I'm interested in suggestions for how to best segment the coax running between my shack and tower-mounted antenna. I'm thinking of something like this: (1) from shack to the base of the tower through
Grounding to the tower at the top and bottom is a good idea. It is, but unless you are running QRO and/or UHF it's quite a bit of overkill. From personal experience with both LMR 400 and 600 UF the U
At a minimum there should be multi-turn ferrite chokes right at the antenna feedpoint, using my Choke Cookbook as a guide for winding them. As Roger has suggested, an additional choke further down th
that seems reasonable.. you have breaks at the places you're likely to change something... and, if you get a strange effect in the shack, you can go out to the base of the tower, disconnect, and chec
This is a problem that concerns me as well. "Up the Tower" suggests that you not try and keep it totally dry. It suggests you use drain pipe to let moisture and condensation seep out of the bottom.
Rick, I have a large "conduit" running 200' to one of my towers. So, speaking from experience, there is no easy way to keep water out unless you want to pressurize the conduit with say, dry nitrogen
The problem may be that he needs to decide right now, while he is installing the coax. On the other hand, large ferrite cores will be very expensive imports in ZL, so it won't be cost-effective to sc
Or if he has a connector at the base, then adding a choke is easy, either with slack in the coax, or a connector used inline version. _______________________________________________ _________________
Ah, the joys of southern California... In this climate, outdoor connectors are something to be used only when absolutely essential. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ______________
The annual rainfall in my Northern California redwood forest averages 70 inches, all of it between October and June. I have LOTS of outdoor connectors, but we learn how to weatherproof them. I agree
Jim's comment should not be misunderstood. A 1:1 choke balun feeding a _perfectly_ balanced load does not have zero common-mode voltage across it; the choke CM voltage will be exactly half the voltag
Another issue is that most "drain" tubing has a very thin wall compared to PVC conduit. If you have rocky soil or will have the "conduit" buried under a path where vehicles will travel, you will want
This is incorrect. First, it is a CHOKE, not a "balun." Second, if the CIRCUIT is balanced, the common mode voltage and the common mode current, by definition, will be zero. Third, both the different
In the case of a perfectly matched antenna the voltage on the inside of the shield is half the "differential mode" voltage, not common mode. Common mode voltage on the outside of the coax indicates t
Jim, You'll not be surprised that I disagree strongly: 1) It is a BalUn - it's a device that interfaces a BALanced load (the antenna) to an Unbalanced source (radio + coax) 2) If the load is complete
Roger, I challenge a couple of those comments: 73, Steve G3TXQ _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contest
A "balun" is a very fuzzy word given to a generic black box (often a "mystery black box) that can consist of at least a dozen VERY different things. You may USE a common mode choke to connect an unba
Jim, I'm not going to waste my time in long debate with you again! I'll just leave other readers to check what I have said using NEC. You might believe that NEC can't model the common-mode currents,
For anyone without access to a modelling tool, let me try to give you a simple qualitative analysis. Say we have a perfectly symmetrical dipole fed with coax that drops away exactly at right angles f
I should have said and meant to say balanced, you are correct although it is the system that must be balanced Typical baluns of this type are transformers be they 1:1 or 4:1 or what ever. They are ca