Charleston, SC installers & DXing

[rufwork]

I'd like to pick up the Fox (channel 18/virt channel 43) and CBS affiliates from Myrtle Beach to get just slightly out of market NFL games from my home near Mount Pleasant, SC. It's just under 100 miles to the antennas, flat ground, and I'm just past the purple at TV Fool. That said, I'd be clearly DXing in the afternoons (1-7pm), which I understand might make things tough. If tropo is a daytime occurrence, it looks like I might have good and bad Sundays.

I've read up on the antenna options and a bit about amplifiers. It looks like an Antennas Direct 91XG is the right (or at least a good, affordable) choice, but it needs to be up pretty high, I think -- say 20-30 feet. I've also got a fair number of trees, but I'm not sure if that's as big a deal (oops: the HDTV Primer says, "§ UHF -- It is best to assume that trees block all signals."). I've got an indoors DB2 right now which, natch, gets nothing from Myrtle Beach.

From tvfool.com for Fox
(if I get this channel, imo, I "win")
=====================
Fox -- WFXB
Real: 18
Virt: 43-1
NM (dB): -18
Pwr (dBm): -108.8
Path: Tropo
Dist Miles: 96.4

I might be willing to put an antenna on a mast on my single story garage, but past that I'd like to get an expert. I've called dish installers and TV repair places, and nobody will or knows of someone that'll install an OTA antenna. It was pulling teeth to get my electrician to run coax to my roof when I built the house, strangely enough, and he (nice enough guy) said he didn't know how to install an antenna. :shocked

Anyhow, any ideas or advice? Far and away the best post I've found is this one and the description of "fringe" on the HDTV Primer is excellent, but as far as finding an installer that can figure out my specific issues (specific channels, etc) better than my guessing, I'm lost.

I realize I might not be able to pull it off. Fun trying though, right?

 

[Robz]

I'd like to pick up the Fox (channel 18/virt channel 43) and CBS affiliates from Myrtle Beach to get just slightly out of market NFL games from my home near Mount Pleasant, SC. It's just under 100 miles to the antennas, flat ground, and I'm just past the purple at TV Fool.

Reception is possible at 100 miles distant, but atmospheric conditions will significantly influence path loss. I am able to receive channels located 110 miles distant mostly at night. Interference from other on channel TV broadcasters may also prevent reception. In addition, the so called "whites space" devices may make reception impossible, if and when implemented.
To get an idea of reception possibility, a UHF receiver or scanner tuned to the pilot carrier can detect the TV channel long before reception is possible. Theoretically 15 db S/N ratio is required.
A good antenna located preamp is also very helpful HDTV Low Noise Amplifiers and Preamplifiers, Preamps, NF 0.4 dB - Research Communications Ltd UK
These preamps are the best ones I have used. Excellent noise figure, very high immunity to signal overload.

 

[rufwork]

To get an idea of reception possibility, a UHF receiver or scanner tuned to the pilot carrier can detect the TV channel long before reception is possible. Theoretically 15 db S/N ratio is required.

Followed everything but this. "tuned to the pilot carrier" and "15 db S/N ratio" confuse me a little.

I'm assuming the latter is similar to the discussion at this post at dbstalk, but I'm still not able to figure how this works.

I guess I might as well skip the Channel Master 7777 amp and go straight for the UK version, then? Any recommendations for a channel 18 antenna? That same dbstalk thread talked about making your own channel-specific antenna. I tried the frequency I found here and plugged that into this page, but I don't know what the balance of the choices really mean there.

I think I need to visit the local university and see if I can buy an electrical engineer a good lunch.

I was a little worried to see this post that said the 91XG wasn't the best for channel 17 without saying what was. I assume that probably includes channel 18 as well, which is why I started Googling that channel-specific stuff.

EDIT: This "channel cut" antenna from Blonder-Tongue (for $215 plus shipping!) seems like the beat-all, end all antenna for channels 14-19 from my most recent Googling (also mentioned with two other brands here).

http://www.blondertongue.com/store/default.aspx?DepartmentId=43&F_ALL=Y
http://www.sateng.com/off-air-broadcast-reception/antenna/bty-10-u/ -- same one for $172 +shipping

Though this page the blonder tongue has a lower gain and that it's just built tougher.

 

[Robz]

The pilot carrier for channel 18 is 494.31 MHz; its 0.31 Mhz above the lower channel edge. The pilot carrier is used to demodulate the 8VSB digital signal and also useful to detect the carrier with a narrow band UHF communications receiver at far lower signal levels then required for digital 8VSB TV reception.
Theoretically, a 15 db signal to noise is required for 8VSB TV reception. However it's more like 20 db in the real world. Its simply the ratio of received signal to the noise level expressed in db. Cable loss, splitter division, receiver noise figure and antenna noise figure all combine to the noise level. An antenna does have a noise figure. Is a combination of the noise emitted from a “warm earth” and the galactic noise from the sky. The major contributor is the “warm earth” black body noise radiation and is a limiting factor for weak signal reception.
The Channel Master 7777 is a good pre-amp; however I have found the Research Communications pre-amp to be better. For best results, mount the pre-amp as close to the antenna as possible.
A single channel antenna can be designed for optimal performance better than a broadband antenna. The NEC (Numeric Electric Code from the dept. of Navy) software provides antenna analysis tools. The original used computer punch cards written in Fortran. To day the punch cards are replaced with a text file. Very useful for antenna design and analysis, but difficult to use. Software developers have written interfaces to NEC to make the process of data entry and analysis user friendly. A good one, free of charge is 4NEC2. There is a significant learning curve, but if you are interested down load the latest version at 4nec2 antenna modeler and optimizer

 

[No Static At All]

I was a little worried to see this post that said the 91XG wasn't the best for channel 17 without saying what was. I assume that probably includes channel 18 as well, which is why I started Googling that channel-specifics.

