Re: K1 - KAT1 FD OCF dipole ...

[Mike Morrow-3]

Steve wrote:

>OK, I wanted to build a plug-n-play off-center-fed
>doublet for Field Day to match my K1 (40-30-20-17) /
>KAT1 / solar powered portable station....

>What say ye, fellow Elecrafters?  Should I just use a
>4:1 and eat the inefficiency?  (At battery QRP, I
>don't like that option and besides, the purist in me
>revolts against such technoblasphemy.)

>... kit my solar-powered K1 with a snazzy, efficient and
"matching" antenna?

Steve,

I guess my question is:  Why choose this type of antenna?  Baluns of any type especially warrant avoidance if losses are of concern.

For more than 30 years, portable HF operation has been my main interest in ham radio.  In that interval I've tried almost every conceivable type, home-made and commercial-made:  dipoles fed with coax, doublets fed with ladder line, verticals, loops, etc. (but no beams). I've found that absolutely nothing ever worked as well as the simple cheap light-weight coax-fed resonant half-wave dipole...nothing else even comes close.

For the four band K1, a 40m dipole with three insulators with jumpers spaced properly in each leg will produce a very compact, low-cost, resonant antenna for each K1 band.  No balun is needed at the antenna, and you'll have the coax feed you need.

For years I've used such an antenna, except that I have nine jumperable insulators in each leg and can, in just a couple of minutes, set the antenna for resonance on any HF band from 40m to 10m.

73,
Mike / KK5F
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Mike Morrow-3]

I wrote:

>For years I've used such an antenna, except that I have nine
>jumperable insulators in each leg...

Whoops, that should have been *six* insulators, not nine.

73,
Mike / KK5F
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[k6dgw]

Steve (et al): FWIW -- I have used a sloping Vee antenna for a number of
years on 30m and below with mixed results.  It is balanced, fed with 460
ohm "window" line.  The balun in my MFJ-989C got hot at QRO, and
bringing the open-wire line into the shack was a disaster at anything
over about 50W (keying the irrigation sprinkler valves was one of the
disasters)  I finally used EZNEC-4 and TLW (N6BV's nifty transmission
line program in the 20th ed. ARRL Antenna Book) to find leg and feedline
lengths that, with a 4:1 DX Engineering balun at the end of the
open-wire line, gave me acceptable SWR on the coax into the shack.  It
worked so well that I worked out a portable version for my K2 and KX1
with a smaller HB balun and the ATU's handle it just fine on all bands.
  The DXE balun is a 10KW current balun with insulation up to a 12KV or
more, and seems to be very efficient (and cold) even with a KW.

I really would stay away from any unbalanced antenna if you can (except
possibly the random end-fed wire with counterpoise radial I sometimes
use with my KX1 when I can't get the dipole up).

As I said, FWIW

Fred K6DGW
Auburn CA CM98lw

Mike Morrow wrote:
> I guess my question is:  Why choose this type of antenna?
> Baluns of any type especially warrant avoidance if losses
 > are of concern.


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Steve Jackson-5]

--- Mike Morrow <[hidden email]> wrote:

> I guess my question is:  Why choose this type of
> antenna?  

Our Field Day setup uncludes a 66' pneumatic bucket
truck.  The bucket holds up a central rope, and from
that is supported my dipole center.  

The bucket truck is set in place by the power company
at 9 AM on Saturday morning and is retracted only at
2:30 PM Sunday.  We can't operate the bucket.

> Baluns of any type especially warrant
> avoidance if losses are of concern.

Properly-constructed baluns are not lossy, provided
they have the right impedances on each side.

> For more than 30 years, portable HF operation has
> been my main interest in ham radio.  In that
> interval I've tried almost every conceivable type,
> home-made and commercial-made:  dipoles fed with
> coax, doublets fed with ladder line, verticals,
> loops, etc. (but no beams). I've found that
> absolutely nothing ever worked as well as the simple
> cheap light-weight coax-fed resonant half-wave
> dipole...nothing else even comes close.

I mostly concur.  With the obvious exception of beams,
as you say, monoband wire dipoles can't be beat -
except by monoband extended-double-Zepps (better
pattern), by coaxial double bazookas (better
bandwidth), and (in narrow bandwidths) by
exaggerated-wall magnetic loops (tolerant of low
mounting height).  That's why I use all four of these
antenna types, depending on the circumstances.

> For the four band K1, a 40m dipole with three
> insulators with jumpers spaced properly in each leg
> will produce a very compact, low-cost, resonant
> antenna for each K1 band.  No balun is needed at the
> antenna, and you'll have the coax feed you need.

That would be fine, if I wanted to (or could) raise
and lower the antenna.  

The OCF dipole is the best multiband compromise
antenna for my specific application, provided I can
make a good match to it.  

What will probably happen if I can't find a good
design for a 6:1 balun in time to make one ... I will
wind a 4:1 balun and feed it with RG-6, then null out
the slight mismatch at the rig using the ATU.  





               
__________________________________
Discover Yahoo!
Have fun online with music videos, cool games, IM and more. Check it out!
http://discover.yahoo.com/online.html
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Stuart Rohre]

Don't forget that 3/2 waves in phase doublets, give you gain and a multilobe
advantage for covering more of the country on Field Day.  Now I am not
talking the G5RV, but the W5GI with true in phase action along each side.

He also has the Vee beam without a in span phasing line, the D3 Plus.  Both
are on his web page, www.W5GI.com.  These can be fed with ladder line or 1/4
wave coax stub for one band use.

The 5/8 wave legs of my IDEZ design, (Inverted Double Extended Zepp) gives
you multi lobes and gain, but you have to have a lot of space, and one
support pole.  Just make the antenna of your favorite conduit wire 14 ga
insulated, in any color.   Each leg is 5/8 wave at lowest band, (160 or
80m).

Feed the center with 450 ohm ladder or 300 ohm line, and go to an external
current balun, then to coax output of your tuner with a one foot jumper or
double male coax plug.

Finally, for Field Day, a low Horizontal loop is easy up, if the legs are
individual wires joined at 3 corners with wire nuts.   Make this loop 2
waves on 40m, and it will have respectable gain like a beam on higher bands,
and 3 dB on 40.  It can be tuned to 80m as well.  It only has to be up 20
feet to have both high and low angle performance.  If oriented to have one
side to most of ham population center, you will cover the country well.
Feed it in the corner opposite the direction of most ham population, as the
lobe pattern favors the side opposite feed.  Again, 450 ohm ladder, or 300
ohm line feeder any length. (we had 150 feet last year).  Same deal,
external balun, on Tee tuner coax output.  4:1 Van Gorden baluns are
efficient and work well.

Stuart
K5KVH



_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com