[600MRG] Amp

[Edward R Cole]

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
>_______________________________________________
>600MRG mailing list
>600MRG at w7ekb.com
>http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     dubususa at gmail.com