My
Low Band Receive Antenna Compendium for Urban QTH’s
Jeff VE1ZAC October, 2012
(Operating comments
added Oct 28,2012)
(Updates Feb 5,
2013)
As promised, I have assembled some personal trial and
error information to share on a selection of receive
only antennas that I have built and utilized over the last 10 years or so. The
antennas have all fit on an urban lot in Halifax, Nova Scotia. I can just get a
200 foot line diagonally across my lot , and a 100
foot line in one direction along one side of the property. The lot is almost
triangular shaped, and I am surrounded by power lines, neighbours and lots of
noise sources. And as I have mentioned before, good RF grounds and I are not on
intimate terms. I have a slim layer of soil over pyretic slate. I usually use
the “Rocky,mountainous”
option in EZNEC to improve model accuracy.
Noise Sources
This is a constant battle in urban locations. One must
be ever vigilant for new noise sources in the HF region and I have had my share
of problems that wound up with solutions, and those that did not. I have
noticed that in the last ten years, the HF bands have been under steadily
increasing assault by manufacturers of noise emitting devices. Governments
(especially in Canada) are no longer interested in protecting radio spectrum
below 30 MHZ and appear to have abandoned any pretence of controlling
unintentional (or even intentional) HF emitters.
Being in the NE part of the continent, I am in a
favourable 2 direction location for a lot of DXing
and contesting. SW of me is nearly all of the US and South Pacific, and NE is a
clear shot across the Atlantic to Europe, North Africa and the Middle East.
There is a decided benefit to being in this location, as often one antenna is
useful in one direction for target stations, and in the opposite direction to
reduce QRN and QRM.
My noise sources include a neighbour to the SW with a
Samsung plasma TV that eliminates reception in that direction on 80M CW and
much of 160M. No solutions there.. when
the noise source was pointed out, his solution was for me to buy him a new TV.
NE of me is a neighbour with a very complex series of computer networks that
lately, have been reduced to blocking reception on 160M. This one is a little
more co-operative and we are steadily reducing the network RFI I am subjected
too. I can’t quite keep up with his purchase of new equipment, but at least he
lets me have input to noise reduction. There are hundreds of dollars of
ferrites on his equipment now, with more added every time I sweep the setup !
I have successfully tracked down several high voltage
insulator problems on power lines with co-operation on repairs from the local
power company, and can usually pinpoint a bad streetlight the same day it goes
rogue. Halifax is very good at fixing streetlights in 24 hours, if you make a
suitable report and clearly identify the light. (They can only do repairs
during the day, so rely on accurate reporting)
In my own house, I have replaced a DSL internet
connection (very RF noisy) with a cable system (no noise) but I can still hear
my NE neighbours houses as they have both subscribed to new fiber optic system,
that generate tons of noise. How, you ask ? The fibre terminates in the
subscribers house in a receiver that turns it back into a DSL line, which then
sends the data around the house on copper. This of course, makes a nice RF
source.
I believe this is a typical urban situation. Noise
sources can be located within 100 feet of my house.
Receive Antenna Requirements
My receive antenna needs involve several tasks:
1.
Reduce the
plasma TV source
2.
Reduce local Ethernet and DSL RFI noise
3.
Aid in direction finding new noise sources ( in
conjunction with an Icom R2 portable scanner, I have
been very successful in locating noise sources)
4.
Aid in DX reception of weak signals from MW BCB to
30M.
5.
“Prefer” a direction, usually NE or SW for contesting
from 160 to 40M
6.
Improve signal to noise ratio of inband
signals ( this is often the most important receive antenna function)
I also am always interested in exploring the compromises
that a modern ham can utilize for improving operations with receive antennas.
And, not living in a roomy rural location, I have to wrestle with limited space
and close in noise sources, like most hams these days. On top of that, readers
of my articles know I like to experiment and build things, so all my projects
are homebrew, and sometimes get complicated.
