AVS Forum banner

Status
Not open for further replies.
1 - 20 of 42 Posts

·
Registered
Joined
·
168 Posts
Discussion Starter · #1 ·
Hi guys--


From lurking around this section of the forum, I learned enough to go out and purchase an STB for HDTV OTA stuff. I have a Hughes E86 without DirecTV activation--just using it to tune/recieve OTA. So--here's a question--I had a professional installer come in to do the antenna. He installed a 4 bay antenna (don't know a heck of a lot about them), I believe. It looks a lot like this:
http://www.warrenelectronics.com/antennas/4221.htm

It has 4 bow-ties, etc. He installed it in the attic.


Anyway, I live adjacent to a busy street and I'm having problems with a couple of channels. My Fox affiliate (22-2 in Seattle--I can't recieve Ch 13-1 or 13-2) breaks up when a large bus goes by (anywhere from 6-8 times an hour) and my PBS affiliate (KCTS--9-2; they run a gorgeous HDTV loop at night) breaks up completely when any cars go by (read: all the freakin' time). :)


So--is there anything I can do? The installer has been out a couple of times, and this is the best placement that he says he can give. I get the feeling he's just tired of fiddling with it. I get 100% reception on these until traffic blocks them out. Can I use a second antenna--maybe an omni-directional number like this:
http://www.warrenelectronics.com/ant...negard_ant.htm

in tandem with my current antenna? Can you even do that? Anyone have any suggestions?


Yes, I've been to antennaweb.org--I'm in the yellow. :)
 

·
Registered
Joined
·
957 Posts
If you can put it outside and get elevation you should get better results.

Before you move it out of the attic you might try a rotator to tweak it and see if you can find a place where the multipath does not wipe out your signal.


Also If you can get it in your attic the $20 radio shack Yagi might be all you need. The Shack has a good return policy and if it does not help you take it back.


The local HDTV and reception forum has a lot of information on what we are using in the Seattle area.
 

·
Registered
Joined
·
2,751 Posts
Just some ideas:


Maybe you could try a vertical stack of two small yagis to reduce the vertical acceptance of the antenna so the traffic doesn't interfere? Or perhaps create a shield to block signal from below?
 

·
Registered
Joined
·
168 Posts
Discussion Starter · #5 ·
Weird. I'd heard of multipath, but never really knew what it was. Can that be the reason why it's happening? A weird multipath signal bouncing off the traffic?
 

·
Registered
Joined
·
168 Posts
Discussion Starter · #6 ·
Yeah, I took some time and watched 9-2 while it was breaking up due to traffic, and it does seem that another channel is breaking in every once in a while. When it pixellates and breaks down, every now and again, an image from an entirely different station sometimes blinks in. I'm guessing this is multipath? Now that I think about it, if it is, then an omnidirectional antenna would be craptacular for sure.


So, is there a way to shield it from the traffic? I've already spent a good amount on the install--I'd like to not drop another load of cash on an installation I'll be moving in another few months. Is there a lo-tech way to block multipath from the traffic directly below and in front of my antenna?
 

·
Registered
Joined
·
3,080 Posts
What area of Seattle are you located in? How close is the street and traffic to the line of sight path between your antenna and the transmitter towers on Capitol Hill? How much difference in direction is there to Queen Anne Hill from your site (compared to Capitol Hill)?


How strong is your received signal? Have you tried an attenuator as a means of reducing the total power so the reflected multipath signals might go below the receiver threshhold? An inexpensive variable attenuator from Radio Shack could let you experiment with this.


Just thinking out loud here. More info about your location in relation to the transmitters would help. You could look up your address on antennaweb.org and copy and paste the station list here.
 

·
Registered
Joined
·
168 Posts
Discussion Starter · #8 ·
I'm just north of Greenlake--one block from the lake, and have 100% signal before multipath pixellates it as traffic on the adjacent street goes by.


