75 ohm coax, some remedial questions...

[riverrat]

OK, some semi-clueless antenna and cable questions...

I'm starting to prepare for my "decent outdoor antenna" project. Placement options are crimped somewhat by HOA and WAF issues. I'm guessing I will need about a 50' run of coax to reach my tuner, maybe a bit less.

I found a 1000' roll of the following Belden coax cable for sale locally for $20:

Belden 9116 75ohm RG6 MATV coax (also suitable for FM antennas)
#Conductor Material & Diam: 18 AWG solid bare copper covered steel, .040"
# Dielectric Material & Diameter: Gas injected foam polyethylene, .180"
# Shield type: 1st layer - Bonded duofoil, 2nd layer - 60% aluminum braid.
# Jacket Material & Diameter: Polyethylene (Black or Orange), .270"

That is about 20 times as much cable as I need, but I could perhaps unload the rest of it. So my questions are:

1. Is this nice quality coax?
2. Is there any benefit to getting "better" cable? If so, what cable would this be?
3. How easy would it be to hook up a switch box (so I can use more than one tuner) and F-connectors to the bare cable? (Presuming that I'd use the same coax into and out of the switch box.)
4. What kind of switch box do I need and who sells them?
5. Is it pretty straightforward to hook up the cable to the antenna end?

 

[Lefty]

" Belden 9116 75ohm RG6 MATV coax (also suitable for FM antennas)
#Conductor Material & Diam: 18 AWG solid bare copper covered steel, .040"
# Dielectric Material & Diameter: Gas injected foam polyethylene, .180"
# Shield type: 1st layer - Bonded duofoil, 2nd layer - 60% aluminum braid.
# Jacket Material & Diameter: Polyethylene (Black or Orange), .270"

That is about 20 times as much cable as I need, but I could perhaps unload the rest of it. So my questions are:"


1. Is this nice quality coax?

RG-6 cable is very good coax for FM and Belden to a top wire manufacture, grab that cable!

2. Is there any benefit to getting "better" cable? If so, what cable would this be?

Not for the length you require. For long long runs there are lower loss cables that are much thicker in diameter and cost more. However 50ft at FM frequencies work great with RG-6 type cable.

3. How easy would it be to hook up a switch box (so I can use more than one tuner) and F-connectors to the bare cable? (Presuming that I'd use the same coax into and out of the switch box.)

Not too hard with the right connectors. There are solderless 'screw-on' type connectors that can work. Short ready made F to F jumper coax cables are cheap and easy to get (same as TV/VCR/cable jumpers) and work fine for FM that can run from a switch box to each tuner.

4. What kind of switch box do I need and who sells them?

Should be easy to search for F-connector switch boxes, Radio Shack may still carry them. One could use VHF splitters to run connections to each tuner but each splitter causes a 3+db loss (1/2 power) so a switch box is lower signal loss.

5. Is it pretty straightforward to hook up the cable to the antenna end?

Depends on the specific antenna. Some accept a coax connector but most take a 300ohm flat ribbon type cable connection so a balun 300/75 ohm transformer would be required. This is the critical connection as it has to be water proof. The better antennas have this stuff included but these parts and connectors can be purchased seperatly.

Putting money and effort into a good outdoor FM antenna installation is the best bang for the $$ there is. Also consider a rotator if you can afford it unless the station(s) of interest are all coming from the same location...

Lefty

 

[avionic]

Belden 9116 75ohm RG6 MATV coax

Just what the doctor ordered. Then you will need 1 or 2 -300Ω to 75 Ω baluns. You may need one to fasten to the antenna and then another to fasten the coax to your Tuner or reciever unless both ant. and tuner have 75 Ω coax connectors. Radioshack or walmart should have the baluns..Switch box not really necessary just get a 2 or 3 or ? set splitter and additional baluns Balun=impedance matching transformer

Dave

 

[Whitehall]

You'll wind up hating this cable.

Why? The core wire is steel and stiff as heck. The pure copper core stuff is much easier to work with, especially at the tuner end.

 

[riverrat]

You'll wind up hating this cable.

Why? The core wire is steel and stiff as heck. The pure copper core stuff is much easier to work with, especially at the tuner end.

Good tip. Could you suggest a good, inexpensive brand of copper core?

OTOH, perhaps the stiffness issue wouldn't matter as much if I used a more flexible variety of coax between my switch box and my tuners.

I'm thinking of getting something like THIS if you folks can assure me that such units aren't directional. This one (and the others listed on the same page) are made to switch between one source and three different antennas. I would use it the opposite way, to switch one antenna back and forth among two or three different tuners.

I assume this wouldn't matter, but I've learned where assuming usually gets me...

 

[Whitehall]

I doubt you'll find anything like the bargain on the steel core stuff. It will be a hassle during installation and maybe local runs can be on just the copper core stuff.

The copper core does have less resistance and so will give you a stronger signal at the tuner. For 50 feet, it won't make much difference.

I've also noticed a triboelectric effect in some insulation. Bend or cut the cable and you hear static for days. It eventually settles down and I haven't figured out which kind of insulation has this effect and which doesn't.

That switch is for a TRANSMITTER and is way overkill for a tuner. It's rated in KILOwatts and you only need MICROwatts. I bought a Radioshack switch for $5 that does work backwards. Again, here's where the steel core coax will annoy you - you have to screw the switch down.

 

[riverrat]

Thanks whitehall. I'll look into some copper core. I will have enough hassles with this project without bringing new ones on that I can avoid. For the amount I need, I don't think cost will be a big deal.

RE the switch- yes that seemed pretty spendy. I'll try RS first.

 

[avionic]

Nice looking switch but its made for 50 Ω coax RG58 transmission coax big stuff

 

[riverrat]

OK, thanks for helping me refine google search terms. Turned up some more suitable ones using "75 ohm coax switch":

This one specifically says it can be used to switch components, if I'm reading it right.

This one looks like it might work, but doesn't give as many details about applications.

 

[Toka]

riverrat,

One option worth considering is getting a custom-length coax from Blue Jeans Cable. They have several varieties of Belden wire, so you should be able to find one that would work for you. Won't have to worry about terminating it yourself either. They ship like lightning, and if you don't like it, you can send it back. It'll may cost more than going the bulk route, but I'm a sucker for convenience myself.

http://www.bluejeanscable.com/store/rf/index.htm

 

[Whitehall]

Those switches should work.

And don't worry about connections on coax. You can get a $20 stripper and crimper tool and a bag of the connectors and you're in business.