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Coax


KD3Y
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I have a problem to solve: Yes
Problem types: Antenna

Maybe this post will go thru.  The last one posted Thursday morning disappeared in the "Needs moderator approval" shredder.

So rather than waste 15 minutes typing out a detailed, well explained paragraph, since it probably won't post this time either, I'll just cut to the chase.

Can I use RG-213 for my radio to antenna run, about 75 feet, for UHF & VHF, or will LMR400 offer me something that RG-213 can't?

Edited by KT4OBX
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ELMER

First a sort of apology and explanation 😇 We had created this Q&A section as a kind of escalation forum for questions that fit nowhere else and were 'tough' to answer. I'm seeing that it's more of a PITA than anything else. After I finish answering your question, I'll nuke the moderation and when I do come down to visit, the first three beers are on me 🍺🍺🍺

Now for the answer. One important piece of information missing... (which I am sure was in the longer lost version...) is the length. If it's a short run, say ten feet, then it's a non issue, either is fine. If it's longer, and especially when you get to UHF, then it matters. The RG213 has about 2.2 db loss for 100ft at 100 MHz and more than doubles at 400 MHz to 4.8 db loss. God forbid you go to 1000 MHz and then you're talking 8.2 DB loss. By and large, LMR 400 is about half that. So if you're talking about, in my books, over 50 feet, the LMR will make a definite difference, especially if you're only running 50W on VHF and 25W on UHF. If you're running amps up to legal power, then you'll feel less pain, of course.

Also, the LMR400 has a solid core conductor with a double shield whereas the RG213 has a stranded core with a single shield, hence both the additional signal loss but also the ruggedness. The LMR400 will live longer.

Last point: 90% of my cables are LMR-400 (the rest is a combo of 600 and 900). In the case of the LMR400, I love the Ultraflex... nice and easy to route.

Again, sorry for the moderation and just don't ask for some beer I have to import from the Belgian Congo.

PS. Moderation fixed... I hope.

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Thank you Sir.

My "longer version" had the details.  But if what I've learned about coax is true (and correct me if it isn't)  I had settled on LMR-400 but after watching some youtube videos on "which cable to use" and such, I was swayed to RG-213 by "the experts".   That's just how it is when you don't know what you don't know.

From what I understand,

RG-58 is high loss in VHF & UHF, used mainly for runs less than 50 feet in frequencies above 100 Mhz and less than 50 feet for frequencies above 400 Mhz, often used for mobile radio installations in a vehicle.  Readily available, cheap, but high loss.  OK for short runs, such as mobile installations is vehicles but it's high loss in long runs.

RG-8X is better than RG-58, Works well for 50 - 75 foot runs in UHF & VHF but still lossy.  Medium price range. But quality varies with manufacturer.

RG-8U was the military spec 52 ohm, better than RG-8X due to the larger diameter center conductor and suitable for 50-75 foot runs in the UHF & VHF frequencies.

RG-213 replaced the mil spec RG-8U and has lower loss and better UV protection than the RG-8 family (which is why I considered it since half my run will be outside in the sun. 

LMR-400 is the best, very low loss and suitable for the Ghz range.  Since I'm only using VHF and UHF right now, my man question was, am I wasting money on LMR for performance I'm not going to use when RG-213 will do the same thing.   Not trying to be a cheap ass, I just don't see the need for paying extra for capabilities I'll probably never use.

My run will be about 75 feet.  Through the floor, across the crawlspace, through the foundation block, then 20 feet up the mast.  Probably half that will be outside in the sun and salt air.   If LMR-400 is what I need, then I don't mind spending the extra 30 bucks.   I think I can rule out RG-58 obviously, and RG-8X, and probably RG-8U.  So I was in a toss up over RG-213 or LMR-400.  I also was concerned though I'm simply VHF and UHF now, I probably will go to HF in the future, and didn't want to have to re-run cable again in a year unless I had to.

On a less bothersome note, for any interested, I updated my website last night and added my morse code practice key HERE.  I still get an error when the user keys in some dot/dash combo that doesn't exist in morse code.  I can't determine if it's my script that's returning the error or if it's a limitation on the cheap hosting I'm using and the server doesn't' know what to do in that case.  Probably the later as it works fine local until I upload it to the server.   

Oh, and I usually drink Newcastle, so I'm a cheap date.   🙂


Anthony
kt4obx


 

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ELMER

First, let me say that I never met an NCO that was a cheap date. Just for the record.

Will the RG-213 work? ABSOLUTELY. Will you even be able to tell the difference? Probably not. But here's the deal, I believe in building for the worst case scenario, not the best. On a perfect day, I can reach my repeater with my HT. On a bad day, I'm really happy I can squeeze out every last dB. Moral of the story, prepare for the worst, not the average. But I know you know this already.

Last point, RG-213, though a great cable, is more sensitive to EMI and RFI.

As far as UV. There you got me. 😱 I had not known that the 213 was better than the 8 family. I will say that I have a run of LMR 400 that has been sitting in our place in the North, outside, in 80-degree summers and -40-degree winters, and this for, don't quote me, but I believe close to a decade and it's still as good as new.

Hope this helps!

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LMR-400 may be just as good or better UV protection as RG-213 but I didn't question it.  I assumed if LMR-400 was newer and better than RG-213, the UV protection was probably there.  The guy spoke of it in his video when he compared RG-8 family to RG-213.   But I never realized until you just mentioned it that he never mentioned UV protection in his RG-213 to LMR-400 comparison.

I believe for the price difference of thirty bucks it's worth the LMR-400.  If it was 50 or 75 dollars difference, then it'd be a consideration.   I especially appreciate the the EMI and RFI sensitivity advice.  I'd like to stay as far away from EMI and RFI noise as I can.  

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