Topband: Non-resonant receive antennas

Thu Dec 18 09:26:40 EST 2014

I noticed JC's comment below about a low dipole as a receiving antenna.

Did I interpret that correctly?  I've read of a Dipole on the ground as a low noise receive antenna for 160 but.........can a non resonant dipole installed at low heights be better, as a receive antenna, than a vertical or L antenna? How about a non-resonant dipole, say, two feet above ground, at a length of 100 feet? Would you feed it with coax or figure out the Zo at 160 and use a suitably wound xfmr to match to 50 ohms???

Just athinkin' of ways to use available low horizontal space, albeit the available space is insufficient for a beverage.

Thoughts???  72, Jim Rodenkirch K9JWV 

> From: n4is at comcast.net
> To: jkaufmann at alum.mit.edu; topband at contesting.com
> Date: Wed, 17 Dec 2014 23:11:10 -0500
> Subject: Re: Topband: 8 circle: DXE vs Hi-Z
> 
> 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 at contesting.com] On Behalf Of John
> Kaufmann
> Sent: Wednesday, December 17, 2014 8:59 PM
> To: topband at 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 at contesting.com] On Behalf Of Richard
> (Rick) Karlquist
> Sent: Wednesday, December 17, 2014 3:19 PM
> To: Lee K7TJR; 'Terry Posey'; 'John Kaufmann'; topband at 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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