[TowerTalk] Half Sloper Recommendations

jcowens1 at comcast.net jcowens1 at comcast.net
Sat Jan 2 10:28:43 PST 2010


I know you are trying to wrap up your recommendations on the half sloper, but will add my 2c for what it is worth. I had a half sloper off my US Tower 72ft motorized tower for about 4 years. I worked about 60+ countries with this antenna and recently took it down in favor of a Inverted L suspended between two of our plentiful Northwest  fir trees. I found the sloper to be a very noisy antenna, and slightly directional in the direction of the sloper wire, but fairly omni. Almost all of the stations I worked were with QSB and in and barely out of the significant noise level that is usually there. I had a lot of ESP contacts. I live a good distance from the metropolitan area, and feel my ambient noise levels here to be below average. 

The only rub with the Inverted L is the big radial field you have to lay out, but that part is done. It is a much better antenna than the sloper. As far as I am concerned, the best approach to 160 is to use either of those antennas for transmitting as both are good transmit antennas, but you will be much better off with a separate receive antenna. I have no experience with the K9AY loop antenna, but understand it is very good. A Beverage antenna would be better in the E-W direction and reversable using DX Engineering gear. That takes a lot of real estate, but people I know who have them do very well. 

I have been experimenting with a 1/2" hardline coax loop antenna lately and am pretty impressed with what it does. It makes almost all of the white noise go away, and leaves you with a weaker received signal, but at a better S/N ratio. It is 6ft in diamater, and I have it sitting on top of my satellite antenna array as you do want to rotate it for optimum results. Basically you are aiming the antenna in the direction that cancels the greatest amount of noise. Check out the following reference for this kind of antenna design. 


The design shown about 2/3 down the page showing a split shield at the top, and with a variable cap at the bottom is the design I built. I got my hardline coax from the local cable video supplier as they usually have scrap left over when they do pole installations. They gave me about 30ft for free. It is much stiffer than RG8U, and holds its shape pertty well. The cap should be a variable with a range that includes around 900pf at center range (mica compression). The same antenna will work on 80M with a capacitance value of around 300pf. I built it in an easel configuration using schedule 40 PVC. If you are interested, I can provide additional pictures and reference info to build it. The important thing is that the coax loop be symmetrical and rigid so that it retains the circular shape. 

It is amazing that this tiny little antenna can provide such good results. I rarely use anything else for 160M receive. I am now working countries in EU which was very difficult with the sloper and Inverted L. It does resonate at 1.820 which is where I want it for CW operation. I do not miss the 160M noise. A friend of mine lives within about a block of a major power substation, and 500KV power distribution towers and he was trying to operate 160M with a very nicely installed inverted L antenna. It was hopeless. He is now working many stations on 160M with the coax loop antenna for receive. 

John Owens  -   N7TK 

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