Jerry Stuckle wrote:
On 11/13/2014 6:12 PM, wrote:
FBMboomer wrote:
On 11/12/2014 1:50 PM, gareth wrote:
It is a truism that short antennae are poor inefficient radiators, and no
amount of infantile bluster by Americanoramuses will change that.

The truth does not need the violence of abuse to force its way down
people's throats.



A perfect example is a G5RV on 75 meters. They suck. When someone joins
our group rag chew on 75, and they have a poor signal, The first thing I
ask is "Are you using a G5RV". We all have a chuckle when they answer
yes and then ask how we knew. :-)


False logic. You don't know how many people with good signals are using
G5RV's, because you only ask those with poor signals.

Trying to prove with math that short antennae work as well as say a 1/2
wave dipole may give someone great sport. However, in the real world,
short antennae suck big time. I have been an American for most of my
life. Please do not paint us all with the same brush.

Yes and no. Depending on their design, short antennas can be very
efficient. See
http://www.futurity.org/radio-wave-c...phones-801322/ for an
example.

But others are correct. The antenna itself is an efficient radiator;
it's the matching network that lowers *antenna system* efficiency.


Any dipole type antenna will suck on 75M if mounted less than about
100 feet, or about .4 wavelengths. Below that you are warming clouds.


So now it's 100 feet? It used to be 60 feet. But I have proof that is
not the case. So do a lot of other hams I know.

Your "facts" are for an idealized installation. Reality is much
different, and will never get the ideal specifications you claim.

For a dipole over average ground:

Height Gain @ Elevation
lambda

0.1 3.89 90
0.15 5.55 90
0.2 5.95 90
0.25 5.81 62
0.3 5.80 48
0.35 6.00 40
0.4 6.38 35
0.45 6.86 31
0.5 7.41 28
0.55 7.76 25
0.6 7.87 23
0.65 7.76 21
0.7 7.54 20
0.75 7.30 18
0.8 7.16 17
0.85 7.15 16
0.9 7.26 15
0.95 7.47 15
1 7.71 14

At 75M .4 lambda is about 100 feet.

Generally for DX a takeoff angle of 30 degrees or less is the rule of
thumb for best general performance.

Of course the antenna still "works" at other heights, but if DX is what
you want to achieve, then best results, on the average over average
ground, the antenna will work best for that at a height of .5 lambda
or better.

Now is you happen to be in a salt water marsh surrounded by 100 foot
tall steel blimp hangers, your results may vary.


--
Jim Pennino