The working end of one of my experimental 2.2GHz
Yagi aerials made of 2mm brass rod, cable ties and glue!
MAKE YOUR OWN "COAT HANGER" AERIAL NOW ON THIS PAGE
Home made 3G aerials
Connecting from a static location is rather different
to using your dongle when out and about. When in a fixed position it is
possible to use a directional Yagi type of antenna array - that's a small TV
aerial to you and me. This design was invented by a Dr. Yagi in Tokyo in
1926 and now used on almost every rooftop in the world. The good thing is
that 3G broadband uses much higher frequencies than TV so the aerial is
correspondingly much smaller (frequency α wavelength), in fact a good one
can be less than a foot long. You can see a couple of pictures of my
prototypes on this page. To make one similar you need smaller parts than for
a telly aerial and a model shop should have all the necessary metal (except
the plug, which you can also make, see below) for under a tenner. Not bad
when 3G Yagis are sold for up to £200 on some web sites! (The manufacturers
sometimes hide them in a plastic pipe to make their device look more modern,
but inside it's just bent metal!)
I have now made several Yagi style aerials for 3G
using modelling brass strip and most work well, but to be honest none as
well as I would hope, so it's still a work in progress. In theory a good Yagi
tuned to the correct frequency could give a 15dB gain, mine give about 9dB,
but that is still an increase of 10 times or going from one bar to 5 bars so
still thoroughly worth doing! The lack of signal
strength may be down to my building accuracy. The director strips need to be cut and
placed to an accuracy of 1mm or less. Such tightness comes hard to a
spectacle wearer, but I'm working on it and hope to improve signals a lot
before publishing my design. However I have read reports that some of these
expensive units sold on eBay don't work that well either. I have recently
built a simple flexible whip (a bent cloths hanger) and this works
surprisingly well, with the advantage that a whip aerial can be put on a
rooftop easily and left outside
when it rains.
Further down I will describe my simple Yagi aerial but must
point out that the design may well be modified in the light of experience.
The "bent hanger" whip will be the next item on the page.
'n cheerful" CRC9 Huawei 3G dongle aerial plug
More drawings are in preparation - please look back
in a week or two
A couple of my early prototype plugs without cable
An adapter to fit an Huawei dongle to a standard aerial
Before you start you need to be able to connect to
your broadband dongle so first I will give you my simple cheap design for a
plug to fit the aerial socket on Huawei 3G dongles. You can use these
plugs to connect your experimental aerials. I haven't seen this size of
plug - called CRC9 - for sale at less than £5. My design, which I have now
repeated many times costs perhaps 20p in parts and works pretty
perfectly. It may not be as beautiful
to look at but who cares - it works, and if you drop it on the floor and
lose it then just
To make a plug the size of a CRC9 to fit the
Huawei socket you will need, a small piece of thin brass from a model
shop, a 2mm drill (used for size so can be blunt!), a piece of tube from a can of WD40 or
similar - 2mm tube is often used for squirt aerosol products, then some
Araldite - preferably rapid cure, soldering equipment, and a small piece
of brass wire or failing that use some fuse type wire or perhaps even in
an emergency a paper clip. Plans below.
Cut a piece of brass to 6 or 7mm x 10mm. Roll this
round the blunt end of the 2mm drill as this will be slightly over size
and you actually need 2.2mm internal diameter to fit the socket. When
you make the cylinder it is helpful if there is a small gap left (in
other words not quite a complete circle) as this will make it easier to
"spring" and fit tightly. If your drill is a bit small you could of course
wrap a piece of paper round the drill former first to make its diameter
slightly larger. To the end of your newly made brass cylinder tin a small part for
easier soldering later without overheating and melting
the plastic. Cut off two "ears" from the corners of the end of the brass
away from the dongle to make a place where you can bend the centre wire
over without shorting out. Look at the diagrams and photos, they are
much clearer and to be honest you could do the job just by looking at
them without bothering to read these words at all!
Next cut the tube about a couple of mm long, this
is your insulator/spacer. Push a few mm of the wire through the spacer
and bend over the end. Chose a size of wire that is a firm fit in your
dongle socket, not too lose nor too fat. I used a piece of wire from a
capacitor, you might use some old fuse wire or brass wire if you can
find it. Fix this wire in place with a tiny blob of Araldite at the
"top" end away from where it will go into your dongle as you naturally
don't want to put Araldite in your dongle! After this has dried
push the spacer with its wire attached through to line up with the back
end lining up the wire bend with the two "ears" to avoid a short
circuit. Fix in place again with another small blob of Araldite. It's
worth making up several of these plugs at one time as it is impossible
to make a small enough blob of Araldite and anyway the parts will be to
hand. You can always use the best ones and junk the rest.
