San Francisco, CA - OTA - Page 255

WOW! Now that is a fantastic TV antenna farm! Congratulations, Chuck.

I wonder what you'll get for distant stations this summer during good Tropo times. Think you might see Santa Barbara to the south?
How often do you see the stations from Chico?
Ever see channel 7 from Redding?

Inquiring minds will be waiting to see what happens.

Larry

I read through the entire thread on the 91XG at Digitalhome.ca:

http://www.digitalhome.ca/forum/show...111398&page=16

Seems like people have done just about every mod possible to it. There are a number of comments about increasing the gain by making the reflector larger by a foot which works best for the lower channels. Nobody has looked seriously at F/B because people are concerned about gain, not F/B. In a comment from the Antennas Direct engineer about making the reflector larger, he said increased F/B would be the most likely result, although he hadn't run any tests. Good news for me. I need to track down some coarse screen. I think I'm going to be in Sonora tomorrow where there's an OSH.

Chuck

It's an experiment. I may only keep 2 up. It didn't improve the SNRs for Sacramento and it didn't help Sutro weak signals enough. My noise margins are running 20 - 38 dB for Sacramento so if I can trade a few dB of gain for much better F/B ratio I'll do it.

I think Santa Barbara is impossible here even with my great shot in that direction. KEYT would be the most likely candidate but it is on channel 27, same as the very strong KEXT analog.

I have seen KRCR Redding here but I don't look for it very often. It's ducting only. I've also seen KAIL Fresno on 7 but again only with ducting.

KCOY is another possibility but it is on 19, same as KMBY, and right next to the overpoweringly strong KUVS. I used to see KCOY from time to time when it was on analog 12 but it was always weak.

I thought my best chance might be KSBY on 15 which is a 1 MW station due south of here. So far no luck but it has to compete with KBSV on 15. I do get some good ducting down that way as some ham repeaters come in here from the same location.

I may decide to scale back UHF and improve VHF to get KGO more often. They're about 50% now and just below the cliff when they're not in. I'd like to get one good news station from SF. Too bad we can't get KGO to put their 72 KW transmitter on the high antenna.

Chuck

Turned on the TV today and KRON is broadcasting their HD signal on 4-1 now instead of 4-2, and the SD is now broadcast on 4-2 instead of 4-1. Also, the aspect ratio's on 4-1 HD were alll over the board, at least for the better part of the day. Are they switching things around? My Zenith converter boxes display the new channel info for 4-1 now as "KRON-HD," but my Panasonic and Sanwin TV's (San-what?) display the info as "KRON-SD" even though the actual image is HD. Why would some TV's say "KRON-HD" while my others display KRON-SD? Don't they get that information from the broadcast signal?

KRON made the switch putting HD on 4-1 about five weeks ago. There's talk that they're going to be carrying a new program service, The Country Network, on 4-2 in the near future. See my post of 4-23-11 for that news and other news of changes on the various local channels.

The set that shows KRON-HD on 4-1 is the updated PSIP info that KRON is sending out. Apparently your other sets don't automatically update and you have to do a scan for the PSIP info to change. Tuners all behave differently depending on what the manufacturer decided to implement in their software.

Larry
SF

Hi I was wondering the new FRY'S ad is showing a new channel master converter box that says in addition to Antenna signals it also gets unencrypted clear qam cable signals? what does this mean? Are there other kinds of stations out there you can get over the air with an antenna or is this a totally different thing?

qam are channels that are decrypted (unscrambled) when you insert a wire from cable company strait into your television input. most are over the air sometimes you get open premium channel.

A bit more, um, "clearly": QAM is the modulation technique used by U.S. cable companies instead of the 8VSB technique used by U.S. broadcasters. (Wikipedia will tell you what the acronyms stand for if you care) So "QAM channels" just means digital cable TV channels. "Clear QAM channels" refers to the subset of the digital cable channels that are not encrypted. As nycdigital09 said, they are mainly the channels that came from the local broadcasters. Here in the Bay Area that's all they are, except when Comcast is doing a limited-time free preview of certain premium channels.

I ran a test yesterday before the thunderstorms hit to see if I could increase the front-to-back ratio of the 91XGs. I added a larger reflector screen on two of the antennas, making them about 2' wider. I reconfigured the setup for two antennas and the other two were unused. All the comments over on the digitalhome.ca 91XG thread indicated this should help. It made not 1 dB improvement on any channel. I put them back in the 4 antenna configuration. At this point I'm out of ideas.

Chuck

did you try the 1/2 inch mesh behind the reflector, you should see to more forward directionality

Yes, I used 1/2" mess. I didn't look specifically at gain but nothing stood out. There was no obvious improvement in the weakest stations. I might not have noticed <1 dB.

Today I experimented with an old CM UHF corner reflector on the ground. There was nothing I could do with the screen to improve the F/B. The exact position of the 300:75 ohm balun made up to a 6 dB change. That was disturbing. Makes me want to play around with a 91XG on the ground to see if the feed line position makes any difference.

Chuck

FYI... KNTV 11.2, NBC's new news and information service, is now in HD.

Larry
SF

Update: As Trip pointed out below it's 16:9 SD on 11.2, not HD.

I use to have a radio shack u120, which was the highest yagi uhf gain wise antenna they sold, it was 102 inches in length, with 15 directors, with 2 half wave driven element, the corner reflector was made of 14 rods. that yagi antenna was a pretty decent setup. I think if anything changes you can make, have you tried the extra middle section, i read that makes 91xg more directional.

Not HD, widescreen SD.

