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Discussion Starter · #1 ·
I just set up a DTC-100 for OTA and it is wonderful.


I have an old antenna that has not been in use for many years. It was very good, with a rotor and on-mast preamp. I have rewired it and it is now getting high 60's and 70's on the strength meter. The antenna is pointed toward Sutro tower. I live in Palo Alto about .7 mile from the 101 freeway.


KQED-DT (PBS): 70's, comes in fine.

KGO-DT (ABC): 20's, poor.

KPIX-DT (CBS): 70's, no picture at all, does not even see the identification information.

KRON-DT (NBC): I thought this was on 57 according to my guides. I get absolutely nothing at all, not even a strength reading.


Also get 12, 19 and 36 OK.



Any advice would be appreciated.



Bob Smith

 

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Wm Phelps lives within blocks of you there in Palo Alto, you might give him a call to compare notes. You probably need to replace the antenna, wear and tear and corrosion might have taken it's toll. I lived in Los Altos, and had a Radio Shack UHF antenna and preamp about 30' up on the roof, and did well with all channels on the air about a year and a half ago. You might give us data on how well the analog UHF stations come in at your location on the antenna, that is sometimes a good indication of multipath and signal strength. Do you get a lot of ghosts on channel 20? That sometimes is a clue.


Bob Smith (the other one!)
 

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Discussion Starter · #3 ·
Those are good ideas.


Channel 20 (analog UHF WB) comes in OK. I know it is on the tower as well.


I am puzzled by the fact that KRON-DT 29 is giving a signal strength of 70 but not picking up. Also puzzled by why I get nothing at all on KRON-DT 57.
 

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I may be even closer to you than Wm! Near Cubberly. I'm receiving all of the digitals just fine with a DTC100 and nothing more than the ChannelMaster Stealth antenna sitting on a 3' mast.


You're welcome to bring your receiver over to see if the issue may not be your antenna - though I suspect that is the problem. I can't imagine living w/o CBS HD.


BTW, is it my imagination or do about 1/5th of the posters on this particular forum live within 5 miles of PA?


Curtis
 

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Rlsmith,


Did you do a channel scan on the DTC-100. Also disable On Air guides and do a new scan. What is your longitude/latitude? Can you tell us anything more about the type of antenna you are using an about the preamp? Should be duck soup at your location. Field strength should be very large in PA and KPIX and KRON are the two of the most powerful DT stations on Sutro., just wondering if there is any chance you may be overloading the DTC-100 on those channels. All speculation, though, don't know enough yet.
 

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Discussion Starter · #6 ·
I will try disabling guides and doing a channel scan over again.


The signal strength of KPIX-DT is 70-75 but still no picture! Other channels are similar BUT KGO-DT 24 is 20-25 and KRON-DT 57 does not even show up! KQED-DT for example is 70-75 and comes in just fine.


The antenna is a top-of-the line Channel Master from about 18 years ago. There is a rotor (which is not working) and an on-mast Galaxy preamp (which appears to be working). The antenna was on a 30 foot mast but I have reduced that to 10 feet, believing that was overkill. I have been changing the connectors etc. without much success. I believe it is pointed toward Sutro and certainly I am getting the highest readings from this location. I am about to try replacing stuff.


I am finding it hard to believe that this is a multipathing issue. I am wondering if it could be the DTC-100 (Proscan version) but that does not make a lot of sense: why would it work on some channels and not others?


I thought this was a no-brainer in this location.

 

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I'm having a similar problem with my Toshiba DST-3000 in Foster City. Although, from the looks of it, I may be getting better reception with my Radio Shack amplified (strip antenna - discontinued) KPIX (CBS) is coming in at 90-100%. I get KRON and Bay TV on Channel 57-2, 4-1, 4-2 (When they aren't dark) but absolutely NO NBC! I honestly wish that KRON didn't have ANY local programing - just give me the damn studio! I can't stand watching people sit around a couch 24 hours/day!!


I'm fairly certain that I can receive NBC since my old Panasonic STB picked it up, but not the newer DST3000, which is supposed to have better reception. In fact, it picks up way more DTV broadcasts over the old Panasonic, but no NBC.

FYI - when I checked this morning, KRON moved from 4-1 to 57-1! Two hours later, it shifted back to 4-1 with Bay TV on 4-2 and 57-2.


Good luck and I hope you figure out how to get yours working...


Elbert
 

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rlsmith,


I can see the entire Bay area topologically. And you don't have a multipath issue. Again, give me a long/lat or local adress and I'll tell you exactly what's in front of you.

