IW5EDI Simone - Ham-Radio

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How to build a tuned loop antenna

Posted: 13 Apr 2020 01:42 PM PDT
http://www.iw5edi.com/ham-radio/3822...d-loop-antenna



How can you vastly improve your Medium Wave reception? its quite simple
really, all you need is 120 foot of wire, a few lengths of timber and an
old tuning capacitor with which you can build the answer to every DXers
prayers, a tuned loop antenna.








This simple Do-It-Yourself project, which will probably cost you no more
than £10, will enable you to improve the clarity of reception on
medium-wave radio stations to an unbelievable level.




NOTE: This graphic of the tuned loop antenna is slightly different from the
one described here in the building instructions, in that it has a central
leg on which to stand, this is only a cosmetic feature and is not necessary
to the better reception of a radio signal.




The results of these amazing antennas really and truly has to be heard to
be believed. So how do I build one? I hear you ask impatiently. Ill keep
you in suspense for a few minutes, firstly Ill explain a little of the
background of the tuned loop antenna.




What is a Tuned Loop Antenna?

The loop antenna is designed primarily for the AM band, which utilises the
530 khz to 1620 khz section of the radio spectrum.

Indeed there are two different types of loop antennas, The first of these
is the ferrite bar as build into practically every portable radio, the
other is wound on an air-core form, and is far less popular with radio
manufacturers because of its size, this is known as a tuned loop antenna.
A loop antenna is very directional. The pickup pattern is shaped like a
figure eight. The loop will allow signals on opposite sides to be received,
while off the sides of the loop the signal will decrease or be nulled out.
The nulling feature will allow you to remove a local station on a frequency
and pick up another on the same frequency by removing the local signal.

For example, I could be listening to Magic 1548 from Liverpool on 1548 khz
from my home in Ireland, also on that same frequency I can faintly pick up
some music and chat from another radio station on the same frequency, so I
turn the loop antenna around slightly in the general direction of this
other radio station and as if by magic, I can now hear a very clear signal
from this other station which turns out to be BBC Radio Bristol, at the
same time the signal from Magic 1548 has faded somewhat into the background
mush.

Air core loop antennas come in many sizes. The larger the loop the more
gain there is. A smaller loop will actually lose part of the signal. There
are two ways a loop can be wound, box or spiral. In the box or solenoid
loop the plane of the windings are wound perpendicular to the diameter of
the loop, so each loop is the same size. In the spiral loop the plane of
the windings are wound parallel with the diameter of the loop, so each loop
gets smaller as you wind into the centre of the loop. A loop needs to be
able to rotate to null out a station. And a loop also needs to be able to
tilt from vertical. This also helps in in nulling of a signal (alt-azimuth
feature).

The number of turns the loop needs is determined by the size of the loop,
the frequency range that you want to tune and the value of your tuning
capacitor. The larger the loop the fewer turns you will need. A 4 foot loop
needs 8 turns and a 2 foot loop needs 18 turns. The capacitor that is used
is the standard AM tuning capacitor with a range of 10 to 365 pf. The
tuning capacitor is used to tune the loop to the frequency that you want to
listen to. When you are tuned in to the frequency the signal will peak. You
may not be able to tune the full frequency range that you want to tune. So
you will need to use a 2 section capacitor and switch the second section
in. (more capacitance)

There are three ways that you can connect your loop to your radio.

One way is not connecting it at all, this requires a portable radio with a
internal loop antenna in the form of a ferrite rod. The field of the loop
will radiate the peaked signal and you will be able to pick it up with no
connection to the radio. You can move the radio around to get the best
reception.

The second way is to get a direct coupling to the loop which is used as a
pick-up coil, This consists of one turn of wire wound around the
circumference of the loop, this is then connected to the radios antenna
socket by means of a removable flying lead.







The post How to build a tuned loop antenna appeared first on IW5EDI Simone
- Ham-Radio.


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QSL Maker

Posted: 13 Apr 2020 01:35 PM PDT
http://www.iw5edi.com/ham-radio/3819/qsl-maker



This nice software, developed by WB8RCR let you design and print your own
QSL cards, allowing to personalize background, by importing pictures or
just filling with a plain color, and let you personalize headings and
address as well as your own callsign.








