splicing coax

[Fishermark]

A couple of weeks ago I asked for some suggestions concerning a new GPS unit. I ended up buying a Garmin 186C with an external antenna and love it. The problem is - I accidently cut the coax cable in half. (Don't ask ), near the antenna. I spliced the coax (soldered the inner wire - heat shrink - soldered the shield - more heatshrink). The GPS unit works but it seems to take longer to find and acquire the satelites. It could just be my imagination however. Is there a better way to splice or am I okay? (Or worse yet, do I need to buy another antenna?)

 

[Sea Mitch]

Re: splicing coax

I'm not really qualified to reply, but if it were sonar, you'd have to buy a whole new unspliced wire. Anytime there is a splice I would assume there is loss. If you want it to work perfectly, you have to buy a new one. If you can put up with what you have and it seems to be adequate, stick with what you have and save your money. The sheilding and insulation in the coax is to "protect" the signal. When it's compromised, there will be loss. If you do a real good repair job (on which hopefully someone will post how), you will minimize the loss.

 

[nightstalker]

Re: splicing coax

You can buy coax splincers at radio shack. They work great and make a tight reliable splice. They sell twist on splicers as well as the crimp style. I've used them quite a bit and have had no problems.<br />Stalker

 

[Troy_from _Oz]

Re: splicing coax

I think there are two fields of thought on this. The hard core electronics people would say that the coax should be length tuned with an osciliscope to allow optimal readings in the right frequency band. Others would say that it doesnt really matter too much either way. This part of the debate deals with how the signal is transferred down the line... <br /><br />My experience is that it doesnt matter too much - I had some VERY long antenna cables made up and I didnt see any real problems with the GPS data. Each antenna cable was 100metres long! <br /><br />However - with any break in the cable what you will have is a loss in the signal power that reaches your receiver. This will happen with any soldering and it will also happen with and splicing connectors that you put inline too. The general rule of thumb is that each connector equates to about 1dB of signal loss. Therefore if you make up one male and one femaile connector to splice together - you will have 2db loss. How this compares with solering - i dont know. Obviously the best thing to do then is to buy a new cable - if the antenna and cable are one piece - this is expensive.<br /><br />The signal loss may attribute to longer time to lock on to some sats if the satellite signal is weak already - or if you are introducing more noise into the equation through your soldering. I guess that weak sats will also drop out earlier too - which may slightly degrade your solution - but i would think that this would be marginal.<br /><br />If it were me I would replace the cable if it is separate from the antenna - if the antenna and cable are one piece - i would leave it as it is (soldered and splicesd like you have) - provided that you are confident that your soldering job is good and that there isnt any possibility of shorting out your antenna (or receiver). - thats just what I would do (if its not for a critical application) (also no warranty or guarantee implied!!! ) - but i work to a budget all the time so make do with what i can.<br />Hope this helps.<br />Troy

 

[Peter J Fraser]

Re: splicing coax

I'd be inclined to join the coax using either PL259 M/F connectors or BNC. You are less likely to get interference that way. <br />My .02 worth.<br /><br />Peter

 

[rc581]

Re: splicing coax

i definatly agree with peterf. use the bnc connectors or the pl259s. you want to keep the shield all the way around the cable, and these plugs will accomplish that. good luck.....bob

 

[Troy_from _Oz]

Re: splicing coax

Good point Peter and RC, but... <br /><br />Nah - just kidding - no buts, seems like fair comments and better way to go... Any thoughts on crimp vs solder connectors?<br /><br />Troy

 

[Peter J Fraser]

Re: splicing coax

Crimps are OK if you can get good styles. Solder can actually increase the resistance of the cable at the solder join. Some that I have used in the past solder the center conducter but crimp the sheild. <br /><br />Go and see **** Smith Electronics, they will be able to supply all you require to do a good repair on that coax<br /><br />I see you are in WA. I lived in Perth myself back in the mid 70's. Great memories. Good luck<br /><br />Peter

 

[Peter J Fraser]

Re: splicing coax

From the above it looks as if my post got an auto edit done on it. I guess you know who I mean.

 

[dogsdad]

Re: splicing coax

Splicing an antenna co-ax is not an effective fix. It screws up the SWR and will seriously degrade performance of a receiver, and can cause damage to a transmitter. <br /><br />I would put PL259 (or whatever might be apprpriate) connectors on each end and use a butt adapter. Then I would seal it to keep moisture out. Another option may be to use N-type connectors since you're just joining two cables. There are some really good N-type crimp-on connectors available and I always thought they were easier to work with than any PL259 type stuff.<br /><br />Solder-on connectors are really the best way to go, if you can install them correctly. It requires a LOT of heat to get the shield soldered right, and it's easy to mess it up. Crimp on connectors can work just fine, and are easier to install---but they have to be done just-so also.<br /><br />Whatever you do, don't just twist the conductors together and call it good. I'd bet a dollar to a donut that's why your GPS is taking so long to lock onto the system. You're not getting ful performance out of your GPS.<br /><br />-dd-

 

[Fishermark]

Re: splicing coax

I went ahead and cut my splice off and bought a connector - it's a nice unit I purchased at the local marine store (specifically for splicing coax). Seems to work okay - I am taking the boat out tomorrow and will let you know how it works!

 

[Boatist]

Re: splicing coax

FisherMark<br />Going with the splice is the right way to go. That is the only way to not affect the impedence of the coax.<br /><br />When you get out go to the Satellite page on your unit. This will show you how strong each bird is. Look and see if you can see WAAS Satellite # 35 AOR-W (Atlantic Ocean Region West) This bird is geostationary over the equtior at 54 degrees west Longitude. If you can see that your unit is fine. One more very weak bird would be WAAS bird 33 also geostationary over the equator at 15.5 degrees West longitude.<br /><br />Make sure your connector is water proof. Getting water in the coax will degrade the signal.

 

[Dan McCosky]

Re: splicing coax

You should use aluminum tape over the spices,It will shield the wires from stray RF signals.Just my 2 cents worth.

 

[BrianTindall]

Re: splicing coax

First off, with ANY receiver that can display SNRs, record them upon first installation and setup. Now you have a baseline for it's performance. Had you done that first, you'd know if you had a signal loss due to the splice/repair. Keep this in mind for the future. Now, how far away was the cut from the antenna? If it's less than 2 feet or so, then remove the "tail" from the antenna and solder the other peice to the antenna. If the antenna is sealed then the appropriate splices listed above are the best way to go. Make sure your splice is sealed against moisture. Braided wire (or any stranded wire for that matter) such as in coax sheilding will wick water like an oil lamp.