Credits
I have followed all of Vic Mizek’s
ideas and suggestions on beverage antennas, referring often to information from
his “Beverage Antenna Handbook”. Also I have been very influenced by Dr. Dallas
Lankford, a retired math prof who lives in Louisiana and is a very keen antenna
experimenter and MW BCB DXer. Dallas has been very
helpful with comments on verticals, phasers and the DADFA I installed this
summer. And, of course, there are many hams that have published information
that I have used, including John Develdore, ON4UN,
Tom Rauch, W8JI , Gary Breed and Greg Ordy. I highly recommend you refer to any information
offered by these folks.. it’s
all high quality, and I am in their debt for making their experiments and
discoveries available to folks like me. And of course, without the work of Roy Lewellan and his wonderful EZNEC modelling software, I
would be living in the Stone Age, antenna wise.
My Low Band Receive Antenna Collection
My current crop of receive antennas consists of a
homebrew compact 4 square active antenna, a shortened dual (not active, now)
delta flag array pointed to the NE (Europe) and optimized for the MW BCB, and a
dual reversible K9AY.. an
antenna that has earned permanent status at this QTH.
Past antennas included a single compact pennant, a
dual vertical array with adjustable phaser for steering the nulls, a Mizek
style, 60 foot short steerable wave antenna (SWA) with adjustable phaser, a 200
foot short reversible beverage and 200 foot short coax reversible BOG antenna.
On the same lot, I also have three transmit antennas,
including a 30 foot monopole that has a base mounted matching device for 80,40, 30 and 15M, a Steppir dual
element Yagi at 33 feet and a Radio Works 80M Carolina Windom, with the center
at 55 feet, also capable of being switched to a 160M vertical Marconi antenna
with top loading. This wire antenna runs over top of the 4 Square and does
interact with it, affecting its performance.
I have noticed a lot of material on the internet
dealing with theoretical performance of many receive antennas. I am well versed
in doing this, but I am going to stay away from that in this article and
report, and instead report on my practical experience with each. This will
include my construction and tweaking results and use in DXing
and contests. I like to make simple comparisons via subjective index scores,
and have developed one to rank my antennas. This does not tell the whole story,
of course, and I am including a little narrative for each antenna. However
there should be some information for nearly any practical question the reader
might have on how these antennas compare for me.
Retired Receive Antennas
200 foot Reversible Beverage
This was the first antenna I built after studying Vic Mizek’s ‘Beverage Antenna Handbook’. I implemented this
with 300 ohm twin lead strong across my yard to 200 feet with a homebrew
matching and switching device. It worked as advertised and mine was approx. SW
to NE.. making it very useful
for 160 and 80M. It wasn’t quite equal gain in both directions but the F/B
ratio was in the range of 20 to 25 dB.. respectable for a short antenna.
The biggest problem I had with this antenna is that it cut right across my yard
and was also useful as a “Pirate Alarm” (as nick named by the neighbourhood
kids). It had to come down in the summer. Further, it ran right underneath the
Windom wire, and when this was converted to a 160M vertical Marconi, the beverage
was an interaction problem. It was retired, in favour of a BOG. This antenna
received well from BCB to 30M
The BOG
This was a 200 foot piece of RG6 on the ground in a
“straight-ish” line with the Mizek style feed and
reversing setup. It played very well on 160M, but was basically dead on
other bands. Reversing was terrible with maybe 1 S unit F/B. This antenna
wasn’t in the way, and I was on to other receive antennas at the time, so it
sat neglected. BOGS are still of much interest to me as a portable 160M receive
antenna. I have rolled out a 600 foot one at another site with very good
results in the target direction.
The Mizek SWA
This was a very technical antenna that could do some
amazing things. It consisted of parallel wires, 1 foot apart, 6 feet high and
60 feet long, fed by two feed lines to an adjustable phaser. A very deep null
could be steered around 360 degrees with careful tuning of a quality passive
phaser, per Mizek/Lankford design. For example, most evenings here in the NE,
one can hear Saudi Arabia on 1521 KHz and WKBB Buffalo on 1520 KHz interfering
with one another. The SWA and phaser could null either of the two stations into
the noise, leaving the other one in the clear. This is an astounding antenna
feat! I have not repeated this with any other antenna. It worked well BCB to
40M, and was excellent for DX use. It was far too fiddly to use for contesting
though. In fact, antennas requiring adjustable phasers really have no use in
the contests I have participated in. Simple 2 direction switching is useable, 4
direction switching even less so. There are just too many other things to deal
with during the contest and direction switching isn’t one of them. With the
exception that you might want to favour SW vs NE, say. That works pretty well,
and makes a lot of directional receive antennas shine during a contest. (my opinion).
