How to make a leaky feed line - Page 1
Forum section: electronics / rf-microwave

author: Qmavam
author_rank: Regular Contributor
timestamp: November 18, 2019, 02:57:10 am
content: I recently had a metal roof put on my home. Since then, FM reception on my portable FM radiois poor. I can't even get my locals to stay clear.I live in a ranch 75ft long. I want mount an FM antenna at one end and run a wire inside the attic to the other end, the purpose of this wire is to leak RF down into the house.What should this wire be?A modified coax?Run a wire twenty ft down to the earth and ground it and run the other lead through the attic?Run two wire 3ft apart through the attic?Any Ideas?Mikek

author: yl3akb
author_rank: Regular Contributor
timestamp: November 18, 2019, 05:17:12 pm
content: Why dont You just connect another FM band antenna at other end of the coax? Its called 'passive repeater'

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: December 22, 2019, 04:17:07 pm
content: The term “leaky feeder” is a special type of coaxial cable with slots cut in the outer shield to radiate a small amount of RF. Usually they are custom made from a short length of solid outer coax, such as Andrews Heliax, and terminated in a 50 Ohm load. They are used to provide coverage over a small area without causing interference outside the intended area. For example one made for use on UHF may be 3 metres long and provide coverage only to 100 metres away. They are used for factory radio systems to keep the RF from the base station within the factory perimeter.

author: coppercone2
author_rank: Super Contributor
timestamp: December 22, 2019, 05:25:54 pm
content: sounds like you need a buffer on the antenna to drive the leaky feeder, its not efficient enough to be a passive device?

author: SeanB
author_rank: Super Contributor
timestamp: December 22, 2019, 06:08:36 pm
content: Find the cheapest nastiest coax antenna cable you can find, the stuff with no foil shield, ad with skimpy braid, and run it along the ceiling, and then connect it to the external antenna with some better coax. I used to use the cheap coax cables that came with RF modulated equipment, like VCR's, video game consoles and satellite receivers, as those are the right junky coax. You could use them as an antenna in high signal areas, or use another TV set to receive just by having one of those from the VCR output to the TV, and another in the same room connected to the other TV set.Otherwise external antenna, a masthead amplifier with low gain, around 6dB or so, and then good coax to inside, and the power supply there, with another antenna, with only the actual FM loop left on it, mounted inside the steel roof.

author: El Rubio
author_rank: Regular Contributor
timestamp: January 12, 2020, 03:06:47 pm
content: I don’t know if it is practical to try to make leaky coax and really don’t have a suggestion where to begin. I do have experience with leaky coax in wireless installations. It’s a neat idea, but pretty much sucks performance-wise. If it were me, based upon your description, I would put upAn outdoor antenna and run it to a powered signal amp, then a splitter with a dedicated coax run to each receiver. Or, you can put another antenna on the output of the signal amp. This antenna should be directional and facing away from the outside antenna. If not, you risk feedback on the amp. Think microphone in front of speaker squealing. Leaky coax runs about $3.50-4.00 per foot for the small 1/2 in diameter stuff.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 12, 2020, 04:14:34 pm
content: Did they ground your metal roof?