I'm picking up CB radio on my amp. I did a search and found everything from "replace all tubes IMMEDIATELY or your amp will fry" to "Don't worry about it, it's common"
So, is it anything to worry about? If I don't have the ends of my interconnects plugged in to my preamp or dac I pick up very faint radio. As soon as a cable is plugged in to a grounded preamp, the slight radio noise goes away.
This CB radio comes in LOUD over the top of the music I'm listening to, but it's probably someone nearby w/ a little too much power in their CB tx.
This is in a pair of Ampex 620 monoblocks, which are 6v6 P.P.
thanks!
So, is it anything to worry about? If I don't have the ends of my interconnects plugged in to my preamp or dac I pick up very faint radio. As soon as a cable is plugged in to a grounded preamp, the slight radio noise goes away.
This CB radio comes in LOUD over the top of the music I'm listening to, but it's probably someone nearby w/ a little too much power in their CB tx.
This is in a pair of Ampex 620 monoblocks, which are 6v6 P.P.
thanks!
wicked1 said:
That is not good. The only way you could be hearing that radio is by means of detection. Detection means nonlinear. One or more stages of that amp are running in a nonlinear manner, and that's not helping the sonics one little bit. It could be a weak tube that's slipped towards cutoff enough to be functioning as a "plate detector", or it could just mean that the rig is close enough to be driving one or more stages into clipping. (In which case, a call to the FCC might be in order, but given the sad state of that ineffectual bureaucracy, the needle in the coax might get faster results.)
If it's coming in loud, then I'd take a look at the earliest stages for the fault. The detection is occurring up front and receiving substantial amplification.
Once I heard a CB radio on the public address system at LAX.
My cousin, who is into CB's uses those illegal CB boosters (don't know what they are called) and when he is parked in front of my house (when I still reside in Los Angeles), his CB conversation gets into my TV and into my audio equipment!
My cousin, who is into CB's uses those illegal CB boosters (don't know what they are called) and when he is parked in front of my house (when I still reside in Los Angeles), his CB conversation gets into my TV and into my audio equipment!
alexg said:My cousin, who is into CB's uses those illegal CB boosters (don't know what they are called) and when he is parked in front of my house (when I still reside in Los Angeles), his CB conversation gets into my TV and into my audio equipment!
They're called "linears", and most of the illegal ones (the FCC requires legit manufacturers of ham rigs to eliminate the possibility of retuning to the 11M band) are designed very badly. That's where your TV interferance comes from. Most of the VT-based designs eat tubes like corn flakes, which is why otherwise good audio finals like 6LW6s are so expen$ive. That's where all the NOS went since the big CB craze of the 1970s.
Hey Wicked,
If you live very close to a major highway then you are pretty much left with trying to correct the problem within your amp. You cant stop all the truckers as a lot of them still run high power "linears". Now if you have a bucketmouth neighbor that is running illegal power just drop him a nice letter stating that you have recorded his conversation and if he doesn't stop you will submit the recorded proof to the FCC, that usually works. Trust me, I know as I have been on both ends of that issue. There is also the chance the guy may well be running within the legal limit of 4 watts but from some reason his CB is "washing" really bad. Washing meaning scattering stray unwanted RF.
If you live very close to a major highway then you are pretty much left with trying to correct the problem within your amp. You cant stop all the truckers as a lot of them still run high power "linears". Now if you have a bucketmouth neighbor that is running illegal power just drop him a nice letter stating that you have recorded his conversation and if he doesn't stop you will submit the recorded proof to the FCC, that usually works. Trust me, I know as I have been on both ends of that issue. There is also the chance the guy may well be running within the legal limit of 4 watts but from some reason his CB is "washing" really bad. Washing meaning scattering stray unwanted RF.
DaveInVA said:I found the only way that really works in keeping out those pesky cabbage banders is to find the offending CB'er and push needles through his ant coax and cut the ends of the needles off. That will stop the interference...
Dave
I prefer putting the needles through the eyes.
I have nothing against ham freaks but morons causing problems with powerful hardware they installed just because they think it's cool need to be punished.
They are one step up from the idiots who shine laser pointers at landing aircraft.
If you are getting interference from an amateur radio operator they are almost always genuinely sorry for the trouble and will do what they can to stop the problem.
Shielded RCA cables will help. I figure they are a coaxial plug so you should use a coaxial cable. Many, many low and high end RCA cables aren't screened.
wicked1 said:
The easiest place for RF to get into your amp is the speaker leads acting as an antenna. A quarter wavelength at 11 meters is about 9 feet, so this length and multiples thereof should be avoided, and try to keep the speaker leads horizontally polarized rather than vertical, if your problem is in fact a CB'er.
A good start would be to try shielded speaker leads if your amp permits the shield to be grounded, and if that does not work, work backwards into the last stage of the amp looking for bad grounds, bad solder joints, etc., anything that can act as a rectifier.
Your statement that you also pick up RF with the line inputs open troubles me, but that's probably an unrelated problem to be fixed after you fix the CB problem.
