San Francisco, CA - OTA - Page 229

[quote=ProjectSHO89;19144256]The C2's VHF reception depends
Loops and loops-in-front of reflectors have been a proven design for decades; to say that only Yagis and bow-ties are "proven" ignores this history.

Your inability to receive channel 7 is most likely due to FM interference would likely be present regardless of your antenna selection.


Sutro tower ... has TV and FM stations on it. Both @ full power.
They do not cause problems with each other.

A properly installed broadband antenna aimed at Sutro Tower will bring
Channel 7 "and" the FM stations both with strong signals.
Fact.

Interesting discussion going here, I live in Foster City. I have a rooftop antenna I set-up 15 years ago for analog TV. A radio Shack model with a 80 mile range. I use the same antenna since I made the switch to a digital TV in 2006. I get KGO 7 fine! And I am aimed at Sutro as best as I can.

Though I've noticed KRON's reception has been iffy lately, the past 4 months or so. No big loss, since they stopped being NBC, but still.

I have a theory about Foster City. If you live south of the high power lines that go through the city, then it might affect TV reception.

Regarding Channel 1. I recently rescanned and the set top box and I can receive it, with Rabbit ears and with the roof top antenna. But my Pioneer plasma and Sony LCD cannot receive that channel. Same with my parents at their house that has a Sharp TV. Only the set-top box gets it. The Insignia box. So perhaps the tuners can't handle it in the TV's.

Also, my parents asked me to check out KTSF today. They had it set for 26.1. But suddenly today, it stopped being 26.1 for them and is now 27.1 and up, 27.2, 27.3, etc. Did KTSF change something? I saw the above posts suggesting to the other person to try 27.3 because it's a Sony TV? When I got back to my place, my Insignia set-top box gets 27.3 and up to 27.6! And then I tried my main set, the Pioneer Plasma and it's not been rescanned in a while. 26.1 still is 26.1 and so on.

Today I got a new Dish Network 722k installed and now KTSF is 27.1-27.4. So I rescanned my Sony TV and now KTSF is 27.3-27.6.
I wonder what my Channel Master will do??

Probably means their PSIP computer needs to be rebooted. Some tuners use the MPEG Program Number (thus the 27-3 through 27-6) while others just list the subchannels in the order it pulls them down (thus the 27-1 through 27-4).

- Trip

Thanks for the speedy responses! And verification. Let's see what happens over the next few days.

The popular advice is 4228. If you are trying to finish this weekend, the 4228, the 4221, and the 4220 are all available at Frys (8bay, 4bay, 2bay -- same basic antenna design). If you will actually be watching them (rather than flipping, which is the case in our house), I'd skip the 4220 and give the 4221 a shot, just be prepared to fuss with it, and potentially return it.

Picking up Sutro and ch.54 will be ... interesting.

good luck,
-Dave

I've got an interesting situation, and I sure was lucky when it occurred. My rotor stopped rotating. Strong winds last week were really batting the antennas around and I think it broke something up in the rotor. The box shows a changing direction but the antennas are stuck in one position. This is where I was lucky... it stopped with my VHF 10 element and UHF 4228 pointing at about 190 degrees.

How's that lucky? These are the antennas feeding my bedroom TV, my lap top, my portable TV, and one of my converter boxes, and I'm still able to get channels 2, 4, 5, 7, 9, 11, 14, 20, 26, 28, 32, 36, 38, 44, 48, 60, 65, and 66 with solid signals! When conditions are right I also get 22 and 68 off the back side of the antenna, and 42 and 54 are there off and on as well. It couldn't have stopped in a better direction!

The south bay stations are at 120 degrees, Mt. San Bruno at 176 and Sutro at 268, so I'm surprised that the antennas pointing at 190 are covering such a wide area. Apparently the 4228 is broad enough and the stations are strong enough to give me signals above the cliff edge. All are in the 20 to 30 db SNR range!

I have my other 4228 for the living room TV and that still rotates, so I still get the UHF Sacramento stations with that. My big loss is not being able to get channels 6 and 10 from Sacramento since the VHF yagi is pointed about 140 degrees off target for them.

Larry
SF

Chuck,

It's simple - the analog tuners had FM filters in them from the factory based on several decades practical experience. Many modern digital tuners, especially those designed overseas by engineers who followed the ATSC specification only, have no FM filters in them since the ATSC spec makes no mention of them. Given the high level of variability between tuner designs, there is ample opportunity for there to be tuners that work okay and for others to suffer more effects of FMI.

