Bruce, A couple of comments if I may on the web page you included a link to. These are based upon over 32 years of Beverage use, simplistic observations to detailed testing.
If the Beverage is being used as a single direction terminated antenna, the termination resistance is controlled more by ground conductivity, than wire height. A poor conductivity earth termination would typically be 350 ohms or lower. A more conductive earth termination would typically be 450 ohms or higher ** Ive measured 250-275 Ohms ground resistance here. This is with a 1-2' covering of rocky and sandy earth over solid rock.....about as poor as you can get outside of a city. Its almost always moist thru the woods. Beverage antennas require the bending of radio waves to work. Poor conductivity earth provides the necessary bending ** The term used is wave tilt and that is what produces the voltage on the wire. A perfectly vertical wave front such as over sea water would produce very little voltage. Too much tilt reduces the maximum length. When obtaining a Beverage antenna transformer, check the earth conductivity value published for your area. Use a 450 ohm transformer for a more conductive location. Use a 330/350 ohm transformer for a low conductivity location. Matching to the transformer will increase the signal to your radio, but will not change the antenna pattern. ** While a small mismatch is not a problem a substantial one will affect the F/B. Beverage antennas are low impedance, low Q devices, and do not couple well. Beverage runs can cross each other if a few feet of clearance is allowed ** Antenna impedance is only a few Ohms. a.. Radial fields radiate energy from the connected vertical. Avoid running a receive antenna, or receive coax across one. (Raised radials radiate more signal energy than in ground radials.) ** Ive found that to be not the case here where a Beverage runs under elevated radials with about 6' seperation. One direction picks up crud from a neighbor and the other points over a few miles of woods and is dead quiet. The same is stated in the current ON4UN book. Perhaps a sufficient number of radials are required to shield the Beverage from the vertical. a.. Take care not to transmit into a Beverage antenna with standard transformers. If transmit is desired, an antenna tuner can be used in place of the Beverage transformer. A much higher wattage termination resistor is needed. (Beverage antennas have negative gains) ** But they can be used to transmit as proven by Belrose and the Canadian government. Ive made 160 and 80M contacts using 750-1500' Beverages; no DX but decent US reports. I made my own binocular core transformers from large 43 mix beads of the type that fit over RG-213 and used large non inductive military surplus resistors at the other end. Ran fine at 100W, cooked some transformer wire at 1200W in the one test I tried at that power! In Northern climates, use a long ground rod as winter time frozen earth does not conduct well. If it is not possible to drive a rod all the way in, avoid leaving a large amount above the ground. (Short metal lengths can pick up signals like AM car radio antennas did years ago) ** If solid rock is in the way drive them in at an angle, Ive even had to do that for the power line ground. For my particular soil, or lack of, I cut an 8' rod in half, drive at an angle and attach 3-4 30-50' radials to each fanned out in front. Rods are 15' apart. Standard (best) wire lengths for a Beverage from the tables available are 290, 440, 600, 800 feet. ** There is no such thing as magic lengths, every installation is different. With a well established ground reference, a proper termination and an accurate matching transformer there should be no ideal lengths since the system is totally nonresonant. Mine are approximately 600, 700, 750 and 900' and there is no observable difference. Covered wires may somewhat reduce noise in areas where rain or snow static are a problem. ** Thats an old myth which I bought into decades ago. Then I installed parallel 750' wires about 10' apart, one using black jacketed #12 copperweld rural telephone wire and the other bare #14 stranded copperweld. Absolutely no difference in a few years of comparisons. The same with inverted vees using the same materials. Bare #14 stranded Copperweld Beverages or regular wires in the air did seem to attract lightning induced (no direct hits) damage more as noted by broken strands showing molten ends and a relatively short life of 5-6 years. The telephone wire has been used at 2 locations with some over 32 years old. For those using individual wires one of the better wire coverings is THHN. This covering is tough, thin and light. Covered wire results in a slowing of radio waves known as velocity factor. ** Long proven to be about 3-4% increase in VP. A given covered wire length will resonate lower in frequency than uncovered wire. ** Only in a resonant antenna such as a dipole. A Beverage is nonresonant or anti-resonant for the blokes in the UK, VK, etc Much of the expense of a two wire Beverage is the cost of the wire, and upkeep. 