Topband: Top Band Antenna

kolson at rcn.com kolson at rcn.com
Fri Aug 7 13:07:14 EDT 2015


You probably know this Rodger, but just in case... 

Radials are ESSENTIAL. As many as you can as long as you can make them (up to 1/4 wave) in as many  directions as i s possible. I staple mine down with lawn staples (I find them at home improvement stores) and after a year or so they tend to "migrate" underground. Till then, you may have to set your lawn mower to leave a bit higher grass and perhaps mow carefully where they are vulnerable due to one's lawn not being perfectly flat . When I moved QTH after 4 years a while back and decided to remove the radials, I had to rip them up to get them out, so they were essentially invisible by then. Having a radial connection plate, either commercial or home brew (I use the one from DX E ngineering) makes things easier and neater. 

I have a wire  "T" with a 40 ft vertical section and a 90 ft horizontal section and about 35 radials, some as long as 50/60/ft and some as short as 20/30 ft (some even go down my basement access hatch and run in the rafters through my basement, be creative)! I mo deled this in a simple antenna program (that I didn't kn ow much about using, it came with an ARRL Antenna Book) and it spit out values for a matching network that got me into the ballpark. The idea for the "L" is another good one and only requires the ability to have space and an anchor point in one direction. Try to keep the loading wire as parallel to the ground as you can, but don't worry if you can't do that perfectly. Again, antenna modeling software will save you much time matching the antenna. On my "T", one leg e nds up at 50 ft and the other at about 20 feet (due to  the supports available ), I would say don't obs ess about it, just do what you can. 

I live on a small lot and that's what I can do in my context and  this works positively, err.... OK, especially for DX. To put it in context, it is MUCH better than a Butternut vertic al over the same radial "field", so the loading wires can buy you a lot . Think about a RX antenna too. I have a K9AY that is not as optimal as I would like, but it still often makes the difference between copy/no copy for DX (often on bands other than 160, BTW, I have used it up to 15 meters at times!) . Again, be creative and search the internet for ideas. I have not set any new world DX records with this set up, but I did finish my DXCC, so it at least  gets you "into the game". 

Best, Kevin K3OX 

----- Original Message -----

From: donovanf at starpower.net 
To: topband at contesting.com 
Cc: "rodger bryce" <gm3job at hotmail.com> 
Sent: Friday, August 7, 2015 12:16:17 PM 
Subject: Re: Topband: Top Band Antenna 

Hi Rodger, 


You will have better success if you add a top loading wire to your mast, 
which makes it into an inverted-L. Suggest you start with an 80 foot wire 
in a straight line if possible but otherwise route it any shape necessary . 
You can increase or decrease the length of the top loading wire to improve 
the match. 


As an alternative to shunt feeding your mast, you could simply install an 
130 foot inverted-L parallel to your mast and direct feed it from the 
bottom. 


You could add a loading coil to the wire if 80 feet is too long. 


73 
Frank 
W3LPL 

----- Original Message ----- 

From: "rodger bryce" <gm3job at hotmail.com> 
To: topband at contesting.com 
Sent: Friday, August 7, 2015 2:54:40 PM 
Subject: Topband: Top Band Antenna 

Gentlemen, I have the following which I would like to turn into a topband antenna if possible. My mast is approximately 40 feet high and there is rotor cage with a 10 foot stub mast, on the stubmast I have an 8 el.log periodic and above that a rotary dipole for 30/40m. 

I attached a drop wire at approx. 38 feet high, I grounded this wire and tried to grid dip the wire plus mast, all as per ON4UN's book "USING THE BEAM TOWER AS A LOW BAND VERTICAL" the results were zilch, nadda nothing at all, no dip anywhere on any band. I used the MFJ 259B with the GDO accessory. 

1. Am I doing this all wrong......highly possible.!! 
2. Is the mast not high enough to be used for top band.? 

I am totally out of my depth here.........so any guidance would be much appreciated. 

Many thanks, Rodger/GM3JOB 

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