frequency doubler

[Marks256]

I have a 48MHz crystal oscillator (actually it is like 48.38MHz, or something) that i have connected to a simple antenna. I am using it to knock out my sister's radio (she likes crap that i don't), so whenever she listens to the radio, i just turn it on, and it knocks out whatever she listens to (on the FM band). I cannot, however, kill anything over 100MHz.

I know that it isn't a very good circuit, but hey, it gets the job done...

How would i multiply the frequency of my oscillator? I found a site that used a 100MHz can to do what i am doing, and it was able to knock out every channel on the radio dial. So, i figure if i can get about 96-98MHz, that should be close enough to knock out the FM band.

 

[audioguru]

The second harmonic of your 48.38 crystal oscillator is at 96.76MHz which is in the middle of the FM band. The third harmonic at 145.14MHz is probably much stronger and might be a TV, police or fire department radio frequency.

A cheap radio doesn't have a tuned circuit at its input so its input gets overloaded by a single strong frequency. A good radio would not have a problem except for trying to receive weak signals near the frequency of the interfering frequency.

You are probably causing interference to many people's radios and TVs so stop kidding around.

 

[justDIY]

Mark check out VCO circuits and PLL circuits.

An easier way to locally nock out radio stations is just get yourself one of those CD to FM transmitters and just tune it to transmit on whatever station you want to nock out. this way you're safely limited in output power and frequency band affected.

 

[Leftyretro]

Couldn't you just 'upgrade' your sister to one that has your same taste in music?

 

[Marks256]

The second harmonic of your 48.38 crystal oscillator is at 96.76MHz which is in the middle of the FM band. The third harmonic at 145.14MHz is probably much stronger and might be a TV, police or fire department radio frequency.

A cheap radio doesn't have a tuned circuit at its input so its input gets overloaded by a single strong frequency. A good radio would not have a problem except for trying to receive weak signals near the frequency of the interfering frequency.

You are probably causing interference to many people's radios and TVs so stop kidding around.

The closes household to ours is about a quarter of a mile. Then the next closest is about half a mile. I am running the whole thing off of an almost-dead 6v battery. Last time checked, it was putting off ~3.5vdc.

Couldn't you just 'upgrade' your sister to one that has your same taste in music?

ugh... wouldn't that be a perfect world...

An easier way to locally nock out radio stations is just get yourself one of those CD to FM transmitters and just tune it to transmit on whatever station you want to nock out. this way you're safely limited in output power and frequency band affected.

I would be fine with a cd to fm transmitter. My only question is, can they be tuned to any frequency on the fm band? The ones i was looking at a while ago could only be tuned to 3 or 4 preset frequencies...

 

[justDIY]

iRIVER makes something called the audio bug ... it has a digital pll (I think) that synthesizes the fm radio band ... it tunes in 100 khz steps, from 87.something to 108.0 mhz.

last one I bought was $14, then they had 'em on a two for tuesday sale, $20 for 2, so I have three now

 

[Marks256]

Great. I think i will get ahold of one of them. thanks.