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Old 29-09-2020, 07:41   #1
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Coax cable for long run up mast

I'm currently painting the wooden mast on my 1959 Stonington Motorsailer, and I thought it would be a good time to run my antenna up the main (it's on the mizzen right now).

The run from the deck to the top of the mast is about 35 feet, so I'm thinking a 50-foot cable will get to the cockpit where I'd like to re-locate my VHF (currently in the aft cabin, making it a pain in the ass to use when single-handing).

As I read about cable types, connections, etc. I feel like I need a degree in electrical engineering to make a good decision on hardware. Can anyone give me a recommendation or link to an affordable, durable 50-foot antenna cable that will function well with minimal power loss? Any advice from someone smarter than myself would be greatly appreciated!

The radio is a typical 25-watt fixed mount.
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Old 29-09-2020, 07:57   #2
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Re: Coax cable for long run up mast

My vote would be for lmr240uf or lmr400uf

I’ve had good luck ordering from MPD digital
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Old 29-09-2020, 08:19   #3
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Re: Coax cable for long run up mast

LMR is very good able but it is overkill for your purpose. The first question is are you OK with a .4 inch diameter cable? If yes I suggest marine grade RG-213. Davis RF is where I bought mine. The marine grade is tinned copper conductors with a white covering. It is about half the price of LMR400UF.

PS. Out of curiosity I just called Davis RF. Their price is $1.03 per foot and they have a total of 50 feet in stock.
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Old 29-09-2020, 10:37   #4
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Re: Coax cable for long run up mast

Thanks guys! $1.03 a foot is great. I'll give them a call when I get off work.

I was planning on running the cable along the front of the mast, as my channel for cables is full, so white is perfect as long as it can handle UV.

I assume I'll have to put my own ends on it... Any recommendation for that? Something that a novice can't screw up?

Thanks again!

-Arthur
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Old 29-09-2020, 10:53   #5
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Re: Coax cable for long run up mast

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Originally Posted by stormalong View Post
LMR is very good able but it is overkill for your purpose. The first question is are you OK with a .4 inch diameter cable? If yes I suggest marine grade RG-213. Davis RF is where I bought mine. The marine grade is tinned copper conductors with a white covering. It is about half the price of LMR400UF.

PS. Out of curiosity I just called Davis RF. Their price is $1.03 per foot and they have a total of 50 feet in stock.
LMR is total overkill (and has a foam, not solid insulator, vulnerable to crushing and water intruction -- do not use on a boat). RG-213 is overkill too (I admit that I have RG-214, but my mast is 75 feet, not 50). For that I would use RG-58 which is far easier to install, takes up less space, is more flexible. The losses in a 50 foot run of coax are not important -- your VHF has 25 watts which is intentional overkill to make up for these losses. Vastly more important is a good antenna, and most important of all -- really well installed connectors. Forget the couple dB from the thinner cable; it's not material.

If you use this loss calculator -- https://www.qsl.net/co8tw/Coax_Calculator.htm -- RG-58 loses 2.9dB over 60 feet, whereas RG-213 loses 1.62dB, at marine VHF frequences. So we're talking about -- drum roll -- 1.3dB. Big whoop. You can claw that back by eliminating one pair of connectors at the base of the mast.

To prove how much overkill even my installation is --

I had a "weak but readable" signal report from 60 miles. USING 1 WATT TRANSMISSION POWER. With an Icom M604 set. I use 1 watt most of the time, and rx sensitivity is so annoying that I normally have the attenuator on.

So if I had to do it over again, I would use RG-58. I can sure spare a few dB.
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Old 29-09-2020, 11:06   #6
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Re: Coax cable for long run up mast

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Originally Posted by Algallop View Post
. . . I assume I'll have to put my own ends on it... Any recommendation for that? Something that a novice can't screw up?. . .

I would hire a pro for this.


Otherwise learn how to solder them on. It's something of an art, and be prepared to redo it multiple times until you get it right.


Use top quality connectors -- Amphenol or similar. You'll need a whole bag of them, so this can get expensive. You'll also need a soldering iron other than a typical consumer type, because you have quite a mass of metal to heat up with those.



I do have this skill, but I actually prefer the crimped ones. Much less risk of screwing it up. I ended up buying crimpers, but this is not economical for just one installation -- hiring the pro will be cheaper and less trouble.


Don't forget that PL-259/SO-239 connectors are NOT waterproof. So if you're running the cable outside, make sure you either get the top connector out of the weather, or do a "telecomm wrap" on it, carefully, to be sure rain doesn't get into it. A Type N connector is better -- if you have a choice.


I have a Shakespeare Little Galaxy antenna (internal dipole with no grounding on the mast). It has a pigtail connector. I chopped off the PL-259 and soldered on a Type N plug, then for good measure did a good telecomm wrap on that, and hid the connector inside the mast (with proper strain relief).



I can recommend the antenna.
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Old 29-09-2020, 12:30   #7
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Re: Coax cable for long run up mast

Davis RF will sell you Amphenol silver plated PL-259s. Per piece, no need to buy a bag of them. That is my connector of choice.

There are dozens of youtube videos on how to install them. One advantage of the Ampfhenols over the cheap ones it that the insulator in the connector won't melt unless you heat is with a blowtorch. They can be re-used too so a bad install won't mean scrapping the connector.