Good luck,
Win W5JAG
Another thing that occurs to me is that, if this is a "vintage" amp, one of the first things I do to any old piece of gear is to break loose EVERY ground conection in the device - tube sockets, terminal strips, I mean EVERYTHING, and put a drop of a good contact cleaner like DeOxit D5 between the chassis and whatever is fastened to it before it's tightened back up.
Flaky grounds can cause a lot of problems, and it's well within the realm of probablity that this can help your problem.
Win W5JAG
Flaky grounds can cause a lot of problems, and it's well within the realm of probablity that this can help your problem.
Win W5JAG
I agree with w5jag.... Many times your speaker wires act as an antenna. Then the signal is coupled into the chassis and detected in one of the low-level audio circuits. It may be as easy as going to your local parts supplier (Radio Shack, etc.) and buying a couple of .01uf 100V capacitors. Connect one across EACH speaker pair right at the amplifier (where the speaker leads attach to the amp). If that's where the signal is getting in, the caps will act as a bypass and effectively "short out" the interference. The low value will have no effect on your sound, however. Good luck.
r221b
r221b
Thanks everyone!
Yah, my speaker wires are fairly long, and I have about 6' of interconnect between my pre and amp. The interconnects are actually just some rj45 twisted pair that I threw some RCA ends on. I guess all of that will act as an antenna.
The general RF I get when my interconnects aren't connected to my preamp is very quiet (gotta have my ear up to the speaker), and goes away as soon as they're plugged in, so I'm not too worried about that.
I hear the CB each morning.. It almost sounds like a dispatch talking to their drivers. I'll drive around and see what I can find. I do live a few blocks from a highway, but I don't pick up general CB traffic all day long.
I used to know a guy about 15 years ago who was a trucker, and he had a very illegal system. His antenna would arc if you held a ground wire close enough to it. He was quite proud of the fact he could drive up to your house and have his signal come through on any electronic device you had. He even purposely added something so that his signal did spread across the entire CB spectrum (and probably beyond)
I think that guys in jail now for other reasons.
Yah, my speaker wires are fairly long, and I have about 6' of interconnect between my pre and amp. The interconnects are actually just some rj45 twisted pair that I threw some RCA ends on. I guess all of that will act as an antenna.
The general RF I get when my interconnects aren't connected to my preamp is very quiet (gotta have my ear up to the speaker), and goes away as soon as they're plugged in, so I'm not too worried about that.
I hear the CB each morning.. It almost sounds like a dispatch talking to their drivers. I'll drive around and see what I can find. I do live a few blocks from a highway, but I don't pick up general CB traffic all day long.
I used to know a guy about 15 years ago who was a trucker, and he had a very illegal system. His antenna would arc if you held a ground wire close enough to it. He was quite proud of the fact he could drive up to your house and have his signal come through on any electronic device you had. He even purposely added something so that his signal did spread across the entire CB spectrum (and probably beyond)
I think that guys in jail now for other reasons.
When I was a student of Tomsk Institute of Automatic Control Systems and Radio Electronics there was a collective amateur station on the highest floor of our campus building. Though it was completely legal, during contests guys used illegal power, so electric bulbs dimmed in tact with their speech in all 9 - store building.
All turntables and tape players detected their signals that sounded horrible because they used SSB modulation.
It was the time when students practically learned to shield their gear, implement RF filtering, to plan grounds properly, but nothing helped to silence that "music" enough.
Once I've found a solution. I borrowed a vinyl disk of new Santana concert (it was 1978?), but suddenly guys started to transmit their horrible waves from the roof!!!
I took a tunnel diode, a 2-base transistor, one varactor, few resistors, couple of capacitors, quickly made a coil on a pencil, connected 9V battery, put everything in a slipper, connected one wire to a central heating battery (ground), another one to a metal frame of my bed (antenna). Turned on a shortwave radio and adjusted a coil on a pencil so my thingy generated frequency modulated signal over all 3.5 MHz ham band. It contained lot of harmonics so all bands (7, 14, 21, 28 MHz) contained a horrible loud continuous "beep".
They stopped soon since did not hear responses... I enjoyed a music when my friend who participated in the ham activity come to the room, sat down starting some unnecessary conversation, looking around as if he was searching for something... He could not expect that the jammer was hidden in one of slippers under my bed...
In your particular case I would call FCC and complain; no doubt your neighbour uses illegal power to transmit.
All turntables and tape players detected their signals that sounded horrible because they used SSB modulation.
It was the time when students practically learned to shield their gear, implement RF filtering, to plan grounds properly, but nothing helped to silence that "music" enough.
Once I've found a solution. I borrowed a vinyl disk of new Santana concert (it was 1978?), but suddenly guys started to transmit their horrible waves from the roof!!!
I took a tunnel diode, a 2-base transistor, one varactor, few resistors, couple of capacitors, quickly made a coil on a pencil, connected 9V battery, put everything in a slipper, connected one wire to a central heating battery (ground), another one to a metal frame of my bed (antenna). Turned on a shortwave radio and adjusted a coil on a pencil so my thingy generated frequency modulated signal over all 3.5 MHz ham band. It contained lot of harmonics so all bands (7, 14, 21, 28 MHz) contained a horrible loud continuous "beep".
