Someone asked me how this antenna worked after I had built the Q section
from two pieces of 50r coax side by side, using the centre conductors as
an open wire feeder equivalent. The shields being joined at each end but
nowhere else.. (There should be grounded at the bottom end and at some
neutral point at the top - if any)

The antenna is a almost equilateral triangular shaped single quad loop
with base/feed about 4 metres off the ground. The "almost" being the
horizontal/top section is about 8 metres in length.

Well it works! I dont have enough of a power supply at the moment for
doing any extensive on air tests. VSWR was 1.4:1 without much excursion
at the band edges. This is what 4NEC2 said it would be. In fact I didnt
have to cut it after following the modelled dimensions. It was
surprisingly wide band I guess from the higher feed Z (rather than using
a single 75r section)

I have only just moved here and there is a lot of noise about at various
times of the day. (S7-9) I have heard stations across the US and maybe
some Spanish speaking. Waiting for a PSU to arrive so I can try a little
harder.

I didnt notice any VSWR changes or a change in feedline radiation
(through PC/stereo spkrs etc) by coiling the coax at the base of the Q
section. Indeed I did it because I was at risk getting tangled in the
coax going to the trash can!

I expect high radiation angles BTW.

Cheers Bob W5/VK2YQA East Texas.

"Bob Bob" wrote in message
...
Someone asked me how this antenna worked after I had built the Q
section
from two pieces of 50r coax side by side, using the centre
conductors as
an open wire feeder equivalent. The shields being joined at each end
but
nowhere else.. (There should be grounded at the bottom end and at
some
neutral point at the top - if any)

The antenna is a almost equilateral triangular shaped single quad
loop
with base/feed about 4 metres off the ground. The "almost" being the
horizontal/top section is about 8 metres in length.

Well it works! I dont have enough of a power supply at the moment
for
doing any extensive on air tests. VSWR was 1.4:1 without much
excursion
at the band edges. This is what 4NEC2 said it would be. In fact I
didnt
have to cut it after following the modelled dimensions. It was
surprisingly wide band I guess from the higher feed Z (rather than
using
a single 75r section)

I have only just moved here and there is a lot of noise about at
various
times of the day. (S7-9) I have heard stations across the US and
maybe
some Spanish speaking. Waiting for a PSU to arrive so I can try a
little
harder.

I didnt notice any VSWR changes or a change in feedline radiation
(through PC/stereo spkrs etc) by coiling the coax at the base of the
Q
section. Indeed I did it because I was at risk getting tangled in
the
coax going to the trash can!

I expect high radiation angles BTW.

Cheers Bob W5/VK2YQA East Texas.

===============================

Bob, what is the purpose of the coaxial outer conductors which are not
connected to anything.except to each other?
----
Reg.

Hi Reg

The two pieces of coax are only meant to be a 100 ohm balanced Q section
to translate the antenna Z to close to that of the main feedline (50r).
I could do the same if I had some 100r open/ribbon feedline.

The outer conductors/shield should be at zero potential and as such
preserve the Z between the two inner conductors. This is handy in that
the coaxes dont have to be bound close together and could be fed through
a non metallic conduit without problems.

Have I made any sense?

Cheers Bob

Reg Edwards wrote:

===============================

Bob, what is the purpose of the coaxial outer conductors which are not
connected to anything.except to each other?
----
Reg.

"Bob Bob" wrote in message
...
Hi Reg

The two pieces of coax are only meant to be a 100 ohm balanced Q
section
to translate the antenna Z to close to that of the main feedline
(50r).
I could do the same if I had some 100r open/ribbon feedline.

The outer conductors/shield should be at zero potential and as such
preserve the Z between the two inner conductors. This is handy in
that
the coaxes dont have to be bound close together and could be fed
through
a non metallic conduit without problems.

Have I made any sense?

Yes, that works OK. You have acheived your objective.

