Replacing GPS and nav text antenna cables

[BacktoBoats]

I have to replace the old cracking antenna cables on my garmin GPS, furuno GPS and nav text fixed to my rear arch . I will have to make a join in the open to the 1m flying lead coming out of each antenna. I will have a cable run of about 9m. Any definitive answers please to what sort of cable I should use, and how best to make the waterproof connections? The current connections have been made via chocolate block for the core and twisted braid for shield, insulated then put in a weather tight box (by the previous owner). I know this isn't best practice, and have seen lots of discussion about the merits of many different connectors, but still don't know what to go for. I have some good heat shrink tubing I can put over whatever connection to help waterproof if necessary, or else self amalgamating tape.

 

[PaulRainbow]

When joining coax for a job like this i usually strip back come outer insulation, braid and inner insulation. Solder the inner core and apply some glue lined heat shrink (remember to put the heat shrink on first) Then pull the braid back over, overlapping it and soldering again. If you've made a neat job, a length of outer insulation, split lengthways) should go over the braid, a little epoxy here doesn't hurt. Finally, another covering of glue lined heat shrink will seal everything up as good as new. For these jobs, tinned RG58 is fine.

 

[Refueler]

As Paul describes .... a pal who is an ex RF Engineer - he worked in a station that TX'd White Noise to stop BBC and Voice of America being listened to during Soviet times .. needless to say that most of time they were listening to BBC etc and only 'hit the switch' when boss was around.

Anyway back to Co-Ax ... he described similar - that what to work towards is to recreate the core, insulation, screen and outer cover ... to be as near to original as possible in diameters ...........

 

[William_H]

As I understand it GPS signals are in the 1000mhz range. As such losses in RG 58 cable would be significant over 9 metres. Now it may be fine. GPS operates on very small signal level. The old coax may have been RG 58 and worked ok. However looking at catalogues for coax cable. As an example this cable "low loss " shows 32db per 100m at 900mhz. Use this as a comparison for any cable you consider buying. Often the thicker cable RG8 style is lower loss but may be impractical. RF200 50 Ohm Low Loss Coaxial Cable - Altronics (you do need 50 ohm cable) ol'will

 

[Refueler]

As I understand it GPS signals are in the 1000mhz range. As such losses in RG 58 cable would be significant over 9 metres. Now it may be fine. GPS operates on very small signal level. The old coax may have been RG 58 and worked ok. However looking at catalogues for coax cable. As an example this cable "low loss " shows 32db per 100m at 900mhz. Use this as a comparison for any cable you consider buying. Often the thicker cable RG8 style is lower loss but may be impractical. RF200 50 Ohm Low Loss Coaxial Cable - Altronics (you do need 50 ohm cable) ol'will

Whether looking at VHF / GPS or whatever .. its interesting that many brands use cable that Loss Tables show is not so good ... I put it down to 'costs' !

 

[BacktoBoats]

Whether looking at VHF / GPS or whatever .. its interesting that many brands use cable that Loss Tables show is not so good ... I put it down to 'costs' !

Yes, I bought an external antenna a while ago to improve the mobile signal to a WiFi dongle distributing Internet locally. It actually made the mobile signal worse and it turned out the loss in the "low loss cable" was greater than the gain of the antenna! This seems to be common practice, hence my concern about connecting 9m of cable to my various bits of equipment.

 

[Refueler]

There is of course the trade off ..... cost - diameter of cable - flexibility of cable ....

The best cable appears to be stiff and hard to use !!