Since the TVfool plot forecasts a KGO signal power of -56.1 dBm (LOS obstructed by Bruno) and a zipcode level FMfool suggests a KQED signal power of -17.4 dBm, this one FM signal is almost 40 dB higher at his location. Unfortunately, the only way to measure the 2nd harmonics or IM2 products would be with a spectrum analyzer AFTER a device such as an amp or mixer to see them. Since HLSJ devices are cheap, it would make sense to try several in series. While a high-VHF antenna will have a lower gain (that is, some rejection) of FM-band signals, the difference in power levels in this example between the desired and (potentially) undesired signal powers is so great that it cannot be ignored as a contributing factor.

[quote=888CALLFCC;19146385]
Yes, it certainly will. However, it is the susceptibility of the tuners (or whatever the first active electronic device in the circuit happens to be) to the potential for harmonic and inter-modulation products that is the greater issue. Strong FM signals, especially those that are 40 dB stronger than the desired DTV signals as in this example cannot be ignored.

If you haven't read Mr Rhodes' articles mentioned above, they are recommended reading to raise awareness of this issue.

FM traps or HLSJ diplexers are a cheap and effective solution if this is a contributing factor.

This assumes the antenna is receiving 88.5 MHz exactly the same as channel 7. If you're using an old antenna that covered low VHF then it probably would. But if you're using a high VHF antenna only, which is what everyone should be using, its response to 88.5 MHz is going to be very poor, just like most UHF antennas are very poor on high VHF.

The guy in Foster City was using a UHF antenna to receive KGO which is bad enough, but a UHF antenna on KQED-FM has to be awful. That -17 dBM is probably more like -50 dBm if you looked at it on an analyzer.

Chuck

[quote=888CALLFCC;19146385]
The FM stations on Sutro Tower are not the only FM stations one has to worry about. If you look at a map of FM stations, you will find that they are all over the place. Many more locations than TV stations. I am about 40 miles from Sutro, and there are a handful of FM towers between my location an Sutro. There are also some FM stations just a few miles from my home. When I looked on a spectrum analyzer, the FM stations were 43 dB stronger than channel 7. If measured in Volts RMS, the FM stations are more than 100 times as strong as channel 7.

There has been mention about modern TVs not having an FM trap built in. There is a reason for that. Modern TVs are designed to hook up to cable as well as to work with OTA. Cable broadcasts TV channels over the entire spectrum, including the FM band. If a modern TV had an FM trap built in, it could not tune in the cable channels at those frequencies.

I don't see channel 7 passing out "fm traps" to viewers.
Channel 7 has no problem sharing the tower with FM stations.

They have reduced wattage substantially with digital tv.
That plus the combination of funky antenna models to flood the market.
There's the problem.

Can somebody take a portable battery tv ... tuned to channel 7 and
walk up to a known FM tower ? Will it work ?

If this test passes. This FM business is a non-issue.

If you haven't read Rhodes' articles, you are operating in a vacuum and are not considering any of the math involved. Some tuners may handle it, some don't. Your "test" won't do anything other than to prove whether that specific device passes or fails. Additionally, iIf any amplifier is being used, then the 2nd harmonics or IM2 byproducts would be created in it instead of the tuner's mixer. Find and talk to a station engineer who is on high-VHF and has local FM stations on a frequency that, when multiplied x2, falls into the VHF channel. KOLR is a good example since their engineer posted about his experience last summer elsewhere on this forum.

I'm out ot town this weekend for the holiday, but I did have both my spectrum analyzer and a C2 in my truck. Since the wife is sleeping in late this morning, I made some interesting spectrum analyzer screen grabs of KOLR and the FM stations out of Springfield MO using them from about 45 miles south of Springfield. I will attempt to demonstrate both high-VHF and FM reception with the C2, but it may be mid-week before I have the needed resources (USB cable) to transfer the screenshots from the SA to the laptop for posting. I'll pop them up when I get back home.

Can you provide a network analyzer plot for this HLSJ filter? Sorry, but I can't remember what HSLJ stands for or I'd look it up myself. Acronym overload.

A filter that can effectively reject 88.5 MHz and not affect channel 6 is going to be a very expensive filter, not the kind of filter that would be included in a consumer TV.

Here's a plot for the Tinlee FM bandstop filter. Tinlee products are generally pretty good but not cheap.

http://www.tinlee.com/PDF/CR7%20FM%2040.pdf

They say that channel 6 will not pass which is what I would expect. I doubt any inexpensive filter will be able to pass channel 6 and effectively reject 88.5 MHz.

Chuck

[quote=DAP;19149460]
It's certainly true that FM stations are all over the place but you're mostly concerned about those whose 2nd harmonic falls inside of channel 7 which would be those on 88 - 90 Mhz.


