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Disone: The Return


#1

Thanks for all the useful suggestions and comments on discones and horizontal vhf. The discone idea has now been discarded.
I have made a fair few contacts on 2mts ssb and the majority of them were with my colinear, simply because it is all I have. Its worked ok so far, as overall I am in 32nd place for 2mt ssb contacts on the database. I would like to improve on that however!
However my xyl has been talking about moving since I started this thread and the likely qth, though only a couple of miles from the current location, is on the floor of a shallow valley. Vhf might not do very well at all. The upside is lots of space for HF aerials.
The turnstile idea is interesting although I can’t find any homebrew instructions on line or a commercial version. Anyone any ideas? It may be that a halo and/or a dipole might well be a simple and inexpensive temporary solution.
Cheers
Q


#2

In reply to GW3BV:

Take a look at

http://www.open-circuit.co.uk/turns.php

and the link to L.B. Cebik’s site

Regards, Mike G4BLH


#3

In reply to GW3BV:
Page 16.33 Radio Communications Handbook

page 7.26 VHF/UHF Manual

Can copy if you send me an e-mail address Q

g4owg@eu.srars.org

Roger G4OWG


#4

Thanks Roger, its also on 14.53 of the Handbook 7th edition which is sat on the shelf next to me…ahem.
Having said that Mike’s link is a little easier to follow for the intellectually challenged, like me!
Cheers
Q


#5

Being the lazy type, well thats not quite true its a time thing, is there anywhere I can buy one or is there a kit out there anyone knows of.
I can see that being a good SOTA antenna in the winter.


#6

Hi Quentin,

Like you, I’ve never seen dimensions for a turnstile, so many thanks
to Mike for the link. I think that the best thing to come out from
all the postings has been the wealth of information shared. What is
clear is that for horizontal operation, any omnidirectional horizontal
antenna will outperform a vertical, bearing in mind that the cross
polarisation loss, as Brian says, will be in the region of 20 to 30dB,
whilst the gain on even the best colinear will only be a fraction of
this. Good luck, and I look forward to trying one of these turnstiles
myself.

Kind regards

73
Dave G0ELJ


#7

In reply to 2E0KPO:

I built one for loft use many years ago using copper plated welding rods and a pair of chocolate blocks, bending the end of the rods over by about a centimetre to go into the blocks and the coax going into the other end of the blocks, the blocks being screwed into a broomstick. It took about an hour to build.

73

Brian G8ADD


#8

In reply to GW3BV:

Try these:

http://www.west.net/~jay/turnstile.html
http://www.wb8erj.com/turnstile_antenna.htm
http://www.cebik.com/wire/turns.html
http://www.ssbusa.com/wimowheel.html
http://www.rmvhf.org/wheelantenna.html

Andy
MM0FMF


#9

In reply to GW3BV:

I’ve just thought of another omni-directional horizontally polarised antenna from times past: does anyone remember the Omni-V? I remember that it was marketed but can’t remember who by: possibly the very much missed J-beams?

As I remember it, it was a pair of dipoles phased together with open lines tapped to match the coax, bidirectional with the dipoles straight and omnidirectional with the dipoles set in a horizontal “V”. I seem to remember it was superior to a single turnstile but inferior to a stacked pair of turnstiles.

73

Brian G8ADD

PS just had a thought and checked my Handbook (6th edition) and found a drawing on page 13.36


#10

In reply to GW3BV:

Hi Q

I think that under the circumstances, with your imminent move, the simplest and easiest to build/erect option is the turnstile, which is basically just a pair of crossed dipoles fed with a coaxial phasing harness.
It is inconspicuous in appearance and would offer an improvement over your colinear for horizontal contacts.
Good luck with the move Q, can you erect a horizontal beam/rotator at the proposed new QTH?

73 Mike GW0DSP


#11

In reply to GW0DSP:

Another alternative if your into experimentation is the 0.8 wavelength constant current loop (or uniform current loop).

Robert Zimmerman wrote about them in QEX and Antennex sometime ago, they are also described on Cebik’s site http://www.cebik.com/ao/ao16.html.

Zimmerman made one from 300 ohm twinfeeder.

It is omnidirectional, has a 50 ohm feedpoint with no matching and better gain than a 0.5 wl halo. Virtually zero radiation straight up.

I have built/used them and think they are worth exploring.

I think you can probably nest them for different bands as they are tuned loops.

Regards,
Nigel. G6SFP.