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Old October 5th 17, 06:45 AM posted to rec.radio.amateur.moderated,rec.radio.amateur.antenna
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Default [IW5EDI] An effective 3 Band Wire DX Antenna


IW5EDI Simone - Ham-Radio

///////////////////////////////////////////
An effective 3 Band Wire DX Antenna

Posted: 04 Oct 2017 01:10 PM PDT
http://www.iw5edi.com/ham-radio/2295...ire-dx-antenna


First, please excuse my artistic abilities. The diagrams are basic but show
the rudiments of this excellent aerial, which is ideal for the newcomer to
HF and those on a small budget as well as those with little space to erect
large arrays!

Please note that my calculations are worked out using feet and inches
because thats what I grew up with! The reader who understands the Metric
System should have no difficulty in converting to Centimetres and
Millimetres but this article will use Feet and Inches.

Before outlining the construction, I would just add that when I was first
licensed, I tried various aerials, verticals; inverted Vs, inverted Ls and
wire dipoles. I finally gave this design a go. It was a brilliant success
and I had a confirmed (QSL Card) contact with CE0ERY Hector on Easter
Island on 30/04/1984 quickly followed by VKs, ZLs, and a string of exotic
DX throughout the Indian and Pacific oceans.

YES using this same design I am about to explain to you in the following
paragraphs!

WHAT YOU WILL NEED

You will need some wire…I have always found that old or new house wiring
cable is an excellent source of wire but will need to be stripped from the
grey outer insulation. The red and black pair of wires needs to be further
stripped from their coverings. If you dont fancy this task, it will still
work, BUT its better to use naked copper wire for best results.

Heres how I strip wire in long lengths.

First I use side cutters and cut into the wire from the end, trying to keep
close to the bare earth wire that is in the centre of the cable and which
runs along the length.

Once I can get a grip on the end of this earth wire with a pair of long
nose pliers, I twist a few turns around the nose of the pliers and gently
pull. Soon there will be enough slack grey outer sleeve to allow it to be
held in place with the feet standing on it firmly. I have also tied the end
of the grey insulation (with red and black wires) to a door handle or vice
handle.

Once the thin earth wire starts to strip it usually comes easily as long as
a steady firm pressure is applied and sudden jerks are avoided. When the
thin wire has been removed from the entire length, having acted like a
cheese cutting wire, the red and black should peel out without any bother.





The 75 ohm twin feeder that I used was cadged from a BT worker that I
spotted while driving home. I approached him and told him what I needed
some for and asked if he might be able to oblige. I made sure that he
spotted the couple of old One Pound notes that I held in my hand. He cut me
off a generous length but refused to take my money. I told him I owed him,
thanked him and rushed home to start making my aerial.

You will also need a small square or oblong rectangle of insulating
material such as Perspex or Paxolin. I didnt have any so I made do with
some plywood which I drilled and varnished until I was able to obtain some
better material later. It is also possible to use a custom centre piece
complete with female coax socket for the feeder and two wing nuts
(butterfly nuts) at each end of the T-piece where all the bare ends can be
twisted together and connected. This is the quickest method and gives
reliable results but regular swinging in any wind WILL eventually cause
breakages at the connections! A proper centre piece with female SU socket
is not too expensive but youll experience greater satisfaction if you make
up the part yourself.

To avoid becoming confused, it is preferable to work with one pair of
quarter wavelength wires at a time and to use a short strip of masking tape
folded and pressed together over the end of a length of wire and marked in
Biro 10 M and 15M and 20M as appropriate.

After you have ended up with pairs of wires, all cut to length ready for
connecting to your centre piece, the next thing to do is to connect all the
ends together and to the feeder.. Look at the enlarged diagram showing the
centre-piece to understand how this is done. Basically, the end of each
wire is passed through two holes, an overhand knot (one turn over the wire
and through the loop) pulled tight will prevent the wire from being pulled
out of the centre piece. Strip off about half an inch of insulation from
each wire end after the knot has been tied and connect all the ends on one
side of the connector centre piece and to this should be added one side of
the 75 ohm Twin Feeder which is commonly used as telephone wire leading
from telegraph poles to the house and which is a superb match when used as
a feeder or Transmission Line for this aerial design.

After fitting, joining and soldering the joints, each bare wire and
soldered joint should be covered by a blob of bathroom sealant or other
rubberised substance which, when dry, should offer some protection from
weathering. It will pay dividends to check and perhaps redo this each year
with your annual inspection and maintenance. What do you mean, you dont do
annual maintenance?!

