"amdx" wrote in message
...
I'd like to build the antenna from the following page;

http://www.frars.org.uk/cgi-bin/rend...62&goback=1064

But there are a few details I need to sort out before I try.



1) It uses UT141, Could I sub 9913?

2) Or, should I use the copper tube method shown here,

http://martybugs.net/wireless/biquad/

3) The author states:

"Next, cut four pieces of UT141 coax 80mm long, and strip 1.5mm of
outer from each end, leaving a total outside length of 77mm. These will
form part of the phasing assembly. Follow the diagram as to the connection
of these pieces of coax. Connection of two double quads in parallel will
result in an impedance of 25 ohms."



Please view 4double quad back jpg at bottom of page as reference.



I assume he's describing the 77mm pieces that run at a 45* angles, however
the picture does not show

UT141 coax as he describes.



4) Again the author states:

" Next for the 25ohm to 100 ohm matching sections, cut two pieces of 61mm
UT141, again strip the outer back 1.5mm from each end to leave a outside
length of 58mm. Of course 2 100 ohm coax's in parallel will result in an
impedance of 50 ohms. Connect each piece to the joined 77mm lengths as per
the diagram. Under the connector, both centre conductors from the 58mm
lengths are connected to the centre pin of the SMA socket. Solder the
outer of these lengths to the SMA socket body to ensure a good earth
connection."



Again he says use UT141 but I don't see it in the picture.



I'm looking forward to your input!

Thanks, Mike

Hi Mike

You have given some great reference sites. Thanks.
If *I* was intending to feed two 25 ohm loads to a 50 ohm line, I'd
consider a series connection rather than transforming with a balanced line
transformer.
Besides, I didnt follow how the transforming of 25 ohms on a 100 ohm line
produced an impedance that is appropriate for matching to 50 ohms. But, I
havent studied the electrical equivalent lengths of the coax lengths.

Jerry