| Author |
Message |
    
Kattracker
| | Posted on Sunday, September 21, 2003 - 3:51 pm: | 
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Can anyone tell me what the maximum wattage RG8X coax can reliably handle?
Also, what is the latest and greatest in base station (11 Meter) coax? I have heard something about Belden having a double shielded coax.
Thanks,
Kattracker |
Tech808
| | Posted on Sunday, September 21, 2003 - 5:57 pm: |
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Kattracker,
RG-8/U 95% Shield = 2000watts
RG-8/U Mini 95% Shield = 1000watts
RG-213/U 95% Shield = 5000watts
Depends how much you want to spend but 213 will handle most everything.
Lon
Tech808 |
Kattracker
| | Posted on Sunday, September 21, 2003 - 8:28 pm: |
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Is RG8-X the same as RG-8/U ?
RG8-X is what I use on the mobile. If so, I am then safe for up to 1000 watts?
Thanks,
Kattracker  |
Bullet
| | Posted on Monday, September 22, 2003 - 4:52 pm: |
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rg8 mini and rg8x is the basic same. rg8 is the .400 inch stuff.
rg8x in the mobile is well safe for 1kw.
anymore and id go with times lmr 300.
i have melted sections of rg8 mini and rg8x
with deadkeys of 700 watts. but i was in good conversations that ran longer than i knew i should have run with that coax in line.
thats why i dont really like that coax for any thing other than mobiles or jumpers or lower power setups like 500 watts.
coax is so cheap compared to the rest of the station i dont see why anyone would skimp on this area of your station. |
fancypants
| | Posted on Saturday, October 04, 2003 - 4:57 am: |
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The power handling on coax goes up as swr is reduced. In other words, the higher your swr, the less power your coax will handle. That's because the coax is no longer just functioning as a "power funnel" from point A to point B, it is actually dissipating power. Any time something has to dissipate power, it will build up heat. Too much heat results in "thermo-nuclear meltdown" : )
With that in mind, i would not use RG-8X aka "mini 8" for anything more than about 800 watts or so. If you are running more than that on a regular basis, switch to RG-213. You are ALWAYS better off with RG-213 no matter what, but it is sometimes too big and bulky to work with.
As to actual specs, RG-213 is only rated for 1000 - 1200 watts at 27 MHz. I've seen guys dumping 10 KW through this stuff though with nary a problem. That is, so long as the antenna is good. I'm not saying that you should try doing this, only that i've seen others get away with it.
As a side note, i know a guy that has his bench wired with "antique" RG-58. Due to having everything "dialed in" with no reflection, i've watched him dump 4.5 KW through this time and time again in to his dummy load. I'm waiting for something to finally give out one of these days though as i've warned him about that TOO many times : )
On the other hand, i know a person who literally melt RG-58 while running a modified Texas 250. The cable was pinched in certain areas, creating big impedance bumps. Add this to a high swr and the coax was dissipating a LOT more power than it should have been. Others would not believe that a Texas 250 melted the coax ( i saved it to show others ), but i know what she was running and that's all the power it took. Then again, this was under less than ideal conditions as previously mentioned.
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Bruce
| | Posted on Saturday, October 04, 2003 - 9:26 am: |
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when i was running the 4cx250b amp on 2 meter moonbounce i forgot and left a rg-58 jumper in line. I will flat tell you rg-58 will not take 900 watts at 145 mhz .... it was fried. the swr of the quad stacked beams was 1.2/1 at 145.05 DO NOT RUN 58 with a amp just not smart. |
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