K2 voltage requirement

[Vic K2VCO]

When operating a QRP K2 in the field with a battery, how low can the battery voltage go
before there are problems with signal quality?

Will it work down to 10.5v?
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[wayne burdick]

Vic K2VCO wrote:

> When operating a QRP K2 in the field with a battery, how low can the
> battery voltage go
> before there are problems with signal quality?
>
> Will it work down to 10.5v?

Hi Vic,

We designed the K2 with low-voltage field conditions in mind (after
all, we dreamed up the rig during field day, running a NorCal Sierra
from a nearly-dead Gel-cell). Both transmit and receive are stable down
to about 9 V, although maximum transmit power output will be reduced.

Here's a table from our transceiver performance comparison page. It
shows the recommended maximum power output setting vs. supply voltage
for the K2 (measured at the DC input jack in transmit mode).

DC VOLTAGE   POWER OUTPUT
    9.0 V         2.0 W
    9.5 V         5.0 W
   10.0 V        7.0 W
   10.5 V       10.0 W

The K3, too, works at lower voltages than other rigs in its class. We
spec the minimum at 11 V, but it will remain rock-stable down to about
9.5 V.

Both rigs will back down the transmit power at low voltages
automatically, if you forget to :)

73,
Wayne
N6KR

---

http://www.elecraft.com

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[Phil Kane-2]

On 5/12/2009 9:04 AM, Vic K2VCO wrote:

> When operating a QRP K2 in the field with a battery, how low can
> the battery voltage go before there are problems with signal
> quality?

> Will it work down to 10.5v?

  FWIW my experience with a K2/100 operating at 30-40 watts is
  that below 11.5V it goes sour.

  I had to arm-wrestle Trojan Battery to get ampere-hour
  discharge curves down to that level for my 27AGM batteries. The
  industry standard for ampere-hour discharge ratings is down to
  10.5V.  They finally admitted that the discharge capacity down
  to 11.5V is about 70% of the 10.5V rating.

  One of my professional colleagues is a national expert on
  battery supplies for communication sites and he concurs with
  that figure for that type of battery.

--  73 de K2ASP - Phil Kane
    Elecraft K2/100   s/n 5402

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