Some of you may have seen the article by WD8DSB in the latest issue of QST. I believe WD8DSB is on this reflector. His article describes a mini-flag antenna that can be used for direction-finding. The neat thing about this antenna, besides its compact size, is that it is unidirectional and is very broadband. It works from the AM BCB through 10m. It produces a sharp null off the back which allows you to determine signal direction without the direction ambiguity you get with a conventional unterminated loop.
DX Engineering is producing this antenna as a kit, along with a companion preamp. (Disclaimer: I have no affiliation or commercial interest in DX Engineering). See: https://www.dxengineering.com/parts/dxe-noiseloop. I just bought the flag kit last week and finished assembling it this past weekend. I see today that the kit is now back-ordered until April so it was good that I ordered it as soon as I saw the QST article. It took me about 3 hours to assemble the mini-flag even though the DXE Web site says it can be done in 1-2 hours. There is a bit of fussy mechanical assembly involved in getting the symmetry and dimensions just right, although it's not hard work. The flag is 42 inches wide and 21 inches tall. The DXE version of the antenna has slightly smaller dimensions than those given in the QST article, which results in a small reduction in gain, which doesn't really matter, but the pattern is the same. I did some testing of the mini-flag in the AM BCB. The gain is very low--about -65 dBi on 160m--so it needs a good preamp. I used a homebrew preamp made up of a couple of MMIC's that produce about 35 dB of gain. The DXE preamp for this antenna won't be available until April. On the higher frequencies, less preamp gain is needed because the gain of the mini-flag increases with frequency. My initial tests indicate this antenna clearly works. By rotating the flag for the deepest null, I could nail the heading an AM BCB station to a few degrees. This antenna could also be used as directional receiving antenna on its own. Although it is not hugely directive, it can be rotated easily to peak or null signals or noise, and it is better than a conventional unterminated loop. It has essentially the same RDF as other larger flag or pennant antennas but is obviously far more compact. This is a nice contribution by WD8DSB. Now I have to go off with the mini-flag and chase some local noise sources that have been plaguing me this winter on the low bands. 73, John W1FV _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
