Mountain in way and -db's...is this even possible?

[Robert_W]

Hello folks, want to say thanks for this valuable resource of a site. Much appreciated.

I really want to dump the dish but not sure about locals. The rest we have covered via Netflix, Amazon, etc.

So here's my situation. We live very rural. There is one tower 4 miles away on top of the mountain that we live at the base of and because of terrain there is no direct line of sight. If I could move my house 300 feet up or over I could do this with a small inside antenna it seems. But alas that is not the case.

I have a "2edge" reading with the highest reading being -3.8db on our plot here:

http://www.tvfool.com/?option=com_wr...46ae3df763b2a8

I'm only interested in the top 5 channels on that list. 8,10,11,12, and 13. I think they are the only ones possible anyway. Willing to mount any size antenna on the roof but not sure if I can boost those signals enough. Though I read here in the FAQ's that it is possible to even with negative db's.

I would like to run this to 3 TV's in the house.

I'm looking at the largest of antennas like the Channel Master 5020, or Winegard HD8200U Platinum, or similar.

Also assuming that I will need a pre amp so a Channel Master 7777? or will it be too much and I should go with the 7778? I'm thinking the stronger the better in my situation.

What I am not sure about is if I will need a splitter booster also like the Channel Master 3414 4 Outputs Distribution Amplifier or will there be enough of a db boost via the pre amp? I know that too much can cause issues too. Will be roughly 75 feet of cable in the longest run.

Open to any suggestions and feedback.

Thanks again.

[GroundUrMast]

Given that all the signals are in the High-VHF band, I'd simply use an Antennacraft Y10713. Be prepared to experiment with aim point. You may find a useful reflection coming at you from an odd direction. I'd give the preamp job to an Antennas Direct PA-18.

If you have any FM stations close to you, add an FM trap between the antenna and preamp.

[Robert_W]

Appreciate it.

We live in a very steep valley and I seem to remember before things went digital that some of the old timers around here actually got a better signal bounced off the opposite side of the valley 180 degrees from LOS. I assume this is still the same concept with the digital?

Is there any antenna specifically for high VHF that's better than the Antennacraft Y10713?

If I add everything up that antenna has a gain of 16.5 db which is great...plus the preamp of 15 db minus the Antennas Direct PA-18 loss of 2.8 db and cable loss of roughly 3 db.

So assuming the numbers on the chart are close...with the worst channel signal the chart indicated ...-7.8db...this translates to roughly 17db fed to the TV's.

Would I still then need another powered booster / splitter? Or is 17db or more plenty and would a regular non powered splitter 1>3 tv's be OK?

And just to confirm then that the 7777's preamp 30 db boost would be over kill?

How many db's are really needed at most new TV's for decent reception. I've read it's theoretically possible at 0db but what are real world #'s? Is 10 db plenty in most scenarios? And at what point is it overkill or over amped? Is there a number for that? Like 25 db or more is too much? Or is that number way higher?

Thanks again.

[GroundUrMast]

You are in a tough spot... or at least that's what your TVFR suggests. However, when you are this close to the base of a hill/mountain, the only way to know what will be received is to try. You are in the fortunate situation that you have no need for a huge/expensive all channel antenna, in fact all the channels fall into a single band. I have seen the Y10713 offered at very affordable prices, I bought one new in the last year for about $25 as I recall (quite a steal i thought... but I see they are now at about $38 on amazon).

Having said all that... Yes, there is a good chance you'll find a bounce or other reception anomaly, just as the 'old timers' mentioned. (There is also the possibility that this just wont work.)

On paper, add the antenna gain to the predicted NM value. If the result is positive, it's reasonable to give it a try. If I'm dealing with the typical installation, with fairly open horizon, (no mountain) I want to achieve no less than a +10 dB NM net at the antenna terminals. In other words, Predicted NM + antenna gain should be +10 dB NM or higher. In cases like yours, you should try even if the prediction looks bleak.

Amplifier gain does not add to the antenna gain. Amplifier gain can only overcome cable/splitter losses and help with some of the noise produced in the tuner front-end. So, in very weak signal applications such as yours, it's more important that the preamp be located close to the antenna and that the preamp produce little noise of it's own. If more gain is needed, a distribution amplifier can be added. The PA-18 is a very good, low noise design, intended for weak signal applications such as yours. The CM-7777 is a bit nosier, the difference in gain is not the deciding factor.

