question about RG6

[davidgcet]

and drawing from your post, the antenna is not resonant across all frequencies. the impedence of the coax itself does not change across them, but due to other parts of the circuit being off impendence anyway it becomes MUCH LESS critical than it would be in a tuned band setup, though certainly if all parts of the circuit are 50ohm components there will be a little less variance. and yes, i've swept antennas across multiple bands and watched as they swung from 40ohm-60ohm or more when out of designed band. so i see and agree with what you are saying about the antenna portion of the circuit.

what i meant by "it is not", is that there is no other reason besides cost/availability to use it over a proper 50 ohm cable. i just did not know if there was some trick folks were doing that made the 75 ohm cable pass more signal. sure a good shield RG6 has less loss than RG58, but if the run is long enough for this really matter then technically for least loss you want a larger cable than either of these anyway especially if you are dealing primarily with UHF and higher freqs.

like i said, i was not trying to start any arguements here. i was just asking a question.

 

[GTR8000]

I think it's fairly obvious to anyone who has a basic understanding of RF that RG8 will outperform even the best RG6. That's not really a fair comparison, for obvious reasons. Maybe a better head-to-head comparison for receive-only 50 ohm vs 75 ohm would be RG8X vs RG6 or RG8 vs RG11.

Or better yet, just compare LMR400 with LMR400-75. Per Times' own published specs, the 75 ohm version has a bit less loss than the 50 ohm version. It's certainly not enough of a difference to have much real world impact, but it does show that if nothing else, RG8 and RG11 are just about equal in that aspect.

Since RG6 and RG11 are easier to obtain and cheaper than 50 ohm variants, they make a fine choice of coax for wideband receive-only applications. Yes, that's probably the overwhelming reason people would choose it over 50 ohm, however a good quad shield RG6 like Belden 7916A not only gives you low loss but also the extra shielding, which can make a difference in RFI/EMI rich environments for a measly 16 cents per foot.

 

[DPD1]

The thing that has to be taken into consideration most, is just the inherent added stuff you have to do to use a 75 ohm cable. F adapters aren't plentiful, and the more connections and other stuff you have in the line, the more things there are to create loss and fail in time. Yes, some makers have just used F connectors or a matching device (even more loss) to begin with, because they know people are going to try and use the 75 ohm stuff anyway. But at some point, it starts being a cart in front of the horse.

 

[jackj]

Gentlemen, it's time to drop this. Nobody is going to change their mind because of what is said here but some tempers might flare. Scanner monitoring is a hobby and both 75 and 50 ohm cable will work as feedline so it really doesn't make any difference except to the purist.

 

[GTR8000]

The thing that has to be taken into consideration most, is just the inherent added stuff you have to do to use a 75 ohm cable. F adapters aren't plentiful, and the more connections and other stuff you have in the line, the more things there are to create loss and fail in time. Yes, some makers have just used F connectors or a matching device (even more loss) to begin with, because they know people are going to try and use the 75 ohm stuff anyway. But at some point, it starts being a cart in front of the horse.

You might be surprised at how plentiful and easy to find F adapters are. F to BNC, F to N, F to UHF, etc etc etc. You can readily find them online, including outfits that sell quality stuff like Tessco, L-Com, Mouser, et al. Perhaps you just haven't looked around lately, or have no reason to, but they are out there in spades.

Incidentally, on my Belden 7916A QS RG6, I have a BNC compression connector on the scanner side, and an N connector on the antenna side. No adapters whatsoever, just the native connectors designed for RG6. In case you're wondering, both connectors are in fact 50 ohm, so I hope that doesn't make anyone's head explode given the abhorrent impedance mismatch! :twisted:

Gentlemen, it's time to drop this. Nobody is going to change their mind because of what is said here but some tempers might flare. Scanner monitoring is a hobby and both 75 and 50 ohm cable will work as feedline so it really doesn't make any difference except to the purist.

Last I checked, this is a discussion forum. We are all adults here...well, mostly all...and I see no tempers flaring. The man asked a legitimate question, and is entitled to hear feedback from a variety of users on the topic. If you're tired of the topic being discussed ad nauseum, or you feel that your post is the only answer on the matter, then walk away. No one is forcing you to participate in the discussion. It really is off putting having someone think they can tell the rest of us when they feel it's time to drop something. :wink:

 

[smason]

i honestly was wondering if there was a valid reason beyond it being at hand. and now i know there is not.

But there is. Lower loss, less expensive, more available.

 

[CalebATC]

But there is. Lower loss, less expensive, more available.

That's what I would say, and like someone else said, the connectors are very cheap, available, and they aren't hard to find.