Question: Antenna no longer receiving certain channels -- Downtown DC

Columbo

DTVUSA Jr. Member
#1
I live on the top floor of a high rise in downtown DC. Since the digital transition I've used a Terk HDTVa and have pulled in numerous channels with excellent quality. I've seen on these forums that often you all suggest not using the amplifier when you're so close to the stations, but I've had much better reception over the years doing so. Also I keep the VHF antennas (rabbit ears) fully extended.

Although my antenna is an indoor antenna I use it outdoors, on a covered balcony, facing generally north-west (the direction of the majority of my local station) and protected from the elements. Again for years I've had excellent reception from NBC (4.1), Fox (5.1), ABC (7.1), CBS (9.1), PBS (26.1), UPN (50.1), and several other stations and sub-channels.

On Sunday, 1/10/2010, I suddenly lost 9.1 (vhf) & 26.1 (uhf) and a few other less important stations. I've tried the following, none of which have fixed the problem:
  • Remove Amplifier
  • Disconnect antenna, scan channels to remove them from memory, reconnect antenna and scan again
  • Change antenna direction a few degress at a time
Also I use it on one tv. It is connected to the tv by about 30 feet of coax.
Any other ideas or suggestions? Thanks in advance.
 

FOX TV

Contributor
#2
I live on the top floor of a high rise in downtown DC. Since the digital transition I've used a Terk HDTVa and have pulled in numerous channels with excellent quality. I've seen on these forums that often you all suggest not using the amplifier when you're so close to the stations, but I've had much better reception over the years doing so. Also I keep the VHF antennas (rabbit ears) fully extended.

Although my antenna is an indoor antenna I use it outdoors, on a covered balcony, facing generally north-west (the direction of the majority of my local station) and protected from the elements. Again for years I've had excellent reception from NBC (4.1), Fox (5.1), ABC (7.1), CBS (9.1), PBS (26.1), UPN (50.1), and several other stations and sub-channels.

On Sunday, 1/10/2010, I suddenly lost 9.1 (vhf) & 26.1 (uhf) and a few other less important stations. I've tried the following, none of which have fixed the problem:
  • Remove Amplifier
  • Disconnect antenna, scan channels to remove them from memory, reconnect antenna and scan again
  • Change antenna direction a few degress at a time
Also I use it on one tv. It is connected to the tv by about 30 feet of coax.
Any other ideas or suggestions? Thanks in advance.


Welcome to the forum,

Just a little data mining to start would be good. What type of receiver are you using? Is it a converter box, or a set with a built in tuner? With all of the radio traffic in downtown DC, you could possibly have an interference issue from another source of RF energy.

Please describe what reception equipment you are using in detail, and include the antenna brand, type, and model and post your zip code at minimum so someone can pull up your predicted signal levels for your location and we will start form there.

We track down problems by the process of elimination, as well as using your predicted signal levels for your location, and your zip code is a good starting point.
 
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Columbo

DTVUSA Jr. Member
#3
Thanks.

The antenna is the Terk HDTVa amplified indoor antenna (linked to in original post). About 30 feet of coax between the tv and the antenna. The TV has a digital tuner, there is no equipment (aside from the amplifier that came with the antenna) between the tv and the antenna. Zip code is 20005.

If you need further info, let me know. As I mentioned in the original post this setup has worked successfully for years. It is only since 1/10/2010 that I've lost a couple of channels.

Thanks much.
 

Don_M

DTVUSA Member
#4
Couple of observations:

• The HDTVa has a built-in amplifier, so please describe how you removed the amp. Most antennas with integrated amps need power to work properly, so if "removed" really means "unplugged," that can and does negatively impact function.

• The fully-extended dipoles (rabbit ears) are not trimmed to the optimum length for capturing signals from ABC on 7 and CBS on 9. Here's how to do it: First, lower the dipoles to horizontal. Collapse both until they reach a combined 31 inches, tip to tip. When done, each rabbit ear should be the same length -- roughly 15 inches. Finally, raise the dipoles until they're at right angles to one another, and each is at a 45-degree angle to the floor. This procedure tunes the dipoles to the average wavelength of both channels correctly.

• Is the antenna situated behind, mounted on, or located close to, anything metal -- the balcony railing, a chair, table, window/door frame, etc.? These surfaces should be at least one foot away from the front and sides of the antenna for UHF stations, and three feet away for VHF-high signals such as those from ABC and CBS. Maintaining a distance of about a foot from below and the rear would be a good idea as well.

• Is the antenna level? Balconies almost always have a slight slope so that rainwater sheds away from the building. Therefore, every surface whose legs rest on the balcony has the same slope. Left uncorrected, this points the antenna slightly downward, toward the ground, when it should be pointed right at the horizon. Even minor deficiencies of a few degrees can make a difference.

• How is the 30-foot cable routed inside? Was it crushed in a door or window frame? Crushing frequently causes internal short circuits that ruin cables, and reception. Use a flat coax to work around this problem.
 

Columbo

DTVUSA Jr. Member
#5
• The HDTVa has a built-in amplifier, so please describe how you removed the amp. Most antennas with integrated amps need power to work properly, so if "removed" really means "unplugged," that can and does negatively impact function.
I wasn't sure on terminology. The antenna has a lenght of coax coming out of it (say 6 feet) and also came with seperate small box connected to a power supply with two coax connectors, one male & one female. So it is possible to completely remove the amplifier from that antenna. Now that may have a negative impact on the antenna, I was just letting you all know I had tried it both ways.

I do use a flat coax to go under a window to enter the condo. The total cable lenght is broken up by a few different cables (I know this is not ideal).

Antenna is level & away from metal.