I would start by testing with just the antenna, a 50' length of new coax and a good TV set-up for OTA reception. (The majority of tuners default to cable mode. You'll need to use the set-up menu to switch to 'air' or 'antenna' mode. Then most tuners will need to be run through a scan to find channels.)

If you see some signals, then invest in the preamp and other hardware.

[ADTech]

Is there any antenna specifically for high VHF that's better than the Antennacraft Y10713?

It's the highest gain 7-13 antenna remaining on the market.

If I add everything up that antenna has a gain of 16.5 db which is great..

No, the antenna's gain is stated as 9.4 dBd on the specification sheet.

On high-VHF, the PA18 averages about 1.7 dB noise figure and about 19.6 dB gain. RG6, at high-VHF frequencies, should have a loss around 2.75 dB/100'.

Keep in mind that those transmitters have power outputs less than half of the power of the light bulb(s) in your refrigerator (door open). Plus, that energy is focused mostly at the horizon. At your depressed angle of elevation relative to the transmitting antenna(s), you may find that little signal is even sent in your direction before considering the effect of the terrain blockage.

The TVFool calculations, in your case, are little more than "guesstimates". Until you actually put an antenna up in the air and experiment with it's aiming direction, you'll be pretty much flying blind.

[Robert_W]

Thank you gentlemen. I kinda figured this was going to be a crap shoot. I'll start with just the antenna and see what happens.

But for give my ignorance. I'm having a hard time with this: "Amplifier gain does not add to the antenna gain." So what's the point?

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Yes as in the past , Test reception buy aiming the antenna in the other direction to receive a reflected signal.

Perhaps you can find some old timers , that did it in the past.

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As to the antenna gain and the amplifier gain adding to the antenna gain.

Pay close attention to the wording of the statement.

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I recommend Test reception , with a preamplifier and without a preamplifier.

When Testing reception without the preamplifier , all parts of the preamplifier must be Disconnected and Removed.

Disconnect and Remove the preamplifier unit , Disconnect and Remove the power injector , Disconnect and Remove the power supply.

[Robert_W]

Originally Posted by teleview

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As to the antenna gain and the amplifier gain adding to the antenna gain.

Pay close attention to the wording of the statement.

OK, not trying to be dense...maybe it's just a wording thing. I just don't quite get it. I've read through a bunch of pages and searches and just don't seem to be grasping this concept I guess.

So the names... preamp...amp...booster...just for marketing proposes?

If it doesn't boost db then what is it "amplifying"? Why the claims of 15 db gain?

Lets try this...

Here's a hypothetical. I have -3.8 db at the antenna. Then my antenna adds 9.4 db of gain. So I should have a signal of 5.6 db at the antenna leads. Right?

So then if the preamp / amp doesn't add 15 db to that signal it's only purpose is to basically hold that 5.6 db signal steady? To compensate for line/splitter loss? As long as there isn't more than 15 db of total loss through the run from the antenna to the TV? (IE...splitters, line length etc.)

And the preamp also adds noise of 1.8 db so I need to subtract that from the 5.6 db for a grand total +3.8db at the TV?

In other words what I get at the antenna for a signal will never get any better no matter what I do? There is no way of making that signal any stronger to my TV?

If this is true then is it just not really reasonable / possible for any one with -dbs for initial readings to receive OTA tv? If not then why bother showing a chart that goes into the -30 dbs or more? What do people do in those situations? Is it just there for show?

Not trying to be difficult. Just trying to understand.

Thanks

[ADTech]

The amplifier gain does add to the power level of the signal, but the amplifier also amplifies the noise floor, plus its own internal noise. In order to have successful reception, the signal must meet ALL of the following qualifications:

1) Adequate signal power at the input to the tuner. Generally, -82 to -85 dBm is the weakest signals usable.

2) Adequate ratio between the desired signal power and the (simplified) background noise level. Bare minimum is usually around 15-16 dB differential under ideal conditions.

3) The quality of the signal must be such that the tuner is able to decode it reliably. Generally, quality is adversely affected by such things as multi-path and external electrical interference (noise).

The concept of the "noise margin" is such that, if, at the input to the tuner, it is greater than zero, then reception should occur provided ALL of the above requirements are met.

Increasing the gain of the antenna is the only way to improve the power level of the signal without simultaneously raising and degrading the noise floor. Bottom line, it's the only way to improve the signal to noise ratio or the "noise margin".