Help Needed: Outdoor TV Antenna Connection

[kb0nes]

Neat antenna that the station provided, cool piece of history too.

It appears that the folded dipole section is about 22" long which works out to being resonant at about 207 Mhz. The rod parallel to the dipole is parasitic reflector to give the antenna a few db of directivity with the front being the dipole.

Remember that all this is 300ohm so you could connect a 300-75 ohm balun at across that dipole to run coax to the set. It is a pity that your UHF corner reflector doesn't also have a folded dipole so that it's feed point would also be 300 ohms. You could actually form a folded dipole for that corner reflector to replace the stock open dipole.

Here is a handy webpage with a folded dipole dimension calculator if you want to experiment.

http://www.changpuak.ch/electronics/Dipole_folded.php

 

[rp2813]

Thanks Phil -- your information above reveals that I have the KNTV antenna aimed backwards.  I'll turn it around and see what happens.  Just for the record, KGO has been on for the past three hours and there hasn't been a single issue.  I would think that turning the KNTV antenna around could only improve on the progress I've made.

 

I'll look into making a folded dipole for the UHF remnant.  I'm not sure where I'd find aluminum tubing, or whether using a tube bender would work to "fold" one.

 

[rp2813]

I turned the KNTV antenna around so everything is now properly aimed.  I'm receiving all available channels with absolutely ZERO interference!   It seems odd not to be dealing with hiccups and temporary loss of sound.  

 

A scan performed by the digital tuner box picked up one additional channel that broadcasts on VHF from about 20 miles south of here, so am assuming the VHF antenna gets credit for that one.  It offers nine appearances, each of which are religious in nature, so I manually deleted all of them.  This is why my excursions to Reno are few and far between.

 

The real test comes this weekend when some rain is expected.  I don't think I can do any better with what I have, so if the rain and/or related cloud deck cause trouble, that will suggest the need to upgrade.

 

[sudsmaster]

A while back Costco had some digital TV antennas on sale. They have a grid not unlike the Channel Master 4221 pictured above, but probably a lot smaller.

I have one mounted on one chimney here, and it's mixed in with a standard UHF/VHF christmas tree style antenna on the other chimney. They are joined with a coax switch box. I usually don't see much difference if one, or the other, or both are mixed in. There's also a signal booster after the switch box because I run coax from the antennae to every room in the house.

The digital reception here is generally great - high def on nearly all channels.
Some times I rotate the old antenna this way or that to try to capture North Bay signals, but in general that is not successful. Occasionally the TV tuner scanner will pick up analog/digital signals around Channel 1, but these are generally without content. I wonder if it's from a nearby hospital or something.

It would probably be fun to put a rotation motor on the older tree antenna, to see just what I can pick up with it.

When I get a Round-To-It...

 

[rp2813]

Rich, I checked around on line for a list of OTA channels to see if I was pulling in everything within reason, and found the rundown in the link provided.   It appears north bay channels primarily offer duplicate programming of what's provided on stations in closer proximity that I can easily receive.

 

The only station I'd like to receive but has its transmitter to the south of here is KSBW 8 out of Salinas/Monterey.  They cover the Santa Cruz weather forecast in more detail than SF Bay Area stations do, and have a no-nonsense/no hype meteorologist who is also a licensed pilot and puts a practical spin on things.

http://www.choisser.com/sfonair.html

 

[sudsmaster]

Most of the stations I receive appear to be broadcast from Sutro Tower in SF, or from Mt. San Bruno just to the south of there. I also can get KCSM which is the College of San Mateo. KNTV I think has a repeater up in the SF area - they probably had to do that after they took over the NBC license (KRON was forced out of NBC because of its ownership of the SF Chronicle). Apparently there's a law that TV stations cannot own newspapers in the same local market, and vice verse.

Also since digital signals don't travel as far as VHF analog, if KNTV had kept on broadcasting from San Jose only, then it might have lost as lot of market to the north.

