This was one of the most entertaining posts I have read on any and all of the forums I attend.
Well done, and well said! 73, Gary KA1J > Sorry for getting in on this late. Various forms of wife-inspired > busy-ness. > > The real kicker here isn't the pattern, it's LOSS. It is helpful when > mentally eyeballing an installation like this to see it in *wavelengths* > rather than linear feet. > > The distance that a dielectric material can be from the radiating source > and cause a given degree of loss increases with increasing wavelength. It > all has to do with how much total energy it takes to raise the molecular > energy of a dielectric molecule to the next level. > > While the energy level at a distance is weaker, if the push is for a long > enough time, the weaker energy of the radiation multiplied by time can > accomplish the raise to the molecular next level. Since a 160 meter signal > is pushing in one direction much longer during the half cycle than the > microwave signal in your microwave oven, you don't have to be in the two > foot box to get dielectric effects. The math is really nasty, and it's not > a linear reduction formula but linear is close enough to *characterize* the > damage in loss by "not high enough" or wrong polarization. > > A pair of vastly shortened MA160V radiators produces a heavily loaded 72' > dipole at 55 feet in your example. That's approximately a 1/8 wave dipole > at a height of 1/10 wavelength. > > To visualize, let's convert that to the ten meter band, where the > wavelength is 33 feet, to get the real view of what's going on. That ten > meter antenna would be a four foot loaded dipole supported at a height of > forty inches above ground. You tell me how well that ten meter antenna is > going to get out, and whether you think it will heat up the ground. > > Prior comments about the cloud burner pattern are correct, but even worse > it's a severely weakened cloud-burner antenna. And for 160m there's more. > > Famously, W8JI put up a 160 dipole that was up a little over a half wave, > supported from the tops of two appropriately spaced 300 foot towers. His > analysis, after using that and his excellent vertical antenna farm in > innumerable A/B tests, was that the dipole RARELY EQUALED the verticals in > signal strength. > > There are reasons why 160 meters goes vertically polarized, and the > efficiency of the counterpoise is the first, second, and third place > consideration in what to do and where to put it. > > With the right counterpoise (another very very long discussion) the MA160V > can be made to work halfway decently. The hint here is that shortened > antennas have a very low real radiation resistance, meaning higher current > for the same *radiated* power, and higher local RF field intensity because > it's not spread out as much as a quarter wavelength radiator. > > Thimble summary of long long counterpoise discussion? > > Do not screw around with any aspect of gimpy, underfunded, half-a**ed, > afterthought, miscellaneous, irregular, undersized counterpoise on 160m. > > Counterpoise is the 1000 pound gorilla in a room otherwise occupied by mice > and small monkeys. Guess who's crushing chairs and hammering the piano into > toothpicks. Treat the Gorilla right or the Gorilla will make you pay. > Doesn't matter whether you're a really nice guy, or gave to the PBA and the > bell-ringers, and coach a little league team, and you're the best dad there > ever was. Screw around with the counterpoise and the Gorilla will make you > pay. Every time. > > Don't believe this? Free country for sure. And it's fun to experiment. Just > be sure and come back and let us know your 160 operation in one or the > other of the 160 contests with that antenna so we can look up your RBN > numbers and put a dB cost to the experiment. > > The tipping point in the decision is whether you truly enjoy trying > something different in antennas just to see for yourself what happens (go > for it!), or you are trying to do something in restricted circumstances and > your REAL goal is getting quickly to actual radiated power adequate for > your choice of QSO's. > > In any event, good luck and have fun. > > 73, Guy K2AV > > > On Tue, May 24, 2016 at 1:02 PM, GALE STEWARD via Topband < > [email protected]> wrote: > > > Totally agree. It would have to A LOT higher to obtain anything but a > > cloud warming radiation pattern. > > Stew K3ND > > > > From: Hardy Landskov <[email protected]> > > To: [email protected]; [email protected] > > Sent: Tuesday, May 24, 2016 11:58 AM > > Subject: Re: Topband: ma160v > > > > Don't waste your time & $$. It's a cloud warmer which is good SS contests & > > local QSO parties. > > 73 N7RT > > > > -----Original Message----- > > From: Topband [mailto:[email protected]] On Behalf Of > > [email protected] > > Sent: Monday, May 23, 2016 9:40 PM > > To: [email protected] > > Subject: Topband: ma160v > > > > Hi all.I currently have 1 cushcraft ma160v,as you all know this is a > > cushcraft 160 vertical.I just recently aqquired a second.Now,has > > anyonetried > > a rotatable dipole using 2 of these.The idea intrigues me.I could mount > > this > > on a 55 ft tower.The only other antennas are a m2 6 mtr > > 2 klm's 2 mtr and a 432 m2.So there should not be any interaction.What does > > the group think? any ideas? a waste of time? your thoughts..73 john w5jmw > > > > _________________ > > Topband Reflector Archives - http://www.contesting.com/_topband > > > > _________________ > > Topband Reflector Archives - http://www.contesting.com/_topband > > > > > > > > _________________ > > Topband Reflector Archives - http://www.contesting.com/_topband > > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > _________________ Topband Reflector Archives - http://www.contesting.com/_topband
