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Old 19-Mar-2013, 8:10 PM   #1
briank101
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Not getting WOCK-CD Chicago Ch. 4 (13.1)

I need help in trying to tune in the VHF-Low station (Physical channel 4.1) WOCK-CD from Chicago.
Here is the Signal Analysis report http://www.tvfool.com/?option=com_wr...1ddae8e21cb99e

I am using a very large Philips 7700 long-range VHF/UHF 51 element antenna
http://www.p4c.philips.com/cgi-bin/c...scy=US&slg=AEN
located in the attic.
Note I have verified correct aim, and I am fortunate that all the Chicago stations I wish to receive are within a 2 degree range 73,74,& 75 degrees from the impressive height of the Hancock, Trump, AON Center, and Wilis(Sears) towers respectively in Chicago. Even at almost 42 miles out, I am pulling in the UHF stations WCHU-LD, W25DW-D which have lower NM than WOCK-CD. WOCK-CD comes from the Hancock and I've verified with its current radiation pattern, that it's putting out 0.18 kW towards my direction. I know they have a CP to increase the power to 1 kW, which would put 0.61 kW in my direction. I use channel 6 WKQX-LP (analog) to test my VHF low reception, which broadcasts also from the same tower (John Hancock center). I optimized the picture on channel 6 to give the least amount of
noise (it's still a bit "snowy", but stable and in color) It was interesting turning off the Wi-fi in the room below reduced the noise by a good bit, turning off any other equipment including CFL lights didn't make any difference to the channel 6 analog signal. I tried with and without pre-amp to no avail. There is an FM station 88.7 FM, 2 miles away with -27.9 dBm of signal, but at 223 degres it not directly 180 deg opposite the Chicago stations (255 deg would be in line with the back of my antenna). My pre-amp has an FM-trap, would enabling that help?

WOCK-CD is the affiliate for MundoFOX which I understand has a 720p picture on 4.1 (13.1 virtual), and Mega TV. My wife speaks Spanish, and I would like to see WeatherNation on 4.4 (13.4).

Anyway am I wasting my time to get a VHF low station with 160 watts in my direction (42 miles away) or should I wait until they bump it up to 1 kW (i.e 610 watts in my direction)? Also is there a way to find out from the FCC website when the station has begun to use their CP license?
Putting this large antenna outside is not an option for now.

Thanks,
Brian (saving $63/mo since dropping Dish Network)

Some interesting facts I dug up relevant to Chicago OTA viewers:

- WPVN-CD 24.1 (Phys 20) broadcasts from Trump Tower (Chicago's newest large high-rise)
W25DW 25.1 (Phys 25) broadcast from the AON building (Note: TVFool mistakenly reports it as Physical Channel 22)
WLS 7.1 (Phys 7) just went off the air (as of yesterday) Digitial 7.1 is now just received on Physical channel 44.
- Fox 32 will add Fox Movies this Spring on virtual channel 32.2 (Phys 31.4)
- CBS has launched CBS Plus in the other large markets, will they do it here??... who knows.

Also some facts for viewers living near me (60538):

- Local digital Channel 40.1 W40CN-D (Waubonsee College) will prevent 40.1 Chicago (Estralla) from being received.
- Local analog channel 30 (WSPY-LP) will prevent WDCI-LD 57.1 (Phys 30) from being received
- I can recieve 71 digital channels at my location counting the sub-channels that is. It's amazing what coverage a small class A station on top of a Chicago skyscraper can produce.
- Maybe WOCH-CD will be receivable when/if they boost their power 3X as per their CP.
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Old 20-Mar-2013, 3:41 AM   #2
GroundUrMast
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You might have a chance if you could move the antenna outside, free of the signal attenuation and reflection caused by the roof construction. By moving the antenna outside, you also reduce the amount of RF interference received from sources in the home.