This antenna was a real novelty and gave some great
demonstrations for visitors. In the end, I needed the room and took it down. It
did not have much gain, and needed a Norton preamp to produce good signals.
The ‘Beverage Antenna Handbook’ is available from RadioWare online.
The Dual Verticals with Phaser
Two 13 foot verticals with transformer feeds, spaced
60 feet with low noise balanced feed line feeding a pair of Lankford ‘PPL’
emitter followers and an adjustable phaser in the shack can steer nulls around
180 degrees. In practice, this was another amazing antenna. It could null the
1520/1521 KHZ AM stations as the SWA antenna, but not quite as deep. Further,
the null was very useful to place on local noise, leaving the band open for
desired signals. In addition, this antenna allowed very good reception of the
European long wave signals here in NA. For such a small antenna, this was
amazing. The reason it worked so well was its noise cancelling null placement
features. This is a much simpler antenna to build and setup as well. This is a winner for small lot simplicity, and
very good for DXing work. If you have a pest plasma TV or other RFI source close by, this is an
effective antenna to kill the noise.
Update (Feb
2013): I now have a pair of 13 foot verticals spaced 60 feet
apart, with Lankford style PPL’s at the base making them active elements and
fed with CAT5E. Inside the shack I have a pair of Norton 11 dB preamps available
for each. Without the active elements, these whips were dead beyond 80M. Now
the system is useful to 40M and beyond. Currently, I can switch in a DX
Engineering phaser or my Lankford style phaser. This antenna pair works very
well for local noise source suppression and as a reference antenna with phaser
and one of the loops, either K9AY or mini DADFA. I have used this, with the
K9AY and the mini DADFA in 4 low band contests since November with very good
results.
Further, with local noise sources I have below 200
KHz, this is the ONLY antenna I have that produces results on the LF
broadcast band, 150 to 200 KHZ. Most evenings I can null the local noise and
actually listen to 3 or 4 of the European and middle
East power house stations on this band.
The Pennant
This is probably the simplest, cheapest, least complex
and best performing receive antenna out there. It has a 30 foot footprint and
only needs 15 to 20 feet of height to work. And work it does. It does interact
with its own feed line and with other antennas, but if you are careful with
these things, it is a stellar performer. It is not unreasonable to get 30 dB
F/B with one of these, on 160 M. A perfect antenna to aim
into the SW or NE for 160M contests. Best of all worlds
?.. have two of them, one for each direction.
This antenna plays well with fishing pole and short tree supports. Nearly every
low band ham aficionado on a small lot can setup one of these. It also works
well over crappy grounds.. like
my QTH and much of Halifax. It looks like a triangle on its side. I used this
in several 160M contests with good results. Best
bang for the buck receive antenna. It is very simple to build and erect.
Current Receive Antennas
K9AY 4 Direction Loop
I have liked this antenna from the day I put it up. It
has earned permanent status at this QTH. It is robust if spring mounted, and a
homebrew switching system and continuously adjustable termination resistor has
worked very well since the beginning. It is in a less than ideal location, on
rocks but still works very well. It is low noise, shows some 3 or 4 S units F/B
and has plenty of sensitivity even on 20M with the addition of a Norton preamp.
This is my workhorse receive antenna for 160 and 80M, and often allows a signal
I can hear on my transmit antenna become more intelligible on the K9AY
with a dramatic increase in SNR. If I could only
have one receive antenna for ham use, this would be it. ( * changed my
mind on this, see comments at end of article) For contesting, it’s a natural.
The switching system makes this a little more complex than a simple pennant,
but the results are worth it. Low foot print space needed and only one support
or tree. ( 30 feet by 30 feet space will do)
DADFA
This is a compact version of the Dallas Lankford opus
work on high performance phased arrays for MW BCB DXing. Happily, these are
fairly broadband devices and easily scaled to ham bands. I built the compact
dual MW version this summer after some conversation with Dallas concerning the
building and operation of these antennas on small lots. And, I can confirm,
they work as advertised, or better, are easy to build, and simple to put up. I
happen to have one line to the NE that I can just fit the 100 feet
needed for this short version of the antenna, and it is a crowd pleaser( well..
me). It works on 160 M quite well too, but Dallas tells me it would be better
on 160 if it was cut for 160. I may try that next. It is really fun to pick out
all the Eu MW stations you can hear most evenings.. I
can easily detect or hear maybe 40 or 45 any particular night. Very cool. I am looking forward to trying on 160M DX
this winter. As a happy coincidence, the plasma TV noise source is in the null
of this antenna to the SW of me. I can’t hear it at all. On bad side, because
of that TV source, there isn’t much point in reversing this thing as that
plasma TV is going to dominate the band to the SW.
