Sorry, should have read more carefully.
For a horizontal loop I'd suggest, if possible, using some kind of open wire feed. "Possible" means you have room to take it off at close to 90 degrees and to route it several times its width away from anything conductive.
If you use coax, consider an autotuner at the feedpoint.
Play with some numbers at http://www.ocarc.ca/coax.htm
, where there's an online calculator for coax losses depending on line length and SWR.