Antenna and Preamp problems.

[Wiggin78]

I have a Winegard 9095p UHF antenna on my roof. I was using a cheap Radioshack 10 db preamp and was getting good reception. I decided to try the winegard ap4800 preamp to get stations that are on the fringe of good reception. To my dismay I hooked the ap4800 up today and now I get worse reception than with the little preamp. I tried using a dc block and that didn't work. All the connections are fine. Does anyone have any ideas why this higher powered preamp would perform worse?

 

[mike_johnson]

Make sure you have DC power on the coax cable feeding the preamp. Use a voltmeter to see if you actually have power at the amp. (Check the output of the power inserter, too.) Also make sure you are using the Wineguard power inserter and not the Radio Shack one (the voltages are different.) The coax line between the power inserter and the preamp shouldn't have any splitters in it. (Most splitters won't pass DC power, but it sounds like you know that.)

I found a forgotten splitter in my attic that kept my amp from getting power. It's also possible you've gotten a bad unit, but it's more likely that it just isn't getting power.

Mike J

 

[Wiggin78]

I don't have any splitters but the line does have two female/female connectors to pass the coax. It is not one solid line and can't be. I don't know if those pass dc power. Do I need a dc block anywhere in the line?

 

[dishrich]

I don't understand what you are talking about with the "dc block" thing - you DON'T need one. (that's why they do NOT put one with the pre-amp ) Also, splices (as long as they are done properly) shouldn't have any affect on this. Also, I assume you are NOT trying to use BOTH the Winegard amp AND the RS 10db, right? That will most likely cause you more problems - you should ONLY need the Winegard pre-amp.

Also, exactly where did you put the actual pre-amp itself? (the box that goes outside at the antenna that does NOT have the AC cord) Did you make sure that you ran the antenna output into the ANT IN connection on the pre-amp, then the output of the pre-amp (market TO POWER SUPPLY) should go DIRECTLY to the PREAMP connection on the power supply, then the TV connection on the power supply would go to your TV(s). Is the LED on the power supply lit up?

Also, how close are you to any TV towers? I noticed that you bought an AP-4800, which is rated for 28db of gain. In my experience with these pre-amps (& I have installed dozens in different areas) this model has too much gain for most areas & is easily overloaded by strong locals stations, which can actually cause MORE problems than you solved. (but since we don't know WHERE you're at, I don't have a clue as to where your local towers are - hint: we CAN'T help you guys if we DON'T know where you are ) This is compounded by the fact you are using the largest UHF antenna Winegard makes. It can be to the point where these overloaded local stations can actually wipe out weaker stations accross the dial, or cause them to overload your TV tuner. (this is "cross-modulation") You might have been better off getting the AP-4700, which has 19db of gain, which is still plenty for most areas.

This is a common mistake that people make that don't work with this stuff regularly - if a small amp works good, then a large amp will always work GREAT - doesn't work like this. You can have TOO much of a good thing.

 

[Wiggin78]

Ok, of course I'm not using the 10db and the Winegard preamp together. As far as the DC Block goes i needed one when I had Voom and the 10db preamp had one as well. Considering I had better reception with the 10db preamp and a block i thought I might need one. I'm sure there are a lot of idiots out there but I have my system hooked up correctly. The antenna lead goes to the preamp antenna jack and the power supply preamp lead ends up[ in the antenna jack on the power supply. And the to tv jack heads to the Dish over the air jack. Now as far as my distance goes I am about 60 miles from the towers and they have very weak signals. Even with the 10db I couldn't get CBS & NBC from that area but was able to get FOX at around 60%. The reason I went with the large antenna and preamp is because I would like to get a couple of stations out of Sacramento which is about 100 miles from me. Now ABC and PBS are with in 28 miles of me so maybe there is some cross modualtion but after have decent results with the 10db I think the jump to 28db shouldn't make it worse any help is appreciated. Thanks.

