Re: COAXIAL CABLE LMR400


Raymond Brooks
 

Hi I'm interested in using LMR400 or equivalent on my mast as I can't find connectors for FSJ2-50. Has anyone used it above 5GHz and is so what sort of losses?

On 9 May 2021 11:51 am, "Reg Woolley via groups.io" <g8vhi@...> wrote:
I agree many use FSJ 4 50.however that has a very fragile outer jacket and can easily be rubbed away.

Reg g8vhi 



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-------- Original message --------
From: "alwyn.seeds1" <a.seeds@...>
Date: 09/05/2021 10:28 (GMT+00:00)
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] COAXIAL CABLE LMR400

Dear Martin,

If you need flexibility for rotator loops, then LMR400-UF rather than LMR400 is what you need.

There are many clones, some good, some bad, as others have commented. Foam dielectric cables are not easy to make as fluctuations in foam density in extrusion cause fluctuations in characteristic impedance. Look at the swept frequency return loss, if the manufacturer dares publish it. Of course some manufacturers publish data but the actual cable performance falls short of what is published.

I find that LMR400-UF works quite well for rotator loops, provided these are designed with no sharp bends- the foam in LMR400-UF is denser than in some of the alternative cables, so that displacement of the inner conductor with repeated flexure is less of a problem. I have loops that are getting on for 10 years old and still work fine at frequencies up to 1298 MHz.

Times Microwave, which is a subsidiary of Commscope, also have a MIL-SPEC flexible tactical cable series, that has a special tape shielding which is more suitable for repeated flexure than the bonded foil used in LMR400-UF- I am awaiting pricing details for this. It will probably be quite expensive as conductors are silver plated, construction is complex plus there are the extra quality control costs to retain a MIL-SPEC approval.

Regards,

Alwyn G8DOH
_____________________________________________________

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.
_____________________________________________________



--
Raymond G8KPS

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