RG-6 Coax

[N_Jay]

"You sure? Why not 300 or 500 ohm for even lower loss?"

How about 600 ohms? You're talking open wire feeder but I like your sarcasm N_Jay. Now here's something for you and it's not sarcasm, have you ever seen 50 ohm open wire coaxial transmission line?

I meant 600 Ohms (fat fingered my original jab, err I mean post)

If I recall, zip cord is about 50 ohms, but you see 50 ohm open transmission line on circuit board traces all the time.

 

[zz0468]

If I recall, zip cord is about 50 ohms...

I also recall zip cord was quite lossy for a balanced line.

 

[N_Jay]

I also recall zip cord was quite lossy for a balanced line.

I didn't say it was good, just that it matched.

Of course that was so long ago, it may have been a different size from today's zip cord with different dielectric.

 

[DaveH]

Yes, but is designed for low loss and NOT power carrying capability.

As I understand it, the outer-inner coax diameter ratio can be
optomized from one of two things: lowest loss (conductors) or
highest power-handling (breakdown voltage). For air dielectric,
the lowest loss ratio yields impedence around 77 ohms. Fill it with a
"good" dielectric like polyethylene (dielectric constant 2.3) and
the impedence drops to about 51 ohms (what a coincidence!).

Now...how does this fit with 73-ohm coax, as far as lowest loss?

Dave

 

[Turbo68]

I use RG-6 on my Centrefire Multi Band Dipole and picks up okay on uhf but vhf is not not good at all and as soon as i change to Belden-9913 which is the same length at 20 metres the radios reception is excellent on vhf/uhf.

Regards Lino.

 

[N_Jay]

I use RG-6 on my Centrefire Multi Band Dipole and picks up okay on uhf but vhf is not not good at all and as soon as i change to Belden-9913 which is the same length at 20 metres the radios reception is excellent on vhf/uhf.

Regards Lino.

Something does not make sense.

 

[DaveH]

As I understand it, the outer-inner coax diameter ratio can be
optomized from one of two things: lowest loss (conductors) or
highest power-handling (breakdown voltage). For air dielectric,
the lowest loss ratio yields impedence around 77 ohms. Fill it with a
"good" dielectric like polyethylene (dielectric constant 2.3) and
the impedence drops to about 51 ohms (what a coincidence!).

Now...how does this fit with 73-ohm coax, as far as lowest loss?

Dave

A minor correction, power-handling and breakdown voltage are two
different cases. Optimal airline impedence for breakdown is 60 ohms
(~40 ohms with poly diel.), and 30 ohms for power-handling (~20 ohms
with poly diel.).

Dave

 

[conve36]

I have been in this hobby for about 2 years and have no friends that are into it...

I have read things online about types of cable to use, and have figured out that it's all about TRIAL AND ERROR.

Try different antennas, cables and scanners. Example: I have read that the RS800Mhz handheld antenna has done wonders for some people monitoring trunking systems. For me I noticed no difference on 800Mhz and noticed greater signal in UHF. Go figure right? I have been using "almost the best" 9913 coaxial cable for my antenna setup. Tried multiple antenna and scanners. They all worked great.

Just 2 days ago I found about 100 feet of RG-6 dish network coaxial cable in my attic. (Has been up there for about 2 years)

I took that cable and a 12 foot whip (thats used for dune buggys) put an american flag on top and zip tied my stock Uniden BC246T antenna to the top and put it on my roof. It stands about 2 feet higher than where my other antennas were...

And found out this seems to be the BEST!! Why? I have no idea...

Some people say dont use RG-6... Some people say it doesnt matter...

My advice is to try different things out for yourself. Sometimes I think thats the most interesting part of it all, trying to see what is the best (or better that what you currently have)