 

[dishrich]

Now as far as my distance goes I am about 60 miles from the towers and they have very weak signals. Even with the 10db I couldn't get CBS & NBC from that area but was able to get FOX at around 60%. The reason I went with the large antenna and preamp is because I would like to get a couple of stations out of Sacramento which is about 100 miles from me. Now ABC and PBS are with in 28 miles of me so maybe there is some cross modualtion but after have decent results with the 10db I think the jump to 28db shouldn't make it worse any help is appreciated. Thanks.

First of all, you most likely won't get digital signals 100 miles away.
As far as the 28db not making much difference - I'm sorry but in fact, it can make a BIG difference. Again, I am telling you this from years of personal experience that you most likely have too much of a good thing. (uh, maybe that's why your BIGGER amp is NOT working as well as your SMALLER amp ) On top of this, if you are, in fact getting cross mod & it is going thru your digital stations, all it is going to do is basically wipe them out totally so that you get NOTHING on them, because the receiver can't cope with the x-mod interfearing with the digital channels. The sad thing is, that now that we are in a digital world, these types of problems are MUCH harder to pin down than in the analog world - obviously, you can SEE x-mod on an analog channel, but you can't on a digital channel. But you also have to remember that now instead of only having 2 locals stations overloading your pre-amp, you actually have 4. (2 digital & 2 analog) This could now be the point which is causing the amp to be overdriven.

My first choice would be to try the other amp I suggested, particulary if you can return it if it doesn't work for your needs. If you insist on keeping this high powered amp, then the only other thing to try is to put a trap on the antenna to knock down the nearby local stations some. It might work to the point of getting the x-mod down.

 

[JohnC]

I have a Winegard 9095p UHF antenna on my roof. I was using a cheap Radioshack 10 db preamp and was getting good reception. I decided to try the winegard ap4800 preamp to get stations that are on the fringe of good reception. To my dismay I hooked the ap4800 up today and now I get worse reception than with the little preamp. I tried using a dc block and that didn't work. All the connections are fine. Does anyone have any ideas why this higher powered preamp would perform worse?

I also have the Winegard 9095p UHF antenna mounted about 40 feet above ground level and use a Channel Master Titan 7777 preamp. I am 60 to 65 miles from the Atlanta digital towers over basically flat terrain and get perfect reception on all of the Atlanta digital stations except 2 that are only putting out 50 KW that I receive about half the time at night. The 7777 preamp is a very low noise preamp and improved the signal indicated by my 6000 by about 7% over that obtained with a similar gain (about 20 db) but higher noise Radio Shack preamp. The gain should be high enough to overcome the losses in the coax from the antenna to the receiver. You might have poor connections at one of the coax connections or a bad preamp. I have (2) 50 foot runs of RG6 with a ground block between the 50 foot sections. Another possibility is that you have one of the switches in the preamp set on the wrong position.

 

[Stacy A]

First of all, you most likely won't get digital signals 100 miles away.

I beg to differ. I live 120 Miles from Dallas and I have four of the digital stations locked into my 6000. I typically can only receive them after dark, but I do, in fact, pick them up. I use a channelmaster deep fringe UHF only coupled with a RS 30db pre-amp. My local channel towers are approximatley 65 miles northeast of me (Shreveport) and 45-50 miles west (Tyler/Longview). Using the high gain amp caused no loss of any of the closer channels, analog or digital. The one most subject to cross modulation (closest to me and highest in power transmission) did not go away.

It's not that I doubt anything you are saying. You obviously are a very experienced professional. It's just that according to what you are saying, I should have lost channels when I installed the system I have. And that was not the case at all. It did exactly what I wanted it to do: pick up Dallas OTA digitals and the digital PBS out of Shreveport which runs at a low power. I used to only be able to pick it up on nights when the skip was good. Now I can pick it up every night. I did lose some signal strength on my CBS digital out of Shreveport. It dropped from 90%+ to mid-80%. That was not a big deal.

 

[DrAlSmith]

The problem, as another reply mentioned, is overload of the pre-amp. This essentially creates noise across the whole OTA band to your receiver. I had a desire to receive a very distant PBS stations and installed a very large parabolic antenna with better than 20 db gain. But even this antenna was not able to receive a good signal, so I, like you, attached a very high gain, high quality pre-amp. Now the problem was the pre-amp was overdriven by strong stations, even when not directed at the nearby strong stations. To cure the problem, I had to resort to a spectrum analyzer to isolate those stations with excessively strong signals, then introduce a narrow-band RF filter prior to the pre-amp to reduce the signal strength for each specific station. In the end I had to use three of these filters tuned to each offending, strong RF signal. This did give the desired results: I can get a good signal on the weak, distant station. But if I did not like the challenge, I would have given up. And this solution requires an investment in filters besides the pre-amp, and access to an RF spectrum analyzer.

 

[dishrich]

I beg to differ. I live 120 Miles from Dallas and I have four of the digital stations locked into my 6000. I typically can only receive them after dark, but I do, in fact, pick them up.

Well, most "mortals" want to be able to pick up stations in the DAYTIME as well, which this guy seems to fall into this catagory. Most people do NOT go to this trouble to be able to watch something only a few hours a day. While I am sure there are people that DO this that are REALLY into TV, as I have done in my younger days, it's different now in the digital world. Obviously in the analog world, you can get something most times, even if the picture quality can vary much - in the digital world, you either get it or NOT! And in your case with trying to pull something in 100 miles away that "only comes in after dark", it's not worth the hassle to me. Especially in my case, since I now have access to 5 markets of local TV from across the country clearly through dishes, (not to mention the 4 HD stations from NY) it's not worth the hassle to me anymore to go through this via antenna.

I use a channelmaster deep fringe UHF only coupled with a RS 30db pre-amp. My local channel towers are approximatley 65 miles northeast of me (Shreveport) and 45-50 miles west (Tyler/Longview). Using the high gain amp caused no loss of any of the closer channels, analog or digital. The one most subject to cross modulation (closest to me and highest in power transmission) did not go away.

Uh, well - you just proved my point. Not sure if you realize this, but "45-50 miles" away is quite a bit different than 30 miles away, at least as far as overload to a pre-amp.

It's just that according to what you are saying, I should have lost channels when I installed the system I have. And that was not the case at all.

In YOUR case, I am NOT saying that at all - read my answer above.

It did exactly what I wanted it to do: pick up Dallas OTA digitals and the digital PBS out of Shreveport which runs at a low power. I used to only be able to pick it up on nights when the skip was good. Now I can pick it up every night. I did lose some signal strength on my CBS digital out of Shreveport. It dropped from 90%+ to mid-80%. That was not a big deal.

That's good - BUT, you are in a different situation.

I am NOT saying that it is NOT possible for the orginal poster to get what he wants, but he's gonna have to work at it, as well as spend some $$$ to accomplish this, just as Dr. Al said above. (who obviously has worked with this stuff for sometime as well)

And I guess a couple things I'd like to add back to the original poster...

-Also another point I forgot to add - you are dealing with an E* 811 receiver, which I read around here is not the best at dealing with "non-perfect" off-air signals. If you REALLY want some of these distant stations, you might want to try a better HD receiver. (to be blunt about it)

-You now have 2 people here giving you different solutions, but who are saying that you have the SAME problem of local overload, but you keep arguing about it. Have you thought about actually taking some of our advice - my solution would be the cheaper one & would be the easiest/cheapest to fix.

Also understand one thing - I DO NOT GUARANTEE 100% THIS WILL SOLVE YOUR PROBLEM, since I don't have the advantage of seeing your setup firsthand! But again, my experience tells me this would be the first place to start. You have to get into your mindset that BIGGER (ie: high-gain) IS NOT ALWAYS BETTER!

Also, have you given any thought to contacting a local antenna dealer for some help. (who will probably tell you the same things we have) It basically comes down to - HOW badly DO you want those distant stations?

 

[nomadicdude]

I've tried multiple experiments with a CM4228 and preamp CM7775 and 7777. Basically, dishrich is right - you are more than likely overloading the signal with 28db gain amplifier. The description of your problem is similar to mine - after I installed the preamp the reception was so bad that I went from getting 30 channels down to 5 channels!! The receiver refused to lock into the signals because of the amount of noise such a high gain amp generates. Bottomline: your amp is not going to improve antenna's signal acquiring skills. (I'm sure I will get flamed for saying this...)

