Topband: Feedpoint of short RX vertical
Hello, trying to improve my RX setup, I have a question . When feeding short RX verticals with a coil and resistor in series, does it make sense to decouple the feedline at the feedpoint with a braid breaker ? 73 Luc ON4IA _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Feedpoint of short RX vertical
hi luc so you use a hi z rx arrya and you have matched the 7m long radials with a coil in resonaze? VY 73 frank -Ursprüngliche Mitteilung- Von: luc kerkhofs via Topband lt;topband@contesting.comgt; An: topband lt;topband@contesting.comgt; Verschickt: Sa, 7 Jun 2014 9:13 pm Betreff: Topband: Feedpoint of short RX vertical Hello, trying to improve my RX setup, I have a question . When feeding short RX verticals with a coil and resistor in series, does it make sense to decouple the feedline at the feedpoint with a braid breaker ? 73 Luc ON4IA _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Feedpoint of short RX vertical
When feeding short RX verticals with a coil and resistor in series, does it make sense to decouple the feedline at the feedpoint with a braid breaker ? There is no universal answer. The particular installation determines whether or not decoupling is necessary. Sometimes a ground rod alone is enough, and sometimes even several radials are not enough. Decoupling can help if: 1.) The ground system is marginal or poor. We do not want the coax feedline contributing signals or acting like part of the antenna. 2.) There is noise following the cable shields to the antenna I do not decouple some of mine because the feedlines are all buried a foot deep for 160-170 feet to the center, I have several reasonably long radials on each element, and the antenna is far from any noise. Some of mine I decouple, because they are near the house and the cables are not deep buried. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Feedpoint of short RX vertical
Tom, one of 2 elements is very close to the house ( 20 ft ) and coax is lying ON the ground, so I guess it is best to use a braid breaker ? In fact it is a test setup . I also have a receiver 500 meters inline with the antenna direction so I can check the F/B of my test setup Luc On , luc kerkhofs luckerkh...@yahoo.com wrote: Hello Frank, no it is 11 m high vertical without toploading feedpoint is matched with resistor and coil Luc On Saturday, June 7, 2014 10:09 PM, donov...@starpower.net donov...@starpower.net wrote: Hi Frank, My 8-circle array uses low impedance verticals, not high impedance verticals like the Hi-Z. My verticals use an inductor and resistor at the base of each vertical. In a Hi-Z array each vertical connects directly to the input of a high input impedance amplifier. The purpose of the radials in an array of short low impedance verticals is to provide a reasonably stable feed point impedance. Eight 23 meter radials provide adequately stable feed point impedance at my QTH. Radials are not needed at all in a Hi-Z array. 73 Frank W3LPL - Original Message - From: dl8yhrfrank--- via Topband topband@contesting.com To: topband@contesting.com Sent: Saturday, June 7, 2014 8:23:12 PM Subject: Re: Topband: Feedpoint of short RX vertical hi luc so you use a hi z rx arrya and you have matched the 7m long radials with a coil in resonaze? VY 73 frank -Ursprüngliche Mitteilung- Von: luc kerkhofs via Topband lt;topband@contesting.comgt; An: topband lt;topband@contesting.comgt; Verschickt: Sa, 7 Jun 2014 9:13 pm Betreff: Topband: Feedpoint of short RX vertical Hello, trying to improve my RX setup, I have a question . When feeding short RX verticals with a coil and resistor in series, does it make sense to decouple the feedline at the feedpoint with a braid breaker ? 73 Luc ON4IA _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Fsj4 series heliax around a rotor
Sorry for this not being entirely topband-related, but I'm hoping some people here have tried this. I have a beam on a rotor than has lmr400 feeding it now. The cable has been damaged by critters that like snacking on polyethylene. I'm thinking about replacing the lmr400 with fsj4-50b heliax since I have several thousand feet of that on a reel. I'm also thinking that the corrugated copper shield will resist critter damage better than the braid in the lmr400 cable. Has anyone had any issues with fsj4 series heliax in rotor loops? I'm interested to know if the flexing causes any fracturing issues with the corrugated copper shield in the cable. I'm thinking it will be ok if I make the loop big enough and I'd rather not splice in a piece of lmr ultraflex if I don't have to. Anyone out there have some experience they can share? -Bill Sent from my iPhone _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Fsj4 series heliax around a rotor
This would be a natural topic for Tower Talk. Access via contesting.com 73, Jim K9YC On 6/7/2014 7:03 PM, Bill Wichers wrote: I'm thinking about replacing the lmr400 with fsj4-50b heliax since I have several thousand feet of that on a reel. I'm also thinking that the corrugated copper shield will resist critter damage better than the braid in the lmr400 cable. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Feedpoint of short RX vertical
On 6/7/2014 12:13 PM, luc kerkhofs via Topband wrote: does it make sense to decouple the feedline at the feedpoint with a braid breaker ? It DOES make sense to decouple the feedline. I've never heard of a braid breaker. Under NO conditions should you open the shield == that prevents the shield from being a shield. The good ways to decouple the feedline are 1) a good transformer, a good common mode choke, and radials. See Chapter 8 of http://k9yc.com/RFI-Ham.pdf for winding guidelines for the choke. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
