Re: [Elecraft] RG-8X

[Jim Brown]

On 2/26/2018 3:15 PM, Bob McGraw K4TAX wrote:
I found that not all RG-8X is created equal. 


Absolutely! And this is true of ALL coax types. There's a lot of junk 
floating around.


73, Jim K9YC

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Re: [Elecraft] RG-8X

[donovanf]

DX Engineering 400MAX is an excellent choice, I'm sure you'll 
be pleased with its performance. Make the extra effort to seal the 
connectors very, very well and be sure you install the cable on 
your tower securely so that high winds cannot possibly cause 
abrasion of the coaxial cable jacket. 


Good luck! 


73 
Frank 
W3LPL 

- Original Message -

From: "Richard" <flat...@comcast.net> 
To: "Elecraft Reflector" <elecraft@mailman.qth.net> 
Sent: Tuesday, February 27, 2018 2:02:32 AM 
Subject: Re: [Elecraft] RG-8X 

The problem is often I get an answer or a request for more info, and I reply 
without realizing that it goes to an individual’s e-mail address, not to the 
selector at large. It almost happened with this one. 

I was talking about 75 to 100 feet on 50 MHz. 

I plan to use DXE’s 400MAX, with which I have had excellent results before. 

Richard - W4KBX 

> On Feb 26, 2018, at 8:23 PM, donov...@starpower.net wrote: 
> 
> W4KBX hasn't commented about the frequency at which he intends 
> to use 100 feet of RG-8X. 0.24 inch diameter coax -- no matter 
> what type or manufacturer -- isn't the best choice for 100 foot cable 
> lengths at 21 MHz or above. 
> 
> 
> 
> It s a much better investment to step up to the next larger diameter 
> coax, especially at 50 MHz. LMR400 or LMR400-DB (waterproof 
> flooded coax) are much better choices for 100 foot cable lengths 
> at 21 MHz or above. 
> 
> 
> Of course its hard to beat LDF4-50A but at a cable length of only 
> 100 feet the difference in loss compared to LMR400 is less than 
> 1/2 dB at 50 MHz. You'll never notice the difference. 
> 
> 
> LDF4-50A or LMR600 is an excellent choice for a 200 foot coax 
> length at 50 MHz. Much beyond 200 feet at 50 MHZ and LDF5-50A 
> or LMR900 is a better choice. 
> 
> 
> All of this assumes proper installation. Moisture intrusion resulting 
> from poor installation practices will degrade your investment no 
> matter what coax you select. 
> 
> 
> 73 
> Frank 
> W3LPL 
> 
> - Original Message - 
> 
> From: j...@kk9a.com 
> To: elecraft@mailman.qth.net 
> Sent: Monday, February 26, 2018 10:28:05 PM 
> Subject: [Elecraft] RG-8X 
> 
> The original post by W4KBX was this: "I’m seeking recommendations for 
> RG-8X coax with the lowest loss. The total run will be about 100 feet." 
> 
> You cannot defy physics and have low loss with 1/4" coax, no matter who 
> the manufacture is, but RG8X was his criteria. 
> 
> John KK9A 
> 
> 
> Jim Brown K9YC wrote: 
> 
> On 2/26/2018 11:02 AM, Bob McGraw K4TAX wrote: 
>> I did inquire as to the application. To feed a 6M yagi being a 6OWL6W. 
> My thinking, I would cringe at putting up a nice yagi such as this and 
> not use the feedline with the lowest loss possible. Most likely Andrew 
> LDF4-50A hardline. 
> 
> Me too! The 350 ft run from my shack to the 3-el SteppIR is 7/8-in 
> hardline, transitioning to a short length of flexible coax for the 
> rotator loop. Scrounged the hard line used for roughly $1/ft. Loss is 
> about 1 dB on 6M. 
> 
> 73, Jim K9YC 
> 
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Re: [Elecraft] RG-8X

[Richard]

The problem is often I get an answer or a request for more info, and I reply 
without realizing that it goes to an individual’s e-mail address, not to the 
selector at large. It almost happened with this one.

I was talking about 75 to 100 feet on 50 MHz.

I plan to use DXE’s 400MAX, with which I have had excellent results before.

