Topband: Top loaded vertical help,

[Stan Stockton]

Trevor,

I have a setup similar to what you are wanting.  The vertical is something like 68 feet tall.   I made a very large coil using 50 feet of 1/4 inch aluminum tubing.  The coil is about 9-1/2 inches in diameter and similar length.  It is placed about half way up.  If you want a picture of the coil, I'll send it to you.  I like the coil as opposed to the real estate needed and ropes and wires to maintain.

If you have a 70 foot vertical, regardless of how you load it, the R is going to be low if you have a good ground system.  By low I mean something in the general neighborhood of 12 ohms plus or minus a few. You need to keep adding radials until the R doesn't want to continue to go appreciably lower.  You don't want a skimpy ground system which you can install that will give you 50 ohms.  That's a recipe for an inefficient antenna.

The matching is simple to do.  Just wind a big (hairpin) coil using some stiff copper wire - #10 or #12.  I think mine is probably 2 inches diameter and a foot or so long.  Looks like a slinky.  It goes across the feed point from the base of the vertical to ground system.  You can experiment with the length, number of turns, etc until you get a good match. 

For 80 meters I have a quarter wave wire that is spaced out from the vertical about 4 feet and about 50 feet from ground level.  That wire slopes out from the vertical at less than a 45 degree angle and then from about 15 feet above ground it comes back in to the base.  The antennas are fed with separate coaxes and the 80m antenna has its own hairpin coil.

OK, it all works wonderfully because it is located 70 feet from the sea.  I do believe the 160m antenna would work very well without the salt water, however, with an excellent radial system.

CU starting last week of October.

73... Stan, ZF9CW



> On Sep 5, 2017, at 4:45 PM, MR TREVOR DUNNE <ei2glb at eircom.net> wrote:
> 
> Hi All
> 
> Looking for a little help I'm going to build a top loaded vertical for 160m
> 
> I have about 70-75ft vertical and was thinking about using 4 wires off the top to make up the difference,
> 
> My garden is not in the clear with houses and other buildings surrounding it so I'm looking to get the max current up as high as possible,
> 
> Would going longer on the antenna help maybe 3/8th wave will that effect the take off angle, also what would give the best match to 50ohms I'm not that clued up on matching networks so want to keep it simple as possible,
> 
> I will be able to put a good amount of decent sized radials down 60ft minimum, 
> 
> I'm also thinking of hanging a 80m wire down along side the vertical spaced 2ft out and feeding it with another piece of coax against the same radial field will this cause me any issues ??
> 
> I had a trap on a previous inverted L for 160/80 and the bandwidth was terrible so thinking this approach might work better,
> 
> I'm a newbie to all this so be gentle with me Hi Hi 
> 
> Also what is a FCP seem it in a previous topic,
> 
> Thanks
> Trevor
> EI2GLB
> _________________
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