No DTV Signal

AndyTiedye

DTVUSA Member
#1
Our pursuit of DTV is reaching the "extreme measures" stage.
TVFool says we should have plenty of reception:

But TVFool does not take trees into account:

We can pick up about 8 analog stations, but no digital stations.
All the really strong stations are low VHF. High VHF is weak.
Analog UHF is unwatchable with a roof antenna.
The only way I could watch it at all was to hang a TV antenna
high up in the redwoods. After getting no signals from roof height,
I tried hanging it from the tree for digital.
 
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AndyTiedye

DTVUSA Member
#2
Part 2
The antenna is a 91XG, it is up 50'. There is 100' of new RG6U.
I aimed it carefully at Sutro Tower:


but it was all for naught::(


Tried Channel Master and Zenith STBs. Tried with and without Antennacraft amplifier.
 

Tim58hsv

DTVUSA Member
#3
Yagi's are the best antennas for long range reception but very very directional. Maybe too directional for your situation. Something like a db8 may work better for you since they aren't as directional and they are rated at something like 60 miles.

I base that on the results of my antenna set-up in the attic. I have a db2 and db4 that works great up there. There's also an old top of the line Radio Shack uhf yagi laying up there that's not hooked up because when I tried it out about two weeks ago, it just wasn't any good at picking up channels compared to either db antenna.

Yup, a 2-bay bowtie antenna even works better in an attic than a top of the line Radio Shack yagi will, at least from my experience.

A db8 might be worth a shot as long as you can take it back if it doesn't work.
 
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Jason Fritz

Administrator
Staff member
#5
How directional IS a 91XG?
According to Antenna's Direct own Product Description:

The reflector grids create an improved front to back ratio with shorter construction while the 91 elements truly make it one of the highest gain UHF antennas available.Although the 91XG is one of the highest gain UHF antennas made, it is also very directional. If you live more than 60 miles from the transmitters, you must get as much elevation on the antenna as possible. Even with its great gain, it cannot pick up signals blocked by the curvature of the earth.
The DB2, DB4, and DB8 are still considered directional antennas because of their flat desgin as well.

That 50' mounting height in the trees was a great idea, but I'm willing to bet there's still a good amount of deflection. How many feet distance in cable total between the antenna and the converter? 100' total?

Are their close trees directly in the signal path of your current mounting position?

I could never get tired of looking at those redwoods everyday
 
#6
The red woods would not cause as much deflection as a oak or other non evergreen tree. place the 91-xg on a pole about 30 ft connect quad shield coax between it and the tv if over a 100 ft place a wineguard 4800 pre amp on the mast under the antenna. tilt the antenna to fifteen degrees on the mast see if this helps hanging it in a tree allows it to sway and causes the signal signal not to lock. mount it sturdy at 30ft or maybe 40ft:)
 

TonyT

DTVUSA Member
#7
Definitely like the CM 7777 for preamp setup, but this is a tough one, especially with not being able to get the antenna mounted higher than the trees. I mean, how can anyone actually mount any taller than a forest of redwoods?? ;)

Your 91XG would be perfect if you could get a clear line of site mounting position. Multipath seems like the main problem here.
 
#8
Definitely like the CM 7777 for preamp setup, but this is a tough one, especially with not being able to get the antenna mounted higher than the trees. I mean, how can anyone actually mount any taller than a forest of redwoods?? ;)

Your 91XG would be perfect if you could get a clear line of site mounting position. Multipath seems like the main problem here.
OK the 91-xg can be tilted up 15 degrees to point over the horizon of the trees to give better signal:)
if you could find a gap in the trees at 344 degrees tilt it up 15 degrees an see if you can get a signal then.
 