Richard - W4KBX

> On Feb 26, 2018, at 8:23 PM, donov...@starpower.net wrote:
> 
> W4KBX hasn't commented about the frequency at which he intends 
> to use 100 feet of RG-8X. 0.24 inch diameter coax -- no matter 
> what type or manufacturer -- isn't the best choice for 100 foot cable 
> lengths at 21 MHz or above. 
> 
> 
> 
> It s a much better investment to step up to the next larger diameter 
> coax, especially at 50 MHz. LMR400 or LMR400-DB (waterproof 
> flooded coax) are much better choices for 100 foot cable lengths 
> at 21 MHz or above. 
> 
> 
> Of course its hard to beat LDF4-50A but at a cable length of only 
> 100 feet the difference in loss compared to LMR400 is less than 
> 1/2 dB at 50 MHz. You'll never notice the difference. 
> 
> 
> LDF4-50A or LMR600 is an excellent choice for a 200 foot coax 
> length at 50 MHz. Much beyond 200 feet at 50 MHZ and LDF5-50A 
> or LMR900 is a better choice. 
> 
> 
> All of this assumes proper installation. Moisture intrusion resulting 
> from poor installation practices will degrade your investment no 
> matter what coax you select. 
> 
> 
> 73 
> Frank 
> W3LPL 
> 
> - Original Message -
> 
> From: j...@kk9a.com 
> To: elecraft@mailman.qth.net 
> Sent: Monday, February 26, 2018 10:28:05 PM 
> Subject: [Elecraft] RG-8X 
> 
> The original post by W4KBX was this: "I’m seeking recommendations for 
> RG-8X coax with the lowest loss. The total run will be about 100 feet." 
> 
> You cannot defy physics and have low loss with 1/4" coax, no matter who 
> the manufacture is, but RG8X was his criteria. 
> 
> John KK9A 
> 
> 
> Jim Brown K9YC wrote: 
> 
> On 2/26/2018 11:02 AM, Bob McGraw K4TAX wrote: 
>> I did inquire as to the application. To feed a 6M yagi being a 6OWL6W. 
> My thinking, I would cringe at putting up a nice yagi such as this and 
> not use the feedline with the lowest loss possible. Most likely Andrew 
> LDF4-50A hardline. 
> 
> Me too! The 350 ft run from my shack to the 3-el SteppIR is 7/8-in 
> hardline, transitioning to a short length of flexible coax for the 
> rotator loop. Scrounged the hard line used for roughly $1/ft. Loss is 
> about 1 dB on 6M. 
> 
> 73, Jim K9YC 
> 
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Re: [Elecraft] RG-8X

[donovanf]

W4KBX hasn't commented about the frequency at which he intends 
to use 100 feet of RG-8X. 0.24 inch diameter coax -- no matter 
what type or manufacturer -- isn't the best choice for 100 foot cable 
lengths at 21 MHz or above. 



It s a much better investment to step up to the next larger diameter 
coax, especially at 50 MHz. LMR400 or LMR400-DB (waterproof 
flooded coax) are much better choices for 100 foot cable lengths 
at 21 MHz or above. 


Of course its hard to beat LDF4-50A but at a cable length of only 
100 feet the difference in loss compared to LMR400 is less than 
1/2 dB at 50 MHz. You'll never notice the difference. 


LDF4-50A or LMR600 is an excellent choice for a 200 foot coax 
length at 50 MHz. Much beyond 200 feet at 50 MHZ and LDF5-50A 
or LMR900 is a better choice. 


All of this assumes proper installation. Moisture intrusion resulting 
from poor installation practices will degrade your investment no 
matter what coax you select. 


73 
Frank 
W3LPL 

- Original Message -

From: j...@kk9a.com 
To: elecraft@mailman.qth.net 
Sent: Monday, February 26, 2018 10:28:05 PM 
Subject: [Elecraft] RG-8X 

The original post by W4KBX was this: "I’m seeking recommendations for 
RG-8X coax with the lowest loss. The total run will be about 100 feet." 

You cannot defy physics and have low loss with 1/4" coax, no matter who 
the manufacture is, but RG8X was his criteria. 