I would like to get some North Bay stations, particularly the public TV station that shows regular NHK programming, such as "Begin Japanology", which despite the slightly strange name, is a gem of a 30 minute documentary series about various aspects of Japanese life, culture, and products. It can be viewed on the Internet but it's just not the same as setting the recorder and watching it later.

It used to be broadcast on one of the SF digital stations, but was dropped a few years back. Now the nearest broadcast station is somewhere in Sonoma County, and can't get that here, at least not over the air digitally.





http://www3.nhk.or.jp/nhkworld/english/tv/japanology/

 

[kb0nes]

digital signals don't travel as far as VHF analog

This mostly seems true since the majority of digital signals are frequently UHF, the transmission mode doesn't change propagation. VHF signals penetrate structures and foliage better and suffer less absorption from moisture (but they do suffer more from noise). This is the reason that many of the broadcasters dropped back into their high band VHF channel allocations shortly after the digital migration. Our market here in MN went all UHF initially but when allowed a handful of stations have dropped back into the channel 8-11 range. They seldom seem to use the low VHF range mostly due to antenna size and the possibility of non-line of sight propagation interference (skip).

As for digital vs analog on the same frequency the coverage area for a perfect picture with digital is larger as a generalization. Digital signals deal with noise and multipath far better and have a narrower bandwidth. The bad thing is with digital transmission is when you start to get on the edge, then only a minor fluctuation will cause artifacts or total lost of picture.

It would be really interested to have an antenna on a rotator just to experiment. If I were to do that I'd be sure to get pretty good sized antenna and pay attention to the front to back ratio. Not a lot of sense in messing with a rotor unless the antenna is pretty pointy.

I have one friend here that has a tower with a rotatable stacked pair of FM antennas on it. Each antenna has an 18 foot boom and they are phased together with a mast mounted preamp. A tunable pre-selector helps kill the strong first ajacents. He can receive FM in stereo from ~200 miles on most days and with a tropospheric enhancement occasionally signals from 1000 miles distant will come up!

 

[rp2813]

Phil, I think your post directly above explains why KGO has been more problematic than other stations. 

 

Today we have some high clouds in advance of a weak weather system due in here tomorrow, and KGO is displaying slight, infrequent choppiness, mainly momentary loss of sound.  It's not horrible, but per the link I posted further up, KGO broadcasts on low band VHF from the tower in SF, and on UHF from a transmitter closer to me, but the nearby tower is NE of here instead of NW, which is the direction I have the UHF antenna aimed.

 

Apparently KGO's VHF signal is too weak from the SF location so I think what I'm getting is coming from the nearby UHF tower.   I've aimed the VHF antenna to the NE, but realize it's not designed to receive UHF, and am not seeing much improvement.  I think KGO will remain an issue except in fair weather, at least until I make a decision on upgrading.  Maybe I need to revisit the rabbit ear dipole addition on the UHF antenna's hairpin block, or just upgrade to a modern rig that will receive both VHF and UHF.

 

The reason I think I'm receiving the KGO signal over UHF is because when I ran a new channel scan on the converter box, I ended up with duplicates of channel 2, which has a similar arrangement over separate transmitters in the same locations as KGO, but channel 2 broadcasts over UHF from both.   So far, appearances of channel 2 from both towers are coming across fine. 

 

[sudsmaster]

Last month KPIX was experiencing a lot of dropouts and coarse pixelation. Not sure if it was weather related or a station broadcasting issue. This month it appears better. Don't generally have a problem with KGO, but then I'm a lot closer to Mt. Sutro than you are.

I remember when KGO was the only station transmitting from Mt. Sutro. We used to live nearby the Mt. and my brother and I used to take walks up there. I remember when the big tower went on top, it's probably about as tall as the Eiffel Tower, except on top of a mountain, and nowhere near as charming. Think War of the Worlds Martian mechanical destruction device in bright orange. It was promised to give a ghost free picture in every corner of the city, but oddly those right under it got worse reception.

