17 Jul 2011

Afternoon Assembly

This afternoon I found myself in the Garage/workshop tidying up and had one of those moments when I looked into my “Radio” junk box and found the components required to make up a “Balun” project that I had been planning during last year but never started ! just recently I had been looking at erecting a different antenna – I had looked at the “Doublet” for a start, but last week I found an old article in the “UK Practical Wireless” on the old G5RV !! so I was thinking along those lines – either way a 1:1 Balun  (Choke) would come in handy so the half finished one I had in my box was pulled out – It is of the “Ugly” type made up of 18-21 feet of RG58 which was wound on UPVC pipe – how much ? I was’nt sure so stripped it all of to check,  (it was 21’) so I re-wound it and started from scratch – I had to poke around the workshop to find the other bits to start but after a couple of hours came up with this design (There are plenty of these around I’m sure)
balun_Choke
It consists of about a foot of upvc piping 1.75”, Dia app’x ,  with end caps drilled to take  two post type terminals, and one SO239 chassis socket, and 18-21’ of RG58 50 ohm coaxial cable (RG213  was a bit too heavy for this) but might make another (Big Boy)  later on 5” pipe.
The terminals are soldered up and end caps sealed (Glued) up and the whole thing covered in Black electricians tape – I could say this is my prototype – I have not tested it yet – I had difficulty in getting the ends on as the RG58 would not push down enough into the tubing and so there was a risk of shorting the terminals but this seems to be ok.
This will be placed “Immediately Outside the shack” to take the 450 ohm ladder line from my doublet/5RV with a length of about 10 feet of coaxial into the Tuner/Rig – the preferred method would be to feed direct to a balanced ATU but would mean having to hack the wall again so it’s easier to gain shack entry with the existing aperture.
So that was my Sunday Radio Job - the Doublet/RV will have to wait a bit now.

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