Yes, PL-259s are not waterproof and need to be properly sealed. There is a product called coax seal that is basically butyl rubber tape. It goes on easy but is a real PITA to take off. I wrap the connection with electrical tape with the sticky side out and then apply coax seal over that. Doing it that way you can seal it really well without the removal problem.
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Old 29-09-2020, 12:40   #8
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Re: Coax cable for long run up mast

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- RG-58 loses 2.9dB ... So we're talking about -- drum roll -- 1.3dB. Big whoop. You can claw that back by eliminating one pair of connectors...

.

Very misleading....


That’s roughly 20% of power. That can be a “big whoop” under marginal conditions.

Also, connectors if properly installed have no inherent loss.
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Old 29-09-2020, 12:46   #9
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Re: Coax cable for long run up mast

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Very misleading....

That’s roughly 20% of power. That can be a “big whoop” under marginal conditions.

Also, connectors if properly installed have no inherent loss.

When 1 or 2 or even 5 watts is fundamentally enough, losing 20% out of 25 watts is -- no big whoop. Really.
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Old 29-09-2020, 12:48   #10
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Re: Coax cable for long run up mast

Thanks, Dockhead. Based on your recommendations, I think I'm going to look for a 50 ft length of RG-58 with pre crimped or soldered connectors.

If I can get 30 miles of range and 5-10 years of trouble-free use, I'll be delighted.
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Old 29-09-2020, 12:50   #11
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Re: Coax cable for long run up mast

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Originally Posted by Algallop View Post
Thanks, Dockhead. Based on your recommendations, I think I'm going to look for a 50 ft length of RG-58 with pre crimped or soldered connectors.

If I can get 30 miles of range and 5-10 years of trouble-free use, I'll be delighted.

You should get more range and more years that than. Good luck!


Range depending very much on the height of the other antenna -- keep that in mind.
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Old 29-09-2020, 12:52   #12
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Re: Coax cable for long run up mast

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When 1 or 2 or even 5 watts is fundamentally enough, losing 20% out of 25 watts is -- no big whoop. Really.
First, a 25 w radio doesn’t radiate 25 w at the antenna. Second, sometimes, 25 w isn’t “enough”. More important than 1or 2, it’s 20% or more of the signal lost as coax loss and saying its “only 1.5 dB” can be misleading to some people like the OP who admittedly doesn’t understand.

We’re here to be helpful , not mislead.
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Old 29-09-2020, 13:32   #13
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Re: Coax cable for long run up mast

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Originally Posted by S/V Illusion View Post
First, a 25 w radio doesn’t radiate 25 w at the antenna. Second, sometimes, 25 w isn’t “enough”. More important than 1or 2, it’s 20% or more of the signal lost as coax loss and saying its “only 1.5 dB” can be misleading to some people like the OP who admittedly doesn’t understand.

We’re here to be helpful , not mislead.

OK, then -- so how much will it radiate at the antenna? And how much is actually needed? How much is "enough"?


Don't get me wrong -- I do have RG214 in my own installation. I took the trouble to pull that awful thick cable through my 75 foot mast. But in my case -- it is clearly overkill. From experience. I think a watt or two at the antenna is enough.
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Old 29-09-2020, 13:58   #14
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Re: Coax cable for long run up mast

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OK, then -- so how much will it radiate at the antenna? And how much is actually needed? How much is "enough"?


.
It’s your premise which is wrong - there is no such thing as “enough” under varying circumstances, conditions, distances, etc... it will always be a difference answer.

“Enough” is whatever is necessary to ensure effective communications. There is virtually no value in cheap coax which your’re only going to buy once but could limit ERP and increase loss such that you won’t hear someone’s mayday or they won’t hear yours.
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Old 29-09-2020, 14:10   #15
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Re: Coax cable for long run up mast

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OK, then -- so how much will it radiate at the antenna? And how much is actually needed? How much is "enough"?


Don't get me wrong -- I do have RG214 in my own installation. I took the trouble to pull that awful thick cable through my 75 foot mast. But in my case -- it is clearly overkill. From experience. I think a watt or two at the antenna is enough.
25 watts in ideal conditions is more than good enough to close a link to a receiving radio (for decent reception) at 10 miles, which is close to the LOS range at 60 feet elevation.

Antenna gain of 3dB on either transmit and receive end is the norm for sail with their leaning mast angles, as is vertical polarization (for everyone on marine VHF). Loosing 5 watts of VHF transmit power is a big deal in the case of antennas transmitting or receiving out of local vertical. Cross - polarization gain is close to 0 dB. So canted 45 deg one way while the other antenna is the other way can cause fading, as can sea water reflection nulls and wave induced interference.

In addition to the transmit power loss, their is a similar effect on receive power. On the Chesapeake, I like to talk to my friends until they start breaking up. Taking 20% out of the receiver's front end input signal can typically result in hearing completely what is said to having it repeated a couple of times due to system noise competing with the input signal.

Its also informative to hear boats at distance work marina channels which allows you to hear about bouys out of place, marina slips, phone numbers and the like.

A 0.5dB additional loss is not a big deal at 25w, but 1.5 dB is too much really.

Reflect what happens with AIS Class B systems added to an existing VHF cable between the VHF two way radio and the antenna. The AIS splitter allows the AIS to connect to the radio antenna, simplifying installation big time. But note all the folks talking about reduced VHF receive performance as the AIS splitter took half the received power and routed it to the AIS receiver front end (a 3dB loss). That power is lost to the VHF. And the AIS receiver didn't decode it either. That is why a dedicated AIS class A or B antenna is best. You need to get that 3dB back.
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