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Old 17-03-2013, 05:51   #16
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Re: RG213U- a practical alternative?

What do you guys think about this cable:

http://www.gigatronix.co.uk/pdfdatas..._datasheet.pdf

It's RG213, with tinned copper stranded inner conductor. The outer braid, however, is copper clad aluminum. Carp? Or not?

The same company has RG214, with silver plated copper conductor and two silver plated copper outer braids. This looks really nice, but the expensive is absolutely massive (345 pounds plus VAT for a 100 meter drum, which is the only way it comes), and the attenuation is actually worse than the RG213. Gigatronix - Coaxial Connectors, Coaxial Cables Assemblies, Coaxial Cable

I'm not sure whether the silver is worthwhile for marine purposes or not -- silver is fairly prone to corrosion.

Any views on this?
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Old 17-03-2013, 09:50   #17
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Re: RG213U- a practical alternative?

Quote:
Originally Posted by Dockhead View Post
I'm not sure whether the silver is worthwhile for marine purposes or not -- silver is fairly prone to corrosion.
I think silver is probably overkill here, but silver oxide (tarnish) is still quite conductive. Silver plating is used in microwave filters and other critical-performance components for just this reason.
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Old 17-03-2013, 11:46   #18
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Re: RG213U- a practical alternative?

Quote:
Originally Posted by Dockhead View Post
Wow, what kind of antennae do you have to need FIVE runs of RG214?!
2 cables goes to an RR Electronic Pacific multi-antenna that provides
- VHF for secondary /cockpit VHF
- SSB-Rx
- TV
- FM/AM radio
- 900 MHz cellular for cell-repeater
- 450 Mhz long-range CDMA cellular diversity antenna
- Navtex
- Weatherfax
Antennen Konfigurator

1 cable goes to the main VHF/DSC, an AC-marine CX4 dipole
1 cable goes to a VHF/900 MHz AC-marine Cel-twin antenna for the AIS and fixed-mount 8W GSM phone
1 cable goes to a 450 MHz colinar from AC-marine, for long-range CDMA cellular RX/TX

4 antenna mounts are placed on outriggers like a + so they get apprx 80cm separation which works fine.

/Marcus
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Old 17-03-2013, 11:47   #19
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Re: RG213U- a practical alternative?

"Inside the boat it's not so critical "
Every wire in a boat is subject to thermal cycling. Heats up during the day, any air under the insulation expands. Cools down at night, exterior damp air is sucked in and brings moisture with it. So I'd argue for all tinned, all the time, for coax, braid, and anything outside of bus bars or other heavy solids.

Every coax has a problem. Either it is too expensive, or it is out of stock. Or it has a foam dielectric which will collapse when clamped, so it can't be run vertically without changing the impedance and sagging. Or it isn't tinned, or it has too much loss, or it is too thick.

"Best" is still a choice to be made based on what's affordable, will suffice to meet the demands you place on it, and how often you want to replace it. Once you spec a few (like how much loss you'll tolerate and what frequency you will be using) the rest comes down to your wallet, doesn't it?
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Old 17-03-2013, 11:50   #20
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Re: RG213U- a practical alternative?

Quote:
Originally Posted by Shipraiser View Post
2 cables goes to an RR Electronic Pacific multi-antenna that provides
- VHF for secondary /cockpit VHF
- SSB-Rx
- TV
- FM/AM radio
- 900 MHz cellular for cell-repeater
- 450 Mhz long-range CDMA cellular diversity antenna
- Navtex
- Weatherfax
Antennen Konfigurator

1 cable goes to the main VHF/DSC, an AC-marine CX4 dipole
1 cable goes to a VHF/900 MHz AC-marine Cel-twin antenna for the AIS and fixed-mount 8W GSM phone
1 cable goes to a 450 MHz colinar from AC-marine, for long-range CDMA cellular RX/TX

4 antenna mounts are placed on outriggers like a + so they get apprx 80cm separation which works fine.

/Marcus
Wow, and I thought I had antenna proliferation!! Respect!

Where did you get that 8W fixed GSM phone? That sounds like quite a goody. Never heard of such a thing.
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Old 17-03-2013, 12:07   #21
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Re: RG213U- a practical alternative?

Thanks for all the great replies. Two respondants mentioned RG8x and RG142 cable. How do these differ from RG213U and RG8U? Also, if I opted for a heavier, thicker diameter cable ie; RG213U .410 diameter,how would you handle the extra weight aloft and the probable movement inside the mast which might theoretically give the Bells of St. Mary a run for their money? Is the thicker diameter cable RG213U overkill? The mast is 48 feet and the cabling from the ceiling to the radio is about 10 feet. All thoughts would be appreciated.
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Old 17-03-2013, 12:16   #22
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Re: RG213U- a practical alternative?

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Wow, and I thought I had antenna proliferation!! Respect!

Where did you get that 8W fixed GSM phone? That sounds like quite a goody. Never heard of such a thing.
I have worked with antennas for a large part of my professional life so let's say it's an occupational hazard...

