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G8MNY > TECH 17.01.11 08:54l 149 Lines 5293 Bytes #999 (0) @ WW
BID : 4989_GB7CIP
Read: GUEST OE7FMI
Subj: Delta Loops
Path: DB0FHN<DB0FOR<DB0MRW<DB0ERF<DB0FBB<DB0IUZ<DB0GOS<ON0AR<GB7CIP
Sent: 110116/2329Z @:GB7CIP.#32.GBR.EU #:4989 [Caterham] $:4989_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
How to make a Delta Loop
I guess we would like to be able to use a full sized Quad Beam but space & the
neighbours (as well as Local Authorities) don't always like us to!
The next best alternative is to make & erect a Delta Loop. I have worked much
exotic DX using the version shown in my bottom drawing. Such an aerial can be
put together quickly & cheaply using spare wire you may have lying around.
(What do you mean you haven't got any spare wire lying around!!!)
The wire forms a CONTINUOUS loop starting from one side of the feedpoint &
running around to the other side of the feedpoint. The 'o' shown at each corner
is an egg shape glass insulator but any insulator will do. I've even used old
cotton reel spools!
Although for optimum results, a delta loop should be fed with 75ohm twin feeder
going to a tuner & then 50 ohm coax to the TX/RX I have had excellent results
just using 50 ohm coax from my transceiver to the feedpoint but with a 4:1
Balun at the feedpoint.
GO ON, make one & give it a try. You will probably be pleasantly surprised!!!
Mel G4WYW
Here is how to make a DELTA LOOP
o <--- Top Support
/ \
/ \
/ \
/ \
L / \
/ \
/ \
/ \
/ \
/ feedpoint \
o--------- ----------o
!!
!!
!! <--- Random length 75ohm Twin Line
!!
!!
!!
----------
| tuner |
----------
||
||
||
|| <-- 50ohm coaxial line to Transmitter
'L' = Length of ONE side
L = 334 divided by 'f' (frequency in MHz) in feet.
Polarisation is horizontal ie; it 'catches' & radiates into & out of the
enclosed space of the loop like a table tennis bat hits a ball!
Power gain of a Delta Loop is about 1.4 dB over a Dipole.
The Delta Loop can also be fed from a corner with a flat side being supported
as the top, ie;
-------------o-------------------------0-------------
\ /
\ /
\ /
\ /
\ /
\ /
\ /
\ /
\ /
\ /
\ /
\ /
||
||
|| <---------Feeder
||
73 - Mel, G4WYW @ GB7SOU.#48.GBR.EU
-------------------------------------------------------------------------------
Title : Delta loop - slight mod.
From: G0TEZ@GB7HVU.#16.GBR.EU
I just thought I'd mention a slight variation on the delta loop described by
Mel, G4WYW, whose excellent drawing I have left in. Please forgive me, Mel.
I fitted mine in a loft which was only 5' high. It would wave on 11m. I fed it
at one end with 50OHM co-ax. It was supported by 3 large elastic bands, the
type used to peg tents down.
I found that stations that had previously been S3 were 9+ but, they still only
got me at S3 so I put a reflector 1/10th wavelength inside the loop. As it was
on the floor of a loft, I could make it free standing from Baco Foil (aluminium
turkey foil) with 3 supports.
They then received me at 9+. When you're limited to 12W PEP you have to use
tricks like that, Hi!
I know we have a lot more power available on AR but the reflector is well worth
trying .
All the best. Ian.
p.s. I used the formula Lambda= c/f -5% to get the length.
p.p.s. It was a full wave on 11 metres.
-------------------------------------------------------------------------------
Title : Re: Wire Antenna's & loops
From: G0IFI@GB7YEO.GB7FCR.#16.GBR.EU
Like Mel, G4WYW, I've had a lot of success with delta loops. The height above
ground isn't as much of consideration as you might imagine. You can also make a
multiband "nest" of loops, fed with coax & a 4-1 balun.
I had one such arrangement some years ago.
/\
/ /\ \
/ / \ \
/ / \ \
/ / \ \
\ \ / /
\ ___\ /___/
[ ]
[balun]
[ ]
[ ]
Coax to shack
If the outer loop is cut for 40m, it should also be resonant on 15m. I once had
a nest of 3 loops like this, more or less diamond shape, one for 40, one for
20, & one for 10m, top end hung from a tree, sides pulled out by guy ropes.
This made it easy to rotate. It worked great, I was able to work most of what I
heard easily, with encouraging signal reports. One great advantage with a loop
antenna is the QRN reduction, in fact when I first tried a loop antenna on 10m
I thought there was something wrong because of the lack of background noise,
until I tuned across a whopping signal from the USA.
There's a bit of cut & try with a nest of loops, as the resonant lengths of
each loop are affected by the adjacent ones, but it's well worth the small
effort.
Go on, go loopy.
Perry G0IFI @ GB7YEO
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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