X-ListName: Amateur Radio discussion list Warnings-To: <> Errors-To: owner-cq-contest@tgv.com Sender: owner-cq-contest@tgv.com Date: Mon, 14 Aug 1995 19:24:34 -0400 (EDT) From: Frank Donovan Reply-To: Frank Donovan To: reflector Subject: Phased Beverages! (was: EVE vs Beverage?) If u want to try a really excellent receiving antenna try a pair of phased Beverages! A pair of 580 foot Beverages, fed in phase, with sloped feeds and terminations, spaced 275 feet side-by-side, shows a pattern remarkably similar to a 3 element Yagi! The side-by-side spaced in-phase Beverages result in nearly total cancellation of signals arriving from the sides. The sloped feeds and terminations (for about 60 feet) are critical to obtaining excellent front-to-back ratio. This same concept will work on 80 or 40 meters (or even higher frequencies!) by scaling the dimensions. You can model Beverage antennas and other antennas in close proximity to the Earth with EZNEC or AO among others. MININEC based models WILL NOT model Beverages or other antennas close to the ground. 73! Frank W3LPL donovanf@sgate.com Date: Tue, 15 Aug 1995 06:35:00 -0400 (EDT) From: Frank Donovan To: Patrick Collins Subject: Re: Phased Beverages! (was: EVE vs Beverage?) Hi Pat! Half wave spacing is what you want (275 feet on 160M), regardless of Beverage length. With this spacing, signals arriving off the side of the phased Beverages will be 180 degrees out of phase. A pair of 1000 foot Beverages will have quite a narrow beamwidth, so u mite want to preserve the ability to run a single Beverage as well! For those who do not use 3 element Yagis on 40M, you can get similar receive performance with a phased pair of 145 foot Beverages spaced 70 feet side-by-side. The same idea will work on 20 meters, if u scale it down. BTW, several large military facilities use very large Beverage receiving arrays up to 30 MHz and higher to obtain low sidelobe performance (about -40 dB) with narrow beamwidths! 73! Frank W3LPL donovanf@sgate.com Hi Rich! First u need to describe what you mean by "better"! A pair of phased Beverages longer than 580 feet on 160M will produce narrower beamwidth, if that is what you desire... 875 feet is a good choice if u want to go longer than 580 feet, although the exact length is not critical. As W1WCR first pointed out in his "Beverage Antenna Handbook," certain Beverage lengths produce a very desirable "cone of silence" at the rear of the antenna. 580 and 875 feet are two such desired lengths on 160M. Corresponding lengths on 80M are 295 and 440 feet. Four phased Beverages will produce still narrower beamwidth; however, it will be difficult to retain the excellent side rejection of the pair. In this case, perhaps more is not better! I've always used insulated copper wire for my Beverages.. I do not plan to use anything else... However, I would be interested in results with other types of wire. 73! Frank W3LPL donovanf@sgate.com Hi Joe! Thanx for the note, your plans for your new Beverage CONTEST antennas sound great to me! If u do not terminate a Beverage, u don't need to slope either end! The slope affects only front-to-back ratio, and u will have minimal f/b without termination! I slope my terminated Beverages for approximately the last 60 feet at each end. The EZNEC model clearly shows the improvement in f/b ratio resulting from the slope; however, I haven't attempted to use EZNEC to determine optimum slope. I've never tried the concrete-filled bucket approach for temporary Beverage supports, but it sounds like a good idea to me! I remove my Beverages during mowing season, using steel fence posts that I install every October and remove every April! I add two foot fiberglas extensions to the top of seven foot steel T-posts. I know other Beverage users have used concrete-filled buckets, perhaps they will comment on the pros and cons of that approach... Good luck! Frank W3LPL donovanf@sgate.com Hi Steve! Thanx for your note! The choice of Beverage length involves many factors, some of which include: - Minimum length to produce useful pattern, probably 400 feet or so on 160M which results in a 3 dB beamwidth of 100 degrees or so... Short Beverages tend to be quite inefficient... so a preamp may be desirable! - Optimum length to produce the "cone of silence" mode first published by W1WCR in his "Beverage Antenna handbook," about 580 or 875 feet on 160M. - Optimum length to produce the desired beamwidth. On 160M a 400 foot Beverage has a 3 dB beamwidth of about 100 degrees, a 580 foot Beverage has a 3 dB beamwidth of about 80 degrees and a 875 foot Beverage has a 3 dB beamwidth of about 70 degrees. Several amateurs have reported good success on 160M with Beverages of 1500 feet or more! At some point, the slow wave velocity propagating down the Beverage begins to deteriorate the low angle performance of the Beverage... Perhaps 2000 feet or so is the maximum useful length on 160M before narrow beamwidth and poor low angle response destroy the utility of the antenna. Phased Beverages offer a very attractive alternative to very long Beverages, by reducing the beamwidth, cancelling the pickup off the sides, increasing the signal level by 3 dB, and avoiding the poor low angle response of long single Beverages. W3LPL I'm not sure there is an particular "optimal" height... >From what I've read, very low Beverages (one meter or less) have excellent patterns (sidelobes and front-to-back) but very poor efficiency. If very low Beverages are practical at your QTH, efficiency can be significantly improved by using a multi-wire Beverage rather than a single wire Beverage. In this case I'm not referring to 1/2 wave-spaced phased Beverages, but to several close spaced Beverages (typically three). You simple space the three Beverages side-by side, spaced from each other by a distance equal to twice their height. Ground losses of the three wire Beverage configuration are about 3 to 4 dB less than a single wire