It can import ADIF log file for fields auto-filling during the print
process, or allow you to insert directly QSO Data into a table.




It runs on Windows, Ive tested it on Windows XP, and is completely Free !









Download QSL Maker 2.4

The post QSL Maker appeared first on IW5EDI Simone - Ham-Radio.


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Fabricating CB antennas

Posted: 13 Apr 2020 01:31 PM PDT
http://www.iw5edi.com/ham-radio/3814...ng-cb-antennas



Citizens Band frequencies are at the top end of the high-frequency band, or
stated another way, just below the bottom end of the VHF band. Here is
where base-loaded CB antennas usually work well. A mobile antenna should be
placed in the middle of the vehicle roof to make best use of the ground
plane. The longer the CB whip, the better the performance. The more you
load an antenna, the shorter it gets, and the lower the radiation
resistance. Lower radiation resistance means less signal output and input.
Select the tallest antenna possible and put it as high as possible.










Phased Two CB Antenna System




You might also consider a phased two CB antenna system to give an
additional 3dB of gain. You can purchase co-phase coaxial cable assemblies,
or make your own using a coaxial cable T-connector and two equal lengths of
RG8AU coax. Make sure that each side of your co-phased coaxial cable feed
lines are identical in length, down to a fraction of an inch, but be sure
to avoid a precise half-wavelength on 11 meters for your phasing harness.
Mount the antennas on either side of your vehicle. The best performance
will be to the front and rear of the vehicle, with slight nulls to each
side of the vehicle.






Unloaded Whip




The easiest way to get the strongest signal out on Citizens Band is to use
an unloaded whip CB antenna. You may purchase these stainless steel or
fiberglass whips at any CB Radio store. Mount the whip as high on your
vehicle as possible. Because it has no loading coils, it will offer unity
gain without loss whereas you might expect a loss of 1 to 2dB from a loaded
CB antenna.






VHF and UHF Bands




On VHF and UHF mobile radio bands, the whips are so short that they may be
phased vertically in a collinear array to achieve increased gain on
transmit and receive. Why send half your signal into the sky when it can do
more good down close to the horizon? You can spot a VHF or UHF collinear
high-gain antenna by the loading coils in the center of the whip.





For VHF operation, a 5/8-wavelength CB antenna offers a low take-off angle
and may achieve increased gain of approximately 3dB over a conventional 18
spike on the roof. You can spot these antennas easily by a single yard-long
whip and a gray or stainless steel loading coil at the base.





For UHF operation at 400-500 MHz, a popular mobile CB Antenna is the
collinear halfwave-over-halfwave whip. Its about 20 tall with a sealed
phasing coil in the center, and offers increased gain over a little 611
spike. A car with one installed on the roof usually will still fit into a
residential garage.






Do-it-Yourself CB Antennas




There are lots of CB antennas out on the market today, all kinds of
different shapes and sizes. Because of this competitive market, companies
are always trying to put out a better product for a cheaper price.
Commercially-made CB antennas are usually easy to put up and maintain.
However, you might want to try your hand at making an antenna. You can make
an one out of readily-available parts that will work as well or better than
some commercially-made CB Antennas.





You will need an SWR meter to check out the Antenna after building it.






¼ Wave Ground Plane CB Antenna




This CB antenna consists of a driven element and four radial wires that act
as a ground. The driven element receives the transmit energy from the rig.
Parts List




104 (264 cm.) [I 02 (259 cm.)] piece of aluminum pipe or conduit
¾ 1 diameter
Two U-bolts, same size as pipe
One sheet metal screw
One J-hook
Four egg ceramic insulators
408 (10.22 m.)[400(10.2 m.)] of 16 gauge wire
Rope, enough to guy the ground radial, depending on the height of the
antenna
A couple of two-by-fours
Electrical tape
Silicone sealer to cover coax connection




1/4 Wave Ground Plane CB Antenna




The inside conductor of the coax is connected to the aluminum pipe by means
of a screw into the bottom of the pipe. See the detail drawing on this
page. Coat this connection with sealer or cover it with tape to protect it
from corrosion.





All vertical antennas need to be grounded in some way. A mobile CB antenna
uses the car body as the ground. On this CB Antenna, the four radial wires
are used as the ground. This is called the ground plane of the antenna.





