Wind Problem with digital ota locals

[intrepid]

Greetings, I have a problem with my channelmaster rooftop ota antenna losing digital signals during gusts of wind. My local PBS station is about 50 miles away but I have great digital reception most of the time except for high winds that come and go and sometimes rain causes fade. Any suggestions to counter this problem. I also read online that when the analog broadcasts stop and all local stations broadcast a digital signal the power of the digital signal will be increased for broadcasting. Is this possible or did the person who said this know what he was talking about? Any help or suggestions to remedy this would be greatly appreciated. thanks

 

[datwell]

I have a CM-4228 that has the same problem. I have ordered the 622 upgrade so I can get my locals in HD from Dish @ 61.5.

---Doug

 

[sfollenius]

I have the same problem with my winegard 8 bay here in the mountains of NC, where wind is frequent. I awaiting Greenville Spartanburg DMA to come on board!

 

[Rick0725]

What you are experiencing is a form of multipath interferience .

you will likely see dropouts when the wind blows because the strong and weak spots of the uhf signal will move around as the tree deforms and the branches move about.

The way around this is to install a more directional antenna with a higher front to back ratio in place of the CM4228. The new antenna will take the edge off. The 4228 does not handle this type of mutipath well.

The effect is called wave diffraction and overlapping fields.

 

[bhelms]

...The effect is called wave diffraction and overlapping fields.

That is certainly one possibility. I've also got to wonder whether or not some of it is due to the 4228 itself moving in the gusts, enough to allow some brief signal drop/loss. Is that possible...?

I associate highest directionality (is that a word?) with best forward gain, all other things being equal and assuming the antenna is aimed correctly. What other UHF antenna is there with equal forward gain vs. the 4228 that is more directional?

I have been considering the 4228 (I'm deep fringe) but wind loading is a concern for me - it seems like hanging a sail out there vs. a yagi.

Comments appreciated...

 

[Rick0725]

I tested recently the cm 4228 at my home versus the uhf performance on my winegard hd8200p. It was on a windy day. I got terrible multipath with the cm4228 during the test. I took it down and tied the 2 screens together tightly thinking the same thing you mentioned.

I reinstalled and the multi path was still present. hooked the hd8200p back up and the multipath was tamed. I felt the uhf performance on the 8200p was just as good or better on some of my weaker channels.

I have read good reports on the Televes DAT-75, AntennasDirect XG91, Blake JBX21WB...Im sticking with my winegard hd8200p...one of the few where the cm4228 did not work out.

here is some reading

http://www.hdtvprimer.com/ANTENNAS/comparing.html

http://www.atechfabrication.com/reception_solutions.htm

http://www.geocities.com/toddemslie/UHF-TV-DX.html

 

[bhelms]

Tks, Rick0725! I'll look into the links (already familiar with the first one). With good weather finally upon us in my locale, my near-term objective is to solve this OTA thing once and for all! In my case all present and future digitals are on UHF and coming from essentially the same direction except for one, but I already receive that one fine with an existing ancient RS VU-160 antenna pointed toward the others. I'll leave that one up for now - it also gives fair performance on a few analogs that'll be around for a few more years I guess. Since my earlier post I looked into the Winegard PR-9032 yagi - might give that one a try vs. the 4228. I just need to find a "local" dealer...

PS - I know what multipath looks like in an analog signal, and I know that multipath in a digital signal results in pixelation, but pixelation can be due to other causes. How can one tell the difference ??

Tks again and BRgds...

 

[mdonnelly]

I have an indoor antenna (Silver Sensor), and still have freezes when it gets windy. I think in my case it has less to do with the trees, and more to do with the towers.

 

[Rick0725]

What you are experiencing is a form of multipath interferience .

you will likely see dropouts when the wind blows because the strong and weak spots of the uhf signal will move around as the tree deforms and the branches move about.

The effect is called wave diffraction and overlapping fields.

It is common on uhf on windy day and will be worsened by climate temperature inversions called ducting.

Experienced yesterday on a service call. The levels on the meter were all over the place and could not perform the maintenance. had to scedule it for another day.

 

[MaD MiKe]

I have harvested my info for area code 61254-9592 from antennaweb.org for and installed a CM4228 tethered to a CM-058-3 tuned for channel 58 stacked on top of a CM3018 (3018 is working great). I started rotating the antenna using the 274° and ended up roatating the antenna back and forth a few degrees to reach the strongest signal strength from the 58 tower (which is 17.3 miles) but I am displeased with the drop outs of the 4228. BUT I have trees in the 4228 path and we are just starting the spring growing season so the leaves aren't on the Pin Oaks yet . When the wind is'nt blowing I receive a signal strength of 80% to 90% (on the 4228) and a wonderful pic on 58, I am more than willing to play with another antenna and in this discussion I see mention of a UHF Yagi, so if someone can give me some idea of what model UHF Yagi I might need I am more than willing to give it a try.. OR if you have any home brew ideas I might try to make the 4228 work I am open for any and all ideas..