- Trip

Gosh, KNTV's signal travels far.

SHF

My experiments with the 91XG at ground level and a sheet of metal siding revealed that the 91XG receives ground reflected signals from the underside of the antenna boom. Holding the metal panel parallel to the boom between the boom and the ground blocks the ground signals, and, in the case of KCRA, reduces signal enough to cut off KCRA reception despite a clear front directional path. Yagi antenna elevation patterns have a node perpendicular to the boom. Moving the balun around near the ground will interfere with ground reflected signals and probably causes your 6 dB change.

I also have dropout problems with KPIX (live in Sunnyvale, using Winegard 7694P on roof mast) that is fairly severe. I have not been able to figure out a pattern regarding when it is particularly bad and unwatchable. KQED has also been slightly unreliable during late afternoons, so I started instead tuning to the San Jose PBS equivalent station KTEH which seems a little better but still occasional pixelation and audio drops. Since KGO is from the same tower and I tune that in just fine, I had assumed there was some local interference for that particular frequency that was causing the problems, or perhaps KPIX was transmitting with less power. I'm taking a little comfort hearing that others see the same issues with this particular channel.

Hi,

A few months ago during the rain When I had problems with KPIX I discovered that my Terk HDTVa on top of a bookcase got KPIX solid pointing due West out to sea. When my CM4228 near Murphy's house got KPIX back the Terk has not gotten anything like the solid signal from KPIX again.

A couple of months ago KTVU starting having problems during NASCAR round and round. Go figure. Oh well, NASCAR on Fox is done now.

You do realize that the RF channels you talk about are quite far apart and that KTEH is in a totally different direction.

SHF

Hmmm, I guess it's probably well known here, but I'll post it anyway:

OTA HD

The sporadic E season is here and I thought I'd have a chance at a channel 2 DTV station. Tonight 50 MHz was hopping so I took a look. I could see a digital signal on the spectrum analyzer but I could not decode it. Unfortunately there are still analog stations on the air which are much stronger. I ended up DXing XEPM from Ciudad Juarez, Mexico. I attached an image of their weather forecast. They never put their call sign on the screen even at the top of the hour. I had to look up in the FCC database to see if there was an analog from there and there was. It's 9.5 KW. The amount of multipath on the picture makes me think that decoding a digital signal like this will be hard.

Chuck

No surprise from a poll conducted by the CEA. The CNET poll had 61% for "Leave OTA Alone" when I voted.

Chuck

It's all about who can make the most money, not anything about service to consumers.

Good to see you on here again, Grubavs!

Larry
SF

Nice DX from Juarez, Chuck! Maybe we'll have some fun this summer.

Larry
SF

All I see here is "Analog" on 2, 3, 4, & 6 No Digital.
2 locked on ... "for about a second". I don't know what it is.
2 & 3 Flutter with the antenna pointed to the Fresno Valley.
4 Flutters with the antenna pointed towards Lake Tahoe. ??

And I see analog on "23" ... not a good thing.
Digital on 23 is stronger but spotty.

Well that image looks like KNTV did .... from Mt. Loma Prieta ... (That's not Maggi Scura)
I did get the digital on 12 back then too. Even with 4 ghosts to the Left of image, & 3 ghosts to the right of image.
Multipath on VHF here was not a issue. Not a big one anyways.

With my new antenna setup I was able to measure loss in the cable from inside the house to the base of the tower, about 15' of RG-6 and 450' of Trilogy MC2 1/2" hardline. This wasn't practical before since the cable ran to the top of the 50' guyed tower. It's pretty hard to get a power meter using 120 V to the top of a tower. Now I'm using RG-6 from under the house to the TV and RG-11 from the base of the tower to the VHF/UHF diplexer on the mast at 65'.

I had calculated how much loss there should be if everything was perfect. Of course I expected more because it's never perfect. But I measured 4 dB more loss than I expected at 700 MHz. This seemed high.

I was using several pieces of RG-6 to get into the house. Under the house to a wall plate with a barrel connector, jumpered to the preamp power inserter, and two more short pieces of RG-6 jumpered so I could connect the spectrum analyzer to the antenna.

I measured most of these pieces and some of them were awful. One 3' piece of RG-6 had 1.3 dB of loss. A barrel connector had 0.4 dB of loss. Yet one 6' RG-6 section was perfect with 0.3 dB loss. The Tin Lee power inserter had no measurable loss.

I got rid of all the crummy jumpers. Now the hardline under the house has a single piece of RG-6 running from there to the power inserter and the good RG-6 jumper runs from the power inserter to the DVR.

I was able to reduce the loss by at least 2 dB. I had to splice the hard line in 2 places and put my own makeshift F connectors on the ends so I'm sure there is loss there but I can't buy real connectors for the hardline so that's the best I can do. There was no rhyme or reason as to what components had how much loss. The expensive compression F connectors were not lower loss than the cheap crimp types.

The bottom line is don't use any more cable jumpers, barrel connectors, or splitters than absolutely necessary as the can add much more loss than expected.

Chuck

Hey Larry. I check in frequently, but (knock on wood!) my antennas just keep on delivering (thanks to you and others on this thread!) so I don't have much to talk about.

Saw a commercial for this on KAXT My Family 1.6 last night thought it might be of interest to some of you.

http://www.freetvandbroadband.org/

66.1 was over 30% higher on the signal meter indoors here after midnight. I didn't try to get a lock on it and watched Victor Borge on KQED instead.

I work at Harmonic and did not realize that KAXT used our products. Thanks for pointing it out.