Topband: Topband Digest, Vol 122, Issue 15

[Mark Connelly]

Several years ago I did testing of broadband antennas for array use in 
an application for DXing on the AM broadcast band.

In the discussion below, numbers in brackets indicate footnotes that 
reference web links that follow.

At a salt-marsh site in Rowley, MA [1][2], I set up two verticals 
spaced 60 m / 200 ft. on a 82/262 degree axis with the idea of 
time-delay phasing to produce a broadband cardioid pattern with a null 
at about 262 degrees (roughly towards New York City, 340 km distant).

Then I swapped out the verticals for two figure-of-8 broadband loops, 
both positioned for 82/262 deg. peaks, 172/352 deg. side nulls.

The 3 m long active vertical whips were of homebrew design, 
functionally similar to MFJ model 1024 [3].

The 2 m per side square single-turn loops, also homebrew, feeding 
W7IUV-design amplifiers via balun, were functionally similar to 
Wellbrook model ALA1530 [4].

The major difference that was noticed was the loops picked up much 
higher levels of short skip at high vertical incidence angles as 
compared to low-angle DX and groundwave.

Because the vertical inherently suppresses short skip, it is a better 
choice.  The problem about high angle skip is that its arrival time at 
each array element is closer to being simultaneous, thereby reducing 
the effective antenna spacing to perhaps half of what it is for signals 
coming in at 30 degrees or less above the horizon.  The other tricky 
thing about shorter skip is that the phase and apparent direction 
bounce around a lot, especially at sunset and sunrise - times that are 
often the most useful for DX, whether on 160 m or the AM broadcast 
band.

I also did a test with a vertical as one element and the figure-of-8 
loop as the other.  If phaser-box gain was set to make the strength of 
a short to medium skip signal (distance 200-800 km) the same, it was 
noted that a long-haul DX or groundwave signal was about 6 dB better on 
the vertical than on the loop (assuming the station bearing was in/near 
the middle of one of the loop's two maximum-pick-up lobes).

For instance, if WPHT Philadelphia (1210 kHz, about 500 km) was 
step-attenuator-set to S-9 on both antennas shortly after sunset, 
Bordeaux, France (1206 kHz) was S-8 on the vertical and S-7 on the 
loop; UK over Spain (1215 kHz) was similar.  Also, on 1210 with the 
vertical, there was more evidence of co-channel VOAR Newfoundland (at 
about 1500 km) competing with WPHT.

The loop-versus-vertical set-up could be used to produce a cardioid 
over a narrow bandwidth whereas loop-versus-loop or 
vertical-versus-vertical were suitable for desired front-to-back over a 
wider bandwidth.

In summation, testing showed that phasing two verticals was superior to 
phasing two figure-of-8 loops, largely because of the verticals' 
inherent reduction of signals coming in at 45 or more degrees above the 
horizon.

EZNEC plots have been done by Dallas Lankford, Neil Kazaross, and 
others to show that phasing two or more terminated (elongated) loops 
such as Flag, K9AY, etc. can produce excellent front-to-back ratio and 
good suppression of high-angle pick-up, perhaps comparable to using 
verticals as elements.  An array comprised of four terminated-delta 
(Kaz) antennas, as used at a Norwegian DXpedition site, is described 
briefly at reference [5].  Somewhat more information can be found on 
IV3PRK's website [6].  A prior Topband post [7] mentions much other 
documentation (including circuit designs) formerly accessible on public 
websites.  Unfortunately most of it has been migrated to Yahoogroups 
file sites requiring moderator access approval.  As such, it wouldn't 
come up in Google searches.

Mark Connelly, WA1ION
South Yarmouth, MA, USA

[1] http://www.qsl.net/wa1ion/pictures1/rowley_antenna_layout_map.gif
[2] http://www.qsl.net/wa1ion/rowley_ma.htm
[3] http://www.mfjenterprises.com/Product.php?productid=MFJ-1024
[4] http://www.wellbrook.uk.com/ALA1530.html
[5] 
http://www.kongsfjord.no/bm/The%20Kongsfjord%20Quad%20Delta%20Flag%20Array.pdf
[6] http://www.iv3prk.it/user/image/..-rxant.prk_qdfa.pdf
[7] http://lists.contesting.com/_topband/2009-10/msg00057.html

<<
Date: Wed, 13 Feb 2013 07:11:47 -0800 (PST)
From: Rudy Bakalov <r_bakalov at yahoo.com>
To: "topband at contesting.com" <topband at contesting.com>
Subject: Re: Topband: New 160M high performance receiving antenna at
	W3LPL


Tom,

Thanks for the insightful reply. Looks like there is no free lunch 
here- I can't
get better performance by simply using a different circle array 
element. Bummer,
I will have to stick with the verticals.

If space is not an issue, will enlarging the circle diameter make any
difference? Note, however, that I am considering the 3-band commercial 
solutions
(160, 80, and 40m 8 circles).


