COAX FEED LINE LOSS.

As everyone who has ever come into contact with me understands I am FANATICAL about feed line losses.

With the changes on the tower, automatic relay switching, pre-amps and the Elevator, I am looking at 8 - 25ft low loss rotor jumpers from the antenna to the top of the tower for the hard line connection.

In the past I have always used LMR-600 Ultra-Flex, Jerry KB2WDM has really been a huge promoter of the new Italian Messi & Paoloni Coax, so I thought I would give it a try out and see how it performs.

I honestly have to admit, that I am more or less impressed with it, and I especially like the connectors that they provide for this specialized cable.

It is EXTREMELY FLEXIBLE AND provides good low loss, specially on the shorter runs so that it is perfect for the jumpers between the antennas and the hard line and with the excellent flexibility it works very well for the rotor loop at the top of the tower.

I purchased a 100ft of it, to do some side by side real world performance test, and in a fashion that would allow the novice Amateur to the experienced to understand exactly the impact that the different coax feed-lines can have on your signal.

For our testing purposes we will focus on 2 meters at the Single Side Band calling frequency of 144.200 and will use 100 Watts as our base power injection.

For our test, we have set up equal lengths of Feed-line RG-58, RG 213, LMR 400, LMR 600, UltraFlex 13/.500, 1/2 hard line, 7/8 hard line and 1 1/4 hard line.
A FM Transmitter putting out 100 Watts into the head-in of the feed-line with a Motorola watt meter, and a dummy load rated to 1000 MHz. The SWR with the dummy load and watt meter is a clean 1.1 SWR.

The 100 watts is fed into the 100ft length of coax and with the exception of the RG-58 and RG 213, N connectors are used.


Coax Type: Watt Reading Loss % Note:
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Belden RG-58 33 Watts 67% Used this as a joke
Beldon RG-213U 53 Watts 46%
LMR 400 69 Watts 30% What most people use for low loss
LMR 600 79 Watts 21% My normal go to for rotor jumpers
M&P Ultra-Flex 500 82 Watts 18% Extremely flexible
Andrew 1/2 82 watts 18%
Andrew 7/8 89 Watts 10%
Andrew 1 1/4 92 Watts 7%

As you can see the M&P Ultra-flex 500 performed very well, plus it has the advantage of being extremely flexible. I believe the quality of the connectors that is designed for this cable plays a bit roll in the loss levels. They are extremely high quality.

On all future projects, I will be using the M&P UltraFlex 13/.500 feed line for my rotor jumpers at the top of the tower, combined with the lengths of under 30ft in all most all applications the loss is very low and will not impact my performance.

NOW A VERY IMPORTANT FOOT NOTE: Keep in mind the loss you are seeing in the cable and equate that to not just your transmit but your receive as well and invasion.

So imagine that weak signal you want to hear, if you take 30% of the signal strength away with feed line loss…..

Looking at this chart, you can understand why I place so much importance upon Feed-Line loss.