What causes interference with HDTV over-the-air reception?

[Johnnyallen]

I have an HDTV rabbit ears antenna with a signal booster to receive local HDTV stations. Making matters worse is the fact that I live in a basement apartment. The antenna sits on a window sill which is about 8 inches above ground level.
I have to move the ears and antenna frequently to tune in certain stations especially in hot weather.
My question: why does my body affect signal strength?
BTW Remember the good old days of analogue TV when you could tune to an empty channel and watch the Cosmic Microwave Background noise.

 

[davenn]

My question: why does my body affect signal strength?

because it capacitively loads the antenna

 

[anorlunda]

i used to have similar problems with FM radio when I lived on a boat, and the antenna was at, or slightly below, sea level. Based on that, I would guess that anything you can do to raise the antenna above ground will improve things. Even 4 inches might make a big difference, especially on rainy days.

Mention it to your landlord. He might offer help.

 

[Herman Trivilino]

I have an HDTV rabbit ears antenna with a signal booster to receive local HDTV stations. Making matters worse is the fact that I live in a basement apartment. The antenna sits on a window sill which is about 8 inches above ground level.
I have to move the ears and antenna frequently to tune in certain stations especially in hot weather.

Is there a window like that on the opposite wall that you can try? It sounds like you could benefit from an outdoor amplified antenna.

 

[berkeman]

My question: why does my body affect signal strength?

One issue is multipath -- you are a lossy reflector at HDTV transmission frequencies.

 

[jim hardy]

i'd say go to this site and type in your address
https://www.fcc.gov/media/engineering/dtvmaps
it'll show you all the stations you're apt to receive
click on the call letters for its direction and the channel number it actually broadcasts on.(which may not be the same channel number it's known by.)

You might be able to make a couple of antennas for different frequencies that you could switch into your amplifier with something like this

that image is from Home Depot but plenty of places sell them

If you're getting by with rabbit ears you'd almost surely benefit from an antenna made for your specific stations. Look up "Folded Dipole"
i made one and hid it behind a drapery with decent results
but to get the weaker stations reliably i had to move it up to the roof.

TV channel frequencies here
https://en.wikipedia.org/wiki/North_American_television_frequencies

good luck !

 

[jtbell]

channel number it actually broadcasts on.(which may not be the same channel number it's known by.)

I haven't been paying attention to channel allocation politics for a while, but now I see that many stations are going to change the channel they actually broadcast on, starting next year.

In my area at least, it looks like most of the changes will take place next August (2019). Fortunately, all except three stations are staying in the same band (UHF versus high-VHF) so hopefully this won't affect my reception for those stations except maybe for having to make my TiVo "re-scan" the channels. But the TiVo has been notifying me about various changes in the channel lineup automatically all along, so maybe it will also pick these up automatically.

Two stations are disappearing as independent channels. One is a state-run PBS station whose territory overlaps with another, stronger one in the same network. The other is owned by the same company as another station in this area, so I suppose they'll simply share the same channel going forwards. The one that's disappearing is already carried as a sub-channel of the other one, in addition to its own transmitter.

One station is moving from UHF (16) to low VHF (2) which means it will disappear as far as I'm concerned, because my antenna setup doesn't receive low VHF (2-6). But I never watch that station anyway, so I won't miss it.

 

[CWatters]

Directional aerials typically work much better than rabbit ears if you only have to point at one transmitter. Size and height matters.

 

[jim hardy]

What that fcc.gov site shows for me - only two channels 8 and 19

My home made two channel Yagi , specific for channels 8 and 19

works quite well only about twelve feet up in the air.
My two stations are near one another so a single boom would have worked as well pointed between them. ..

old jim

 

[tech99]

One issue is multipath -- you are a lossy reflector at HDTV transmission frequencies.

I have an HDTV rabbit ears antenna with a signal booster to receive local HDTV stations. Making matters worse is the fact that I live in a basement apartment. The antenna sits on a window sill which is about 8 inches above ground level.
I have to move the ears and antenna frequently to tune in certain stations especially in hot weather.
My question: why does my body affect signal strength?
BTW Remember the good old days of analogue TV when you could tune to an empty channel and watch the Cosmic Microwave Background noise.

Reception will fluctuate because the received signal is made up of several components coming from reflecting objects, such as cars, houses, trees and your own body. These add together in random and varying phase. It is probable the because of your low location, a direct signal is not being received.
I think you would find an improvement for UHF if you can use a log periodic antenna (see Wiki no doubt). This has a very clean pattern and covers a wide band of frequencies, and will reduce the number of multipath signals.

 

[tech99]

Also, find out if the desired transmitter is horizontally or vertically polarised and rotate the antenna accordingly.