If I had the room, I might consider building a rhombic antenna for the L-VHF band... You need gain, but also need to make every effort to minimize reception of noise and interference.

http://forum.tvfool.com/showthread.php?t=2858
http://forum.tvfool.com/showthread.php?t=109
http://forum.tvfool.com/showthread.php?t=2865

FWIW: A power increase of three times expressed in decibels rounds to 4.8 dB. That's not insignificant, but it's not going to dramatically expand WOCK's service area.

Last edited by GroundUrMast; 20-Mar-2013 at 3:46 AM. Reason: Power x 3 in dB
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Old 20-Mar-2013, 4:09 AM   #3
teleview
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Install the antenna above the Peak of the Roof in such a manner that reception is not blocked by the roof or house in the direction of , east / north east.

Here are some Strong and Sturdy above the roof antenna mounts.

http://www.ronard.com/antenna/pointing/pointing.html , use the 5 foot tripod antenna mount.

http://www.ronard.com/34424560.html , use the #4560 eave antenna mount.

http://www.ronard.com/ychim.html.http://www.ronard.com.

http://www.ronard.com.

Buy the ronard antenna mounts at solidsignal by typing the word ronard in the solidsignal search box or buy from ronard.

Here are some places to buy reception equipment.

http://www.solidsignal.com.

http://www.amazon.com.

_____________________________

Yes switch the FM trap in/on.

_____________________________

As always , trees and tree leaves , plants and plant leaves , do a good job of , multipath/reflecting , absorbing , blocking , OTA=Over The Air , Digital Broadcast Tv Reception , and so do buildings and other obstructions including your own roof and house.

It is best to install the antenna at a location that has the least amount to no amount of obstructions of any type or kind in the direction/s of reception including your own roof and house.

___________

Digital Broadcast Tv Tuners can develop - Digital Glitches - that are not cleard out with simple channel scans.

Do a Double Rescan.

http://www.dtv.gov/rescan.html.

______________________

Yes it is True.

Electric and electronic devices can disrupt and block Digital and Analog Tv reception.

And Yes it is True.

Analog Low Power and Analog Repeater Tv stations have until Sept. of 2015 , to convert to digital or cease transmitting.

Most have converted digital , some are still transmitting analog.

______________________________

The Philips antenna is a Good older antenna design that does very well receiving the Vhf low band channels of 2 thru 6.

The design of the back part of antenna is a < shape double boom log periodic.

The double boom must be mounted to the plastic insulation blocks that keep the double boom from shorting out to the mast pipe.

Last edited by teleview; 20-Mar-2013 at 8:02 AM.
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Old 20-Mar-2013, 4:01 PM   #4
briank101
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Thanks for the very helpful responses. So I may have to put the antenna on the roof after all, though from what I've read I thought the lower the frequency the less likely it is to be attenuated by structures such as wood and roof shingles and being receivable beyond the horizon. However I'm now learning that higher noise susceptibility is the Achilles heel of VHF Low band reception (and digital reception is nearly all about S/N right?) and that the advantage of roof mounting may have just as much (if not more) to do with furthering the antenna from the noise sources as it is about signal gain at VHF Low band frequencies. Possibly a high VSWR is also an issue as per this nice article http://www.tvtechnology.com/conferen...visited/183659, as all my electrical wiring is in metal conduit running across the floor of my attic 2 feet under my antenna. NE Illinois code specifies all electrical wiring must be in EMT conduit which may help however with power line noise emission, while causing possible high SWR due to its proximity. Thankfully the weak channel 6 analog station from the same TX site can sort of be used as my poor man's test equipment for seeing noise on the signal. I'm still wondering why my wireless n router causes noise in the VHF low band.

I may hold off putting it on the roof until the 4.8 dB increase, because my 60" Sony EX500 looks like it on the verge of locking on, as it does show a "Now tuning" for about 25 seconds when I enter 4.1. On empty channels it show "No Signal" right away. Unfortunately, the signal diagnostics don't display anything at all unless there is at least a 15 dB S/N from the signal. My older Sony digital XBR960 CRT at least shows a signal level even when not locked in.

