Of course many coaxial cables are used which do not contain silver plated
conductors. Indeed, at low HF frequencies, the depth of penetration into the
surface of the conductor, ie skin depth, is quite shallow, and increases slowly
with increasing frequency. While silver is about 108% IACS conductive, or about
8% more conductive than annealed ETP copper, typical silver plating thicknesses
of a minimum of 40 micro-inches don't really change the sum of the total AC
resistances of the conductor of which skin effect is but one.
At HF, the silver plating really imparts a much improved solderability for the
conductor which is highly desirable during connector installation.
Cables which are designed to offer low structural return loss, SRL, at above
several gigahertz in frequency, are generally always silver plated with heavier
coatings because of the much greater depth of the skin effect. Without the
plating the losses will be greater.
In the gigahertz region, the shield wires become even more important to reduce
structural return losses. Very high quality cables favor shields with flattened
conductors and silver plating. The very thin flat wires provide something close
to a flexible tube in coverage.
All the cables on the McDonnell Douglas F15 Eagle use flattened braidwires,
silver plated. It saves a good deal of weight in the airframe. Most every
modern military aircraft does the same.
The military specs, Mil C 17 type coax, with silver plated conductors, assure
good performance up to 200 degrees centigrade. There are 400,000 connections in
a typical fighter. Many will be crimp terminated and again silver is a good
choice.
No one can afforded a bad connection. Your coax connector benefits also.
73,
Mike
W2AJI
Sent from my iPhone
> On Jun 1, 2014, at 9:18 PM, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net> wrote:
>
> Regarding coaxial cables, RF current flows on the outer skin of the center
> conductor and on the inner skin of the shield. Thus the reason for silver
> plated center conductors and silver plated shield material. As to coaxial
> cable radiation, this is largely dependant on the percentage of shield for
> the specific cable. For that reason, tightly shielded application
> requirements will use double shield silver plated cables such as RG-9. Lines
> made using solid aluminum outer conductor or copper outer conductor are known
> as "hard lines" and offer theoretical 100% shielding.
>
> <quote>
> "The currents in coaxial cable flow on the outside of the center conductor
> and the inside of the outer shield." ARRL Handbook, 2014, page 20.2.
>
> <quote>
> "Common-mode currents are conducted and induced into the outside of the
> shield of the feed line, which in turn radiates." ARRL Handbook, 2014, page
> 20.17
>
> My earlier statement regarding using "a 1:1 common mode choke" is a 1:1
> current balun at the feed point to attain a balanced to unbalanced condition
> for a center fed dipole with a coaxial feed. This is immediately followed by
> a common mode choke at the feed point to account for any natural unbalance of
> the installation.
>
> With a true flat top dipole and the feed line exiting precisely at 90 degrees
> from plane, there is little current induced in the coax feed. However, any
> angle departure from 90 degrees, including that of a so called inverted V,
> is likely to have significant common mode current induced into the feed line.
> With the proliferation of inverted V usage, largely to ease of installation,
> we see a notable increase in common mode current issues.
>
> <quote>
> " Reducing common-mode current on a feed line also reduces:
> * Radiation from the feed line that can distort an antenna's radiation pattern
> * Radiation from the feed line that can cause RFI to nearby devices
> * RF current in the shack and on power line wiring
> * Coupling of noise currents on the feed line to receivers and receiving
> antennas
> * Coupling between different antennas via their feed lines"
> Regarding coaxial cables, RF current flows on the outer skin of the center
> conductor and on the inner skin of the shield. Thus the reason for silver
> plated center conductors and silver plated shield material. As to coaxial
> cable radiation, this is largely dependant on the percentage of shield for
> the specific cable. For that reason, tightly shielded application
> requirements will use double shield silver plated cables such as RG-9. Lines
> made using solid aluminum outer conductor or copper outer conductor are known
> as "hard lines" and offer theoretical 100% shielding.
>
> <quote>
> "The currents in coaxial cable flow on the outside of the center conductor
> and the inside of the outer shield." ARRL Handbook, 2014, page 20.2.
>
> <quote>
> "Common-mode currents are conducted and induced into the outside of the
> shield of the feed line, which in turn radiates." ARRL Handbook, 2014, page
> 20.17
>
> My earlier statement regarding using "a 1:1 common mode choke" is a 1:1
> current balun at the feed point to attain a balanced to unbalanced condition
> for a center fed dipole with a coaxial feed. This is immediately followed by
> a common mode choke at the feed point to account for any natural unbalance of
> the installation.
>
> With a true flat top dipole and the feed line exiting precisely at 90 degrees
> from plane, there is little current induced in the coax feed. However, any
> angle departure from 90 degrees, including that of a so called inverted V,
> is likely to have significant common mode current induced into the feed line.
> With the proliferation of inverted V usage, largely to ease of installation,
> we see a notable increase in common mode current issues.
>
> <quote>
> " Reducing common-mode current on a feed line also reduces:
> * Radiation from the feed line that can distort an antenna's radiation pattern
> * Radiation from the feed line that can cause RFI to nearby devices
> * RF current in the shack and on power line wiring
> * Coupling of noise currents on the feed line to receivers and receiving
> antennas
> * Coupling between different antennas via their feed lines"
> ARRL Handbook, 2014, page 20-18
>
>
>
> 73
> Bob, K4TAX
>
>
>
>
>
> ----- Original Message ----- From: "Mike Schatzberg"
> <cherokeehillfarm@earthlink.net>
> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
> Sent: Sunday, June 01, 2014 5:13 PM
> Subject: Re: [TenTec] Trading radios
>
>
>> What I said was:
>>
>> "With good quality cable, the center conductor is not radiating. However,
>> the shield may indeed be carrying current."
