Need a better OTA tuner..

[parisology]

Using vbox 3560 usb tuner now for a couple of years. But apparently my tv's tuner can pull in digital stations a lot better based on the amount of choppiness I see. What is the best PC tuner for a weak OTA signal area?

[captain_video]

The 3560 is one of the better tuners available for pulling in weak stations. It could be that your signal is actually too strong and causing the problems you're seeing. Try inserting an attenuator in the line and see if that helps. You could also use one or more splitters if you have them onhand. Just make sure you place a 75-ohm terminator on any unused ports.

I had similar issues on certain local channels but was able to switch to another affiliate further away that had a weaker signal. The problems disappeared immediately. I'm in between Baltimore and DC and get all of the networks for both markets. The Baltimore NBC station is only about 10 miles away and was having the same problem you described. The Washington NBC station is about 30-35 miles away and had none of the issues that the Baltimore station did. I found this strange because the Baltimore CBS, ABC, and Fox affiliates all broadcast from the exact same location (ABC, CBS, and NBC all use the same tower) and none of the other channels have issues. I can only guess that the NBC station has a more powerful transmitter than the other three channels.

BTW, I'm using six 3560's in my HTPC and like them better than the Hauppauge HVR-2250, HVR-950, OnAir USB HDTV-GT, and the HDHomeRun. I've tried them all but keep coming back to the VBox tuners.

[parisology]

The problem must be a weak signal. The vbox signalmeter won't run on vista so I don't know the numbers. Will have to boot xp to run it.

I am behind a hill from the transmitter, and have a 30ft mast, 8-bay bowtie and mast mounted amplifier. As I said, the tv works ok, but the vbox gives me a choppy result on a few stations, but others are ok. All transmitters are colocated.

[parisology]

Here are the vbox signal meter readings. Channel 21 (PBS) is choppy with vbox/btv but works perfectly with tv's built in tuner. Channel 7 (NBC) is also having problems. I think the only thing that will help in my location is raise the antenna a bit more, or try some low loss feed line, or get a new PC tuner.

Digital channel, % signal, reading

7 100% -2000 mDb
10 100% 7000
13 100% 4000
21 100% -2000
24 100% 4000
28 100% 3000

[Rich A]

Originally Posted by parisology

Here are the vbox signal meter readings. Channel 21 (PBS) is choppy with vbox/btv but works perfectly with tv's built in tuner. Channel 7 (NBC) is also having problems. I think the only thing that will help in my location is raise the antenna a bit more, or try some low loss feed line, or get a new PC tuner.

Digital channel, % signal, reading

7 100% -2000 mDb
10 100% 7000
13 100% 4000
21 100% -2000
24 100% 4000
28 100% 3000

Digital OTA reception problems CAN be caused by a too strong signal. You really should look at the actual transmitter parameters from those OTA signals.

For example, it could be that #'s 7 and 21 are way up in the UHF band while the others are down in the VHF band. Or vice verse.

Since both the problem stations are showing 100 percent signal levels to the tuners and yet show "strange" levels, my guess is that those two signals are either suffering from multipath or (more likely) are too strong.

What make and model antenna are you using? And what make and model of pre-amp are you using at the antenna? If you give me the call signs of those stations, I can get the FCC data from them.

Here's one example. While an antenna may be designed for UHF only, if the signals are strong enough, it sometimes can also receive VHF, albeit weak.

Antenna height also can be critical. Sometimes a better signal can be had by lowering the antenna.

Here are two PDF files that I highly recommend to anyone who is attempting to build their own home TV distribution system. While they are written specifically about Cable TV feeds, all the line loss etc. information is still applicable to OTA.

http://www.sencore.com/uploads/files/SignalLevels1.pdf
http://www.sencore.com/uploads/files/SignalLevels2.pdf

The one thing that is not addressed (because it isn't a problem on cable (closed) TV systems) is "multi path" and the possibility of wide differences in received signal strength for individual channels (in your case stations)

Those two things are really OTA problems only.

Here's a bunch of things to consider.

1. The stations are widely separated by frequencies (IE 60 to 900 MHz) Some may be in the 60 to 150 range and others from 150 up. This may result in problems if the antenna isn't designed for both, or the preamp also isn't designed for both.

2. You might have a multi-path problem. Where one or more of the signals are being received twice from two different directions. When that happens the signals are usually a few micro-seconds apart and the tuner is now seeing "double" which really causes strange things. Like a 100 percent signal but with many "phantom" signal drop outs.