Here's my antennaweb data. (I'm in the yellow for all stations that I care about):

Digital Antenna Type Call Sign Channel Network City State Live Date Compass

Orientation

yellow KOMO 4 ABC Seattle WA 174°

yellow KING 5 NBC Seattle WA 172°

yellow KIRO 7 CBS Seattle WA 177°

yellow KCTS 9 PBS Seattle WA 147°

yellow KSTW 11 UPN Tacoma WA 148°

* yellow KTBW-DT 14 TBN Tacoma WA May 1 2003 227°

yellow KONG 16 IND Everett WA 172°

* yellow KCPQ-DT 18 FOX Tacoma WA Now Live 228°

* yellow KTWB-DT 25 WB Seattle WA Now Live 147°

* yellow KONG-DT 31 IND Everett WA Now Live 172°

* yellow KWPX-DT 32 PAX Bellevue WA Now Live 108°

* yellow KOMO-DT 38 ABC Seattle WA Now Live 174°

* yellow KIRO-DT 39 CBS Seattle WA Now Live 177°

* yellow KCTS-DT 41 PBS Seattle WA Now Live 147°

* yellow KWDK-DT 42 DAY Tacoma WA Jan 1 2003 108°

* yellow KHCV-DT 44 IND Seattle WA Mar 1 2003 108°

* yellow KING-DT 48 NBC Seattle WA Now Live 172°

* yellow KWOG-DT 50 IND Bellevue WA Now Live 108°

green KTWB 22 WB Seattle WA 147°

lt green KCPQ 13 FOX Tacoma WA 228°

lt green KTBW 20 TBN Tacoma WA 227°

* lt green KBTC-DT 27 PBS Tacoma WA May 1 2003 178°

lt green KWPX 33 PAX Bellevue WA 108°

lt green KHCV 45 IND Seattle WA 108°

lt green KWOG 51 IND Bellevue WA 108°

lt green KWDK 56 DAY Tacoma WA 108°

violet KBTC 28 PBS Tacoma WA 178°

violet K54AO 54 CBS Bremerton WA 241°

http://arcimsmaps.decisionmark.com/C...1929802903.png


80th is the busy street.
 

·
Banned
Joined
·
3,023 Posts
You must be extremely close to the transmitters with all those strong YELLOW signal levels. That will make multipath more possible since even reflected signals will be strong, so trying an attenuator might indeed be worthwhile.
 

·
Registered
Joined
·
3,080 Posts
Andy, you are very close to Queen Anne Hill there, and not much farther from Capitol Hill.


Did the installer mount the antenna perpendicular to the ground (i.e., is the mast plumb and the antenna parallel to the mast)?


For your location, being so close and at somewhat low elevation, I would think you might be able to tilt/aim the antenna upward, away from the ground and street, and still not have any trouble with primary signal strength from the towers. This just might take the street reflections partially out of the vertical reception range of the antenna. I don't know the vertical reception range/pattern for the antenna, nor do I know how far above the street (and tops of cars/trucks/busses) the antenna is mounted.


You have plenty of signal strength to work with so if you lose a bit aiming the antenna upward you will still be well within working range for the primary signals. By aiming further away from the street you will improving the ratio of good primary (direct) signals to bad (reflected from the street) signals.


This all applies if you are convinced that traffic in the street directly correlates to your instances of breakups.


There is also a possibility that you are getting reflections from the downtown high rise buildings. If this is the cause, re-aiming the antenna upward will be less helpful, if at all. But those reflected signals are still not as strong as the direct signals if you can see the tops of the transmitter towers on Queen Anne Hill and Capitol Hill. If you canot see the towers, your stronger signal may be from the reflections. The multipath issue is caused by getting the same signal at different times caused by differences in path distance for the direct and each reflected signal.


I still think a variable attenuator would be the easiest and best first attempt. I tried to look one up just now at Radio Shack's web site but I can't get into their site for some reason right now. See if they have one rated at 0 to 25 or 30 dB attenuation.


Can you say more about what you can and cannot see from your antenna site? QA towers? CH towers? Downtown buildings behind Lake Union? I just can't remember the lay of the land there.
 

