Need help identifying antenna connector and advice going forward

[stormalong]

LMR400 is not a good choice for marine use. It uses aluminum conductors, needs a crimped on connector and any water intrusion will quickly damage it. Foam dielectric acts like a sponge to soak up any water that gets in.

For the same reason I don't like the idea of a right angle connector at the base of the mast. Waterproofing this connector will be difficult. If this is to be sealed up access to inspect and service it will be non existent. This is why an uninterrupted run from the antenna to the radio is best. Although the signal loss at the connector is insignificant, the potential for water intrusion is high.

[AlanR]

Originally Posted by chollapete

Thanks. I know. I'd prefer RG-213, but do to cost and bending radius I'm leaning toward Ancor RG-8X.

The run is about 55 feet, so a table at West Marine shows attenuation at 60 feet for RG-213 at -1.6dB and RG-8X at -2.7dB. I don't entirely understand decibel math, but exp(-1.6) ~ 0.2 while exp(-2.7) ~ 0.07.

He had been running (and was happy with) old RG-58CU with attenuation of -3.6dB ~ exp(-3.6) ~ 0.03. Not sure how to convert all this into percentages.

Also, it may have been that he could hear others clearly, but others heard garble when *he* transmitted.

Decibels are serious, and refer to power ratios, as follows:
3dB loss means you will only get 50% of the power out the other end. 6dB means only 25% out. 10 dB means 10% out.

Using RG-8X means you would lose nearly half of both transmitted and received signals in the co-ax. Not good.

I hope this helps.

Alan
GU3ONJ

[chollapete]

Originally Posted by AlanR

Decibels are serious, and refer to power ratios, as follows:
3dB loss means you will only get 50% of the power out the other end. 6dB means only 25% out. 10 dB means 10% out.

Using RG-8X means you would lose nearly half of both transmitted and received signals in the co-ax. Not good.

I hope this helps.

Alan
GU3ONJ

Thanks. That clarifies. I learned enough about the exponential to muddle through a few tests, but never enough to reason about it on my own.

[stormalong]

Don't buy coax from West Marine. West Marine is the high price supplier on just about everything.

Look here: Davis RF Co. - Coax Cables

They sell RG-213, 50 ohm, stranded Mil C-17, non-contaminated jacket for $.85/ft. Far less than West sells RG8X for.

I bought marine grade rg213 from Davis ten years ago and it is good stuff.

[Nicholson58]

Originally Posted by stormalong

Don't buy coax from West Marine. West Marine is the high price supplier on just about everything.

Look here: Davis RF Co. - Coax Cables

They sell RG-213, 50 ohm, stranded Mil C-17, non-contaminated jacket for $.85/ft. Far less than West sells RG8X for.

I bought marine grade rg213 from Davis ten years ago and it is good stuff.

We$t is very high. I found my 50 ohm Marine cable on Amazon best price by the long, full spool. I had enough to do the main and mizzenmast.

[chollapete]

@stormalong & Nicholson57: Thanks for the supplier tip. Do you have a favorite supplier for marine grade electrical wire?

[Nicholson58]

Originally Posted by chollapete

@stormalong & Nicholson57: Thanks for the supplier tip. Do you have a favorite supplier for marine grade electrical wire?

I don’t remember the actual vendor. I found it on a Google search.

[waterman46]

I think you are wise to want an unbroken run of cable from the mast top down to well inside the boat somewhere, which means not using a right angle connector at the mast base. Not knowing the configuration of everything at the mast base, I still have to believe that you could use a little creativity in removing some material somewhere, to allow a greater cable bend radius. If you can do that, then you can use a larger foam dielectric cable for much lower loss. Yes, don't buy that from WM! So much cheaper elsewhere.

[Northbound44]

Originally Posted by chollapete

Photo album: https://imgur.com/a/CHX40Lg



Helping a friend with a project boat. He's getting ready to close the coach (house?) deck so I have to run the wires that are concealed there. The original builder ran the VHF antenna cable under the headliner to the point pictured, where there is a tight radius needed to bend the wires through the deck before entering the deck-stepped mast. Not sure if this is best but it's how it was done.



The whip antenna has a connector much smaller than a PL259. The cable is labeled Network Lab Inc and is RG58C/U.



Thinking of replacing with 213 cable, Metz whip, and 259 connectors. Worried about the radius. Comments?