I've tried the original CM4228 & Winegard HD 8800 in an area that has low UHF channels 15, 16, 19, 21 & 22. The 91XG did better than either of the 8 bay antennas on the entire UHF band. On paper, the HD-8800 is said to be the best low band UHF performer, but I had much different results at that particular deep fringe location. (With a good deal of height & preamplifier experimentation) The 91XG antenna/Winegard 4800 preamp obtained the best results)

 

[Larry1]

I've read up on the antenna options and a bit about amplifiers. It looks like an Antennas Direct 91XG is the right (or at least a good, affordable) choice, but it needs to be up pretty high, I think -- say 20-30 feet. I've also got a fair number of trees, but I'm not sure if that's as big a deal (oops: the HDTV Primer says, "§ UHF -- It is best to assume that trees block all signals.").

Even 20-30 feet might still be too low. How high are the trees around you? I'm in a deep fringe area and it is common for towers to be 4 to 5 sections plus. (each section is 10ft, plus mast) At 4 sections my neighbours antenna is about the height of the trees. I'm only currently have 3 sections and i'm below the trees and suffering from it. Definitely you need to be above the trees. Most of the towers in my area were put up 30-40 years ago. Since then the trees have grown. Remember, trees grow. Make sure you are above the trees enough to account for their grouth.
The one in this picture would be about 55-65ft.
T.V. Tower removal
There are free standing towers (like the one in the above picture), or ones that are attached to the side of your house.
http://overtheair.saveandreplay.com/Antenna_Towers.asp
Now, most channels in my are are 65 to 70 miles away. For further you would need even a higher tower and look into ganging 2 91XG's together.
http://www.aa6g.org/Lp/lp.html
For cost, the CM7777 is a very good pre-amp. The UK one (for me) is just too expensive for just a little less noise. If you want to make up for the CM7777 amp, use RG-11 cable and you should come out about even. (in my opinion, but that just my opinion)
Now to turn all that, look for a good heavy duty rotor. A lot of people use HAM rotors for the extra mass to move.
Now be prepared for sticker shock if you want an expert to put it up for you. Towers are not cheap, and add the antennas, rotors, cabling, pre-amp., etc....
100 miles may be just a little to far for reliable reception.

 

[rufwork]

100 miles may be just a little to far for reliable reception.

The NFL schemes against me, I'm telling you.

I might give the 91XG a shot in a field down the road at night up on a pole to see how it does. At $60, the worst I'm doing is giving myself a better antenna. I can't decide if I should bag an amp. I don't know that there's much to DX around here if it doesn't work other than Jacksonville and maybe Cola, and I'd hate to throw too much money down a hole. I suppose that's a few more possible games a year.

I'm not sure how I'd borrow a UHF receiver or scanner, but I'll check around for that too.

Thanks for the help. It looks like I'm on the right track. My only real question is if I should trust the Blonder-Tongue vs. the HDTV Primer gain measurements for the XG91. It would seem that the XG91 barely outperforms the Blonger-Tongue channel cut antenna on channel 18, though this guy seems to have gone for the B-T pretty quickly instead of something cheaper. Not a huge deal, but I'd rather put my $60-70 towards the B-T at $170 if it's the best out there. Looks like it might just be in the materials rather than the gain.

 

[Larry1]

That setup the link points to appears to be short distances to the towers (max 36 miles) and relatively high powered stations.
For DXing, you might not even get any signal on the signal meter for long distances without a pre-amp. Without a pre-amp I have nothing watchable, and most stations would not even showup on the meter.

 

[Robz]

Without a pre-amp I have nothing watchable, and most stations would not even showup on the meter.

I also get loss of reception when I remove the pre-amp. While strong major broadcasters are still receivable, distant channels and weaker LP digital broadcasters are lost. The LP ones are only 30 miles distant and line of sight. Without the preamp the total noise figure is about 5 db cable loss + 6 db receiver noise figure + 6 db splitter loss = 17 db. With the preamp the noise figure is reduced to about 1.3 db. If I add the antenna noise figure of 300 degrees K the overall noise figure is increased to about 3.8 db. Using RG11 the noise figure is slightly improved to about 3.7 db or a difference of 0.1 db. The pre-amp provides a significant improvement of 17-3.8 = 13.2 db and will make a clear difference in reception.
The values are from the standard noise function:
F = F1 + (F2-1)/G1 + (F3-1)/(G1*G2) + (F4-1)/(G1*G2*G3) ....
F is Noise, G is gain.

Where the conversion from db to F or G = 10^(db/10)

A nice on-line caculatr interface is System Noise Temperature And G/T Calculator