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Diganet
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How much can a cable bend?

Wed Dec 27, 2006 2:42 pm

Hi,

Wwe are having some issues (maybe) with some MT pigtales (u.fl - NF). Problem is their casing is a bit too small and the lid touches the backside of the N-Connector where the pigtale cable is mounted so that the pigtale cable gets a 90 degree bend and lies almost flat on the N-Connector. How Much does this influence on signal? I know this is not the right way to do it, but we had to build some quick links and used what was available.

We have a 6km LOS , 2 x RB532 on each side dual polarized 23dBi panels (5Ghz) and SR5 cards in all RB's and we get no packets through, not even if we sniff.. Nothing... and the only thing i can think of is the pigtails..

Anyone?

/Henrik
 
miles
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Tue Jan 02, 2007 7:22 pm

hi Henrik..
the lid is plastic shouldn't make you any problem. About bend for pigtail I don't know about degree but you can bend that much you think is enough, but you can bend the pigtail I have bend pigtail in my MT and work just fine for me.

cheers
miles
 
Hellbound
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Tue Jan 02, 2007 8:41 pm

you have to check manufacturer website and specs for this.
I remember I specificily checked time microwave website and
for some special case we had to buy second version of LMR400
that could bend some more.

hope it helps.
 
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nickb
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Tue Jan 02, 2007 9:27 pm

With the tiny wire on UFL pigtails I would imagine that you've snapped the wires inside and are not making an electrical connection at all.
 
ejansson
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Tue Jan 02, 2007 9:49 pm

All types of wire have a maximum bend radius; the cable manufacture can supply the details. The higher the frequency the more likely a sharp bend can cause problems. If the cable is kinked to make the bend you can end up reflecting the signal back to the radio. We will cut out or replace any LMR 400 that has been kinked, even at 900 MHz you can see 10's of db drop from a kink, the foam dielectric gets deformed and changes the cable characteristics. As mentioned you can often break or disconnect the center cable on small cables and connectors.

Erik
 
Diganet
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Wed Jan 03, 2007 1:04 am

Thanks guys,

I finally got hold of some u.fl - NM pigtales and will change them tomorrow and let you all know what happens. With this pigtale we save about 5cm room in the enclosure. The lid is metallic and i suspect a shortcut in the 5GHz signal because of what we did.. Anyone knows if this could have damaged the SR5 cards? More because we rent a $200/Hour lift to get on top of this and have 7 radios up there and perhaps we should change the SR5's as well instead of learning the hard way ;)

/Henrik
 
Hellbound
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Wed Jan 03, 2007 5:25 am

Thanks guys,

I finally got hold of some u.fl - NM pigtales and will change them tomorrow and let you all know what happens. With this pigtale we save about 5cm room in the enclosure. The lid is metallic and i suspect a shortcut in the 5GHz signal because of what we did.. Anyone knows if this could have damaged the SR5 cards? More because we rent a $200/Hour lift to get on top of this and have 7 radios up there and perhaps we should change the SR5's as well instead of learning the hard way ;)

/Henrik
if that is the case, I suggest you test your unit at least 48 hours before you put them up there.

you can also simply test your pigtail with multimeter to make sure that the center cable is not disconnected. and even test it with actual unit under heavy bandwidth.
 
Diganet
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Wed Jan 03, 2007 4:43 pm

Whee!

Changed pigtales and now have -55 RSSI on a 6km link LOS. I am able to push 25Mbit TCP on each of my links (dual polarized) and +40Mbit UDP.. Great stuff.. None of the cards were damaged because of the smashed pigtales, lucky me :-)

/Henrik
 
phendry
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Sun Feb 11, 2007 9:33 pm

We are in the process of setting up a similar link. Distance is about 8km and each end consists of an RB532's with 2 CM9's in an MTi enclosure with 23db dual pol MTi panel antenna. We are bonding EoIP tunnels across 2 standard N-Streme links. Signal on both links are as expected but when we try to pass traffic over both links we have nothing but trouble and it doesn't seem to matter what frequencies we use. Did you have anything similar when you setup?
 
slipstream1
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Sun Feb 11, 2007 10:42 pm

A general rule of thumb on bending any wire is bend no tighter that 10 times the radius of the wire.
 
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bjohns
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Mon Feb 12, 2007 3:12 am

Also don't forget there's LOTS of connector styles out there and the chances are that you can find one that suits your particular application - ie a right angle entry.

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