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 (large area) and the Hi-Z 4-8PRO 8 element circle. They all work
more or less as expected on the "easy" stuff and show reasonable
directivity but when I need help for the weaker dx, there just isn't any
signal there to work with. The beverages do the best of the bunch, they
aren't anything special - typically in the 700-1100 foot range. With the
many vertical structures I have there is no doubt their patterns are
somewhat affected but they seem to work fine for Eu and JA bcb dx vs the
loops and the 8 verticals. Not that this has been a good year for much of
anything on the low bands in this area.
The HI-Z was erected quite aways from anything else which involved
bushwhacking and clearing the entire circle, trenching almost 1200 feet of
feedline etc so there was a lot of sweat work done on that project. But
on 160 and 80 where I have the tx antennas to use as a comparison, the
specialized rx stuff just doesn't hear the weaker stuff. And it's not that
I have a pristine "can hear a pin drop low noise qth", esp on 160 - plenty
of flare stack ingitors plus the usual powerline and smps junk. It's
especially frustrating to hear all the glowing success stories of these rx
arrays and how they make the dx just jump out of the noise and into your
log...
73 Don
VE6JY
On Thu, Dec 18, 2014 at 4:11 AM, JC <n4is@comcast.net> wrote:
>
> 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 signal always
> come in both polarization.
> The result form the two reasons is an optimized signal to noise ration
> using
> horizontal polarization.
>
> I have both WF with the same RDF, during SR or SS there is almost no sky
> noise coming from the back because of the darkness, however local man made
> noise comes from any direction, especially if you live in a city lot like I
> do. Most of the time the noise is coming at the same direction you want to
> hear the DX, and if you add power line noise the situation deteriorates a
> lot for the VWF due vertical polarization. Using my HWF I normally get 10
> dB
> better SNR than my VWF that has the same RDF and same aperture of 74
> degree
> measures, I can turn the antenna and measure it, they are not optimized for
> best F/B, I optimized them for maximum rejection of local man made noise.
>
> The HWF is not a dipole. The two phased loops take of angle us 40 degree
> and
> there is a huge attenuation for signals above 60 degree. Low dipole is a
> huge issue if the dipole is resonant, it will interact with all other
> receiver antennas and will destroy directivity of all of them, if you want
> to use a low dipole make it not resonant. Gain in not important so it can
> be short as a 30 m dipole and still will hear the same way. Another issue
> with low dipoles is the amount of energy absorbed from the TX antenna. If
> you connect a power meter and a 50 ohms load o the low dipole and transmit
> KW on the TX antenna, you can measure several WATTS at the low dipole . You
> can burn you front end with a low resonant dipole.
>
> Adding to all that there is another very interesting observation from my
> last 5 year using a high RDF horizontal RX antenna, when the TX signal
> refract on the ionosphere the signal split in two waves, that was very well
> explained by K9LA. What I observed is that these two waves does propagate
> in
> different directions. I normally receive VK6 near my SR with better SNR
> horizontal from 210 degree SSW and with better SNR from 280 degree
> vertical.
> Sometimes the horizontal peak is 20 minutes before the vertical peak that
> is
> most of the time at my SR.
>
> 73's
> N4IS
> JC
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of John
> Kaufmann
> Sent: Wednesday, December 17, 2014 8:59 PM
> To: topband@contesting.com
> Subject: Re: Topband: 8 circle: DXE vs Hi-Z
>
> 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 signals and noise evolve randomly with no preference for any one state,
> which is often assumed for skywave signals, then RDF will be--on average--a
> good receiving metric, subject to the previous stated qualifications about
> the spatial distribution of the received noise. However, some of the past
> discussions on this reflector about preferential polarization of skywave
> signals on 160 may call into question the assumption of randomly polarized
> signals.
>
> 73, John W1FV
>
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Richard
> (Rick) Karlquist
> Sent: Wednesday, December 17, 2014 3:19 PM
> To: Lee K7TJR; 'Terry Posey'; 'John Kaufmann'; topband@contesting.com
> Subject: Re: Topband: 8 circle: DXE vs Hi-Z
>
> 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
> polarized antenna, such as a low dipole frequently receives considerably
> better than a vertical. In that case, you would be better off using an
> array of low dipoles. The reason why horizontal polarization can be better
> is that the horizontal component of terrestrial based noise is highly
> attenuated over distance as a ground wave.
>
> Rick N6RK
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