After this solder on your co-ax connecting cable
screen to the previously tinned brass strip, centre to centre, and then
cover the end up with a blob of Araldite shaped when almost dry to make
a handle to push and pull when inserting. Set this entire unit aside to
dry properly, 24 hours minimum.
Here is a tip. You should really ensure that the
wire is central while the Araldite dries - overnight is best - and it
might fall to one side while drying. I usually risk it and leave the
plug just slightly in the dongle socket while it dries. If you are going
to make several of these plugs then you might prefer to make up a small
fake socket or perhaps just use another piece of WD40 tube (unglued) to
hold it all in alignment. A little grease will stop the tube sticking
while the Araldite dries.
Finally cut the wire so that it protrudes about
4mm or so out of the end of the brass screen and there you are! A cheap
'n cheerful plug to attach your experimental aerials to your Huawei
The brass is cut to roughly this shape and then rolled into a
My attempt at a diagram of the plug design.
The WD40 tube is just used as an insulator.
2.1GHz Yagi antenna for 3G broadband
Now it's time to look at how you might make a Yagi
aerial (antenna) to improve your 3G mobile broadband reception. The
advantage of using a Yagi type of aerial is that first it is directional. By
its very design it will reject signals coming from the side - in this design
it will only accept signals coming at an acceptance angle of 35degrees. That
means that signals from the side at 90 degrees, or to a lesser degree from
the back at 180 degrees will be at a much lower level than those from the
This is a neat way to help with the problem described
above when there is a source of interference at the side or back. So why try
my "device" and why not use a Yagi for every purpose? The answer is the
connecting lead. You see it attenuates or reduces the signals - a lot! If an
aerial gives a gain of say 12dB (that's a lot in this design) then after
going down a 10 metre lead of normal quality you will actually end up with
less signal at the plug than using a small whip aerial with a one metre
If this were a TV reception problem then we might
consider a device called a pre-amp. This sits right on the back of the
aerial and amplifies the signals before they go down the lead. That wouldn't
work on 3G broadband as we need to send signals in both directions, both up
and down. A suitable two-way device could be designed but it would be both
difficult and expensive to build ourselves! Anyway, we will describe here
the design of a Yagi and leave it to you to put it on the shortest low loss
lead possible. I recommend that you use 2 metres of cable maximum if at all
possible. Using really good quality cable you will lose about 1 bar per
metre of cable. This means that if you put the dongle right on the back of the aerial
and get 5 bars signal, 2 metres away you would only see 3 bars.
So keep the aerial lead as short as possible and use an extension (possibly amplified) USB
The quarter inch (6mm) square metal strips that we
will use for the centre spine of our aerial are sold by model shops in 30cm
lengths so we will design an aerial to fit on such a back bone after
allowing an inch or two on the rear end for a mounting bracket. To build
this antenna you will therefore need a single length of 6mm square box
section brass and several lengths of 2mm solid brass rod, also some solder,
plumbers solder is best, some flux for tinning and a hot soldering iron or a
blowtorch. If you don't have a blowtorch available then you can stick most
of it together with Araldite and leave the soldering just for the cable
connection to the active element. Alternatively use your gas cooker when
your wife is out! Total price for the metalwork is about £5 or £6. on top of
this you will need some suitable co-ax lead (details of how to obtain this
cheaply later on) and one of my famous home made Huaweii dongle plugs! Total cost for the
whole thing, less than £10! This setup can increase your signal level from
no bars to 5 bars. It really does work!
Again I will stress that you should connect this
aerial to your dongle by the shortest lead made of the highest quality
cable. Ideally less than 2 or 3 metres long, use anything over 8 or 10 metres
and even with the best cable available you'll end up with less signal than you started with! So if you have
plans to put this aerial on your chimney consider putting your dongle under
the slates on a long amplified USB extension. In the past it wasn't possible
to run USB devices more than a couple of metres from your computer. Now that
amplified extensions are available this can be increased to 10 metres by
putting two 5 metre leads in series. The manufactures of the extensions
claim that you can daisy chain up to 5 leads together to get 25 metres away.