I've give your rabbit ear suggestion a try, but seeing as this setup has worked for a couple of years I can't see that suddenly being the problem. I wondered if it was the fact that I was using an antenna made for indoor use outside (even if covered/not getting wet) but again why would just a couple of channels drop off?


I'll either report back or give a different antenna a try. Again I appreciate the feedback.
 

weroberts

DTVUSA Jr. Member
#6
Any new Electronics in the house? Electric Heater maybe. Depending on location these can screw up a signal. The setup I have in my living room looses channels when the microwave in the kitchen, 16 feet away, is turned on. Also that antenna looses stations if within about 18 inches from my Dish Network box.
If you have anything new try turning it off.
 

Columbo

DTVUSA Jr. Member
#7
Any new Electronics in the house? Electric Heater maybe. Depending on location these can screw up a signal. The setup I have in my living room looses channels when the microwave in the kitchen, 16 feet away, is turned on. Also that antenna looses stations if within about 18 inches from my Dish Network box.
If you have anything new try turning it off.
Thanks, that is a possibility. Nothing new actually, but I did move a compact dehudifier recently. I actually moved it farther away from the TV (and it typically only runs overnight) but that is a potential source of interference.

I've been considering an antenna designed for outdoor use for the last few months, this might be a good time to make the switch. I must have a low profile antenna so I was considering the Terk HDTVo, although the cost is higher than I like. If the antenna gives me a number of years without a cable bill it is worth it.

Thanks again everyone.
 

Trip

Moderator, , , Webmaster of: Rabbit Ears
Staff member
#11
TV stations are required to have both audio and video, but the two don't have to be the same programming.

- Trip
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#12
The HD 1080 isnt much better on UHF and is worse on VHF High, than the Terk HDTVi, even without amplification. And the amplification is useful for the 100 ft run of coax.
 
#13
I wasn't sure on terminology. The antenna has a lenght of coax coming out of it (say 6 feet) and also came with seperate small box connected to a power supply with two coax connectors, one male & one female. So it is possible to completely remove the amplifier from that antenna. Now that may have a negative impact on the antenna, I was just letting you all know I had tried it both ways.

I do use a flat coax to go under a window to enter the condo. The total cable lenght is broken up by a few different cables (I know this is not ideal).

Antenna is level & away from metal.

I've give your rabbit ear suggestion a try, but seeing as this setup has worked for a couple of years I can't see that suddenly being the problem. I wondered if it was the fact that I was using an antenna made for indoor use outside (even if covered/not getting wet) but again why would just a couple of channels drop off?

I'll either report back or give a different antenna a try. Again I appreciate the feedback.
I would suggest that you replace the flat cable.

Whenever I install a flat cable, I leave a replacement and tell people to check it first (in about a year) when something goes wrong.

Otherwise, I think you may have just come to the end of the life-cycle of your antenna.

"Why would just a couple of channels drop out?"

Electronic components and cabling in digital systems will often fail partially, at first. Every error indication that you have is evidence of the beginning of failure to come. These things don't die like vacuum tubes used to. Splitters and switches, satellite LNB's, diplexers, and connections can all fail "partially" and still work. Their work is passing signal as information, not passing electricity as a path. Here we are concerned with partial failure to pass a signal. The failure to pass a portion of a signal (certain wavelengths or frequencies are lost) leading to loss of channels, or with satellite, loss of transponders.

Partial failure of these components is "typical" behavior in digital systems.
 

Columbo

DTVUSA Jr. Member
#14
I wanted to come back and follow up with what ended up being the solution to my problem. Before I do though one last thank you to everyone who commented and offered support. I very much appreciate all of the replies.

My plan was to replace the flat cable running under the window first, but when I went to see if Monoprice had one for sale (I had to buy and HDMI cable for another system) I noticed they sold an indoor/outdoor antenna that was less than $25. I've had great luck with Monoprice and the reviews were good so I gave it a try (Antenna link).

I used the same coax setup with the new antenna and everything works just as good as before, so it looks like my old HDTVa was the problem. Getting 2+ years out of these antennas is an acceptable cost to me over having cable.

Thanks again everyone.
 

FOX TV

Contributor
#15
Here is an interesting discovery I made last Sunday. I built a new antenna (UHF DB-4 knockoff) and it was actually receiving channel 13 VHF with a 2 edge path at 30 miles away. I proceeded to hook up a stream analyzer to my laptop, and as soon as I hit the power switch on the laptop, I lost the channel 13 signal. I shutdown the computer, and as soon as the power LED went dark, the channel 13 signal immediately came back. I re-started the laptop, and again, as soon as the power button was pushed, the channel 13 signal immediately went away again.

The power supply for the laptop was hooked up to the same power strip as the DTV, which is an Emerson 19" with a built in DVD player that I bought just before Christmas. The power supply has a ferrite coil trap built into the power cord, so I don't expect that RF through the power cord is the culprit here, as the same results were seen when running the laptop on batteries. The wireless card was turned off at the time too, and the laptop was located almost 10 feet away from the DTV.

The signal level of the channel 13 signal was obviously not very strong as it was being received on a UHF antenna, and my suspicion is that RF from the computer was the cause of this issue. This just goes to show how some reception problems are a big mystery, and how solving them on a forum like this one may not always produce results that are satisfactory to the user due to circumstances such as this one.

There are many possibilities such as this one that can cause loss of a single or multiple channels that you could previously receive. This could be especially troublesome for apartment or townhouse dwellers, as you have no idea of what other potential sources of interference may be coming from the other side of the wall in an adjacent apartment or townhouse, or what type of new interference sources that may spring up out of nowhere in the complex.
 
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#16
That's right, FOXTV.

Microwave ovens, wireless routing, police radar, and sometimes even a cell phone can cause loss of a single transponder or channel with satellite.

I'm not sure how many of these affect both satellite and DTV, though.



Or did we just jump off topic?
 
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