antenna for airband recievers

[1d2d3d4d]

Hi all,

Some time ago there was a thread on here with the details of mking an antenna to increase the range of an airband receiver. I have tried several searches but cannot find it. I think the instructions included the length of co-axial and how to split it to make a suitable rabbit ears antenna.

I have just started IMC training and thought it might be a good idea to try and listen to commercial traffic to increase my comprehension speed on RT. I live 40 miles away from the nearest large airport but with a decent twig might just be able to get reasonable reception.

Thanks in advance Chris

[Keef]

If you meant the details for a plain dipole, it was a length of copper tube - a resonant half-wavelength - split in the middle and fed with coaxial cable. Use placcy pipe to hold the two halves together.

There's a thread here (http://forums.flyer.co.uk/viewtopic.php?t=40317) that describes it a bit.

If you want to fabricate your own, drop me a PM and I'll send you the exact dimensions etc. It's not difficult.

The hard part is getting the antenna up high enough and clear enough to pick up airband transmissions. The radio horizon in statute miles is 4/3 the square root of the height above ground in feet - so you don't hear many ground stations unless they happen to be on hilltops.

[BackPacker]

If your receiver has a BNC antenna connector (round, twist about 1/4 turn to lock) then what you need is RG-58 (50 ohm impedance) coaxial wire. Usually black, it was also used for "thin ethernet" so any computer shop with a sense for nostalgia might have miles of the stuff lying around.

Snip one connector off from one end and connect it to a dipole: simply two pieces of wire (copper electricity wire will do), one sticking straight up, the other sticking straight down. Lenght of each wire should be one quarter wavelength. The thread mentioned above has the details but anything between 62 and 75 cm should probably suffice for airband.

One of the wires connects to the core of the RG-58 coaxial cable, the other wire connects to the mantle. Doesn't really matter which goes to which as long as the antenna is mounted vertical, as high up as possible. Also doesn't matter all that much how you make the connection. I used standard household stuff to connect electricity wires together. Works fine.

In my case I used a scrap piece of wood and some tie-wraps to hold the antenna together, and some velcro to tie it to a wooden upright in the attic.

[liam548]

of course it depends on your location, someone with good line or sight will pick up better quality signals with a poor antenna that someone in a city with a good antenna but I found several of the shelf antennas that work great for airband.

One in particular, a wideband discone picks up manchester ground no problems from my house near Halifax, and its some 40 miles away.

[1d2d3d4d]

thanks guys.

Thats just whay I was looking for. I've got the connector, just need to nick some eternet cable now.:ok:

Chris

[1d2d3d4d]

Keef, Backpacker,

Thanks guys. I now have a dipole built and working, just need to get it up high enough, and get the connector fixed onto the co-ax properly! I havn't had time to set it up properly what with work, getting ready for holidays and trying to fly as well, but it should stand me in good stead over the next few weeks.

Thanks again from a happy ppruner.

Chris

[Blues&twos]

Made a pretty rough looking dipole (approximately following Backpacker's original instructions) when the original thread was "in progress". At the time I lived in a really terrible reception area, and even in a bungalow the dipole impoved my scanner reception dramatically. All held together and in place with gaffa tape in the loft!
:ok:

(That's the dipole, not the bungalow).

[Frelon]

.....or if you do not want to go to all that trouble you can buy a ready made one here (http://www.emnet.co.uk/wilsam/).

My last one I left on the chimney of my house when I moved (the removal men would not go up to get it!). It really gave me excellent reception.

[Whopity]

Far simpler, get a length of bell flex; split one end to make a diapole; tie a knot at the end of the split to stop it spreading; connect the other end to a BNC plug. Bell flex is about 75 ohms and far cheaper and easier to use than coax!