Bravo, John! Well stated on all points. No disparaging comments noted. I
especially appreciate your discussion of RDF and what it actually means in
practice.
As you commented, in practice, RDF is calculated (EZNEC, etc.) assuming
equal amplitude distribution of noise over all 3D free space.
Excellent discussion John and Terry.
Interestingly enough if you take the 8 elements in a 200 foot circle you
can optimize the peak RDF to nearly 15dB. M.T. Ma in his book outlines his
math to optimize feeds for the specific purpose of maximizing directivity.
Using his mathematics
All this discussion about RDF overlooks the issue of
polarization. If you make an array of verticals
with a certain RDF (assuming noise comes from all
directions uniformly), the array will be better than an
individual vertical by the RDF factor. However, what
I have found is that a horizontally
Good points about polarization. If the signals and/or noise are polarized
predominantly in one state, then RDF may not be a good predictor of SNR
performance, particularly if the antenna receives predominantly in an
orthogonal polarization. On the other hand, if the polarization state of
the
Hi guys
Polarization does play a lot on 160m for two reasons. I can say that because
I am using my HWF (two horizontal flags end fire) since 2009. The first one
is local man made noise that propagate only vertical due the attenuation on
the horizontal component near the ground. And Second the DX
I forgot to mention another very important development. My friend N8PR is
experiencing with the WF in another level, Peter is using a rotator to turn
the WF vertical to horizontal. He worked FT4TA on 160m with the WF at 45
degree polarization, (not elevation, the rotor turns axial) and only 45
Well I disagree that gain isn't important. Maybe you topbanders in the
better areas of propagation can afford to throw away many db to get a
better rdf, but that sure isn't the case up here in mid-northern VE6 land.
I have numerous receive antennas including many beverages and Wellbrook
loops
My experience is similar to Don's outlined below. Both gain and noise
figure are important in very low noise environments. In my own case, I have
a noise floor from my TX array in the high -120s or -130s assuming a quiet
atmosphere. A high RDF performance RX array often brings virtually no
Which does radiolocation mean? Radar or loran/GPS/etc. or both?
Not obvious.
Rick N6RK
LORAN was a system of radionavigation, not radiolocation. Not the same thing.
Radionavigation is just what it says, a system used to help navigate a moving
ship, plane or land vehicle. It was a useful
Their meaning with respect to gain as unimportant is due to the fact that
the RX antenna is all about SNR maximization. A low noise preamp can fix
overall signal weakness, if your rig's preamps are insufficient.
73/jeff/ac0c
www.ac0c.com
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