3. you might be over-amplifying the signals so that the weak ones are okay but the strong ones are now over-amplified. Over amplifying a signal can be worse than a too weak signal. Especially with digital.

As for the okay reception in the TV, nobody will admit to it, but your average TV tuner is far more sophisticated than a PC use TV tuner.

After all, the TV manufacturer is selling you a several hundred (or thousand) dollar device that is made to receive TV. Some tuners are better than others and have sophisticated circuitry to reduce the errors caused by multi-path etc. Where would you expect to find a "better" tuner? In a $1,000 digital TV? Or a sub $100 PC tuner? Okay so why don't the PC tuner people use better stuff? I dunno? Or maybe it's not cost effective to "over-design" a superior digital tuner for a VERY small portion of people who "might" have a problem. Just look at the number of TVs sold compared to the number of PC based tuners. Maybe hundreds of thousands or more to one?

So the answer to your second question as to why the TV tuner works better is really simply that the whole RF input section and tuner in your typical TV is just plain better.

<edit> Sorry I missed that you were using an 8-bay bowtie antenna. That is usually only for UHF signals. Plus it has a much broader beamwidth than a long yagi type antenna. By having a wider beamwidth, it means it will receive signals from a wider compass bearing. So if two UHF stations were say at 45 degreen and 60 degrees that type of antenna will have a better chance to receive both when you aim between the two. The longer Yagi (multi-element arrays) has a sharper beam-width which means it would only see the station when pointed right at it and trying to split the general direction in the middle might result in not being able to see either station. Having a "wide beam width" antenna will of course make it more possible for multipath to happen.

Tell me the call signs of all the stations and I'll bet some are VHF and some are UHF. And your UHF antenna is of course going to work best with the UHF portion of the Pre-amp.

[parisology]

Thanks for the info. I gave the physical channel numbers.
Preamp: CM-7777
Antenna: CM-4228

My buying guide has been hdtvprimer.com.
Channel Master 4228
I chose this antenna since I needed some hiband vhf gain.

vhf KNIN-DT 9.1 CW CALDWELL, ID 32° 10

vhf KTVB-DT 7.1 NBC BOISE, ID 32° 7

uhf KBCI-DT 2.1 CBS BOISE, ID 31° 28

uhf KAID-DT 4.1 PBS BOISE, ID 31° 21

vhf KTRV-DT 12.1 FOX NAMPA, ID 32° 13

I am 10 miles from the tower but behind a hill and some power lines. By using a 30 ft. mast I get a little closer to line of sight and clear the power lines (which are far from my antenna out at the street :+>).

I don't know what's going on exactly -- too strong, multipath etc. Too bad re the tv tuners, just wondered if the vbox was ok.

[Rich A]

Looks like you've done your homework

Ten miles is pretty close. The tuner you have is supposed to be one of the better PC / USB based tuners. Let me check a few things. Sometimes the radiation pattern of the TVs is not equal in all directions. Or power levels are widely different. Before the digital transition one station I had was very hard to receive. (like you it was on the other side of a mountain). I was just barely able to get it and it was always flakey. I was running a preamp on a dedicated antenna just for that station. And with the pre-amp it was almost perfect. Only had an occassional drop out.

Then right after the change to digital, that station suddenly became totally un-viewable. Many many drops. But signal strength was "off the charts". Upon checking at the FCC web site I found their PRE-digital setup was with the digital antenna at half way up the tower and the transmitter running 10,000 watts ERP. When they went to only digital they put the digital antenna at the top of the tower (I think it might have been a 500 foot difference) AND they upped the power to one MILLION watts ERP. Ergo to say the new signal severely overloaded my preamp and the tuner's front end. After removing the preamp it then became better than ever with NO drops etc. at all. Just goes to show all the weird things going on out there.

[Rich A]

Well I spent some time looking at the FCC database for your stations.

More on that later. But first your antenna is very similar to my Winegard PR-8800 antennas that I use. They are "not" VHF antennas and are specifically designed to work from around 450 to 900 Mhz (UHF)

Now they WILL pick up lower frequency stations but it is not designed to work below around 400 mhz. Anything lower will be a "mis-match" which can cause various problems. Especially if you are using a pre-amp that is also designed specifically for UHF only. As such the pre-amp is going to actually limit front end frequencies below it's designed spec. If they didn't do that then a high power lower frequency can over-load the amp. You would have to insure that your pre-amp is a broad band one capable of amplifying from 60 Mhz all the way up to 800 or so.