Last edited by briank101; 20-Mar-2013 at 4:04 PM.
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Old 20-Mar-2013, 4:36 PM   #5
GroundUrMast
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Quote:
...the lower the frequency the less likely it is to be attenuated by structures such as wood and roof shingles and being receivable beyond the horizon...
Generally true.
Quote:
...digital reception is nearly all about S/N...
Though the symptoms appear quite different, the same is true of analog signal transmission as well. But again, true.

The further you can get the antenna away from other metal and power lines in particular, the better.

The article you've cited does speak of VSWR problems, but correctly points out that the problem is with small antennas that lack intentional design support for the low VHF channels. You should expect acceptable VSWR if using an antenna designed to operate in the low VHF band. The Phillips SDV7700K should have an acceptable VSWR in all three bands.

Of all the factors that help provide reliable reception, antenna gain and avoiding reception of noise/interference are at the top of my list.
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Old 20-Mar-2013, 6:45 PM   #6
teleview
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VHF low band channels 2 thru 6 , have Always had reception situation situations.

Analog low band Tv reception situations , show in the picture.

Snow from weak signal.

Drifting lines.

Wiggle lines of FM radio interference (mostly on channel 6 because channel 6 is next to the FM radio frequencies).

Dashed lines of electric motor interference.

Multipath/reflections also known as ghosts.

All those years of interference in the analog picture were common , and people did not think much about it , was accepted as Tv reception , that is the way it was.

The same reception situations effect Digital Tv transmission and reception.

The Digital Broadcast Computer Tuner can make corrections for the different types and kinds of interference and low signal strengths and maintain a clear picture.

However at some point the Digital Tuner will not be able to correct all the situations and the picture will break up into blocks and or go blank. And with Digital Tv the sound goes out also.
_________________________________________


The following recommends are for Digital Tv transmission and reception Only.

For low band Digital transmission and reception a way to over come the interference issues is to increase transmission power.

The FCC should authorize low band transmission power increase beyond what is maximum allowed now.

Make a new stronger maximum allowed.
_____

And an other way is transmitter antenna tilt , tilting the transmitting antenna at more of a downward angle so that more of the signal strength power is concentrated in a smaller area of the transmission area.

_____

Last edited by teleview; 20-Mar-2013 at 10:13 PM.
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Old 21-Mar-2013, 3:45 PM   #7
briank101
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Thanks for the info on the interference patterns on the analog signal, which can be more helpful for diagnosis vs a digital signal. In fact when the last analogs shut down it will be harder to track down the noise. Perhaps one can hold on to an old VCR RF modulator (and an old TV) to diagnose noise sources. If a neighbor has their VCR modulator set to Ch. 4, could that signal be the source of noise? This gives me an idea, I do have an old VCR where I can generate a very weak Ch 4. signal transmitted in the air, with a small bit of wire perhaps, and connect my old CRT to the antenna cable and see what noise pattern I can see on that frequency. I thought I powered down almost everything in the house, that could be a source of noise, computers, Wifi, ethernet switch/routers, CFLs, other radios, TVs near the antenna, even the smoke alarm circuit.

In past experience what has been the top causes of VHF low band noise?

I often wondered why the FCC has restricted low VHF TV stations to such low powers, because unlike with typical omni-directional FM reception, TV viewers need to user directional antennas to receive medium to long distance stations. Even if a co-channel station is somewhat short-spaced (when operating at higher power), for the vast majority of the viewers, the directionality of the reception antenna will allow the desired station to be received properly. I think the FCC are thinking in terms of omni-directional reception when determining spacing and power-levels. I can see room for optimization of power levels and spacing, taking into consideration the probability of two high powered stations being in the same direction for a significant number of end users. i.e. it might not be good short space a co-channel station in western Michigan directly E or NE of Chicago, but would be likely OK to short-space a co-channel station direction W, or SW of Chicago at the same short-space distance. When I say short-spaced, I mean as a result of using higher power.
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