Diverd4777 ) writes:
To Whomever:

How this thing work aside from just scanning & stopping somewhere on the
dial..?

I'm not going to look at the link, but from your comment, I assume
the radio is one of those 2-button FM radios, which are selling here
down to $1.99 each.

I bought one when it hit that point, because I was curious. I couldn't
read the number on the IC, but since there was no ceramic filter (or IF
transformer) I assumed the IC was the Phillips TDA7000. That IC
converts the incoming signal to a very low frequency, I think the 70KHz
area, where active filters can provide the selectivity. Yes, there's
an image problem, but for FM broadcast the image lands between stations.
Checking the datasheet, it couldn't be the TDA7000 because the pin count
did not match. But the Phillips website pointed to some similar ICs,
and one of them had the right pin count. It was something like the TDA7088
(don't quote me, since it's been a while, though I have posted about
it in various newsgroups since I first looked into this). Tracing
the circuit, it was a match. Then I looked more closely at the IC, and
there was a number and it was "7088".

The difference between this IC and the TDA7000 is the extra logic circuitry
for the scanning.

Press the scan button, and it applies a ramp to the varactor in the local
oscillator. When the radio hits a station, a stage notices that it
is a station, and that stops the ramp. Press the scan button again,
and it scans further up the band, until it hits another station, and so
on. Press the reset button, and it goes back to the bottom of the band.

So assuming the spammed radio is the same thing, it is somewhat selective,
and just uses an analog ramp voltage to tune it, rather than a synthesized
local oscillator of a better and more expensive radio.

These radios sell from that dollar or two to twenty dollars or more
with a brand name. I have no idea if the more expensive ones are any better.

I actually never tried mine. I was curious about it's internals. I suspect
operation is limited. Even apart from the odd conversion scheme, the thing
runs off two AAA batteries, which surely can't make for a good mixer,
and I suspect it may tend to overload, like many cheap FM radios before it.

Michael

If you live in an area with Dozens of stations, how can you just pick out the
One or Two you want ??
IF there are only TWO stations in yur area;
or if you JUST DON'T CARE what station you get
- then maybe this is the radio for you..

Possibly good for something, I'm not sure what;

rather spend a few bucks more & get the AM/FM/ SW Jwin JX -m14

http://store.yahoo.com/kb-electronics/jx-m14.html

now THATS a cheap radio !!

Dan

In article ,
(Parking Space) writes:


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