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Author Topic: Coax  (Read 2037 times)
KD8VIW
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Posts: 17




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« on: June 28, 2013, 06:35:41 AM »

hey how's everyone doing today!
I need to pick up coax for my first rig build, which will consist of a rc2950 and an  Antron 99, for the 10 m band.
I'm looking at the "MINI 8 LO-LOSS" at http://thewireman.com/coaxp.html and was wondering if anybody can suggest anything better for about the same price?
I'm only gonna be running about 35 W so I'm trying to get as high of a quality coax as I can without breaking the bank or having the wife rip my head off LOL.
I also found this data sheet Its Item#118, but I'm really at a loss as to what most of it means.
The person I talked to in the phone said they were suggesting it because its double shielded and the other two RG8x are not.
It sound good to me but wtf do I know LOL I'm a total newbie LOL so I figured I'd ask you all for some suggestions.

Thanks for the help,
Chad
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AA4HA
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Posts: 1398




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« Reply #1 on: June 28, 2013, 07:38:35 AM »

This thread may help you;


http://www.eham.net/ehamforum/smf/index.php?topic=67573.0

RG-8x type cable is 1/4". It is OK for jumpers but for running up to the antenna you may want to consider 3/8" to 1/2" cable (RG-8 or LMR-400).

Usually you will want to buy coax only once. if you do the connector ends correctly you will get 10-15 years out of it.
« Last Edit: June 28, 2013, 07:43:24 AM by AA4HA » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KE3WD
Member

Posts: 5694




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« Reply #2 on: June 28, 2013, 07:45:59 AM »

For that setup you don't really need to go all out in the coax department. 

Any reasonably good coax designed for CB can also be used on 10. 

73
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WB6BYU
Member

Posts: 13171




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« Reply #3 on: June 28, 2013, 08:25:22 AM »

How long is the run from the rig to the antenna?  With short lengths the choice of coax
is less critical, but once you get out to 100' or more then choosing a lower loss cable
may be more important.

However, I don't think there is much advantage in using double-shielded cable rather
than the standard stuff - at least I wouldn't pay extra for it in this case.
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K1WJ
Member

Posts: 454




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« Reply #4 on: June 28, 2013, 08:42:41 AM »

8x will be ok for run of 100ft, 9913 or 213 would be much better for 10m, the lower in freq you go the lower the loss will be, 8x is great for 80m. Get the best you can afford if you have a long coax run radio to antenna. Use as little as possible to get the job done, excess coax is just additional loss. 73 K1WJ David
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KE3WD
Member

Posts: 5694




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« Reply #5 on: June 28, 2013, 12:12:14 PM »

For a 2950 and an Antron 99, proper installation of the Antron, on a steel pole that's long enough and with the coax wrapped around that pole the correct number of turns as per the directions to decouple rf off of the shield is likely far more important than any amount of coax loss. 

Matter of fact, the OP could use 75 ohm TV rated coax here and it would work if installed properly. 

Use of just about any good 50 ohm coax should work just fine and that coax does not have to be some huge diameter stuff like 213 here. 

Mine is the voice of experience. 

The Antron 99, installed properly, can talk around the world and won't do too bad of a job at the local groundwave stuff, either.  Often even cross polarized to the other guy, no less.


73
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WH7DX
Member

Posts: 1029




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« Reply #6 on: June 28, 2013, 02:35:25 PM »

hey how's everyone doing today!
I need to pick up coax for my first rig build, which will consist of a rc2950 and an  Antron 99, for the 10 m band.
I'm looking at the "MINI 8 LO-LOSS" at http://thewireman.com/coaxp.html and was wondering if anybody can suggest anything better for about the same price?
I'm only gonna be running about 35 W so I'm trying to get as high of a quality coax as I can without breaking the bank or having the wife rip my head off LOL.
I also found this data sheet Its Item#118, but I'm really at a loss as to what most of it means.
The person I talked to in the phone said they were suggesting it because its double shielded and the other two RG8x are not.
It sound good to me but wtf do I know LOL I'm a total newbie LOL so I figured I'd ask you all for some suggestions.

Thanks for the help,
Chad

My attitude was - get something good because it will last and it's a small piece of the overall cost (a little extra)   If you decide to crank out more WATTS later, this stuff will be ready and you won't be putting the other stuff in a box.

