Low loss TV coax

[N2RJ]

I want to know what options I have for low loss 75 ohm coax. The reason I am asking is because the run from my tv antenna atop the tower to the TV is going to be approximately 170ft. Since it is at UHF I don't think I want to use RG6 because I will lose all of my signal.

Any suggestions?

Steve (ATS) - what kind of 75 ohm hardline is available? I've not seen much in the way of 75 ohm hardline although I was told that CATV companies have it in abundance.

I would like to be able to watch TV OTA if the cable company goes off air for any reason. Maybe even cut the TV portion of my cable bill too. Honestly 99% of what I watch is from local networks.

[W4KLB]

:D cable co hard line is 75 ohm at least for the first 100 ft, i have used 50 ohm at 180 ft with good results, what ever you can get the chepest should work or call aes and get some 8213 same size as rg8u 8)

73

Probably be best to down convert with a receiver up top and use a cheap coax after amplification on channel 2.

[K8YS]

around here, TimeWarner used two types of hard line, .500 inch and .750 inch. The Cincinnati Repeater Association uses .750 on the WCPO and WKRC towers (over 800 feet each) with great success. The former president, chief Engineer, and all around all knowing W8HQQ, made adapters that went from UHF or N to 3/4inch pipe. He used common plumbing pieces, he would insert the RF connector in the 1/2 to 3/4 copper transition piece, then threaded the hard line, screwed the copper piece on the hard line and securely fixed the terminated end to minimize bimetal shrinkage.

The same could be done fitting .500 into a PL-259 by drilling it out and pressing the hard line into the connector, secure with a hose clamp.

around here, TimeWarner used two types of hard line, .500 inch and .750 inch. The Cincinnati Repeater Association uses .750 on the WCPO and WKRC towers (over 800 feet each) with great success. The former president, chief Engineer, and all around all knowing W8HQQ, made adapters that went from UHF or N to 3/4inch pipe. He used common plumbing pieces, he would insert the RF connector in the 1/2 to 3/4 copper transition piece, then threaded the hard line, screwed the copper piece on the hard line and securely fixed the terminated end to minimize bimetal shrinkage.

The same could be done fitting .500 into a PL-259 by drilling it out and pressing the hard line into the connector, secure with a hose clamp.

When they report great success, what frequencies are they up to when they claim this? I'm ignorant as to what this frequency is.

[N3ATS]

I want to know what options I have for low loss 75 ohm coax. The reason I am asking is because the run from my tv antenna atop the tower to the TV is going to be approximately 170ft. Since it is at UHF I don't think I want to use RG6 because I will lose all of my signal.

Any suggestions?

Steve (ATS) - what kind of 75 ohm hardline is available? I've not seen much in the way of 75 ohm hardline although I was told that CATV companies have it in abundance.

I would like to be able to watch TV OTA if the cable company goes off air for any reason. Maybe even cut the TV portion of my cable bill too. Honestly 99% of what I watch is from local networks.


Andrew makes a 1/2" 75 ohm cable model # LDF4-75A.

CommScope might, but I am not familiar. For that length of run you would be better off with a tower top amp (TTA). But be aware that cheap broadband amps are noisy as hell. Good ones are expensive.

CATV Co's use aluminum cable, probably CommScope brand. It's generally a smooth outer jacket about 5/8" in diameter from what I've seen. Not too familiar with the CATV world.

[N2NH]

Ryan, are you running the feedline on the ground? If you can, you might be able to run it on an angle from the shack to a point 1/2 way up or higher on the tower. This would shorten the feedline a lot.

http://i24.tinypic.com/2rpcgat.jpg

[kb2vxa]

Uh oh, running feedline in catenary fashion is asking for trouble. First of all you must provide strain relief in the form of a suspensor cable or the coax will stretch which will upset it's electrical characteristics. That's why CATV drop cable has one molded in. Then too it provides a nice path for lightning to follow into the house, that's why coax is normally run inside the tower to the ground and the shield(s) grounded to the tower base.

