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Discussion Starter · #1 ·
I just got a Panasonic receiver (open box from Crutchfield) and hooked it into my preamplified antenna system (see related thread: Does a preamp cure all?)


In summary, I have a Radio Shack U120 antenna with a CM 7775 preamp. Analog reception goes from superior on the nearest stations (approx distance to towers of 20 miles) to rather fuzzy color on distant channels (75 miles.)


Now, the problem: One of the channels I'm supposed to get (in the red zone on Antennaweb.org) on DTV doesn't come in. The Panasonic lacks a signal strength meter, so I'm left looking at the blinking red and green lights inside the box. I get red+green. Never just green, like I do on the local DTV station. I'm assuming that this means I'm getting "some signal, with lots of errors" but not enough to lock in on and actually show anything. Is this right? I'm getting the same sort of thing, though less frequently, with the distant DTV stations.


I'm rather disappointed, since I expected to get a station in the "red zone" without any major problems. I know the 75+ mile stations are a stretch. I accepted that as inevitable. Any ideas on the closer, stronger one?
 

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Sounds like multipath or overload.


Don't worry about not having a tuning meter, most aren't designed to be very useful anyway. Get a real meter if you want to really see what's going on or a spectrum analyzer would be even better.


A signal meter reading in DB will tell you if you have enough signal. I use a Sencore which is one of the cheapest that reads digital, but an old used analog meter is better than nothing, and should be available cheap. Spectrum analyzer will show you most multipath problems too.


If your signal levels are ALL within a reasonable range like -40 DB to -10 db ahead of the preamp. Then your problems are multipath.


You need to experiment:


1 Try without the preamp.

2 Rotate your antenna.

3 Try more directional antenna.

4 Try to borrow a better tuner (Samsung or Zenith?)

5 Go higher.


Sounds like you have two problems: Local stations and 75 mile ones.


For locals: How close are you? How much power do they have? Analog will overload a preamp just as much as a digital one, so check all your channels.


If you are within 40 miles you should be able to get any local stations without a preamp (you did say it is flat out there.), unless the station is just trying to cover around their studio with a 5 watt transmitter. Check with your stations to see what power they are actually using and if they are broadcasting in your direction if their antenna is directional. They can also tell you if you have any close neighbors receiving their signals ok.


For the distant ones: You are trying to go very far. Check on the power as above. Also plan on maybe needing to filter out the locals so you can amplify the distant ones, and you may need to stack antennas and go up like 50-75 feet as well. And you can go to separate antennas that are tuned perhaps for your distant stations.


You might try a Winegard preamp with the 19 db gain, as a compromise, to reduce your local overloading if that is happening.


Sounds like something must be very wrong with your antenna, since you are having problems even with your local stations.


I see in your other post you have an analog and digital on the same channel. you can forget about that one, unless the analog switches off.
 

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Discussion Starter · #3 ·
Quote:
Originally posted by jhe
Sounds like multipath or overload.


A signal meter reading in DB will tell you if you have enough signal.

If your signal levels are ALL within a reasonable range like -40 DB to -10 db ahead of the preamp. Then your problems are multipath.
Well, I've already invested far too much money in this wild goose chase as it is. I'm not about to go out and buy more equipment. At this point, I'm debating just sending as much as I can back to cut my losses.

Quote:
You need to experiment:


1 Try without the preamp.

2 Rotate your antenna.

3 Try more directional antenna.

4 Try to borrow a better tuner (Samsung or Zenith?)

5 Go higher.
(1) I may try to cut out the preamp, but I doubt it's the problem at this point. More on that later...


(2) I've been rotating the antenna as fine as I can. I only get the "intermittent blinking" lights in a very localized direction - the same one the tower conveniently happens to be located in. :)


(3) I already have a rather directional antenna, so I'm not sure how much more directional I could go.


(4) I know of no one in my area with a tuner that I could borrow.


(5) Due to my lack of real-world skills in construction and mechanics, I'm already as high as I can reasonably go, which is about 15-20 feet off the ground.

Quote:
Sounds like you have two problems: Local stations and 75 mile ones.


