Weak vs. Strong conundrum

arkbldr

DTVUSA Rookie
#1
I have a carefully configured and tested stacked pointable large VHF Channel Master antenna and a good UHF yagi antenna appx. 4' above it all mounted on a 50ft. Tower with a Channel Master 0264DSB Booster and get a lot of dtv channels with very good strength here in a fringe location in central Wisconsin.
Can anyone explain why I can get a channel like 27( actually 26) with 100kw output out of Madison with 90% signal but can’t get any signal recognition at all for channel 3 (actually ch 50) from Madison which has 600kw output. Is there possibly a defect in my converter box, it is a Dish TR 40. Have no problem receiving other strong UHF or VHF signals in other cities pointed to.
 
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#2
Run your TVfool report and look for co-channel or adjacent channel interference sources.

Post your link to your TVF report so we can also evaluate it.

If you can identify your exact antenna models, that would also be helpful.

A 4 inch stack is aweebittooclose.....
 
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arkbldr

DTVUSA Rookie
#3
tvfool info

Thank You for directing me to the tvfool website. I now have some clues to what may be the problem. # 1 I may need a better Yagi antenna. #2 I was expecting WISC 3 signal to be at least as strong as their old analog vhf signal which was always the best and favorite Madison station I could get. I don’t understand why they would settle for a loss of coverage like this. They have gone from the strongest Madison channel to the weakest now in south central Wisconsin. Their move to a high freq. UHF signal must have put them out of reach for me and a lot of other viewers now. Am I correct that the higher the frequency of the UHF transmission the less likely it can deal with terrain obstructions such as distant intervening bluffs or ridges regardless of the power behind it. My yagi is an older Jerrold Sharpshooter brand 14-70. My VHF is the largest Channel Master Quantum I could get years ago. Looks like I may have to start the dreaded climbing again and try a different Yagi to have any chance of getting all my old favorites I had before the switch over to dtv. Any suggestion as to the best Uhf ant. For this application. Is the 0264DSB Amp still suitable for the dtv signals as well ? Link to Tvfool printout here:

TV Fool

I don’t really know how to interpret the colorful “transmitter profile detail” image that comes up when you click on a specific channel in the “estimated signal strength” channel list. Is the very right green side of the image my location? Is the blue color where the best signal is.
 
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#4
On the individual channel plots, you are in the lower right corner and the transmitter is depicted on the left margin. Intervening terrain and it's effect on signal strength are then depicted.

WKOW has 1,000 kW ERP, not 100 kW. Due to a directional antenna, only 863 kW is directed in your direction. WISC uses an omni antenna at 603 kW.

Low-VHF bend more easily "over the horizon" than does UHF. However, it is highly susceptible to noise and interference, both natural and man-made, on DTV broadcasting. Only about 35-40 full-power DTV stations nationwide remain on low-VHF.
 

Trip

Moderator, , , Webmaster of: Rabbit Ears
Staff member
#5
Actually, WKOW has not built out their 1000 kW permit, and has instead only built out 800 kW. Given the directional pattern, that implies 690 kW in the direction of the original poster.

- Trip
 

arkbldr

DTVUSA Rookie
#6
1 last question

Thanks for the info posts,
I find that if I disconnect the VHF ant. From the booster and just leave the UHF connected I can watch the weaker UHF signals I am looking for. Would it likely work if I use a separate booster and power supply for each antenna and bring down 2 coax leads and combine them just before the converter box . It would be a lot easier for me than changing out the Yagi to a newer larger one.
 
#7
Yes. In strong signal areas, I have gotten the best results by amplifying UHF only. (If amplification is truly needed) You will need to run a separate VHF coax cable inside, and then join the 2 cables together with a UVSJ anywhere "after" the power injector.
 
#8
Yes. In strong signal areas, I have gotten the best results by amplifying UHF only. (If amplification is truly needed) You will need to run a separate VHF coax cable inside, and then join the 2 cables together with a UVSJ anywhere "after" the power injector.
If amplification of only UHF is needed, just use a UVSJ that has power pass on the UHF port and install the preamp between the UHF antenna and the UVSJ. That eliminates extra cable runs.

Examples of available products that are DC-pass on the UHF side only are the Radio Shack 15-2586 and Antennas Direct EU385CF. The commonly recommended UVSJ from Holland or PicoMacom are DC-Pass on the VHF side.
 
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Thomas G

Contributor
#9
Actually, WKOW has not built out their 1000 kW permit, and has instead only built out 800 kW. Given the directional pattern, that implies 690 kW in the direction of the original poster.

- Trip
How did you arrive at 690 kW? Does broadcast power change with the directional pattern?
 

Trip

Moderator, , , Webmaster of: Rabbit Ears
Staff member
#10
If he received 863 kW at the 1000 kW power level due to the directional pattern, I worked the formula backwards to figure out which field number value of the directional pattern he was facing (answer: 0.929), then worked through it forward but with 800 in place of 1000.

800 * (0.929)^2 = 690.

- Trip
 
#11
If amplification of only UHF is needed, just use a UVSJ that has power pass on the UHF port and install the preamp between the UHF antenna and the UVSJ. That eliminates extra cable runs.

Examples of available products that are DC-pass on the UHF side only are the Radio Shack 15-2586 and Antennas Direct EU385CF. The commonly recommended UVSJ from Holland or PicoMacom are DC-Pass on the VHF side.
Thanks ProjectSHO89,

I didn't know Antennas Direct had that combiner that is designed for outdoor use.:thumb: I generally try to keep all splitter & combiners indoors whenever possible.
 
#12
If he received 863 kW at the 1000 kW power level due to the directional pattern, I worked the formula backwards to figure out which field number value of the directional pattern he was facing (answer: 0.929), then worked through it forward but with 800 in place of 1000.

800 * (0.929)^2 = 690.

- Trip
Nice, thanks. I've got to check my thread subscriptions more often. :p
 
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