2
$\begingroup$

I would like to put up a relatively large loop antenna to cover all the HF bands. I have sloping terrain and geographically in a slight "bowl" with hills and/or ridges in many directions.

If I stick with the trees on the high part of my property, it looks like I could get somewhere around 400 ft. of wire up perhaps 25ft. high on average.

Or, I could extend the loop to the lower end of my property, where I at have some arbor vitae that I can almost see over when standing on my porch — this would allow me to get over 500ft but most of that extra would be lower.

My plan is to use a tuner in the house with around 20ft. of coax running to a balun outside, so I'm wondering what sort of tradeoffs I should consider here.

  • Is it better for a large horizontal loop to be 10ft higher on average, or 100ft longer total? Ignoring other factors, how would loop diameter and height (and slant!) affect the radiation pattern?
  • If I can't get an exact resonance on 160m, should I aim for some other particular length of wire (perhaps optimizing the higher bands, or to get some OCF-style impedance compromise), or just string from tree to tree around the lot and let the tuner deal with it?
$\endgroup$
1
  • $\begingroup$ Higher will reduce your ground losses. $\endgroup$ Feb 5, 2017 at 13:00

1 Answer 1

2
$\begingroup$

Rules of Thumb

ah... I can answer that

  • higher is better for DX (more lower angle lobes)
  • lower is better for NVIS (more higher angle lobes)
  • longer is better than shorter, but much longer than a full wave on lowest desired frequency is not needed
  • shorter feed is better than longer feed to the tuner to minimise feed-line losses
  • resonance is not needed if you have a short feed to tuner (or tuner at feed-point)
  • parallel to ground is better (more even lobes) regardless of ground at angle or curve, but slant when you need too.

I am sure that you will get more scientific answers, but those are the rules of thumb I have used in the past when doing (sky) loops.

I also kept the following in mind:

  • you are using lots of wire, spanning a larger area: I always make sure that I can take it down quickly in case a "situation" occurs. I always made sure that I could lower and "unhook the wire" without climbing ladders.
  • use counter weights to tie-off / tension: you are likely to use natural objects (such as trees) to support your loop. These objects move, therefore a counter weight tie-off-tension system will ensure you minimise damage, while maintaining tension on the wire, allowing the objects to move.

Lastly:

Experiment! Wire antenna's are easily to take down, change, put back up, and experiment. Sky loops are fun to play with; do expect "lobes" at "angles/azimuths" and some nulls as well...

Good Luck.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .