OTA Antenna Heigth vs. Coax length.

[MR2NR]

I am a novice at this and have experimented a few times with OTA mainly analog though only three digital homes I have had to rewire from degrading 300ohm flat wire. I have lived here all my life (60 miles from the network transmitting towers I use) and am curious if using a very high tower to mount an antenna helps or degrades signal due to coax length. I am going to attack this job this summer and wanted some ideas. I have an older full size radio shack VHF/UHF antenna with the radioshack 75-300ohm converter and RG-6 Quad shield cable I plan on crimping myself for the least amount of coax. it's going straight into my 722K's OTA Modulator. I know that amplifiers are a double edged sword but since I'm not that close to other stations and it has shown to help with other peoples setups in my area I consider it an option for coax signal degradation but I am cheap so if I don't need it I won't buy it. I live in town with one or two trees in the line of fire but 20ft from the antenna mast. It's not very hilly. But there are hills that are higher than my antenna's ideal height halfway between us. I can get on average 43-50% signal with RCA's converter tuners at other houses but would like 75-80% for my installation if possible. The only piece of equipment I don't have is a tower which is the biggest reason for this posting. I can clear the house with a pole mast but would invest in a tri tower with a cement footing if it will be more beneficial than buying a new antenna.

Here is some more info you might need.
My city Weaubleau MO ZIP 65774 Alt. 978ft.
Transmitting towers Fordland MO Alt. 1604ft.

TV Fool

Thanks for any advice or cheap ideas.

 

[navychop]

I presume you mean "pre-amp." That will help with weak signals. Could also make strong signals overwhelming, but I gather that is not a concern in this case.

Distribution amplifiers can compensate for long/multiple runs within the building.

I think you might get by with, and do better with, a UHF only antenna such as the CM4228. It will reach down to channel 7, so your channel 10 might be picked up. Of course, try with what you've already got, first.

You will not need a rotor, assuming you're happy with the first few on that list. And I'd certainly try rooftop reception before going with a tower. And maybe try an antenna high in a tree, well aimed, before investing the bucks in a tower, which may or may not help.

You'll find crimping/compressing quad shield to be a bit more of a challenge than regular RG-6. The quad shielding, I believe, is for where there is interference, and may not deliver a better signal in interference free areas. Others more knowledgeable than me may chime in.

Good luck. I'm happy with my OTA, and not so happy that Dish is going to provide my locals via satellite whether I want them or not, starting 2/1 (or so I hear).

 

[MR2NR]

You'll find crimping/compressing quad shield to be a bit more of a challenge than regular RG-6. The quad shielding, I believe, is for where there is interference, and may not deliver a better signal in interference free areas. Others more knowledgeable than me may chime in.

I have a nice crimper and the "correct compression ends" for RG6 Quad sheilds and it is by far the best setup I have ever had. I have used it in three house installs where I had to replace all the 300Ohm cable that was cracking and showing bare wire. With the digital transition I have had to rewire my families houses and hated having to hunt down coax and the correct length so I went and bought all the tooling at monoprice. Highly recommended if you want a clean OTA install . But doing these installs I noticed that the longer coax you run the worse the signal gets dramatically. It didn't matter if i was using single shield or quad shield the length really hurt the digital signal but I did notice on TV Fool that the higher you are the signal would increase dramatically so I realy want to know is there a barrier on height vs. length.

 

[navychop]

I think the tradeoff is going to vary by each location. Hard to guess, I'd experiment, especially if I had or could borrow a meter.

I also run my own coax. Current and previous home were thoroughly wired by me- OTA coax, satellite coax, phone, Ethernet & extra outlets. Plus rotor wiring, pre-amp and distro amp. Only way to go, although I have broken down and added a wireless router. Easier for back yard surfing. Just ask my wife.....

 

[Jim5506]

I believe 100' of RG-6 nominally loses about 3dB or 1/2 the signal, so 200' would be a 6dB loss or 3/4 of the original signal.

You receive as much loss from one splitter as you do from 100' of RG-6.

Plan your amplification with this in mind.

I would look at TV Fool and find your exact location either by street address or by using the maps and actually seeing your house on the satellite image.

This will tell you which stations (UHV/VHF or both) and give you an approximation of their signal strengths at your location.

With the maps part of TVFool you can also experiment with antenna heights to get a computer simulation of how varying your antenna height will effect reception.

It may give you an idea if altitude is more expensive than antenna replacement.

Running a generic elevation scenario on you zip code it looks like you do not start to get any significant jumps in reception with a 10 ft rise in antenna height until you are above 100 ft AGL.

Contrast that with the gain of a Winegard 7698P antenna on channel 28 (your weakest network station) which is somewhere in the 14dB neighborhood.

KSFX (FOX 27.1) is estimated at -7.7dB noise margin at 35 ft.

It should be receivable with the 7698P at that elevation and Solid Signal has it for $150 shipping included.

How much tower will that $150 get you?

If it were me, I'd go with the new antenna in my current mast with new wire and see if it works.

If not then we start looking at more expensive solitions such as towers.

 

[navychop]

Also see antennaweb.org.

 

[Splicer]

Well lets get this straight. The amount of signal lost per 100' of RG6 is dependant on the frequency being transmitted/received.

A tower will cost you much more than a pre-amp, which is what you want/need in your situation. A tower will add unnecessary cost to your project. A roof mount as high as you can have it, + a fixed output LOW NOISE pre-amp is all you will need. A rotor (more money) won't aid you at your distance unless you have a 100' tower, and that is expensive.

Quad shield or single shield will not aid in reception. The quad shield is only to aid in the rejection of unwanted, spurious signals. But if you're going to do it, do it right I say and use quad shield.

As for crimping, make sure you are using the proper connector for the cable being utilized. DO NOT use fittings designed for quad shield on single shield cable and vice versa.

Concerning the suggestion to get a CM4228, that is a good idea. Not so sure about getting channel 7, but that doesn't really matter as it should be able to p/u ch10 with no troubles. Besides, to get ch7 you will need to turn the antenna. Not to mention ch7 is another 20 miles out.

 

[MR2NR]

Well I guess I'll get an amp and use a 50ft tower mast with the old Antenna and see what I get then as I'm not going to buy another antenna and be in the same boat. I have the metal and someone to weld me together a tower as I am his computer guru slave and he said he would be happy to put it together for me. Don't worry I will have a proper ground and cable anchors. To bad it will be a lightning magnet . But the 200ft water tower isn't too far away

Using my address compared to the ZIP nets you no difference and I varied the heights also.

As stated I am just needing 3.1, 10.1, 21.1, 27.1, and 33.1. That covers all the major networks

So that just leaves a couple questions for my situation.

What would the loss be with an avg. Signal of Nm 19.4 and Pwr 71.5 and 57ft of RG6? (Wish TV Fool would have a calc for this. if you know of one let me know.)

What is the best amp to get?

 

[meinename]

MR2NR,

I have a RCA model DTA800B1
The signal meter on my RCA unit is mostly a signal strength meter
Other units I have used and owned give a signal quality, which is much more valuable for digital TV.
I have had a Zenith DTT900 as well as both the DigitalStream DTX9900 and DTX9950
I have borrowed a Magnavox before the Coupons were available. The Non-Analog-passthrough model.

You wrote that at friends home's you could get a 50%?
I live 8 miles from the towers near me and the best I can get is 54% with my outdoor UHF antenna on a 50 ft. RG-6Q run without an amplifier.
I haven't seen better without an amplifier.
I usually see 40% tops where I have hooked it up elsewhere.

Something very annoying that the RCA does is show black screen when there are too many errors (read as: a mis-colored block or two) but the audio keeps playing.
That is usually a sign of a very minor problem. It is a very annoying behaviour by this converter.
In the case I had recently it was poorly installed compression connectors on a cable. Swapping the 25 foot RG-6 out for another made the blackouts go away.

On contrast the Zenith and DigtalStream show the otherwise perfect picture.
The key for me is if the audio drops out too. Then you will know you have a persistent problem.

I traded my poor grandma a Zenith for this RCA. To any other person in any other situation, I wouldn't have. It was not a fair trade otherwise.
But I have the luxury of signal, she did not at 45 miles and no amp next to a highway.
She had A/V drop-outs incessantly when I got there.
I was able to minimise the drop-outs to 1 every 5 to 10 mins.
The standard I read elsewhere at 45+ miles was 1 drop-out per hour.
Grandma was very happy that it worked most of the time instead of hardly at all.

What I want you to get out of this is to borrow another converter from someone else. Preferably a Zenith or a DigitalStream.
The RCA converter will have you hunting for problems that will otherwise not be a problem for any other digital TV tuner I have used.
That includes the digital TV and PC tuners I own.

 

[Splicer]

What would the loss be with an avg. Signal of Nm 19.4 and Pwr 71.5 and 57ft of RG6? (Wish TV Fool would have a calc for this. if you know of one let me know.)

I may not have been clear earlier. The amount of signal loss is frequency specific. The higher the frequency, the higher the loss.

What is the best amp to get?

I recommend these as the best ones depending on your need. I think it will be fine for you. Look around for the best price.

 

[MR2NR]

What I want you to get out of this is to borrow another converter from someone else. Preferably a Zenith or a DigitalStream.
The RCA converter will have you hunting for problems that will otherwise not be a problem for any other digital TV tuner I have used.
That includes the digital TV and PC tuners I own.

Thanks for the info. I really need to find a reputable meter to borrow .

That brings up another question. Does the 722K w/module have a signal meter for OTA?

 

[MR2NR]

I recommend these as the best ones depending on your need. I think it will be fine for you. Look around for the best price.

NexxTech +15 dB Amp?? Where did you get yours and for how much?

 

[Splicer]

I apologize, I thought I included the link.

Amazon.com: Motorola Signal Booster 484095-001-00 Bi-Directional RF Amplifier:?@@AMEPARAM@@http://ecx.images-amazon.com/images/I/41HG8Q6hI6L.@@AMEPARAM@@41HG8Q6hI6L

Look around for the best price. As a reference, I got mine for $7 but that was a one time fluke. It seems that at the time I began recommending these, the price increased. But you can get them on ebay reasonably enough I think.