Do most of the stations where you live broadcast out of the same general location? If you already tried this, ignore the suggestion. Since you are receiving a (weak) signal for the "fringe" stations, you may have more luck just reorienting your antenna. Believe it or not, good old fashioned trial and error helped me get the high frequency UHF channels (56 and above) - something the amps could never do.

 

[Carl B]

Wow, what a thread!

Anyway, the Winegard AP pre-amps use an AC power supply, not a DC power supply like the RS and CMs do. The conversion to DC for the pre-amp circuitry occurs in the pre-amp.

Digital (ATSC) and analog (NTSC) tuners are very different. ATSC tuners were designed to deal with CFM problems, whereas NTSC tuners were not. Amp overloading will affect analog reception considerably more than digital reception. The FCC and ATSC defined, tested, and specified that digital tuners had to deal with large differences in channel signal strength. A lot of the rap on pre-amps is based on VHF analog signal experience, not UHF digital signal experience.

Why would anyone receiving 30 DTV channels add a pre-amp? With digital, if you get a decent signal (no dropouts) that's as good as it gets. Higher signal strength doesn't help. Don't try to boost it, you'll only create new problems.

However, if you can't receive most available DTV channels or the signals are always dropping out, go ahead and use a good, low noise pre-amp like the CM 7775 or 7777. If you aren't receiving the channels, those pre-amps won't make the situation any worse.

Just my 2 cents!

 

[k4106]

If you have access to an analog receiver, use it to tune to the fox station in Sacramento with the 28db preamp installed. KXTL broadcasts on analog UHF channel 40 and you can easily judge whether you have cross channel interference/overload by looking at the picture on the screen.
I think the reason for using AC power through the coax is it prevents electrolysis at the connections.

 

[Wiggin78]

Well, I left for the weekend and didn't worry about my reception problems. After getting home from work today I did a digital scan of stations and 12 were found. before i was only getting 4. One of the stations I really wanted to pull in is FOX from Sacramento which is 160 miles from me. It is coming in between 63% and 72%. It does drop out now and again so I would like to fix that problem. I guess the preamp just needed to warm up over the weekend. I will continue to play with my setup until I can get both of the stations I want in HD. Only ABC in our area broadcasts HD so we have to resort to further away cities. Is it absurd to think that I can get a consistent signal from 160 miles away? I wouldn't care about all of this if E* would just figure out how to get NBC & FOX HD feeds.

 

[dishrich]

Digital (ATSC) and analog (NTSC) tuners are very different. ATSC tuners were designed to deal with CFM problems, whereas NTSC tuners were not. Amp overloading will affect analog reception considerably more than digital reception.

Sorry, but that's not entirely true. You have to realize that in today's off-air environment, you now have DOUBLE the number of off-air channels floating around today, since each local station is broadcasting 1 analog AND 1 digital station. (with some exceptions, of course) With this comes double the chance of x-mod into your preamp. It makes NO difference whatsoever that we are talking a digital or analog signal - the preamp does NOT know the difference between an analog & a digital carrier. BOTH can overload the amp & cause x-mod, period. Which leads me to my next point...

The FCC and ATSC defined, tested, and specified that digital tuners had to deal with large differences in channel signal strength. A lot of the rap on pre-amps is based on VHF analog signal experience, not UHF digital signal experience.

No, I'm basing it on ALL signal experience, digital & analog, VHF & UHF altogether. Also, I am NOT talking about the signal strength into the TUNER - I'm talking about the signal strength into the PRE-AMP itself. As I stated above, when an amp is overloaded by either analog OR digital signals, it will go into x-mod & will start "x-modding" stations across the dial, INCLUDING x-modding into digital carriers, either from another digital carrier OR analog carrier. Once this happens, the digital receiver cannot lock onto the desired carrier, because of all these other "spurs" that have infiltrated the desired carrier. There is nothing that can be done AFTER the pre-amp to cure this, except for reducing the input to the amp in the first place, either by reducing overall signal input, or trapping out the strong ones, like Dr.Al just described to you all. (you will need a SA to do this with)

As far as the "rap on pre-amps is based on VHF analog signal experience, not UHF digital signal experience", while I can't speak for anyone else, I will tell you that my experience has been predominately in a market where ALL of our local off-airs (except for one PBS) are UHF, both analog & digital. Now that my market now has 16+ off-airs, I have to be more careful now with preamps, as I just described to you above. I KNOW what I just described to you above to be fact & it has NOTHING to do with the overall signal strength going to the tuner itself.

