[Elecraft] [K2] Report on cheap power supply

[jerry]

All,

   Ebay is crawling with Netgear wall warts that are rated 12V 3.5A.
They are ideal for a K2.  The connector fits, too.  I got a couple of
them at the ham swap a few years ago.  Sold to me by Mark, the CTO
of Netgear.  He would show up at every flea market in his ancient
VW bus, selling detritus from the Netgear labs.

              - Jerry KF6VB






On 2021-12-28 08:19, Douglas Hagerman via Elecraft wrote:
> Santa Claus brought me a cheap 14 volt wall wart style power supply.
> The purpose of this is to charge the K2 built-in battery.
> 
> https://smile.amazon.com/PERFEIDY-Switching-Regulated-Transformer-Interchangeable/dp/B09DSCD62C/ref=sr_1_8?keywords=14+volt+wall+wart&qid=1638756395&sr=8-8
> <https://smile.amazon.com/PERFEIDY-Switching-Regulated-Transformer-Interchangeable/dp/B09DSCD62C/ref=sr_1_8?keywords=14+volt+wall+wart&qid=1638756395&sr=8-8>
> 
> The unit is made in China, and the cost is $16. The nameplate rating 
> is:
> Input: 100 - 240 V AC 50/60 Hz 1A
> Output: 14.0 V DC  1.0 A 14.0 W
> 
> The unit comes with a selection of connector adapters of various
> sizes, but the connector that is wired onto it is the right size for
> the K2 power socket.
> 
> Recall that the K2 receive current requirement is in the neighborhood
> of 120 - 250 mA, while the transmit current is 2.0 A or more, or
> potentially somewhat less if current limit is set. So this power
> supply is adequate for charging the battery, adequate for receiving,
> and inadequate for transmitting.
> 
> After the battery has been fully charged (overnight) with the 14.0
> volt power supply, the radio shows 13.8 V when the PS is connected,
> and 12.9 V with the PS is disconnected.
> 
> With the battery discharged so that it shows 10.0 volts with the PS
> disconnected, then when the PS is connected it shows 13.7 volts. This
> suggests that the PS is barely able to maintain its rated voltage
> output under a heavy charging load.
> 
> With the 14.0 V PS connected, I am not noticing any new noise when
> receiving with an antenna mounted outside my house. I have not tried
> transmitting.
> 
> A concern might be if the battery is fully charged using the 14 volt
> supply, and then a conventional 13.8 volt supply is accidentally
> connected with the battery turned on in the radio, then the voltage
> regulator of the conventional power supply might get confused.
> 
> This power supply seems to solve two problems:
> 
> 1.) Cheap, small portable power for battery charging when traveling.
> 2.) Higher voltage than conventional ham power supplies, which should
> help battery life.
> 
> Doug, W0UHU.
> 
> 
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