Cutting the cable in Cardiff, CA

[Clint]

OK - I'm ready to cut the cable. I've been getting as much information as possible from the Web. Just when I think I know the steps to take, I read a bit more and have doubts about whether I really know what I need to know.

I have a couple of questions. I tried to include all the details that you might need to know to provide advice. I apologize if this post is a bit long.

(Note: I posted a similar question on another web site, and the only real response was from a sales tech at an antenna company, recommending one of their antennas. This site - TV Fool - looks like it might be a better place to get some advice.)

Here is the report from TV Fool on the stations in my area.

http://www.tvfool.com/?option=com_wr...5134c93faf0239

I want to receive the first seven stations on the list. Three are clustered on a mountain in La Jolla about 13 ½ miles away with NM ranging between 30 and 59 dB. The other four are clustered on a mountain about 30 ½ miles away with NM ranging between 28 and 32 dB. The azimuth difference between the two mountains is about 35°. (If I can get the 8th channel - CW which is broadcast from a transmitter in Tijuana - that would be nice, but not imperative.)

One error about the TV Fool report: I don't have line-of-site to the closer mountain. You'd have to be about 15 or 20 feet above the peak of my roof to have line of site. There is a small ridge about 250 yards south of me. The ridge itself doesn't block line of sight from my roof, but houses and trees on the ridge rise up high enough to block my line of sight. So I don't have true LOS with either of the clusters of transmitters. I suspect that TV Fool's map software is looking at the elevation of the earth and isn't accounting for the elevation of houses and trees. My actual NM for each station is probably a bit lower than TV Fool's estimate.

I want to mount an antenna in the attic for two reasons: Avoid having to ground it; and if the antenna is on the roof it may corrode quickly - because I do have line-of-sight to the ocean. The Pacific about 1000 yards due west of my house and metal that is left outside doesn't have a long life. But I'll mount on the roof (a few feet above the peak of the roof) if I need to.

I called Antennas Direct and the woman steered me towards a DB4e (long-range and multi-directional). But it doesn't have VHF reception (and 2 or 3 of the channels I want to get are in H-VHF). I found an antenna made by Stellar Labs that appears to be VERY similar to the DB4e at a much lower cost - but it is not rated for H-VHF either.

I read some articles about combining two antennas (UHF and H-VHF), and it sounds like a bit of work. Cutting cables to matching lengths, going through reverse splitters, matching impedances, etc. Is all that necessary? Is it as hard as it sounds? Is there a single antenna that I could use to try to get all the stations on my wish list?

If I put the antenna in the attic, I will need less than 10' of cable to reach the TV. If I mount on the roof, I will need either 15' or 30' of cable depending on how I route it.

To cut to the chase (and appealing to the combined knowledge and experience of members of this forum), what do you recommend for my situation?

Thanks (in advance) again!
Clint
(I tried posting this once and it didn't seem to work. Trying a 2nd time. I hope this doesn't result in duplicate postings.)

[ADTech]

(Note: I posted a similar question on another web site, and the only real response was from a sales tech at an antenna company, recommending one of their antennas. This site - TV Fool - looks like it might be a better place to get some advice.)

That's hardly an accurate depiction of our previous conversation: http://www.avsforum.com/forum/45-loc...cut-cable.html You indicated that you had spoken with a coworker so I double-checked her work and concurred, adding specific observations.

I read some articles about combining two antennas (UHF and H-VHF), and it sounds like a bit of work. Cutting cables to matching lengths, going through reverse splitters, matching impedances, etc. Is all that necessary? Is it as hard as it sounds?

It's actually very easy when you use a UVSJ combiner. Here's an example, just ignore the amp and power inserter if no preamp is in use. https://www.antennasdirect.com/cmss_...e_Antennas.pdf

Is there a single antenna that I could use to try to get all the stations on my wish list?

Maybe, but your VHF signals come from a substantially different direction than do your UHF signals. You'd have to use a relatively low gain (less focused) antenna and hope that you can split the difference while still maintaining reception of terrain-impaired signals. Such a scenario is pretty much impossible to predict, it would need to be considered an experiment whose outcome can only be demonstrated.

One error about the TV Fool report: I don't have line-of-site to the closer mountain. You'd have to be about 15 or 20 feet above the peak of my roof to have line of site. There is a small ridge about 250 yards south of me. The ridge itself doesn't block line of sight from my roof, but houses and trees on the ridge rise up high enough to block my line of sight.

That does complicate the estimates. Usually, it means that greater patience in trying available mounting locations and heights may be required.

I suspect that TV Fool's map software is looking at the elevation of the earth and isn't accounting for the elevation of houses and trees.

That is substantially correct, it's due to the limited resolution of the elevation data in use. The propagation software uses the terrain elevation data from the STRM mission that was done back in February 2000 (https://en.wikipedia.org/wiki/Shuttl...graphy_Mission). At its highest resolution the SRTM data effectively averages radar-mapped terrain elevation into either 30m or 100m squares. The propagation software then uses each of these virtual elevation points to calculate a line of sight signal path, then performs the necessary LRI calculations to come up with an estimate of received signal power for every transmitter within a given radius, then it sorts and displayed all that. It really is an engineering marvel that this site's creator came up with.

(I tried posting this once and it didn't seem to work. Trying a 2nd time. I hope this doesn't result in duplicate postings.)

I use the Lazarus add-on for Firefox, it keeps a record of recent posts as well as work-in-progrees and has saved me considerable time when posting goes awry. Highly recommended!

[Clint]

I had a thought this afternoon. I have friend who is a EE. I'm pretty sure he owns a spectrum analyzer. If he would agree to haul his spectrum analyzer up onto my roof, do you think I could get data on signal strength that would be helpful in determining what kind of antenna I'll need and how high I'll need to position it?

[ADTech]

A spectrum analyzer is an invaluable tool for working with antennas, especially if it has a battery.

You'd probably need an appropriate antenna in the first place. If he's an RF engineer, he may well have one that covers the requisite frequiencies, depending on his particular specialty.