[600MRG] Amp

[John Langridge]

>Linear is needed for CW

Linear is NOT required for CW.. only when amplitude and/phase varies is
linear required.  It would be needed for PSK, which has been rarely used in
the last few years.

73!

John XIQ

On Sun, Aug 2, 2015 at 11:25 PM, Edward R Cole <kl7uw at acsalaska.net> wrote:

> Jim, and all:
>
> The K3 can be upgraded to operate down as low as 100-KHz by upgrading the
> Synth board for $219.95.  Reception is improved by a minor change in the
> General Coverage band filter and one component on the main board.
>
> So it is capable at this time by incorporating those changes.  Elecraft
> has just rolled out a new model called the K3S which comes standard with
> these.
>
> 100w seems a good target for 5w ERP (depends on your antenna efficiency).
>
> I think one should just figure on using a linear amp.  Linear is needed
> for CW and psk modes and gain is not difficult to achieve at 500-KHz.  I
> would guess 60-65% efficiency in the high power stage so you need
> dissipation of say 50% of RF output as a minimum to have a safe margin.
> 100w dissipation would ensure almost bullet proof running of any mode.
>
> Not sure you saw my recent post on the Elecraft reflector regarding 630m
> amplifiers?  I will be looking at making up a 100w linear amp that runs
> with 1mw drive sometime this winter when outdoor stuff is not as nice to
> do.  I am giving thought to offering it as a kit or partial-kit for sale.
> I was once considering transverters but others have beat me to that and
> with the K3 and TS590S both able to run 630m an amplifier is the needed
> item (probably a preamp too).
>
> Don't ask for particulars at this point - just an idea that needs some
> research and building a proof of concept.  No idea of cost.  Most likely
> will use FETs and run with 13.6v for simplicity, though 28v and 50v
> transistor specs are better.  Driving with 1mw makes such an amp usable
> with simple mixer schemes, as well.
>
> I discussed this with Wayne-N6KR of Elecraft and the market is too small
> for them to consider making an amp.
>
> 73, Ed - KL7UW
> http://www.kl7uw.com/kits.htm
>
> At 05:10 PM 8/2/2015, Jim Miller wrote:
>
>> Now that the K3 is getting closer to being a 630 capable machine and the
>> FCC is lumbering toward a band decision I'm thinking more about an amp.
>> I'm
>> assuming the market is too small for an Elecraft offering.
>>
>> The K3 puts out 1mW on the transverter output. I'm assuming that I'll need
>> 50-100w to get to 5w ERP.
>>
>> Assuming 100w for a minute and assuming 10-15db for the final amp stage
>> then you only need 5-10w before then. That should mean that even with poor
>> efficiency not a lot of power will be dissipated until the finals. That
>> means that I could keep the chain to that point linear and make the output
>> stage decision based on what modes are most prevalent.
>>
>> I assume CW for historical reasons and JTXX for practical reasons, WSPR as
>> well. Not sure about PSK or other modes which would require a more linear
>> final.
>>
>> So I could build a 1mW to 10W linear then wait and see about the finals.
>>
>> Thoughts?
>>
>> 73
>>
>> jim ab3cv
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>
> 73, Ed - KL7UW
> http://www.kl7uw.com
>     "Kits made by KL7UW"
> Dubus Mag business:
>     dubususa at gmail.com
>
>
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