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Author Topic: RG-8x vs RG-8 coax  (Read 9919 times)
KC6SLA
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Posts: 35




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« on: November 08, 2013, 08:24:07 AM »

I have an Icom IC-735 connected to a Hustler 4-BTV ground mounted with 32 radials using RG8x coax. The coax is about 85 feet long. How much will I benifit on receive if I changed out the coax to RG-8 or the 400MAX from DX Engineering? I am looking to improve the receive as I get decent reports from others on my signal to them.
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AA4PB
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Posts: 12891




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« Reply #1 on: November 08, 2013, 08:30:54 AM »

On HF, the ability to copy is usually limited by the external noise picked up by the antenna. That means that reducing coax loss will increase the noise by the same amount it increases the signal and you will see no benefit.
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W9GB
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Posts: 2626




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« Reply #2 on: November 08, 2013, 08:35:19 AM »

BEST improvement, will be 1 dB per 100 feet of coaxial cable at 30 MHz (high end of 10 meters).
A difference of 1 dB is not detectable at HF.
The loss (dB) difference is LESS, with shorter cable length and LOWER Frequencies!
http://www.universal-radio.com/catalog/cable/coaxperf.html

SO, for HF Frequencies (3-30 MHz) DO NOT get sucked into Marketing, Do the Math.

THE SECRET SAUCE:  Purchase QUALITY Coaxial cables, with known manufacturer's specifications.  
The CB hobby got sucked into this nonsense in 1970s (CB Craze).
IF you are operating 50 MHz and Higher (VHF/UHF/Microwave) Frequencies,
THEN it DOES make a difference!


I used Belden RG-58/U for my Novice/General station on HF Bands !!!

Not worth the $$$ --- Go out to dinner instead.
« Last Edit: November 08, 2013, 08:43:48 AM by W9GB » Logged
KC6SLA
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Posts: 35




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« Reply #3 on: November 08, 2013, 10:46:01 AM »

Ya I know what therory saids but I was wondering what reality saids about it.
The RG-8x coax I am using right now is from Cable X-Perts. I bought it many years ago (like 12 to 14 years) and it has spent it's life outside in Iowa weather. I am not sure what the lifespan of coax is and was thinking if it was time to replace it, I would go with at bit less lossy cable.
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AA4PB
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« Reply #4 on: November 08, 2013, 11:54:04 AM »

Provided there isn't some unknown variable involved you'll find that practical experience will match the theory. You won't notice any difference in receive between RG-8x and RG-8 on the HF bands.
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M6GOM
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Posts: 944




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« Reply #5 on: November 08, 2013, 01:53:01 PM »

Ya I know what therory saids but I was wondering what reality saids about it.
Oh god you're one of those. I bet you think you need to ground all your station gear in the shack as well.....
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N4GKS
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Posts: 84




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« Reply #6 on: November 08, 2013, 03:49:44 PM »

Ya I know what therory saids but I was wondering what reality saids about it.
Oh god you're one of those. I bet you think you need to ground all your station gear in the shack as well.....

I'm glad you understood what he said because I didn't.
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W9GB
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Posts: 2626




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« Reply #7 on: November 08, 2013, 05:34:00 PM »

Quote from: KC9SLA
I know what theory says,  but I was wondering what reality said about it.
Kyle -

IF it would make a difference, I would have told you so.
You don't need an excuse to buy Coaxial Cable, if that us what you want to do.

Weathering (sunlight/UV light, moisture penetration) are realistic concerns, especially if coaxial connectors are not properly applied. Non-Contaminating outer jacket on coaxial cable (originally for military) has been available for decades.

REALITY:  I have a 50 foot section of Andrew RG-8/U installed in 1957 for my father's 46 MHz business radio system.  Swept with a TDR, its attenuation (dB loss) has not changed !
QUALITY of Product and Installation -- Priceless.

You have houses in Cedar Rapids SW side with Electrical wiring from 1910s --- it still works (lights still work).
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KB4QAA
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Posts: 2406




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« Reply #8 on: November 08, 2013, 07:07:01 PM »

http://vk1od.net/calc/tl/tllc.php/

Use Owens transmission line loss calculator to compare various lines at different bands.
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K8AXW
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Posts: 3898




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« Reply #9 on: November 08, 2013, 09:30:00 PM »

SLA: I've been using the same 100ft length of RG-8 coax for about 20 years now.  I run 12-1400W on it..... so far no problem.

If your installation coax is bothering you, replace it.  $80 bucks and you learn something and have peace of mind for the next 14 years.

BTW, I recently built a 40M inverted V antenna and fed it with RG-8X.  This is the first time in 57 years that I've ever used anything but RG-8.  I had misgivings but found that it works fine on HF.  Just like the chart says! And I saved a buncha bucks!
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N6AJR
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Posts: 9910




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« Reply #10 on: November 09, 2013, 09:07:23 AM »

I buy coax in quantity when I see a "deal" so I have probably 2000 feet of lmr 400. 1500 feet of 8 x and also rg 58, 59, rg 6  and some others in quantity.  I use 8 x for most everything under 75 to 100 feet and lower than 10 meters,  I use rg 8x on 6 meters too if the run is under 35 feet or so.   now if you are on 900 MHz or 1.2 gig, then use lmr 400 or better, because it makes a large difference.
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K5TEN
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« Reply #11 on: November 22, 2013, 02:29:30 PM »

Rebuilding my station.  Invested in RG 213 on HF and LMR 400 on 10m and and 2 meters.

An old ham feature in the QST archives says "do everything you can to invest in a good antenna system and coax/feedline.  It will pay dividends."  They are right.

I agree.  All the other older coax got trashed except for RG-8X for 80/160.
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G3RZP
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Posts: 4713




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« Reply #12 on: November 23, 2013, 01:58:15 AM »

If unhooking the antenna gives a noticeable drop in noise level on the highest frequency band that you use, it's not going to make any real difference. Only check that the band isn't dead, but usually, in a suburban environment, there'll be external noise on 10m even when the band is dead.
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W8JX
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Posts: 6038




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« Reply #13 on: November 23, 2013, 06:29:24 AM »

Rebuilding my station.  Invested in RG 213 on HF and LMR 400 on 10m and and 2 meters.

An old ham feature in the QST archives says "do everything you can to invest in a good antenna system and coax/feedline.  It will pay dividends."  They are right.

I agree.  All the other older coax got trashed except for RG-8X for 80/160.

I love this LMR 400 got to have for HF mentally. Unless it is a very long run like several hundred feet on HF you will see no difference over 213 and even 8x is good to 100feet and more on 20 and below. LMR 400 is more a state of mind ego thing than actually needing on HF.
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KA5IPF
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« Reply #14 on: November 23, 2013, 09:06:32 AM »

There is only one reason I see to use RG8 over 8X at HF frequencies, power handling capability. 8X is rated at 1kw at 10 MHz and 370w at 50 MHz. From Belden's website.

If running full legal limit use RG8 or equivalent, if less RG8X will work.

No matter what you use buy quality coax from a dealer you trust.

Clif
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