The 8W phones were made in the 1990s as fixed install car phones. Search in the scrap sales or check ebay for the Motorola International range, models 1000, 2500, 3200 etc. Sometimes a nice one is sold with all cabling for 20-50 EUR.

motorola international 2500 vintage mobile phone | eBay
Motorola International 1000 connection | Flickr - Photo Sharing!
Автотелефон. Telekom D1-324


/Marcus
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Old 17-03-2013, 14:14   #23
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Re: RG213U- a practical alternative?

" the probable movement inside the mast "
No no no. If your cable is slapping around, it was not properly secured, and the simple weight of the cable pulling down unsupported WILL compress the jacket, compress the dielectric, ruin the cable in a few short years. You don't just drop a cable, you support it or tie it off every so many feet, to take the strain off of it.
If you're just going to drop it through, then buy something cheap and it won't hurt so much when the SWR shifts and you throw out the cable.

Marcus-
"The 8W phones were made in the 1990s as fixed install car phones"
IIRC in the US the car phones were never 8W they were capped at 3W, and that was for analog phones only. Analog phone service in the US jumped to about a buck a minute five years ago, when digital was dropping to pennies, and most carriers shut down their analog accounts completely.
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Old 17-03-2013, 14:25   #24
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Re: RG213U- a practical alternative?

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Originally Posted by hellosailor View Post
You don't just drop a cable, you support it or tie it off every so many feet, to take the strain off of it.
If you're just going to drop it through, then buy something cheap and it won't hurt so much when the SWR shifts and you throw out the cable.
??? How do you do that? No place to tie off in the middle of the mast that I have ever seen.
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Old 17-03-2013, 14:43   #25
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Re: RG213U- a practical alternative?

Given the limited choices and lack of a wire chase? Probably the best way is to borrow a page from the telcos. Run a stainless cable (which these days could be a non-stretch high tech halyard line instead) parallel to the coax, and tie the coax off to that. Let the cable take the strain instead of letting the coax stretch itself out. I've never seen solutions documented to this, except "replace cable every so often as it ages".
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Old 17-03-2013, 14:44   #26
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Re: RG213U- a practical alternative?

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"The 8W phones were made in the 1990s as fixed install car phones"
IIRC in the US the car phones were never 8W they were capped at 3W, and that was for analog phones only.
All the phones I mentioned are GSM900 only, suitable for European use, since both me and Dockhead who asked the question is in Europe.

The swap to GSM was made already in 1991-1996 in Europe and GSM was never made to be compatible with the old analog systems, which was both a blessing and a curse. We could not make dual-mode phones, but we had a faster switch to a modern system without having to care about backwards compatibility. GSM wasn't big in the US until AT&T replaced AMPS & D-AMPS with GSM & WCDMA 2002-2008.

Regarding analog, I used the same Motorola car phone from 1986 to 2007, analog NMT on 450 Mhz. It could put out 15W, and the range over sea was fantastic, I have used it 40NM out from the coast. I kept it in the boat the last years until they shut down the network.

But now we are terribly off-topic...

/Marcus
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Old 17-03-2013, 14:55   #27
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Re: RG213U- a practical alternative?

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??? How do you do that? No place to tie off in the middle of the mast that I have ever seen.
If You don't have a conduit from factory like most modern masts you could make one. Take a few lengths of electrical PVC pipe (25 or 32mm or what fits) and join them together to the right length. Temporarily replace halyards with cheap thin ropes. Have a few people help in the next step. Insert the full length of conduit while applying plenty of a marine-grade Construction Adhesive (I like Bostik Simson CA). The mast should be positioned so that gravity helps the conduit to settle inside the mast. Let cure overnight, and now you have a conduit to pull cables inside, and no banging in the mast.

Re-install your halyards. Don't want them smeared with CA.

/Marcus
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Old 17-03-2013, 14:58   #28
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Re: RG213U- a practical alternative?

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The same company has RG214, with silver plated copper conductor and two silver plated copper outer braids. This looks really nice, but the expensive is absolutely massive (345 pounds plus VAT for a 100 meter drum, which is the only way it comes),
They seem to sell by the meter also?

Yes, it's expensive, but it does the job well. How much time and money are you spending to replace cables? I've taken out cables not even 5 years old that were completely oxidized.

/Marcus
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Old 17-03-2013, 16:16   #29
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Coax choice for VHF masthead antennas

First off I must disclose that I have a great deal of experience with coaxial cable for RF applications (HF, VHF, UHF, SHF/microwave), and that most cruising sailboats can make compromises from the "ideal" set-up, and not have any issues....
But, every db lost is a db lost....so if you can pick up a db or two, by spending an extra $20 or so, that is always a good recommendation!!!


1) Generically, for most marine installations, the basic criteria are (in order of importance):
a) cable longevity, resistance to moisture ingress/intrusion...
b) abrasion resistance / UV resistance...
c) cable loss/attenuation...
d) ease of proper installation / ability to ensure proper cable installation (will the cables fit in the space you have??)...
e) ease of connection and waterproofing those connections...
f) cost....(I placed cost last, as the lengths generally used do not usually allow significant cost savings if considering a "bargain" cable, etc....so usually spending the extra $5 or $10 for a high quality cable isn't a big issue...)