The two VHF stations you are trying to get are at present very low power. And their antennas are somewhat directional. If you live to the North to North East direction of the tower, the signal is going to be very weak. Here is the data on those stations.

KNIN-DT Caldwell, ID 192-198 mhz 14 KW ERP
KTRV-DT Nampa, ID 210-216 mhz 17 KW ERP

Those two are way down below your antenna's optimum design freq. And they are pretty weak to begin with.

KTVB-DT Boise, ID 542-548 mhz 948 KW ERP
KBCI-DT Boise, ID 554-560 mhz 89 KW ERP
KAID-DT Boise, ID 512-518 mhz 725 KW ERP

As you can see the true UHF transmitting stations are putting out signals by far much stronger than the VHF stations. Even the weakest of the UHF stations is 8 or more times stronger than the VHF stations.

Add to that one other thing which is the antenna radiation pattern. Here is a plot of the KNIN station's signal.

As you can see, if you live to the North East of that station you'll be at a disadvantage relatively speaking, as opposed to someone living to it's South West.

The hill you are trying to get over is a problem that is compounding things.

If anything maybe a little more height might help? Might only need just a few more feet. It can be critical.

If I were you, I'd get another small vhf yagi and mount that just below the UHF antenna. Then run two separate coaxes from them into the house. Inside the house use a "combiner" to join both to one coaxial feed and send that to your distribution amp. (you might try loosing the pre-amp at the antenna for this)

Also here is a picture of my dual 8-bay Winegards. I have stations in two different directions and a HUGE mountain near by. I get very bad multi-path from that mountain (it's actually a 900 foot cliff face to my North). So I can't use an omni-directional antenna. So I opted to use two antennas, each pointing in different directions to get the signals. These are mounted about 3/4ths the way up on my ham radio tower. Yeah, I'm lucky my hobby has it's perks for my TV viewing pleasure. <grin>

[parisology]

Many thanks. A tower would be nice...
It's KTVB and KAID that have the most problems, and these are not the low power ones. KTVB has moved to physical 7, KAID is on 21, so it's not clearly a band problem either. The CM-4228, according to hdtvprimer.com, is supposed to have some VHF gain, more if you connect the screens so I thought it would be good enough. The preamp is VHF-UHF, and I took out the FM trap. A 2nd VHF antenna won't help PBS (21). Anyway, the tv's tuner is ok. I think it will take a lot more cut and try to fix things.

[parisology]

Ok, I could have struggled with the antenna mast, preamp and all that... but I took the easy path first and got an AverTVHD Deut oem white box for $60.

1. btv setup shows only 83% on all OTA channels. So I had to select them using the checkboxes.

2. so far no breakup in the problem channels. I will know more over the next week or so, but this is very encouraging for making good recordings.

3. I can now record 2 shows at once. What if I hook up the vbox also, can I record 2 and watch a 3rd? This is a huge upgrade for me.

[Rich A]

I have found that for the most part anything over 80 on the BTV setup can be okay BUT is on the "edge". I'd feel better if it was over 90. Having done some extensive antenna work in the VHF and UHF frequencies I can tell you that the signal strength can indeed change. Things that can affect the signal can be seasonal or weather related. In the Fall after the leaves have mostly fallen, the signal might go up a bit. (if you have a large amount of trees in the path). Plus rain, or snow will also affect it but to a lesser extent.

It all depends on when you test and the conditions. For example, let's say your signal actually varies from a low of 80 to a high of 90. So it never goes below the minimum and you get pretty much stutter free reception no matter where the signal is. BUT, what if when you tested, you were at 80 and at that time it was the highest? Then when the signal does drop a tiny bit, you'll have trouble. I'd feel better if you could get that signal up a wee bit. Or maybe that signal you are reading is the lowest it could get, in which case you'll be okay. Only time will tell.

I have one station to the South of me which changes signals during the seasons. Luckily it was strong enough to begin with so it doesn't affect playback. I have an old growth forest in my back yard with rather large trees. I notice that stations signal changes about 10 percent depending on whether the leaves are in full bloom or are on the ground. That station is at it's best a 98. So when it drops in the Summer, it never gets below around 88 to 90. Still plenty good for error free reception.