·
Registered
Joined
·
1,132 Posts
Bottom line..you just need more signal strength at the antenna to overcome any interference along the line between transmitters and antenna.
 

·
Registered
Joined
·
3,080 Posts
magic123:


I think Andy's issue is more likely too much signal strength as he is very close to 3 towers and not much farther from 3 more. It could be that a reduction in signal strength will do him some good.
 

·
Super Moderator
Joined
·
18,458 Posts
Andy..

At this point, I'd drop back and try a pair of ordinary rabbit ears. Ten bucks at Radio Shack. Move them around the room until you find the sweet spot for each station (it's bound to be a little different). Keep the receipt and, if it doesn't work, take 'em back.


Doc
 

·
Registered
Joined
·
1,132 Posts
I have found the best type of antenna for me is a highly directional antenna..zeroed in on the highest signal with a rotator. I have found less than 10 degrees can make a difference in receiving a near-perfect signal with zero dropouts and no blocking. I think it very important to make that primary signal so strong at your antenna that nothing will interfere with it. At least, this has been my experience. And I have signals up close and over 60 miles distant. I treat all signals the same way..just trying to get each one as strongly as is possible. I even believe a close by signal should be brought in as strongly as possible to overcome multipath problems, etc. I have never had these problems by the way. For me, signal strength is just about everything. It works wonders!
 

·
Registered
Joined
·
168 Posts
Discussion Starter · #15 ·
Wow, thanks for all the great suggestions, guys!

Signal strength isn't the problem--I'm pretty sure of that. All of the stations are absolutely pegged at 100% until a bus goes by and mutlipath fouls up the signal.


Dave, your post is very informative, thanks. To answer one or two questions, the installer put the 4-bay antenna in the attic (upstairs...second floor) and ended up zip-tying the antenna to the framing of the attic. I only glanced at it, but yes, it appears to be perpendicular to the ground plane--or rather perpendicular to horizontal (as I live on a hill). I'll have to wait for a clear day and grab some binoculars to really see if I have a clear line of sight--that might be a bit of a wait as we've had some crappy weather these past few days.


So--again, bear with me, I'm a bit of a newbie in the DTV/OTA world--I'm familiar with the concept of an attenuator--that is, I understand it would be for dialing down the signal strength altogether, but where would it be hooked up--what's the cost, etc? (I'll try to poke around on the radio shack website to find one...)


Is there no chance of creating a shield to block the street with? That is, a horizontal plane in front of the antenna to block nasty reflections from the cars passing by below? (The traffic passes below and directly in front of the antenna.) Anyone done this with any degree of success?
 

·
Registered
Joined
·
606 Posts
A metallic shield may replace the dynamic ghosts from cars with a static ghost (possibly quite strong) from the shield.
 

·
Super Moderator
Joined
·
18,458 Posts
Andy..

I'm serious. Try less antenna. Rabbit ears. Worked for a guy in downtown Cincinnati who had much the same problem.


Doc
 

·
Registered
Joined
·
168 Posts
Discussion Starter · #19 ·
Doc-


Really? Rabbit ears, huh? Well--I'll consider it. Would hate to find out that I needlessly plopped hundreds down on an install, you know? :) I'll see if I can find a pair.


I was considering trying a sheet or two of aluminum foil. That would definitely be the most low-cost solution. :)
 

·
Super Moderator
Joined
·
18,458 Posts
Andy..

If you're that close to the towers, using a high gain antenna can actually be a problem. I'm 15 miles away and can get all of the stations with rabbit ears. From my basement. My issue was airplanes. That sent me to an attic mounted yagi which works just fine. Even so, one of the UHF analog stations bleeds into adjacent channels rather heavily.


The guy in downtown Cincinatti is under 5 miles from all of the towers and was having multipath fits, mostly from other towers, the hills and the tall buildings. Tried the rabbit ears and voilia! No troubles, now.


Doc
 
1 - 20 of 42 Posts
Status
Not open for further replies.
Top