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

[kq2m at kq2m.com]

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