In our experience no computer can supply sufficient current through its USB
socket to run so many amplifiers plus a dongle. You could try a self powered
USB hub but we still doubt that 5 leads in line would work.
If you absolutely have to get this far away from your
computer then use a device called an Ethernet USB extension. This uses two
special adapters at each end and a normal network lead in the middle - up to
30 metres does work, and up to 60 metres may work. The one drawback (apart
from cost) is that with a high current device such as a 3G dongle you
absolutely have to have mains power at the far end of the connection. Hardly
convenient on your roof in a a rain storm!
Here are some sizes to get you working on your home
built 3G aerial.
You will need something to act as the centre spar of
the aerial. It is interesting that this plays no part in the actual workings
of the aerial but I used 3/8" square brass section. You could use any metal,
plastic or even wood. Obviously brass takes solder so if you use non
solderable spar then you can glue the elements on, should make no difference
to the final result. The elements (these are the bits of metal that go from
side to side) can either go through the centre spar by drilling or can be
mounted on the side of the spar. Again this makes no difference.
(May 2012, still
working on the site - more soon)
"Coat hanger" aerial
made from the contents of your rubbish box
I have hesitated from publishing designs until
I felt they were easy to make, were reproducible and above all that
they worked! I have now built a half dozen "coat hanger" aerials
that should give you a useful increase in signal strength if you are
struggling to get a good mobile broadband signal. I am not saying
that this design will make a huge difference but you should get a
decent increase and if you make the design as described it should
cost you less than £1 GBP in total, so hardly a huge outlay even if
you throw it in the bin in the evening!
A piece of thick wire (an old wire coat hanger
thickness is ideal) This must be able to be soldered at one end so
steel or copper wire is best.
A large heavy washer to act as the ground screen, the thicker and
heavier the better!
A small piece of wood to act as a base. You could also use any other
sort of non-conductive material but it needs to be fairly heavy to
stop the whole thing falling over!
You will also need the real thing or one of my plugs shown elsewhere
on this page.
Finally a metre or so of screened wire ideally a type suitable for 2GHz (TV aerial
or satellite wire is a bit thick and inflexible but would do at a
pinch). Do not use more than about 1 metre length or you may end up
with less signal than you started with!
You will also need some simple tools, an
accurate ruler, pliers, wire cutters etc., and a drill or piece of
dowel to act as a former. If using a drill to wrap around it can be blunt. Glue of
some sort is also needed, Araldite or hot melt glue would be ideal,
the stuff from the 99p shop is fine.
I am going to give you the sizes for an aerial
to help increase signals with a Three network dongle. As this uses
its own specific frequency you won't get such good results if you use it
on Orange, O2, or any other networks in the UK.
Start by straightening the wire and then cut
to a length that you can work with, about 50cm is a good place to
start. I cannot be more specific as it all depends on the thickness
of the wire that you are using. You have to make two coils in the
wire, both of two and a half turns. So you will have to experiment a
little to get it right, start at the bottom end bending and
measuring as you go and then cut the final 10cm. The three lengths
shown on the diagram are important, the wire thickness is far less
so. You now need to start measuring and here accuracy is everything,
so measure twice and bend/cut once!
To make it clear the 6cm, the 9cm and the 10cm
are important, but you will need to work out how much wire is needed
for the two two and a half turn coils. I have guessed that you will
need a total of about 50 cm. With the coils having an internal
diameter of 1cm using pi seems to equal 8cm for each coil. Is that clear?
I hope so!
Right, you have cut your wire and now need to
put in the first of the coils which starts 6cm from the bottom end
but the wire may be a bit longer if you want to push some wire into
the base. As long as the washer sits 6cm from the bottom of the
bottom coil then the matching will be fine.
As mentioned the coils have an inside diameter of 1cm so using an old 1cm
drill as a former would seem the easiest. If desperate you could use an old
wooden spoon handle as I did for one of my early efforts! The coils
are 2 and a half turns, no more, no less or you will not get a good
match. The photo should make it all clear.
Next attach the centre of your connecting wire to the
6cm point at the bottom end of the aerial wire. You really need to solder this to get a good
connection, any thing else would be a bodge.
