Hi Don
Yes, but I found this now about LPDA, but really wonder if it is possible to
do it as INV-VEE formation.
Because all I have seen have been straight, first antenna I saw with wire
was this army antenna.
I will do some research
73s Rag LA6FJA
****************************
http://www.supernec.com/lpda.htm
Geometry of an LPDA
The relationship between element spacing and element length are given by the
scale factor tau, as shown in equation 1.
tau = Ln+1/ Ln = dn+1/ dn
..................................................1
Truncating coefficents are used to find the minimum value for L1 (longest
dipole element) and the maximum value for LN (shortest dipole element) as
shown in equations 2 and 3.
L1 = 0.5 lambda max
.........................................................................2
LN = 0.25 lambda min
......................................................................3
Tau can be calculated using the following equation, if the length and
spacing of individual elements is required.
tau = (LN /
L1)1/(N-1)............................................................4
The Form Factor (FF) is defined as:
Form Factor = Boom Length / lambda max ................................5
-----Opprinnelig melding-----
Fra: n8de@thepoint.net [mailto:n8de@thepoint.net]
Sendt: 16. desember 2008 18:51
Til: LA6FJA/K3RAG Stein Roar Brobakken
Kopi: towertalk@contesting.com
Emne: Re: [TowerTalk] Wire log periodic antenna
Rag,
The spacing between adjacent elements in a LPDA is NOT a function of
highest/lowest frequency.
Do some research on LPDA design and you will discover that the
'graduation' of spacing and element lengths is dependent on CHOICE of
'sigma', the factor which determines bandwidth and boom length.
When Dr. Duhamel of Collins Radio 'discovered' Log Periodics waaaaay
back, his design information was published in a few texts, but most of
it goes too far for ham radio uses.
K4EWG {I believe] designed and built a nice LPDA that was printed in
the ARRL Antenna Handbook and one edition of the Antenna Compendium.
A little searching should prove fruitful.
Good luck.
Don
N8DE
Quoting LA6FJA/K3RAG Stein Roar Brobakken <s-roabr@online.no>:
> With correct picture link !!
> Hi
>
> I am planning to put a wire yagi for 40m to NA, but suddenly I came over a
> picture for a wire log periodic antenna.
>
>
> I have seen some pictures of wire log periodic antennas on internet,
> Just like this one
>
http://www.antenna.it/military/images%20military/disegno%20lp1530-w%20copy.j
> pg
>
> One guy have made one like this
> http://www.radiosky.com/super_cheap_log_periodic_antenna.html
>
>
> He have used spacing between 40 cm - 75 cm(2'5.8" - 1'3.8") for 17mhz -30
> Mhz.
>
>
> My spacing calculation gives:
>
> 40 cm is 1/35 wave on 17 Mhz, for first driver * is this optimal
calculation
> ?
>
> 75 cm is 1/40 wave on 30 Mhz,? for Rear Reflector * is this optimal
> calculation
>
>
> so my question is then have anyone tried something like this version
before?
>
>
> My idea is to make one for 7 to 21 Mhz ?
>
> should I just put my first driven element on 6 Mhz and then calculate
until
> 21.5 Mhz for reflector?
>
>
> I don't know what will happen when I get up one as Inverted-Vee in a Log
> periodic formation ?
>
> Anyone have a idea to figure the length of elements etc? correct spacing ?
>
>
>
> 73s Rag LA6FJA
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com
> Version: 8.0.176 / Virus Database: 270.9.18/1849 - Release Date:
15.12.2008
> 17:04
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
No virus found in this incoming message.
Checked by AVG - http://www.avg.com
Version: 8.0.176 / Virus Database: 270.9.18/1849 - Release Date: 15.12.2008
17:04
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|