Build your own "twig"

[Archive-8]

I have made an aerial for the plain plotting.

Picked up some coax to make, now I have just had a thought.

If I buy 2m of decent radio coax, will this make a better twig?

Compared to regular sky/tv coax?

 

[Vipersan]

Difficult to say Chris ..
It is a fact that the collinear is easier to assemble with the steel centered copper coated core of RJ6 ..
There are other things to consider such as the velocity factor of the dielectric material of the coax...
What is certain is that if the coax is 50 ohms impedance ..you will have a closer match ...or at least that's what I read ...
I guess it is just a case of 'suck it n see'..
good luck mate ...
I'd be interested in seeing comparison results..

 

[PaulR]

For best results you should match the impedance of the cable to that expected by the box. Generally speaking transmitters use 50 ohm and dedicated receivers use 75 ohm. Matching the impedance of the cable to that of the antenna is then the problem.

 

[Archive-8]

So a twig and dongle used for rx only would use 75 ohm coax.

And match up with the impedance, at not cause any problems.

I am rather new to all of this.

 

[Analoguesat]

The main thing for the 1090 antennas is to get them up as high as possible and preferably outdoors. A couple of extra feet will easily compensate for any slight impedance mismatching.

 

[Archive4]

If I were you Chris, I´d go as high as I could.

 

[Archive-8]

Might be able to get it in the loft, and run the vrs in one of the other rooms.

Still tinkering with it all, so I like it under my nose.

Trouble with me is, now I have made the twig, my head starts thinking about improvements etc, what if this and what if that..... it goes on and on.

And I am still toying with the idea of a setup in Sherborne. But that will cost about £100 ish by the time I have my "perfect" setup.

 

[Terryl]

Just make a "J" pole antenna out of 1/2 inch copper pipe, you can make one up tuned to any frequency you need to.

Here is a good place to start.

http://www.hamuniverse.com/jpole.html

But for wide-band stuff I use a Discone from Diamond Antennas.

 

[Terryl]

For areas where they do not allow external radio antennas we use to use what was called a "Venttenna" it was a black piece of ABS 2 inch pipe with the antenna built inside it, you slipped it into the roof vent for your sink or toilet.

I don't think they make them anymore but you can build one up, if they ask why the vent is so high you just say that you were getting sewer gas back into the house and some plumber did the job.

What was inside was several 5/8 wave dipoles made out of wire and co-phased, all wrapped around a second sleeve that was slipped up into the 2 inch ABS pipe, I have one for 2 meters and 440 that was used at an apartment I stayed at for a bit, worked great.

 

[Archive-8]

For areas where they do not allow external radio antennas we use to use what was called a "Venttenna" it was a black piece of ABS 2 inch pipe with the antenna built inside it, you slipped it into the roof vent for your sink or toilet.

I don't think they make them anymore but you can build one up, if they ask why the vent is so high you just say that you were getting sewer gas back into the house and some plumber did the job.

What was inside was several 5/8 wave dipoles made out of wire and co-phased, I have one for 2 meters and 440 that was used at an apartment I stayed at for a bit, worked great.

That's quite a good idea, sometimes the best way of hiding something is right in plain sight.

 

[Terryl]

OOOhhh guess what I found...

http://www.ventenna.com/

 

[Terryl]

I have taken a Comet antennas 2 meter 44o dipole and stuck it up inside a fiberglass flag pole (they can't tell you that you can't have a flag pole in your yard here stateside) the local HOA didn't know and could not do anything about it, the coax was feed underground in conduit.

We have ways of hiding antennas.

 

[Archive4]

OOOhhh guess what I found...

http://www.ventenna.com/

If the forum Gods get a whiff of that?

 

[Archive-8]

Well I have only just made my first twig now at mk5, and hanging on the back of the tv at the moment.



I used basic 30p a meter coax, to try to start with but now I am asking questions and starting to experiment with different coax hence some of my questions..

 

[Archive-8]

If the forum Gods get a whiff of that?

It could create a bit of a stink

 

[Archive4]

Well I have only just made my first twig now at mk5, and hanging on the back of the tv at the moment.

View attachment 98295

I used basic 30p a meter coax, to try to start with but now I am asking questions and starting to experiment with different coax hence some of my questions..

A. Must be a big TV!
B. Worst place you could put it! Do you have any idea how much EMD is generated by TV´s etc?

Stick it elsewhere!

 

[Archive-8]

A. Must be a big TV!
B. Worst place you could put it! Do you have any idea how much EMD is generated by TV´s etc?

Stick it elsewhere!

Yes I know, once I have finished playing I will try and put it somewhere more permanent.

 

[Vipersan]

Indeed all that has been said is worth paying attention to ...though collinear is better than J pole for this specific job I think...
As high as possible above gutter preferably on the roof is all thats required ...unless like Confucian you have a super mast in an acre of open land going begging..
??

 

[Archive4]

Yes I know, once I have finished playing I will try and put it somewhere more permanent.

All replies welcome !
Come on!

 

[Archive-8]

Just found some RG213/U coax.

It has about 6 solid cores. 50 ohm.

Would this be any good?