This antenna makes the 1520/1521 KHz AM station
separation test work quite nicely. It doesn’t suppress the station in the
opposite direction as well as the Mizek SWA array, but nicely brings up the
desired direction so that an ECSS or SSB detector can hear the station fine.
And no fiddly adjustments.. just
switch the antenna online and away you go.
At a rural site where I might have 200 to 250
feet in two directions, I would build four of these things. By all accounts,
these antennas outperform shorter beverage antennas, hands down, and in many
instances, even longer beverages. If you can space the two delta flags 50 feet
apart, they get even better. I started
mine with active elements, using the Lankford PPL element, but found they
weren’t necessary. Instead, I have a Norton preamp inside on the phaser output
line that can bring 11 dB gain online when needed. The
phaser for this antenna is a fixed device. One project I will do next is make a
separate phaser tweaked for 160M use.
If you have 100 feet of space and can figure out 2 x
15 foot masts (I used trees and springs but Dallas uses collapsible fishing
poles) I highly recommend these antennas for low band reception. Very cheap to build and not too complex. In fact, the most
complex item is winding a few toroid chokes and transformers..
not too difficult a feat for most home brewers.
My current DADFA consists of 2 deltas, 15 feet
high with a 50 foot base, end for end with each other, in a 100
foot( 30M) line. This one is really made for the MW BCB DXing. It has 900 ohm
termination R's and a -212 degree net phase shift in the combiner. I will be
replacing it shortly with a smaller pair of delta's on the same space. They
will be 15 feet high with a 25 foot base, spaced 50 feet apart. This one has
better performance on 160M but has less gain, so will need to use the Lankford
PPL's for each element. It's termination R's will be 650 ohms and the phase
shift will be -225 degrees. Modelling wise, this smaller one has better F/B
performance over several ham bands but one pays a little price for sensitivity.
That isn't a problem with the PPL element amplifiers.
These antennas should open up all kinds of property
ideas for hams thinking they need a field full of 1000 foot beverages, but
lacking the property funds. As Dallas says, these are beverage killers. There
are some really notable 160M contest results from stations using flags and
delta flag arrays now.
As a bonus, this antenna hears well from LW up to 30M.
It’s not as directional but very low noise and still directional enough to be
an antenna asset. This one gets high marks from me. And keep in mind, mine is a
compromise short version because of the 100 foot requirement.
As a side note, Dallas is a great fan of balanced feed
lines and has discovered a very cheap alternative to expensive twin axial. That
is CAT5E shielded Ethernet cable. It’s dirt cheap here..
I picked up 1000 feet of this stuff with an outdoor rated jacket and shield for
less than $300. The cable twisted pairs are 110 ohms with a VF of .72 as
measured on my HP 3589 VNA and AIM4170C. I have used this on my dual vertical
array, the DADFA and on the 4 square receive, along with common mode chokes at
each end, with excellent results. It is my new standard receive antenna feed
line.
Note: coax is frowned on by Dallas and many others
because of the common mode noise pickup problem.
This antenna is an array of two loops, fed through a
phase delay combiner to provide a beam pattern. Pushing the two loops together
so they are end for end still allows a beam to form, but this improves as you
separate the two elements. Dallas has done a lot of work evaluating these antenna
arrays in 2 and 4 element models, and their performance is nothing short of
astounding. Even from my very compromised 2 element
model, I can see this would be my top choice for an antenna farm where I had
some space to put up some more of them. And they are very simple to put up. One
15 or 16 foot center pole is all that is needed. Collapsible fishing poles work
fine. One matching transformer, one common mode twin choke, a resistor
termination and some balanced feed line like CAT5E shielded comprises the rest
of the antenna. Each element needs a feed line back to the combiner, and they
must be equal length. If you had more than one of these arrays you could
conceivably have a switching control box out at the array field to reduce runs
back to the shack. The combiner is a couple of simple toroids
and resistors and one Norton preamp is useful for added gain. The Lankford
designed Norton amp is available from
Jack Smith at Clifton Laboratories in an easy to assemble kit, and all of
Dallas’s technical information is best gathered by joining the Yahoo group “The
Dallas Files”, where all of the articles and details are available as PDF
downloads. (Thanks Dallas and Jack!)