They stopped soon since did not hear responses... I enjoyed a music when my friend who participated in the ham activity come to the room, sat down starting some unnecessary conversation, looking around as if he was searching for something... He could not expect that the jammer was hidden in one of slippers under my bed...
In your particular case I would call FCC and complain; no doubt your neighbour uses illegal power to transmit.
I hate to say it but the FCC isn't really doing much these days. Unless the person is interfering with tv or radio they won't do allot with just a couple complants.
The man power of the fcc isn't what it used to be. There are plenty of UHF tv station breacking the law by going over 4megawatts E.R.P. and they don't do anything, but it's clean though.
I know a pretty high up guy in the fcc back in Houston and he was the only guy in Texas. And I don't see them hiring more people.
Unless your guy was causing alot of tvi problems and people started calling the station would the fcc get involved.
And ebven then it would only be 1 guy and a few us marshalls usually.
Good luck
The man power of the fcc isn't what it used to be. There are plenty of UHF tv station breacking the law by going over 4megawatts E.R.P. and they don't do anything, but it's clean though.
I know a pretty high up guy in the fcc back in Houston and he was the only guy in Texas. And I don't see them hiring more people.
Unless your guy was causing alot of tvi problems and people started calling the station would the fcc get involved.
And ebven then it would only be 1 guy and a few us marshalls usually.
Good luck
Yeah,
I'm not that worried about it, and I avoid getting authorities involved unless I really really really have to. I just wanted to make sure it wasn't a problem w/ my amp. If it was all day long, I might start to get upset, but this is just for a while in the morning. Maybe it's how this guy keeps in contact w/ some of his buddies.
I'm not that worried about it, and I avoid getting authorities involved unless I really really really have to. I just wanted to make sure it wasn't a problem w/ my amp. If it was all day long, I might start to get upset, but this is just for a while in the morning. Maybe it's how this guy keeps in contact w/ some of his buddies.
If it sounds like a dispatcher, and is only in the morning, it may not be CB but a licenced operator on a commercial band in a business nearby.
you should be able to work out what type of business after a few days of listening. Even so the easiest thing is to start with protecting your own equipment. The business won't care much. You can get some weird and wonderful things from corroded structural connections on towers.
Fortunately our FCC equivalent here is quite good. Though my experiences with them are as a tech lodging a complaint, not the general public. I remember a guy was jailed for 2 years for causing confusion by talking on an aviation band at a major airport.
you should be able to work out what type of business after a few days of listening. Even so the easiest thing is to start with protecting your own equipment. The business won't care much. You can get some weird and wonderful things from corroded structural connections on towers.
Fortunately our FCC equivalent here is quite good. Though my experiences with them are as a tech lodging a complaint, not the general public. I remember a guy was jailed for 2 years for causing confusion by talking on an aviation band at a major airport.
Hello Wicked1, I woudn't expect too much from the FCC. I had a similar problem with a neighbor (never did figure out where) about 15 years ago. I called the FCC, all they did was send me a little booklet with ways to reduce the interference on the end that is receiving the interference. Unless you have a lot of money, i.e. you are a major political contributor, you won't get much out of any government agency.
The suggestions that others have had, using coax for your low level signal cables, adjusting the length of your speaker wires, using shielded wires for your speakers all may help. Another is to use twisted pair wire for your speaker cables. If the speakers cables are acting as antennae, then the offending signal should be on both leads to the speaker. Twisted pairs tend to reject common mode interference like this. You also may want to go through your amp and clean up solder joints, as was suggested earlier. If at all possible, it may be worth trying to adjust the circuit design so that all of the grounds come together at a single point, aka a star ground. Also, install a grounded power cable and have the ground wire attached to the metal chassis, near the star ground, but not on the same screw. Grounding the chassis will use the metal as a Faraday cage to channel RF signals that may get into the chassis to ground.
If you find out who the offender is, the needle trick does sound effective, but make sure you don't leave behind any evidence; fingerprints, etc. Then the cops can get you for destruction of property.
Peace,
Dave
The suggestions that others have had, using coax for your low level signal cables, adjusting the length of your speaker wires, using shielded wires for your speakers all may help. Another is to use twisted pair wire for your speaker cables. If the speakers cables are acting as antennae, then the offending signal should be on both leads to the speaker. Twisted pairs tend to reject common mode interference like this. You also may want to go through your amp and clean up solder joints, as was suggested earlier. If at all possible, it may be worth trying to adjust the circuit design so that all of the grounds come together at a single point, aka a star ground. Also, install a grounded power cable and have the ground wire attached to the metal chassis, near the star ground, but not on the same screw. Grounding the chassis will use the metal as a Faraday cage to channel RF signals that may get into the chassis to ground.
If you find out who the offender is, the needle trick does sound effective, but make sure you don't leave behind any evidence; fingerprints, etc. Then the cops can get you for destruction of property.
Peace,
Dave
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