Top Band Homebrew Wire

[vitvoo1]

I'm looking to pick the Brains of some of you more experienced guys or anyone come to that in the know.

I'm looking to build an effective Antenna for top band and have been toying with the idea of building this..saying that I'll go ahead and do it anyway...... it's all part of the fun. :-)

My only concern is the 70ft wrapped around the Fibreglass Tubing..would this cause any problems...I intend to use Plastic tubing instead of the Fibreglass.

Anyway...what do you think?


http://www.iw5edi.com/ham-radio/?a-practical-antenna-for-160-metres,32


Any input would be greatly appreciated.

Happy New Year again to you all!!

[Advent]

Hello and a Happy New Year to you...
This topic has been brought up quite recently on this site do a search under Multi Band long wire....

Then go and have a peep at :-

http://uk.groups.yahoo.com/group/topbandhelical/yguid=235835346

for further info on the type of antenna your about to build.
Good Luck
73
Keith......





nnnn

[steveeh131047]

Good luck with the build.

EZNEC modelling shows that it does indeed have a useful mixture of low-angle radiation and higher angle. Antenna and coil copper-losses, assuming #14 gauge wire, are about 2dB - mostly in the coil. As expected the feedpoint impedance is low - about 4.7 Ohms, so you need a good ground system.

A low VSWR will be a strong indicator that you have high ground losses. For example, if you measure 2:1 or better, that indicates the feedpoint impedance is 25 Ohms or higher, and that indicates that your ground losses are 20 Ohms or more. That's an efficiency of 20%.

So the usual "odd" advice applies: keep putting more copper into the ground until the VSWR is as bad as you can get it :)

With zero ground losses the antenna has a 2:1 VSWR bandwidth (ref 4.7 Ohms) of 18KHz; so, again, wide bandwidth will be a good indicator that you have high ground losses.

73,
Steve G3TXQ

[M3WHN]

You could try this http://www.pi4cc.nl/link/mkII.htm Depends though on space if it ends up being larger than the back garden.

[steveeh131047]

Originally posted by M3WHN
You could try this http://www.pi4cc.nl/link/mkII.htm Depends though on space if it ends up being larger than the back garden.

That design has a much higher feedpoint impedance - 12 Ohms - so the efficiency will be a lot higher. But note that, as shown in the first diagram, it needs about 60ft of vertical height.

Steve G3TXQ

[vitvoo1]

Happy New Year to you also Keith!

Thanks for the input Gent's, I'll also have a look at the link that you and M3WHN has posted.

Excuse my ignorance but you all have been very helpful.

I have been advised to get more Copper in the ground, at the moment I only have one stake in the groung about 3ft down which I am guessing could be better, I am lucky though I have a very wet ground being only 150m from the sea on sea level and I keep it well watered ;)

I'll get to work on the Ground system before I go any further and when it stops raining here.

I'm itching to give top band a go so I'm looking forward to having a mess around in the Garden with Antenna systems, unfortunately I don't have the biggest Garden in the world also have Power lines :( going over my House so I'm hoping this system will be ideal for me.

Happy New Year to you all! and thanks again.

[steveeh131047]

If I lived 150m from the sea I think I'd work 160m portable on the beach with a kite-supported quarter-wave vertical :)

Have a healthy & peaceful 2009,
Steve G3TXQ

[vitvoo1]

Originally posted by steveeh131047
If I lived 150m from the sea I think I'd work 160m portable on the beach with a kite-supported quarter-wave vertical :)

Have a healthy & peaceful 2009,
Steve G3TXQ

Yer getting technical now Steve. :)

Thats way down the line for me mate, my heads getting a wee bit scrambled (which wouldn't take much) with the links I've just looked at, a lot to take in indeed.

All the best also for 2009!

[M3WHN]

Another option is to go for a DX loop. It is smaller than a full vertical. It would solve problems of vertical and horizontal and as you are so close to the sea, placing it outside with 18" off the floor it may work a treat.

Try this one:

http://members.verizon.net/~vze24qhw/loop.html

[vitvoo1]

Thanks for the link M3WHN!

I'd need a little help with that one I think, not the actual Antenna construction but the tuning box, it does look like an ideal Antenna for my needs and no height at all as you say.

You guys have give me a lot to think about.

Thats why I love this Hobby and i'm only new into it but I admit........I do have an awful lot to learn!

73

[M3WHN]

All you have to do is to ask at your radio club for help. Get someone who can make the box for the base and price up how much it costs. As a foundation licence holder it can count towards your intermediate as soldering and construction is part of the 2E0. So having someone help you and learning to solder and construct will have that box ticked when it comes to the exam.:D

[steveeh131047]

That particular magnetic loop design would make a fine Rx antenna, but is likely to be very inefficient on Transmit.

Magnetic loops designed for efficiency will most likely be single-turn and comprise large diameter copper or aluminium tube, not wire. Even then it's a struggle to get one of a reasonable size that operates efficiently on 160m.

Here's a site that will give you some idea of the engineering involved:
http://www.standpipe.com/w2bri/


73,
Steve G3TXQ

[M0VEY]

..

[M3WHN]

Originally posted by M0VEY
Try my Topband helical site. a few ideas on here.

Topband Homebrew Helical (http://uk.groups.yahoo.com/group/topband-helical/)

Other Ideas here: M0VEY HOMEBREW ON FLICKR (http://www.flickr.com/photos/13508717@N04/)

Cheers,

Seen that group some time ago. The image on the front, the one made from plastic tubing seems interesting.

So applied to join (membership pending).

[vitvoo1]

Even more food for thought there.

I'll let my Tutor's have a look at the design and see what they say.

I'm intending in sitting the Intermediate in the Summer hopefully, just starting to study for it now but I don't want to learn to run before I can walk.

It will as you say M3WHN be a tick for one of the practical tests which would be killing two birds with one stone.

Thanks for the additional links Gents, I'll have a look when I'm fully awake.

[G0GQK]

I made one of these when it first appeared in QST magazine many years ago now. I was unable to get it to the height required but nevertheless it was very good at receiving and it was too complicated for me to use permanently because of trees and other things so I took it down. I used white plastic tubing and had no problems with it.

'Tis a fact that 160 metres is a problem band for many people and its noisy as well, but OK for local contacts.

G0GQK

[vitvoo1]

Thanks for letting me know about your experience with this Antenna.

You mention height required, out of curiousty what would you determine as being a required height, would it be a case of the higher the better I imagine?

Top band is a big problem for us not so fortunate with a good sized Garden so I see this as ideal for me.

I will let you all know how I get on, as said in previous post I'm going to work on my Ground system first.

Cheers