[TowerTalk] 120' QSO King
Roger (K8RI) on TT
K8RI-on-TowerTalk at tm.net
Mon Jan 27 03:49:38 EST 2014
On 1/26/2014 1:40 AM, Jim in Waco WB5OXQ wrote:
> I ordered one. Now, he says u need at least 50' of coax, more is ok. He also say you need some kind of choke so rf does not get in the shack.
The devil is in the details...
I'd point out there are many variable so what I plan may not work with
Were it me, and it's not. I'd mount the balun as high as I could get it
and ground directly to the tower, I'd add a current balun directly below
the voltage balun. IE: directly feeding the antenna balun. I think it's
#32 material will give you a high resistance on all 3 of the bands you
wish to work. IIRC without looking it up, 6 or 7 cores with 6 or 7
turns should work, but I'd look it up on Jim Brown's site. He has an
excellent paper describing baluns that will do a good job on common
voltages, which can get pretty high particularly on 160 and 75. These
can provide as much as 5000 ohms of isolation. I use 6 turns of Davis
BuryFlex on 5 2.4" cores with a second choke at the point where the
feedline reaches the tower. The 160 half sloper will be fed through 7
turns of smaller, Teflon coax on 7 cores. I forgot the RG number and
it's about two to three times the price of LMR-400 or BuryFlex.
http://www.rogerhalstead.com/ham_files/AntennaFeed2.htm 75 m feed
http://www.rogerhalstead.com/ham_files/tower46.htm 160 feed construction
The output of the current balun will have the shield frounded to yhe
tower and te center conductor connected directly to the antenna. The
antenna is cut for the top end of the band to keep the voltage low. If
cut for the bottom end, operating near the top end of the ban will cause
many tuners, like the MFJ 989C to arc,
I's start with a single current balun feeding the balun at the antenna.
I'd add the second balun near a quarter, or half wave of feedline from
the antenna if it proved necessary. Note, I use wire nuts instead of
> Where does the choke go? On my beam the choke goes at the feedpoint on the antenna. on this end fed antenna does the choke go at the antenna feed point or does it need to be at least 50' down the coax or just before the coax enters the shack? Is the 50' part of the coax supposed to radiate? Next he says he put a ground lug for those who want to use it. The feedpoint will be aprox 50' above the ground on a tower. So, ground it to the tower leg, or run a separate insulated wire to the ground and ground it, or connect it to radials on the ground or elevated. If elevated they must be high enough to walk under. That would put them about 43 feet below the antenna and they can only run in a 180 degree path some as little as 25' others as much as 50' or do they all need to be the same. I have a 500' spool of 14ga. and I can use it all if this will help my signals. Also the radials will not be under the antenna rather on the oposite side of the tower since the antenna ru
> ns over the house for the first 60' then over open yard. Radials have to be in the side yard away from the house. So many decisions. I really want this to work as well as possable and since I have to pay someone to install if for me I want to do the job right the first time.
> I only need this antenna to work on 160, 80, and 40. I have a beam at 53' for 20-10.
> 73, wb5oxq
> TowerTalk mailing list
> TowerTalk at contesting.com
This email is free from viruses and malware because avast! Antivirus protection is active.
More information about the TowerTalk