John KK9A 


Jim Brown K9YC wrote: 

On 2/26/2018 11:02 AM, Bob McGraw K4TAX wrote: 
> I did inquire as to the application. To feed a 6M yagi being a 6OWL6W. 
My thinking, I would cringe at putting up a nice yagi such as this and 
not use the feedline with the lowest loss possible. Most likely Andrew 
LDF4-50A hardline. 

Me too! The 350 ft run from my shack to the 3-el SteppIR is 7/8-in 
hardline, transitioning to a short length of flexible coax for the 
rotator loop. Scrounged the hard line used for roughly $1/ft. Loss is 
about 1 dB on 6M. 

73, Jim K9YC 

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Re: [Elecraft] RG-8X

[Bob McGraw K4TAX]

I found that not all RG-8X is created equal.  For one project, I 
measured 3 or 4 different brands of new RG-8X to find that the loss can 
vary considerably.  The measurement method was to use 50 ft, snake it 
back an forth across the floor so as not to have adjacent coupling, the 
ends fitted with N type connectors and connected to my Spectrum Analyzer 
with tracking generator. Normal meaningful sweep was 0.1 MHz to 1 
GHz.    I don't recall the numbers but I was a bit surprised to find 
significant difference as I recall.  The project was in preparation of 
antennas for Field Day operation.


73

Bob, K4TAX


On 2/26/2018 4:28 PM, j...@kk9a.com wrote:

The original post by W4KBX  was this:  "I’m seeking recommendations for
RG-8X coax with the lowest loss. The total run will be about 100 feet."

You cannot defy physics and have low loss with 1/4" coax, no matter who
the manufacture is, but RG8X was his criteria.

John KK9A


Jim Brown K9YC wrote:

On 2/26/2018 11:02 AM, Bob McGraw K4TAX wrote:

I did inquire as to the application.  To feed a 6M yagi being a 6OWL6W.

My thinking, I would cringe at putting up a nice yagi such as this and
not use the feedline with the lowest loss possible.  Most likely Andrew
LDF4-50A hardline.

Me too!  The 350 ft run from my shack to the 3-el SteppIR is 7/8-in
hardline, transitioning to a short length of flexible coax for the
rotator loop. Scrounged the hard line used for roughly $1/ft.  Loss is
about 1 dB on 6M.

73, Jim K9YC

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Re: [Elecraft] RG-8X

[Jim Brown]

On 2/26/2018 10:45 AM, Tom Georgens wrote:

HI Jim

Thanks for your informed commentary

One question I have had is, if loss is dominated by resistive losses at HF,
does coax actually get more lossy with age?  If so, what is the mechanism.
Does the dielectric change properties, or do the copper surfaces corrode or
break down?   If the dielectric breaks down, then the impedance should
change as well

Most  info on cable life deal primarily with the UV, heat, and moisture
resistance of the jacket but I have seen very little about aging of the
internal components.


Hi Tom. I don't know enough about this issue to say anything useful, 
except for this.  When N6RZ died something like 8 years ago, I bought a 
lot of his stuff and helped his XYL, Kerry, get rid of the rest of it. 
He had a lot of coax and some hard line; I bought the hard line, and 
took the random lengths of coax to an NCCC meeting, telling members 
where it had come from. Almost all of it was good quality stuff, some 
used inside, some outside. I even found some stored in a shed. I'd guess 
most of it was at least 20 years old. Everyone turned their noses up at 
it, so I brought it home, made stubs out of it, and measured their 
effectiveness. I didn't have a VNA then, so I used an HP generator and 
HP spectrum analyzer (as an RF voltmeter), doing point by point 
measurements. Most of the stub data in that Q are for that cable.


Since a harmonic stub depends on a low value of impedance to work, that 
tells me the cables were still quite good. The only bad piece of cable I 
found was one whose interior jacket was green from oxidation of the 
shield. I think it had come from that shed.


Until I learn more about it, I go under the assumption that the primary 
hazard is moisture.  Because dielectric loss doesn't kick in until at 
least UHF, I don't buy that being as a factor at HF. A few years ago, I 
noticed moisture around the Polyphaser for one of my high dipoles when I 
removed it for some reason. I had only recently replaced the dipole and 
the coax run (Belden 8213), but hadn't done a good enough job of sealing 
the coax around the center insulator. Water penetrated, came down 
between the braid and dielectric, and in less than a year, had turned 
the shield black. I put that length of coax on the VNA and found that 
loss had increased from about 0.4 dB to about 0.45 dB.


