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Guest Message by DevFuse

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Weird OTA reception


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3 replies to this topic

#1 OFFLINE   bleggett29

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Posted 05 May 2010 - 12:34 AM

Can anyone tell me why I can't get any OTA reception 50 miles away but can get full power for stations 100 miles away?
My approx. location 38.256953,-76.479306 -- about 50-55 SW of Wash., DC. I've mounted an 8-bay bowtie antenna up about 15 feet several days ago. Been trying like mad to get DC stations. Once in a while I'll get 66.1 from DC, and 22.1 from Anappolis; both with crappy signal. Or I can turn the ant. toward Salisbury, MD and get 16.1, 47.1, and 28.1 with reasonable signal. Tonight, I noticed 15.1 WHRO was showing up during a scan. I lived in Norfolk back in the late 80's and knew instantly where that was from---just a bit over 100 miles away! My curiosity go me and pointed the ant. due south. OMG! I was getting nearly all the major stations from Norfolk at full power. WTH? Can someone explain this to me?

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#2 OFFLINE   BattleZone

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Posted 05 May 2010 - 10:53 AM

There are all kinds of possible reasons:

- The broadcasting antennas aren't going to be completely omni-directional; you may be in a null area of the antenna.

- Terrain features between you and the antenna (hills/trees).

- RF interference from nearby sources.

- Inadequate or inappropriate antenna (are any of these stations transmitting on VHF frequencies [2-13]?)

- Stations not broadcasting with adequate power.


Start by going to http://www.tvfool.com, enter your address, select "Digital Only", and post the resulting plot here.

#3 OFFLINE   bleggett29

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Posted 05 May 2010 - 01:32 PM

There are all kinds of possible reasons:

- The broadcasting antennas aren't going to be completely omni-directional; you may be in a null area of the antenna.

- Terrain features between you and the antenna (hills/trees).

- RF interference from nearby sources.

- Inadequate or inappropriate antenna (are any of these stations transmitting on VHF frequencies [2-13]?)

- Stations not broadcasting with adequate power.


Start by going to http://www.tvfool.com, enter your address, select "Digital Only", and post the resulting plot here.


tvfool report
Yes, I know I'm in an area that's in a void. Hell, we can barely get any decent FM here. My ant. is rated for 12db gain in the mid UHF range. I have a pre-amp only to compinsate for the 75 foot RG6 run. I figure I should be able to pick up anything with -10db(NM) or less(UHF of course).
But I believe I have found the answer for my original question---Tropo Ducting. I was actually able to get decent signals from DC, Baltimore, Richmond and the Norfolk stations last night after posting. Hell, I was able to get Richmond and Norfolk or Richmond and DC at the same time with the ant. pointed midway between.
I knew from the start it would be unlikely to pick up anything useful. I was just wondering why I was getting long distant stations and not mid distant stations. Looks like I found my answer. And got the mid distant stations after some tweeking the direction of the ant.

Pretty interesting stuff Tropo ducting does.

#4 OFFLINE   Jim5506

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Posted 05 May 2010 - 05:49 PM

Stations in Maryland are mostly over water from you, whereas DC is overland.

Over water is much easier for signal propagation plus Salisbury is 10 miles closer.

The 100 mile away signal was probably tropospheric ducting which will occur occasionally allowing reception 200, 300, 400 miles, but it is not reliable in any sense.
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