Want to replace old flat tv cable with better coax.

[Ralph Mowery]

Coiling up extra coax wil not make it like a RF choke and will not lower the signal level. As long as the coil diameter is large enough that the center conductor does not cut into the iner insulation and short to the shield, nothing on the outside of the coax will affect the strength of the signal. The signal is carried on the inside of the outer shield. Coil up all the extra you want. One thing that will affect the signal is if you have way too much coiled up (like 20 or more feet) is the extra loss in the length of coax. YOu will get the same ammount of loss if it is coiled or just ran in a line.

If you are transmitting , coiling up the coax may have a benifit as it will act as a choke and keep the transmitted rf that is coupled from the antenna from getting back to the transmitter. Discussion on this is beyond the TV application and not needed here.

[mm]

You sound like you know what you're talking about, but one thing gets me. Here you say it will act as a choke and at the start of the previous paragraph you say it won't. Why does transmission have a different result from reception, or is there some other difference?

Remove NOPSAM to email me. Please let me know if you have posted also.

[garyarnold]

That's it.

[Ralph Mowery]

I have been a ham radio operator for over 30 years and at one time held a first class phone license that was good for the comercial radio repair.

When receiving the signal comes from the antenna it comes down on the outside of the inner wire and the inside of the outer sheild. Unlike Direct current which uses all the wire area, as the frequency goes up, the signal only uses part of the area. That is a copper tube can carry just as much signal as a solid wire the same diameter. Large coax (usually called hardline) is often made this way. There is nothing useful on the outside of the shield of the coax. In otherwords everything from the receiving antenna is on the inside of the coax and coiling it up has no effect .

When transmiting it is possiable that some of the signal from the antenna will couple or be introduced on the outside of the coax. This unwanted signal will come back down the coax on the outside of the shield and can cause problems with the transmitter and other electronics in the house. If the coax is wound in a coil it may choke off this unwanted signal. The coil is usually placed outside the house .

[jg]

Ok, so is it possible to have both my current antenna pointed in one direction (minus the UHF section) and use this new antenna pointed in a different direction? Then just combine the signal? This would give me the best of both world w/o the need for a rotor.

[jg]

You seem to know a lot. Here's a question, if my mast is well grounded (buried a few feet) do I still need to ground the coax before it enters the house? The way I see it, the mast will dissipate any charge on the antenna? Yes?

[HFguy]

Not sure who you are addressing, but the shield of the coax does need to be grounded before entering the house. This is regardless of whether the antenna mast is grounded, but it should be. I would run a copper ground wire, at least 12-gauge, from a clamp on the antenna mast to a good copper clad ground rod. Connect the shield of the coax to this ground wire too. You can use a coax grounding 'block' to make the shield connection to the ground wire. This block is the kind that cable TV companies use to ground their coax before it enters the house. You can buy one at Radio Shack or hardware stores with coax parts.

[Mark Zenier]

Sure. Back in the dark ages, when the UHF channels went up to Channel

83, TV sets didn't have a combined antenna input, instead they had two (usually 300 ohm) inputs, one for each band. To save cable, VHF/UHF splitter/combiners were used if you had an all band antenna. They're bidirectional, the same unit can be used either way. So you can run two antennas into the one cable.

Mark Zenier [e-mail] Googleproofaddress(account:mzenier provider:eskimo domain:com)

[jg]

Thanx to all who replied and helped out. I've installed a balun tranformer at the antenna and I've replaced the entire run with RJ6 coax cable. Picture quality increased drastically on all channels. I've got my antenna pointing 206 degrees yet I can still pick up channels 29 (103 degrees) and 19 (143 degrees.) (My antenna's fault I'm sure.) At any rate the local stations (Sacramento) all come in super clear, so I'll leave it as it is.

Thanx again.

[Ralph Mowery]

I try not to give advice on lightning protection. For about 25 years I had a tower up about 40 feet and never took a hit of any kind. The tower was not very well grounded and there were about 6 coax cables from various ham antennas coming into the radio room. None were grounded . There was also a wire about 130 feet long split in the middle and coax comming into the radio room. It was up about 30 feet and not grounded in any way. Only damage I ever took was a couple of telephones over the phone line. The installation was done by the phone company and I never looked at it to see how well it was done. Others I have know had well grounded systems and still had their equipment wiped out by lightning.

[HFguy]

The antenna's 'fault' proved to be a benefit in your situation. Sometimes it's better to have an antenna like yours which has less gain (sensitivity) for weak stations but a wider beamwidth, so you can receive stations from different directions without needing a rotator. It's a trade-off that sometimes pays off. Nice work.

[Brian O]

If you ever get the urge, buy a good long distance antenna and put a rotor on it and see what you get! B