Dipole Scanner Antennas

[btlacer]

I'm looking at building some antennas for my 4 scanners. I would like to build one for vhf air band, military air band, public service vhf and one for 700/800. Can anyone recommend a design for these antennas? Lengths? I would like to mount them outside but might end up putting them in my attic. Thanks for any help you can provide..

 

[nd5y]

You calculate the length of a dipole by:
L= 234/F
L is the length of one side in feet. The overall length will be 2X that.
F is the frequency in MHz.
For the length in inches use 2808 (234x12).

 

[popnokick]

Homebrewed Off-Center Fed Dipole - The RadioReference Wiki

wiki.radioreference.com

 

[Ubbe]

You can use PVC pipes connected to a T joint and connect electrical wires to the coax. You have to use a balun right at the point where the dipoles meet the coax. There are different types and if they should fit inside the pipe then probably need to be the core type that you stick the coax thru and 5 or more of them. Page 19 in the PDF.

https://www.amazon.com/letsFix-3-Way-Fitting-Fittings-Connectors/dp/B08NDYH87V/

https://w4cae.com/wp-content/uploads/2020/02/Ferrite-and-Baluns.pdf

/Ubbe

 

[ih784]

Homebrewed Off-Center Fed Dipole - The RadioReference Wiki

wiki.radioreference.com

Can a regular copper T fitting be used in place of the CPVC fitting that’s called for in the drawing?

 

[jwt873]

No.. The two legs of the dipole have to be insulated from each other.

 

[ih784]

Copy. Thank you!

 

[majoco]

I cut down an old TV folded dipole antenna cut for 125MHz - even kept the transformer in its little orange box - its only up about 12 feet and works well. I can hear the ATIS from our nearest mil station which is about 45miles away.

 

[Ubbe]

I did the same to a 50MHz low-VHF TV antenna and cut it down to 69MHz to listen to the guys who uses the eight free channels we got in that band that anyone can use without any license or approved radio. Works just fine.

It was too complicated to redo the attachments to the horizontal boom at the balun and also to do new connections to the balun. My antenna had bigger tubing at the center half at the balun end and thinner tubes stuck into the big ones and crimped, so I had to saw that crimp off and make a slit in the larger tubes and tighten with hose clamps.

/Ubbe

 

[John_S]

I cut down an old TV folded dipole antenna cut for 125MHz - even kept the transformer in its little orange box - its only up about 12 feet and works well. I can hear the ATIS from our nearest mil station which is about 45miles away.

I just built almost the same exact thing from a cheap FM antenna. I bought one of those Omni-X antennas and thought I was getting decent reception till I hooked the OCF dipole up. Easy to see I need to build a second one. Highly recommended.