Last week, I posted a message asking for suggestions for 80/75 meter antennas for ARRL Sweepstakes use. My original message and responses received are summarized below. After reading the responses and doing a little supplemental reading, I've settled on a 80 meter horizontal full-wave loop (either delta or diamond, depending on how I situate it), mounted at 40 feet. This is 0.15 wavelengths, and is the height cited in the NVIS (Near Vertical Incident Skywave) literature as the best compromise between ground losses and high-angle radiation. I'm also going to install a similar loop for 40-meters at around 20 feet up, also to gain the benfit of NVIS - the close-in QSOs. Thanks to everyone who provided inputs! 73, Jeff K8ND _______________________________________________________________________ Date: Wed, 20 Aug 1997 21:20:53 -0400 (EDT) From: Jeffrey Maass To: Contest Mailing List Subject: [CQ-Contest] Sweepstakes Antennas: 80/75 Meters After an absence of several years, I'm rebuilding my antenna system with an eye towards ARRL Sweepstakes. Today I'm considering how to improve my 80/75 meter coverage domestically. Located in Central Ohio, I'm interested in saturating a 500-mile circle to cover the population centers, and that means I want to maximize my high-angle lobes. I have available one 70-foot tower, and some fairly tall (up to 70-80 feet) trees, ranging from 50 to 150 feet away. I currently have up an inverted-V broadside E-W with the peak at 70 feet and fed with half-inch hardline. I'm considering a delta loop, broadside E-W, bottom corner fed, supplemented by an inverted-V broadside N-S. Any better ideas? Delta- or diamond-loop oriented horizontally 50-60 feet up? Jeff Maass (jmaass@freenet.columbus.oh.us) Amateur Radio K8ND USPSA/IPSC # L-1192 NROI/CRO NW of Columbus Ohio 25000 Members in 2000! _________________________________________________________________________ From: Kresimir Kovarik <9a4kk@geocities.com> I beleive that the best for this short contacts would be a horizontally oriented delta loop or quad (doesn't make some differences). I am using horizontally oriented delta loops for 80 and 40 meters bands to work Europe, and it's doing a really nice job for me. The difference between this delta loops and inv v antenna is big for short contacts. Chris, 9A4KK _________________________________________________________________________ From: JOE and TAM BV/N0IAT When I lived in Indiana, I found that any antenna higher than about 50 feet would work east or west coast well, but did little to get my signal into the surrounding states. For the surrounding states, a low dipole at about 30 to 40 feet worked well with my barefoot rig -- it was fed with ladder line and would load all bands 80 thru 10, but was resonant on 80M. One field day, as I recall, we strung a ladder-line dipole between two stadium lamp posts at about 100 foot level -- our ability to hold a frequency was hindered by the high dipole, though we did work some good DX on 80M, we had a tough time working the folks close in. Why not try a couple X dipoles switchable from inside the shack. This will give you some directionality while taking advantage of the high lobes that low dipoles create. _________________________________________________________________________ From: "Douglas L. Klein, K4LT" Try the trusted cloud burner if you have enough room. It is a 2 element wire beam with reflector UNDER the dipole. 73, Doug K4LT (ex-WD8AUB) _________________________________________________________________________ From: Pete Soper You're in a great location for the 500 mile strategy. In your shoes I'd investigate the NVIS designs aimed at providing gain at high angles. _________________________________________________________________________ From: Randy Thompson For SS, I don't think you can do much better than what you have! If you had said DX contests, then it might be worth investigating the delta loop or perhaps even a quarter wave sloper. _________________________________________________________________________ From: HENRY Nothing sounds better than saturating a 500 mile radius with strong low band signals! Here's what I did last weekend. Our contest club, W4WS in Winston-Salem, NC decided to run the NAQP from my house. I live on a 90 x 1590 lot in the downtown area- a rather high area, close to the highest peak in the city- with trees in the front and back yard. I have a Gap Challenger, and felt it waas time to experiment with a second antenna. NAQP was perfect timing. Anyway, I put up a full wave horizontal loop for 80 meters- 68' on a side- Its in a ROUGH square pattern( more like a stretched diamond) due to my tie off points. the tie points are 2- @40' and 2- @50'. I fed it with 450 ohm ladder line on one of the 40' corners and used a roller inductor tuner. The results were amazing. A small station like ours- no yagis- no monster beverages- RAN 80 meters during NAQP for about 2 hours when it seems everyone else had terrible noise problems. It seemed to asttenuate atmo noise, tuned up on all bands, including 160- I was impressed and as a GAP user, found it too be a quiet antenna with big rx/tx capability. For a smaller area, i'm convinced. In fact, I told my wife after the contest that it is "staying up for more extensive testing." . I took the borrowed roller tuner back to our local club station, and for kicks, tied the ladderline to a 1:1 balun , fed it with coax from just outside the shack to my ts930SAT. The radio tuned it, and again, it put out fine, but I really enjoyed the rx- standard ragchews through the noise came jumping out of the radio. I have to buy a tuner- will probably buy one at Shelby, the granddaddy of em all- over Labor Day weekend. Good luck with the antenna- PS- Use copper line that is easy to handle- I had fits from tangles! 