grapedog

Aaron62

Welcome to the forum grapedog. Have you run your tvfool results yet? I used the coords you gave at an antenna height of 15'


EDIT: In response to your post below me GrapeDog, I overlooked your TVFool info in your post.
My bad, but atleast this info will be useful for everyone else who see's the thread.

grapedog

Hi Aaron, yes I mentioned TV Fool in my original post (love it!) and have looked at the same data you posted above. Issue is that all network signals (KOIN, KATU, KGW, KPDX) are not LOS and are edge reception, which explains why with my 15' antenna location, i can't get a decent DTV signal. What i'm hoping is to have a dicussion about possible alternatives to this current setup. For example, if you put 50' AGL into TV Fool, reception looks a lot more likely. But, before I run off and try this, I wanted to see if anyone knew of other things to think about.

Don_M

As a code writer/editor, you well know that every decision involves trade-offs. That's every bit as true in RF signal propagation. The following comments assume that you want to pull in the major network affiliates broadcasting from Portland. The trade-off comes down to either:

1) Putting up a big tower and getting a single, near-fringe antenna capable of receiving VHF and UHF OTA channels. A Winegard HD-7696P antenna will be sufficient at this height.

2) Installing a mount on the house with a tall mast, perhaps steadied by guy wires, and using two of the most powerful antennas available, one dedicated to VHF channels 7-13, the other designed for the higher UHF channels. You'd want to acquire the antennas and pre-amp specified in the "prescription for deep-fringe reception" if this is your choice.

As you probably appreciate, the second alternative will cost less. You won't need the rotor if the Portland stations are the only ones you want, but the pre-amp specified in the prescription is a must with either setup.

I ran two TVFool reports at the provided coordinates -- one at 20 feet above ground, the second at 50 feet. At 20 feet, you have two ridges (the "2-edge" notations) to overcome. An extra 30 feet overcomes one of the ridges, but not both. The good news at 50 feet is that the signals are an average of roughly 20 dB stronger than those at 20 feet. That's a factor of 100.

Whether the trees block signals tends to be a matter of trial and error. They're not a factor at some locations, and they're a complete pain in the neck at others. Erecting an antenna (or two!) is the only way to find out which one applies to your situation.

Whatever you decide, I would strongly recommend against using a tree as a permanent antenna mount. (It's OK temporarily, for experimental purposes.) Trees have nasty habits that cut into reception and/or greatly shorten antenna life: They sway in the wind, which is murder on UHF signals in particular; they regularly drop sap, which corrodes the metal and can cause a reception-robbing short circuit; and the delicate aluminum will get mangled if a major branch falls on the antenna or the whole tree falls down.

grapedog

Thanks for the well-written response, Don_M. Reading the "deep fringe reception" recipe gives me something to think about. The key issue to resolve is a properly supported mast of sufficient height to get decent signals. I am asking some of my ham radio friends if they can recommend a mast installer. At this location, there are high winds at times, along with the yearly dump of 36" or more of snow. I realize that going with a paid solution like DirecTV is the easy way out, but paying $35/month is not something I want to do, just to receive the 4 networks via (what used to be) free TV.

Don_M

Glad to help. If you and your ham friends are handy (and have the time), you can probably do this yourselves.

I wouldn't worry too much about snow, even if you frequently get the heavy, wet stuff known in Denver as "Sierra Cement." Snow is only a big problem with poorly installed or inadequately supported antenna mounts/masts.

HTNut

I don't want to thread hijack at all here, but AndyTieDye mounted his 91XG a while back (I think it was his only alternative) to some tall trees, and didn't have good results (Thread with pictures are here http://www.dtvusaforum.com/dtv-recep....html#post8884), at least that I know of.

Piggie

Not to mention the increased chance of a lightning strike if it's like here in FL where I have seen many CBers (11 meters) put omni's high in pine trees and boom!

__________________
The more I understand, the less I know.

grapedog

One more question for you guys.... TVFool says that 35' AGL will give me some decent DTV reception. If I use Cowboy's Fringe recipe, I wonder if mature douglas fir trees will impact the signal reception. I don't want to go thru all the setup and then find out that trees block the signal. Note that these trees are probably 100'+ tall and occupy about 1/4 mile between the house and the top of the ridge that is in my way. After that, it's LOS to the towers.

Don_M

Hey, there! They may... or not. Proximity is a big factor: You have a challenge ahead if the nearest firs are right up against the house. If they're more than 100 yards away, don't lose any sleep worrying about it.

One great feature of the 91-XG is its dual boom, which is calibrated to allow tilting of the UHF antenna upward. UHF is where trees would have their greatest impact on reception. You'll want to tilt it so as to aim just above the tallest ridge between you and the stations, anyway; tilting also helps the antenna "see" signals coming in from above the trees. The trees won't be as much of a hindrance to reception of VHF channels 7, 8, 10 and 12 as long as you experiment with placement of the YA-1713 -- backwards/forwards, left/right, higher/lower -- to find the best spot before settling on a mount point for the antennas.