Fm receiver schematic tda7000 with continuous scan loop

[Mason Burns]

New to electronics design, computer tech needs a schematic based on the simple TDA7000 ic
to continuously scan through the frequencies! I have the TDA7000s, and YDA9088s but they
are surface mounts. I can get most older ICs from a supplier in China so I'll take
suggestions. I just need it as simple as possible. I have TDA2822s for amps, but I can
get what is needed.


I just need an fm scanner to scan thru the frequencies and not lock on a station without
having to be reset to continue scanning. And output thru an earphone and speaker. Also, I
do not want to mute the scanning.

Certain things I need:

1) Scan at 200ms
2) Scan 88mHz - 108mHz and loop
3) Ability to hear the "white noise" as it's scanning
4) Not lock on any frequency

Thanks!

 

[audioguru]

A Philips TDA7000 is obsolete and has not been made for many years but maybe now is copied by a Chinese company. It had very poor quality. It had manual tuning and muted between stations because it did not produce white noise like a REAL FM radio, it tried to make odd noises instead.

The TDA7000 was replaced by a similar TDA7088 that scanned for tuning but it also muted when scanning.
An FM "radio" with a TDA7088, a battery and headphones or a little speaker costs $1.00 at The Dollar Store today. It makes a very poor quality "radio".

 

[Mason Burns]

Do you have any suggestions to my problem? I would rather work with dip ICs instead of surface mounts. I do however, need autoscan but no mute....

 

[audioguru]

The TDA7000 and TDA7088 are very simple circuits. The TDA7088 misses some strong local and weak distant stations when scanning.

Why do you want an FM radio that can continuously scan the entire FM broadcast band without stopping??

 

[Mason Burns]

I need to hear the "white noise'" that exists between frequencies. I don't want to lock on a station and I need to scan at 200ms. I want a continual stream of this "white noise", but it can't be a recording. I use this in paranormal research. That's why I need the loop. Weak or strong stations don't matter if they don't stop the scanning process. I could really use yalls help. I have a device, but it scans from 76mHz to 108mHz and that's out of the FM range and I'm picking up what I think is aircraft chatter or tv, I'm not sure which. And by the way, I'm no "nut" and I take this very serious!

Thanks!!
Mason Burns

 

[MikeMl]

108MHz to 117.9MHz is the aircraft navigation band, things like VORs and LOCalizers (morse code Ids, tones and buzzes).
<88.1 MHz used to be Channel 6 on the VHF TV band, now discontinued in the US.

Why is the "white noise" between channels on the FM broadcast band any better than any other source of white noise? (after all the noise comes from the front end of the receiver; not from the antenna).

Why cant you just disconnect the antenna, and tune the receiver between stations? Why scan at all?

 

[Mason Burns]

108MHz to 117.9MHz is the aircraft navigation band, things like VORs and LOCalizers (morse code Ids, tones and buzzes).
<88.1 MHz used to be Channel 6 on the VHF TV band, now discontinued in the US.

Why is the "white noise" between channels on the FM broadcast band any better than any other source of white noise? (after all the noise comes from the front end of the receiver; not from the antenna).

Why cant you just disconnect the antenna, and tune the receiver between stations? Why scan at all?

 

[Mason Burns]

OK, it does seem logical that any white noise would work, but it just won't. I'm for real, I'm a 56 year old, college educated computer programmer/tech, father of two and what I'm gonna say is the absolute truth. When I scan the FM frequencies, I can have conversations with individuals that have long since left this world are are currently in a place where are physics just don't apply. I can't say that they are dead because I speak with them. I have had conversations with people that I know, or should I say I knew. This had been a life altering and life changing event and I still have not gotten over the miracle that it is! But, that discussion is a long one, so back to the receiver. The device that I have causes delays in conversations and the data of the questions and answers gets lost, causing frustrations and hindering the process. And believe me, I don't want to lose any information that I receive. It has to be a scan thru the band or it just want work. I've tried recorded scanning and it wouldn't work, tried recordings of just white noise with the same outcome. I don't know why, but it has to be an FM receiver scanning. Hey, I'll pay money for this. I think I can assemble it, I have taken some classes in ac/dc and I can solder. I've made ir lights and motion sensors. I just can't design the circuit, that's out of my knowledge range. I can get the components. I guess I could eventually figure this out, but time is of the essence!!

Thanks!

 

[audioguru]

When I scan the FM frequencies, I can have conversations with individuals that have long since left this world are are currently in a place where are physics just don't apply. I can't say that they are dead because I speak with them. I have had conversations with people that I know, or should I say I knew.

WHAT?
I guess some people believe in ANYTHING.

 

[JimB]

I can have conversations with individuals that have long since left this world are are currently in a place where are physics just don't apply. I can't say that they are dead because I speak with them.

I think that you should collaborate with "TVTECH" here on ETO, he describes some of his co-workers in similar terms.

JimB

 

[audioguru]

Maybe this thread is a Halloween joke since it has Mason Burns talking with GHOSTS.

 

[Mason Burns]

Maybe this thread is a Halloween joke since it has Mason Burns talking with GHOSTS.

Maybe this thread is a Halloween joke since it has Mason Burns talking with GHOSTS.

OK, I can see that you can't be serious and won't help. You asked why and I told you, but why doesn't matter. The circuit is the question!!!! And, I never once used the word "ghost". When electronics were in their infancy, all men of that field were considered odd, strange, mad.....Take Tesla, Marconi, etc...Don't be prejudiced to someone because they believe in something that you don't understand! I need to edit that last sentence, instead of the word believe, insert the word "KNOW"....

