Cutting the coax cables

I use Conrad's PA5Y method of cutting my phasing cables to as close as possible to the desired length ready for final 'tuning' with a VNA. It saves time and I keep the conduit just incase I need to make another cable in the future. So to quote Conrad (from Moon-net 10/6/2021) :

On 10/6/2021 1:20 PM, Conrad PA5Y via Moon-net wrote:

The relative phase of the 2 cables is important, otherwise you end up
with your antenna pattern being skewed.

It is easy to cut cables to the correct length. The following method
gets me to within 0.3deg error on 4 cables on 432MHz.

1. Determine the minimum length needed for 1 cable and add 10cms or 4 inches
2. Cut a piece of plastic cable conduit to the length determined above plus 1 or 2 inches (5cm), it must be stiff enough not to bend too much, it is OK to use conduit joints
3. Install a connector on one end of the cable, the conduit must not allow the connector to enter end,    but it should act as a stop
4. Butt up the connector to the end of the conduit and pull the coax tight
5. Saw off flush with the opposite end of the conduit
6. Remove the cable and prepare the connector on the other end. This is
   your reference cable
7. Take care with your measurements, I use 1/2 inch hardline with a cable
   prep tool so the cable ends are all the same
8. Repeat for as many cables as you need

If you use a good quality cable from the same drum this will produce
perfect repeatable results. I use SCF12-50 or LCF12-50 and spinner
connectors.

I have made 8 cables for my 2m Xpol, 2 cables for my 2m tropo array and
4 cables for my 70cms array. I have a proper vector network analyser and
as stated above my max error longest to shortest on 432 MHz was 0.3deg!
This is far better than you need. In professional arrays I am told that
they cut to 5 deg errors. I was also told that errors of up to 10 deg
are probably OK. I am sure that my antennas have far greater errors
during high winds due to a little waggle factor.

Of course, you can use aluminium tube if you have it. I used plastic
conduit because I can buy it a few km down the road and it is very cheap
and easy to transport.
It is very quick.
Works for me and it will work for you.

73

Conrad PA5Y

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