Although the final choice is completely up to yourself as to which band you
have at top, bottom or in the middle, the results I achieved came from
having the shorter 10M pair at the top, the 15M pair in the middle
horizontal position and the 20M pair at the bottom working as an inverted
V. The reason why this design gives such good results is because of this:
At ten metres the 10M section acts as a half wave dipole but at the same
time the 15M section also radiates some lobes and the 20M section acts as a
full wave dipole on 10 metres in addition to the radiation from the actual
10M section.

Now that you understand how each section interacts with and reinforces each
other section, it is time to look at how the individual lengths are worked
out.

L (length) = 468/F (frequency in MHz)

/ = Divide

As an example, suppose you wish to operate the 20M dipole at 14,250 KHz
(14.25 MHz).

Length (overall of half-wave) = 468 / 14.25 = 32.84 or 32feet 8 and a half
inches.

(You will see that I have approximated the inches. Such a small inaccuracy
will not make any noticeable difference!)

Divide 32.84 by 2 to give 16.42 feet, the length of each quarter wave
section that makes up the half-wave dipole length.

Purists may wish to add an inch and a half to allow for the knots at the
support points at each end. Where the bare end of a wire connects to an
insulator such as an egg type insulator, pass the wire through and around
the insulator then twist the end back over the main wire with a series of
small twists or turns. (Bare wire!) The length in this case will be to the
centre of the bend where the wire curves back on itself at the insulator
and NOT to include ALL the total length of wire providing it does indeed
connect back on itself and in effect is shorting itself out!

So there you have it. The formulae to work out your own individual
measurements and the instructions for putting it all together.

PLEASE REMEMBER NEVER TO ALLOW ANY OF THE SECTIONS TO BE CUT AS A HALF
WAVELENGTH FOR A BAND FOR WHICH ANOTHER SECTION IS THREE HALFWAVES!

For example, if you cut the lowest dipole for 40M, you would not wish to
cut another section for 15M as they would interact giving a wrong
feed-point impedance in addition to a skewed radiation pattern.

In practice there will be small differences in impedance and standing wave
ratio (SWR) in each different location. This is due to conductivity of
soil, height above ground, wire type and other tiny factors which we have
all experienced in our hobby as Radio Amateurs from time to time.

In conclusion, I do not claim this as my design. Indeed, it can be found in
varying forms in a number of books on Antenna Design. I have just presented
it in a way that I hope may be attractive enough to cause you to give a try
to making one. I have tried to explain in such a way that you can picture
the finished aerial in your mind.

If you are unwilling to construct an aerial that resembles a Union Jack
flag in wire, you CAN build it so that all sections lay alongside of each
other BUT ONLY if the insulation is retained on each wire component. It
wont work quite as well as the described aerial but it will work.

I have used 75 Ohm Co-axial Cable in place of the twin feeder and it still
worked surprisingly well. Once you are satisfied that it exhibits low SWR
(standing wave reflection) at each frequency it is cut for, you can just
get on and use it without the need for an ATU (antenna tuning unit) except
for at the band ends. I am of the opinion that far too much fuss is made
about SWR measurements that hardly deflect a needle of a meter. You can
fire up into an SWR of 3.0 and there will be hardly any difference in the
received signal at the other end of the contact!

Your Transceiver will soon let you know if things are not quite right!

I might have been extremely lucky, but I just made mine, stuck it up, ran
the twin feeder to my transceiver (Yaesu FT 401-DX) and started using it
straight away with good effect.

I DID have a good earth rod though, driven into the ground to a depth of
six foot (6) which I would advise you to have no matter which type of HF
wire aerial you use. On the night that I worked Easter Island, I called
many times without getting a reply. So I went and sprinkled a packet of
salt over the top of my earth rod and splashed more than ten washing up
bowls of cold tap water over the area. When I returned to my station and
called again, I was answered immediately and Hector said how pleased he was
to hear and work a G station. We exchanged reports of 5/5.

The reader is expected to resolve his/her own problems and the writer does
not accept any responsibility for wrongful use of the information provided.
All information is supplied in good faith.

Get cracking now… and good luck with your CQ calls!

This article by Mel Fisher G4WYW, was found on
http://www.southgatearc.org/articles...tri_bander.htm

The post An effective 3 Band Wire DX Antenna appeared first on IW5EDI
Simone - Ham-Radio.


