[Hi-zreceivingarraydiscussions] DIRECTIVITIY 8 CIRCLE

Sat Nov 30 21:05:15 EST 2013

Hi Lee,

Can you recommend a method of additional grounding ?  The red dirt around here sucks as ground.

I have 6 inch wide copper tape and some 2 inch tape.  I can get anything.

Thanks,
Dave Anderson, K4SV

Sent from my iPad

> On Nov 30, 2013, at 8:34 PM, "Lee  K7TJR" <k7tjr at msn.com> wrote:
> 
> I just ran some theoretical plots of the array at 1.84 MHZ. The 200 foot dia
> 8 element array shows 44 dB of F/B. Of course it is unlikely we would ever
> see that much. However I routinely see 30+ dB in practice. I scaled all
> phases on an 8 element 200 foot dia array  to 1MHz in the BCB and sure
> enough as I remembered there is little if any low angle pattern. It is
> almost circular with less than 10dB of F/B. This 8 element array was
> designed to only work from 1.8 to 2 MHz. Or 3.5 to 4 MHZ when scaled to 100
> foot dia and new delay cables.
>  Interestingly enough I have tried the Broadcast F/B determination many
> times. What I have discovered is that not all BCB stations seem to have that
> ground wave low angle and do not always show F/B on the arrays. No, I have
> not tried to figure out why. Maybe it's a mix of high angle skywave and
> ground wave. What I do know for a fact is that early morning signals
> sometimes come in at high angles and show little directivity for a period
> during sunrise.
>  A classic example of that was FT5XO that came in solid on arrays and
> beverages until late in the sunrise and then switched to no directivity and
> best reception on my TX vertical.
>  We have had some recent reports from Alaska where there is no soil only
> rock dust from glaciers. The reports showed that at low frequencies like 160
> a Hi-Z array needed some extra ground help. Adding some short radials has
> helped the situation but I remember back to my original research where I
> found radials to be pretty sensitive to placement. I also at times have
> suggested shallow burying of a plate of metal to increase the surface area
> of the element ground to the earth. My early research indicated this to be a
> bit more stable than hoping to place radials accurately. Accuracy is why
> these arrays are able to do what they do.
> Lee   K7TJR
> 
> 
> -----Original Message-----
> From: Hi-zreceivingarraydiscussions
> [mailto:hi-zreceivingarraydiscussions-bounces at hizantennas.com] On Behalf Of
> Dave Anderson, K4SV
> Sent: Saturday, November 30, 2013 4:18 PM
> To: Hi-Z Receiving Array Discussions
> Subject: Re: [Hi-zreceivingarraydiscussions] DIRECTIVITIY 8 CIRCLE
> 
> Hi Everyone,
> 
> I have had my 200' 8 circle for nearly 2 years now.  In my case I have
> installed my 4 square inside of the 8 circle.  This allows me to have both
> controllers in the same cabinet. 
> 
> For 160 meters,
> The 4 square works very well with great F/B.  My 8 circle works well but
> depending on the arrival angle of the signals the F/B varies.  I do not
> think the 8 circle has ever has 30+ DB of F/B.  I am using a ~3 foot 5/8"
> ground rod (8 foot rod cut into three pieces) for each antenna.  My array is
> out all by itself away from any metal objects on a small hill.
> 
> Lee's comment about it should have a 30+ DB F/B is interesting.  If
> grounding is the key I will go out tomorrow and add more ground rods/radials
> and give it a try to see if it will indeed improve F/B.  Comments?
> 
> My 8 circle works not bad on 80 meters either, directional too.
> 
> When I test my 8 circle/4 square and other receive antennas for F/B I try to
> do this during the middle of the day using ground wave from an AM broadcast
> station 100 miles away or so.  This was suggested by Jose N4IS when testing
> the Waller Flag I built.  When using an application called Polar plot and
> testing the WF I can easily see the pattern of the WF.  This might be a
> trick that can be used to check F/B on other receive antennas. 
> 
> I have attached a plot of the 8 circle when using Polar Plot.  Once I
> started Polar Plot I switched the 8 circle through its range.  You can read
> the F/B from an AM station some 80 miles away.
> 
> Comments?
>  
> Dave Anderson, K4SV
> Tryon, NC
>  828 777-5088
>  
> www.K4SV.net
>  
> 
> 
> 
> On Saturday, November 30, 2013 6:54 PM, kd9sv <kd9sv at comcast.net> wrote:
> 
> Lee, 30db F/B is about what I am seeing on my 4sq with 80ft/side which is
>> located about 400ft in the clear in an open field...de gary
>> 
>> -----Original Message-----
>> From: Hi-zreceivingarraydiscussions
>> [mailto:hi-zreceivingarraydiscussions-bounces at hizantennas.com] On 
>> Behalf Of Lee K7TJR
>> Sent: Saturday, November 30, 2013 5:56 PM
>> To: 'Hi-Z Receiving Array Discussions'
>> Subject: Re: [Hi-zreceivingarraydiscussions] DIRECTIVITIY 8 CIRCLE
>> 
>> This will be an interesting thread. The Hi-Z 8A was only designed to 
>> work on a single band, but to produce the best SNR currently available on
> that band.
>> I suspect your observations are what I would expect on other bands. If 
>> operating on multiple bands, I would suggest changing over to a 4-8Pro 
>> which is a 3 band array and shows reasonable directivity on all three. 
>> With of course, slightly less available SNR of received signals than 
>> the single band array.
>>    All that being said, I have heard that the 8A actually hears 
>> reasonably well on 80 Meters while not showing much directivity.
>> I personally have not seen the need for common mode protection however 
>> every install is usually different. If you are seeing 30+ dB of front 
>> to back ratio on 160 meters I suspect your ground rods are quite adequate.
>> 
>> What say others?
>> 
>> Lee  K7TJR
>> 
>> -----Original Message-----
>> From: Hi-zreceivingarraydiscussions
>> [mailto:hi-zreceivingarraydiscussions-bounces at hizantennas.com] On 
>> Behalf Of k4pi at bellsouth.net
>> Sent: Saturday, November 30, 2013 2:13 PM
>> To: hi-zreceivingarraydiscussions at hizantennas.com
>> Subject: [Hi-zreceivingarraydiscussions] DIRECTIVITIY 8 CIRCLE
>> 
>> I have an 8 circle in 200 ft diameter.  I notice the F/B and F/S are 
>> mainly only good on 160.  Even on the upper portion of the BC band for 
>> the most part the F/B is not great.  Not that I need this but I have 
>> used Hi Z 4 squares with 90 ft on a side and they seem to have good F/B 
>> on the BC band and other bands.  On 80 with the 8 circle I can tell the 
>> most predominant direction of a station but there is little F/B and 
>> F/S.  Just wondering if this is what others are seeing.  It receives fine.
>> 
>> I am well pleased with the system but just wondered what others were
> seeing.
>> I am using only a single 4 ft ground rod and wondered if anyone else 
>> had seen any improvement of the system with more ground rods.  Also 
>> wondered if anyone else was using common mode chokes in the feed line 
>> as recommended by ON4UN's Low Band DXing book.  I have one at the 
>> receiver end built from K9YC data.  My feedline is about 450 ft long 
>> being cable TV hardline.  It is grounded once in the middle.
>> 
>> Would like to hear from others on their experience.
>> 
>> 73 Mike K4PI
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