450 ohm cable expense is high, and breakage repair is difficult. WD-1 wire is inexpensive, but repair is somewhat difficult. ** WD-1A is .10/ft and up thru dealers which isnt exactly cheap when several thousand feet are needed. I finally scored a NOS 2 km reel for $45. Army guys can splice it in minutes when the bullets are flying. Electric fence wire spaced about 6-10 inches (depending upon wire size) has an impedance about 600 ohms, and is available for about $22.00 for 1/4 mile at farm supply stores. It splices easliy, and can be soldered with a torch. ** The galvanized steel wire has a finite life in some enviroments and its RF resistance adds to the wave tilt so total lengths have to be less than copper before reversal takes place. The economy route using electric fence wire has an extra benefit. As noted in "Low Band DXing", early two wire Beverage antennas, often, at the far end, had one wire insulated and one grounded. ** Which has since been proven as a poor way to do it. For economy in a small space the Slinky Beverage does very well. Five large ones stretched over about 175' approximates a full wavelength and are very quiet. VP computes to .57 which means you dont want to add more Slinkys at least at that turns pitch. Close spaced wires gave less signal and front to back ratio than wider spaced Beverage wires that gave good results without a refelection transformer. ** Say what?? Close spaced has no effect on signal strength as proven by all using WD-1A and similar which is about 93 Ohms impedance. Wide spaced loses the balanced line effect as each wire now has a portion of antenna mode current. Plus the close spaced lines naturally twist during install which further aids balance. a.. Longer BOG antennas loose signal strength. One that works well on 160 meters, may be lower signal strength on 80 meters and possibly reverse direction on 40 meters. ** Again that is very ground dependent. My 600' BOG that is on leaves (actually mostly under the recent fallings)and very low ground cover shows only a few dB less signal than one at 6'. Buried under the snow for months last winter had no effect either. I dont use any preamps unless its to make up bandpass filter loss that are usually switched out except during contests or when BCB signals are extremely strong. Installed a 50 to 50 ohm isolation transformer in the BOG antenna coax cable at the shack end. This solved TV and house noise picked up by the coax.(Reduction of Common mode pick up) ** With binocular core transformers using sleeves to minimize interwinding capacitance and proper seperation of antenna and coax grounds is the first place to start. If there is any pickup on feedlines that are disconnected from the Beverages there is a problem to be corrected. The 1:1 isolation transformers shouldnt be necessary unless something is amiss such as water corroded shields or ground loops. I use a 750' run on the ground of 1/2" CATV hardline back to the house and individual antenna feeds are elevated runs of RG-6 quad shield and flooded and using Thomas & Betts F connectors. Prior attempts at ground runs resulted in critter destruction. The 1/2" line has been there 22 years. (One wavelength for 160 meters in free space is 537.4 feet, times the mid coast Maine .4614 velocity factor for field telephone wire on the ground equals 247.9 feet). On going research of a 247 foot, two wire, two direction BOG has ended. Earth freezing caused pattern changes, but found it useable for many DX contacts. ** How did you determine the VP? It will be interesting to see how my 2 wire BOG's survive this winters ice age. Carl KM1H ----- Original Message ----- From: "Bruce" <[email protected]> To: <[email protected]> Sent: Friday, November 18, 2011 1:28 PM Subject: Topband: Bog wire >I also have found the BOG antenna to be quieter than my up in the air > Beverages. In some types of thunderstorm QRN I have been able to make DX > contacts when copy was not possible on other Beverages. Self termination > varies with ground conditions. Trying to resonate a BOG is like chasing a > butterfly, as ground conditions are constantly changing. The non resonant > approach is working well, > my BOG length is now 160 feet. Low Banders in my area are using from 134 > to 160 foot lengths. > An earlier experiment with a two wire, two direction 247 foot BOG went > well > until late winter when snow melting and re-freezing took place. Then self > termination, and pattern changes took place. Best length varies with local > ground conditions and bands of interest.... ( Non-conductive sands of Cape > Cod, and Florida would be near the BOG optimum) > They are easy to install, low maintenance, and rarely gets damaged. > Beverage notes www.qsl.net/k1fz/beveragenotes.html > 73 Bruce > > > >> Ive had a single wire 600' BOG for a bit over a year and I must say Im >> impressed. > Carl >> KM1H > > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1411 / Virus Database: 2092/4024 - Release Date: 11/18/11 > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