73, Henry Heidtmann, N4VHK _________________________________________________________________________ From: Larry Lindblom-wa0etc The loop is usually a gud low angle ant. How about the old cloud warmer special-a dipole at 30-50 ft on 80/75 has losts of high anle rad. _________________________________________________________________________ From: Patrick Croft Look at a two element beam pointing UP. You can install a inverted vee reflector element under your present vee and get excellent high angles with gain into the 500-600 mile region you seek. _________________________________________________________________________ From: John Nitzke For high-angle radiation, multi-band operation and QRN-reduction, a horizontal loop sounds like a good idea. If your tower and trees allow the geometry, you would do well with a loop in the horizontal plane. Cost is very low. Consult: QST, November 1985, p 20 QST, May 1990, p 28 73, April 1996, p 18. _________________________________________________________________________ From: "Milt Jensen, N5IA" JEFF, THE GUY WHO DID REAL WELL LAST YEAR USED A TURNSTILE. GIVES YOU A REALLY LARGE OMNI-DIRECTIONAL HIGH ANGLE LOBE. YOU GUYS HAVE IT MADE FOR THAT SORT OF OPERATION. OUT HERE IN SW NEW MEXICO I MIGHT MAKE A DOZEN CONTACTS WITHIN A 500 MILE RADIUS. GOOD LUCK ON ALL. 73 DE MILT, N5IA. _________________________________________________________________________ From: "Roderick M. Fitz-Randolph" Jeff, I would suggest the quad loop, horizontally placed, at about 30 feet for local (500 miles) coverage. Rod, W5HVV _________________________________________________________________________ From: Steve Lufcy Jeff- My vote goes to the Delta loop. I used one for a number of years and always felt like I owned 80 meters. I came in 2nd in US in 1986 WPX single band 80 with that antenna. I fed mine at the bottom corner for vert polarization but for SS moved it to feed it in the middle of bottom leg for higher angle horizontal polarization. Good luck and I'll be looking for a BIG 80m signal from you this year in SS. 73 de KM0L Steve in KC _________________________________________________________________________ From: "T. A. Russell" You want to MAXIMIZE your HIGH angle radiation and you are considering a VERTICALLY polarized antenna? Go back to your antenna books and look at the radiation patterns! (There may be some merit in placing a reflector .15 wavelengths BELOW a dipole such that the pattern is aimed straight up. Such configurations are affectionately called "CLOUD WARMERS". The claim is that it improves the reflection efficiency at high angles.) de Tom N4KG _________________________________________________________________________ From: Tom Osborne I think if you fed the delta in the bottom center, it would be horizontaly polorized and better for close in contacts. Bottom corner feed will give it vertical polorization and a lower angle of radiation. > Any better ideas? Delta- or diamond-loop oriented horizontally 50-60 >feet up? Those are real cloud warmers and good for close in contacts. _________________________________________________________________________ From: Don Nutt What you need to do is NVIS (Near Vertical Incident Skywave). The only trick (if you will) is to place the antenna between 1/8 and 1/4 wave from the ground. Inverted vee's work well, Horiz. work well to. I have done quite a bit of study for EOC's and mobile deployments in the early to mid 80's. If you model the antenna, you will find that the lobes will be nearly (or purely) spherical with an optimum angle(s) from 45 to 135 degrees off the horizontal plane. This will allow you to cover a 600+ KM range from your QTH. In real world practices in CA, I was able to provide excellent coverage over the whole state and several adjacent states from Sacramento. This allowed reliable communications over a 500 mile radius. Oh, yes the frequencies that were tested were in the 75/80 and 40 meter ranges. The key was to not exceed 1/4 wavelengnth above the ground at the desired frequency of operation. This technique was proven in the field during Operation Desert Storm. (9K2WR after the ground war was over). Don Nutt N6TDM/0 (newly transplanted in MO) ______________________________________________________________________ From: Nd3f@aol.com Take a look at the ARRL handbook and build a "loop skywire" horizontal loop for 160 and 80 meters. I have one, and so do several other folks around here. Mine is about 65 feet average height and 540 feet in length. Fed with 450 ohm ladder line, but coax works OK and just about anything feeder works (feedpoint impedance is high, and varies from band to band from about 300 ohms to about 1600 ohms for mine). For 80 as the primary band, 270 feet long is about right. (1000/freq in MHz is close enough). Can be used on all ham bands with a tuner, no problem. It hears great--has noise immunity because the horizontal loop has natural cancellation properties. It works great short because it has a lot of high angle lobes, but also FB for DX. I have a bunch of wallpaper on various contests running QRP or low power and using this antenna. I have even worked more than 20 countries on 6M with it! In this area, WK3I (perennial 160M QRP champ) and K2YWE both have one and are happy. I tried a 1000 foot arrangement, but the 540 foot one works best on 80M and especially 40M at my installation, and is OK on 160. BTW, the loop hears as well as my EWEs (I took 'em down) but not as well as the beverage I put up for SS. In general, no one distant believes I could be running QRP... Brian ND3F _____________________________________________________________________ From: "Raymond G. Crepeau" I don't recall the specific objectives you cited in your original post. But when living in Asheville, NC a year ago I used a 1/2 wave 80 meter dipole up about 20 feet. The main lobe is up! My objective was to enable emergency communications within the state of North Carolina on the Tarheel Emergency Net on 3.923. The theory here is called "near vertical incidence radiator (NVIR). Located in the far west end of the state I routinely worked the east coast (475 miles) very well. You might consider this alternative. 73 Ray Crepeau, K1HG (ex WB1HGO) _________________________________________________________________________ Jeff Maass (jmaass@freenet.columbus.oh.us) Amateur Radio K8ND USPSA/IPSC # L-1192 NROI/CRO NW of Columbus Ohio 25000 Members in 2000! -- CQ-Contest on WWW: http://www.contesting.com/_cq-contest/ Administrative requests: cq-contest-REQUEST@contesting.com