ranger140
Freebander
Registered: 03-2010
Posts: 73
Karma: 1 (+1/-0)
|
Reply | Quote
|
|
di-pole into a 2 element beam
I have my hands on a sirio di-pole.
I was thinking of adding a pole to turn it into a 2 element beam for portable work,
however best to go for the director or the reflector??
I am also not sure if the boom supplied with the di-pole is long enough to seperate the two, I have had conflicting advice on distances between them, any thoughts please.
Thanks.
T
|
5/Oct/2011, 12:44 pm
|
Link to this post
Send Email to ranger140
Send PM to ranger140
|
yamanx1
Head Honcho
Registered: 09-2007
Location: In a world of my own
Posts: 4894
Karma: 40 (+41/-1)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
Best way is to have two driven elements, using 70ohm coax between the two elements, I have some plans for this, I’ll post them.
Or turn it into a three element, the spacings are quite close for the Sirio three element. But you will need a slightly longer boom and the ali pole is a difficult diameter to get hold of, although I have some here you can have
Either way you will need the small casting that comes with the Sirio for best results.
---
By all means think yourself big, but never think others small.... R.F.Scott
|
5/Oct/2011, 2:18 pm
|
Link to this post
Send Email to yamanx1
Send PM to yamanx1
|
Hot Fusion
Management
Registered: 03-2008
Location: South West England
Posts: 1389
Karma: 7 (+7/-0)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
I believe adding either a director or reflector have similar benefits, so the choice is up to you.
bear in mind that a reflector needs to be approx. 5% longer than the driven element, and a director needs to be about 5% shorter.
Also note that the feedpoint impedance will drop quite a bit meaning you will no longer get a good match to the coax and this may well cost you as many decibels as any you would gain from the modification.
My honest advice would be to get a purpose-built 3 element antenna - this will have the correct spacings and element lengths, and have a feedpoint matching section.
--- Andy - FB107
|
8/Oct/2011, 5:50 pm
|
Link to this post
Send Email to Hot Fusion
Send PM to Hot Fusion
|
mikefox whiskey
Accomplished DX-er
Registered: 02-2009
Location: Northern Ireland
Posts: 403
Karma: 1 (+1/-0)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
I was thinking of turning my Sirio SD27 dipole also into a two element beam, the boom is 4ft 7 inches or thereabouts, the British built Vortex two element beams have a similar length boom.
I was going to add a reflector behind the driven element, this would be good for front to back rejection, adding a director in front rather than a reflector would perhaps have more gain but less rejection from signals to the rear, it's all about experimentation with the spacing and a good antenna analyser would be handy.
I was contemplating actually adding a piece of boom and making a three element out of it, spacing's are widely different on commercially made beams and I guess I would have to play about, for instance the Maco M103 three element is 11ft long with 7ft between the reflector and driven with 4 ft between the driven and the director.
The 3 element sirio equivalent has an 8 or 9ft boom, with 4ft between the elements.
So plenty of scope for messing about with differing lengths.
--- (Forum user name is now SuperNasty)
|
1/Dec/2011, 8:03 pm
|
Link to this post
Send Email to mikefox whiskey
Send PM to mikefox whiskey
|
topbuzzuk
Big Cheese
Registered: 11-2007
Location: Wiltshire, UK
Posts: 2655
Karma: 12 (+12/-0)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
dave are you on about co-phasing the two di-poles? i'd like to se the plans for that, but i imagine its pretty simple just the spacing and length of the two bits of 70-75ohm coax??
--- 26FB118
|
2/Dec/2011, 7:21 pm
|
Link to this post
Send Email to topbuzzuk
Send PM to topbuzzuk
Yahoo
|
henry hpsd
New Kid On The Block
Registered: 02-2010
Posts: 6
Karma: 1 (+1/-0)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
Hello,
It is known that it is possible to construct a 2elements yagi with relative short spacing and actually getting that way maximum gain...