Although expensive a CATV DA provides typically up to 30dB low noise amplification with variable tilt (higher amplification on higher frequencies) which would make common RG-6 quad shield the coax of choice. If buying one from a CATV equipment manufacturer is too steep a bit of scrounging can always turn one up, I've even seen a few at hamfests. FYI, the tilt is adjusted to compensate for coax loss vs. frequency so you have equal signal levels across the board on the far end, you don't want overload on the bottom channels and snow on the top.

[K8YS]

around here, TimeWarner used two types of hard line, .500 inch and .750 inch. The Cincinnati Repeater Association uses .750 on the WCPO and WKRC towers (over 800 feet each) with great success. The former president, chief Engineer, and all around all knowing W8HQQ, made adapters that went from UHF or N to 3/4inch pipe. He used common plumbing pieces, he would insert the RF connector in the 1/2 to 3/4 copper transition piece, then threaded the hard line, screwed the copper piece on the hard line and securely fixed the terminated end to minimize bimetal shrinkage.

The same could be done fitting .500 into a PL-259 by drilling it out and pressing the hard line into the connector, secure with a hose clamp.

When they report great success, what frequencies are they up to when they claim this? I'm ignorant as to what this frequency is.

the VHF repeaters and the UHF repeater. But hey, there is no SWR - zippo, nadda, none! At a 900 foot run, all the power goes up and nothing can be measured reflected. OK, so it is noit as good as the 6 1/8 inch feed line that they replaced, but after we sold the 6.25 to WCET, we took that money and bought two new Motorola MSR2000's off the shelf as well as two contolers and DVR. WCET got a deal since the feed line was already inplace and we got new toys.

A problem with pulling 900 feet up the tower, the center conductor expands and contracts at a different rate as the outer shell, so if this is not taken into consideration, and adapter for, you can have problems. I have never seen a 900 foot horizontal run, so in CATV service, shrinkage is not an issue.

[K8YS]

Ryan, are you running the feedline on the ground? If you can, you might be able to run it on an angle from the shack to a point 1/2 way up or higher on the tower. This would shorten the feedline a lot.


you are going to need a messenger cable, probably a chinese finger pull at the top of the bend too.

[N2RJ]

Probably be best to down convert with a receiver up top and use a cheap coax after amplification on channel 2.

Good idea, but not gonna happen with digital TV.

[N2RJ]

Ryan, are you running the feedline on the ground? If you can, you might be able to run it on an angle from the shack to a point 1/2 way up or higher on the tower. This would shorten the feedline a lot.

http://i24.tinypic.com/2rpcgat.jpg

Not gonna happen. Where the tower is located, I don't want any coax running in the air, especially if it's hardline. The reason is that I'll have equipment crossing and I don't want that to cause a complication.

I could get away with that for 300 ohm ribbon feed though.

[N2RJ]

So here are my new questions now.

Is it worth it to run hardline? From all appearances, the answer may be no. Part of my motivation is to cut my cable bill, however, so it may pay for itself. But I don't want to break the bank for a TV antenna. Ham antennas I spare no expense, but this is a TV antenna.

The reason I want low loss is because I will be receiving from transmitters 40+ miles away, on UHF (digital TV). Will I really gain (or rather, not lose) that much from low loss coax? My gut says yes, but will it be make or break? I am aware that dB loss is logarithmic and isn't as dramatic for a weak signal as it is for transferring power at a higher level (i.e. received signal loss won't be as dramatic as transmitted power loss).

I want to try to NOT use a pre-amp, reason being that the cheap ones can oscillate and also they tend to be interfered with (desensed) by ham transmissions.

I think I'll take a trip to our local cable co one morning to see if they have any reel ends.

So here are my new questions now.

Is it worth it to run hardline? From all appearances, the answer may be no. Part of my motivation is to cut my cable bill, however, so it may pay for itself. But I don't want to break the bank for a TV antenna. Ham antennas I spare no expense, but this is a TV antenna.

