Since having digital tv/phone/roadrunner installed I'm experiencing buzz on AM & SW bands on both unused and some used freqs with low signal strengths. Makes DX'ing almost impossible. It seems to be akin to what one would may find from BPL, from what I've read. Is this a common problem with digital tv? The installers ran the cable from the utility pole to my tower where other antannas are installed then inside. What sort of shielding could I use?
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AM Interference
- Thread starter WCJ
- Start date
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WCJ said:
Roadrunner and other Cable internet modems use 26.xx MHz for the upstream from your PC and 633+ MHZ for the downstream TO your PC...if the shield is open anywhere, your modem will lose connection or be EXTREMELY slow in uploading, requests, etc.....the power out level is usually +55dbv into the cable.
But I have not had any issues with cable internet.....The digital TV is likely another issue (and I have been on Dish for 6+ years....I HATE cable TV choices and pricing)....I have DSL with Vonage at the house...no problems here on HF or VHF.....AM is pretty well quiet too except for one table top clock radio...which sits next to my 5.6GHz cordless phone...but not sure if thats the cause.
As for shielding? Any good quality shielding should always be used...likely I would not have let them tie to a tower...
this makes a good lightning path!...you need to have them move it away from your tower/antennas...besides, any such system is NOT supposed to radiate (you think this is bad, you HAVENT heard BPL yet!).
You must get the cable off your tower. There is no shielding effective enough to run it that way.
Digital goons have NO respect for the delicacy of weak analog signals.
THEY should pay for the move, as they installed it in opposition to all rules of good engineering.
Keep all digital sources well removed from all RF as they are totally dissimilar and the analog always loses out.
My rental car this week in Des Moines must have the engine turned off to remove 15db of digital noise in order to hear otherwise perfectly readable daytime 50kw Chicago AMs. It's not ignition noise, it's engine controls or the DC armature motor for the fuel pump.
The first thing I did when moving to my house was remove all cable TV wiring and call the cable company to come remove the drop from the pole before I yanked it off myself. I will not permit such sloppy engineering to ruin my radio reception. And this was 1993, with analog cable.
I'm sure any digital service will be even noisier. BPL is the textbook example for "they don't get it".
Digital goons have NO respect for the delicacy of weak analog signals.
THEY should pay for the move, as they installed it in opposition to all rules of good engineering.
Keep all digital sources well removed from all RF as they are totally dissimilar and the analog always loses out.
My rental car this week in Des Moines must have the engine turned off to remove 15db of digital noise in order to hear otherwise perfectly readable daytime 50kw Chicago AMs. It's not ignition noise, it's engine controls or the DC armature motor for the fuel pump.
The first thing I did when moving to my house was remove all cable TV wiring and call the cable company to come remove the drop from the pole before I yanked it off myself. I will not permit such sloppy engineering to ruin my radio reception. And this was 1993, with analog cable.
I'm sure any digital service will be even noisier. BPL is the textbook example for "they don't get it".
Not to totally hijack the thread but does a DSL installation cause the kind of interference the OP is describing?
I've got that same kind of noise here at a house. There's tons of birdies over AM and SW, and some I know for sure are coming from the DSL modem because the sounds correspond (!) to data being handled by the modem.
Funny thing is, I can unplug the router and modem and the interference is still there but the "noises" are gone.
When I first moved in about 7 months ago, the FM band was almost completely dead, as was the VHF-Lo TV band... Even the few local FM's had a heavy layer of static on them. (These are class A's about 10 miles out over gentle rolling terrain.) There are some distant TV stations on 2, 4 and 6 that were just *dead* anywhere in the neighborhood...
Now, the FM band is better but by no means "normal" because once I leave the neighborhood the FM reception in a car gets much better...
It's a mystery to me.
The AM/SW problem bothers me, especially. There's actually a few decent AM's around but they're all in other cities. The closest AM to me here in Grenada is a 1kW non-D that's 27 miles away; the strongest on the dial is a 50kW non-D in Memphis, 82 miles away.