You have an old undocumented hook up that is causing a lot of confusion to you and to those of us who would like to help you. I can tell you exactly what you need to do to get reception but I can't trouble shoot an unknown problem. I am puzzled, for example, on how you manage to see KICU, KNTV and Sutro, all at the same time, with no rotor. You say you are pointing at Sutro. KICU is at mount Madonna above Fremont, KNTV is at Loma Prieta. So, although I know a great deal about antennas, I am confused still about your set up. Often when you have an undocumented set up that doesn't work well, it's best to trash it and start over. All for now.


Regards,


John Stephens
 

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Discussion Starter · #9 ·
Everyone:


I took the antenna down and rewired it completely. It is working fine now.


The thing that was confusing me was that I was seeing a 70 signal strength for 29 (CBS!) but no reception. I cannot account for this. I am seeing 80's now, pointed to the Sutro tower, and am getting about what I expected.


John Stephens:


Thanks for your offer of assistance!


The antenna, while old, was not undocumented, just a chore to take apart. (It has a 30 foot mast, so I have been on the roof with a ladder etc.)


I was confused, as I said above, by getting a 70 signal strength from KPIX-DT without any reception. So I thought it worthwhile to see if there were any "gotchas" that folks around here might know about that I was not aware of before I went off on a tangent.



Thanks again!



Bob Smith

 

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Bob,


Congrats on getting your signal strength up to snuff.


I can't explain why you are getting such an indication and still not receiving a signal. I think the way the signal strength meter works is by counting corrected errors on the FEC decoder. The way they do that is by re-encoding the decoded data with FEC and comparing that to a delayed version of what is received before error correction. That is why you can't normally get a meter indication until the bit sync in the receiver is locked. With that high an indication, you must assume the receiver is locked, and I can't understand why with the FEC decoder working so well, a picture isn't displayed.


The meter doesn't have any relationship to input power, only SNR, indirectly indicated by error rate.


One thing you have to be careful about is the fact that even if your average SNR may be OK across the band, any deep notches caused by multipath that place the missing spectrum close to the noise floor of the receiver will cause errors. Also, if the notches are beyond the dynamic range of the DSP, errors will result. It is possible that the transversal filter taps are close to maxed out on gain, and that even though the error correction is able to pull a reasonable BER through, the uneven distribution of errors caused by the equalizer may be causing the MPEG decoder to not have enough information to display a picture.


All academic at this point though, you've fixed your protlem!


Bob
 

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Rlsmith,


Congrats! Good to see these mysteries removed. Would be nice to have a detailed post mortem. Any idea what might have caused your problem?


Regards,


John Stephens
 

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I'm another user in the Palo Alto area, this time over on Stanford's campus. I have a bit of a problem in that I have two 4 story buildings directly in my line of sight to Mt. Sutro. They are only about 200 meters away from my one story apartment row. Realistically, I can only put up an antenna on a 10 ft mast, and I'm actually going through the FCC resolution process now since Stanford wants me to take the antenna down for "aesthetic reaons". Hehe, that's another story, but I think I'm solid ground to win it.


Anyhow, here's the setup and the problems. I'm using a Radio Shack 100' Yagi antenna, I get CBS, ABC, and KQED (29, 24, and 30) in the 40's or so on my DTC100, I get in the 20's or nothing for the other digital channels. Do you think one of the channel master antennae with a preamp could inprove the situation? Here's my lat/long info, as a previous poster mentioned they could be useful


Decimal Degrees Deg:Min:Sec

Lat: 37.424411 37:25:27.880N

Lon: -122.152814 122:09:10.130W


Any help or advice will be appreciated.


thanks

Tim
 

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Discussion Starter · #13 ·
I don't have much experience with digital antennas but I had a lot with analog at various places.


Based on that, I would definitely suggest an on-mast preamp. Radio Shack has some that are cost-effective. Get the more powerful model.


The CEA AntennaWeb Selector site has good information about where the channels are in relation to your house. Obviously, most are on Sutro. You may find that a rotor helps. (I have a rotor left over from analog days but it is presently not working.)


Good luck!



Bob Smith

 

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thollida


Your problem is quite easy to solve. A couple of preliminaries first. First, other than those 4 story buildings, there is absolutely nothing blocking you from a line of sight to Sutro. Second, the fact that you get measurable signals at all on 24, 29 and 30, means that you have at least 16 dB S/N at the STB. Good. All the DT channels at Sutro deliver very large and comparable FS to your area. Means that you ought to also be able to get 45, 56 and 57. As you are currently set up, you are degrading your S/N by 10 dB plus the DB loss in your cable, You can make most of that go away by using a low noise high gain preamp mounted close to you antenna. Therefore, just buy a CM7775 UHF preamp(Gain=26 DB, NF=2 DB). So with everything else just as you have it now, you'll get 10 dB or more better S/N and get robust reception on those Sutro stations, despite the hefty attenuation due to those bldgs across the way. Let us know your results.

