Possible to cut vhf cable and not lose power?

demonboy

demonboy

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I have 20m of rg213 that I'd like to use for a new installation that requires 30m. Is there some kind of booster box available that will join the 20m to an additional 10m without any compromise, or do I just bite the bullet and buy new 30m? Obviously I'm trying to avoid doing this from a budget pov but I do not want to compromise on TX power.

Cheers
 
My VHF cable is cut at the base of the mast and fitted with a Bulgin plug & socket for the cable to enter the boat. Don't see any reason why you should not be able to do what you want with a suitable coax fitting.
 
Useful way to get the cable down the mast is use a line with a short length of bicycle chain on the end. This should keep it clear of twisting on halyards. To extract at the base is easy if you take some long cable ties and join them into a longer strip. Insert this inside the mast, before dropping the weighted line, as it will sit around the inside of the mast. Then pull out with the line in the loop! Very quick and simple to do.
 
Any connection on VHF coax will incur losses and reduce your RF power at the antenna...... In an ideal world you should use 30 m of coax with no joins. In the real world that is not always possible so do what you can to reduce losses. Use the best quality plugs you can afford and ensure they are terminated properly. Also ensure they never get damp!!
 
You can do a butt join by soldering the ends together. In terms of impedance matching, wrong but losses negligible. Just make a good job of taping it up with self amalgamating tape. Can be better than badly made up and corroding connectors.
 
You could also technically tie the ends of a damaged seatbelt together to repair it..... the losses in strength could be negligible but common sense tells you otherwise.

Your life could depend on your VHF one day..... do it properly..... ensure you get 50 ohms all the way..... no bodges.
 
Alpha22 said:
You could also technically tie the ends of a damaged seatbelt together to repair it..... the losses in strength could be negligible but common sense tells you ot
Your life could depend on your VHF one day..... do it properly..... ensure you get 50 ohms all the way..... no bodges.
Click to expand...

It's a perfectly sound way of joining VHF coax
 
Hmm... if you don't mind loosing 50% of your Tx power. Even a good connector, well made can loose 3dB.
25 watts of VHF RF splattering out of a hole in the cable is going to play havoc with any other electrical systems, particularly GPS reception. Mobile phones and other RF noisy equipment is going to compromise the reception too. RF does not react the same way as 12 volts DC.

The OP asked if it will loose power...... the answer is yes.... any join will loose power. Using the correct connectors will mitigate that.

A chocolate block will work up to a point, as will twisting the ends together and fastening with chewing gum, but when the boat is healing at over 45 degrees, waves crashing over the foredeck, you are taking in water, the sails are blown out, the batteries are about to be submerged....... that last call on the VHF will be the difference between life and death ..... I would want to know I had done everything to ensure that my mayday will be heard...... wouldn't you?
 
I would disagree regarding losses in joins of coax at VHF frequencies. It is nothing compared to long runs of cable. I think the primary concern is for long term robustness of the join. Certainly one continuous cable must be more reliable long term. But if you need to make a join ie at deck level then do so with a well covered join. Preferably using coax fittings. Use any money you save for an emergency stern rail mounted antenna. good luck olewill.
 
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