I've got that same kind of noise here at a house. There's tons of birdies over AM and SW, and some I know for sure are coming from the DSL modem because the sounds correspond (!) to data being handled by the modem.
Funny thing is, I can unplug the router and modem and the interference is still there but the "noises" are gone.
When I first moved in about 7 months ago, the FM band was almost completely dead, as was the VHF-Lo TV band... Even the few local FM's had a heavy layer of static on them. (These are class A's about 10 miles out over gentle rolling terrain.) There are some distant TV stations on 2, 4 and 6 that were just *dead* anywhere in the neighborhood...
Now, the FM band is better but by no means "normal" because once I leave the neighborhood the FM reception in a car gets much better...
It's a mystery to me.
The AM/SW problem bothers me, especially. There's actually a few decent AM's around but they're all in other cities. The closest AM to me here in Grenada is a 1kW non-D that's 27 miles away; the strongest on the dial is a 50kW non-D in Memphis, 82 miles away.
BPL is a possibility but I don't know where the trials are going on. Could also be straight 'power line' interference from a bad transformer or insulator. Easiest thing to do (except for resetting the clocks) is to take a battery operated portable radio, tune it for the maximum noise, shut off the main breaker to the house, and see if the problem goes away. If it goes away, then it is in the houseand you need to track it down (one breaker at a time). If it doesn't, rotate the portable and see if you can directionalize it.
The 'DSL' noise may be coming from the computer and not from the modem or router.
I live in a stucco house and can see the FM and TV transmitters. But I can't get any reception at all inside the house thanks to the chicken wire and cement making up the stucco. Is there a nearby broadcast transmitter, cell phone tower, or some other transmitter. Otherwise, it may be house construction (like mine) or you are down in a hollow as far as FM and TV goes.
John
The 'DSL' noise may be coming from the computer and not from the modem or router.
I live in a stucco house and can see the FM and TV transmitters. But I can't get any reception at all inside the house thanks to the chicken wire and cement making up the stucco. Is there a nearby broadcast transmitter, cell phone tower, or some other transmitter. Otherwise, it may be house construction (like mine) or you are down in a hollow as far as FM and TV goes.
John
John I checked around and it appears that there is no BPL trials going on here.
I've cut the power to the house before and the noises are still there. I am thinking the FM/VHF interference is actually coming from a power transformer. The utilities are all underground here but there's a power box right in my front yard. And lo, that's where the interference is strongest.
The AM/SW noise is present even with the entire house power cut. I hadn't thought of it before, but I realize there's an alarm system installed - with built in UPS. Perhaps it's the alarm causing the problem? There's no way I know of to disconnect it completely from a power source.
As for nearby transmitters... The city/county services are on a tower about one mile east of here, but I doubt that's a source; there's a local 2m repeater there as well that never gets used.
(BTW, KE4OYN here - long time licensee but I rarely have used it.)
There's a combo GSM/CDMA cell tower 3/4 mile from here as well...
I'll get my portable out and do some playing and see what I can come up with.
I've cut the power to the house before and the noises are still there. I am thinking the FM/VHF interference is actually coming from a power transformer. The utilities are all underground here but there's a power box right in my front yard. And lo, that's where the interference is strongest.
The AM/SW noise is present even with the entire house power cut. I hadn't thought of it before, but I realize there's an alarm system installed - with built in UPS. Perhaps it's the alarm causing the problem? There's no way I know of to disconnect it completely from a power source.
As for nearby transmitters... The city/county services are on a tower about one mile east of here, but I doubt that's a source; there's a local 2m repeater there as well that never gets used.
(BTW, KE4OYN here - long time licensee but I rarely have used it.)There's a combo GSM/CDMA cell tower 3/4 mile from here as well...
I'll get my portable out and do some playing and see what I can come up with.
So there is nothing around with repsect to transmitters that would cause 'de-sensitization' of the front end. You may just be a victim of geography.
If you are getting VHF/FM interference form the box outside, I'll bet the box is also carrying the TV cable signals and you have some leakage there. Tell the cable company and they will generally come out and fix it.
