Who knows about digital broadcasting?

All of our digital channels are receiving good signal, except one. I have tried everything and finally found that if I disconnect the coax and insert only the center core, leaving the shield unconnected, I receive that one channel perfectly - but I loose all other channels. As soon as I connect the shield I loose that one channel and gain all the others. What gives?

It’s just the RF, nothing to do with digital signals.

It could be that the one signal is too strong and is overloading the input of the receiver. Just connecting the centre connector gives you less signal hence the front end is not being overloaded. Try inserting a 3dB attenuator in the antenna or adjust the direction it is pointing.

If it is a TV signal then it won’t be just one channel that is affected but most likely the entire multiplex which could carry up to 5 TV channels.

Makes sense, I’ll try that - thanks

EDIT
I tried moveing the ant,(roof top) but no luck.

The other thing that could be a problem is interference from a near by transmitter being picked up on the outer braid of the coax. This can be cured with braid breaker.

Google it or see:-
http://www.ukradioamateur.co.uk/full/html/c9-1-3.htm

EDIT
I have use the one at the bottom of this page:-
http://www.vwlowen.co.uk/radio/radtech.htm
Just with a small piece of pcb material and two saw cuts through the copper. It completely cured the RFI I was causing.

Well thanks for your suggestions, but no dice.

This is what I have tried.

3db Attenuator
5db Attenuator
DC Block
FM Trap
RF Filter
Noise Filter
Ground loop Isolator
Amplifier both with and without a DC block and FM trap
Braid breaker
Rotated the ant in 3 degree steps a full 360 degrees (this made all other channels get worse)
Indoor antenna
EMI Filter

Only thing that works: Remove the shield on the coax OR a 24awg wire about 10’ long stuck in the center of the connector and draped across the furniture. When the sheild is connected, I get 0 on the signal meter for this channel, absolutly no signal. With just the center connects I get at least a 50%. Most of the above things I have tried had none or very little effect on anything.

I guess I will just rig up a switch to disconnect the sheild. Unfortanatly, this one channel is about the only channel we watch. FOX network.

Sounds like you are trying to pick up a VHF channel with an ill-suited antenna. MOST channels will switch to UHF after the switchover, but some may not. Most all “HDTV” antennas are UHF only (They can be built smaller) and cannot receive VHF channels. VHF can be picked up with a bare wire in a pinch, but sadly, will all but dissappear from the airwaves in June. I suggest visiting TVFool.com for more complete information about your situation.

Thanks, I’ll check it out but this don’t appear to be the issue. My antenna is a UHF/VHF roof top, about 25’ in the air.

Once is a great while, I can receive this channel normally, but more often than not it won’t come in. If push comes to shove I will simply insert a switch on the shield and flip the d*m switch.

very annoying. :-/

I am talking to Solid Signal about the issue as well, so hopefully they can come up with something.

MOST channels will switch to UHF after the switchover, but some may not

Sorry this is just wrong. There is no change to any VHF broadcasts with digital changeover.

Most all “HDTV” antennas are UHF only

This is again rubbish. There is no such thing as a HDTV antenna as there is no terrestrial HTV transmissions in the UK at the moment.

VHF can be picked up with a bare wire in a pinch, but sadly, will all but dissappear from the airwaves in June.

RUBBISH VHF is NOT going to be affected by analogue turn off.

Well, I just got my 0-20 db attenuator and no luck. There was absolutely to change on this one channel in question. It did affect the other channels a little bit.

So I guess it back to the ol’ switch to open the shield. I think I can hook it up to Ir as well so when I tune to this channel it will automatically open the switch.

Thanks for you suggestions.

It appears that the one with the most posts is deemed the smartest.

That’s too bad. I have a bit of experience with this, but I’m in the US not in the UK.

Good luck with the advice you get.

It appears that the one with the most posts is deemed the smartest.

No not at all.

I have a bit of experience with this,

So have I, like I work in digital TV designing set to boxes, started over 10 years ago. I designed one of the set top boxes that OnDigital gave away with their subscription back in 98. OnDigital were the worlds first digital terrestrial TV company. I attended the House of Commons lobby for analogue switch off in 2002. Plus I have been a radio ham since 1973 and even transmitted amateur TV.

but I’m in the US not in the UK.

So check the location of the person asking the question or state in your answer that you are in the U.S.

Jasper.
What is the channel you are having trouble with and what transmitter are you taking the signals off?

Jasper.
What is the channel you are having trouble with and what transmitter are you taking the signals off?

The channel in question is Fox Network, local channel 28.1, which is actually 58.4, UHF I believe. The transmitter is ~10 miles to the south west

WSJV-DT (Digital)
Channel: 28 (28.1)
Network: Fox
Maximum ERP: 250.000 kW
Coordinates: 41.616160 -86.193893

This transmitter is also the closest to my location, so it may very well be over driving the receiver. I would have thought that the 20db aten would have shown something but it didn’t. The signal simply isn’t there unless I break the shield.

So now I am investigating an auto switch, something that can determine the best signal from 2 or more sources (antennas) and switch to the best one.

Not wishing to be rude Grumpy_Mike, but are you sure he’s in the UK?

Coordinates: 41.616160 -86.193893

Andrew

Well that is quite a bit of power quite close, I am not sure if 20dB is enough for your front end. It could be that you might need 40 or even 50dB. It depends on the intermodulation performance of the front end of your set top box.
If you get a 30dB attenuator you could always try the two in series. However with that sort of power difference between transmitters you might have a problem you can’t easily solve.