This is my first experiment of an array of loops, and
I am very pleased with the results. You can easily demonstrate better-than-beverage performance in a small
space with one. Plus, for a 100 foot (30M) footprint, this is the best DX
antenna I have ever used. The F/B on this antenna is over 36 dB, in my setup. I
might even convince myself it's over 42 dB. My new 160M scaled version is
showing over 60 dB F/B on the model. I have built it, but not done any testing
with it yet. (I will mention the results here when I do.)
Yee ha ! Just fired this thing up ( Sat.
Oct 13) and can confirm at least 55 dB+ F/B on an 80M CW source, really
excellent on MW BCB F/B and better than the larger DADFA on 40M F/B. Looks like I have a winner for best DX
antenna..certainly my new favourite ! Smaller elements are easier to
deal with as well. I have 15 foot fish poles to hold these up. I have also
added a simple feedline reversing switch on one feedline at the phaser, which
lowers the RDF/null depth. Very handy for ham use. This is my new
favourite all around antenna !
My phaser works extremely well, despite numerous
compromise issues. Bad ground, other antenna elements nearby, a utility
entrance at one end of it.. still, it provides amazing performance
from MW BCB to 40M. It even shows pretty good nulls on 30M. It is very low
profile, uses a very small amount of space and still performs better than most
beverage antennas I have seen or heard. Was I just lucky with this
antenna ? I don't think so. I did pay a lot of attention to get my phaser to
perform the desired delay by measuring this delay with a VNA. That compensates
for construction vagaries, capacitive affects and other problems.
Plus, I added a 1 dB pad on the non delay feedline to help balance the signal
levels. Maybe this contributes to the deep nulls but I think these are more
tweaks than anything else. The added single feedline phase reverse switch is a
winner for using the antenna as a great loop with lesser nulls and RDF than the
full mini DADFA. With this new functionality, I could now live WITHOUT my K9AY !
(Yikes), especially if I had two of these DADFAS setup in the yard.
Update Feb
2013: Stellar performer in low band
contests since November. In fact, I could easily live with this as my only
receive antenna and be quite happy for low band reception.
The 4 Square Active Receive Array Project
This one is a project I have been toying with for many
months. In fact I started it last winter. I will show construction details in
another article on the website, but I have finished the array and am using it
now. I utilized knowledge from Dallas Lankford’s array work and Tom Rauch’s
(W8JI) version of the 4 square with time delay phasing. Information on this system is available in
John Devoldore’s “Low Band DXing” book from ARRL. My system has 16 foot
elements in a 40 foot square (just fits in my yard), is heavily compromised by
other antennas and buildings, has Lankford style PPL emitter-follower active
elements and uses shielded CAT5E feed lines. This was a very complex antenna
project. I had to make many boards for the controller and pay a lot of
attention to common mode chokes, very low ripple power supplies, hard to make
short phase delay lines and lots of other niggly little issues. In the end,
mine is tweaked by delay line adjustment and is still not perfect. The small array spacing
means the delay lines are quite fussy. However it is useable the way it is and
I will get some operating time with it in the next few contests. It works well
on MW BCB, 160 and 80M. Although I have no real experience with it on 160 yet.. too early in the season and I
have another noise source to deal with that is poisoning the 160M band right
now. That problem has to be solved first.
Next I will make a better set of delay lines for best
RDF (the ones I have in there now are pretty hacked up from additions and
deletions) and another set for best F/B for experimental purposes. Now that I
have some knowledge to confirm the on board delay of 1 degree on the long line
and 3 degrees on the short lines, I have more confidence in cutting and measuring
the delay using my shop VNA, an HP 3589. You could take your wire over to a
friend’s place that has a VNA to measure yours...you don’t have to have one on
site. But it is a true experimenter luxury to have a VNA in your shop! Also,
once you have some confidence in your VF and measured lengths, you can proceed
with just accurate measuring and be in good shape. I may get really crazy and
install a set of switches or pin jacks in my control box, with both sets of
delay lines so I can switch between the two for evaluations.
