[Elecraft] [KPA500] Low Power Use Cases

[Ralf Wilhelm]

Hi Frank,

I would not expect the waterfalls for the JT modes to change because the JT modes transmit only one tone at a time. Apart from turning the tx on and off, the amplitude of the signal does not change. Therfore there is no source for IMD that could result in a broader signal or splatter. You could even use a class C amplifier like you could for a fm transmitter.

Greetings

Ralf, DL6OAP

Am 19.07.2013 um 00:55 schrieb Frank Precissi <vadept at gmail.com>:

> I think the best solution would be to try it both ways and see what kind of
> signal report you get.  I'd be interested to see the two JT waterfalls
> compared side by side.
> 
> 73,
> 
> Frank KG6EYC
> 
> 
> On Thu, Jul 18, 2013 at 3:47 PM, Ron D'Eau Claire <ron at cobi.biz> wrote:
> 
>> I think it's a good question, but I cannot answer it.
>> 
>> Most amps produce more distortion the more power they run.
>> 
>> The question is whether the sum of distortion from both amps at lower power
>> is less than one amp running at higher power.
>> 
>> 73, Ron AC7AC
>> 
>> -----Original Message-----
>> 
>> 
>> On 7/18/2013 3:08 PM, Chris Johnson wrote:
>>> I love my KPA500.  I don't use it enough because of all the low power
>>> digital I do.   I was wondering if the quality of my signal would
>>> better if I let the KPA500 produce the output even if the wattage is
>>> 50 or less watts.   If I drive it with 1 to 5 watts, it produces 10
>>> to 50 watts.   I like the thought of offloading the thermal load of
>>> my long JT65 & JT9 duty cycles onto the KPA rather than my main rig
>>> which is a Flex 6700.
>> 
>> You're likely to stimulate more replies than the "Why is aeronautical VHF
>> comm still AM?" did. :-)
>> 
>> I don't know anything about a Flex <anything> but, all amplifiers have
>> non-zero distortion figures.  Putting two "in series" will add up at least
>> some if not all of them.  The amp in your Flex followed by the
>> KPA500 will most likely produce a poorer signal quality than just your Flex
>> for the same power output.
>> 
>> Secondly, the KPA500 was designed to produce several hundred watts with a
>> few tens of watts drive [500W on any band for me takes between 25 and
>> 30 watts drive].  That's probably the optimum operating point.  Driving it
>> with 5 watts should produce somewhere in the 50+ watts output range.
>> 
>> 73,
>> 
>> Fred K6DGW
>> - Northern California Contest Club
>> - CU in the 2013 Cal QSO Party 5-6 Oct 2013
>> - www.cqp.org
>> 
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> 
> 
> 
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