///////////////////////////////////////////
HF antennas for high rise dwellers

Posted: 04 Oct 2017 12:46 PM PDT
http://www.iw5edi.com/ham-radio/2288...-rise-dwellers


If you have ever tried transmitting on HF from a tall block of apartments,
where its just not possible to erect a substantial aerial system, then this
article is for YOU!

If you have never had to try…consider yourself extremely fortunate!

The limitations imposed are not so much that of limited space (although
this can be a problem) but strict Rules and Regulations that prevent the
erection of any beam or vertical rod aerial.

However, the very fact that the signal is going to leap into space from a
good height above ground can be, in certain respects, a bonus, so all is
not lost.

It IS possible to install an aerial…a wire aerial and using low power to
enjoy some interesting contacts. The satisfaction of making contacts can be
most rewarding.

What we need to do is be a little sneaky here. By this, I mean that we
should just fit a length of wire, discreetly, tune it up and have a go!
Perhaps you have already discovered or learned from others that applying in
the normal way for permission will, almost certainly, result in the request
being denied.



Let us now consider a few things obvious to some but which may have never
occurred to others. A thin gauge wire against a pebble-dashed or concrete
building, when fairly high above ground, will go virtually un-noticed,
providing it is fixed into position quietly, during darkness and does NOT
cause any flickering of neighbours television screens while they are
watching Coronation Street!

The key factor in NOT giving any interference is in using an ATU (Antenna
Tuning Unit) AND a Low Pass Filter which should allow low HF (High
Frequency) signals to pass through, as we want these to radiate, but should
suppress any VHF or UHF (Very High Frequency and Ultra High Frequency)
signals or harmonics from the lower frequencies which could cause
interference to television reception. One of the Golden Rules in
determining this is that should you be giving yourself any flickering on
any television channel then you can be fairly certain that a neighbour is
also getting it and that is not acceptable!

Keep it simple!

A true Long-wire would be several full wave-lengths at the operating
frequency. Such an arrangement is impractical for our requirements and in
any case would fire straight off the end heading into space or down to the
ground! What we are seeking is to send out a lobe that covers an area of
the planet likely to include other radio amateurs.

Ideally, we should use a length of wire that is at least a quarter
wave-length long, but preferably longer, at the lowest frequency we wish to
operate on. This would mean a wire at least 130 feet long for Top Band or
1.8 MHz, but in practice I suggest that you aim for a length of 90 feet or
as much as you can reasonably get away with.

As shown in the diagrams, #12 or #14 gauge wire is suitable because it will
be strong enough yet hardly be visible. Stranded wire is preferable to hard
drawn (solid) copper wire as it is more flexible and resistant to fracture
from movement in the wind.

The Vertical will radiate the best pattern, so this would be my first
choice.

If you have access to the roof, with the help of your wife or friend, lower
a length of twine or strong nylon fishing line down to the point where
someone is able to grab hold of it and pull slack into the room or balcony.
Now join this line to an end of your wire. If using nylon line which is
slippery, tie a knot using several turns and tape around the end to stop it
from slipping and becoming free!

Once the end of your wire has been pulled up and your assistant has grabbed
hold of it, go up to the roof and get the end fixed into position as soon
as you can. This may involve some leaning over, so dont attempt this if you
are nervous of heights and if you do attempt this TAKE GREAT CARE!

You need a strong support point which in turn will invariably require the
screwing in to the masonry of a hook, screw or masonry nail. Any of these
is going to require either a short burst with a masonry drill (battery
operated portable drill) or several taps from a hammer. I would prefer the
drill myself. (If it were me doing this, I would be inclined to do this
fixing one night and then wait several nights before pulling up the wire
and attaching it to this fixing). I would feel inclined to attach a wrist
strap to any drill, hammer or tools used for this task rather than risk an
item slipping from my grip and dropping. TAKE THE GREATEST CARE!

The observant among you will have noticed that in the diagram, I suggest
the use of Blue Tack to keep the wire away from the actual structure and
stop it flapping about. This should only be a temporary step until you are
satisfied that this can work for you. The best method of support is to use
TV stand-off insulators at the far end (top) of the wire and two or three
along the length. I appreciate that this might not be possible unless you
are friendly with the dwellers in apartments between yours and the roof.
Before fitting anything permanent though, I would want to make sure my
aerial is going to work, so a cable-tie from wire end (small loop) to the
fixing screw/eye will be fine for tests.