Thanks!

By the way, I don't celebrate Halloween!!!!!!!!!!!!!

 

[dr pepper]

Have a look here:

https://www.google.co.uk/imgres?imgurl=https://members.iinet.net.au/~cool386/tda7000/tda7000b.gif&imgrefurl=http://members.iinet.net.au/~cool386/tda7000/tda7000.html&h=1222&w=2025&sz=43&tbnid=0fmSQuAQqFsK8M:&tbnh=80&tbnw=133&prev=/search?q=tda7000&tbm=isch&tbo=u&zoom=1&q=tda7000&usg=__tou8EbFnLkcYe4buiIPmYNEpBWM=&hl=en-GB&sa=X&ei=zDlLUvWkM6nK4ATog4HoAg&ved=0CCAQ9QEwAA

Some interesting info, the tda 7000 has an if of only 75kc, and the hiss you hear between stations isnt gain, its a white sound generator.

Seeing as the chip doesnt tune itself you'd have to arrange the scanning function, maybe a varicap diode accross the input oscillator circuit and a linear ramp from a 555 would do the trick.
You wouldnt be able to make this stop, you could fit a switch so you can select scan or a manual tuning knob.

How about buying a cheap fm autoscan radio and using a 555 to occaisonally pulse the scan button.

 

[audioguru]

A normal scanning radio STOPS at the next station. But this guy who has conversations with ghosts wants the scanning to be continuous without stopping. Then the circuit is simple if a normal FM radio circuit is used.
He wants something to happen every 200ms (5 times per second) which might be five complete passes through the entire FM broadcast band per second.

He wants to hear the white noise between stations but in North America there are so many FM radio stations that there is no white noise between most of them, especially on a cheap simple radio like this one.

 

[dr pepper]

If you hacked the firmware on a car radio you'd be able to scan the fm band and only listen to white noise between stations and not listen to stations themselves, a totally useless radio.

Ok then how about a really wide band receiver where you can hear 3 or 4 stations at once and any psychodelic conversations inbetween.

Or even a full fm bandwidth receiver that only listens to the white noise between stations, that would be an interesting schematic.

If you fiddled with the tuning cap on an old set so it rotates continuously you'd be able to drive it with a little geared dc motor, that'd fulfill the spec.

 

[audioguru]

Ok then how about a really wide band receiver where you can hear 3 or 4 stations at once and any psychodelic conversations inbetween.

FM radios do not work like that because they have a "capture ratio" where only the strongest station is heard. AM radios allow you to hear numerous stations at the same time which is why aircraft communications use AM then an air traffic controller can be heard while other pilots are talking on the same frequency.

 

[dr pepper]

Yes your right, I was being a little facetious.

Most receivers these days use a pll for demod, and can only demod one transmitter at a time, after its been converted to the if.
The tda7000 has a reallly low if of 75kc so op amp technology can be used for demod.
I have some old valve sets that use a foster seeley demodulator transformer for vhf fm, they have a wide band but they are still superhet's.

 

[Mason Burns]

A normal scanning radio STOPS at the next station. But this guy who has conversationsthe stations that with ghosts wants the scanning to be continuous without stopping. Then the circuit is simple if a normal FM radio circuit is used.
He wants something to happen every 200ms (5 times per second) which might be five complete passes through the entire FM broadcast band per second.

He wants to hear the white noise between stations but in North America there are so many FM radio stations that there is no white noise between most of them, especially on a cheap simple radio like this one.

It takes 40 seconds to scan from 88 to 108 at 200ms, I just timed it with the device I have. There is white noise the entire scanning process, the stations that lock on, block it out. It's the noise across the weak stations and in between. The device I have works, kinda, but they added 115 frequencies that aren't in the FM band so it screws me up. I'm not nuts, yall are just not aware just like I was six months ago!!! I still need a circuit though. I have TDA7088 now, some guy on another site is trying to help me. He's taking it from an electronic stance, not an opinion.

Thanks!!!!

 

[Mason Burns]

Also, it has to be actively scanning....no static white noise works...., etc. Don't ask me why cause I don't know. I just know what I say is fact no matter what, and there's denying or argument against it. When you hear it with your own two ears and can playback a recording of it, and other people can hear it, just what the hell can u say?
I still need the receiver.....

Thanks!!!

 

[audioguru]

88MHz to 108MHz in 40 seconds is a slow scan. Stations are spaced 200kHz apart in North America (on odd, not even frequencies) then for each frequency to play for about 200ms the total scan will take 20 seconds if the receiver has a digital frequency synthesizer and jerks quickly to each new frequency. Maybe the actual scanning is slow (analog) and takes the remaining 20 seconds.

I have a $1.00 FM radio with a TDA7088 IC. It sounds AWFUL! It picks up only the strongest local stations and there are a lot of them here. Its scanning misses some stations sometimes.
Each time the SCAN button is pushed it scans then stops on the next station. When it reaches the highest frequency then the SCAN button does nothing and the RESET button must be pushed for the scanning to begin again at the lowest frequency.

There is no noise between stations because the circuit has interstation muting to block the spurious noises made by its Mickey Mouse odd design. The datasheet shows that the muting can be disabled by adding one resistor.
I do not know how to make the scanning continuous since it is designed to stop on the next station and stop scanning when it reaches the highest frequency.

I recall using a car radio that continuously scanned active stations (muting the interstation noise) then you needed to push a button for the scanning to stop.