Antiference 'Antex' X aerial

[EF80TVVALVE]

Hi all

I've recently found the main nount/body of this type of aerial when walking across a field that was once used to for construction waste. It was in poor condition but complete with the semi circle brackets used to help clamp down the elements. I also have one in much better condition that a forum member gave to me many years ago and now I have enough parts to make a complete aerial without risk of damaging from winds etc.

I'm just wondering if anybody has any information for the lengths of the elements used on the antex, preferably for Channel 4 as this is the channel that covered my region. I'm hoping to buy some new aluminium tubing and make it to the correct size. From memory the reflector and director elements are connected together in the body of the aerial.

[Andy Green]

Who may be able to advise on what elements were connected to what is Wrights aerials differed for the 'X" aerials depending on who made them)
You could then model it in EZNEC to get the element lengths - the demo version should do you.

[peter_scott]

I have a little Bernards book on making your own aerials. For a X aerial on Channel 4 it quotes the Director as 3' 7½" and the Dipole 4' 0"

Peter

[EF80TVVALVE]

Thanks for the advice both, it may be worth me having a play with the EZNEC software, it looks interesting and may be of great help.

Peter - am I correct in thinking that this would be more like a H with angled elements? There were some like this available at the same time as the Antex although I believe the Antex is two directors at the front, dipole at the top rear and reflector at the bottom.

I see the science museum has an early one for Channel 5 but I highly doubt they will be willing to measure the elements or even give access to it to be inspected in person.

[Nuvistor]

The rear two elements are the dipole, front elements are directors, there are no reflectors with the Antex.

[peter_scott]

The X in the Bernards book was a genuine 90 degree cross with the two directors at 10-30 and 7-30 and the two dipole elements at 1-30 and 4-30 if you get my meaning.

Peter

[EF80TVVALVE]

Thanks for clearing that up Frank, I must have been confused from recalling a previous discussion on why the lower dipole was connected to the directors.

Peter - thanks for the information, I suppose these measurements will be fine for the Antex, after all it's not going to be receiving Ch4 405 any time in the future, is it!

[Restoration73]

There is more to this antenna design ;

http://on5au.be/content/a10/vhf/6mrp.html

[kan_turk]

The two shorter segments together form a single director which is at ground potential - the two longer segments form a single dipole (lower segment grounded connected to coax screen while upper segment is the signal connection which is connected to coax inner)

J

[SteveCG]

Antex 'X'

For Channel B4: Director 3', 10 3/4"; Dipole 4', 2 3/4" (These are tip to centre of junction box lengths)
For Channel B2: Director 4', 7 1/2" ; Dipole 5', 3/4" ( ditto )

Note that the mounting holes are at different distances from the centre of the junction box.

[simpsons]

I bet that they'll be fun and games at the local Currys (PC World) when you get your NEW X aerial on the roof.

In ignorance, as a boy, I always thought that the X with its Band 111 attached was "space age" unlike its H brother.

So, with that in mind, will joe public think: Ahh Is this the "BritBox" aerial? and rush down to said retailer demanding that they have one too!!

Just one question though, just what are you expecting to receive on CH4, or do you know something about 405 Alive you could share.

Chris

[EF80TVVALVE]

Thanks Steve, it looks as though sizes between the different X designs didn't differ too much then. I'm interested to know where you got the information from as I've been searching for quite a while, unless you are in possession of some complete examples which would easily give away their secrets.

Chris, I'm sure with it on the roof it would create a bit of interest, I'm sure they are mostly forgotten by those who seen them many years ago and anyone younger wouldn't have a clue. I'm unsure whether I'll put one on the roof as of yet. My reason for rebuilding one is simply for my own interests, I've always wanted to get my hands on one and keep an eye on a few local examples in case I catch them being removed (already missed a couple) but I've been lucky to get hold of the centre mounts which is probably as close as I'll get.

I don't have any information on the 405 test transmissions but I'd be way out of the coverage area and I think I'd need something more substantial than this X to receive anything. We shall see what comes of it though as I'd love to try when the time comes.

[SteveCG]

EF80TVVALVE,

The dimensions came from complete examples. Note that on a combined X and Band III the same Band I junction box was used, just rotated through 90 deg. This however meant that the positions along the elements of the mounting holes of the elements were therefore in a rotated sequence as well.

[EF80TVVALVE]

Hi Steve, it's great that there are others out there recording or have access to this type of stuff, I'm sure Antiference probably never put dimensions etc on paper, at least not available to the general public. Do you happen to have any photos of the mount for the junction box to mast? This is the only thing I've never seen complete and something I need to make from scratch.

[SteveCG]

EF80TVVALVE,

Hmm, mountings... Well off memory (I took the data over 30 years ago) Antiference had different mounts depending on whether it was a single X or a combined Band I & III. I cannot recollect exact details but they used one metal plate on either side - making the junction box the filling in the middle of the sandwich. In other words they supported the moulding both sides to minimise snapping off stresses. How the plates were then linked to the mounting pole I can't remember. Perhaps you could use spacers to keep the plates at the desired separation and then drill through the metal plates to use a 'U' or 'V' bolt to attach to a 1" pole?

[EF80TVVALVE]

That sounds like it will be easy enough to do, there were some bits remaining on the field find one but not enough to know how exactly it attached to the mast. I'll make something up this weekend I'm sure, it seems relatively simple.