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Author Topic: Barrel connector loss on 2M/440?  (Read 3287 times)
N4NYY
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« on: November 11, 2012, 06:17:19 PM »

A friend was running about 75 ft of coax for his 2M/440 mobile rig in his home. He said he would be about 20 feet short. He asked me about how much loss it would be at that freq. He is running LMR400.
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KM3F
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Posts: 509




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« Reply #1 on: November 11, 2012, 08:19:33 PM »

For use in FM service into repeaters; as long as the repeaters are able to be accessed it makes little difference.
Otherwise to get nit picking, a barrel connector on 440 is not very good for swr match.
I have done extensive testing of connectors into a flat 50 ohm load termination and see those that don't do well for weak signal best match antenna system use.
Unless the application demands the best feedline match, the barrel connector will work ok.
An swr meter test will tell what the connector does when inserted into the feedline.
Good luck.
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KA4POL
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« Reply #2 on: November 11, 2012, 09:57:47 PM »

If one needs a connector anyway why not use a good one like N? A barrel connector represents a discontinuity for the 50 Ohm line.
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K1CJS
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« Reply #3 on: November 12, 2012, 04:13:27 AM »

Unless you want to get into a repeater that is out on your fringe area, use of a barrel connector--even on 440--isn't going to do much harm to your signal strength.  Granted, there is an impedance 'bump' in the line where the connector is, but for all practical purposes, it's negligible--except to purists.   Grin
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AA4PB
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« Reply #4 on: November 12, 2012, 04:28:48 AM »

They do make type "N" barrel connectors.
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KCJ9091
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« Reply #5 on: November 12, 2012, 07:01:14 AM »

In both 50 and 75 ohms.
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KQ6EA
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« Reply #6 on: November 12, 2012, 09:54:56 PM »

Yes, and DO NOT intermate them!

The 50 Ohm center pin in the male will destroy the 75 Ohm center contact in the female.

One of the "Technicians" I used to supervise at a broadcast uplink ruined several thousand dollars worth of 75 Ohm combiners by mating them with 50 Ohm male connectors.

73, Jim
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WB6BYU
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« Reply #7 on: November 13, 2012, 05:29:48 PM »

The losses of properly-built connectors and adaptors are relatively low, even on 440.
I seem to recall that N3OX strung 40 of them together and measured a small fraction
of a dB loss at 440.  The loss in the extra 20 feet of coax will be more than that of
the connectors and a barrel.

Meanwhile the loss in 20 feet of empty space between the rig and the end of the coax
will be far larger than that.


Don't over think the problem:  use a barrel, weather proof it as needed, and forget about it.
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N3OX
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« Reply #8 on: November 14, 2012, 08:50:49 AM »

The losses of properly-built connectors and adaptors are relatively low, even on 440.
I seem to recall that N3OX strung 40 of them together and measured a small fraction
of a dB loss at 440. 

I did that on 10m, but K2DC reports a similar test with adapters at 1.3GHz with a similar conclusion.
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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