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

[Jim Brown]

On 12/4/2021 3:09 PM, kq2m at kq2m.com wrote:
> 
> 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?

I've always seen 550 ft as an ideal length for 160. I have one of that 
length, another 50 ft shorter.
> 
> 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.

NI6T, W6GJB, and I all have rather irregular terrain. Our Beverages work 
just fine. In the words of NI6T, a LONG time 160 op who lives DEEP in a 
ravine but has something like 240 countries on topband, "Any Beverage is 
better than no Beverage." Gary's and Glen's terrain is very dense like 
yours.
> 
> 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.

Don't worry too much about height. Mine start off 5-6 ft high, get low, 
run downhill for a while, then elevated to 15-20 ft over a ravine, 
eventually terminating near the top of the ravine.

> 
> 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?

Study W3LPL's excellent talks at Dayton on a half dozen or so RX antenna 
types. He notes that some RX systems are bothered by nearby surroundings 
(trees, etc.) while others are not. This a "must study."
> 
> 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.

Mine (two reversibles using DXE hardware) cross each other within 30 ft 
of my 120 ft tower. They work.
> 
> 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.

Some of my RG6 runs along a wood fence and then is elevated to clear my 
driveway and enter the shack, but most of it runs on the ground. It's 
the direct burial type that has the sticky goo in it, that varmints 
don't seem to like.
> 
> 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?

Study the texts on Beverages. There's a terminating resistor that serves 
to match it. Beverages DO work better with termination, but again, any 
termination is better than no termination. At PJ4A, the ground is 
volcanic rock, making driving a rod difficult. The guys terminate them 
with a few short radials. More might be better.
> 
> 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?

My EU/VK Beverage works all the way up to 20M -- I used it a lot to copy 
EU when all I had for TX was a high dipole. They get narrower as they go 
up in frequency.
> 
> 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.

I have a pair of VE3DO loops spaced 5/8 wavelength for 160, steered with 
an NCC-1 box. They work well when something hasn't fallen on them.:) 
They are written up on my website, k9yc.com/publish.htm
> 
> They are challenging questions that are not really covered in anything 
> that I have read.  I would appreciate all of your thoughts and insights!

It's worth doing more reading. The ON4UN book has a lot on Beverages and 
other RX antennas. W3LPL and N0AX recently authored a QST piece on 
Beverages.

73, Jim K9YC