coax for longwire

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coax for longwire

Postby pajeroboi » Sat Nov 16, 2013 10:18 am

Hi folks

I'm looking to build a longwire for the garden to catch some HF. if I stripped the copper wire out of some 75ohm coax, I'm guessing that would work?? I don't know the first thing about baluns or earthing so I'm just going to plug it straight in and see how it goes.

If anyone thinks this will blow up my scanner, or indeed myself, can you let me know in the next couple of hours before I start lol
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Re: coax for longwire

Postby m0lsx » Sat Nov 16, 2013 1:42 pm

There is no need to strip the copper from it..Simply bond (Twist) the inner & outer together & seal it against the weather at one end & you will have a very nice antenna..However that is a VERY exspense long wire, any old wire will do..
Also if you are using a scanner, just buy a short length of bell or speaker wire, 10 meters at most, put a crocodile clip at one end & string it up..It is all I use on my portable radio, as small radios are not like a specialist SW RX, they are not designed to be used with a long wire antenna & often overload & leave you worse not better off.
I use some speaker cable I got from Wilkinson & stripped it down to two lengths, but you could at under £2, be extravagant & simply twist the sides together..


http://www.wilko.com/electrical-accessories/corelectrics-speaker-flex-cable-10m/invt/0081556?VBMST=speaker%20twin
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Re: coax for longwire

Postby pajeroboi » Sun Nov 17, 2013 1:59 pm

Hiya m0lsx

Thanks for the info. Before i read your reply Id already stripped the wire that poked out the house, however the other half which I left the sheild and outer plastic on, I then wrapped the shield around the copper wire halfway down. So basically its half bare wire, half coax with the sheild connected to the inner wire halfway down where the coax starts.

Well it works! My question would be, does the fact that its only connected halfway down make it a worse than if id used your suggestion of connecting sheild and inner wire at the end?

Cheers

Jim
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Re: coax for longwire

Postby m0lsx » Sun Nov 17, 2013 2:30 pm

No it is still the same length & what you have made is known as a bazooka antenna, the braid will alter the tuning, but on a long wire used on RX it is not really important..
http://www.hamuniverse.com/vertbazooka.html
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Re: coax for longwire

Postby pajeroboi » Sun Nov 17, 2013 3:00 pm

Ah ok cool. Well its a start, I'm going to buy an swr meter as I am enjoying experimenting with homemade antennas! I made a dipole from coax which was on the same site and the rx from 25-500 Mhz is amazing. I made a 40ft mast from some old gazeebo poles attached it to the top and hey presto!!!!!!!!
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Re: coax for longwire

Postby m0lsx » Sun Nov 17, 2013 4:02 pm

An SWR meter will only work on RX if you get a audio bridge, so you can tune the antenna without RF..If you just get a ATU you tune for maximum noise volume, so no SWR meter is needed.
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