This was by far the most technically complex antenna
project I have ever undertaken, and I can easily understand why DX Engineering
sells the W8JI design/kit for as much as they do ( This not a cheap antenna). These things work, but
they are critical when you try and compress them as I have done. Larger sided
squares are less fussy and give better results. The DX Engineering kit
recommends 70 feet per side, I believe. Still, I wanted to see how these
antenna arrays could play out in a small lot situation and 40 feet should be
available to lots of hams on small lots. In fact this antenna would be a good
choice for “No room” lots where even 100 feet is a problem. It would be a
tossup between one of these, a K9AY or a Pennant or two.
This array definitely interacts with the Windom wire
that runs above it. This interaction can be reduced by switching the Windom to
its Marconi 160M mode.
So far, pros include the low footprint of the receive
elements, and the simple direction switch inside the shack. It is plenty
sensitive enough up to 20M with the 2 Norton preamps in the system (one of them
is switchable in or out). On the cons, it is more sensitive to my neighbour’s
data equipment interference. As a result, it’s hard to get low SNR’s on weak
signals when compared to the DADFA or K9AY in some situations. So, I have to
get at the source of the low band noise first before I have the definitive
comment. However, if you know you have a lot of local noise from network
equipment, this may not be the antenna for you.
I have experience with it now on the MW band, 80M 40M and 20M receive, where it works well. 160 and
LF are the noise bands at the moment that need noise source reduction. The F/B
near the design frequency is easily 5 to 6 S units (30 to 36 dB) and it is
quite sensitive. The model shows 60 dB nulls, but I have not been able to
demonstrate those yet. Plus, this antenna is located near obviously interfering
antennas and structures. I may not be able to get it to the modelled null depth
as a result. (I will keep trying)
As far as building one, it is entirely doable by the
advanced home brew folks. But even buying parts for home brewing is going to
put the cost of this 4 to 6 times more than a home brew K9AY or DADFA. Plus you
probably do need some instrumentation, or a friend that has some, for a compact
4 square like this one. A vector network analyzer (VNA) is useful for checking
phase delays and the AIM4170C has a TDR function making it easy to set the feed
line length exactly the same between
elements (if you can’t measure them in advance, as happened to me as I
reused my previous two phased verticals
as part of this project).
I used Eagle CAD to make a series of small boards
which hook together to make the total switched system. My boards are one sided
and etched on a small SherLine vertical mill
converted to a CNC system. It makes nice boards for RF use as the surplus
copper is left on the board for a ground plane. The construction article on
this website will give a few details and a commentary on some of the challenges
to make this project come alive. It wasn’t really cheap and it was fairly
complex, including requiring surface mount skills to install about 50 WRE
surface mount common mode chokes! (I took Dallas’s common mode choke recommendation’s seriously).
The best job I could do on the delay lines was to
bring the delay lines and the combiner to the shop, terminate unused inputs and
outputs with 100 ohm resistors, calibrate the leads on my VNA to 0 degrees at
1.81 MHz (the design frequency) and then go at the delay line trimming to get
the desired overall phase at the combiner output. This method takes into
account all of the fabrication delay characteristics and allows you to get the
delays as close as possible to the desired EZNEC values. These were -30 degrees
to the rear, and +165 degrees to the sides in my case. These are the best
RDF values for a 40 ft square with 16 foot elements. I also installed a 50 ohm
resistor in series with each element to swamp the mutual inductance problem,
which shows up as -R in the complex impedance model on EZNEC. You don't want
this to happen. The antenna element itself is such a high impedance that the 50
ohms has no effect on sensitivity. At this point, everything is working as
advertised, but I need to operate the antenna in some DX and contest
situations.
Another slight con for this antenna involves the
active elements. Mine are relay grounded when no power arrives for the
emitter-follower circuit, and my shack controller has a transmit relay input to
ground the antenna during transmit. Even with input protection devices on the
front end of the pre amps, it is a very good idea to do this, or you will be
replacing fets on a regular basis.