Good cable..  it's much more flexible than the solid core that I bought 500ft of before.  Might need to remove a few wires to get inside connector center.

http://www.dxengineering.com/parts/dxe-400max

Good connectors..

http://www.dxengineering.com/parts/dxe-pl259

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KB4QAA
Member

Posts: 2340




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« Reply #7 on: June 28, 2013, 03:04:07 PM »

Chad,
RG8X (Mini-8) is more than adequate for up to a 100ft run at 10m.

If you needed to really economize, even RG-58 would be fine.

You do not need to buy anything with double shielding.  Like anything in life, you can spend as much as your wallet will afford for higher quality.  In this case, you would be unlikely to notice any difference.
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W8JX
Member

Posts: 5679




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« Reply #8 on: June 28, 2013, 03:19:48 PM »

Chad,
RG8X (Mini-8) is more than adequate for up to a 100ft run at 10m.

If you needed to really economize, even RG-58 would be fine.

You do not need to buy anything with double shielding.  Like anything in life, you can spend as much as your wallet will afford for higher quality.  In this case, you would be unlikely to notice any difference.

I do agree 8x is fine for 100 feet or even a bit more on HF. Some will try to insist you need 9913 or LMR 400 for HF but, unless your run is several hundred feet, it is a waste of money. RG 213 is good to a few hundred feet or a bit more on HF. If you have some 58 you can use it but if you have to buy it get 8x as it does not cost much more and will handle a kw on HF too.
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KD8VIW
Member

Posts: 17




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« Reply #9 on: June 28, 2013, 03:26:34 PM »

For a 2950 and an Antron 99, proper installation of the Antron, on a steel pole that's long enough and with the coax wrapped around that pole the correct number of turns as per the directions to decouple rf off of the shield is likely far more important than any amount of coax loss.  
Ha ha ha I was thinking I should try to avoid contact with the tower and pole as much as possible LOL Now I finding out not only do I want to make contact with the pole but wrap around it LOL THIS type of stuff I never would have figured out on my own Smiley
I'm actually planing on setting up a 30+ foot tower with a 15ish foot aluminum pole up from that. Is aluminum ok or should I use steel? How do I determine the correct number of turns around the pole?


How long is the run from the rig to the antenna?  With short lengths the choice of coax is less critical, but once you get out to 100' or more then choosing a lower loss cable may be more important.
However, I don't think there is much advantage in using double-shielded cable rather than the standard stuff - at least I wouldn't pay extra for it in this case.
It should be less than a 90' run of coax, how much less is still in question, If I run a guy wire from the tow to the top of the shack (literal reference in my case, I spend most of my time working in a 12x16 foot shed Smiley  ) Here's a pic w/ some calculations I've been doing to figure out how much coax I'm gonna need, once I get inside I figure at most I will another 12ft to get to the spot I picked out.

ok so rg8x isn't the same as rg8, is rg8u the same as rg8 or are all three different?

My attitude was - get something good because it will last and it's a small piece of the overall cost (a little extra)   If you decide to crank out more WATTS later, this stuff will be ready and you won't be putting the other stuff in a box.
Good cable..  it's much more flexible than the solid core that I bought 500ft of before.  Might need to remove a few wires to get inside connector center.
http://www.dxengineering.com/parts/dxe-400max
Good connectors..
http://www.dxengineering.com/parts/dxe-pl259
I would love to spend more for the coax and I could probably get away with going upwards of 50-55 cent a foot if it makes enough of a difference but I had to promise the wife I would just do a bare setup to get started, after all the stuff I've bought so far and yet more that I still have to buy she's already starting to give me the eye LOL I'm planning to buy 100' even though I may not need all of it at the moment, and a few extra ends for the meter and the amp (that I still need to see if it can be fixed) and its all really starting to add up :-/

This thread may help you;
http://www.eham.net/ehamforum/smf/index.php?topic=67573.0
RG-8x type cable is 1/4". It is OK for jumpers but for running up to the antenna you may want to consider 3/8" to 1/2" cable (RG-8 or LMR-400).
Usually you will want to buy coax only once. if you do the connector ends correctly you will get 10-15 years out of it.

Still working my way through the thread but its a good read so far, Thanks!

the spec sheet at http://thewireman.com/coaxdata.pdf really has me confused, could hanyone please let me know what these mean?