I purchased the tripod and 10' mast at a reputable electronics store but I would like to mention that the mast the antennas are mounted on wobbles and shakes pretty good when the wind blows so would you think I might start with a 10' stick of 1 1/2" schedule 40 pipe might be in order first???

Thanks as always..

 

[Rick0725]

Schedule 40 is a good idea but is heavy. Make sure to purchase stainless steel pipe so it will not rust as quickly.

You can also try a thrust bearing (#tb-105), sold at stark electronics. Which will give the long pipe more support.

http://www.starkelectronic.com/cmmatv.htm#rotor

Another thing you can try. On the cm 4228 adjust the 2 screens till they just touch and secure them together with 7 nylon ties equally spaced from top to bottom. This will prevent the screen from easily flopping about in the wind.

 

[MaD MiKe]

Got up on the roof and lowered the 4228 and 3018 to just above the tripod, with the 4228 at least a full wave length from the 3018, to alleviate the shake, rattle and roll and I got 80% to 90% signal with fewer dropouts on channel 58, but the limbs are a movin in the wind and the leaves are still a growin..

Before I go and spend money on a UHF Yagi or stiffer mast, I'm gonna wait until I get the vip622 installed (this Friday I hope) and see how it compares to the Humax HFA100 tuner I am using as there might be a difference in signal recognition and I might not have as big a problem with OTA as I think.. I've only messed with rotating the 4228 about 5° to 10° clockwise to counterclockwise from the required 274° but I feel I'm wasting my time until I get the VIP..

But the wheels are still a turnin and open for any ideas!!!!

OOOPS!! I almost forgot while I was messing with the antenna I tied the two screens together..

 

[MaD MiKe]

What if I put a good preamp on the 4228 and if so will it affect the 3018 with the antenna joiner in place?? As I said before I have an 80% to 90% signal on channel 58 when the wind isn't blowing..



Just a thought and I will wait until the vip622 install before the preamp or anyother adjustments to the 4228, but the wheels keep on a turnin...

 

[Rick0725]

****first thing to do is observe how the wind affects your install****

the problem may be as simple as this.

-do the screens flop about in the wind...secure them together with nylon ties

-does the antenna shimmy and shake on the mast when the wind blows.
shorten the mast
if you are using a rotor, install a thrust bearing to lessen the load.

-if you want to try a preamp suggest the winegard hdp-269 amp...the other higher gain amps will overload at your distance from the towers and amplify after the joiner.

-the newer generation tuners are less prone to multipath (5th generation chipset)

 

[ralfyguy]

the newer generation tuners are less prone to multipath (5th generation chipset)

What is built in the ViP622?

 

[Rick0725]

just read at the avs forum that the 5th gen has problems with signal overload.

there is always something.

Sorry do not know which receivers have the new chip set.

 

[MaD MiKe]

****first thing to do is observe how the wind affects your install****

the problem may be as simple as this.

-do the screens flop about in the wind...secure them together with nylon ties

-does the antenna shimmy and shake on the mast when the wind blows.
shorten the mast
if you are using a rotor, install a thrust bearing to lessen the load.

-if you want to try a preamp suggest the winegard hdp-269 amp...the other higher gain amps will overload at your distance from the towers and amplify after the joiner.

-the newer generation tuners are less prone to multipath (5th generation chipset)

While reconnoitering the install, thanks Rick, I got to thinking about the preamp and I thought over the signal strength and I figured a preamp would be overkill in an 80% signal situation.. It was either the antenna or the tuner...


In the surveying my install I also determined the antenna with the most wind load was the 4228 and as the wind mostly comes from the West and the 4228 is pointed West so I reversed the positon of the 3018, it's above the 4228 now, to put the 4228 just above one of the two fulcrum points which would be the top of the tripod.. With a few trips up and down the ladder I am pulling in an unflatering 80% signal from the 4228 on channel 58 and so far still pulling rock solid signals from the 3018.. This could be the answer to "my area related delima" but only time will tell....



I won't mess with anything else until the 622 is installed but so far I am happy with my OTA signals..

Thansk to all...

 

[MaD MiKe]

Well the 622 is intalled so I got a new mast, a piece of 1' galvanized water pipe and a cap for the top, and intalled the 3018 on top and the 4228 on the bottom and I "think" I solved the problem with wind changing the angle of the antennas and cauing dropouts.. Only time and weather will tell but if I have to jump up on the roof a few times to tweak I still feel I have the best I can afford at the moment..

Question to the pros: Has anyone of you taken a reject dish 500 and used it for a reflector instead of the corner array that is normally used for a Yagi ???

Just thinkin and a tinkerin...