Pictures above of one of my experimental designs to give an
idea of the manufacture of the coil. The centre picture also shows
the gap between the two coils. I used some plastic covered garden
wire for this aerial. The wire inside was a lovely rusty steel wire
that after it was cleaned up took solder beautifully. This for a correspondent who asked for
more info. Sorry, I have had health and technical issues lately and have lost the
original message. The main point is that the coil should be central about
the upright. If you off set the coil the sensitivity will not be
unidirectional and you would have to twiddle the aerial round for
best reception. By the way you can try putting your aerial at
45degrees rather than dead upright, this can increase signals by 1
The next step is to get a signal from your new
aerial into the dongle. As I mentioned previously you really need to
use a low loss flexible cable which is not so easy to get hold of so
here are a couple of suggestions. I managed to get hold of a 9 metre
Wi-Fi aerial extension lead complete with plugs for just £3 on eBay.
Unlike an aerial which has to be made for a certain wavelength or
frequency connecting wire designed for a slightly different
frequency will work perfectly on 3G. Just cut to length (as short as
possible remember - 9 metres is far, far too long), attach one of my
simple plugs (or buy the right thing) and solder the other end to
the aerial. If you don't want to go down the eBay route then believe it or not a simple screened lead
that is used for audio will work after a fashion as long as you keep it as short as
possible - not more than a foot or two will at least give you
something to experiment with. I always keep an eye on the rejects box
at my local supermarket and buy any unboxed incomplete audio or
video leads and accessories there. I have picked up unwrapped switch boxes
with useful switches and wires inside for £1 and incomplete audio or video
lead sets for 50p!
I will look in the Maplin shop the next time
that I am in the area (which is when I visit the hospital) to find a
suitable lead part number that I can recommend and will report back
Now we move onto the base of the aerial which
needs to be able to support the thing without falling over. This
is made by drilling a small hole the same diameter as the wire. You
stick the end of the wire into this hole to make the aerial stand up
(doh!). Now the clever bit is that you then put the largest heaviest
and largest steel or other heavy metal washer that you can get hold
of to the top of the block of wood or plastic that you are using for
the base. Look at the diagram (on the way) to see how this all works.
The centre of your connecting wire is attached to the bottom end of
your aerial wire and the screen of the connecting wire is attached
to the washer. The washer MUST NOT make physical or electrical
contact with the aerial. In this way the washer acts at the electronic base against which the
signal "pushes" out. Solder the screen of your wire (that's the outside
of the wire) to the washer and the centre of your wire to the bottom
of the aerial
itself. You can if you wish make the bottom part of the aerial
(that's the 6cm part) a little longer and use the extra as the part
that you push into the base. As long as you attach the connecting
wire no more than 6cm from the bottom coil the aerial sees just this
part and the matching is not affected. To make this clear the washer
is placed 6cm from the bottom of the bottom coil and the circuit
simply ignore the part that is stuck into the wood. Hope that's
clear! Later on I will suggest ways to tune the
aerial to the exact frequency. You do this by lifting the washer up
and down nearer and further from the bottom coil. This is quite
difficult (for example you have to move your hand completely away as
you adjust so you can't just hold it and watch the signal level) but
getting it right can make a real
difference in gain so I will write a separate section to clearly
explain how to do this. Using the above figures will give you good
gain without any fine adjustment, so it's up to you.
How large should the washer be? The larger and
heavier the better - it must be of conductive material, steel is
best and wider is better than thicker. Some large washers are
galvanised to go on roofs. To use these you will have to file off
the coating and probably use some extra plumbers flux to get a good
soldered connection. The picture shows the wire screen attached in two
places, this is really to ensure a good electrical connection which
JULY 2012 - MORE DETAILS
p.s. For heaven's sake put something on the
top end of the wire (a blob of hot melt glue perhaps) so you don't
stick it in your eye!
p.p.s. Our local 3 transmitter went off the
air last week and I used one of these aerials to connect to a base
station that is 5 or 6 miles away. I got 2/3 bars with the aerial
connected and no bars without. In fact I had
to connect the aerial before the dongle would fully connect. So the
Sorry, cable has all gone.
p.s. I am not a business and only have a few metres spare
anyway so I can't supply large quantities at this price.
