Re: Wimo 13cms yagi


John Quarmby
 

The older Andrews FHJ4-50, a predecessor to LDF4-50, has helical corrugation of the outer, very obvious when you inspect the interior of the connectors used on it which are also helically grooved. I think it dates back to the late 70s, so not seen much these days.

73

John G3XDY



Sent from my Samsung Galaxy smartphone.

-------- Original message --------
From: "alwyn.seeds1" <a.seeds@...>
Date: 16/11/2019 10:23 (GMT+00:00)
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Wimo 13cms yagi

Dear All,

Cable and connectors.

I have measured very deep (20dB) suck-outs and corresponding reflection spikes around 2.3GHz on some samples of Ecoflex 15.

I have also measured severe suck-outs, but usually above 3 GHz, on poor quality N-Type connectors.

Definitely check your cable and connectors carefully, before working on the aerial.

Regarding the comment on “Heliax”, I do not agree. 

All foamed dielectric solid outer cables that I have seen do not have helical corrugations.

I have measured many samples of these cables up to their rated frequencies and above.

The large LCF-78 types are rated to 6GHz and have no problems at all at 2.3GHz.

The upper frequency limit is normally set by circumferential modes in the cable- the spacing between the corrugations is chosen so that the periodic feedback from these occurs above this frequency.

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.
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