[TowerTalk] Questions on Low band receiving antennas in forests and wetlands along ridgelines and ravines.

Alan Swinger awswinger at earthlink.net
Mon Dec 6 14:44:36 EST 2021


You may want to consider the K9AY Loop system -  ~25ft radius and switchable in 4 directions. Have had one for yrs in and among trees and find it very helpful on the low bands in Diversity receive. I think Array Solutions carries. - Alan K9MBQ
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Sent: Dec 5, 2021 10:25 PM
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Subject: Re: [TowerTalk] Questions on Low band receiving antennas in forests and wetlands along ridgelines and ravines.
 
Hi John,
 
That presentation was great, as was the article with Frank and Ward. TY for the links to both!
 
73
 
Bob, KQ2M
 
 
On 2021-12-05 17:00, john at kk9a.com wrote:
> W3LPL has a lot of Beverage information in his low band presentation.
> > http://www.k3lr.com/Dayton/Dayton2016/w3lpl.pdf
> > John KK9A
> > kq2m wrote:
> > I want to supplement my transmitting antennas with the most useful
> low-noise low-band receiving antennas possible that I can put up in
> dense forest and with extremely challenging topography.
> > My qth and surrounding woods are on a hilltop with extensive and > steeply
> angled jagged ledge, many ridgelines, ravines and wetlands and areas of
> standing water and marsh, varying in height from ~ 750' - 820' ASL.
> Past where I would be able to put receiving antennas, there are very
> sharp dropoffs to South and West of several hundred feet. It is
> beautiful but NIGHTMARISH to walk through the woods under the best of
> cndx (like today) but it is a true HORROW SHOW when all the thorns
> bushes and dense vegetation is growing rapidly and the Deer Ticks and
> mosquitos are everywhere. It's even worse in snow as the ledge and > rock
> slopes become exponentially more dangerous to access and there is ledge
> EVERYWHERE.
> > Complicating matters are areas of the woods that resemble the moguls on
> a ski slope only more spread out. Some of these moguls can approach > 30'
> high with the ridgelines even taller than that. While they somewhat > run
> in the same direction ENE to WSW others run on steeply sloping hills
> like a series of "steps". One ridge runs North to South on the side of
> a hill; drops 15' feet then there is a another ridge then another drop
> of 15' or so to a ravine and standing water and muck pond about 20'
> across. And there are flatter areas of ledge that have what appears to
> be a boulder on it about 5' high and 30' long right in the middle of a
> flat spot. There are a few formations like this in other areas as > well.
> The result is that there are very few areas open for more than 100' > in
> any direction without running into these rock formations and steep > hills
> and dropoffs.
> > Now that I have described the terrain, my questions will make more
> sense:
> > 1) Is that a formula specific to beverage antennas for determining
> length? Or should I used the standard dipole formula 1/2 wavelength =
> 468/ f?
> > 2) What is the effect on a terminated directional beverage (terminated
> at the back end that runs downhill at an 8% slope? If the maximum of
> the lobe is at say 15 degrees on flat ground, does the lobe maximum > drop
> to an even lower angle? Or does the lobe change? or both?
> > 3) Same question but with the beverage now running uphill at a 5% > slope.
> > 4) Same question but with a 20' high "Hump" in the middle? as the
> beverage starts and is terminated on a flat spot, runs to the top of a
> ridge and then back down again on the other side.
> > 5) If you put a phased array of verticals NW to SE (with pattern
> broadside to the direction of the elements - receiving NE) in a flat
> spot that then points directly into a 30' high ridge to the Northeast
> 50' from the front of the array, have you essentially turned a low > angle
> receiving array into a created a high angle receiving array?
> > 6) What happens when you have 4 ground mounted receive verticals with
> that large 5' boulder taking up of the space in the middle of them?
> What does that do to the pattern?
> > 7) Let's say that you have a 6 L array of receive verticals in 2 rows > of
> three with each line pointing NW to SE (pattern broadside NE) and they
> are phased. But instead of being on flat ground However, they are on
> the side of a steeply sloping hill so that the first row is at 820' asl
> and the 2nd row is in the same direction but at 800' asl. How might
> that affect the pattern? (for purposes of this question ignore the
> impact of ground being "ledge" rather than soil.
> > 8) Now lets say that you have transmitting antennas for 160, 80 and 40
> nearby. How far do the receive verticals and beverages have to
> physically be from the radials of the 160 Inv L, 80 M 4-square and from
> the 40 meter wire beam before the performance of either the > transmitting
> antennas or receiving antennas starts to degrade? A formula for
> distance in wavelengths would be most helpful.
> > 9) How far apart fractions of a wavelength do the beverages have to be
> from each other before their performance starts to degrade?
> > 10) What is the impact on beverage receive performance if the RG6 Quad
> Shield coax to the shack instead of running along the forest floor,
> instead runs horizontal and parallel to the beverage? I am thinking of
> keeping it elevated to greatly reduce the opportunity of critters to
> chew on it but I don't want to impact the performance of the beverage.
> > 11) Is there any performance advantage if I were to terminate the
> beverage with a ground rod and radials in that standing water on the
> hilltop? Or does it not make a difference?
> > Finally, I have read about many preferred beverage lengths for 40, 80
> and 160 but few if any seem to be based on an established formula to
> calculate their lengths. What formulas and multiple of wavelengths
> would you use and why?
> > 12) How many wavelengths on 40 is too long and how many is too short?
> Same question for 80? Same question for 160. I know that these > answers
> vary by band which is why I am asking.
> > They are challenging questions that are not really covered in anything
> that I have read. I would appreciate all of your thoughts and > insights!
> > Tnx & 73
> > > Bob, KQ2M
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