Hello people, looking for a way to lessen the receive sensitivity to the immediate area (such as inside of a house) of a standard chinese cheapo AM/FM radio. These radios dont have any tuning coils, or any other components on the board, except for the single AM FM Receiver chip and a simple audio amplifier, and its assorted components.
I know that the AM band is simply represented by a 3 ft whip antenna (I think), and the FM section seems to be represented by the Ferrite lAntenna Bar.
Is it simple enough to just remove the whip for AM, and unwind a portion of the Ferrite Antenna Bar.
Whatcha think??
Thanks in advance for any help
Kim

 

Don't do that. The whip is for usually for FM and the bar is for AM. Messing with bar turns will detune the AM section.
Removing the whip will reduce FM reception. The AM is tricky because it's a magnetic field antenna.

 

Try wrapping everything in aluminium foil. The AM can be attenuated by tilting vertical.

 

Why would You want to ruin a perfectly good Radio ?
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Why not just turn down the volume?

 

Why not just turn down the volume?

I think the radio has poor selectivity. Pretty common with the one chip receiver solutions.

 

There are frontend filters that are inserted between the antenna and the radio that will reduce a local broadcast band signal.
Possibly a very simple wave trap will do that. If you like messing with that a lot then solder an sma and switch an external antenna in or out,
Joe Carr's Radio Tech-Notes TNOTE06.PDF

A well designed adjustable wave trap and parts used to reduce QRM @ 1.1MHz
kjs crystal radio, wave trap 2

 

Don't do that. The whip is for usually for FM and the bar is for AM. Messing with bar turns will detune the AM section.
Removing the whip will reduce FM reception. The AM is tricky because it's a magnetic field antenna.

Damn it, Mixed those up!!!

 

Are you trying to block one specific frequency?

 

Hello people, looking for a way to lessen the receive sensitivity to the immediate area (such as inside of a house) of a standard chinese cheapo AM/FM radio. These radios dont have any tuning coils, or any other components on the board, except for the single AM FM Receiver chip and a simple audio amplifier, and its assorted components.
I know that the AM band is simply represented by a 3 ft whip antenna (I think), and the FM section seems to be represented by the Ferrite lAntenna Bar.
Is it simple enough to just remove the whip for AM, and unwind a portion of the Ferrite Antenna Bar.
Whatcha think??
Thanks in advance for any help
Kim

As pointed out by @nsaspook you've got the antennas in reverse, and as he also pointed out, the ferrite bar is part of the circuit in a way that something like the whip is not. There is usually more than one inductor wound on the ferrite and changing anything about it will change the circuit's tuning.

An important—and unanswered—question is why are you trying to "limit reception"? What is the problem to which this is the solution? I can speculate*, but rather than play 20 questions it would be really helpful if you would explain what is going on and how you expect this to make things better.

*My surmise is that you are trying to transmit something in the AM BCB and you want the receiver to be dedicated to that transmission. This is mere surmise and my be wildly inaccurate—so help us help you, state the problem you are trying to solve, not the solution that has now become the problem,

 

Thank you for your comprehensive reply. I Have an extensive project that is too long and complicated. I would like to attempt to only receive local radio. I dont think that the sigle chip simple radios are as prone to antenna unbalance as its older more complex designs. They start out as being incredibly more sensitive as their older brothers

 

Are you trying to block one specific frequency?

Thanks for the reply.
No just limit its receiption to the local area

 

There are frontend filters that are inserted between the antenna and the radio that will reduce a local broadcast band signal.
Possibly a very simple wave trap will do that. If you like messing with that a lot then solder an sma and switch an external antenna in or out,
Joe Carr's Radio Tech-Notes TNOTE06.PDF

A well designed adjustable wave trap and parts used to reduce QRM @ 1.1MHz
kjs crystal radio, wave trap 2

I think that the "Pro Wavetrap" is a bit of a overkill for me, maybe I should tru figure 3

 

I think the radio has poor selectivity. Pretty common with the one chip receiver solutions.

The problem is that this chip is far too sensitive

 

The problem is that this chip is far too sensitive

Define what radio station or frequency you wish to receive. Then maybe we can recommend a different solution.
A simple crystal radio circuit or MK484 circuit should do the trick.

 

The problem is that this chip is far too sensitive

Is it sensitivity or selectivity you're having problems with? Do you have distortion, bleed-over, FM capture issues or do you only want to restrict what stations can be received. Sensitivity should be handled by the receivers AGC. If we knew exactly the circuit and chip the circuit might be modified to only receive stations of high RF levels across the band.

 

Is it sensitivity or selectivity you're having problems with? Do you have distortion, bleed-over, FM capture issues or do you only want to restrict what stations can be received. Sensitivity should be handled by the receivers AGC. If we knew exactly the circuit and chip the circuit might be modified to only receive stations of high RF levels across the band.

The chips, such as TDA1083 do not allow you to access such functions, which is why I want to limit its receiption

 

The chips, such as TDA1083 do not allow you to access such functions, which is why I want to limit its receiption

Why do we need to pry information like that out of a poster. The TDA1083 does have AGC for the IF section. Pin 16 is AGC/AFC

 

Next question, Why do you want to reduce the radio's sensitivity?
Most people want to increase the sensitivity.

 

Why do we need to pry information like that out of a poster. The TDA1083 does have AGC for the IF section. Pin 16 is AGC/AFC.
This is a very good question. Could it be that the O.P. simply does not have the experience to understand the question that you have given, hense his plea for assistance. Remember, not everyone has the skills that you do. I would suggest that if you are finding that the O.P. is maaking his questions difficult, that you abandon your responses, anad move on to a more skilled o.p. that matches your skillset exactly. Now back to the statement at hand, now that I got this off my chest.
Someho, I think that the schematic that you have posted is a hybrid of this radio, with extended functions, as I have athe radio here on my bench tht in no waay has transistoirs , diodes IF Transformers, etc...ot only haas a handful of components plus the chip.
It is incredibly hard to include the exact chip marking s, as its microscopic. I will continue looking for a schematic