Help, I've drilled through my VHF aerial cable

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JimC

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Help, I\'ve drilled through my VHF aerial cable

Sodd's law - it was behind a panel. Is there any way of fixing it without having to replace the entire run of cable from the set to the foot of the mast. This would entail stripping out a lot of the lining panels and trim. Can the cable be joined without incurring signal loss?
 
Re: Help, I\'ve drilled through my VHF aerial cable

Use male and female TV aerial co-ax connector, and then wrap that in gaffer tape.

Here's a stripper to minimise waste (practice first on something else)

stripper
 
Re: Help, I\'ve drilled through my VHF aerial cable

Be wary of fittings for TV application. Most are cheap metal and the VHF signal will barely get through. Try a PL259 connector from Maplin or Radio Spares. We use one all the time since we don't leave our set on board.
 
Re: Help, I\'ve drilled through my VHF aerial cable

Oops!

Short answer, no you can't join it without incurring a slight signal loss.

I'm guessing also that you have a join at the foot of the mast :-(

If you're inshore (ie not needing long range) all the time then you may be okay.

I would not recommend TV Aerial connectors, or Gaffer Tape. You should be using PL259 plugs, or BNC connectors. Gaffer Tape is not fully waterproof: use Self Amalgamating tape.

Best is to replace the entire length - but use the old cable as a draw wire to pull the new one through; this will mean less panel removing.
 
Re: Help, I\'ve drilled through my VHF aerial cable

If you have enough slack you can join the cable with some loss. Use two PL259 plugs and a barrel connector. If that is too bulky use a TNC kit. A TNC is a threaded version of the bayonet type BNC and therefore more positive.
 
Re: Help, I\'ve drilled through my VHF aerial cable

I agree 50 Ohm TNC will do job Don't use TV connectors they are 75 Ohm so will be more lossy, especially important on transmit as could affect VSWR
 
Re: Help, I\'ve drilled through my VHF aerial cable

Contrary to many of the opinions expressed, I would make an inline joint by soldering the inner cores together; insulating; pushing the braids back together as much as possible; wrapping bare solid core wire tightly in a spiral across the brading and insulated core; insulating idealy with self-amalgamating. The impedance match will be far better than using TV connectors or PL connectors (they are not constant impedance) and there are no contact problems. At the frequency we are talking about any loss will be insignificant if you do the splice well. Obviously the inner core and braid must be in clean, bright condition before starting.

Vic
 
Re: Help, I\'ve drilled through my VHF aerial cable

Well I would say replace the whole cable as the textbook answer. I doubt the signal loss with a TV connector is going to be appreciablly more than with any other kind of connector. Fact is the break will either cause major disruption in your reception (dependant on what else happens to be around to cause interference) or it won't. I say try it out with cheap TV connectors (unless you have a Maplins next door) and see if you notice a difference in the signal strength or squelch setting. If you do, replace the whole cable - a better grade of connector won't fix it.

I suggested gaffer tape as a way of stopping it all coming apart. I assume it's somewhere dry. But of course, there's also different grades of gaffer tape...
 
Re: Help, I\'ve drilled through my VHF aerial cable

Vic, there will be a loss, and possibly a reflection, as you cannot acurately replicate the dielectric of the cable and spacing of the core and screen. The join will end up being a different impedance to the cable causing a reflection and loss of signal.

Any join will cause a loss, and you may not know how significant it is until you travel some distance from another VHF station.
 
Re: Help, I\'ve drilled through my VHF aerial cable

You can not test the system without travelling some distance from another station, or by using specialist test equipment. Most (all) of the suggested repairs will work okay within a marina or to nearby coastguard repeaters or within a mile or so.
 
Re: Help, I\'ve drilled through my VHF aerial cable

I use two standard tv type coax ariel connectors from Maplins on my vhf so I can unplug the ariel when the mast is unstepped. I can't see it's any worse than the through deck gland that cost me £15 a couple of years ago. Beaign in mind that any joint is bound to have an adverse result, why are these connectors any worse than the others people are recommending? I could use PL 259s quiter easily but wnder if there would be any norticeable difference.
 
Re: Help, I\'ve drilled through my VHF aerial cable

Difference would be noticeable when trying to use the VHF over longer distances.

Short distances wouldn't be noticeable difference.
 
Re: Help, I\'ve drilled through my VHF aerial cable

You do not need to strip out the wire and replace it (unless it is old and the ground braid is corroded).

Worst case is get a pair of PL259s and a barrel (SO232s) and solder the PL259s to the two ends to be joined. If the braid is not corroded then this should solder ok and give negligible loss. BNC connectors are an alternative but are fiddly - I prefer the bigger connectors.

You can join the wires direct as said above but check the loss. You need to get hold of a power meter and check the power output and SWR on transmit. Receive is likely to seem ok whatever join you make - but a bad join will give an impedance mismatch and the radio will reduce its power output if bad. Whilst the meter is "specialist" kit - you will be surprised how easy to get hold of - try and find a local ham radio operator around - there are many lurking here. PM me if you are near East coast of Scotland - I have the kit. You can make successful joints but if you are going to rely on the radio then check it has worked.

As I say, worst case is a couple of PL259s well soldered.

Dr Bob
 
Re: Help, I\'ve drilled through my VHF aerial cable

Wow. Isn't that cool!

pl258cp.gif


Have you tried it? Is it easy to use? Particularly in a confined space..?
 
Re: Help, I\'ve drilled through my VHF aerial cable

This looks rather nifty.

Wouldn't want to use one in a marine environment though; the method of contact to the screen and core is not 'secure' like with a soldered or crimped connector. Slightest amount of corrosion and it'll stop working. It's like an IDC (insulation displacement connector) connection. Would be happy to use these ashore though.
 
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