Sabotaging a short-wave radio receiver

[Odysseas]

Hello everyone,

I need to manipulate an FM radio receiver in a particular way, that it can no longer receive a specific radio frequency (90.7 MHz in this case), but only noise instead? Is this possible? Perhaps a few capacitors and/or resistors in the antenna path?

Thanks for any help!!

 

[justDIY]

certainly some sort of LC "notch filter" or "trap" could filter out that frequency ... dunno if you could get it exact down to just one station, most likely adjacent stations would be affected too.

https://www.google.com/search?q=fm+notch+filter

 

[Papabravo]

I'm curious about why you want to do this. What would happen if you destroyed the radio in the process of making the modification. Generally one can design a filter for any given level of performance but it must usually be characterized and adjusted in practice. The equipment normally required for this task may be a bit outside of your budget. The frequency of interest, 90.7 MHz is in the VHF range where lead length, component placement and other factors have an impact.

What happens if the affected party goes out and buys another radio?

Don't you have better things to do?

 

[HiTech]

since when was 90.7 FM considered to be a shortwave radio?

 

[JimB]

Theoretically you could make a high Q filter which would reject 90.7 Mhz and give a deep notch at that frequency.
Practically, such a filter would be so large that if would not fit into the radio you are trying to sabotage.

JimB

 

[Papabravo]

since when was 90.7 FM considered to be a shortwave radio?

Shortwave radios cover frequencies with much longer wavelengths than 3.3 Meters. Aint technical terminology grand!

 

[on1aag]

Station suppressor.

Hi Odysseas,

It can be done by building a 90,7 MHz overtone crystal oscillator and
modulate it in FM with a LF noise source. You don't have to connect
it to the tuner, just put it close enough so that only one station will
be "replaced" by the signal from the oscillator.

on1aag.

 

[Odysseas]

Actually, I was already thinking about that. I happen to know that setting up your own short-wave radio transmitter (using audio-radio frequencies) has recently become legal in my country, providing that the power allows only for a few meters range.

I thought about a radio transmitter that would duplicate the signal from one station (104.4 or 106.3 MHz preferably) to 90.7 MHz. However, I like the idea with the noise transmitter. I think this is also much safer, since I have no intention of taking the radio apart, probably damaging it. Do you think you can help me with that?

 

[Hero999]

Actually, I was already thinking about that. I happen to know that setting up your own short-wave radio transmitter (using audio-radio frequencies) has recently become legal in my country, providing that the power allows only for a few meters range.

But how whould that help you here?

This isn't a short wave radio, it's an FM VHF radio, you could even call it an ultra-shortwave radio but please don't call it a shortwave radio, it's incorrect.

 

[HarveyH42]

There is a 'TV Jammer' circuit somewhere in this forum that would likely do the job. Less than 10 common parts one simple, hand wound coil. I remember digging out the old circuit a couple months ago (saved it from high school 25 years ago). It worked on FM radio too.

Still don't know the purpose of blocking out this one frequency, what is being broadcast that is so offensive? Gypsy music?

 

[Odysseas]

It is called UKW in german (Ultra-Kurz-Welle), which would translate into ultra-short-wave radio. I guess you are right, I will use this expression in future. But I see you understand what I am talking about

The radio station I am trying to 'suppress' is called 'Bayern 1', terrible! If you want to give that a try, use this link: **broken link removed**. Select one player (should be pretty obvious). In any case, I just try to make some fun of my friend, I am sure he will just think it is a defect in his radio (it is not the most expensive) and switch to another station. A better one. I mean no harm by this.

In any case, I have seen quite a number of small radio transmitters that would be appropriate. I will try and seek out one of those.

 

[Nigel Goodwin]

It is called UKW in german (Ultra-Kurz-Welle), which would translate into ultra-short-wave radio. I guess you are right, I will use this expression in future. But I see you understand what I am talking about

Perhaps if you had made a sensible entry in your location profile?, we might have known you were in Germany!.

In any case, missing the 'Ultra' off makes nonsense of it.

 

[Hero999]

I've seen FM is marked as UKW as well as FM on some radios. I've always wondered why and know I know.

 

[Odysseas]

To on1aag's proposal: Can you give me a more detailed description of what you suggest? What components would I need besides a Oscillator (a quartz cristal?)? How can I obtain a simple noise close to white noise?

 

[bigkim100]

Why the 'ell would anyone bother tuning in a wimpy, piss-poor signal on a radio...when the station can be so easily be heard over the internet??.
Just buy the guy a pair of headphones, and save yourself a whole load of bother.

 

[Odysseas]

Thanks, that was very helpful :-D