JGBOYLES wrote:
As to this particular project, I've received several interesting
suggestions, some modifying the shape/size, some adding a tuner at the
base. I'm probably gonna try both. I have a line on an extra tuner,
which I'm gonna try to weatherproof and install (single band)

Dan, I homebrewed a remote controlled tuner that would work with your antenna,
and you could change bands without ever leaving the shack. It uses a motor
driven roller inductor and variable capacitor in an "L" network. I also have a
relay switching scheme to reconfigure the "L" network. With this tuner at the
base of a vertical or inv. L you can match a wide range of impedances. The L
and C in this tuner are rated at legal limit.
Obviously the only thing standing in the way of you using something like this
is obtaining the parts and building it. The inductor is surplus, about 30 uH.
MFJ sells one that they use in their 1 kw tuner, around $65. The capacitor is
a Ten Tec 500pf variable cap. kit, around $45. The drive motors came out of a
kids battery operated car, 12vdc around .5 to 1 revs/sec that can be changed
with the supply voltage. The hard part is coupling the motors to the L and C.
The control cable is 100' of 8 cond.#20 shielded industrial control cable,
about $45. Forward and reversing was done with relay logic.
This was not a weekend project, but it wasn't that bad either. If you want
some more details, email.

A few more thoughts, in case they're useful to Dan or anyone else:

* It's sometimes possible to make an automatic two-band network. For
example, the same 33ft end-fed vertical can be matched as both a
half-wave on 20m *and* a quarter-wave on 40m, with one network and no
switching. The same goes for a 66-footer (vertical or inverted L) on
40/20, or a 130-footer on 160/80.

* Remember that the remote network doesn't have to give a perfect match.
If the SWR on the coax is below about 3, the extra losses won't be
significant (except in extreme cases) and you can always do the final
"flattening" to 50R in the shack.

* Instead of remote rotary switches, consider latching vacuum relays
which don't require power to hold them closed. There are surplus vac
relays at very reasonable prices at:
http://www.mgs4u.com/#president

* You can reduce the number of control lines by sending cunning
combinations of positive and negative DC, AC out from the control box,
and using steering/blocking/rectifying diodes at the remote end.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Ian White, G3SEK wrote:

A few more thoughts, in case they're useful to Dan or anyone else:

* It's sometimes possible to make an automatic two-band network. For
example, the same 33ft end-fed vertical can be matched as both a
half-wave on 20m *and* a quarter-wave on 40m, with one network and no
switching. The same goes for a 66-footer (vertical or inverted L) on
40/20, or a 130-footer on 160/80.
. . .

Wes Hayward, W7ZOI, published either a QST article or a Technical
Correspondence piece about doing this, many (10? 15?) years ago. A
search of the QST CDs should turn it up. If I recall correctly, he
concluded that either a two-band solution could always be found, or that
he wasn't able to find a combination that he couldn't find a two-band
solution for.

Just by observing this newsgroup, though, it seems like very few hams
are any longer interested in matching an antenna to a feedline,
preferring to buy ladder line and a tuner instead.

Roy Lewallen, W7EL

On Wed, 30 Jul 2003 07:15:30 +0100, "Ian White, G3SEK"
wrote:

Excellent suggestions, Ian...I sure like the K.I.S.S. method! Gonna
try the dual band approach with a tuner and mybe try some stubs. (I
also liked the homebrew remote tuner using the kids' car
motors....perhaps one day when my projects to-do list drops to the
single digits!)
73
dan (k0dan)

A few more thoughts, in case they're useful to Dan or anyone else:

* It's sometimes possible to make an automatic two-band network. For
example, the same 33ft end-fed vertical can be matched as both a
half-wave on 20m *and* a quarter-wave on 40m, with one network and no
switching. The same goes for a 66-footer (vertical or inverted L) on
40/20, or a 130-footer on 160/80.

* Remember that the remote network doesn't have to give a perfect match.
If the SWR on the coax is below about 3, the extra losses won't be
significant (except in extreme cases) and you can always do the final
"flattening" to 50R in the shack.

* Instead of remote rotary switches, consider latching vacuum relays
which don't require power to hold them closed. There are surplus vac
relays at very reasonable prices at:
http://www.mgs4u.com/#president

* You can reduce the number of control lines by sending cunning
combinations of positive and negative DC, AC out from the control box,
and using steering/blocking/rectifying diodes at the remote end.

JGBOYLES wrote:
A few years back, I reduced the number of control lines to zero with a wireless
link.

When I was at Texas A&M, I did a Mother's Day experiment where I had six
switches, seven wires, and six lamps. Each switch would light a different
individual lamp. I could disconnect the wires one by one and still light
the correct lamps. When it got down to lighting the lamps over one wire,
you would be surprised at how many engineering students couldn't figure
out how it was done. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote:
Ian White, G3SEK wrote:
A few more thoughts, in case they're useful to Dan or anyone else:
* It's sometimes possible to make an automatic two-band network. For
example, the same 33ft end-fed vertical can be matched as both a
half-wave on 20m *and* a quarter-wave on 40m, with one network and no
switching. The same goes for a 66-footer (vertical or inverted L) on
40/20, or a 130-footer on 160/80.
. . .

Wes Hayward, W7ZOI, published either a QST article or a Technical
Correspondence piece about doing this, many (10? 15?) years ago. A
search of the QST CDs should turn it up.

Yes, that's the one.

I possibly have a photocopy somewhere, but don't recall seeing these
extra details, which Roy may have hard directly from Wes:

If I recall correctly, he concluded that either a two-band solution
could always be found, or that he wasn't able to find a combination
that he couldn't find a two-band solution for.



Just by observing this newsgroup, though, it seems like very few hams
are any longer interested in matching an antenna to a feedline,
preferring to buy ladder line and a tuner instead.

If anybody's interested in this "two bands, one coax, no switches"
solution, I'll try to put a PDF together over the weekend (it isn't a
good subject for ASCII art). It also struck me that this may be a good
subject for an Excel spreadsheet, or one of Reg's programs.



--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

If anybody's interested in this "two bands, one coax, no switches"
solution, I'll try to put a PDF together over the weekend (it isn't a
good subject for ASCII art). It also struck me that this may be a good
subject for an Excel spreadsheet, or one of Reg's programs.

Ian, count me in. While "all band" operation is always desirable, when
you get right down to it 160/80 or 80/40 are the gaps I'm really
trying to fill. And while many of the other solutions proposed are
innovative and tempting to perform, the "keep it simple" approach has
very strong appeal.
Tnx & 73
Dan (K0DAN)