If there is a drainpipe running down the building and close to your
apartment, you might want to consider passing your wire through a length of
thin plastic pipe and secure this to the drainpipe where, if it is the same
colour, it will look like part of it. Keep an eye out though for
maintenance workers and if you see one showing more than a passing interest
in your pipe, offer him a cup of tea and biscuits and explain your
dilemma…hell probably wink at you and say no more!

There are no hard and fast rules regarding working out length except as
said earlier, this wire should be longer than a quarter wave-length at the
lowest operating frequency. Use this formula to work out how long your wire
needs to be at the lowest quarter wave frequency:

L (length) = 234/F (frequency in MHz)

/ = Divide

As an example, suppose you wish to operate the wire at 14,250 KHz (14.25
MHz).

Length = 234 / 14.25 = 16.42 or 16feet 3 and a half inches. (Approx)

Because your wire will be end-fed, it is going to have high impedance so
you will need a tuner and SWR meter between the end of the wire and your
transceiver.

See the diagram for details of how to make a simple tuning device that
should tune up any random length of end fed wire. Using low power, say 5
watts or less, then any tuning condenser which has vanes, removed from an
AM Wireless, will do the trick. Just remember that the wider the gap
between vanes, the higher the power it will handle.

For the variable inductance, if you can find a roller-coaster at a Radio
Rally, that would be ideal. Failing that, make a former about 2 inches
diameter (kitchen roll core?) and around 6 or 7 inches long (why doesnt
this guy use metric?) and use #14 gauge or thicker.

Wrap your wire around the former with a gap of a sixteenth or eighth of an
inch between turns. When using the finished coil, a short lead with
crocodile clip (as shown in diagram) can be used to change contact from one
part of the coil (inductor) to another. Experiment with different
combinations of coil coupling and tuning capacitor settings. Make a written
note of which settings give best match for given frequencies.





NEVER MAKE ADJUSTMENTS OR COME INTO CONTACT WITH THESE PARTS WHILE
TRANSMITTING RF!

I knew a Radio Amateur who lived in a tall block of flats not far from
where I live. He tried many frequencies but found he could achieve
excellent results from the 40 Metre band. This was the band he used until
he became Silent Key. He found he could have regular contact with UK
stations and European neighbours during the day time. In the evenings and
particularly in the early morning (0100+) he could work DX and had
confirmed contacts from as far away as Tierra Del Fuega which is down by
Cape Horn at the tip of South America. Eric accepted his lot and was happy
to be able to work anything at all. His aerial was a wire around his living
room skirting board under the carpet! He used CW and less than a couple of
Watts for all his contacts!



Inverted Vertical

Choosing which of these two aerial methods to use will depend on how high
in the apartment block you live. You could try both of them. The simplicity
of this second way is that you can easily lower your wire, with a small
canvas bag of sand as a weight at the bottom. This will keep your wire
straight while you are lowering it and also keep the wire from swinging too
and fro once its in the final position. You could also use a section of
broom handle or similar with a V notch cut in one end to keep your wire
away from the building structure. If you feel particularly paranoid, you
can lower this when it gets dark, use it, then bring it back up before
going to bed.

There is not much else for me to tell you, but I always get a feeling I may
have forgotten something!

Ah, just remembered…should you fail to achieve a low SWR (standing wave
reflection) no matter what you do, you may wish to consider using a
counterpoise. This is, in effect, the second part of a half wave dipole so
if you want to give it a try, cut a length of wire equal to the length of
your main aerial. Connect it to the Earth/Ground side of your tuner and
spread the wire along the corridor and under carpets in your apartment.
This can be insulated and can improve your signal considerably. What it
does is provide the simulated ground which is missing because you are
living so far above it!

As with my previous article, readers must be prepared to solve their own
problems. There are plenty of books in the Library or at your local Radio
Club that will give additional information on these and other designs. I do
NOT pretend to be an authority on the subject, so please just accept these
humble offerings as an incentive for you to try things out for yourself.

You must also take responsibility for your own actions as neither myself,
the Website Author should be deemed responsible for any use or misuse of
this information or for being the cause of any adverse circumstance!

Si fallatis officium, quaestor infitias eat se quicquam scire de factis
vestries

(If you fail, the secretary will disavow all knowledge of your activities)

This article, by*Mel Fisher G4WYW, was found on
http://www.southgatearc.org/articles.../apartment.htm



The post HF antennas for high rise dwellers appeared first on IW5EDI Simone
- Ham-Radio.



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