Topband: Measured RG-6 Loss: Solid Copper vs. Copper Clad center conductor

[donovanf at starpower.net]

Uli,

A very important lesson about CCS RG-6 has been communicated to topbanders by you and several others who have had bad experiences.  Thanks for taking the time to describe your unfortunate experience in detail.

When purchasing copper clad steel RG-6, its very important to immediately test its loss characteristics.  It appears that some unscrupulous suppliers are selling factory rejected RG-6 or selling RG-6 from unreliable manufacturers.  We should be careful to purchase from trusted suppliers, on ebay they will be suppliers with 100% positive feedback.

Its easy to use an MFJ-259 to quickly check cable loss, using its cable loss mode.  Its more accurate if you build or purchase a simple 50:75 ohm broadband matching transformer.

73
Frank
W3LPL


---- Original message ----
>Date: Fri, 25 Jan 2013 12:21:48 +0100
>From: "Ulrich Weiss" <dj2ya at t-online.de>  
>Subject: Re: Topband: Measured RG-6 Loss: Solid Copper vs. Copper Clad center conductor  
>To: <donovanf at starpower.net>, "topband" <topband at contesting.com>
>
>hi Frank et al.
>
>preparing our last year's CR3L contest activity in the CQWW-CW, we wanted to 
>try a remote RX-antenna to work in-band multipliers as DM6V in the 
>WAG-contest at DL5AXX's qth... naively following the formula that quartering 
>the frequency will half the attenuation Ulf ordered 500m of 75 Ohm CCS -TV 
>coax promising about 15db loss at 500MHz per 100m... the calculated loss of 
>about 10db for the Windom 400 m away was expected to be tolerable for our 
>purpose...
>when we didn't hear literally anything on our RX-antenna we first thought of 
>a faulty connector, but the SWR, totally flat at 1.5 (75 ohms) from 160 to 
>10m, made us suspicious and measuring the SWR into one (unbroken) 100m piece 
>(open at the end) showed that the cable was responsible for the high 
>losses... when taking a 100m bobin home for more exact measurements, at 30 
>MHz the attenuation was measured as 17db at 14MHz, 15 db and 8 db at 1.8 MHz 
>... no wonder that we couldn't hear anything at the end of the 400m feed 
>line... as at 100 MHz the attenuation was 19.5 db, well above the promised 
>15 db at 500 MHz, we returned the cable to the distributor and hoped for 
>reimbursement...
>to be fair, the cable was very cheap (< 20 EUR/100m) and we simply had to 
>pay the price for saving the wrong way...
>we were almost determined to order 500m of H155 and pay a lot of money when 
>I found a promising CCS-TV-cable in the catalogue of another distributor in 
>Germany... at the price of EUR 25/100m the catalogue specified an 
>attenuation of 5,64 db/100m and I had another try... with 6.1 db at 100 MHz 
>it was pretty close to specifications and the losses (measured with my 
>miniVNA ) for 100 m were 4,8 db on 30 MHz , 4.4 db  on 14 MHz and 3.3 db 1.8 
>MHz , not very far away what you listed in the table in a recent e-mail and 
>clearly better than the expensive H155 we were going to buy at three times 
>the price...
>CONCLUSION: there are enormous differences in the quality of  75 ohms-CCS-TV 
>cables in the low price segment here in Germany (presumably all made in 
>China)... TV-cables are very rarely specified as RG-6 here and I wonder if 
>there are standard specifications for RG-6 just as for RG-58 or RG-213 
>etc.... furthermore we learned (the hard way) that - obviously due to the 
>characteristics of CCS-wire - the attenuation/frequency ratio is very 
>different from that of our common 50 ohm coax with inner conductors of solid 
>(or stranded) copper... before ordering a long run of TV-cable first I'll 
>always try a sample...
>hoping that our experience will perhaps prevent others from making the same 
>mistake...
>
>73
>
>Uli, DJ2YA
>
>----- Original Message ----- 
>From: <donovanf at starpower.net>
>To: "topband" <topband at contesting.com>
>Sent: Thursday, January 24, 2013 3:28 AM
>Subject: Re: Topband: Measured RG-6 Loss: Solid Copper vs. Copper Clad 
>center conductor
>
>
>> Hi Mike,
>>
>> Obviously I had computers on my mind...
>>
>> Yes, of course I meant to say quad-shield RG-6 CATV cable.   I'll provide 
>> the manufacturers and part numbers in a subsequent e-mail, but its just 
>> typical inexpensive ebay RG-6 CATV cable.
>>
>> Inexpensive RG-6 with a copper clad steel (CCS) center conductor is much 
>> more widely available than solid copper, especially in desirable options 
>> such as a tough polyethylene (PE) jacket and flooded RG-6.  CCS looks like 
>> a reasonable choice except for very long cable runs on 160 and 80 meters. 
>> A copper clad center conductor may be a problem if a device (e.g. a preamp 
>> or relay) is remotely powered through the coaxial cable.
>>
>> 73
>> Frank
>> W3LPL
>
>