I'm copying this to the reflector, hoping that guys like W3LPL will jump 
in with more.


73, Jim


Thanks

Tom W2SC

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Brown
Sent: Monday, February 26, 2018 10:11 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] RG-8X

On 2/26/2018 9:28 AM, j...@kk9a.com wrote:

I believe all RG8X has a .242 diameter PVC jacket and about the same loss.
Certainly some brands are better made, I use only Belden 9258.

Not quite. First, for at least 40 years, RG-numbers are NOT a specification,
but only a generic description of cable, mostly telling us the approximate
outer diameter and the characteristic impedance (Zo).
Below about 500 MHz, loss in coax is all due to I squared R, which depends
entirely on the combined resistance of the center conductor and the shield
at the frequency of interest.

Zo depends on conductor diameters, spacing, and the dielectric material.
Coax with a foam dielectric allow the center conductor to be larger for the
same shield diameter. THAT'S why foam cables have lower loss, NOT because of
lower loss in the dielectric -- dielectric loss doesn't show up until we're
well into the UHF region. Shield resistance is reduced by a larger diameter
for two reasons -- more copper and skin effect. Many coax cables don't use
copper for center or shield or both. Loss will be greater at low frequencies
if the center is copper-coated steel, which is often done for both cost and
physical strength. Loss will also be greater if the shield uses less copper
or is made from aluminum.

As usual, Frank has asked the right questions -- there are important
"applications-related" differences between coax types, even from the same
manufacturer.

In general, it's best to use bigger coax from a trusted manufacturer, and
with the best quality shield. Larger coax has less loss. Don't buy smaller
coax because you're running low power -- our Field Day team runs QRP, and
all of our coax is RG8-size with a foam dielectric for low loss and a robust
copper braid shield!

There's a tutorial on this topic at http://k9yc.com/Coax-Stubs.pdf

73, Jim K9YC

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Re: [Elecraft] RG-8X

[Jim Brown]

On 2/26/2018 11:02 AM, Bob McGraw K4TAX wrote:

I did inquire as to the application.  To feed a 6M yagi being a 6OWL6W.  My 
thinking, I would cringe at putting up a nice yagi such as this and not use the 
feedline with the lowest loss possible.  Most likely Andrew LDF4-50A hardline.


Me too!  The 350 ft run from my shack to the 3-el SteppIR is 7/8-in 
hardline, transitioning to a short length of flexible coax for the 
rotator loop. Scrounged the hard line used for roughly $1/ft.  Loss is 
about 1 dB on 6M.


73, Jim K9YC


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Re: [Elecraft] RG-8X

[Bob McGraw K4TAX]

I did inquire as to the application.  To feed a 6M yagi being a 6OWL6W.  My 
thinking, I would cringe at putting up a nice yagi such as this and not use the 
feedline with the lowest loss possible.  Most likely Andrew LDF4-50A hardline. 

Bob, K4TAX


Sent from my iPhone

> On Feb 26, 2018, at 12:21 PM, Dave Cole (NK7Z)  wrote:
> 
> Thanks for sharing!  Very interesting.
> 
> 73s and thanks,
> Dave
> NK7Z
> https://www.nk7z.net
> 
>> On 02/26/2018 10:10 AM, Jim Brown wrote:
>> 
>> There's a tutorial on this topic at http://k9yc.com/Coax-Stubs.pdf
>> 73, Jim K9YC
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Re: [Elecraft] RG-8X

[Dave Cole (NK7Z)]

Thanks for sharing!  Very interesting.

73s and thanks,
Dave
NK7Z
https://www.nk7z.net

On 02/26/2018 10:10 AM, Jim Brown wrote:


There's a tutorial on this topic at http://k9yc.com/Coax-Stubs.pdf

73, Jim K9YC

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Re: [Elecraft] RG-8X

[Jim Brown]

On 2/26/2018 9:28 AM, j...@kk9a.com wrote:

I believe all RG8X has a .242 diameter PVC jacket and about the same loss.
Certainly some brands are better made, I use only Belden 9258.


