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Old 17-03-2013, 16:45   #31
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I would not get too hung up on losses to the antenna as a result of cable choice, I'd pay far more attention to proper connection assembly sealing and strain relief etc. most problems I've discovered with my VSWR meter have been connector related.

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Old 17-03-2013, 17:31   #32
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Re: RG213U- a practical alternative?

dockhead-
Closed Mesh, Single Eye, Single Weave Grip on Remke Industries, Inc.?
This is one of the support gizmos available, although at that price you may understand why folks would either tie off, use multiple zipties, or just let it hang.
Essentially a chinese finger trap with a loop to hang it from, and of course you have to feed the damned cable all the way through it. There are other options that use lacing, etc. but I have no idea if anyone, even the USN, is real religious about using any of them.
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Old 17-03-2013, 17:36   #33
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Re: RG213U- a practical alternative?

1) I think this must've been a typo on the poster's part, as RG-142 is an expensive and small diameter (0.150"), double-shielded, precision-made cable (w/ low-vel-factor Teflon dielectric), designed for use in fairly short lengths (and/or where loss can be tolerated), for high-isolation uhf/shf use...and is NOT a low-loss cable, nor is it particularly well suited for our applications....
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Originally Posted by rognvald View Post
Thanks for all the great replies. Two respondants mentioned RG8x and RG142 cable. How do these differ from RG213U and RG8U?
I suspect that the poster meant to type RG-214.....

RG-214 has the same loss specs as RG-213.....the only differences are 214 is slightly larger in diameter (0.425"), slightly stiffer and harder to bend, and has significantly higher ingress/egress isolation....(typically 100-110db+ vs. 80-90db)
Either 213 or 214 are good cables and will suit your application well....
(If the choice was just between these two, I'd go for the 214 "tinned-shields".....but I doubt you'd ever notice any difference at all....)







2) See my post above for the detailed answers to these questions...


a) But, here I think we may have a unanimous and non-technical answer for you....
Quote:
Originally Posted by rognvald View Post
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?
No matter what coaxial cable you use in the mast, you must secure the cable properly....use of a cable conduit / cable race / etc. is best....but cable clamps / cable ties, spaced appropriately is also acceptable.....
So, whether small cable or thick cable, it needs to be secured....but, ironically the smaller cable is in MORE need of proper support/securing than the thicker cable, as it has less overall strength....






b) Only you can decide how much a couple extra db matter to you....and how much spending an extra $20 or so would be a hardship for you....so, I cannot answer this for you....But..
Quote:
Originally Posted by rognvald View Post
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.
But, if you desire my advice (based on 40 some years, of both radio communications experience, and offshore sailing experience), gaining ONE extra db (actually 1.1db of gain, comparing 60' of RG-8x would be about 2.8db loss @150mhz, vs. 1.7db for 60' of RG-213 @150mhz) is unlikely to gain you any significant measureable range....BUT....
But, my recommendation IS to go for the lower loss cable, always!!!!

And, if you can afford an extra $50, then I'd go further and recommend either Davis Bury-Flex or Times LMR-400UF.....where you'd have only about 1db of loss for 60' of cable @150mhz....gaining a full 1.8db vs. RG-8x.....and that IS measurable / noticeable.....




3) Again, see my post above for more details and links...


Fair winds...

John
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Old 17-03-2013, 17:43   #34
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Re: RG213U- a practical alternative?

I agree here with Dave....
Quote:
Originally Posted by goboatingnow View Post
I would not get too hung up on losses to the antenna as a result of cable choice, I'd pay far more attention to proper connection assembly sealing and strain relief etc. most problems I've discovered with my VSWR meter have been connector related.
But, once you've taken care of the "connector/connection" issues and waterproofing issues, spending an extra $50 on lower loss cable (gaining you a couple db), in MY opinion, is a good choice.....

Just my 2 cents...

John
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Old 17-03-2013, 17:50   #35
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Quote:
Originally Posted by ka4wja View Post
I agree here with Dave....

But, once you've taken care of the "connector/connection" issues and waterproofing issues, spending an extra $50 on lower loss cable (gaining you a couple db), in MY opinion, is a good choice.....

Just my 2 cents...

John
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Yes but people here are debating 0.2 to 0.5 dbs , that's rather funny in real life. Given the installation is a boat , over time corrosion, moisture, vibration, will cause losses well above the basic cables not to mention losses due to reflected power.


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Old 17-03-2013, 18:06   #36
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Re: RG213U- a practical alternative?

Yeah, more ERP (effective radiated power) is always better than less....but don't forget that antenna system gain (less coax loss is effectively antenna system gain) helps receive as well....



In actuality, depending on the pre-emphasis and receiver bandwidth the capture ratio for nbfm is about 5 - 6db....
Quote:
Originally Posted by hellosailor View Post
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.
....but, yeah a db here and a db there does add up to "real" numbers...


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