VF                                0.8
Center conductor          19/29 bc
Dielectric                     mcfpe
Cap. (pf/ft)                   24.5
Shield                          AL/tc
Jacket                         PVC IIA (just the type of plastic outer coating?)
OD  (outer diameter?)    0.242"
Volts/RMS                    300
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KD8VIW
Member

Posts: 17




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« Reply #10 on: June 28, 2013, 03:29:17 PM »

Chad,
RG8X (Mini-8) is more than adequate for up to a 100ft run at 10m.
If you needed to really economize, even RG-58 would be fine.
You do not need to buy anything with double shielding.  Like anything in life, you can spend as much as your wallet will afford for higher quality.  In this case, you would be unlikely to notice any difference.
what is the purpose of double shielding, does it affect tx or is it only to block out extra noise when receiving?
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WH7DX
Member

Posts: 1029




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« Reply #11 on: June 28, 2013, 04:15:54 PM »

Here's my thinking.. 

Even if you start out small, like I did, you will be building your system and 90% chance you'll get an amp in the future.   If I had bought cheap cable before my amp, I would have had to replace it all.   I've used close to 700 ft now.  I bought a 500ft spool of LMR-400 solid core for $250 + another $100 for shipping to HI (still a great price $0.70 ft).  And I've recently purchased 200 feet of LMR-400 from DX Engineering (stranded center - which I prefer).  I have a Hex Beam, 3 dipoles and a beverage with external switch etc.. When I first started I only needed about 50ft for my 20M dipole on a PVC pipe (with my Ebay TS-570 that I still have and power supply - that I also bought big enough to handle more than I originally needed Astron RS-35M - why push things etc..   Just don't box yourself in with low power cable or cable that doesn't handle the weather as well.   The good stuff is designed to last for 20+ years.

Coax Calculator..

http://www.timesmicrowave.com/cgi-bin/calculate.pl

Average price of Ham Radio Shack?   $2500-4000?    We'll use $3,200.   If you get into it, you'll be there and higher with time.

$0.40 difference between good coax and cheap coax at 200ft = $80 or 2.5% of your overall cost.   If you need to switch out the cheap cable later for power, weather etc..  your down.   

So I would recommend buying nothing less than high-power coax.
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WB6BYU
Member

Posts: 13171




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« Reply #12 on: June 28, 2013, 04:26:18 PM »

Double shielding reduces the amount of RF that passes through the shield, either on TX or RX.
It is particularly useful in applications such repeaters where maximum isolation is needed to
keep out strong signals, or to keep from radiating signals that could be picked up by a
nearby receiver.

In most ham applications there will be more radiation from the coax due to common mode
current on the outside of the shield than radiation passing through the shield.


The other parameters in question:

Vf = velocity factor.  Use this number if you have to calculate a particular length of cable,
such as 1/4 wavelength.  (The electrical length times the velocity factor gives the physical length.)

Center conductor consists of 19 strands of #29 wire.

Dielectric is the type of plastic used in the center insulator.

Cap is the capacitance in picofarads per foot.  Usually this doesn't matter.

Shield looks like Aluminum foil with a copper wire (Huh)

Jacket is the type of outer plastic cover - some types are more resistant to UV radiation, etc.

Outer diameter is the size in inches.

Voltage rating is the maximum rated voltage between the two conductors.  For 300V peak
at a 50 ohm impedance the line should handle about 900 watts maximum with a perfect SWR.
While some people have pushed RG-8X beyond this, the line may overheat on the higher bands
where the loss per foot is higher, and it doesn't allow any safety margin in case the inner
conductor migrates through the foam center insulation when you have a bend in the cable
in the hot sun, or someone tightens a tie wrap down too tight securing it to a tower leg.


Wrapping coax around a metal mast to make a choke is convenient, but not very effective.


RG-8/U and RG-8A/U are former military coax type designators.  They are no longer active,
but have been superseded by RG-213.  Now anybody can use those numbers for their products
without having to meet the former standard.  RG-8X ("Mini-8") was an attempt to make a smaller
cable that was less lossy than RG-58:  it was never a military standard, and there never has been
a standard specification for that particular part number.

I think the difference between RG-8/U and RG-8A/U was that the latter had a stranded
center conductor while the former was solid copper.  The nominal impedance was 52 ohms,
while the new RG-213 is 50ohms and has a non-contaminating jacket material.