You can also make the antenna and tune it for maximum front to back.
A "study" on the www.cebik.com website will provide better information than i can tell.
HOWEVER...
And thats a big however.
That "maximum" is only over a relative short bandwidth.
Possibly the best way to go for the average CB user would be to go for a 2 elements moxon.
The moxon will have a not noticable slightly lower gain (in comparisment to a maximum gain 2elements yagi-uda antenna)
But it will remain rather high over a wider bandwidth which is a major bennefit as the CB band is rather wide.
Besides the 2el moxon has a direct 50 ohms impedance for that reason there are no matching losses (as small as that migth be)
We could do another thing.
I have designed a 3elements folded dipole yagi with a 6 feet boom.
That antenna has a antenna plot which never has been seen before on 11 meter
(for that boomlength).
And it is also 50 ohms so relative easy to feed.
If you are interested please mail me as im more than willing to help you.
(i wont put the link online as we sell them commercial aswell and i dont want to give the wrong impression)
By the way you do have another option:
You migthdo a google search on "jungle job" antenna. Im more than willing to desing that for you aswell.
It looks like a bow and arrow. Where the bow is the refelector. So..all you need is about 18 feet copper wire and some non-conducting wire for the attachment.
Hope it helped,
Kind regards,
Henry 19SD348
|
4/Dec/2011, 8:00 pm
|
Link to this post
Send Email to henry hpsd
Send PM to henry hpsd
|
ranger140
Freebander
Registered: 03-2010
Posts: 73
Karma: 1 (+1/-0)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
sorry haven;t been around alot,
Thanks for your your replys.
I am waiting for some better 'summer' weather to get back out portable.
I am not really the 'aerial type' but i would like to give this a go very soon.
t
|
28/Dec/2011, 7:29 pm
|
Link to this post
Send Email to ranger140
Send PM to ranger140
|
sydthecat
Freebander
Registered: 02-2012
Posts: 21
Karma: 0 (+0/-0)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
hi all
I had a two element yagi made for me by a friend of a freind and i must say it really does work well
Cheers Craig
|
22/Jun/2012, 2:42 pm
|
Link to this post
Send Email to sydthecat
Send PM to sydthecat
Blog
|
Kaosss
Management
Registered: 04-2008
Location: County of Flintshire, N. Wales
Posts: 1890
Karma: 10 (+10/-0)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
Yes indeed, I can vouch for that, it does work very well. Nice one Craig
Al
--- Al -163FB777 - N.Wales, UK
Kenwood TS-480SAT, TS590, MC-90, Yaesu FT1000D, FT2000D,RCI 2995dx, Heil 781, 5 eli beam, F/S G5RV, K40 when mobile, A99 for portable. Optima V3,Portapack. RM KL500-modded, PMR`s.Ranger 1k Amp
|
22/Jun/2012, 6:27 pm
|
Link to this post
Send Email to Kaosss
Send PM to Kaosss
Blog
|
SuperNasty
Freebander
Registered: 01-2012
Location: NI
Posts: 59
Karma: 0 (+0/-0)
|
Reply | Quote
|
|
Re: di-pole into a 2 element beam
Looks good that 2 element with the hairpin match, I have since bought a 2 element Moxon from Henry at HPSD antennas and am very pleased with it, extremely high front to back ratio for rejection and enough gain to get good reports, easy to put together and light weight though heavy duty. Henry does not want to plug his commercial business on the forum but as a buyer I can recommend him 100%.
http://www.hpsd.nl/
--- (Forum user name was previously - mikefox whiskey) - 68 FB750 - Pat
Kenwood TS870 - Centre fed balanced dipole - HPSD 2 element Moxon for 11m, vertical 'Ringo' for 11m.
|
22/Jun/2012, 9:10 pm
|
Link to this post
Send Email to SuperNasty
Send PM to SuperNasty
Blog
|