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Post subject: An odd discovery!
Posted: Sun Aug 18, 2013 4:58 pm
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Aspiring Musician
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As most of you can tell by my username on here that I am an amateur radio operator who also loves music. Anyway,...I am trying to determine if the guitar pickups themselves are/were picking up RF from my two way radio on the 147.060 mhz frequency(or any 2m/144 mhz frequency),or if the guitar cable was picking up RF. When I keyed the transmitter,a loud buzz came through the amp since my ham shack is right next to my music practice area in the utility room. Obviously,...ole knot head me forgot to put the amp on "stand by" while taking a break to check into our Sunday evening local amateur radio net! :lol: :lol: Maybe the amp itself was picking up RF,...who knows? My computer speakers do the same thing if I have a two way radio close by,...you will hear a buzz from them too when I key the transmitter! :)

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Post subject: Re: An odd discovery!
Posted: Sun Aug 18, 2013 5:04 pm
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It's funny how instruments and amps can sometimes pickup radio waves like that. I used to be able to pick up AM radio via my practice amp in my old apartment.


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Post subject: Re: An odd discovery!
Posted: Sun Aug 18, 2013 5:19 pm
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schnepf13 wrote:
It's funny how instruments and amps can sometimes pickup radio waves like that. I used to be able to pick up AM radio via my practice amp in my old apartment.


Were you living close by a radio broadcast transmitter facility at the time? I can see the possibility of that happening if you picked up an AM radio signal through your practice amp,...OR it had to be one very powerful station to come through your amp like that!
Was your guitar plugged into the amp at the time? If so,...your pickups might have been catching the signal or your guitar cable! My voice did not come through the amp's speaker,...only a buzz came through when I keyed up!

_________________
If it aint' broke,...don't fix it! I like to keep my amps and guitars factory original,...no mods necessary,...don't want them,...don't need them!

My gear as of now;
Standard Strat
Hot Rod Deluxe III amp
Champion 20 amp
'59 Bassman LTD Reissue


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Post subject: Re: An odd discovery!
Posted: Sun Aug 18, 2013 5:38 pm
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Amplifiers just love RF!

As guitarists we tend to think of tubes as somehow being non-linear or inefficient at amplifying high frequencies. The truth is that something like a 12AT7 can amplify up to around 100 kHz, well beyond human hearing. Apart from the tone stack, almost all the natural HF rolloff in a guitar amp occurs in the output transformer and speaker and unless you take precautions to design a tube amp to limit high frequencies it can be very good at finding stray radio signals and wasting power ampifying them.

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Post subject: Re: An odd discovery!
Posted: Sun Aug 18, 2013 9:58 pm
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The grid stopper resistors used at various places within an amp's circuitry are intended to roll off the very high frequency response of that particular gain stage. Fender and others usually uses 68K ohm grid stoppers at V1 and 1.5K ohm at the power tubes with various values in between.

Image

Here are a couple of examples of the frequency response effects due to various values of grid stoppers.

68K ohm

Image

10K ohm

Image

100 ohm

Image

V1 is the most sensitive gain stage when it comes to reacting to RF as the signal is amplified by each succeeding gain stage. Using too small a grid stopper can result in RF getting into the circuit. Too large a value can impact high frequency response of the amp.

Using tube shields is also a good way to prevent signals from getting into the amp circuitry. I have a high power wireless transmitter for my wireless network in my studio where I play. I had to locate the transmitter as far as possible from my amps and use tube shields, otherwise the transmitter causes a rapid "pop-pop-pop" in my tube amps.

I also live near various federal government installations. At certain times of the night, I will hear a loud buzz through my amps. It impacts every guitar and every amp and usually lasts about 15 to 30 minutes. Most often I hear it on Sundays between 11:00 PM and midnight. I am convinced that it is coming from one of those installations and they are doing tests or uploading large amounts of data. Or it is from UFOs. :lol: :lol: :lol:

Most amps in good condition are fairly immune to interference, but cheap cables and single coil pickups are dandy antennas. You can also get leakage through the unshielded body cavities of a guitar. You body holding your guitar works as a great antenna, capacitively coupling signals into the guitar.

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Post subject: Re: An odd discovery!
Posted: Sun Aug 18, 2013 10:24 pm
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Location: Buffalo, NY
KC9SYJ wrote:
schnepf13 wrote:
It's funny how instruments and amps can sometimes pickup radio waves like that. I used to be able to pick up AM radio via my practice amp in my old apartment.


Were you living close by a radio broadcast transmitter facility at the time? I can see the possibility of that happening if you picked up an AM radio signal through your practice amp,...OR it had to be one very powerful station to come through your amp like that!
Was your guitar plugged into the amp at the time? If so,...your pickups might have been catching the signal or your guitar cable! My voice did not come through the amp's speaker,...only a buzz came through when I keyed up!