Sources of AM interference are flourescent lights. video/FM amplifiers, wall chargers, power lines (especially in a dry climate), and some street lights.
The alarm system you can check by holding the radio next to the box.
You can also try to use the directivity of the ferrite loop inside the radio to narrow down the direction.
BTW, effective Friday (the 23rd), morse code disappears as a requirement for General and Extra So if you want to try HF, then all you need to do is pass the written.
If you are getting VHF/FM interference form the box outside, I'll bet the box is also carrying the TV cable signals and you have some leakage there. Tell the cable company and they will generally come out and fix it.
Sources of AM interference are flourescent lights. video/FM amplifiers, wall chargers, power lines (especially in a dry climate), and some street lights.
The alarm system you can check by holding the radio next to the box.
You can also try to use the directivity of the ferrite loop inside the radio to narrow down the direction.
BTW, effective Friday (the 23rd), morse code disappears as a requirement for General and Extra
So if you want to try HF, then all you need to do is pass the written.Wow I never thought morse would be dropped as a requirement to get on HF! I'm not sure that's a good thing or a bad thing.
I'm beginning to think it's geography that's affecting the TV channels, but everything else seems to be inside the house. This area is a nice flat plain surrounded on almost all sides by gentle rolling hills.
It appears that some of the noise, especially on the SW bands has been eliminated. Dunno why, but I'm not complaining.
The alarm seems to be affecting FM reception, but only on this side of the house. On the opposite side of the house, the wireless router is definitely affecting FM and AM reception. I shut it and the DSL modem off and all the sudden what was full-signal static was a nearly full-quieting C1 FM from 78 miles off. (WQJQ - I'm in Grenada, at the top of the map - not exactly in their primary service contour.)
Luckily, the major sources of AM interference that you listed aren't in use in the house...
As for the alarm, I noticed for the first time today that there's a smaller box next to the main unit (where the siren is) with two antennae on top. Hmm. Time to start snooping. SW reception got much much better when I placed the radio next to the boxes. Must be a long wire run near there.
The cable company has an underground box next to the transformer box, but there's no run to this house or either next door neighbor - we're all on satellite.
So, it appears that most of problems have resolved themselves... At least now if I get desperate for some FM DX I can just shut off the router (and all the computers), go outside and have at it.
I'm beginning to think it's geography that's affecting the TV channels, but everything else seems to be inside the house. This area is a nice flat plain surrounded on almost all sides by gentle rolling hills.
It appears that some of the noise, especially on the SW bands has been eliminated. Dunno why, but I'm not complaining.
The alarm seems to be affecting FM reception, but only on this side of the house. On the opposite side of the house, the wireless router is definitely affecting FM and AM reception. I shut it and the DSL modem off and all the sudden what was full-signal static was a nearly full-quieting C1 FM from 78 miles off. (WQJQ - I'm in Grenada, at the top of the map - not exactly in their primary service contour.)
Luckily, the major sources of AM interference that you listed aren't in use in the house...
As for the alarm, I noticed for the first time today that there's a smaller box next to the main unit (where the siren is) with two antennae on top. Hmm. Time to start snooping.
SW reception got much much better when I placed the radio next to the boxes. Must be a long wire run near there.The cable company has an underground box next to the transformer box, but there's no run to this house or either next door neighbor - we're all on satellite.
So, it appears that most of problems have resolved themselves... At least now if I get desperate for some FM DX I can just shut off the router (and all the computers), go outside and have at it.
An outside FM Yagi, a rotor, and a coax feed line (to reduce noise from inside the house). That is what I used when I lived in the boonies and it was 40 miles (over hilly terain) to the nearest FM worth listening to. I could reliably listen 100+ miles (depending on the station). Antenna height is everything on FM.
John
John
Replaced the $39 PC power supply with a name-brand $79 supply and 99% of the RF interferance went away. Could hear the cheap supply on the car radio a block away, even when it was on standby.
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