It is currently Thu Sep 19, 2019 4:32 am

Click the link below to visit the site sponsor

The Ham Radio Shop




Post new topic Reply to topic  [ 15 posts ] 
 hexbeam 40m band only 
Advanced Member
User avatar

Joined: Wed Mar 25, 2009 10:55 pm
Posts: 222
Location: Falkirk
Feedback: 26 (100%)
Reply with quote
Post hexbeam 40m band only
Steve, looking for advise basically getting new beam antenna and wondering if I can use hexbeam spreaders to install a 40m band rotatable dipole or will it be to small

Any advise appreciated

Cheers

Steve


Tue Nov 18, 2014 6:11 am
Profile Send private message

 hexbeam 40m band only 
Contributor 2018
User avatar

Joined: Sun May 24, 2009 10:46 am
Posts: 509
Location: Watford, Hertfordshire - IO91tq
Feedback: 17 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Not sure if this may be of interest, but you could add 40m to your Hex.

http://www.jdunman.com/ww/AmateurRadio/Antennas/hex.pdf

Anthony

_________________
Drowned Rats Radio Group - M0HRF


Tue Nov 18, 2014 7:37 am
Profile Send private message

 hexbeam 40m band only 
Advanced Member
User avatar

Joined: Wed Mar 25, 2009 10:55 pm
Posts: 222
Location: Falkirk
Feedback: 26 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Thanks for reply tony but getting steppir db11 and just looking to see if I could use the existing hex spreaders for a single band 40m rotatable dipole

I have tried what you said a few years back but went back to basic wire dipole ran down garden


Cheers

Steve


Tue Nov 18, 2014 4:12 pm
Profile Send private message

 hexbeam 40m band only 
Moderator

Joined: Fri May 22, 2009 1:23 pm
Posts: 5662
Location: Northampton IO92ME
Feedback: 1 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Making a hexbeam even smaller by inductively loading the elements is, in my view, just not worth the effort.

A rotatable dipole is a better idea, but what maximum length would you be able to manage from your spreaders?

I realise it's probably longer than you're considering, but this idea from Cecil is worth a look:
http://www.w5dxp.com/rotdip.htm

Finally, Ant has added a "bent" 40m dipole to the normal hexbeam structure; you could try building that simply for 40m with 4 spreaders:
http://www.g3txq-hexbeam.com/index.php/ ... nd-hexbeam


Steve G3TXQ


Tue Nov 18, 2014 4:20 pm
Profile Send private message WWW

 hexbeam 40m band only 
Advanced Member
User avatar

Joined: Wed Mar 25, 2009 10:55 pm
Posts: 222
Location: Falkirk
Feedback: 26 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Steve I got the hexbeam from dx engineering and had the five bands the turning radius is 3.2 metres was just not sure if a full dipole would fit on it.looked at ants 40m twin peak but not sure how it works as each leg looks different length.Thanks for the reply

Regards

Steve


Tue Nov 18, 2014 5:36 pm
Profile Send private message

 hexbeam 40m band only 
Moderator

Joined: Fri May 22, 2009 1:23 pm
Posts: 5662
Location: Northampton IO92ME
Feedback: 1 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Ant's design is a 40m half-wave of wire, fed at the centre, and stretched between two "opposing" spreaders; the surplus wire at each end is then taken to an adjacent spreader, and then finally back towards the centre-post. You could easily build one without a normal centre-post because you only need to keep the wire just clear of the spreaders.

You end up with a 40m half-wave with a maximum dimension just a little over the diameter of a 5-band hexbeam. Bending the dipole like this lowers its feedpoint impedance so you need a 1:4 balun at the feedpoint - very similar to the bent dipoles in a cobweb.

Steve G3TXQ


Tue Nov 18, 2014 6:22 pm
Profile Send private message WWW

 hexbeam 40m band only 
Advanced Member
User avatar

Joined: Wed Mar 25, 2009 10:55 pm
Posts: 222
Location: Falkirk
Feedback: 26 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Thanks for that Steve I have the 1:4 balun which takes it to 12.5 ohms so will give it a go over Christmas period when on holiday

Thanks again


Steve


Tue Nov 18, 2014 6:33 pm
Profile Send private message

 hexbeam 40m band only 
Advanced Member

Joined: Sun Jan 27, 2013 3:37 pm
Posts: 430
Location: Cumbria, Gods Country
Feedback: 7 (100%)
Reply with quote
Post Re: hexbeam 40m band only
G3TXQ wrote:
Finally, Ant has added a "bent" 40m dipole to the normal hexbeam structure; you could try building that simply for 40m with 4 spreaders:
http://www.g3txq-hexbeam.com/index.php/ ... nd-hexbeam

Steve G3TXQ


Link returns 404 error Steve, presumably t has moved... somewhere?