For locals: How close are you? How much power do they have? Analog will overload a preamp just as much as a digital one, so check all your channels.
The nearest locals (2 UHF) are 25 miles. The analog UHF is at 1400kW. It looks absolutely beautiful! No reception artifacts. No problems at all. (If any station would be overloading the amplifier, this would be it. Wouldn't I see something on the screen to indicate overloading? Multicolored static? Weird banding in certain color ranges? Something?) The digital UHF is at 1000kW. It comes in perfectly, provided I'm pointed somewhere reasonably near the tower location. Steady green indicator light, no red.


There are also two UHF stations almost next door (2-4 miles) but they're running at 1kW and 3kW.


The station I'm trying to pull in from further away is listed at just under 1000kW. I'm technically in the "grade B" contour for their VHF signal. I estimate tower distance at 40-50 miles. Line of sight is impossible, even with a very tall tower, due to a hill within 2 miles of my house in that direction. Note that with the UHF antenna, I was able to receive a very staticy picture from the low-VHF tower. I don't have a VHF antenna to see what reception would look like. This is my only chance at a CBS affiliate, and this is a slam-dunk win or lose station. If I get it, I'm happy and everything stays. If I don't, I'm frustrated and transformed from an HDTV advocate to a disillusioned, tied-to-crappy-cable viewer.

Quote:
Sounds like something must be very wrong with your antenna, since you are having problems even with your local stations.
Well, I guess "local" is a relative term. My nearest UHF stations are all perfect, digital or analog. It's that middle-distance between impossible and perfect that I'm struggling with. And given that my analog long-distance reception is actually better than Grade B predictions would indicate (including the direction with the hill,) I have to think it's working.


(In the interest of full disclosure, there are two antenna installers in town and both of them refused to install an antenna at my location at all, stating that I was "in a valley" and too near a high-power line that's leaking EM all over the place. I grew up in a valley in PA. This ain't no valley. The EM seems to be restricted mostly to the AM band. FM and UHF seem unaffected. I suspected that their refusal might have been related to the fact that it was the middle of winter.)


My only alternative that I can think of at this point is to order two Channel Master antennas and set up a vertical stack (lacking the technical know-how to rig a horizontal stack such that it could stand up to the 70-90 mph gusts I seem to see on a routine basis.) But in all honesty, I've already blown $700 to get one channel. At what point do you give up?
 

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Discussion Starter · #4 ·
Quote:
Originally posted by sregener


The station I'm trying to pull in from further away is listed at just under 1000kW.
Well, nevermind me. I contacted the station engineer (tv station web sites with contact information are wonderful!) and found out that they have a temporary tower on their broadcast studio at low power and 225ft. Needless to say, the fact that I'm getting *anything* from them at this point bodes well for their future high power/high elevation plans.


Goes to show that the information on some web sites stating "current broadcasting ERP" aren't all that useful. :-(


Anyway, thanks for your help. I guess I'll be keeping that equipment after all.
 

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sregener,


1 Hey, I didn't mean to discourage you! I know it is frustrating, but I've been getting HDTV for 3 years or so now and I'm still making small improvements. I have a dual Blake horizontal stack, and I'm thinking of trying a quad stack next! Don't need it in the winter, but a bit more gain would help me in the summer..... But like you, I'm not sure it is worth the effort to just get one channel better in the daytime. It is pretty solid at night.


2 Regarding equipment: I held off buying a signal meter for years. Now that I have one I wish I bought it 30 years ago. My meter cost a lot, but friends of mine have found analog meters on Ebay that they found useful and were quite cheap, like $50-100. With the useless meters in tuners, that is worth it just to help aim the antenna, or see if the station has cut their power, as they seem to be doing around here.


3 The Winegard preamps works better than the Titan for me, I think because it handles my locals better with less overload.


4 Your blinking lights only in the transmitter direction sounds like a good sign. I have like 3 hills that I can receive off of at times as well.


5 Your antenna may not be directional enough. I started with Winegards, went to Channel Master 4248's and then Blakes. Finally had to go with the best of the bunch, which for me was the Blakes, and use a horizontal stack. See Glenn's Mt Wilson thread for more on stacking. A horizontal UHF stack still has less wind loading than lots of all-channel antennas people put up around here.


