[Elecraft] [K2] Report on cheap power supply

[Frank Krozel]

I was under the impression that we set the K2 for 3.5Amps under the initialization, so maybe a 4amp supply like the one made by Pro Audio Engineering??

-73-  Frank    KG9H
kg9hfrank at gmail.com




> On Dec 28, 2021, at 11:06 AM, jerry <jerry at tr2.com> wrote:
> 
> 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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