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

[Ulrich Weiss]

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