It's news to me that analog TVs had FM traps built in. TVs going back to at least the 1980's had tuners in them that would cover the cable channels so they must not have had FM traps built in unless they were switching them in and out for "Antenna" and "Cable."

Even if they did have them, they were ineffective at 88.5 MHz. I never could receive KVIE on 6 because it was always wiped out by FM while 3, 10, and 13 were fine.

Chuck

I wonder if I could get some expert recommendations. I'm based out of San Leandro.

I'm trying to get reception OTA. I'm really only interested in the major stations. At the moment, I'm only able to get CBS 5-1 good. FOX and NBC are choppy. I can't get ABC at all.

I'm using this simple RCA antenna my sister-in-law got for me. It literally looks the wings of an paper airplane. There is no stand for it. The two wings simply just sit on top of the top ledge of my rear projection TV.

At one point, I made my own 2 bow antenna. It worked. Never did get ABC on it. Then the antenna tipped over - I didn't actually have it on a good stand, and the wired connection broke, so I abandoned it. Nevertheless, the RCA airplane works just as good as the two DIY bow antenna. At one point, I even broke down and got a ChannelMaster 8-bow one from Frys. But it didn't really make a difference. So I returned it. ABC wasn't picking up.

The TV is downstairs. I do have a 32" flatscreen HDTV upstairs using rabbit ears, the reception is a little better. But still, I dont get ABC at all - it won't even get picked up as a channel on a auto-channel scan. The NBC channel is recognized by the channel scan, but the reception is very choppy and unusable. I believe that ABC and NBC are VHF?

Initially, I thought it might have been the rear projection TV that was giving the choppy results. But I'm leaning toward that its antenna related.

I do have a home 12 feet to my due west in direct line of sight of the towers in SF. I'm in a newer community where I'm restricted by HOA by-laws that prohibit mounting antennas on top of the roof. Prior to today, I thought that installing a bow-tie type antenna in the attic does no good. But I just saw that bow-tie setup on Larry's web page. So it is possible.

Any thoughts or recommendations are definitely appreciated.

Except for the rabbit ears, all of the antennas your tried, including your bow tie, were for UHF. Unless the signal is pretty strong, a UHF antenna will NOT pick up a VHF signal. It's too small... the elements aren't long enough. For channels 7 through 13 you need a VHF antenna. Yes, I have the 8 element bow tie 4228, and it works okay for 7 and 11, but I'm only 3/4 of a mile from Sutro Tower and 5 miles from Mt. San Bruno. One would probably work for you if you were able to get it up high enough.

There are lots of VHF antennas available, but most are too large for use indoors... that's why the rabbit ears are used. Do you have an attic space where you could put an antenna? To get channels 7 and 11 well, you need something better than rabbit ears, located as high as you can possibly get it mounted.

One thing to remember, putting an antenna indoors decreases the signal by approximate one half, so you need a good antenna with gain if you're going to use it indoors.

Tell us how much space you have available and we can make some recommendations.

Larry
SF

For results today. Move the antenna far .. far away from the tv.
Never place it on top or near the tv. Put it near any window.
It's best to purchase extra RG-6 cable so you have moving options.

The good news is San Leandro has strong signals on most stations.
post your signals from this site. www.tvfool.com

If the original owner of the C2 from Costco wishes to continue his experiment, please contact me by private message and I will send several FM Filters to insert in the system and see if that corrects the problem.

Thank you for all the responses.

With a bit of tweaking the position of my C2 antenna, I am able to get pretty good reception for ABC. So, it does seem like it was not related to FM interference (but thanks a lot for all the suggestions).

Also, after tweaking a bit more with the direction, I am able to get Channel 1 along with other local channels; how the strength of Channel 1 is low and the strength of other channel signal also drops (because now I am positioning the C2 in between the two towers).

So, I am debating if I should get a CM 4228HD and if that will improve the signal signal strength.

p.s. I was out of town for the long weekend and hence couldn't incorporate all the great suggestions earlier.

I'd still be curious to see the results with FM attenuation in circuit. Let me know if you're interested and I'll send you the needed traps/filters.


An HLSJ is a diplexer with a transition frequency between the low and high VHF bands. They make for an inexpensive low or high pass filter depending on which set of ports you use vs the capped port. Obviously, they cannot be used as a high pass filter if you have low-VHF signals than need protection.

Here's what the Holland HLSJ looks like. I also tested the Pico Macom HLSJ, but I haven't finished the comparison graphs. For FM filtering, I like the Pico Macom device a bit better.

