[Elecraft] Home made Sigma-GT5 & KRC2 or SGC?

[Mike McCoy]

> The Force 12 Sigma-GT5 looks interesting, but I would like to cover 30 and
> 40 meters. It should be possible to make a matching network similar to the
> Sigma-GT5 for either the Sigma 40 or 40XK.

Unlike the GT5 band changes on the 40XK are done manually with different
T-bar lengths (and coils added for 40/30) specifically per band.  If the
T-bars were adjusted/set 'permanently' for 20-10 (ala GT5) the only
difference would be switching the coils in/out for 40/30.  I don't think
that is the case because it would then be very easy for Force12 to simply
offer a '40-10 Sigma 5'.  Thus it would probably be easier to get the Sigma
40 (T-bars at one permanent length) to work on 40-10 thru an appropriate
matching network being switched in/out.

Way outta my league here 'antenna theory-wise' but given the popularity of
the Sigma series I bet if it were possible Force12 would have already done
it, designed a 40-10 'Sigma GT5'.  Not to say they aren't (hopefully)
working on it though.

Let me know if you figure it out, build a '40-10 GT-5 adapter' for the Sigma
40/40XP. I'll buy one from you HI

>The KRC2 Band Decoder could
> switch the relays. .

hmmm... now you got me thinking. Sometimes I end up slapping my forehead
because I forget to change the GT-5's little rotary (band)switch.  The KRC2
would be way overkill for just being inattentive but it would certainly
solve that problem ;)

>
> Also, is there anything about the Force 12 Sigma antennas that would be
> difficult to fabricate at home?

When I initially received my GT5 I was pretty disappointed ('I paid that
much for this?!?!'). But in actual use I grew to really appreciate its
efficiency/performance. For something so small it really gets out.

I'm sure fabrication wouldn't be the issue... nothing really exotic in its
materials/construction... it's the design behind it (and resulting
performance) that you pay for and thus would be the challenge to duplicate.

>
> I am also considering a BigIR 40m to 6m vertical, but I really do not have
> room for many radials. How will a BigIR with minimal radials compare to
the
> vertical dipole?

I know it's just me being paranoid but I can't shake the feeling there is
just too much going on mechanically inside the Fluidmotion antennas... Stuff
like that wears out over the long haul and Murphy always seems to be in the
wings around here ;)

In my particular situation I am becoming a big fan of vertical dipoles
because they are small footprint, don't require radials yet still provide a
low takeoff.  Really a big plus for me since I don't have the room or
ability to orient slopers, plant radials, much less put up a tower/beam for
DX.  If you're interested in a multi-band (80-10) vertical dipole check this
out:

http://www.titanex.de/frames/vertdipoles.html

73,
Mike K5PU