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chollapete · 29-09-2018, 14:41

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?

S/V Illusion · 29-09-2018, 15:07

Difficult to provide a reliable answer as we have no clue what you refer to as a "tight radius". It's possible to compromise the dielectric spacing with RG213 depending on how "tight" the turn is but if you are worried about it, use LMR 200 or equivalent and check the bending specs on the cable manufacturer's web site.

**GordMay** · 30-09-2018, 05:07

PL259 connectors come in a 90 Deg version. Perhaps yours do, as well.

CarstenWL · 30-09-2018, 05:11

Quote:

Thinking of replacing with 213 cable, .... Worried about the radius. Comments?

Most (if not all) RG-213 cables are specified to need 10cm (4") radius (for a 'one-time bend'), around 15cm if bended more than once.

Regards,

Carsten

chollapete · 30-09-2018, 06:37

@Carsten: Thanks. I had also found 5x cable diameter as a rough guide for coax. I think I'll be going with RG-8X, as I believe it is stranded and somewhere I saw it specec'ed for 1/2 inch bends--but 1-1/4 inch will be sufficient.

Could you or anyone else identify the antenna socket? I found reference to a "mini-UHF" plug. Again, this is an unlabeled antenna, but if it came as a kit with the cable, it would be Network Lab Inc., which has a website.

My friend's budget seems tight, so I'd rather keep the existing whip and find the correct connector. This isn't my area of knowledge.

PS. On second thought, I'll just order a mini-UHF connector and see if it fits. They're easy to find online. Sorry to seem so needy. Lol.

CarstenWL · 30-09-2018, 07:39

@collapete:

RG8X or any cable with a tinned / silvered outer jacket would be my preference too.

Can you post a picture "how the connection looks inside the antenna"?
Could it be a FME connector? (https://tinyurl.com/y8h6mlcl)

Regards,

Carsten

Nicholson58 · 30-09-2018, 07:49

You should use the low impedance cable, particularly for a long run.

CarstenWL · 30-09-2018, 07:53

Quote:

You should use the low impedance cable, particularly for a long run.

You should use 52 Ohm impedance cable (might qualify as low impedance ;-)) ...
You should use low loss cable, especially for a long run ...

:-)

Carsten

Nicholson58 · 30-09-2018, 08:20

Quote:

Originally Posted by CarstenWL

You should use 52 Ohm impedance cable (might qualify as low impedance ;-)) ...
You should use low loss cable, especially for a long run ...

:-)

Carsten

Yes.

AIS especially suffers on high impedance cable.

chollapete · 30-09-2018, 08:48

Quote:

Originally Posted by Nicholson58

You should use the low impedance cable, particularly for a long run.

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.

ohgary · 30-09-2018, 08:53

Quote:

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.

...

If you need a tigher turn radius then LMR400 has a 1 inch turn radius.
RG8x has about twice the loss over lrm400 or rg213. Avoid id it you can.

W3GAC · 30-09-2018, 10:39

Spent my career in telecommunications working with coax of all sizes/ types and a ham and sailer for 40+ yrs... if you use right angle RG-259/8 adapters make sure you tighten with plyers, paint with liquid tape, and use ‘outdoor/ weather resistant heat shrink material (has sticky goo inside). This is especially true when such adapters are going into inaccessible areas in marine environments. If at all possible, avoid the hidden adapters and adhere to the recommended coax radius spec. Consider that coax installation a ‘safety of life’ install where someone’s life may depend on choices made & workmanship.

stormalong · 30-09-2018, 10:48

Quote:

Originally Posted by ohgary

If you need a tigher turn radius then LMR400 has a 1 inch turn radius.
RG8x has about twice the loss over lrm400 or rg213. Avoid id it you can.

LMR400 is a foam dielectric and has a bend radius far greater than one inch. It also has a solid, copper plated aluminum center conductor that will cut through the foam core and short to the shield if bent too tight.

RG213 has a stranded copper core and a solid core that is far more resistant to shorting when bent. There is marine grade RG213 cable available that is tinned.

The DB signal loss translates to a reduction of signal strength of 50% for every 3 db. IOW a three db loss means that half the signal strength received at the antenna is lost.

thunderhoof · 30-09-2018, 10:52

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.