Splicing WeBoost cable?

[kga1978]

I bought a WeBoost Drive Reach OTR a little while back and I just broke the antenna trying to unscrew it. WeBoost will mail me a new antenna (cat # 311229), but I really really don't want to have to redo all the internal wiring since that's an absolute PITA in my Grand Cherokee. I'm therefore planning on shortening the cable of the new antenna and splice it to my old cable, before waterproofing everything. But here's the problem - I can't for the life of me figure out what connectors I need? I don't know much about coax cables and there are a million different connectors - RG6, RG11, RG58, SMB, SMA, etc....

Does anybody know what connectors I need? And what tool? Most tools/connectors I can find on Amazon seem to be RG6, but I don't think that's what I want here?

 

[Chris Boyd]

Do you know what kind of cable it is? It would be something like LMR-xxx or RG-xx. From there the appropriate connectors can be identified. Likely you’d need a male connector on each end to be spliced and then a female/female connector to join them.

One word of caution - as a rule of thumb, each time you pass through an RF connector, you’ll lose 3db of signal - when they are made perfectly. As fussy as I hear these weboost to be, and how marginal gains can sometimes be, I’m not sure I’d risk the signal loss.

If you decide to proceed, you might look up a local 2way radio shop or place that works on first responder vehicles to make the splice connectors for you. They might even solder the splice, keeping the loss minimal. Save, that a local ham operator might do you a solid…

 

[kga1978]

Thanks Chris, very helpful. So I found out it's an LMR-195 cable and I'm assuming SMA connectors would be the way to go. WeBoost themselves recommended I did not splice the cables because of data loss. My initial reaction was "whatever, I'm sure it'll be fine", but I think my first post made it clear that I know nothing about this sorta stuff, so maybe they're right based on what you're saying?

Having to rewire would be a total PITA, but it could be done...

 

[DaveInDenver]

You can't really splice coax like it's battery cable. I mean, you can sort of if you know what you're doing. But terminating the two ends you want to join with connectors is far more reliable mechanically and electrically.

LMR-195 (which is similar to RG-58 coax) and SMA connectors seem plausible but if you can post a photo of the connectors it will be easy to identify them. You also sometimes see FME and very rarely SMB connectors used in this application.

BTW, you don't loose 3 dB for every connector. It could be the case with the SO239/PL259 type but a good BNC (such as Amphenol) is either 0.2 or 0.3 dB insertion loss up to 3 GHz. The exact insertion loss depends on military or commercial and whether it's double crimp or crimp/solder.

For SMAs you use the formula 0.06 * SQRT (F[GHz]) up to 12.4 GHz. On Band 5 (800 MHz) an SMA should test to an insertion of no more than (0.06*SQRT(0.8)) = 0.053 dB. So cutting and splicing a male and female SMA will give you a about 0.11 dB of loss. On Band 2 (1900 MHz) the loss is 0.082 dB per connector.

That's in addition to the extra coax, LMR-195 gives you 11.1 dB of loss per 100 feet at 900 MHz and 16.5 dB/100' at 1900 MHz, so adding say 10 feet incurs about 1 to 2 dB of loss as well. So a couple of connectors and a few feet of coax will end up with perhaps as much as 3 dB total loss.

But getting these values does require using correct technique (e.g. the right crimpers) and good workmanship. It's very easy to hack on a connector and get 3 dB, especially SMA. The center pin especially on those is a pain, which is usually soldered.

 

[Chris Boyd]

Well I think Dave pretty much covered it.

LMR-195 and SMA is challenging combo without the right tools and experience. I think the frustration of Re-running the cable would be less than trying to get this spliced, not getting it to work and then having to order another antenna again…

Good luck!