However, if you can't receive most available DTV channels or the signals are always dropping out, go ahead and use a good, low noise pre-amp like the CM 7775 or 7777. If you aren't receiving the channels, those pre-amps won't make the situation any worse.

Here's the printed specs for the following amps: (I take it you already know these, right? )

CM 7775/7777: gain-26db / noise-2.0db
http://www.channelmaster.com/home.htm

Winegard AP4800: gain-28db / noise-2.7
Winegard AP4700: gain 19db / noise 2.9
http://www.channelmaster.com/home.htm

Again, the noise is NOT the issue here; it's the GAIN that IS the issue. (guys, you got to get out of this "bigger is better" mindset - you AIN'T buying a car here. )
Why do you guys think that Winegard & other manufacturers makes a lower gain (ie: high-input) amp in the first place?
Winegard even has antenna classes explaining all of this, but if you've done this for awhile, it's not that hard to understand.

 

[Wiggin78]

Ok, come 8pm here on the west coast I have lost my ability to watch the Sacramento channels. Do most stations increase their signal in the evening for Prime Time therefore causing cross modulation?

I can't send the preamp back so I would like to find a way to use it to get the Sacramento stations. If I have to block the local digitals to do so that is fine since they won't be broadcasting in HD for at least another 4 years. I would love to be able to make this setup work.

 

[dishrich]

I can't send the preamp back so I would like to find a way to use it to get the Sacramento stations. If I have to block the local digitals to do so that is fine since they won't be broadcasting in HD for at least another 4 years. I would love to be able to make this setup work.

Re-read DrAl's post - the filtering alone will cost you a LOT more than a new pre-amp...

(someone else try; I give up trying to convince him - I'm not gettin' paid enough...)

 

[Wiggin78]

Let me rehash what it is that I am trying to accomplish. I live about 60 miles from our local television stations that provide NBC, CBS, and FOX. These stations do send out digital signals but they do not broadcast in HD and won't for another 4 to 5 years. ABC & PBS are about 25 miles from me and do broadcast in HD but never come in over 72%. Sacramento's towers are about 150 - 160 miles from me and all of them broadcast in HD. I would like to be able to pull Sacramento's stations in rather than any of the closer non-HD stations. The engiDuring the day I am able to accomplish this with the HD9095P and 4800 preamp. However, at night all the channels drop out even ABC and PBS wich are 25 miles away. Everyone is saying that it is cross modulation which I agree with. Now, if I invest in the 4700 preamp is there a possibility that the Sacramento stations will come in consistently? If I try a trap instead what kind do I need to purchase?

 

[Carl B]

Please provide the channel numbers and location names (town/city) for the 25, 60, and 150 mile channels of which you speak. Also, provide your Zip Code. With that I'll do a little research and analysis for you regarding the feasibility of your goal.

No one can answer your hardware question with any certainty, even with the additional data I requested. However, there could be more fact-based recommendations forthcoming.

 

[Wiggin78]

ABC channel 34-01/RF 34 is located in Redding about 25 miles away
FOX channel 30-01/RF 20 is located in Chico about 60 miles away
NBC Channel 24-01/RF 36 is located in Chico about 60 miles away
CBS Channel 12-01/RF 43 is Located in Chico about 60 miles away

Stations I would like to receive but only receive intermittently now are:
FOX channel 40-01 is located in Sacramento about 150 miles away
NBC channel 3-01/RF 35 is located in Sacramento about 150 miles away

My zip code is 96073 and we sit on a large hill that has no obstructions.