The braided wire which forms the outside conductor of the coax is soldered
to all four radial wires. The wires must be exactly 264 cm (104) long [259
cm(102) long] (¼ wavelength).





Remember that the inner conductor and outer braid of the coax must not
touch each other, nor can the radials come in contact with the driven
element. The radials slope down at about a 45 degree angle in different
directions, and are tied to the insulators. Rope or nylon cord is then tied
to the insulators and used to hold the radials out. They can be attached to
anywhere convenient; trees, a fence, house, etc.





If you are short on room for such a radial system, you can use 104
(radials) and 102 (driven elements) pieces of aluminum tubing, or suspend
the wires on PVC pipe, bamboo, or 1 x 2 wooden sticks. Its a must to check
the SWR when done. It should be lower than 2, and ideally lower than 1.5 or
1.3.





A ¼ wave ground plane CB antenna made from wire can be suspended from a
tree. We have talked to stations over 40 miles away using this antenna up
about 30 feet high, running a mobile rig for a base.










Coax Cable Vertical CB Antennas




For a quickie CB antenna, a vertical dipole (1/2) wave can be made right
from the coax itself You take your coax and very carefully, without nicking
the braided shield, strip 102 inches of the outer insulation jacket off one
end. After removing the outer jacket, start bunching the shield down the
coax from the end. Now, where the outer jacket and the shield meet,
separate the braided shield enough to get the inner conductor out through
the hole in the braid. Pull all of the inner conductor through and stretch
it and the braid out. Be careful not to skin any of the insulation off the
inner conductor. Now attach an antenna insulator to the end of the inner
conductor. Measure the braided shield. Cut it off at about 106 and attach
an antenna insulator to the end. The total length of the inner and outer
conductor should be about 17 feet (1/2 wave). You can haul it up to any
height you want with a string or rope attached to the insulator on the
center conductor. Its a good idea to coat the end of the coax cable where
it separates with some kind of waterproof sealer. This keeps water from
seeping into the coax, which could cause a high SWR.





Just attach a coax connector on the end of the coax going to your
transceiver and you are on the air. The SWR should be 1.5 or better, if cut
to the proper length. Itll get out about as good as a ¼ wave ground plane
CB radio antenna if you get it up high and in the clear. Do not hoist this
antenna up next to a metal pole, because the metal will interfere with the
antennas operation and cause a high SWR.






Using a Mobile CB Antenna for a Base Station




A mobile CB antenna can be used as a base antenna by mounting it on the top
of a metal pipe. The metal pipe serves as ground connection for the
antenna, taking the place of the body of the vehicle. Remember to run a
separate ground wire to a proper grounding rod for lightning protection.






Building a Vertical Gain CB Antenna




This is an easy antenna to build and find the parts for. If you follow
these instructions and have it come out looking like these pictures, it
should have a very low SWR and appreciable gain.





You can use any number of pieces of aluminum pipe so long as they are
ridged and fairly thick-walled so as not to become bent and broken in a
strong wind. The pieces should be gradually smaller, one being able to fit
inside the next. Cut two 2 grooves with a hacksaw down the outer pieces of
aluminum and put a hose clamp around them. Now adjust the antenna to 22 ½
feet (6.85 meters) and tighten the hose clamps down to hold it all
together. This 22 ½-foot vertical element can now be mounted with two
U-bolts on to the 2 x 6 board. This board should be treated or painted to
protect it from the weather.





Put a bolt through the piece of wood a few inches below the vertical
element. Here you should fasten one end of the 6 foot (183 centimeters)
piece of copper wire or tubing, the outside braid of the coax and each of
the 104 (264 cm)[102 (259 cm)] long, stranded wires. These are called the
ground radials and should be tied off with string (not wire) at a 45 degree
angle away from the bolt. The ground radials and the braid from the coax
can be soldered together or can be crimped together with a crimp connector
that fits the bolt. The other end of the 6 copper wire is bent and fastened
to the vertical element. The end of the center wire of the coax is then
twisted onto this in such a way that it ca be slid up or down along the
copper wire and soldered after adjustment.




The SWR of this CB antenna is adjusted by sliding this connection. You do
this by keying your rig up on channel 20 and sliding this connection up or
down until you have the lowest SWR. In our experience, an SWR of 1:1 or 1
was easily reached on channel 20 with a low SWR throughout the 27 MHz band.





