Folded Dipole?

kkn50 · #1 (**permalink**) 10-22-2005, 12:55 PM

I recently salvaged an antenna from an industrial site. I suspect it was used for their on-site repeater.

I don't know much about these antennas but I think that it is a folded dipole. Each of the folded elements is about 11 inches from end to end. I am guessing that it is a UHF antenna tuned either to the 450 or 460 mhz range. Any of you have experience with using such an antenna with a scanner for the UHF band?

Link to photo: http://www.sendpix.com/albums/05102209/tk27xuoklu/

Thanks.

rescue161 · #2 (**permalink**) 10-22-2005, 01:34 PM

I'm using the exact same antenna on my repeater here.

If you're using it as a scanner antenna, then you'll have OUTSTANDING reception in the UHF band.

Old4rd · #3 (**permalink**) 10-22-2005, 08:48 PM

I believe it is a Cushcraft. http://www.cushcraft.com/details.asp...39&group_id=22

rescue161 · #4 (**permalink**) 10-23-2005, 02:01 AM

Or Decibel Products. They're the ones who made the one I use.

ReceiverBeaver · #5 (**permalink**) 10-23-2005, 08:27 AM

Hey KKn50,

These are also known as Phased Dipole Arrays and are available in VHF sizes too. You can position the elements in a verticle line for a directional pattern, or space them around the mounting mast per manufacturer's instructions to obtain an omnidirectional pattern. They provide good gain without being too large or bulky. Sweet find. A keeper.

TeRayCodA · #6 (**permalink**) 10-24-2005, 12:54 AM

I made a VHF MURS Folded Dipole antenna like that a couple of years ago,and it is the absolute best MURS antenna I have built.

http://hometown.aol.com/teraycoda/myhomepage/photo.html

crazyboy · #7 (**permalink**) 10-24-2005, 02:14 PM

TeRayCodA: Could you post measurements for the antenna? Supplies too?

TeRayCodA · #8 (**permalink**) 10-25-2005, 01:47 AM

The dipoles are 18", using solid alum stock,using a bender(3/8" hole drilled through workbench,and vise with 1 & 1/2" pipe to bend the dipoles)

Gamma match from 2meter specs,about 7".(about the only way I could tune this monster,and get it to resonate/work)Yes,I know the real folded dipole antennas don't have a gamma,but I have never seen one up close,so,I did'nt know the magical/tech feedpoint,but this worked out really well for me.

Phasing harness is RG8U,equally measured/cut(don't recall the exact lengths)PL-259 connectors to each dipole,everything is terminated with an N connector.
Feedline is Andrews FSJ-4-50 Heliax.

About 40ft up the tower,using a R/S 19-1210 Murs/Business band radio,Pyramid 13.8V power supply.
Just checked SWR the other day,still at 1.2:1.

Here in Okieland,the terrain is mostly flat,and I am getting a range to another mobile of about 10-15miles.

BTW I am not much of a techie,but I just build what I see,and try to make it work.

TeRayCodA · #9 (**permalink**) 10-25-2005, 01:52 AM

The support pipe is 1 & 3/4" Dia aluminum pipe.The dipoles are mounted on some 1 & 1/2" pipe cut to fit the contour of the support pipe,slots cut in the 1 & 1/2" pipe with S/S hose clamps to secure them onto the support pipe.

The entire antenna is 10ft.

eastcare · #10 (**permalink**) 10-25-2005, 07:40 PM

we have a folded diapole at our station and it works quite well, its being used in conjunction with a Midland LMR, which if I get my way will soon be replaced. But the antenna has been up since the early 80's

Al42 · #11 (**permalink**) 10-25-2005, 09:44 PM

Quote:

Originally Posted by TeRayCodA

Gamma match from 2meter specs,about 7".(about the only way I could tune this monster,and get it to resonate/work)Yes,I know the real folded dipole antennas don't have a gamma,but I have never seen one up close,so,I did'nt know the magical/tech feedpoint

1/2 wave phasing section for most of them. 50 ohm coax, centers to the dipole - feedline to one end of the section, all 3 grounds (feedline and both ends of the section) tied together.