Cholapette,
I would highly recommend to replace the antenna or at least to check it with a good SWR meter.

[S/V Illusion]

Originally Posted by thunderhoof

PL-259 connectors do not have have a controlled impedance which means they can be somewhat inconsistent in their loss characteristics. At typical marine frequencies this is not a big problem. I would prefer TNC connectors in critical applications. Probably the best cable for this application is Times Microwave LMR-400. It has a solid center conductor so it is not suitable for frequent flex applications but it has the lowest loss in its class.

Do not use right angle connectors or adapters because of their loss issues except for "swept" (curved) components.

Probably more important than all this is to ensure all exposed connections are weathertight on a long term basis. I like heat shrink sleeving with a flexible adhesive inside or an overall coat of silicone adhesive.

To clarify the statements above:

Good quality connectors have negligible insertion loss.

No connectors, good or of less quality, have a 'controlled impedance'.

By "TNC" connectors, you presumably mean BNC.

Again, connectors including right angle connectors have negligible insertion loss.

[Kirok]

Originally Posted by chollapete

@stormalong & Nicholson57: Thanks for the supplier tip. Do you have a favorite supplier for marine grade electrical wire?

I've had good luck with genuinedealz.com for marine wire and connectors.

[Paul Elliott]

Originally Posted by S/V Illusion

By "TNC" connectors, you presumably mean BNC.

He could have meant TNC. These are identical to BNC, but have a threaded shell (the "T"), rather than the bayonet shell (the "B"). I prefer BNC because they are more convenient and seem just as mechanically secure, but my satphone and Class-B AIS GPS (for example) use TNC connectors.

[El Rubio]

I wouldn't get too caught up in the attenuation of the cabling. 8X would be fine at VHF and less than 100'. The convenience of running a smaller cable could make a huge difference. I have suggested LMR240 for VHF runs<100' on this board many times. The attenuation is similar to RG-213, but flexible like 8X. Half or a quarter of your output at the antenna sounds much worse than actual performance over the air. If you had two identical transmitters side by side, one with RG 213, the other with 8x cabling, and a distant receiving station. The person at the distant receiver will not be able to tell the difference between your signals. The difference is insignificant performance-wise. you're really looking closer to around 1dB difference between these cables.



Sometimes, the difference in cost can be significant though. RG-8X runs around 50-70 cents a foot, LMR-240 around 80 cents, RG213 around 90 cents, and LMR400 around $1-1.20 per foot. so, LMR400 could cost you twice as much as 8X, but you're still only looking at $30 difference on a 60' run.



As far as connectors, I would use PL259's because they are common and more durable than some of the others mentioned like BNC or TNC. PL 259's are a bitch to solder if you've never installed several of them. Get crimped on connectors. Not those Shakespeare clamp on things they sell at West Marine, but crimp on. You can buy a cheap crimper on eBay for $25-30. You will make a far superior connector almost every time. Any connectors should be weather sealed with tape at the very least, but better with a self amalgamating tape like butyl or silicone.


Someone mentioned to stay away from LMR400 because it has aluminum conductors, foam dielectric, etc. That's not entirely true 400 has a copper clad aluminum center conductor, aluminum foil on the outer dielectric and a tinned copper braid over that. The foam doesn't "wick" moisture either. It's no less susceptible to water intrusion than any other cable. Water in any cable will wick up the braid and corrode quickly. That is why all exposed connectors should be sealed. Buy good connectors and protect them no matter what cable you use.

[chollapete]

@El Rubio: Thanks for the super-quality post. I'm def thinking about what you said.

[chollapete]

@El Rubio (or anyone else): About the crimp tool, I'm a little confused by what tool is correct for what connector. As an electrician, I know that the correct crimp die is determined by the lug being used; i.e., Burndy or Ilsco lugs tell you the color- and number-coded die to use. For battery cables, certain hex crimp tools seem to work with particular brand of lugs.

I've actually run LMR400 at work when a customer needed to bring GPS signals into the interior of an office building. We had a little, "special" hex crimper sent out from the shop just for that. Do you think that crimper would work for PL259s? Thinking about it now, I wouldn't be surprised if we actually were using PL259s on that job. Thanks. I'm going to check out that crimper, as i believe that my boss never sent it back to the shop.

Any thoughts or advice is welcome!