Here's a convenient calculator for coax losses:

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

You'll find RG-8X listed as Belden 9258:  that is just one manufacturer, and since there is no
standard spec for the stuff you'll have to guess close the particular variant you are considering
is to this Belden type.  The most important factor for your use is probably the loss, usually given
as dB / 100' at specific frequencies.  In this case, 100' of Belden 9258 RG-8/X at 29 MHz will have
1.6dB loss, so about 70% of your power will reach the antenna.  Using the larger RG-213 would
bring that up to 80%.  If you really want to be cheap you could use RG-6A TV coax, with about
the same loss as RG-213 or RG-8, though with some possible variation in SWR.


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KD8VIW
Member

Posts: 17




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« Reply #13 on: June 28, 2013, 07:45:45 PM »

Double shielding reduces the amount of RF that passes through the shield, either on TX or RX.
It is particularly useful in applications such repeaters where maximum isolation is needed to
keep out strong signals, or to keep from radiating signals that could be picked up by a
nearby receiver.
In most ham applications there will be more radiation from the coax due to common mode
current on the outside of the shield than radiation passing through the shield.

Ok that makes sense,  So if it was a difference of more than few bucks, its not worth it in my situation.

The other parameters in question:
Vf = velocity factor.  Use this number if you have to calculate a particular length of cable,
such as 1/4 wavelength.  (The electrical length times the velocity factor gives the physical length.)

Center conductor consists of 19 strands of #29 wire.

This brings up another question for me, stranded vs solid? I know when it comes to networking we always use solid for our long runs and stranded for patch cables and short runs, partly due to the skin effect vs the proximity, does that come into play here?


Dielectric is the type of plastic used in the center insulator.

Cap is the capacitance in picofarads per foot.  Usually this doesn't matter.

Shield looks like Aluminum foil with a copper wire (Huh)
Its been awhile but it seemed like there was a big outcry in computer when memory was switched over from aluminum to copper contacts and people were told not to use copper tipped memory in aluminum slots, I think because doesn't putting aluminum and copper wire together cause corrosion/oxidation or something like? Or would that not really be a problem in the wire other than at the end due to lack of O2?

Jacket is the type of outer plastic cover - some types are more resistant to UV radiation, etc.

Outer diameter is the size in inches.

Voltage rating is the maximum rated voltage between the two conductors.  For 300V peak
at a 50 ohm impedance the line should handle about 900 watts maximum with a perfect SWR.
While some people have pushed RG-8X beyond this, the line may overheat on the higher bands
where the loss per foot is higher, and it doesn't allow any safety margin in case the inner
conductor migrates through the foam center insulation when you have a bend in the cable
in the hot sun, or someone tightens a tie wrap down too tight securing it to a tower leg.
ha ha ha I forget how much power some of you all run! I remember back in the day amps ran about a buck a watt does this still hold true?

Wrapping coax around a metal mast to make a choke is convenient, but not very effective.

Is there any negative to doing this, like say I wrapped around the pole 30 times could this have a negative effect at all? I know back when I used to run a cb everyone said don't coil your wire or you'll create a choke, bad thing at low watts, good thing at high watts?


I think the difference between RG-8/U and RG-8A/U was that the latter had a stranded
center conductor while the former was solid copper.  The nominal impedance was 52 ohms,
while the new RG-213 is 50ohms and has a non-contaminating jacket material.

Here's a convenient calculator for coax losses:

http://www.vk1od.net/calc/tl/tllc.php
LOL not sure what half the fields are for LOL got a lot to learn.

You'll find RG-8X listed as Belden 9258:  that is just one manufacturer, and since there is no
standard spec for the stuff you'll have to guess close the particular variant you are considering
is to this Belden type.  The most important factor for your use is probably the loss, usually given
as dB / 100' at specific frequencies.  In this case, 100' of Belden 9258 RG-8/X at 29 MHz will have
1.6dB loss, so about 70% of your power will reach the antenna.  Using the larger RG-213 would
bring that up to 80%.  If you really want to be cheap you could use RG-6A TV coax, with about
the same loss as RG-213 or RG-8, though with some possible variation in SWR.

Well after playing with that calculator it looks like I will be running that guy wire for sure! LOL
One other question speaking of calculators/programs, is there one out there that will figure estimated horizon distance based on location or gps cords?


thanks for all the great info, I feel like I know a lot more than I did a few days ago, and one of the things is what I learned is that I'm just scratching the surface! Cheesy

Thanks again, 73,
Chad
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NI3S
Member

Posts: 67




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« Reply #14 on: June 28, 2013, 08:13:57 PM »

If that shed is going to be your shack, would it be possible to mount the tower next to it?
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