These are electronic devices that, believe it or
not(!), amplify or boost the signals down from the mobile base station and
then boost your data before it is sent back up. It's quite difficult to make
a suitable unit from scratch, but much easier to modify existing devices
such as those made for Wi-Fi to work at the adjacent 3G frequencies. We have
tried modifying an amplifier sold for wireless internet frequencies to
the 2GHz frequencies used by 3G. This does work after a fashion but we are
faced with the problems mentioned above of increasing the interference just
as much as the wanted signals. It is perhaps for this reason that there
seems to be a dearth of professionally made 3G boosters in this country. In
the wide open spaces of the USA and Australia though it is a different
You can make a start and can easily get a femtocell
amplifier for many mobile phone providers but that is not really what we are
looking for on this web site. We are looking for a long term reliable
broadband signal rather than occasional short term phone calls. We are
working on the problem...
brew 3G software to make the best use of what signals you can get
for example by combining two connections into one. When one goes down the
other may well get better! I have one example running at present although
it's not yet good enough to publish.
to boost 3G dongle signal that I have tried
(WORK IN PROGRESS JANUARY 2012)
I am now able to give one easy and practical
suggestion of a way to boost the signal when using a 3G dongle.
You need an unused Sky type satellite dish although I
have been experimenting with an old BSB dish which is smaller than your
average Sky dish and this works well. One problem is that the larger the
dish the more accurately it needs to be pointed so for this application
smaller is sometimes better! To make this system work properly you must also
know exactly where your 3G signal is coming from as you will be pushing all
your signal in that one direction. Even a few degrees off beam will make
you signals far worse than they are now.
Sky dishes are offset, that is they are designed with
the focus off centre so you must point the dish far lower than normal. This
may well involve modifications to the mounting clamp - more about this
later. As you will be transmitting from the dish as well as receiving you
should look for a dish that has a smooth surface with no obvious defects or
dents. You can get hold of dishes that are solid rather than perforated - if
you can then one of these is recommended. Remember though an unperforated
dish will have a much higher wind resistance so will need fixing that much
more securely. You will not want to be responsible if it falls on someone's
head! If you are reading this abroad then a small c-band dish should be
If you are using a dongle of the Huawei type, which is
the make that I am most familiar with, then the most sensitive part is at
the end furthest from the connector. I have found (rather surprisingly) that
you get by far the best signal if you mount the dongle at an angle of 45°.
Push the dongle through the ring that is normally used to mount the
satellite L.N.B. which is not needed for this application. If using a
different dongle then try mounting it upside, downside or inside out - try
Everything must of course be waterproof. I have placed
my dongle in a small Tupperware type drinks container which happens to be
the same diameter as the old L.N.B. Gaffer tape seals and holds it all in
place for now while I experiment.
You must mount the dish reasonably close to the
computer - certainly whilst setting the whole thing up - but it should never
be more than 5 metres away. This is not a system where you can mount a dish
on your roof and run a long wire down the wall, as you will certainly lose
more signal than you gain, To get the signal to and from the computer I
recommend that you use a 5 metre amplified USB extension cable which can be
bought for £10 - £15 in the U.K. As you are transmitting you need as much
voltage as possible to reach the dish, so an ordinary 2 metre extension lead
should be avoided.
By the way if it is essential there IS a way to get
round the distance restriction mentioned above, but it involves turning the
USB signal into a network IP signal with an adapter at each end as well as
providing a mains power supply near the dish. Expensive and a fiddle, but I
suppose do-able if you must.
I get between 0 and 1 bar with the dongle hanging in
the air and a full 5 bars signal when properly mounted in a well sited dish.
This system really can make an enormous difference perhaps when travelling
(although you would need a map of the nearby transmitters). One rule still
applies that is that whilst you will probably not be able to get a line of
sight signal you really still need to avoid walls, thick foliage etc. These
things still attenuate the signal whether the dongle is inside a dish or
A quick look at the diagrams (which I hope to have
ready very soon) will help make everything clear.
Oh a quick p.s. For some reason this scheme does not
seem to work well when using the Mi-Fi type of adapters that include a built
in wi-fi connector. I have absolutely no idea why this might be although it
may be that these units are not made as sensitive as the normal Huawei
dongle. Pity as I find my Mi-Fi invaluable when out and about.
Please do get in touch if you need more help.
LOTS and lots more to come including some hard
details, plans and hopefully some details of when you can get suitable parts
cheaply. Please look back. Always pleased to hear from you.
p.s. There is a video on YouTube showing a booster
that uses a saucepan. This quite simply does not work and I can't see how it
might work - unless the signal is coming from directly above! There are many
videos on YouTube that are complete cons - don't fall for 'em!
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