6 Tuners made all the difference for me, and I bought my Samsung at Best Buy, planning to take it back if it worked like I expected. Unfortunately it worked better, and I had to sell my RCA instead. So see if you can find a store to "loan" you a different tuner to try out, after you get everything else as good as you can.


7 Your height is not very high. But I can see why you may not want to go higher. I use a tower to get there safely and easily. FCC expects outdoor antennas are typically at 30 feet.


8 Glad you are getting locals ok. The 1.4 Meg watt station sounds very powerful even at 25 miles. One question is which stations are blocked by the hill you mention.


Without a meter overload is hard to check for. Sometimes you can tell a lot with an adjustable attenuator on the input of the preamp. If you cut the signal going in and it helps you can be sure you have overload.


Analog stations will show overload, but problem is each station may not show it equally. You could have a problem at a particular frequency that just happens to match the digital station you are trying to get. And digital ones won't show it except by dissappearing.


9 Your distant station you say is listed at 1000 KW or so. Be sure to check with the station and make sure they are really at their allowed power. The FCC decided to let stations cut power to save electricity during the transition, and some are doing it.


40-50 miles is very encouraging. Much better than the 70 miles you mentioned! With the curvature of the earth the difference should help you a lot here.


10 So it sounds like your main problem is that hill at 2 miles:

You say the analog station is VHF so reception of that doesn't tell you much, since VHF will bend over and around the hill much more than UHF. Could be great for you in the long run if the station keeps the VHF frequency. Then you'll just need a VHF antenna.


So how high is the hill? Is your antenna 20 feet from clearing the top, or 500 feet under it? And how about moving sideways? Can you see around it more from one corner of your property? Every little bit helps.


Another question is is that your only hill? You are in bad shape with a big hill blocking your line of sight for a 50 mile away station. It is much worse if you have any other hills that see the station directly and reflect signals back toward you as well.


11 I doubt you have to worry about the power lines. I have some near me too, and like you say they kill my AM radio.


12 Maybe you can get an installer to rent or loan you some test equipment?


13 Your hill could be blocking a lot of signal depending on the size at 2 miles. That is about the distance to the hill blocking me, and it cuts my signals by 20-30 db I estimate.

(I used a dipole on my meter and checked at home, and then in an tall building that could see over the hill.) The really frustrating thing is my hill is not that big, and any other house on my street would be able to see around one side or the other of it. All you can do is to go higher or add more gain. The hill makes multipath problems likely so a horizontal stack should help you more.


14 Are there any 50 mile away UHF stations you can receive that are analog, and have to go through the hill? You could then maybe see the effects of changing heights, and antenna locations with them, for signal strength.
 

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The 7775 pre-amp is UHF only. You might see if you can swap it for a 7777, which does both VHF and UHF. It also allows separate inputs for VHF and UHF, if you end up with a separate VHF antenna.
 

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Discussion Starter · #7 ·
Quote:
Originally posted by jhe
Your antenna may not be directional enough. I started with Winegards, went to Channel Master 4248's and then Blakes. Finally had to go with the best of the bunch, which for me was the Blakes, and use a horizontal stack. See Glenn's Mt Wilson thread for more on stacking. A horizontal UHF stack still has less wind loading than lots of all-channel antennas people put up around here.
Just out of curiosity, what's the gain difference between a CM 4248 and a Blake? Or is it just more directional? (I looked and the most expensive Blake I could find was $170+shipping. No word on how big that puppy was. It did, however, look like a beast.)


I've looked at the stacking stuff. For right now, I'll probably stick with a single as I've got a barely functioning rotor that I don't want to replace. (I say barely because it sticks at one particular spot, requiring a visit to the roof to unstick it. Fortunately, I get all my directions with stations without a visit.) But I am interested in getting more signal, if that's possible. Would the Blake do it, and are we talking a small or a large gain?
 

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sregener,


I'm about to order a Blake, myself. The gain looks to be 2-3dB over the CM 3023 (from what I can tell). It weighs 12 lbs. and I think it's about 7-8' long (not too bad). Oh, and the F/B on the JBX21WB looks to be quite a bit more than the CM.