The reason I want low loss is because I will be receiving from transmitters 40+ miles away, on UHF (digital TV). Will I really gain (or rather, not lose) that much from low loss coax? My gut says yes, but will it be make or break? I am aware that dB loss is logarithmic and isn't as dramatic for a weak signal as it is for transferring power at a higher level (i.e. received signal loss won't be as dramatic as transmitted power loss).

I want to try to NOT use a pre-amp, reason being that the cheap ones can oscillate and also they tend to be interfered with (desensed) by ham transmissions.

I think I'll take a trip to our local cable co one morning to see if they have any reel ends.

No, I was not recommending a pre-amp. I was recommending a downconverter. There is a difference.

[kb2vxa]

"I could get away with that for 300 ohm ribbon feed though."

Ryan, you hit upon an idea! Instead of ribbon line subject to the usual upsets caused by rain and worse yet when coated with ice why not open wire ladder line? I once used it on a run about as long as yours in a deep fringe area in Pennsylvania, interesting stuff with glass spacers molded on made specifically for TV reception. Sorry, I have no idea where you could get it around here, I only saw it once up in the Poconos but maybe a web search? Hey, you should have seen me up in a tall pine with a chainsaw in one hand and hanging on for dear life with the other! Well, when all was said and done that tree sported a BMF antenna and rotor, TV and FM reception from New York, Philadelphia and Scranton was pretty darn good for the distance, especially since he's down in a valley.

[N2RJ]

You didn't mention where the stations you most want to receive are located. If they're all in the same general direction, i.e. metro NYC, you may want to consider spending comparatively more on the antenna and less on the feed line. For example, the difference in cost between new RG-11 and LMR 500 over a 200 ft run is over $120, for a 6.2 dB improvement in signal strength. I'll bet spending half that much on a better TV antenna will give you that much improvement, plus improved SNR at the receiver.

If you can get the hardline for free, then the equation changes, but now you've got to spend time and effort handling hardline, and either making connectors or giving blood to be able to afford commercial ones.

They're in NYC. I don't think there's anything else in this area I need to watch. Just the big four plus CW and MY9 and PBS.

I'm already going to max out the antenna - Winegard 9095p corner reflector.

Hardline is no big deal. I have dealt with it for my HF and VHF/UHF amateur aerials.

[HUGH]

The reason I want low loss is because I will be receiving from transmitters 40+ miles away, on UHF (digital TV). Will I really gain (or rather, not lose) that much from low loss coax? My gut says yes, but will it be make or break? I am aware that dB loss is logarithmic and isn't as dramatic for a weak signal as it is for transferring power at a higher level (i.e. received signal loss won't be as dramatic as transmitted power loss).

Ryan: I use 75 ohm TV satellite cable for nearly everything including UHF TV. It's often listed as "CT100" here. The only downside is that the polyethylene insulation is semi-airspaced so can allow water ingress but the PVC sheath is tough.
Centre conductor is solid copper 1mm dia, screen 100% 0.5mm aluminium with copper braid over, overall diameter 6.6mm, 52pF/m, loss 20dB per 100m (325ft)at 1000MHz, velocity factor 82%. I would think there is a US equivalent.
Cost is equivalent to $30 per 100m (325ft).

[N2RJ]

Where do you get it?

Still waiting on the warm weather to put up the antenna.

[HUGH]

It looks as though the only equivalent to CT100, FW100 etc. in the US is RG6. I expect many will throw up their hands in horror because RG6 seems to be extremely variable in quality and construction. Perhaps if you visit your local cable or satellite TV installer you might acquire some for free.
There do seem to be some US suppliers selling RG6 specifically as satellite cable and some even specify it's construction and specifications. I'd certainly like to see it first and cut a sample from the end.

Good hunting!

[N2RJ]

Well if RG6 is what you're talking about, I'll just use RG11 instead.