Another problem may exist if you live near an AM
transmitter or other high power low frequency transmitter. It may be necessary
to build a front end filter to trap some of this energy before it creates IMD
problems in your antenna amplifiers. I have no such problem here, and the
Dallas Lankford PPL circuit is very good for use in active elements. They have
certainly been working very well for my receive antenna experiments. You can
build these yourself from information on the "Dallas files" group
site or you can buy these from Jack Smith at Clifton Laboratories. He
calls them 'Hi Z' amplifiers, but they are the Lankford designed units, and
very well made, as are all of Jacks items. The commercial system from DX
Engineering has front end filter options available in the antenna box.
In the end, I have an incomplete experience base for
this antenna. It certainly has a negative due to the cost of buying or building
one, compared to other small lot antenna options. However, it is very low
profile and low yard requirements. The active elements generally do not require
ground radials. A simple 2 foot ground rod is more than adequate. They do
interact with close by structures and antennas a little more than the loops
seem to do. It is a very good candidate if you
enjoy a technical challenge. And it is very low profile if you are
trying to be discrete about antennas in your yard. The black collapsible
fishing poles as elements are hard to see against trees.
Update Feb
2013: This antenna was retired in
late fall to concentrate on contesting for the winter. I will have a revisit to
it in the spring. (Depending on other projects, fishing,
golf, etc.)
The Comparison Chart
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VE1ZAC Receive Antenna comparisons |
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Receive antennas |
Current |
DX Use |
Contesting |
Directionality |
Front/back |
Ease of Use |
Interaction |
Kill noise |
Foot print |
Height |
Score |
Complexity |
Cost |
Score |
|
1 |
K9AY, 4 directions, with Norton preamp |
√ |
4 |
4 |
4 |
3 |
3 |
5 |
3 |
4 |
4 |
34 |
3 |
3 |
40 |
|
2 |
Compact DADFA.. Lankford style dual |
√ |
5 |
4 |
1 |
5 |
5 |
5 |
5 |
2 |
5 |
37 |
3 |
5 |
45 |
|
3 |
Compact 4 square receive, 40 ft. sides, |
|
2 |
4 |
4 |
3 |
3 |
2 |
3 |
3 |
5 |
35 |
1 |
1 |
37 |
|
4 |
60 foot Mizek SWA with phaser |
|
4 |
0 |
5 |
5 |
1 |
3 |
5 |
3 |
5 |
31 |
3 |
4 |
38 |
|
5 |
dual 13 foot vertical elements with |
√ |
4 |
1 |
4 |
5 |
2 |
3 |
5 |
4 |
5 |
33 |
3 |
4 |
40 |
|
6 |
Compact pennant, 30 foot ground |
|
3 |
4 |
1 |
5 |
5 |
5 |
5 |
5 |
5 |
38 |
5 |
5 |
48 |
|
7 |
200 foot reversable coax BOG with |
|
1 |
3 |
2 |
2 |
3 |
5 |
2 |
2 |
5 |
25 |
4 |
4 |
33 |
|
8 |
200 foot reversable beverage at 6 feet |
|
3 |
4 |
3 |
4 |
3 |
5 |
3 |
2 |
5 |
32 |
3 |
3 |
38 |
|
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|
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Transmit antennas |
|
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|
|
9 |
80M Carolina windom, 55 feet |
√ |
|
|
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|
|
|
|
|
|
|
|
|
|
|
10 |
30 foot ground monopole, with switched |
√ |
|
|
|
|
|
|
|
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|
|
|
|
11 |
Steppir dual element yagi at 33 feet. |
√ |
|
|
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|
|
|
|
|
12 |
80Mwindom can be switched to 160M |
√ |
|
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Noise sources |
|
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|
13 |
Plasma TV, Samsung 50", very loud, |
|
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|
|
14 |
NE neighbour Dlink powerline ethernet |
|
|
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|
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|
15 |
NE neighbour network routers, low band |
|
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|
16 |
Power line noise, currently low |
|
|
|
Scoring |
|
|
|
|
|
|
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|
|
|
|
17 |
Streetlight noise, currently low |
|
|
|
|
Low |
1 |
Not so good |
|
|
|
|
|
|
|
|
18 |
NE and NW neighbours, DSL line noise, |
|
|
|
|
Medium Low |
2 |
Problematic |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Medium |
3 |
Can live with it |
|
|
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|
|
|
Medium High |
4 |