Sun Dec 28, 2014 11:26 am
Profile Send private message

 hexbeam 40m band only 
Moderator

Joined: Fri May 22, 2009 1:23 pm
Posts: 5662
Location: Northampton IO92ME
Feedback: 1 (100%)
Reply with quote
Post Re: hexbeam 40m band only
It looks like Ant has re-worked his web site!

If you need some dimensions I can probably come up with some.

Steve G3TXQ


Sun Dec 28, 2014 1:05 pm
Profile Send private message WWW

 hexbeam 40m band only 
Advanced Member
User avatar

Joined: Wed Mar 25, 2009 10:55 pm
Posts: 222
Location: Falkirk
Feedback: 26 (100%)
Reply with quote
Post Re: hexbeam 40m band only
If you dont mind Steve that would be great much appreciated

Cheers


Steve


Sun Dec 28, 2014 10:10 pm
Profile Send private message

 hexbeam 40m band only 
Moderator

Joined: Fri May 22, 2009 1:23 pm
Posts: 5662
Location: Northampton IO92ME
Feedback: 1 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Hope you can remember the shape - if not I'll draw it out.

Wire 1 that runs from side to side, through the centre of the hex support structure: 26ft
Wires 2 & 3 that run from the ends of wire 1 to the tip of each the adjacent spreader: 13ft
Wires 4 & 5 that run from the ends of Wires 2 & 3 back towards the centre post: 10.2ft

Feedpoint is in the centre of wire 1 and needs a 1:4 balun.

Total length of wire: 72.4ft

The model shows resonance at 7.1MHz using bare copper wire; you'll need to reduce the dimensions by about 3% of you use insulated wire.

Steve G3TXQ


Mon Dec 29, 2014 3:07 pm
Profile Send private message WWW

 hexbeam 40m band only 
Advanced Member
User avatar

Joined: Wed Mar 25, 2009 10:55 pm
Posts: 222
Location: Falkirk
Feedback: 26 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Steve thanks for info but as you say you are only using the four spreaders and with your version spreaders are only 3,2m radius means you cant do this unless they are made longer.Question is although not sure if this upsets pattern cant you go from centre in normal hexbeam pattern from V point and come back to centre on both legs like a butterfly from rear side of V keeping the elements to outside of the spreaders all the way round to rear using all six spreaders which would mean it can fit on normal hexbeam arrangement, Basically mirror image both legs please advise hopefully you understand what Im saying.


cheers



steve


Mon Dec 29, 2014 11:42 pm
Profile Send private message

 hexbeam 40m band only 
Moderator

Joined: Fri May 22, 2009 1:23 pm
Posts: 5662
Location: Northampton IO92ME
Feedback: 1 (100%)
Reply with quote
Post Re: hexbeam 40m band only
You're right that the way Ant implemented it, the spreaders had to be longer. The reason for doing it that way was that it keeps the critical mid-dipole section as straight as possible and allowed him to add it above a 6 band array.

I quickly modelled an alternative which ought to fit on 6 existing size spreaders - I assumed 10ft horizontal distance from the centre-post to the spreader tip. The wire runs from the feedpoint on the CP, out to the tip of a spreader as normal, then follows the spreader tips around the perimeter until it is opposite the feedpoint. The other side of the dipole does the mirror image of course. I assumed an insulator spacing gap of 1ft between the two ends where they come together - just as you would have in the cobweb.

Total wire length was 34.5ft each side of the feedpoint. With insulated wire it would be correspondingly smaller.

The penalty of bending the centre section - as distinct from Ant's straight section - is a further drop in radiation resistance to about 10 Ohms and a further narrowing of the SWR bandwidth. But it might be an acceptable compromise for you.

Hope that helps,
Steve G3TXQ


Tue Dec 30, 2014 9:28 am
Profile Send private message WWW

 hexbeam 40m band only 
Advanced Member
User avatar

Joined: Wed Mar 25, 2009 10:55 pm
Posts: 222
Location: Falkirk
Feedback: 26 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Steve thanks for the reply next question could i add the 30m dimension to it to have both bands as both rotatable 30/40m dipoles


cheers


steve


Fri Jan 02, 2015 11:42 pm
Profile Send private message

 hexbeam 40m band only 
Moderator

Joined: Fri May 22, 2009 1:23 pm
Posts: 5662
Location: Northampton IO92ME
Feedback: 1 (100%)
Reply with quote
Post Re: hexbeam 40m band only
Yes - if you extend the spreaders you could add a 30m version.

Just a couple of points:

1) The feedpoint impedance is low at around 10 Ohms so you either need two separate 1:4 baluns and feedlines, or if you use a common balun (like in the cobweb) there should not be a large distance between the two feedpoints.

2) When you bend a dipole this way, the azimuth radiation pattern tends to become close to omnidirectional; it's debatable whether it's worth making it rotatable.

Steve G3TXQ


Sat Jan 03, 2015 9:01 am
Profile Send private message WWW
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 15 posts ] 


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB © phpBB Group.
Designed by Vjacheslav Trushkin for Free Forums/DivisionCore.