Author Topic: Should I Shorten Antenna Cable?  (Read 644 times)

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Offline SylvestreTopic starter

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Should I Shorten Antenna Cable?
« on: November 15, 2013, 06:00:39 PM »
Hello,

I have a small issue I need some advice on.  I am building a robot and I am really focusing on wiring organization with this iteration. I just received the antenna in the mail, but the cable is like 15ft long.  I would just splice it, but its coaxial cable, which I've never dealt with before.  I know coax cable is mainly used to prevent interference.  I am fairly experienced solderer, but I do not want to have any external electrical noise problems.  How hard is it to splice coax cable?  Do you recommend it?  Will it affect the gain if I shorten it?  Otherwise it is going to be a real pain to try to hide this much cable when i really only need a foot.

Thanks
« Last Edit: November 15, 2013, 06:04:02 PM by Sylvestre »

Offline waltr

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Re: Should I Shorten Antenna Cable?
« Reply #1 on: November 15, 2013, 06:57:38 PM »
Do not splice coax.
Shortening the coax is easy. Just cut to length and install a new connector.

What type (number) is the coax? RG58? RG58/U?
What type of connector do you need to interface with the transmitter or receiver? UHF, BNC, etc?

Post a clear, in focus picture of the connector if you're not sure what it is.

Or disconnect the coax from inside the antenna base (its probably just soldered to lugs). Then cut the coax to the the length you need from the connector. Strip the coax as it was in the antenna base and solder back on. Again if you're not sure post a clear picture of the connections.

FYI: Coax is also required to maintain the characteristic impedance of the transmitter/receive to the antenna. Google "transmission line" and "impedance matching" to learn more.

Offline SylvestreTopic starter

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Re: Should I Shorten Antenna Cable?
« Reply #2 on: November 15, 2013, 08:34:37 PM »
Thanks Waltr for the great response.  Exactly what I was looking for. 

Quote
What type (number) is the coax? RG58? RG58/U?
What type of connector do you need to interface with the transmitter or receiver? UHF, BNC, etc?

Post a clear, in focus picture of the connector if you're not sure what it is.


It is a RG58U coax cable according to the description of the product
http://www.amazon.com/dp/B006FRAPFW/ref=pe_385040_30332190_TE_3p_M3T1_ST1_dp_1

Below are pictures of both the male and female connector.  The male connector is the one that needs to be reconnected.

Quote
Or disconnect the coax from inside the antenna base (its probably just soldered to lugs). Then cut the coax to the the length you need from the connector. Strip the coax as it was in the antenna base and solder back on. Again if you're not sure post a clear picture of the connections.

In my case, the first solution is better since the wire is embedded into the base itself that I would rather not tear apart.

Quote
FYI: Coax is also required to maintain the characteristic impedance of the transmitter/receive to the antenna. Google "transmission line" and "impedance matching" to learn more.

Thanks! I'll have a look later.


**The images are too large in size so click on these links
https://drive.google.com/file/d/0B83RdnxAI6xvZmMyVmdFenF4aUE/edit?usp=sharing
https://drive.google.com/file/d/0B83RdnxAI6xvam0zMkZwelZJTW8/edit?usp=sharing

Offline waltr

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Re: Should I Shorten Antenna Cable?
« Reply #3 on: November 15, 2013, 09:53:00 PM »
Nice clear pics.
In the first that looks like a 'UHF' type connector, also know as a "PL259 plug". These are very common for CB and Ham radios.
Google "uhf connector" and "PL259 plug for RG58U" to find them and how to install them. Buy the kind that screws together not the kind that is crimped on (like the one that is on the cable now).
Any store that sell CB or Ham radio parts should have these. Also be sure to get the reducer plug to fit the RG58U cable.

Is the connector taken apart in the second picture?

Offline SylvestreTopic starter

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Re: Should I Shorten Antenna Cable?
« Reply #4 on: November 15, 2013, 10:36:52 PM »
My mistake.  I thought the second picture was the male, but I just saw this link (below), which states its the female.  This is the one I need.  Turns out the connector I need is a fme female.  Never heard of it.

http://www.ebay.com/itm/15ft-RG58U-External-Antenna-Extension-Coax-Cable-/360179068998?pt=US_Other_Cell_Phone_Accessories&hash=item53dc587046

Quote
Is the connector taken apart in the second picture?

Nope


UPDATE: I was able to salvage the connector so hopefully I will be able to use the same one.  Thanks for all your help

Offline waltr

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Re: Should I Shorten Antenna Cable?
« Reply #5 on: November 16, 2013, 08:51:48 AM »
FME connector! That's a new one for me.
Good you got this sorted out.

 


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