Not quite. First, for at least 40 years, RG-numbers are NOT a 
specification, but only a generic description of cable, mostly telling 
us the approximate outer diameter and the characteristic impedance (Zo). 
Below about 500 MHz, loss in coax is all due to I squared R, which 
depends entirely on the combined resistance of the center conductor and 
the shield at the frequency of interest.


Zo depends on conductor diameters, spacing, and the dielectric material. 
Coax with a foam dielectric allow the center conductor to be larger for 
the same shield diameter. THAT'S why foam cables have lower loss, NOT 
because of lower loss in the dielectric -- dielectric loss doesn't show 
up until we're well into the UHF region. Shield resistance is reduced by 
a larger diameter for two reasons -- more copper and skin effect. Many 
coax cables don't use copper for center or shield or both. Loss will be 
greater at low frequencies if the center is copper-coated steel, which 
is often done for both cost and physical strength. Loss will also be 
greater if the shield uses less copper or is made from aluminum.


As usual, Frank has asked the right questions -- there are important 
"applications-related" differences between coax types, even from the 
same manufacturer.


In general, it's best to use bigger coax from a trusted manufacturer, 
and with the best quality shield. Larger coax has less loss. Don't buy 
smaller coax because you're running low power -- our Field Day team runs 
QRP, and all of our coax is RG8-size with a foam dielectric for low loss 
and a robust copper braid shield!


There's a tutorial on this topic at http://k9yc.com/Coax-Stubs.pdf

73, Jim K9YC

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Re: [Elecraft] RG-8X

[donovanf]

Hi Richard, 


Please provide a little more information so that your question can 
be answered more accurately. 


At what frequencies will you be using your coax? 


Will your coax be buried or laid on the ground, or will it not be 
in contact with the ground at all? 



Many coaxial cables have a vinyl jacket which is very susceptible 
to moisture penetration if buried or laid on moist ground. 


Are rodents (squirrels, mice, etc) a problem in your area? 


Vinyl jacketed coax is very susceptible to rodent damage which 
will quickly increase your coax loss. 


73 
Frank 
W3LPL 


From: Richard  
To: Elecraft Reflector  
Sent: Monday, February 26, 2018 8:35 AM 
Subject: [Elecraft] RG-8X 

I’m seeking recommendations for RG-8X coax with the lowest loss. The total run 
will be about 100 feet. 

Cheers! 

Richard Kunc — W4KBX 

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Re: [Elecraft] RG-8X

[Bob McGraw K4TAX]

In using ARRL Transmission Line for Windows application:

RG-8X  Belden 100 ft @ 50 MHz has 2.5 dB loss

LMR-240 Times Microwave  100 ft @ 50 MHz has 1.7 dB loss

RG -213 Belden 8267 has 1.5 dB loss at 50 MHz

RG-8 Belden 9913 has 0.88 dB loss for 100 ft at 50 MHz.  {Due to the 
nature of this line having a lot of air content, the reason for low 
loss,  it is reported to have moisture condensation issues.   Thus I 
would avoid it for outside use.}


Andrew LDF4-50A which is 1/2" hard line has 0.44 dB loss at 50 MHz

These were just a few I checked.  All values calculated for 100 ft, with 
a 1:1 SWR at 50 MHz.


I would cringe at the thought of putting up a fine antenna and loose any 
performance on transmit and receive due to feed line loss.   In my case 
I have a 4 element HyGain 6M yagi which is fed with about 75 ft of 
Andrew LDF4-50.  I selected the 4 element on a 12 ft boom as opposed to 
the 5 element on a 12 ft boom.   The side lobe pattern on the 4 element 
yagi is much cleaner, hence noise off axis is lessened.


I didn't see any polar response plots on their site so I can't comment 
on overall performance of the 6OWL6.


73

Bob, K4TAX

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Re: [Elecraft] RG-8X

[Bob Gibson via Elecraft]

Richard..If you are set on using the small size the real LMR-240 is the best 
bet..also may want to check with MFJ.. they now carry a very good line of 
coax!! 
    73s Bob W5RG


  From: Richard 
 To: Elecraft Reflector  
 Sent: Monday, February 26, 2018 8:35 AM
 Subject: [Elecraft] RG-8X
   
I’m seeking recommendations for RG-8X coax with the lowest loss. The total run 
will be about 100 feet.

Cheers!

Richard Kunc — W4KBX

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