BTW, I am a good barometer of what those stations are transmitting. I live on Mount Hamilton about 50 miles away. From my back porch, on a clear day, I can see the tower quite clearly. There's absolutely nothing in my view. I have no multi path, my antenna is screened from the rear. Have enough gain to drive 3 STB's with no pre amp. AS I write, I am getting mid 90's on all those stations but KTVU. Getting 10 dB less on KTVU(2/56). All for now.


Regards,


John Stephens
 

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Quote:
Originally posted by john stephens:
thollida ... there is absolutely nothing blocking you from a line of sight to Sutro. ...
Unless you count those huge hills around hwy 280 where the large dish is installed. Last year I lived on the southern edge of the Stanford campus and had a difficult time getting even what Tim is now receiving. There were no structures, trees, anything else in me way but those large hills.


Pls correct me if I'm wrong, but you're at or higher than Sutro tower, right? Most of PA is flat valley. Though now on the southern end of PA I get great reception.


Curtis

 

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Curtis,


Trust me, those huge hills are not in tollida's line of sight. There do exist folks in the bay area for whom those hills do matter. Not tollida, not me not most folks.


Regards,


John Stephens
 

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Discussion Starter · #17 ·
Dagman:


I am also in Palo Alto, on Greer between Embarcadero and Oregon, and am having problems.


I get 29 and 30 but cannot get KRON or KGO well enough to watch a show.


I bought a CM 4248, a new rotor, new wiring, and am waiting for a CM 7775 preamp. My only other option is to move the antenna.


The antenna is pointing straight toward Sutro and I have followed John Stephen's advice so far.


[No wonder HDTV is not popular yet. If my mostly-high-tech friends had to do through this, they would give up.]


Where are you located?


 

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Quote:
Originally posted by rlsmith:
Where are you located?
I am at Lytton & Middlefield just North of downtown Palo Alto.


The first things I am going to try are:

1)Raising the antenna . . . I can get another few feet from my current arrangement.

2) Steadying the antenna . . . right now it is 13' up but supported only by a strap mount to my chimmney. I think it sways a bit. I am going to add guy wires just below the rotator.

3) Fine tuning with the rotator. I haven't yet tried to align the antenna/rotor with the true compass directions. I've just been spinning it around to whatever looks good on the analog stations.


BTW, should I be using magnetic or True directions? Is Polaris magnetic or true North?


Antenna tip: I find Polaris (the North Star) is the easiest way to align the antenna since it is the only reference I can use when looking up at the antenna while rotating it. You all know how to find Polaris right? It is lined up with two stars that form the non-handle end of the "Big Dipper" (AKA Ursa Major).
 

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Discussion Starter · #19 ·
I am between Embarcadero and Oregon on Greer.


I just received the CM 7775 and installed it. Initial tests seem better. I can now sort of get 57 (NBC) and 24 (ABC). I need to test with the rotor tonight to see if things are really OK or not. I suspect not.


The next thing I will try is to move the entire antenna assembly. I think that I have a position that will point to Sutro without the trees that are in the distance. But this will be a big job.


I don't mind this personally (it's actually a bit fun I suppose) but I am scared that this is going to make HDTV very hard to get going, unless cable starts to carry it.

 

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Quote:
Originally posted by rlsmith:
I am between Embarcadero and Oregon on Greer.

I just received the CM 7775 and installed it. Initial tests seem better. I can now sort of get 57 (NBC) and 24 (ABC). I need to test with the rotor tonight to see if things are really OK or not. I suspect not.
Let me know how it goes, I want to find out what works.

Quote:
Originally posted by rlsmith:
I don't mind this personally (it's actually a bit fun I suppose) but I am scared that this is going to make HDTV very hard to get going, unless cable starts to carry it.
It has been fun so far, but it is going to get annoying . . . I would certainly be annoyed if I had to move the antenna placement. That's is a big job.


But I wonder if KRON is doing something wrong. Why do we both pick up other stations that are on the same tower? I even pick up 36's digital channel and their UHF counter-part is really snowy. (DTV could be a godsend to UHF stations if they broadcast as well as 36 does . . . the analog channel is snowy but the digital channel is better than analog cable quality.)


I am also having trouble with KTVU-Fox's digital channel . . . do you get them OK?
 
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