RG6 or RG8?

Discuss commercial and home made antennas.
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Kev7274
Posts: 8
Joined: Sat Apr 20, 2019 7:23 pm

RG6 or RG8?

Post by Kev7274 » Sun Apr 28, 2019 10:53 pm

Since I will only be listening to my local Trunked P25 system and not transmitting, will RG6 enough? My run will only be around 25-30 feet from the discone and the laptop. Is 50 or 75 ohm going to make a difference?

rtlsdrblog
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Re: RG6 or RG8?

Post by rtlsdrblog » Sun Apr 28, 2019 11:56 pm

RG6 will be more than good enough. The impedance mismatch isn't going to cause much additional loss.

snn47
Posts: 192
Joined: Tue Dec 27, 2016 11:00 pm

Re: RG6 or RG8?

Post by snn47 » Tue Apr 30, 2019 8:04 am

There are different versions of RG-6 (foam dielectricum) and RG-8 see (solid dielectricum) https://en.wikipedia.org/wiki/Coaxial_cable, which can have mechanical problems or due to heat over time.
The difference can be more than 2 dB at 400 MHz for 100 ft, and increase with frequency, but it depends on the version of RG-8xx or RG-6xx coax you buy..

Since the sticks were built for TV use one can assume that they have 75 Ohm impedance as well. but so far I have not seen any mention of impedance of the sticks.

Kev7274
Posts: 8
Joined: Sat Apr 20, 2019 7:23 pm

Re: RG6 or RG8?

Post by Kev7274 » Tue Apr 30, 2019 9:18 pm

Thanks for the info,I appreciate it.

Kev7274
Posts: 8
Joined: Sat Apr 20, 2019 7:23 pm

Re: RG6 or RG8?

Post by Kev7274 » Wed May 01, 2019 1:15 am

I just found some Perfect Vision E341555 RG6,but I believe its Copper Clad Steel. Would this work for the short run or should I stick to solid copper?

snn47
Posts: 192
Joined: Tue Dec 27, 2016 11:00 pm

Re: RG6 or RG8?

Post by snn47 » Wed May 01, 2019 8:20 am

While there a several RG6 type coax on the perfect vision webpage https://www.perfect-vision.com/WebStore ... &menu=intl I could not find the number you referenced.

RG-6 and RG-8 coax differs in addition to the attenuation, which depends on the dielectricum (air, foam, solid material) between center conductur and the outer shield. The the outer shield density also defines the shielding factor, how much of a signal is radiated/is coupling into the cable even if you have connected the cable not to an antenna but to an shielded termination (resistor). Even though the dimensions are identical, cheap cable differes in quality, which you cannot see unless you cut it open. The cheapest ones cut corner by using only a few strands of wire for shielding, while good ones have really dense (double layer) webbing or add a foil below the outer webbing layer.

There are also other SATTV coax cable available for F-connecter which may be an alternative.

Coax exists also with solid cooper shielding like cellflex or flex-well, which are available bu to several inch in diameter and more much more expensive.

Kev7274
Posts: 8
Joined: Sat Apr 20, 2019 7:23 pm

Re: RG6 or RG8?

Post by Kev7274 » Thu May 02, 2019 1:19 am

I got around to cutting a piece and it looked to have very good braid and it does appear to be solid copper. Here's the info on the jacket....Perfect Vision RG6-4 75 OHM High Performance 3.0 GHZ Digital CATV Cable 18 AWG 75 Degree C E341555 (UL) CM

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