>>
>> I don't think you have my meaning and have taken it out of context.
>>
>> The percentage of braid coverage, the use of foils under the braid, double
>> braids, and aspects of the cable insulation and geometry, can be factors in
>> radiation. The common mode current can still be an issue, due to the
>> direction of the cable run and it's length with regard to frequency.
>>
>> If you believe that there are no differences in various types of 50 ohm
>> coax, with regard to radiation from the cable, this does not agree with my
>> experience.
>>
>> 73,
>>
>> Mike
>> W2AJI
>>
>> Sent from my iPhone
>>
>>> On Jun 1, 2014, at 3:59 PM, "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de> wrote:
>>>
>>> Mike is doing it CORRECTLY.
>>>
>>> My only comment is, the quality of the coax plays NO ROLE in this.
>>> CMC flows on the outside of the coax shield so it makes no difference if you
>>> are using the best or the worst coax in the world - (as far as CMC is
>>> concerned; of course you should use good coax for other reasons).
>>>
>>> 73 - Rick, DJ0IP
>>> (Nr. Frankfurt am Main)
>>>
>>>
>>> -----Original Message-----
>>> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Mike
>>> Schatzberg
>>> Sent: Sunday, June 01, 2014 7:39 PM
>>> To: Discussion of Ten-Tec Equipment
>>> Subject: Re: [TenTec] Trading radios
>>>
>>> In my case the RF is radiated from my Yagi and the coax shield picks up the
>>> radiation between the antenna feed point and the radio.
>>>
>>> With good quality cable, the center conductor is not radiating. However,
>>> the shield may indeed be carrying current.
>>>
>>> Stations with RFI often only experience interference with their directional
>>> arrays with the antenna in a certain alignment with their cable.
>>>
>>> I use a 1:1 current balun at my Yagi hairpin feed point, and the line
>>> isolator at the input to my amplifier, between it and the Orion II.
>>>
>>> Seems to work well with all the radios here.
>>>
>>> 73,
>>>
>>> Mike
>>> W2AJI
>>>
>>> Sent from my iPhone
>>>
>>>> On Jun 1, 2014, at 12:42 PM,k4elo@fastmail.fm wrote:
>>>>
>>>> Disagree Bob. Put the choke at the feedpoint of the antenna or your
>>>> coax will be radiating rf all the way down to the rig. If you can't
>>>> move the antenna, this is the most effective rfi fix.
>>>>
>>>> 73
>>>> Wayne
>>>> K4ELO
>>>>
>>>>
>>>>
>>>>> For starters, as to RFI issues, yes antenna to radio spacing,
>>>>> increasing same, will usually improve the issue. Be sure all equipment
>>> is each
>>>>> bonded to a common point such as the PS ground. Omit the external
>>>>> ground but keep 3rd pin ground intact. Use a common mode choke on the
>>>>> output of the radio.
>>>>>
>>>>> 73
>>>>> Bob K4TAX
>>>> _______________________________________________
>>>> TenTec mailing list
>>>> TenTec@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/tentec
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>>
>> Sent from my iPhone
>>
>>> On Jun 1, 2014, at 3:59 PM, "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de> wrote:
>>>
>>> Mike is doing it CORRECTLY.
>>>
>>> My only comment is, the quality of the coax plays NO ROLE in this.
>>> CMC flows on the outside of the coax shield so it makes no difference if you
>>> are using the best or the worst coax in the world - (as far as CMC is
>>> concerned; of course you should use good coax for other reasons).
>>>
>>> 73 - Rick, DJ0IP
>>> (Nr. Frankfurt am Main)
>>>
>>>
>>> -----Original Message-----
>>> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Mike
>>> Schatzberg
>>> Sent: Sunday, June 01, 2014 7:39 PM
>>> To: Discussion of Ten-Tec Equipment
>>> Subject: Re: [TenTec] Trading radios
>>>
>>> In my case the RF is radiated from my Yagi and the coax shield picks up the
>>> radiation between the antenna feed point and the radio.
>>>
>>> With good quality cable, the center conductor is not radiating. However,
>>> the shield may indeed be carrying current.
>>>
>>> Stations with RFI often only experience interference with their directional
>>> arrays with the antenna in a certain alignment with their cable.
>>>
>>> I use a 1:1 current balun at my Yagi hairpin feed point, and the line
>>> isolator at the input to my amplifier, between it and the Orion II.
>>>
>>> Seems to work well with all the radios here.
>>>
>>> 73,
>>>
>>> Mike
>>> W2AJI
>>>
>>> Sent from my iPhone
>>>
>>>> On Jun 1, 2014, at 12:42 PM, k4elo@fastmail.fm wrote:
>>>>
>>>> Disagree Bob. Put the choke at the feedpoint of the antenna or your
>>>> coax will be radiating rf all the way down to the rig. If you can't
>>>> move the antenna, this is the most effective rfi fix.
>>>>
>>>> 73
>>>> Wayne
>>>> K4ELO
>>>>
>>>>
>>>>
>>>>> For starters, as to RFI issues, yes antenna to radio spacing,
>>>>> increasing same, will usually improve the issue. Be sure all equipment
>>> is each
>>>>> bonded to a common point such as the PS ground. Omit the external
>>>>> ground but keep 3rd pin ground intact. Use a common mode choke on the
>>>>> output of the radio.
>>>>>
>>>>> 73
>>>>> Bob K4TAX
>>>> _______________________________________________
>>>> TenTec mailing list
>>>> TenTec@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/tentec
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>> _______________________________________________
>> TenTec mailing list
>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
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