It was the signal of a powerful station (that broadcasts in Buffalo and can reach Toronto), located right in the middle of the AM dial with a transmitter located about a mile away from my apartment. It only picked up the signal when my guitar was plugged in, and the amp had to be positioned in just the right spot in the room. Even then, it didn't pick up the signal all the time.


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Post subject: Re: An odd discovery!
Posted: Sun Aug 18, 2013 11:39 pm
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Radio signals can play havoc not only with guitars, but also amps. Back when I had a single coil Telecaster Bass 4 decades ago, the Georgia State Patrol used linear amplifiers on their Motorola 2 way radios in their cars because they had to cover such a large area. Anytime a State Patrolman was anywhere within about 2 miles and keyed his mobile up I could actually hear his radio traffic and understand every word he said from the bass pickup.

Back in the 1930's Powel Crosley's WLW (AM 700) in Cincinnati had what was at the time the most powerful AM transmitter. It ran 500,000 watts for about 5 years. That is 10 times today's legal limit of 50,000 watts. This transmitter and the 50KW transmitter that drove it were both water cooled and there is a large pool of water adjacent to the building housing the transmitters. It is said when it was cranking at 500KW (until 1939 when the FTC made them back it down to 50 KW) that if you were standing near a barbed wire fence close enough to the tower that you could hear their broadcasts coming from the barbed wire, no radio required. I've also heard that some people were also picking up WLW in their dental work during this time. I've always here that WLW stood for "Whatta Lotta Watts!"

There's an AM station in Jacksonville, FL (actually the suburb of Orange Park, Fl) that also had a monster transmmitter, WAPE was known as the Mighty 690 and you could hear them all up and down the eastern seaboard in broad daylight! It was also water cooled at one time when it was doing way more than 50KW. I was told it would do way over 100KW no problem, except the water in the cooling pool got steamy. At one time I had photos I had taken of their transmitter. It was so big it took like 4 photos to get it all. There were stories about that one causing some interesting things also.

When I was working in commercial radio, complaints from people about the radio station drowning out their telephone conversations were frequent, especially for people living close to the transmitter site of the larger 50KW AM stations.

Never had many complaints on even the big 100KW FM transmitters causing problems like the high power AM ones.


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Post subject: Re: An odd discovery!
Posted: Mon Aug 19, 2013 3:39 am
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Aspiring Musician
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Joined: Sun Jan 27, 2013 3:44 pm
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bluesky636 wrote:
The grid stopper resistors used at various places within an amp's circuitry are intended to roll off the very high frequency response of that particular gain stage. Fender and others usually uses 68K ohm grid stoppers at V1 and 1.5K ohm at the power tubes with various values in between.

Image

Here are a couple of examples of the frequency response effects due to various values of grid stoppers.

68K ohm

Image

10K ohm

Image

100 ohm

Image

V1 is the most sensitive gain stage when it comes to reacting to RF as the signal is amplified by each succeeding gain stage. Using too small a grid stopper can result in RF getting into the circuit. Too large a value can impact high frequency response of the amp.

Using tube shields is also a good way to prevent signals from getting into the amp circuitry. I have a high power wireless transmitter for my wireless network in my studio where I play. I had to locate the transmitter as far as possible from my amps and use tube shields, otherwise the transmitter causes a rapid "pop-pop-pop" in my tube amps.

I also live near various federal government installations. At certain times of the night, I will hear a loud buzz through my amps. It impacts every guitar and every amp and usually lasts about 15 to 30 minutes. Most often I hear it on Sundays between 11:00 PM and midnight. I am convinced that it is coming from one of those installations and they are doing tests or uploading large amounts of data. Or it is from UFOs. :lol: :lol: :lol:

Most amps in good condition are fairly immune to interference, but cheap cables and single coil pickups are dandy antennas. You can also get leakage through the unshielded body cavities of a guitar. You body holding your guitar works as a great antenna, capacitively coupling signals into the guitar.


So I could assume that the guitar's pickups were acting as an antenna,...or the cable,...and maybe not necessarily the amp? Sounds logical to me and quite possible!
The 2m/440 mhz dual band radio I was using at the time only puts out 5 watts of transmitting power,but must have been just enough since my radio room is right next to my music practice room! I can only imagine what would have happened if I had my 100 watt HF radio going at the time.

_________________
If it aint' broke,...don't fix it! I like to keep my amps and guitars factory original,...no mods necessary,...don't want them,...don't need them!