I want to get a K-band version as that might tweak a little bit more gain from CHs. 14-50 and that's the range I need (the only thing I have over 50 is a strong local at 55 and it should do fine on that).


I'm waiting on a response back from [email protected] (the address I was given when I called hi-rez - or hometheater1..same place).
 

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Quote:
Originally posted by sregener



Just out of curiosity, what's the gain difference between a CM 4248 and a Blake? Or is it just more directional? (I looked and the most expensive Blake I could find was $170+shipping. ..............................


I've looked at the stacking stuff. For right now, I'll probably stick with a single as I've got a barely functioning rotor that I don't want to replace. (I say barely because it sticks at one particular spot, requiring a visit to the roof to unstick it.


But I am interested in getting more signal, if that's possible. Would the Blake do it, and are we talking a small or a large gain?
Regarding Blakes, there are several kinds. I got the JBX21-B because that antenna is tuned for max gain where I need it for my particular channels, and the JBX series is the one that is supposed to be best for multipath.


The Wideband Blakes have less gain, but cover more channels well. Then there are the other types, some of which have more gain esp at the lower channels but they are more like standard yagis, and may be less good for multipath.


In anycase you can see the gain curves on the Blake web site at http://www.blake-aerials.co.uk They also have a page somewhere with a conversion chart between the British channel numbers and the US numbers.


In the antenna posts I listed the antennas I use or have tried and I rated 4 4248's about equal to 2 Blakes. They would also be about equal to one Parascope, which unfortunately is off the market now! Some very expensive antennas have been listed on the forum from companies in Canada, but I know of no super gain antennas that are affordable now. Yagi gain is mostly related to boom length as I understand it (more so than number of elements) and a little extra can be achieved by peaking for a smaller frequency range.


So compare the Blake curves at the channels you want, and see http://www.starkelectronic.com for gain ranges for the 4248. Which is best gain wise depends a lot on the channels you care about. Even the so-called wide band antennas may peak in the mid-range or in the high end, depending on the design. Without parabolics there's not much you can do to boost gain without going to stacking. Stacking gives you around a net 2.5 db each time you double the antennas. For really high gain some people here have suggested using big satellite dishes and replacing the feed horn with a bow tie pickup antenna.


As to your rotor: I am using a Channel Master rotor. My wind load turns it sometimes, but so far it has not gotton stuck. I do use it however with a big bearing about 3 ft up from the rotor, which helps. Still I may want to get a heavy duty rotor someday like a hy-gain, but the Channel Master seems to work well so far and is cheap.


If it is really only one channel you are missing you may want to look into building or buying a cut yagi tuned just for that channel. If you make one you could go very long and mount it separate from your rotor, just to get that distant channel. Big hassle, but may be the best way to get more gain other than by going up higher. Someday I want a 70 ft electric telescoping tower for my antennas, but can't afford it yet!
 

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I still cant believe the POS Panny doesnt have a signal meter. I dont care whether or not they really prove anything it's still should be there. I thought my Dish 6000 was bad enuff just not having an audio tone for signal strengths but at least it has a bar graph.


My Mitsu has both and theres no question that the bar graph is virtuous. It's plain and simple. If the graph can hit 37 out of 100 I can get a stable picture. If it doesnt, I wont. But I can get readings all day of 24 and 30, or even less naturally if I move the antenna far enough. If all a person has is blinking lights how do you really know where you're at. If it's going to blink green/red at the equivalent of 18, 21 and 24 just as easily as 30 what does that really tell me? Whereas if I can actually see 30 as opposed to 21 I know I have a shot with more tweaking or a better antenna. If I already have a good antenna and/or amp and after major tweaking 21 or 24 is the best I can get, I know I'm SOL.


What does the Panny assume, that you should either get a picture or not and if not, it's not worth the trouble of telling you how "close" you are?


As opposed to ordering antennas that might not do any good at all and then you have the hassle of sending them back or whatever, it's too bad you couldnt either rent a meter as jhe mentioned or just even go to Best Buy and buy a STB that has a meter for experimentations sake and then just take it back after you have a handle on whats really going on.
 
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