Homeowner associations can't prohibit outdoor antennas.

http://www.fcc.gov/mb/facts/otard.html

"The rule (47 C.F.R. Section 1.4000) has been in effect since October 1996, and it prohibits restrictions that impair the installation, maintenance or use of antennas used to receive video programming."
"The rule does not prohibit legitimate safety restrictions or restrictions designed to preserve designated or eligible historic or prehistoric properties, provided the restriction is no more burdensome than necessary to accomplish the safety or preservation purpose"

Hello,
So this "Bus Tour" your company is hosting in California to give away
product.
......Can we expect the C5 model .. to be part of it ?

No. C1 and C2-CJM models (overstocks and/or refurbished) are units given away on the bus tour.

I am located in Fremont (94555) and have C2. I am in similar situation. With lot of tweaking I got ABC at 290 degrees but it keeps skipping every 10 seconds. And due to the change in direction (earlier it was at 280 degrees) many other channels have started skipping like CBS, PBS, NBC and so on. (by skipping i mean it pixalates and looses audio for a second or two).

Should I consider changing the antenna? I called up AntennaDirect and they suggested an inline amplifier with 10db gain, but I have a HTPC setup and the tv tuner card cannot power the amplifier (ATI Wonder 650). I also tried amplifier with has power adapter. Result is still same, it skips. Is there anything I can do to remove this skipping.

Another weird problem I noticed on channel 5.1: When there is HD reception it skips once in a while but when non HD (4:3) advertisement start it pixelates like crazy and freezes, the reception resumes if the ad is in HD.

My setup: Antenna is about 17 feet high, 35 feet away from TV, 50 feet cable (excessive cable rolled near the TV), connected to ATI Wonder TV Card and using Windows 7 Media center.

For the past week or so I've been seeing a strange blocking and studdering of KTNC's (42.x, RF14) transmissions (I actually watch some of the ThisTV stuff on 42.3). It's not the kind of behavior I would see from a station on the "cliff" (i.e., conventional pixelization and signal dropouts). Indeed my Sony reports a signal level from 93 to 98 (the max my Sony ever reports) with a SNR greater than 32, and an AGC of 26 to 27. Of course the signal variance is due to some multi-path but signal level is way above the threshold for my TV which would be below about 32.

On the other hand, the Sony is reporting a error value at the times of the blocking/studdering. So the strange blocking/studdering is just the way my Sony behaves during its attempts at error correction.

In the year+ since I set up my antenna(s) I've never seen such behavior, and I only started seeing it on ThisTV this past week.

So the purpose of this post is simply to ask for confirmation if anyone else is seeing this kind of behavior on RF14? If so then the problem is most likely at KTNC's end. Maybe something is wrong with their transmitter signal quality? I'm just trying to rule this out.

On the other hand this could very well be due to my antenna setup, and/or the fact that my antennas are in my attic, and/or the trees the antennas look through (I'm guessing that the trees are in their max foliage at this time of the year). I also saw the same behavior on my neighbor's TV. But that is not strictly a confirmation since his setup is similar to mine since I made his antenna too Considering we're talking about RF14, i.e., the bottom end of the UHF TV band, I'm not ruling out that with the dimensions I used for my 4-bay antennas they might have reduced gain there. I don't believe it based on previous signal level measurements I've made on my antennas over this past year, but I won't rule it out either.

Hi,

With the weather changing from day quite widely, I would suggest that weather is the cause.

The inversion layer is moving up and down I suspect. The fog is coming and going and so on. A cold front just went by.

As KTNC's location on Mt. Diablo is away from the other transmitters, it may be affected differently.

Larry will tell you that the transmitted signal is very closely monitored and does not vary.

I am receiving KTNC at about 90 degrees away from where my CM4228HD is pointing so it must be a weak signal for me. I do have LOS to Mt. Diablo (No more, the trees have grown so high now but I could see it ~ 35 years ago).

I am capturing some movies from KTNC, the one I watched the other day was fine, I did not expect it to be. I have another one and I will report how it is.

SHF

I used to live in Fremont 94555 (in Ardenwood). Signals from Sutro and San Bruno were killer there. I could see both locations standing on my roof. Get yourself a Winegard high VHF/UHF antenna, put it on your roof, and you shouldn't have any more problems.

Chuck

Hi Chuck,

Thanks for your reply. Is Winegard HD 7694P a good option? I have already spent 100 bucks on C2, I want to make sure this time I get the correct antenna.

Is Winegard HD 7694P a directional antenna? Will I need a rotar for this antenna?

Me!,

I checked KTNC on a set where their signal is always at the digital cliff. It was still there, so I doubt it's a problem from them.