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Author Topic: Coax Cable For #6 Meter's...  (Read 997 times)
AA4PB
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« on: September 12, 2003, 08:47:12 AM »

While I don't disagree with the previous postings of recommending the use of lower loss coax, I seriously doubt that your use of 100-feet of RG8x is your problem.

At 52Mhz and a 1:1 SWR, 100 feet of RG213 has a loss of 1.48dB. 100 feet of RG8x has a loss of 2.24dB. Thats a difference of only 0.76dB which will be hardly noticable as far as performance goes. Remember, 6dB is only one S-unit difference.

Tell us a little more about your problem. How is the SWR on the antenna and what type of antenna is it? Is it horizontally polarized if you are working SSB or vertical polarized if you are working FM? Cross polarization will in theory cost you 20dB - way more than the difference between RG8x and RG213.

The best length for a coax run (provided it is not part of some matching section) is always the minimum length that will reach between the antenna and the rig.
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KC0OHP
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Posts: 66




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« Reply #1 on: September 12, 2003, 05:12:13 AM »

Question...

  Could someone please tell me what type of
Coax Cable is considered the best for operating
on the 6 meter band!!  Hope this is not a dumb question
too be asking.  I think it's coax I'm using ;-((

  What type of RG; is considered the best?  Also
what length should I use?  50, 75, 100 feet
length?  I looked at a lot of web sites that sell
coax, and different types and specification's also!!

  I'm using RG-8x, 100' feet.  This I feel may not
be the right Coax for 6 mtr's.  Also maybe be
part of my receiving problem's  signals on 6 too?

   Still new at this hobby ham radio, and learning
more about it.  Any information, and general help
on this subject appreciated...

   73 de
   Dwight KC0OHP...
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W8JI
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« Reply #2 on: September 12, 2003, 06:04:13 AM »

At only 100 feet or less of length the best compromise between cost and loss would be good quality RG-8 style cables, like LMR-400 or some of the other high quality foam insulation Belden cables.

RG-8 X is really a poorly made cable for any frequency above 30-50MHz, unless it is a very short run. The off brand cables all have pretty high loss compared to better cables.

The cable can be any length, length does not matter except it obviously has to reach. Don't use grossly excessive lengths.

Regular good quality PL259's/SO-239's are fine at six meters, they have immeasurable loss. Stay away from cheap Radio Shack connectors and such. As with the cables buy name brand or a trusted source. The Wireman sells good stuff.

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W4QA
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« Reply #3 on: September 12, 2003, 06:57:51 AM »

Depending on whether you need physical flexibility in the cable or not, I would echo the previous poster's thoughts as well and go with a cable that has a lower loss characteristic at the higher frequencies.  Where RG-213, RG-8, and RG-8X are fine below 30 Mhz (in general), once you go above this you really should consider the newer cables with a bonded foil shield + braid or even hardline.

Belden has two cables that come to mind that are ideal for VHF applications.  The Belden 9913F7 is a 100% shielded, nitrogren gas injected dielectric coax with a stranded center conductor -- super low loss for a very flexible RG-8 sized coax.  Connectors go onto this coax in a jiffy.

For applications where movement is not an issue, go with the Belden RF-400 (their part is 7810A) which is a PE jacketed, solid center conductor, 100% shielded (braid + bonded shield) coax -- takes standard connectors.  This cable is widely used in the Land Mobile Radio and Cellular commercial markets.  The stuff can be buried in the ground with no problems and is about the best you can get in a .400" coax without stepping up to some type of hardline -- it is very similar in construction to the LMR400 coax.

You can't go wrong with the Belden cables for quality.
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KA2UUP
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Posts: 388




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« Reply #4 on: September 12, 2003, 08:26:32 AM »

The dumbest question is the one that is not asked.  We are here to help.

Now, I am using 75 feet of RG-213.  I also use for VHF/UHF 9913 cable.  In terms of loss per feet, 9913 is a better choice.  Its a little more, but its better.
9914 is also a good choice with more ore less the same loss as 9913.

