Quadrifilar Heliciodal Antenna question.

[dchurch24]

Hi all,

I'm pretty new to this game; I've had a few projects over the years - mainly based on computers controlling servos etc...(made an automatic cat-flap once with motion detection - sad, I know).

However, I am in the process of making a quadrifilar helicoidal antenna and have found a few designs on the good old Interweb, but out of the designs I have found where they make the antenna from coax cable, they use four lengths of cable and solder them together at the top and bottom.

My question is, does this matter? Can I just use one long length of coax to save the soldering?

Here is what I am making:

http://www.cidb.co.uk/pics/helicoid.jpg

...as you can see, it would be possible to feed one long length of coax through from the bottom, up around etc... and back down to the bottom to the connector and still keep the helicoidal shape.

One other thing is, I believe that the coax in the UK is 70 ohms - I'm not sure what the receiver that this is going to be plugged into is. Would I need to convert it (by maybe soldering to a heavier ohm coax cable) to the same before attaching to the unit?

The unit that this is going into is an Icom PCR1000 (in case that means anything to anyone!).

All help gratefully recevied - I really am a complete electronics beginner.

[dchurch24]

Well, I've not wired it with one length of coax, I have found a diagram and wired it correctly - phew.

However, I'm still a little confused by the impedence question - can I just plug the coax into the back of the receiver and hope for the best or is there something else I need to do to regulate power before it reaches the unit?