[Elecraft] kpa1500?

[Joe Subich, W4TV]

> Just what the world needs...another dirty 13.8v...oops 12vdc mobile
> amp.

They don't need to be dirty ... the problem is that it takes so many
"pills" to make the power that designers tend to use the 60, 80 or
100W rated transistors right up to their saturated output rather than
limit each pair of devices to 50 - 60% of PEP output.  For example ...
the MRF-421 is rated as a 100W transistor but third  order IMD is
minimized around 50-55W.  An "eight pill" design could make 900W in
saturated mode but in order to keep it clean, the output would need to
kept to 500 W PEP.  This, in spite of the fact than Communications
Concepts sells a 2 x MRF-421 board set as a "180 Watt HF amplifier"
(Motorola AN-762).

73,

    ... Joe, W4TV


On 2014-12-13 10:29 AM, Gary Gregory wrote:
> Gee whizz
>
> Just what the world needs...another dirty 13.8v...oops 12vdc mobile amp.
>
> Why do folks need to run so much power mobile?...oh yeah, i forgot....silly
> me.
>
> Gary
> Vk1ZZ
> K3, KX3, KPA500-FT, KAT500-FT,P3.
> On 14/12/2014 1:02 AM, "Joe Subich, W4TV" <lists at subich.com> wrote:
>
>>
>>
>> On 2014-12-13 9:31 AM, Dan Baker wrote:
>>
>>> My feature request is for a 500 W mobile version of the KPA500.
>>>
>>
>> That's difficult due to the 12V requirement.  To do it right using 12V
>> capable transistors/FETS would take at least two and probably four
>> amplifier boards similar to the KPA500 with associated splitters and
>> combiners.  *Without tuner and power supply* would put the price
>> somewhere north of the KPA-500 just because of all the controls, heat
>> sinks, etc.  There is a reason that 12V capable transceivers do not
>> run more than 100W output (typically 2 x 60W or 2 x 80W transistors
>> in push-pull).
>>
>> 73,
>>
>>    ... Joe, W4TV
>>
>>
>> On 2014-12-13 9:31 AM, Dan Baker wrote:
>>
>>> My feature request is for a 500 W mobile version of the KPA500. I think
>>> the Mississippi company is the only one making a 500 watt mobile amp now.
>>> Seems like there is an opportunity to be had. I would gladly donate my
>>> ALS-500 to Wayne and Eric so they could see how not to build one.
>>>
>>> Dan KM6CQ
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>