Topband: New 160M high performance receiving antenna at W3LPL

[donovanf at starpower.net]

Hi Tom,

You've surely built and evaluated more BSEF and 8-circle receiving arrays than any of the rest of us.  I'm very new to them and after just a few days of evaluation I'm delighted with the results of my new BSEF receiving array consisting of four 25 foot W8JI umbrella verticals spaced 300 feet x 130 feet.  I still have my 900 foot Beverages, but so far the performance of my new BSEF receiving array is consistently superior. 

I used a pair of 270 foot spaced broadside 580 foot Beverages for several years but the improvement was insignificant compared to a single 580 foot Beverage.  I replaced them with single 900 foot Beverages which perform slightly better than the 580 foot Beverages.  I have inadequate space for more widely spaced broadside Beverages.

If you were to install a new BSEF receiving array using four W8JI inductive/resistive loaded 25 foot umbrella verticals (not an 8-circle array) what spacings and fixed phasing would you use based on your experience and evaluations?

tks

73
Frank
W3LPL

---- Original message ----
>Date: Sat, 2 Feb 2013 23:58:15 -0500
>From: "Tom W8JI" <w8ji at w8ji.com>  
>Subject: Re: Topband: New 160M high performance receiving antenna at W3LPL  
>To: <donovanf at starpower.net>, <topband at contesting.com>
>Cc: Don Johnson <n4dj at me.com>
>
>> In W8JI's very rural area minimum main lobe beamwidth is more valuable to 
>> him than minimum sidelobes.  Tom's choice of 330 foot broadside spacing in 
>> a very rural area with little or no local RFI makes lots of sense.
>>
>
>I actually use a little more than 330 ft now in that array, and considerably 
>more spacing in broadside Beverage arrays.
>
>Half-wave spacing forms two nulls at ground level, directly of the sides of 
>the array. You have ONE null on each side at ground level.  Most people fail 
>to realize the side nulls at half wave spacing are at ground level only. It 
>is a less than perfectly deep null at wave angles above earth level.
>
>Wider spacing, compared to 1/2 wave spacing,  forms a null cone.  This 
>provides **two nulls** at ground level off each of the sides (now you double 
>the chances of groundwave noise being in a null).  Even more important, the 
>side null forms a cone that reaches maximum elevation off the side.
>
>This means directly off the side of an array, WIDER spacing gives a deeper 
>null. This is contarary to what most people assume, because they look at the 
>null as a ground wave side problem. People tend to overlook the fact that 
>distant signals and noise come from angles higher than zero degrees 
>elevation.
>
>They also overlook the fact that a wider spacing provides four groundwave 
>nulls (two on each side), instead of just two nulls (one on each side) of 
>1/2 wave spacing.
>
>I can't think of a single case, besides a single groundwave noise source 
>directly off the side, where 1/2 wave spacing would be an advantage.
>
><<<
>If you look at end-fire cell patterns, you will find closer spacing gives 
>more directivity.  It is easier to have a wider null area with somewhat 
>closer spacing.>>>
>
>Right.
>
>
>
>> End fire spacing has essentially no effect on beamwidth and sidelobe 
>> levels, so Tom's choice of 70 foot end-fire spacing makes little if any 
>> measurable difference compared to 130 foot end-fire spacing.  Larger 
>> end-fire spacing (up to 1/4 wavelength) is somewhat more forgiving of 
>> phasing errors and mismatched signal levels and slightly more 
>> efficient.>>>
>
>Actually there is another very common myth or mistaken assumption about 
>phasing. We assume phase difference between elements should be 180-s where s 
>is electrical degrees spacing. We assume with quarter wave (90 degree) 
>spacing we want 180-90 = 90 degree phase difference, or with 45 degree 
>spacing we want 180-45 = 135 degree phasing. Once again, despite being in 
>countless articles and books, this is almost always NOT optimum. The only 
>case where it is optimum is where we want a single zero wave angle null 
>directly off the back.
>
>This is almost never the case, because as with 1/2 wave broadside spacing, 
>this forms only ONE null at zero elevation. By increasing phase delay we 
>split the back null into TWO nulls at zero angle, and have a null cone that 
>is elevated directly off the back about the same as the zero elevation nulls 
>are angled off the side.
>
>It's really pretty silly, when we think about it for a while, to design 
>skywave systems or noise rejection systems that have a single groundwave 
>null peak. What almost any case demands is a null covering the widest 
>possible area, and to absolutely be above zero elevation. This not only does 
>a better job of notching unwanted signals and noise from skywave, it also 
>doubles the null area on the ground for local noise.
>
>If I had multiple groundwave noise sources, I would not use 1/2 wave 
>broadside spacing. I would use wider spacing.
>If I had skywave side signals to reject, I would not use 1/2 wave broadside 
>spacing.
>
>The only case I would use 1/2 wave spacing would be ground wave noise 
>exactly off the sides, and nowhere else.
>
>If I had multiple groundwave noise sources, I would not use 180-s phasing or 
>1/4 wave endfire spacing. I would use narrower spacing and use a phase delay 
>of some number greater than 180 - s.
>If I had skywave signals or noise to reject, I would not use 180-s phasing 
>or 1/4 wave endfire spacing. I would use narrower spacing and use a phase 
>delay of some number greater than 180 - s.
>
>The only case I would use 180-s phasing would be a ground wave signal 
>exactly in line with the element's endfire spacing. That would be a single 
>signal condition.
>
>This about the problem in three dimensions, and it is easy to see why 1/2 
>wave broadside and a 90 deg space 90 deg lag system is almost never the best 
>choice. Even my 45 degree spaced elements are not delayed 135 degrees, but 
>rather some larger delay amount. This actually increases null depth and the 
>statistical likelihood something unwanted is in a deep null.
>
>73 Tom 
>
>_________________
>Topband Reflector