My only comment is that the inner coaxial conductors are very thin and
depending on length they may be a little lossy. You could use a
twisted pair of thicker wires insulated with thin plastic which would
have approximately the same 100-ohm impedance. The actual impedance is
not very critical.

This would also eliminate stray capacitance of the coax outer
conductors to their surroundings. Although that is not likely to
cause much trouble anyway.
----
Reg.

Mmm okay, well considering the rest of the feedline is RG58 I guess the
matching section has less loss per unit length! grin (The Q section is
3 point something metres long - 1/4 wave at 0.66 vf)

I havent been playing with HF that long. I must admit though that I tend
to ignore the losses that I would worry a lot about at VHF/UHF.

Oh BTW I tried one of your pgms under Linux Wine the other day. Dies
with some kind of DOS memory alloc error or something. I'll make a note
of it next time and do a little research if your interested.

Cheers Bob

Reg Edwards wrote:

Yes, that works OK. You have acheived your objective.

My only comment is that the inner coaxial conductors are very thin and
depending on length they may be a little lossy. You could use a
twisted pair of thicker wires insulated with thin plastic which would
have approximately the same 100-ohm impedance. The actual impedance is
not very critical.

This would also eliminate stray capacitance of the coax outer
conductors to their surroundings. Although that is not likely to
cause much trouble anyway.
----
Reg.

"Bob Bob" wrote in message
...
Mmm okay, well considering the rest of the feedline is RG58 I guess
the
matching section has less loss per unit length! grin (The Q
section is
3 point something metres long - 1/4 wave at 0.66 vf)

I havent been playing with HF that long. I must admit though that I
tend
to ignore the losses that I would worry a lot about at VHF/UHF.

Oh BTW I tried one of your pgms under Linux Wine the other day. Dies
with some kind of DOS memory alloc error or something. I'll make a
note
of it next time and do a little research if your interested.

Cheers Bob

Reg Edwards wrote:

Yes, that works OK. You have acheived your objective.

My only comment is that the inner coaxial conductors are very thin
and
depending on length they may be a little lossy. You could use a
twisted pair of thicker wires insulated with thin plastic which
would
have approximately the same 100-ohm impedance. The actual
impedance is
not very critical.

This would also eliminate stray capacitance of the coax outer
conductors to their surroundings. Although that is not likely to
cause much trouble anyway.

==========================================

Regarding Linux.

There's little or nothing you can do about it. And I'm afraid, sooner
or later, future versions of Dos/Windows may not be able to run my
programs.

Just don't throw away your old computer. ;o)
---
Reg, G4FGQ

On Mon, 03 Oct 2005 19:17:36 -0500,
Bob Bob wrote:
Mmm okay, well considering the rest of the feedline is RG58 I guess the
matching section has less loss per unit length! grin (The Q section is
3 point something metres long - 1/4 wave at 0.66 vf)

I havent been playing with HF that long. I must admit though that I tend
to ignore the losses that I would worry a lot about at VHF/UHF.

Oh BTW I tried one of your pgms under Linux Wine the other day. Dies
with some kind of DOS memory alloc error or something. I'll make a note
of it next time and do a little research if your interested.

Cheers Bob



try dosemu instead. Wine won't work well with programs that try to
directly access memory via INTs and such.

http://www.dosemu.org/

Also, there's freedos, but I haven't used that seriously.

--
Jim Richardson http://www.eskimo.com/~warlock
Step by step, day by day, machine by machine, the penguins march forward.

Hi Jim

I actually had a quick look at that for trying to run Ari's 4NEC2 under
Linux. Since it calls the DOS shell to run the calc I was hopeful. Cant
remember if it worked but was more concerned about how to call it from
the GUI under Wine. (ie how to call a Linux pgm from a W32 pgm running
under wine!)

I tend to use my wife's W98 machine when I need to model things (shame
on me!)

Many tnxs for your feedback.

Cheers Bob

Jim Richardson wrote:


try dosemu instead. Wine won't work well with programs that try to
directly access memory via INTs and such.