---- Considerations for a and b...
If the connections are properly made and waterproofed (self-vulcanizing tape, over heat-shrink-tubing, have been my fav for years, but even a few tightly wrapped layers good 'ole 3M electrical tape, will work surprisingly well for years in the UV/salt air environment, or a few wraps of silicone "rescue tape" over the 3M tape...), in most marine applications the moisture issue is usually a moot point....
And as long as you install the cable correctly (supported along its length, drip loops, no tight bends, etc.), there are few abrasion issues to worry about....
BUT...

But, if you wish for added abrasion resistance, you could consider PE (or rubber) jacketed cables rather than the normal PVC jacket....
And, for further protection from "moisture ingress" issues (although I've never seen the need), you could consider "flooded" cables (these have a sticky / goo'ey liquid applied inside the cable when it is manufactured, that eliminates water from wicking its way thru the cable, should it become cut/sliced-open and moisture/water is present)....




---- So, now onto c and d....
Coaxial cable loss/attenuation is basically determined by the cable's size and dielectric (inner insulation)....
While some may try to simply and say "bigger is better", that is NOT always the case, as high vel. factor dielectric cables of smaller sizes can have as low of loss (or VERY close) as larger, lower vel-factor dielectric cables....
[Ex. is LMR-240 vs. RG-213/RG-214.....where the 213/214 loss per 100' (@150mhz) is only 0.2db lower than that of the LMR-240...]

If you look at cable loss/attenuation data...
Coaxial Cable Attenuation Chart
Coax Attenuation Chart
Welcome to Times Microwave | Coaxial Cable - Attenuation & Power Handling Calculator

If you have limited space in your mast conduit(s), as I do, you may wish to go with a lower-loss, hi-eff (high vel-factor) smaller diameter cable (such as LMR-240) and have the same loss as the larger cable....
Using this approach, does require attention to waterproofing of connections, as the higher-vel-factor dielectrics are more prone to moisture wicking (although I've never had issues with it, you should be aware that more care should be taken here..)
Also, caution should be used to maintain proper bending radii, and proper support for the cable as the smaller cable is slightly more sensitive to rough handling, etc...

(take note that there are TWO variations of RG-214....one has double-silver-plated copper shields, and one has double-tinned copper shields....in my profession, I use the silver-plated cables, but for on-board use, I would use the double-tinned shielded cables....}

If considering other low-loss cables (such as "Bury-flex", LMR cables, etc.) be sure to understand the differences in their center-conductors and dielectrics...you can give up one or two tenths of a db in loss, by going with stranded center-cond, etc. (Burt-Flex and "UF", etc.) and have a much easier cable to work with, vs. the solid center-cond cables, especially those with copper-covered aluminum center conductors (such as "regular" LMR-400)....






2) Specifically on this question / issue....
Quote:
Originally Posted by rognvald View Post
I read that RG213U would be the best antenna wire for my VHF. However, when I read the specs, the cable is 3/8" in diameter which is quite sizeable next to the RG8U Foam core and would not only be considerable weight aloft, but could be a real "bellringer" inside the mast. Which will provide the best all around performance based upon these practical considerations? Are there any other considerations I have overlooked? Also, is there a premium brand for terminal connections at the radio/antenna ends? All "techy" responses will be greatly appreciated.
a) First, you should have all the cables (especially coaxial/signal cables) supported properly, so there would be NO "bellringing" inside your mast!!!

b) If you could fit a 0.405" cable in the mast / mast conduit, I'd recommend my favorites..... "Davis RF Bury-Flex" or "LMR-400UF"....
There is no real issue with "weight aloft" between these larger cables vs. the standard RG-8x....so not worry about that!!

c) If you cannot fit the larger cable, then I'd recommend "LMR-240".....

d) You can source any of the above cable and the proper connectors from Davis RF....
And, if you desire, Davis will pre-assemble the cables/connectors for you....either on both ends or just one end....
I've been doing business with them for years (15-20 years), they are great guys.....(no connection to them, except as a longtime customer...)
Davis RF Co. - Coax Cables
Davis RF Co. - Bury-FLEX Flexible Low-Loss Coax




3) Lastly, a generic piece of advice....
Do NOT look for internet bargains for coax....you can buy goo, high-quality coax from Davis, Tessco, etc. and get excellent prices....
Most no-name / discount coax, is of suspect quality and I'd not recommend trying to save a few dollars....




I hope this helps clear up the confusion...

John
s/v Annie Laurie
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Old 17-03-2013, 16:30   #30
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Re: RG213U- a practical alternative?

John, wasn't it Alan Greenspan who said "A decibel here, a decibel there, and pretty soon you're talking real money." ?

As best I can figure it out, if my signal is just one db stronger than the next guy, my signal is the one that will capture the receiver I'm trying to talk to, and his won't. Doesn't really matter how fine the difference is, but without becoming a fanatic this is a case where "more power" always beats less.
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