[Elecraft] Issue 12 re Astron Power Supply

Tue Apr 17 14:45:51 EDT 2018

Like all of the "12VDC"  rigs made today the IMD on the K3 is sensitive 
to input voltage.  I would recommend you get the input up into the 
14.8VDC range as it will reduce the IMD products.  I have mine such that 
on CW key down 100W the internal K3s voltmeter reads 14.5VDC which is 
basically the reverse protection diode drop from the 14.8VDC input.  I 
am using a TGElectronics battery booster with about 4 in cable from the 
battery booster to the K3s.

Dave K5MWR

On 4/17/2018 1:36 PM, Buck wrote:
> What is the minimum recommended voltage for the K3S?  Using the stock 
> Elecraft 5' cable, I drop from 13.3 to 12.7 volts on key down.
>
> Buck, k4ia
> Honor Roll
> 8BDXCC
> EasyWayHamBooks.com
>
> On 4/16/2018 4:51 PM, Joe Subich, W4TV wrote:
>> On 2018-04-16 4:26 PM, hawley, charles j jr wrote:
>>> So 4 sets of power pole connectors plus 2 fuses.
>>
>> Even if the power pole connectors are assembled perfectly and
>> mated with optimum tension, the resistance in just the four
>> (15 A) power pole connectors in the negative lead is equivalent
>> to nearly 40 feet of #12 copper wire!
>>
>>> The voltage at the rig, K3, now drops a volt when putting out 100
>>> Watts.
>>
>> With the equivalent of 50 feet of power cable (4 connectors plus a
>> 10 foot physical cable), I would not be surprised.  Assuming 20A
>> in transmit (on 15A power poles!), a 1V drop represents 0.05 Ohms
>> of total circuit losses .... that's pretty good for 10 feet (x2)
>> of cable plus eight connectors (4 in the + lead, 4 in the - lead)
>> and the switching device (probably a Schotkey diode).  However,
>> the 0.05 Ohms in the negative lead is probably ten times higher
>> than in a braided bonding connection directly from the K3 chassis
>> to the power supply chassis.
>>
>> I'm surprised that only 75% went through the ground path - that
>> indicates the ground path has 1/3 as much resistance as the "right"
>> (V- lead) path.
>>
>> 73,
>>
>>     ... Joe, W4TV
>>
>>
>> On 2018-04-16 4:26 PM, hawley, charles j jr wrote:
>>> About 75% went thru the ground path. The 10 ga to the rig went from 
>>> Astron to a battery switching device in case of power outage, to rig 
>>> runner and to rig. So 4 sets of power pole connectors plus 2 fuses. 
>>> I’m thinking of changing some of that too. The voltage at the rig, 
>>> K3, now drops a volt when putting out 100 Watts.
>>>
>>> Chuck Jack
>>> KE9UW
>>>
>>> Sent from my iPhone, cjack
>>>
>>>> On Apr 16, 2018, at 3:14 PM, Wes Stewart <wes_n7ws at triconet.org> 
>>>> wrote:
>>>>
>>>> I would hope that "much of the current..." wasn't really much.  The 
>>>> direct conductor from the negative terminal of the power supply to 
>>>> the radio should carry the majority of the supply current,
>>>>
>>>> Wes  N7WS
>>>>
>>>>>   On 4/15/2018 7:38 PM, hawley, charles j jr wrote:
>>>>> This thread prompted me to check out my Astron vs35m. It had a 
>>>>> small black wire from -V connected to the bottom of the chassis. 
>>>>> Perhaps it could be called a case or cabinet...more importantly, 
>>>>> it’s what the green wire from the line cord is connected to. I 
>>>>> disconnected the black wire. When it was connected, much of the 
>>>>> current that would have passed thru the negative power wire from 
>>>>> the power supply to the rig was shunted thru the green power cord 
>>>>> wire, the ground buss bar, and other ground connections.
>>>>>
>>>>> Chuck Jack
>>>>> KE9UW
>>>>>
>>>>
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