Re: Wimo 13cms yagi


John Lemay
 

Hello Alwyn

 

I’m interested in your comment about connectors because very recently I had a problem with what looked like, at first sight, a decent quality 50ohm N type termination (male):

 

It showed a good return loss to around 2GHz, becoming very poor (-6dB) around 2.5GHz and then improving significantly above that frequency. Is that what is called “suck out” ?

 

On inspection I decided that the pin was making good contact and so was the screw ring. But the more important inner fixed ring was sometimes not making contact – which I proved by carefully making it slightly oval – problem (crudely) solved.

 

It makes me consider that plugs that have the inner ring split into “fingers” are a better bet ?

 

Regards

 

John

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of alwyn.seeds1
Sent: 16 November 2019 10:23
To: UK Microwaves 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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