Good |
|
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|
|
High |
5 |
Very good |
|
|
|
|
|
|
|
My rankings then, based on the scores with
applications largely applicable to ham contesting and some DXing
follow:
Ranked list by sub score, excluding complexity
and cost
|
1 |
Compact pennant,
30 foot ground |
38 |
|
2 |
Compact DADFA.. Lankford style dual |
37 |
|
3 |
Compact 4 square
receive, 40 ft. sides, |
37 |
|
4 |
K9AY, 4
directions, with Norton preamp |
34 |
|
5 |
dual 13 foot vertical
elements with |
33 |
|
6 |
200 foot reversable beverage at 6 feet |
32 |
|
7 |
60 foot Mizek SWA with phaser |
31 |
|
8 |
200 foot reversable coax BOG with |
25 |
Ranked list by net score, including complexity and cost:
|
1 |
Compact pennant,
30 foot ground |
48 |
|
2 |
Compact DADFA.. Lankford style dual |
45 |
|
3 |
K9AY, 4
directions, with Norton preamp |
40 |
|
4 |
dual 13 foot vertical
elements with |
40 |
|
5 |
200 foot reversable beverage at 6 feet |
38 |
|
6 |
60 foot Mizek SWA with phaser |
38 |
|
7 |
Compact 4 square
receive, 40 ft. sides, |
35 |
|
8 |
200 foot reversable coax BOG with |
33 |
Interestingly, the ranked list changes the 4 Square
between the two scores. The spread between the scores shrinks when you
include cost and complexity factors, and the 4 Square drops down the list. They
aren’t that far apart, but it seems obvious the sophisticated compact loops
score the highest overall.
My Contesting Conclusions
· Cheap
and Effective: go for pennants
· Slightly
more complexity, a little more money, way more performance and utility,go for a
DADFA or K9AY (Don't forget to include
the reversing switch for the DADFA)
· Enjoy a
challenge and don’t mind the cost ? Go for the 4
Square, but keep one of the loops on board as well.
· If more
room available.. several DADFAs or a larger 4 Square
active (70 foot spacing)
DXing
Conclusions
This one is easy.. DADFA in
the wider spaced mode is the way to go. Erect a few of them if you have the space.
I really have no valid experience with DX use of the 4 Square at this point,
but I will report on it when I have some.
Direction finding low band noise sources
Clearly, the K9AY and the 4 Square active are the
perfect candidates for this task.
Construction Conclusions ( from my current receive
antennas)
The 4 Square active array is a bit of a project. You
can buy one from DX engineering but that one states it must be used with 70
foot spacing. if you don't have that, you are back to the problem of building
custom phase delay lines to deal with the smaller spacing. So far, I have only
been able to accomplish this with the aid of a VNA (vector network analyzer). I
intend on making a new set of delay lines for best model null, rather than RDF,
next. If you decide to build one, you can buy the active element emitter
followers and a Norton preamp or two from Jack Smith at Clifton Laboratories,
which makes the rest of the project a little easier. You still have to deal
with the switching matrix and the hybrid combiner , but these can be made by a
variety of home brew methods without any serious difficulties. Keeping track of
signals and control lines and signal line polarities is very important and it
is easy to make a wiring error. Plus, common mode noise pickup is the enemy of
these antennas and attention is needed to prevent this from detracting from
receive signal signal to noise ratio.
The K9AY and the mini DADFA's are much easier to build
and not as complex. Both can benefit from a Norton preamp, which can be
purchased from Jack Smith if you don't want to build your own. The mini Dafas
also need the emitter follower amps for each element. There is no need to put
them outside though. They work fine if placed at the termination point in the
shack. A handful of epoxy coated ferrite cores is also needed for winding
transformers, baluns and common mode chokes.
In order of increasing complexity of the high
performance receive antennas, it would be K9AY, DADFA and then a 4 Square
active array.
The penant is the simplest of the bunch, and
considering it's receive performance enhancement, it's an attractive choice.
Overall, I have found receive only antennas so useful
for low band ham radio, that I will probably never be
without one.
I hope you find this information useful. I will be
working on my 4 square construction details article next.
Enjoy
Jeff VE1ZAC