burgemusic
Location : Scarborough
Spotter Watch Member : 83
|
 Subject: Home made UHF antenna - cheap/effective - DIY guide 2008-12-27, 13:07 |
|
|
All,
Below are pics which hopefully explain how to make an effective vertical dipole useable for UHF airband without spending hardly any money.
This stuff was on the old forum and I havent been on in ages and see that its no longer available.
Hope this is of help to someone who fancies experimenting with such things...
PS If you need to buy coax/connectors I can recommend:
www.whwestlake.co.uk
very reasonable prices, and they have "everything".
best regards
Alan Burge
First get some coax (eg RG58C/U)
You want a BNC plug on one end (to fit to your scanner)
Measure about 10 inches from the end
Carefully cut round the black pvc outer - dont press too hard - you dont want to cut the silver braid.
To get the black pvc off, it may help to cut long ways too, but again, go easy here....
Peel away the outer plastic...
Now you have something like this......
Prise out a little hole in the silver braid , its quite tough stuff, youll need a screwdriver...
Then "hook through" the inner plastic covered conductor and pull it "out" of the silver braid...
..so that you have two loose ends like this......
Now we just need a rigid support to "stretch" these two ends across. The support must be non-metallic (wood/bamboo/plastic are all OK)
Then hang your new creation somewhere by the window and try some frequencies you know.
(When you are inside a room there are always 'sweet spots' and 'dead spots' for reception- the best way to find a sweet spot is if you know an ATIS frequency - tune that in - because it is constantly transmitting its easy to move around holding the antenna until you find the best 'spot' in your room to site the antenna. But a good guess is the middle of the window will prove to be the best place.)
(If your wife comes home from shopping while youre in the middle of all this and asks what the hell your doing - hold your nerve - tell her you are now a scientist and she needs to give your genius some space.)
If you try the above and get good results you might want to refine the design a little and make the below:
Its really exactly the same antenna but this time a BNC chassis socket is used at the "middle" and two bits of copper wire used to make the two sides.
The longer these antennae are it changes the "resonant frequency" ,now there is a formula
468 / freq in MHz = dipole length [feet]
[468 divided by freq in MHz equals dipole end to end length in feet]
BUT in the real world you dont really have to get into all that I would suggest making the dipole this long for starters:
For UHF listening [230-390MHz] about 20 inches from end to end [10 inches each side]
Last edited by burgemusic on 2008-12-27, 14:06; edited 2 times in total
|
|
GOOSE
Moderator
Location : UK
Spotter Watch Member : No
|
| Subject: Re: Home made UHF antenna - cheap/effective - DIY guide 2008-12-27, 13:21 |
|
|
|
Alan, your thread was a huge success on the old forum so a big thank you for posting again. Can you add your formula and decriptive notes as well? Then I'll make this a sticky, it's a great resource.
|
|
Aileron
Location : Ramsey, Huntingdon
Spotter Watch Member : no
|
| Subject: Re: Home made UHF antenna - cheap/effective - DIY guide 2009-01-27, 04:07 |
|
|
|
is it possible to permanatly hang this on the out outside of the house
|
|
scottish_scanner
Location : NE Scotland
Spotter Watch Member : Yes
|
| Subject: Re: Home made UHF antenna - cheap/effective - DIY guide 2009-01-27, 08:38 |
|
|
Hi there,
I use mine mounted outside - I used cat5 network cable using a similar principle and connected it to around 20ft of bamboo cane. I used waterproof tape to hold the cable in place, connected a bnc type connector to the end of the cable. Works a treat at my location in NE Scotland - I can generally hear 4 or 5 of the Scottish Military controllers which I have never been able to do using previous antennas.
Cheers
Richard
|
|
dervish
Location : various
|
| Subject: Re: Home made UHF antenna - cheap/effective - DIY guide 2009-01-27, 10:40 |
|
|
- Aileron wrote:
- mines been made for months but just wanted whats the best way of hanging it outside (weather proof)
Enclose it in white (NOT grey or black) ABS waste pipe. Get end caps and drill one to allow passage of the coax (or a panel mount BNC). Ensure the end caps are sealed.
|
|
Aileron
Location : Ramsey, Huntingdon
Spotter Watch Member : no
|
| Subject: Re: Home made UHF antenna - cheap/effective - DIY guide 2009-01-27, 10:59 |
|
|
|
why not gray or black?
|
|
doc steve
|
| Subject: Re: Home made UHF antenna - cheap/effective - DIY guide 2009-01-27, 17:24 |
|
|
|
metallic content in the colouring of the plastic
|
|
dervish
Location : various
|
| Subject: Re: Home made UHF antenna - cheap/effective - DIY guide 2009-01-27, 22:37 |
|
|
- doc steve wrote:
- metallic content in the colouring of the plastic
Almost....
actually the carbon content makes the tubing conductive and act like an aerial.
|
|
Sponsored content
|
| Subject: Re: Home made UHF antenna - cheap/effective - DIY guide |
|
|
|
|
|
