VHF Antenna Cable Connection at Base of Mast

[geoffschultz]

After a lightning strike which vaporized my VHF antennas, I'm replacing the antenna cable. At the base of the mast I currently have PL259s and a female union. I was thinking of using a male/female BNC connectors instead as it seems to me that having an additional connection (each side of the female union) increases the loss over a single BNC connection.

My radio knowledge is minimal, so I'd like to ask the opinion of people who know a lot more about this than I do before ordering connectors.

-- Geoff

 

[Don S/V ILLusion]

I have read studies showing that the loss through bnc or the ubiquitous vhf connectors is negligible. There is also a YouTube video showing similarly negligible loss through a dozen or so vhf connectors many of which were old, daisy-chained together.

In other words, use whichever you prefer.

 

[JRacer]

When I rewired my mast, I set it up like this, see the pics. All the wiring comes up through the mast support at the top above the headliner and up through a pipe. The pipe is sufficiently tall that water in the step will run over the top of the step before it can enter the pipe should there be any leak in the seal. The pipe was epoxied in place and sealed after the wires were fed up through it. The connectors I used for the wiring are waterproof "Weather Packs" and as you can see one set of wires at the base has a male connector and the other has a female. In that way, there is no opportunity to connect one plug to the wrong mate. On the VHF (big cable) and the TV (small cable) I sort of stayed with the OEM setup and routed them through the bump-out in front of the mast (originally all the wiring was fed through grommeted fittings through the bump-out - bad plan IMO as connectors were a PITA to feed through them). Only problem with the way I have the VHF and TV cables coming out of the deck is that they tend to get in the way of the jib sheets. If I had to do over, I would find a way to feed them up through the mast step similar to what I did with the lighting circuits - difficulty is they have to be able to be screwed on to the connector inside and out. I suppose a short stub of cable with connectors on each end (one inside the boat and one outside could accomplish that.

If memory serves me correctly, I got all my coax cable and connectors through L-Com (L-Com.com) and I went with the bigger VHF cable to reduce the loss from the length of cable - 43 foot stick plus the run back to the nav console from the inside base of the mast.

 

[Brian D]

The female mate to the PL-259 is called an SO-239. If you want to go BNC you can, but that is not the "standard" for that type of system. Don't get me wrong, you certainly can go BNC. However, if you decided to change the cable again, most cables will already come with PL-259 connectors. This is by way not a game stopper.

As Don says, you will have more loss in the cable than in the connectors (unless the electrical connection within the connector is bad).

 

[geoffschultz]

Thanks for the feedback. I guess that I'll stay with my PL-259s and SO-239s.

-- Geoff

 

[NYSail]

Keeping on this subject as I am going to rewire my mast...... what type cable is recommended / best performer.

Greg

 

[JRacer]

I went with 14/3 Marine Cable - got it through Defender as I recall. My lights on the stick are not LED's. I went with the biggest cable I could that was suitable for running up the internal conduit in order to minimize resistance (power loss) resulting from the cable length.

 

[Brian D]

@NYSail, the most common would be LMR240 or RG8X. Both are about .25" diameter and have a good bend radii. Next would be the heavier LMR400 or RG8. These a larger diameter (about .5") and require a larger bend radii.

 

[jssailem]

Greg
Simple question to a complex issue.
VHF radio band is 30 to 300 MHz. The Marine channels we use to transmit on are from 156.050 MHz to 162.025. The Weather channels are from 162.400 to 162.550 MHz.
So your looking for a Coax "the length you need" that has an acceptable low loss within the range you will be using. Your radio is looking for a 50ohm antenna do you can eliminate everything else..

Here is a link to a chart that will give you info on the various types of cable.
http://www.universal-radio.com/catalog/cable/coaxperf.html

I bought LRM400 ultra flex for about $1.00 per foot. Too early to tell if the investment was worth it as it has only been up 1 year. I am figuring not to have to play with the wiring again in my lifetime. My radio works great. I can hear Canada from Everett WA.
http://www.hamradio.com

You might want to check out a local Ham Radio resource to see what they can share info. They are a wealth of knowledge about radios.

 

[Don S/V ILLusion]

I went with 14/3 Marine Cable - got it through Defender as I recall. My lights on the stick are not LED's. I went with the biggest cable I could that was suitable for running up the internal conduit in order to minimize resistance (power loss) resulting from the cable length.

Given the context, I think NYSail is asking about coax.

Others have already given good advice. The only addition I have is to consider the length between radio and antenna when choosing coax based on loss characteristics. Loss of effective radiated power increases as length of coax increases. If you have a very short run, it's less important what you chose.

 

[Mark Maulden]

Back to the OP question...BNCs are nowhere near environment resistant as the PL-259/SO-239. Decades ago, I did some bench testing for insertion loss on BNC/PL-259,SO-239/N connectors. The best was "N"followed by PL-259/SO-239, then BNC. This is also frequency dependent and I think I used 150MHz. If I remember correctly, the BNC had a loss of around 1.5 dB...the others were about half

 

[geoffschultz]

Back to the OP question...[clip] If I remember correctly, the BNC had a loss of around 1.5 dB...the others were about half

In that case, doesn't an SO-239 have 2 insertions, equalling a single BNC? Why does a BNC have twice the loss of a PL-259? I would think that the composition of the pins/socket would have a lot to do with loss. I'm looking a BNC connectors that have gold pins, sockets, etc and trying to understand what to utilize. Really, I'm just trying to understand and am not trying to be a nay-sayer/stir-the-pot type person.

-- Geoff

 

[Ken13559]

Thanks for the feedback. I guess that I'll stay with my PL-259s and SO-239s.
-- Geoff

Do get a new SO-239 even if the old ones looks good after lightning strike. I had same experience with lightning changed everything but the SO-239 and had been struggling with bad vhf for sometime until i replaced the seemingly still ok SO-239.

 

[Crazy Dave Condon]

When I use to sell the smaller sailboats that were trailerable, I used the following for the PL 259:
https://www.westmarine.com/buy/ancor--pl-259-style-deck-feed-through--238568?recordNum=2
as it is a two inch double male connector with locking nuts for each end. You can purchase a separate cap to keep the elements like rain out when not in use. Easy to screw in and easy to take off. Did not see much loss in use of the connector. It sure made it easy for the wire to be disconnected fast and when taking a boat out and mast down preparing it for travel on a hot day, the above was the key to making things quicker.

 

[vizwhiz]

Are your connections on the Fast 40 inside the mast walls or does the cable exit the mast and go through the deck outside the mast area? Just curious...