Beverage. Simple join the three wires at each end by sloping the wires toward the common feed point at one end and towards the termination at the other end. Sidelobes and front-to-back should be acceptible on 160M at Beverage heights of 3 to 5 meters. Heights above 2 to 3 meters are probably undesirable on 80M and two meters is probably a little too high on 40M for good sidelobe and f/b! In my case, its very inconvenient and perhaps a bit dangerous to place my Beverages below head-height (for humans and animals - we have lots of deer who get tangled up in my Beverages every year)! So I place my Beverages at about 2 meters height, with the last 16 meters at each end sloped down to ground leve at the feed and termination ends. 73 Frank W3LPL Hi Rich! I use separate phased Beverage (note the capitalization, this is a man's name!) arrays on 160M, 80M and 40M. (hey... why do u refer to 80M as 75M??? 300 divided by 3.75 = 80 !!! Or have ur SS interests caused to to forget about (80M!) freqs below 3900 kHz?) If u are planning to use a simple Beverage antenna, as opposed to phased Beverages, u can certainly use a 580 foot Beverage on both 80 and 160. A 580 foot Beverage antenna works very well on 80M although a 580 foot Beverage antenna (not array) isn't long enuf to work particularly well on 160M... A pair of phased 580 foot Beverages with 270 spacing makes a fabulous 160M receiving antenna however, likewise a pair of 295 or 440 foot Beverages with 135 foot spacing on 80M! N2RM uses a pair of phased Beverages with compromise spacing that work well on both 80 and 160. Here are some factors to keep in mind when selecting Beverage antenna length: 1. As W1WCR points out in his Beverage Antenna Handbook (results easily confirmable with EZNEC), certain preferred lengths produce a very desirable "cone of silence" off the back of the antenna. The preferred cone of silence lengths are (it is NOT necessary to use precision lengths, furthermore, ideal Beverage antenna length is somewhat affected by local ground conditions!): 160M: 290 ft, 585 ft, 880 ft, 1160 ft 80M: 150 ft, 295 ft, 440 ft, 580 ft 40M: 75 ft, 150 ft, 225 ft, 295 ft 2. Longer Beverage antennas produce POORER front-to back ratios! Beyond the minimum useful Beverage length (the first length in 1 above), about 3 to 4 dB of front-to-back is lost each time the length of the Beverage is doubled! As a result, the first two "cone of silence" lengths would be preferred if (but only if!) front-to-back were the primary design factor... 3. Short Beverage antennas have a very broad main lobe, poorer response to low angle signals and lower sensitivity... Of the four lengths listed under number 1 above, the shortest length has a 3 dB beamwidth of almost 180 degrees, not very desirable! The second length has a 110 degree beamwidth (better, but still not good...), the third length has an 80 degree beamwidth and the longest length has very desirable 50 degree beamwidth (but only 17-18 dB front-to-back ratio...). The clear advantage of phased half-wavelength-spaced pairs of Beverages is that you get the front-to-back ratio advantage of short Beverages, the narrow beamwidth and sensitivity of long Beverages, and the fantastic front-to-side ratio resulting from the phased pairs that is unavailable with any single Beverage antenna length! In summary: On 160M I'd suggest phased 585 or 880 foot Beverages spaced 270 ft. On 80M the preferred phased Beverage lengths are 295 or 440 feet, spaced 135 ft On 40M the preferred phased Beverage lengths are 150 ft or 225 ft spaced 70 ft. N2RM's compromise of two 580 foot Beverages spaced 200 feet is a proven performer on both 80 and 160. 73! Frank W3LPL donovanf@sgate.com Hello Mario! I haven't tried to develop a physical explanation of why certain Beverage lengths produce a "cone of silence" at specific frequencies! The lengths result from computer-based optimization! A velocity factor of 0.89 was used for the optimization, which is typical for Beverage antennas. Beverage antennas used in non-amateur applications really cannot take advantage of the cone of silence property, because the phenomenon occurs over a relatively narrow bandwidth, which is inconsistent with non-amateur applications for the most part. 73! Frank W3LPL Subject: Beverage kit I have been amused by all the discussion regarding whether Beverages should be made of copper or aluminum or steel wire. Copper seems to be the wire of choice and doesn't cost that much anyway. I built my first Beverage this past year. It was so easy I can't believe I lived without one. Here's how to do it: - Go to Home Depot (or other large hardware store) and buy 500 ft roll #16 THHN or MTW wire. It's available in every color you can imagine for about $15 per 500/ft roll. - Go to local feed store and get some electric fence insulators. This cost me about $3. - Call your favorite radio dealer and order an ICE Beverage matching box. Cost about $30. - Go to Radio Shack and get a 400-600 ohm resistor. I actually used four (4) 2K ohm resistors in parallel! Roll out the wire in the desired direction. Mount the fence insulators to convenient trees (my Beverage is not perfectly straight) about 7-9 feet up. Connect one end of the wire to ground through the resistor. Connect the other end to the matching box. Connect coax. Enjoy! I did follow the conventional wisdom of sloping the ends down. I used 4 foot ground rods at each end. I only have room for a 500 foot run. W3LPL has pointed out that 580' might be a better length. Simple to solder some more wire on. This antenna makes 80 and 160 enjoyable. Less than $50 to hear Europeans all summer on the LF bands seems like a good deal if you have the space. When the antenna broke this summer, I used a split bolt connector to join the two pieces back together. You can find these for about $1 in the electrical aisle of the Home Depot (or hardware store). No solder required! Randy Thompson, K5ZD k5zd@iconics.com