[UK-CONTEST] Monobanders and height

[Andy Cook, G4PIQ]

Callum,

I think you'll find some take-off angle data in the ARRL Antenna Handbook
(don't have a copy myself), but what you'll see from there is that it's all
statistical, so it's about the likelyhood of a particular angle on a
particular path at a particular time of year. I know from experience this
differs with time, and also with day (which is presumably linked to what
hop-mode-mix is dominant on a particular day on a particular path). To a
large extent, low angles are dominant at the start and end of openings.

On a practical note, I've have opertated a number of times with antennas at
55ft / 95ft mix both available. In general on shorter paths (Eu / East Coast
W) there's not so much to choose between them, but the difference is more
pronounced on the longer paths and early / late in openings and marginal
forward-scatter paths. It's not often that the lower antenna is better than
the higher one, but from time to time (I've seen it on Eu paths on 20m in
the summer, intense W openings on 15, and on a similar basis I have
occasionally seen a dipole @ 80ft better than the 4 square on 80m to the
East Coast of W during strong openings). If I could have only one antenna it
would clearly be the one at 100ft, but if I was doing a field-day contest
with the majority of traffic to Eu, I wouldn't worry too much if I only had
the 60ft one available.

73,

Andy, G4PIQ

-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com] On Behalf Of Callum MØMCX
Sent: 02 May 2010 17:18
To: uk-contest at contesting.com
Subject: Re: [UK-CONTEST] Monobanders and height


In CQWPX, we ran a pair of A3S antennas; 100 feet and 50 feet. The 100  
footer won everytime; both EU and DX.

Although we'll have a 60 footer available for FD, we won't have time  
and resources to do both towers.

We have all our antennas modelled but there appears to be a knowledge  
gap as regards take off angles. I can't find a reliable source of  
information outlining the variables that affect required take-off  
angle for required range on a per frequency basis.

A case in point is 80m. I now have real-world data for a dipole at 140  
feet; the answer is that it will only run DX, (but it's great). The  
footprint only starts to land at around 2,000 miles. For 20m, I've no  
real world data unfortunately.

If I can get some reliable data tables together, that would assist the  
decision making processes.

Callum McCormick
Via iPhone
07976 631881
http://www.m0mcx.co.uk/
http://www.barclayanderson.com/

On 2 May 2010, at 16:42, "Clive GM3POI" <gm3poi2 at btinternet.com> wrote:

> Callum,
>    With all the work involved in doing either
> project you would be well advised to model the
> difference using the ARRL handbook software by Dean
> Straw (HFTA).
>    You should input the main directions from the
> location of the proposed antenna and use say a 2el
> 20m to represent the A3S and a 3el mono at the
> various heights. Dependant on the local ground slope
> you may get some surprising results.
>    The only time surprises don't happen is when you
> have flat ground around the Station, because you need
> roughly twice the antenna height over  gentle sloping
> ground. 73 Clive GM3POI
> ----- Original Message -----
> From: "Callum MØMCX" <callum at mccormick.uk.com>
> To: <uk-contest at contesting.com>
> Cc: "James Thresher" <James.Thresher at Jaama.co.uk>;
> "G4MKP" <terryburbidge at blueyonder.co.uk>
> Sent: Sunday, May 02, 2010 12:07 PM
> Subject: [UK-CONTEST] Monobanders and height
>
>
>> Our team is trying to establish the likely
>> real-world difference on
>> 20m band, in extreme field-day style contesting,
>> between an A3S at 60
>> feet and a full-sized 3 element  monobander with 16
>> foot boom at 100
>> feet.
>>
>> Does anyone have experience of these variables?
>>
>> Callum McCormick
>> Via iPhone
>> 07976 631881
>> http://www.m0mcx.co.uk/
>> http://www.barclayanderson.com/
>> _______________________________________________
>> UK-Contest mailing list
>> UK-Contest at contesting.com
>> http://lists.contesting.com/mailman/listinfo/uk-contest
>
>
> _______________________________________________
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