 

[rp2813]

It seems strange when a little college station like KCSM/60 with presumably weaker signal can be received more reliably than a network affiliate like KGO/7, even though they're both broadcasting from the same tower.  I've decided I can't improve reception on KGO with my current system, but it's not bad enough to make me go out and buy a new antenna.  We'll see what happens when SF's summer fog season kicks in.

 

Also, I just heard that negotiations are in progress to sell KCSM, so we can say goodbye to the only PBS alternative to the bloated KQED empire in this market.  Prepare for foreign language, shopping, infomercial or religious broadcasts on channel 60 down the road.

 

[ea56]

Ralph,

I don't know a whole lot about tv antenna's other than we used to use them before cable tv. But as a life long resident of the greater Bay Area I can safely state that KGO always had the weakest signal, no matter where we lived, even when we were just across the Bay in El Cerrito. There was always more interference on channel 7. Sometime's I even remember that when we were using rabbit ears one of us would have to hold one of the rabbit ears to get 7 to come in clear. Yet we could get KCRA from Sacramento clear as a bell and it was about 80 or more miles away. Seems like an ABC affiliate would have had a more powerful transmitter.
Eddie

 

[sudsmaster]

Sale of KCSM?

Ralph,

That's bad news. I enjoy the jazz (music only) station 60.3, as well as the France24 (Fraaaance-van-cat) continuous coverage.

Oh, well, there's always internet streaming...

France 24 Live Stream

 

[rp2813]

Eddie, thanks for confirming that KGO has always been quirky.  I sort of recall it being ghosty in the olden days when other network affiliates were fine, even though most were broadcasting from the same general area before Sutro tower went up.  The other station that tended to come through less than perfectly was KTVU channel 2.  I remember on our 1951 Capehart, 2 was always a bit snowy.  It improved when we got our '62 Airline, but with rabbit ears on other sets, 2 was more compromised, and 7 (KGO) always needed adjustments.

 

I read many, many years ago that the reason so many ABC stations are found on channel 7 is because there was a rumor or concern in the early days of TV (cold war era?) that the FCC or whatever agency might claim the use of the lower VHF frequencies for government use, so by snapping up all of the channel 7 frequencies, ABC would essentially be the first viewable channel on the dial.  In the days before remote control, that was a strategic position.   I don't know if there's any truth to this legend, since ABC was late to the TV party behind NBC and CBS anyway.   In the end, ABC landed downstream from NBC and CBS, which in major markets can usually be found somewhere in the range of channels 2 through 5. 

 

Rich, it gets worse re: Channel 60.  In that same story I mentioned above, it was reported that the jazz station KCSM (91.1 FM or 60.3 on TV) has cut staff and live programming and is now running some shows prerecorded out of Chicago.  A source at KCSM didn't exactly confirm or deny rumors that the radio station is up for sale (presumably ours is a hot market for radio and there's no shortage of potential buyers), so we might be saying goodbye to jazz in the Bay Area for good this time, as there probably isn't anyone willing to step in like KCSM did to fill the void left when KJAZ was sold quite a few years ago.

 

[sudsmaster]

Ralph,

Thanks to corporate chain ClearChannel, local radio has become a wasteland of sorts.

Gone: KKSF, which played great "smooth jazz" for a few decades, and had an equally great annual "Sampler for Aids Relief" CD release with the best smooth jazz hits of the year.

Gone: KDFC, the area's sole remaining classical music station, albeit it returned last year as a low power public station, with limited reception and the usual interminable pledge breaks.

For a while digital HD radio seemed to be picking up some pieces, such a digital branch of KISS-FM picking up the smooth jazz format. Sadly, they dropped that format in favor of mass produced hip hop dreck last year, so even that work around for the dearly departed KKSF has gone under.

At work I find I'm listening mostly to live streaming of KDFC on my Bluetooth headphones. It works well enough since the desktop system has a powerful enough bluetooth capability, except for the aforementioned pledge breaks. It is perhaps the direction that a lot of quality radio is going - dropping broadcast or having limited, low power broadcast capability, in favor of internet audio streaming.