Need help with antenna selection--San Francisco

westcoastman · 29-Jun-2011, 1:30 AM

Here is the tvfool report for my specific address in SF:

http://www.tvfool.com/?option=com_wr...03d93d87a07aee

I have finally cut the cable to DirecTV and am amazed at the quality of the stations I am now getting with a simple indoor antenna. My problem is I cannot receive NBC at all. Unfortunately, it's not on Sutro Tower, but on San Bruno, which is about 5 miles from me. I know there are terrain issues, but I'm hoping there might be antennas that could pull in the signal. I tried using a friend's Antennas Direct DB4 on my roof, with no luck. Does anyone have a recommendation for another roof antenna to try that likely would be able to pick up NBC? I'd be willing to install a rotator with a roof antenna if it would improve my chances of recieving NBC.
Thanks in advance!

GroundUrMast · 29-Jun-2011, 1:48 AM

Wow your are close to the Sutro Tower! At those power levels, a paper clip is more than enough antenna. No amplified antenna would have a chance with those power levels. (The power levels are so high that I would expect any and all amplifiers to overload, causing great difficulty with distorted, unusable signals.)

An Antennacraft Y5713 pointed south will receive KNTV - real channel 12, and KGO - real channel 7.

An Antennas Direct DB-2 on the roof, facing Sutro tower will get all of the UHF stations WSW of you. You may need 20 to 40 dB of attenuation due to the extreme power levels.

To combine the signals from the two antennas, you will need a UVSJ. You should have no trouble driving at least four sets with no amplifiers of any kind, just a passive splitter with the same number of ports as number of connected sets.

John Candle · 29-Jun-2011, 4:32 AM

NO AMPLIFIED ANTENNAS , DO NOT use any type or kind of amplified antennas. The signals are so strong that the first 9 are listed in red , over the top strong. You can try one of these NON Amplified indoor antennas if the house is not wrapped with stucko and stucko Wire or is not wrapped with metal siding. http://forum.tvfool.com/showthread.php?t=233 . Here is how to aim indoor and outdoor Tv antenna , http://www.kyes.com/antenna/pointing/pointing.html , aim the indoor antenna at about 165 degree magnetic compass. Read and understand this about , REAL Digital Broadcast Tv Channels , Virtual Digital Broadcast Tv Channels , Analog Broadcast Tv Channels , http://forum.tvfool.com/showthread.php?t=695

westcoastman · 29-Jun-2011, 5:55 PM

Thanks for the specific recommendations. I'm wondering if there is one antenna that will serve both transmitters (Sutro & San Bruno) if I install a rotator on the mast. Would prefer not to have two antennas on my roof. I note that NBC (on San Bruno) is identified as VHF while all the stations on Sutro are UHF. Not sure if that factors into the antenna I buy.

ADTech · 29-Jun-2011, 6:55 PM

There's a reason I sometimes refer to the area between and adjacent to Sutro and San Bruno as "Multi-path Hell" or "The Valley of Death".

KGO on Sutro is also on VHF (7). KNTV, operating on VHF-12, is behind Diamond Heights for you and its signal will be strongly affected, more so than the TVfool plot would suggest due to the short ranges to the diffracting terrain. At the same time, there's an FM station on Sutro whose 2nd harmonic falls right into VHF-12 raising a strong probability of FM inter-modulation (interference). An FM filter is strongly recommended.

Stations coming off Sutro will be substantially less powerful that TVFool suggests due to your significant angle of depression relative to the transmit antenna's primary horizontal signal lobe, probably in the order of up to 20 dB lower. The majority of their power is being pushed just below the horizontal plane with relatively modest amounts directed towards the base of the mountains that the antennas are situated on.

Your situation is one where I'd be curious if our ClearStream 5 would work. I'm curious enough that I'd be willing to send you one to try out. If you're interested, send me a Private Message (PM) with contact information and I'll set it up.

GroundUrMast · 29-Jun-2011, 6:57 PM

Once again... I'm impressed

westcoastman · 4-Jul-2011, 12:01 AM

As a follow-up to the C5 suggestion, I obtained one and spent 2 hours positioning it with the help of a friend on my roof and it was an absolute failure at picking up NBC on San Bruno Mountain; absolutely 0 reception. So moving on to next suggestion.

No static at all · 4-Jul-2011, 4:46 AM

Did you use an FM trap as suggested?

ADTech · 5-Jul-2011, 2:36 PM

I was just going to ask that same question.

On FM, the C5 should exhibit an omni-like horizontal pattern with a net gain of around -10 to -15 dbi. Still, the power differential from Sutro's FM stations is still going to be somewhere around 20 dB greater than KNTV's signal if the TVFool simulation's math is even close and depending on the actual signal power delivered at your angle of depression from the towers of interest.

westcoastman · 5-Jul-2011, 5:31 PM

Yes, I used the FM trap with the C5 and the number of stations I received actually dropped by about 25%. Most every other station's signal strength dropped to 60-70%. So removed the trap and was back to strong signals, still minus NBC.

ADTech · 5-Jul-2011, 7:16 PM

That's odd. An FM filter should have zero negative effect on anything (except FM). I'd suspect the filter was defective.