Rudy N2WQ


________________________________
 From: Tom W8JI <w8ji at w8ji.com>
To: Rudy Bakalov <r_bakalov at yahoo.com>; topband at contesting.com
Sent: Wednesday, February 13, 2013 5:53 AM
Subject: Re: Topband: New 160M high performance receiving antenna at 
W3LPL

> I have been wondering if the antenna element in phased arrays could 
be a loop
rather than a vertical. My thinking is that the loop has some level of
directivity so phasing two of them should result in better side lobe 
suppression
compared to a vertical. Is there any merit to this thought? 
Specifically, will I
see better RDF numbers if I were to use loop elements in any of the 
active 8 and
4 circle systems (e.g., DX Engineering, Hi-Z Antennas, etc.)?
>

Hi Rudy,

A loop can work in a fixed array, or bi-directional array. My first 
antenna
allowing me to work JA's through LORAN from Ohio was a long array of 
loops,
although these were elongated loops. I also had long end-fire arrays of 
small
inverted delta loops in Cleveland in the 80's, and small active 
verticals.

Small loops do not work well when used in things like four squares or 8 
circle
arrays. A multiple direction array, like a four square or 8-circle, 
requires a
uniform pattern of uniform phase from each element or cell.

With a small loop, phase flips 180-degrees immediately after crossing 
the null.
Also, the directivity is generally poor because the small loop has two 
very
sharp null points though the loop axis, but a broad response everywhere 
else.
Both of these things actually hurt performance of arrays with loops 
that depend
on phasing to eliminate side nulls.

Elongated loops are a different story, because (we probably all know) 
elongated
loops are not really loops in function. They are really phased 
verticals, and
the horizontal part or component of the conductors is simply a phasing 
line.
K9AY's, Flags, Pennants, EWE's, and other forms of elongated loops are 
really
all just phased verticals in function. They have a wider null and no 
sudden
phase shift at the null, and no null cone at the side or "loop axis".

The best element for a traditional 8-circle or four square will always 
be a
simple vertical, and even in a broadside array we would want to avoid 
small
loops with deep axis nulls. They are OK as cells in an end-fire array, 
but not
particularly advantageous for pattern unless elongated. I used small 
loops as a
matter of "construction convenience" as deltas in a long endfire array, 
but the
deep side null in that array was really created by out-of-phase cells 
of deltas
and not the sharp null pattern of the individual delta. It could have 
just as
well been verticals with no loss of pattern.

73 Tom

------------------------------

Message: 2
Date: Wed, 13 Feb 2013 07:17:46 -0800 (PST)
From: Rudy Bakalov <r_bakalov at yahoo.com>
To: "topband at contesting.com" <topband at contesting.com>
Subject: Re: Topband: New 160M high performance receiving antenna at
	W3LPL
Message-ID:
	<1360768666.23050.YahooMailNeo at web163404.mail.gq1.yahoo.com>
Content-Type: text/plain; charset=us-ascii

Hi Tim,

This does look like a viable option. Too bad it is single-band and only
bi-directional, although a star-like arrangement (with lots of relays) 
could
work too.


Rudy N2WQ


________________________________
 From: Tim Duffy <k3lr at k3lr.com>
To: 'Rudy Bakalov' <r_bakalov at yahoo.com>; topband at contesting.com
Sent: Wednesday, February 13, 2013 1:43 AM
Subject: Re: Topband: New 160M high performance receiving antenna at 
W3LPL

Hello Rudy,

I am using a pair of VE3DO loops in a phased array for 160 meters. The 
two
loops are spaced 5/8 wavelength (at 1830 KHz) apart at K3LR - aimed at
45/225 degrees (a DPDT relay selects the direction for each loop).

The VE3DO loops are simple to construct and work very well. The in phase
feed for the two loops is simple with equal lengths of 50 ohm coax to a 
T
connector and a 25 to 50 ohm UNUN to match to the 50 ohm RX. The VSWR 
of the
system is excellent with the 9:1 K9AY transformers at each loop feed 
point
up thru 7 MHz. I suggest using a DX Engineering RPA-1 preamp operating 
at 16
VDC to feed the receiver for best results.

Details for the inexpensive VE3DO loop receive antenna is here:

http://topbanddinner.com/page_presentations.html

73!
Tim K3LR

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Rudy
Bakalov
Sent: Tuesday, February 12, 2013 12:00 PM
To: topband at contesting.com
Subject: Re: Topband: New 160M high performance receiving antenna at 
W3LPL

I have been wondering if the antenna element in phased arrays could be a
loop rather than a vertical. My thinking is that the loop has some 
level of
directivity so phasing two of them should result in better side lobe
suppression compared to a vertical. Is there any merit to this thought?
Specifically, will I see better RDF numbers if I were to use loop 
elements
in any of the active 8 and 4 circle systems (e.g., DX Engineering, Hi-Z
Antennas, etc.)?

Rudy N2WQ
_________________
Topband Reflector
>>