Be sure to cover the end of the coax real well with a moisture proofing
sealing compound so no moisture can get in it.






Fishing Pole EarA Homemade Mobile CB Antenna




While the next project wont necessarily save you any money, you might want
to give it a try if you are interested in understanding more about how
fiberglass whip antennas do their thing. We have talked 30 miles
mobile-to-base on one of these home brew fishing pole antennas using a $20
barefoot rig.
Antenna Parts




One 7-foot fiberglass fishing pole with hollow base One piece of steel rod
4 to 6 inches long-right diameter to slip into base of pole One ¼ x 1
machine bolt (threads to match mount) 12 feet of enamel #18 gauge wire Some
good epoxy glue




Antenna Mount Parts




One 114 x 21/z bolt and nut (same threads as bolt on base)
One longer-than-usual ¼ nut
Two plastic insulating washers
Three metal 5/8 diameter washers
One large terminal lug




First youve got to get yourself a fishing pole, 6 to 9 feet long. If you
already have an old one lying around, you can clip off the line loops and
cut the handle off.





We did some shopping and found that a finished fishing pole as long as we
wanted was at least as expensive as a newly-manufactured CB antenna. But
then we discovered a sporting goods store that sold unfinished fiberglass
poles 7-feet long for $6. The kind we found was a black hollow tapered pole
with about a 1/8 inside diameter at the base.





The next step is to hook something to the pole so you can screw it to a
mount on your vehicle. The way we did it was to get a piece of scrap steel
rod near the inside of the base of the hollow pole. (If the pole is not
hollow you will have to figure out another way of hooking to it.)





Grind a slight taper to match inside taper of the fishing pole. Braze bolt
to rod. Use 1/4 x 1 steel bolt. Epoxy the steel rod inside the base of the
fishing pole.





There are many commercially made CB antenna mounts that you can buy at
electronic parts stores that could be used to hold your fishing pole ear.
If you elect to buy one of these mounts, get one with a spring so that if
the pole encounters a stray tree branch, it can bend instead of break! If
you are going to use this antenna with a store bought mount, the threads on
the bolt on the bottom of the antenna should mate with the hole in the top
of the mounts spring. Tuning the Fishing Pole Ear




Now its time to get into the electrical part of the antenna. The fishing
pole is not the antenna; its just a prop that holds the wire up. So we need
to wind a wire around the fishing pole in such a way that will make it tune
the 27 MHz CB band





If your antenna is shorter than 9 feet long, you can tune it by winding a
coil around the pole. On our 7-foot ear, we found that it was necessary to
make a coil of four turns ¼ apart about 2- 3 up from the base of the pole.
Tightly wrap the wire in a spiral up from the base of the pole. Make the
distance between windings as wide as possible below and above the coil. If
you follow these particular dimensions you should be close to being tuned
up. To really make the ear a perfect match, however, youll need to use an
SWR meter to check the SWR. You may have to modify the coil spacings or add
or subtract a turn from the coil to get it just right.





Different lengths of CB Antennas will also work, but different coil
windings will be necessary, so if you have a different length pole youll
have to use a meter to tune it up. You just have to dive right in and try
different numbers of coil windings. The longer the pole, the less center
coil windings; the shorter, the more windings necessary. It takes some
playing around and trial and error.





We used enamel coated wire, the kind used in motor windings, generators,
transformers, etc. Its best to use enamel-coated wire so that the coil
turns cant possibly short to each other.





At the bottom, wrap the wire around the 1/4 bolt. Be sure to scrape the
enamel coating off the wire and clean the bolt for good contact. Solder
that wire to the bolt or use a nut to hold the wire onto the bolt so that
it makes a good electrical connection.





We covered some CB antennas we made with a thin coat of fiberglass (which
you can tint any color you want). They looked pretty good but the
fiberglass chipped off some of the antenna tips because they were mounted
fairly high up and got tangled in the trees. You can prevent chipping by
putting some shrink tubing over the tip. Shrink tubing would be another
possible way to hold the wire on the fishing pole. Its available at most
electronics shops.
Building a Fishing Pole Antenna Mount




If you are really adventurous, you can also build your antenna mount. The
main point to understand when making an antenna mount is that the radiating
element is not supposed to ground out to the body of the vehicle. This
means that the bolt the antenna hooks to must be insulated from the metal
body of the vehicle.