AndyTiedye

DTVUSA Member
#9
place the 91-xg on a pole about 30 ft connect quad shield coax between it and the tv if over a 100 ft place a wineguard 4800 pre amp on the mast under the antenna. tilt the antenna to fifteen degrees on the mast see if this helps hanging it in a tree allows it to sway and causes the signal signal not to lock. mount it sturdy at 30ft or maybe 40ft:)
I had it up 25' (from the ground) on a pole with 25' of coax (which is why I
only went up 25' that time), angled up and got nothing. That's why I tried
putting it up in the tree. I can go up to 40' on that Army surplus field tower
I have been testing with, but will that improve the signal?

In either location I get 0% signal strength on every channel except 19, which comes up to about 30% intermittently.
 
#11
I had it up 25' (from the ground) on a pole with 25' of coax (which is why I
only went up 25' that time), angled up and got nothing. That's why I tried
putting it up in the tree. I can go up to 40' on that Army surplus field tower
I have been testing with, but will that improve the signal?

In either location I get 0% signal strength on every channel except 19, which comes up to about 30% intermittently.
yes place it on the tower and angle it if there is a gap in the trees near 342 degrees point it there and see what happens.
if you put 20ft and 40 ft in tv fool for height you will see a difference in signal strength and noise levels, put ten ft mast on antenna and you could get 45-50ft .
 

Byte24

DTVUSA Member
#12
Rays from the transmission tower come to earth after passing over a skyline ridge. This ridge could be a tree line 50 yards away or a mountain ridge 5 miles away. The rays diffract at the ridge, staying in a plane perpendicular to the ridgeline. The result is often overlapping rays.

Overlapping fields will result in weak signal spots and strong spots arranged in a regular pattern.
For UHF the strong and weak spots are often 5 to 20 feet apart. If you are in a neighborhood with overlapping fields, moving your antenna a few feet can make a huge difference in signal strength.
Siting the antenna
 
#13
I tried putting a VHF/UHF antenna* up in the trees and was able to pick up channel 11 in digital.
About 50% on the "meter" on the Zenith STB.
11 is the only VHF digital station in the Bay Area now until 7 moves down to real 7,
but they are expected to be really weak.

Still no UHF, but if the 91XG didn't pull in any, I didn't expect this POS to.

*beater rat shack I had lying around. I tried to order a Winegard 1713, but they're back-ordered.
 
#14
yes place it on the tower and angle it if there is a gap in the trees near 342 degrees point it there and see what happens.
if you put 20ft and 40 ft in tv fool for height you will see a difference in signal strength and noise levels, put ten ft mast on antenna and you could get 45-50ft .
I put the 91XG back up in the tree at 50' last Friday and got reception
on lots of channels, some as far away as Sacramento and Cotati.
We hadn't had any fog for a few days, and I had the antenna pointed at
a gap sorta NNE. Foggydrizzle returned that night and we lost all reception again.

Got reception back again after things dried out and I re-aimed the antenna
at a different gap. Now I can get KQED! I lose 3 and 10 from Sac'to,
but that's OK. Oddly, I still get 13 on this heading.

Looks like DTV will be a fair weather friend here.

WET trees eat the signal.
 

Jason Fritz

Administrator
Staff member
#15
I put the 91XG back up in the tree at 50' last Friday and got reception
on lots of channels, some as far away as Sacramento and Cotati.
We hadn't had any fog for a few days, and I had the antenna pointed at
a gap sorta NNE. Foggydrizzle returned that night and we lost all reception again.

Got reception back again after things dried out and I re-aimed the antenna
at a different gap. Now I can get KQED! I lose 3 and 10 from Sac'to,
but that's OK. Oddly, I still get 13 on this heading.

Looks like DTV will be a fair weather friend here.

WET trees eat the signal.
Thanks for the update Andy, looks like you guys get about 20-25 inches or so of rain a year, might have quite a few down days eh?

 
#17
place the 91-xg on a mast and tiltit toward the gap the closer it is to the trees the more it effects the signal. the signal will drop down over the trees like it will a hill side so I would try that and see what happens.
 
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