Advantage of RG-213 and 9914 is that they are flexible and buriable.  9913 is more rigid and I would not recommend it for repeated turning with an antenna mounted on a rotor.  Hope this helps.

Good luck from Bert @ KA2UUP.
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KB0ETC
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Posts: 248




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« Reply #5 on: September 12, 2003, 10:58:46 AM »

Well lets let the numbers speak for themselves.

This is Belden 8267 (RG-213U)
Length: 100'
Freq: 52Mhz
SWR: 1:1
Power In: 100 watts

RESULTS
Matched Loss: 1.482db
SWR Loss: 0
Total Loss: 1.482
Power Out: 71.90 Watts

This is Belden 9913 (Same parameters as above)
Matched Loss: 0.903
SWR Loss: 0
Total Loss: 0.903
Power Out: 81.222 Watts

Now is there a difference, yes a small amount of difference in loss and power that eventually will be your ERP.

Stick to a good quality cable.  Don't use generic RG-8 Like Radio Shack junk.  Any RG-213, 9913/9914 cable is ideal for your application.

If you have a pocket full of money then move to Time LMR or Andrew Heliax Smiley

The length of coax that you need is exactly what it takes to get from your antenna to your radio/tuner.  Unless you are building phasing lines, it doesn't matter.

73's
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WA4MJF
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Posts: 1003




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« Reply #6 on: September 12, 2003, 12:52:20 PM »

RG-8 with a foam dilectic is better (by a hair)
loss wise than RG-213.  The down side is
the jacket is not as durable so you change it more
often.

I use RG-8 foam for 6 meters and 9913 for two
meters and down.  Runs are less than 100 feet.

73 de Ronnie
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W8JI
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« Reply #7 on: September 12, 2003, 03:28:14 PM »

The big problem with RG8X is it is NOT a mil speced cable, so the performance varies all over the place. By rights, it should NOT have been assigned an RG number. The same is NOT true for other cables, unless you purchase "type" cables.

I'd wager very few stores sell Belden RG8X, most are probably odd brands with no QC and no tested ratings for loss.

I wouldn't hesitate to use even the off-brand stuff for short runs (under 100ft) on 20 meters and down, but not for 100ft on six meters! At least not the stuff I have purchased.

73 Tom
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W8JI
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« Reply #8 on: September 12, 2003, 03:30:19 PM »

But I agree his problem might not be the cable. It might be the antenna, the rig, the cable, the location, the band, or a combination of everything.  
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WA4MJF
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« Reply #9 on: September 12, 2003, 03:41:46 PM »

Tom, I think you mean 20 meters and up (longer).

73 de Ronnie
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KG4VPV
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« Reply #10 on: September 13, 2003, 02:18:19 AM »

I agree with W4QA, Belden Low Loss is the way to go.  Although I didn't go with it for the 6 feet of run in the cab of the truck, RF-400 is running from the base station to the antenna at home.  Trust me,it is well worth the pain of running this less flexible cable through a wall to reap the low loss benefits of it. Something about efficiency really makes me sleep better at night HIHI.  Im not sure whether or not I got taken on the price of it, but I ended up spending 63 cent a foot.
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W8JI
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« Reply #11 on: September 13, 2003, 06:27:02 AM »

That's right. Up down sideways, I always get confused. ;-)

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AA4PB
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Posts: 12899




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« Reply #12 on: September 16, 2003, 09:40:29 PM »

Guys, run the numbers. The additional loss of 100-feet of RG8X (even though not MilSpec) will result in less than 1 S unit difference in signal strength. It is most certainly not the cause of him not being able to make any 6M contacts. I recommend that he concentrate on finding the real problem before changing out the coax.
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W8JI
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« Reply #13 on: September 17, 2003, 07:33:33 AM »

I agree it probably isn't the coax, but he did ask what the best cable was.

RG8X ranges from OK (for top line stuff like Belden) to absolute junk. Some of the stuff I've purchased actually has fallen apart from UV exposure!!

Better to stick with a known good cable, than brand X.

73 Tom
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