Topband
[Top] [All Lists]

Re: Topband: ma160v

To: Topband@contesting.com
Subject: Re: Topband: ma160v
From: "Gary Smith" <Gary@ka1j.com>
Reply-to: Gary@ka1j.com
Date: Tue, 24 May 2016 23:12:57 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
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 <
> topband@contesting.com> wrote:
> 
> > Totally agree. It would have to A LOT higher to obtain anything but a
> > cloud warming radiation pattern.
> > Stew K3ND
> >
> >       From: Hardy Landskov <n7rt@cox.net>
> >  To: w5jmw@towerfarm.net; topband@contesting.com
> >  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:topband-bounces@contesting.com] On Behalf Of
> > w5jmw@towerfarm.net
> > Sent: Monday, May 23, 2016 9:40 PM
> > To: topband@contesting.com
> > 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

<Prev in Thread] Current Thread [Next in Thread>