Your homemade mount must use good insulating washers, because if the bolt
shorts to the vehicle body it could possibly blow out your rigs final RF
power transistor.





One source of home brew insulating washers is the main output terminals of
junk alternators or generators. The washers should be made out of some type
of plastic. The best kind of insulating washer has a shoulder around its
hole. You drill a hole in the vehicle body, big enough to allow the
shoulder to fit through. This holds the bolt away from the metal body.





If you cant find a plastic washer with a shoulder, it is possible to use
two flat plastic washers with a little piece of plastic tubing in place of
the shoulder. Make sure the plastic is tough enough to not get cut by the
edge of the hole in the vehicle body.
Your base CB antenna system may be put up 20 feet higher than the highest
point of the building or tree on which it is mounted; however, the highest
point of the antenna must not be more than 60 feet above the ground. There
are additional restrictions on an antenna system located near an airport.
Consult FCC Laws Part 95, Subpart D for your particular situation.
sistance means less signal output and input. Select the tallest antenna
possible and put it as high as possible.

The post Fabricating CB antennas appeared first on IW5EDI Simone -
Ham-Radio.


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Attic Antennas

Posted: 13 Apr 2020 12:04 PM PDT
http://www.iw5edi.com/ham-radio/3809/attic-antennas



Attic antennas can work better than you might think, some of mine work as
well as their outside counterparts (no Im not comparing to a 150ft tower &
big yagis). The RF losses are fairly low in wood and most roofing at HF &
VHF, most of problem comes from interaction with electrical wiring and
ductwork. This creates deformation of patterns and sometimes high swr.




Another concern is to keep your power at reasonable levels, RF exposure to
your family and even fire are considerations. I would suggest no more than
100 watts on HF and 50 at VHF & UHF. Be careful to insulate your wires
especially at the ends for fire safety.



indoor loop antenna 17-40 mt




Â*TUNERÂ*




A good tuner will straighten out impossible interaction problems on HF
antennas, also they will provide multi-band operation on some
installations. Though lossy, a tuner can make the difference between
acceptable operation or frustration. Â*




VERTICALSÂ* Radials:Â*








If you are lucky enough to have a large attic take advantage of this and
lay out a extensive radial system, this is one area that you can do better
than an outside installation also the better the radial system the less RF
in your house. If you have a small attic do the best you can, dont be
afraid to bend to fit. Almost any size wire will work since mechanical
strength is not a consideration. Cut your radials to the 1/4 wave length
for your band(s).Â* Radiator(s):Â* On VHF & UHF full size and radiators with
gain should be no problem, but on HF usually shortened or loaded radiators
are yourÂ* only choice. Use the longest radiator you can get away with that
is at least a few inches away from the roof. Its OK to fold over the top is
you have to. If you can, add some tubing on top to turn it into a T for
bestÂ* pattern. Shortened 11m for 10m or Hamsticks for other bands work
well. Also several radiators can be installed on one mount for multi-band
operation with matching radials, but this does not always work because of
interaction between the bands.Â* Coax:Â* Use a good quality coax cable to
reduce RF & interaction problems. Â*Â* Â*





DIPOLESÂ*




There are a lot of dipoles in attics out there, the big limiting factor
here is the size of your attic. If you need more room consider zig zaging
your wire, just keep your turns at 90 degrees or more. Also commercial
multiband or shortened dipoles work well. Again run your dipole as far away
from metal as possible. Try not to have your rig right below your antenna
to reduce any potential RF problems. Feed line: A little care is needed
here, be careful of running parallel to electrical lines or ductwork if
using balanced lines. Use the best coax or twin lead you can but if you can
use 300 TV lead with some loss for easy routing.




Â*Â*BEAMSÂ*



VHF UHF Beam Antenna




On VHF a beam antenna can work well in the attic, even a rotator can be
used. Again stay away from metal and wires to maintain your pattern. On HF
wire beams can be run on the roof supports or the rafters, these usually
are good for one direction only but can be switched electrically for
different coverage.




Article by N0HC originally available at
http://www.geocities.com/n0hc/attic.html

The post Attic Antennas appeared first on IW5EDI Simone - Ham-Radio.