =3D 60

Itx=3D1000

Tx duty cycle 50% (since CW)

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Ratio tx/rx  25%

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So in one hour I would be in tx mode for 15mins drawing 1000mA but since
it=92s at 50% duty that=92s 500mA for 15mins

Which works out to 250mA for 30 mins or 125mA for 1 hr

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Plus the rx drain of say 70mA so that=92s 70mA/Hrs

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Total drain then is 125+70=3D195mA/Hr

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Since I have 2400mA/Hr cells that=92s 2400/195=3D12.3Hrs use

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That just seems at lot of use at 25% tx/rx ratio and with 4 watts output
power but it seems right to me., anyone confirm ?

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One more little mod I have done to the K1 (which I know I will be shot =
down
in flames for !)

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I wanted the cells in the K1 to be kept topped up ready for action so I
found a pin on the on/off switch that only gives 12volts out when the =
switch
is in the OFF position

>From this pin I took a feed to the cells via a 1amp diode and series
resistor to limit the current to about 25mA on a fully charged pack and
about 50-60mA on a flat pack.

This only supplies charge to the cells when the k1 is connected to =
external
power and turned off ,so if using the K1 in the field off a gel pack or

 the like it does don=92t add extra drain to the pack when the radio is =
turned
on , when the radio is turned off if you want to save any drain to the =
pack
just unplug it!

It works for me.

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All the best

Paul

M0BMN

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