My gear as of now;
Standard Strat
Hot Rod Deluxe III amp
Champion 20 amp
'59 Bassman LTD Reissue


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Profile
Post subject: Re: An odd discovery!
Posted: Mon Aug 19, 2013 3:49 am
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Aspiring Musician
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Joined: Sun Jan 27, 2013 3:44 pm
Posts: 366
brotherdave wrote:
Radio signals can play havoc not only with guitars, but also amps. Back when I had a single coil Telecaster Bass 4 decades ago, the Georgia State Patrol used linear amplifiers on their Motorola 2 way radios in their cars because they had to cover such a large area. Anytime a State Patrolman was anywhere within about 2 miles and keyed his mobile up I could actually hear his radio traffic and understand every word he said from the bass pickup.

Back in the 1930's Powel Crosley's WLW (AM 700) in Cincinnati had what was at the time the most powerful AM transmitter. It ran 500,000 watts for about 5 years. That is 10 times today's legal limit of 50,000 watts. This transmitter and the 50KW transmitter that drove it were both water cooled and there is a large pool of water adjacent to the building housing the transmitters. It is said when it was cranking at 500KW (until 1939 when the FTC made them back it down to 50 KW) that if you were standing near a barbed wire fence close enough to the tower that you could hear their broadcasts coming from the barbed wire, no radio required. I've also heard that some people were also picking up WLW in their dental work during this time. I've always here that WLW stood for "Whatta Lotta Watts!"

There's an AM station in Jacksonville, FL (actually the suburb of Orange Park, Fl) that also had a monster transmmitter, WAPE was known as the Mighty 690 and you could hear them all up and down the eastern seaboard in broad daylight! It was also water cooled at one time when it was doing way more than 50KW. I was told it would do way over 100KW no problem, except the water in the cooling pool got steamy. At one time I had photos I had taken of their transmitter. It was so big it took like 4 photos to get it all. There were stories about that one causing some interesting things also.

When I was working in commercial radio, complaints from people about the radio station drowning out their telephone conversations were frequent, especially for people living close to the transmitter site of the larger 50KW AM stations.

Never had many complaints on even the big 100KW FM transmitters causing problems like the high power AM ones.


I've seen photos of that huge RCA 500,000 watt WLW transmitter,...and I have also read stories where if you lived close to any transmitter site that powerful(50 kw or above)that even if you turned your lights off,they still might glow a little because of all the RF energy. WOWO AM 1190 from Ft. Wayne,IN still has,...as far as I know,...their 50 kw(actually a 100 kw that ran at half power) Westinghouse transmitter,but it is not used anymore,...though still operational from what I hear. I can only image that if they were still running that thing and you lived close by it,what you would pick up through anything that was suspectible to RF interference,...be it guitar pickups,cables,phones,etc.

_________________
If it aint' broke,...don't fix it! I like to keep my amps and guitars factory original,...no mods necessary,...don't want them,...don't need them!

My gear as of now;
Standard Strat
Hot Rod Deluxe III amp
Champion 20 amp
'59 Bassman LTD Reissue


Top
Profile
Post subject: Re: An odd discovery!
Posted: Mon Aug 19, 2013 5:25 am
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How about a flow sheet for the Krebs/Citric Acid Cycle just to level the playing field :idea: :?: :lol:

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Post subject: Re: An odd discovery!
Posted: Mon Aug 19, 2013 10:17 am
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Aspiring Musician
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It IS weird how electronic devices will mess with one another.

I have a wireless hub for my internet connection, and it HATES all other electronic transmit/receive devices. I have to unplug all of my TC toneprint pedals, my Fuse enabled amps, and keep my hub away from any 2 way radios or it'll boot me off the 'net...

So far, I have not picked up anything through any guitar pick ups or amps yet.


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Post subject: Re: An odd discovery!
Posted: Mon Aug 19, 2013 10:23 am
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The discussion is interesting but not surprising given what an EMP can do to everything electrical in a region where it is discharged.

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Post subject: Re: An odd discovery!
Posted: Mon Aug 19, 2013 1:41 pm
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Friend had to get a utilities smart meter installed in there house and now his main amp is picking up noise from that thing!

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Post subject: Re: An odd discovery!
Posted: Mon Aug 19, 2013 2:05 pm
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ZZDoc wrote:
The discussion is interesting but not surprising given what an EMP can do to everything electrical in a region where it is discharged.


Not quite everything.

EMP may cripple your computer put your tube amp will just shrug it off and continue as normal. The US Air Force may have laughed when they discovered the Soviet MIG fighter jets retained their vacuum tube radio equipment well into the 1970s but as someone pointed out, the transistor version would not have worked after a nuclear blast.

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Post subject: Re: An odd discovery!
Posted: Mon Aug 19, 2013 2:29 pm
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GilgaFrank wrote:
.......as someone pointed out, the transistor version would not have worked after a nuclear blast.

That IS the usual chaser. :roll:

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