Not wishing to be rude Grumpy_Mike, but are you sure he’s in the UK

No - my bad, he is not although I thought he was from reading other threads.

It looks like he is not so I apologise unreservedly to honda_bot, and conceded that he knows about the VHF moves in the U.S. :-[

Nope, not in the UK, although about 80% of my roots come from the Great Britten, and if our current reigning “King” don’t keep his nose out of my business, I may be heading back there. :-X

The radar plot of your area (supplied by www.tvfool.com) based on the information you supplied, shows no remarkable differences between that channel and others. See it:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3D577305bea93dd4

Before spending any more money, I’d start ruling stuff out. Take your TV up as close to the antenna as possible and use as short a cable as possible to hook it directly from antenna to TV. I recommend a different cable than what is already there in order to rule the original cable out. See what you get. If you still don’t get it, it could be your antenna or your TV. Most likely it’s not your TV, but it is possible. Try it w/different TV. Adjust your antenna using a compass. inspect your antenna, too. If your antenna is bent or damaged, it’s possible that it may have a dip in responsiveness to that frequency or direction. Try rabbit ears. (you should be able to pick up your stations w/ rabbit ears based on your radar plot.) If you do get that station, then connect your tv at every joint in the cable down to your original TV location. Then you can determine what cable/splitter/amplifier is bad. If your TV or Converter box has a signal display or SNR, pay close attention to that at each step.

Also, remove any unused splitters that you may have. Each splitter attenuates your signal by more than half. It’s possible that there’s just not enough signal at your TV to get that channel.

good luck

The radar plot of your area (supplied by www.tvfool.com) based on the information you supplied, shows no remarkable differences between that channel and others. See it:

Yes, I already looked at that - that is where I got the above info, thanks for the link.

Before spending any more money, I’d start ruling stuff out. Take your TV up as close to the antenna as possible and use as short a cable as possible to hook it directly from antenna to TV.

I don’t think I am going to carry a 90lb TV to my roof top :wink:
or lug it around to other location in my hose.

I recommend a different cable than what is already there in order to rule the original cable out.

Already tried.

If you still don’t get it, it could be your antenna or your TV.

It’s not the antenna, and it’s not the TV. If anything it is the cheap a** converter boxes. I have one on 3 TVs, exact same results on each.

Adjust your antenna using a compass. inspect your antenna, too. If your antenna is bent or damaged, it’s possible that it may have a dip in responsiveness to that frequency or direction.

No damage and I have already moved the ant in 3 degree increments for a full 360. If I get the time, I will try it again in only 1 degree.

Try rabbit ears. (you should be able to pick up your stations w/ rabbit ears based on your radar plot.) If you do get that station, then connect your tv at every joint in the cable down to your original TV location. Then you can determine what cable/splitter/amplifier is bad. If your TV or Converter box has a signal display or SNR, pay close attention to that at each step.

I would assume an indoor ant would work, as the 10’ wire works laying across the floor, but the wire won’t pick up the other stations except 1, which btw is the next closest trasmitter and rabit ears won’t do me anygood for my basment TV.

The converter box does have a signal meter. With the normal ant the signal is 0. With my wire on the floor the signal is about 50. I don’t beleive a wire on the floor is going to pick up a weak signal better than my roof top ant even if it was damaged.

Also, remove any unused splitters that you may have. Each splitter attenuates your signal by more than half. It’s possible that there’s just not enough signal at your TV to get that channel.

Well I agree that splitters attenuate the signal, but I wouldn’t say by half. I only have 1, 3-way splitter anyways and I already by-passed that.

Let me give a bit more background. Before Feb 17th, 28.1 was broadcast in both analog and digital. At that time I could receive both just fine. once in a great while, I would loose 28.1 for maybe a day or two, but it would come back. After Feb 17th 28.1 was only broadcast in digital, since then I could no longer receive the channel. It’s possible that they were not broadcasting at full power before the switch.

I talked to the techs at the station, but they pretty much said it is my problem and didn’t really offer any resolution.

Thanks for your suggestions, it gave me a few other ideas for things to check out anyways.

What about a stopband filter to attenuate that specific freq?

I don’t know your specific situation, but I don’t think you want to attenuate anything, unless you know specifically that your input is being overloaded. BTW, any time you add something that says
-X.xdB (a splitter or attenuator) it “muffles” the signal. Without a long explanation about dB, any time you lose 3 dB from input to output, you halve the signal. So, for instance, your 20dB attenuator divides your input by 20/3=6.6 times. In other words, your signal is now 1/6.6 of the original. You noticed it because you probably lost some other channels because their input was now too low to display.
It could also be your cheap converter box. cheap electronics make for those cheap converter boxes.

You could theoretically do everything I oulined above with your CB (instead of your 90lb TV) and send it down the cable to your TV. But that won’t expose any frequency problems with the cable.

I suggest contacting www.dennysantennaservice.com for more help. This guy really knows his stuff. He’s solved some really tough problems, and he offers help to casual e-mailers, too.

I would also suggest talking to your nieghbors, see what channels they get.

Edited for wrong maths

I would also suggest talking to your nieghbors, see what channels they get.

All my neighbors have Satellite or cable, so they don’t care. ;D
I’m probably the only one in a 50 mile radius that refuses to pay for commercials.