Homebrew aerial

[yarmouthshipping]

got mine from screwfix 2mtrs for £1.47

[Truetrack]

Hi Simon. Have you any wire coathangers?. They work fine you may have to scrape off the coating to solder it to the socket. I have used wire of hangers for all kinds of antennas. and hairpin matches for my yagis. Another way is twin and earth take the solid earth wire and use that (30 amp)

                                                                                                             Billko

Hi all - a bit OT but it fits to homebrew !

re wire coathanger, I love 'em
these are my favourite dispensable travel items
good for vertical dipoles, GP , Triple(quadruple) legs,
all easily exact tailored to your freq

all you need are a few coathangers
one or two coax chassis-sockets of your choice (4-hole)
a plier for cutting and sharp bending
a length of customized coax cable
and that's about it.

everyone goes SMA, but for these purposes I prefer the Bayonet-Neill-Concelmann = BNC
no screwing here! Just quick connect/disconnect.

In practice I had some 3 cms of 1.5mm solid copper soldered into the chassis socket
and clamp the coat wire to it and cut to length. I do not know how you call it,
a metal clamp with 2 screws to connect two ends of wire e.g. Mains, or in switching boards.
A little bent hook ontop enables you
to hang it most everywhere e.g. hotelroom-window shades or what not.
Into the 4-holes you can hook  the lower section of a dipol.
with clever bending you can form radials to be horizontal as in GP, or drooping 45 degrees
downwards, holding indoors simply by gravity.
It works - the contact betwween the metal is good enough for VHF/UHF Comms .

almost forgot that;
Formula (short Version)
75/freq(Mhz)= 1/4 wavelength (meter)

have fun experimenting

[yarmouthshipping]

Cheers Klaus

[yarmouthshipping]

how did you get on i cant get any reception thru mine i have checked and checked think i will save for manufactured one

[shakysen]

Hi Klaus.Take a look at this site (find one in english) http://f5ann.pagesperso-orange.fr/AntenneStrip-line1090MHz/index.html

                                                   Billko

[Truetrack]

Hi
tks, I had that french site previously bookmarked.
Have a look at AMOS-5
another and different approach this Franklin-centre feed type of antenna

BTW re etched PCB for antenna elements
one Juan Gelb of Brasile posted somewhere fotos
a/ of his homebrew collinear and
b/ a dismantled GP1090 this is also a slim PCB etched with 4 sections if I remember right.
sorry cant find the link anymore

[gutopohl]

Hi!!
Does someone know how to connect two 50 ohm antennas in one receiver and keep the 50 ohm?
My idea is put the demo antenna that's comes with microAdsb and my home brew high gain collinear antenna working together. 
Thanks.

[Truetrack]

Hi
well, when homebrewing at it, you could consider preparing a 1/4wavecoax-section as transformer.
with both antennas combined and such connected in parallel the resulting impedance is only 25 Ohms.
You can step this up by using a short length (quarterwavelength incl. velocity factor) of 100-Ohm Coax.
A bit tricky 1/4 WL = 6.88 cms , velocityfactor depending on cable 0.8 to .86 makes it only 5.5 to 5.9 cms length.

Formula
square root of (25 x 100) = 50 Ohms out.

So for practical reason use a T-Piece, center connected to Transforming section and
continue into your downleading coax cable.

so far the theory, question remains
are the different qualities of your antennas so prominent that the effort is justified
and not possibly spoiled by other factors ?

[gutopohl]

Hi Truetrack.

Thanks for your replay.

Let me try to explain what's happening.
A few weeks ago I built this project: http://www.wardrivingonline.com/equipment/antenna/omnicolliner-antenna-design.htm
I changed the length of 1/4 to 'feet' 1090 mHz.
The results are much better then demo antenna that's comes with microadsb but now I got a huge Doughnut affect.

Guto.

[Truetrack]

Yes that is plausible then.
All those multisectioned collinears whether industrially manufactured or homebrew
have these effect. They just focus the ring of lobe to the horizon, thus flattening it
like a doughnut.
One may use less elements resulting in less horizontal gain to a certain extent as a compromise,
and possibly use of expensive preamp and T-injection of power instead.

regards

[gutopohl]

Thanks Truetrack.

I will try to build the coax transformer using your formula. Right now buy an expensive preamp is out of context.

Let see what will happens!
Thanks again!

Guto.

[dongle]

You can make a pre-amp for about £4.

Take care how you feed in the power to it and make sure you provide a capacitor of maybe 100pf between the collector of the transistor and the input line to your receiver, else you won't do the RX any good at all.

Here is a really cheap one:

http://www.lll.lu/~edward/edward/adsb/preamp/ADSBpremap.html

Then you can buy this kit for about a tenner plus £2 postage:

http://www.g4ddk.com/SPFAMP.pdf

Here is another simple design:

http://users.belgacom.net/hamradio/schemas/preamp_HF_VHF_UHF_SHF_wideband_MAR6.htm

[JohnOCFII]

no, there is nothing more simple to that proven design

http://www.tech-software.net/1090_ant_02.JPG

Are there any additional drawings or photographs of this simple 1090 MHz antenna?  I'd like to see the proper way to create the little 20 mm turns in the copper wire.  Are the turns mostly horizontal, or mostly vertical?

I see this additional drawing of the two caps butted together. 

http://www.tech-software.net/endcaps.bmp

Is it correct that the aluminum plate goes between the two caps?  Is the aluminum plate electrically attached to anything, such as the external connector on the Coax connector?

Also, the first drawing shows the lower tube section as 600mm.  Does the length of that section matter?  It seems the actual antenna is above that in the other section, and this tube only houses the coax you would connect to the antenna.  I have no problem creating that length - just curious as to why there is a stated size.


Thanks!

John

[IanH]

The member known as "shakysen" is your man. He knows how to make these.

[shakysen]

Hi John. I use 20mm waste pipe,mark your bottom section with a bit of tape bend the wire Round the pipe.mark middle section and tape off same again with pipe. just pull each coil up so not touching. the vertical part must not touch the disk. They work very well 130-150nm, East,100-120nm North, 100nm South. An mine is poor in the West 90nm. Mine Are indoors

                                                                     Regards Shaky