Modifying a Cheap AM radio

I am considering removing the tuning knob and basically locking the radio onto my frequency.

THe "Fab 50" stations back in the 1960s did that, and I thought it was cool.

The one in my town took the knob off and glued a little plastic panel over the tuning view window that said "KJR, Seattle, Channel 95"

The local Mariners Affiliate did it again in 1986, I think, with a "one chip" type circuit, a fixed cap for tuning, a button cell for power and an ear phone.

I've heard that if you look up the FCC ID number in the FCC database you can find a copy of the schematic, which might help.

Let us know how it goes! 😀

I can easily access the inside of this radio and there is room for a larger wire coil for an antenna. I am supposing that a finer wire with more turns is better than a heavier wire coiled just a few times.

I suggest looking for another brand cheap am radio that does cover 1610. Any radio that doesn't cover 1610 must be a real junker. Its audio quality is also likely very poor. You may be hurting your case by distributing something that sounds crappy.

Adding turns to the antenna coil won't help. You need to remove turns from the oscillator coil or adjust the oscillator trimmer capacitor somewhat lower to tune 1610.

PhilB

maybe try looking for one on google as a corporate gift or promotional giveaways or something.. we always get gadgets to give away from those places where i work...

Hi again,

I should clarify my original post. The radio already receives 1610 am. I'm just looking for a way to improve that reception. You know, the "we can make it better than it was..." effort. I have put a part 15 transmitter with no special antenna where I live. I am then using the durabrand radio and measuring how far away I can get a usable signal (a signal that I would actually listen to). Then I am making modifications to the radio and trying again. True, this may not be the radio that will ultimately work the best, but if the modification have any significant effect the radios are cheap enough to give away for a small donation to the station. If by chance this works, I will post the documentation online.

Thanks for all of your advise and information you have posted on this site!

ahhhhhh .. i read that the first time, then got kinda muddied from the addon posts 😉

I'd love to know how this works out..

I did find that if you look up "custom pc badges" on google, you'll find those dome stickers made for computer cases are inexpensive in bulk - something to put over the hole once you remove the knob 😀

you know - this has me thinking - What is the cheapest AA/AAA battery powered AM radio you can find? I started searching google, then I thought "lets see what the other part15'ers come up with" - maybe if we co-op we can get boatloads for pennies?

So far i found 7.99 - thats too much for a giveaway.

The radio already receives 1610 am. I'm just looking for a way to improve that reception.

Sorry, my mistake. Sometimes I don't read carefully enough.

Small, cheap portable transistor radios are usually sensitivity-crippled for several reasons. First, because they are cheap, they have minimal component count and a simple design. This may vary across manufacturers. Secondly, they suffer from a small ferrite loopstick antenna and no ground such as you tend to get with an AC plug-in radio. The small antenna and lack of a ground can be overcome with high RF amplification, but this is difficult to achieve while still getting good overload protection. Higher quality portables can do this with good design and at a higher price.

Here is one thing you could try. If the oscillator vs. antenna tuning tracking is off (possibly the case in a cheap radio), it may come factory tuned as a compromise. You might benefit by tweaking the antenna stage tuning capacitor trimmer to peak at 1610.

As far as adding wire to the antenna goes. If you add turns to the ferrite loopstick, you will detune the antenna stage. You may be able to compensate by adjusting the same trimmer mentioned above, but with too many additional turns, you will go out of range of the trimmer adjustment. A possible better approach would be to add an "antenna" to the loopstick by connecting one end of a wire to the hot side of the loopstick and wrapping it aroung the inside of the case several times. Leave the other end disconnected. This will also likely detune the antenna stage somewhat, but will likely be within the range of the trimmer.

PhilB

I'm just looking for a way to improve that reception.

I don't know if this would be practical, or even helpful, but it's cool 8)

Here is a link to an add-on loop stick antenna that could be simple and inexpensive:

I remember diddling around with this very same issue back when I was a young buck. (hehe - may years ago!). I had an old transistor AM/FM alarm clock that had a very sensitive "front-end" IF. I tried adding additionl wiring around the internal AM loop antenna inside the radio. This seemed to help with the extended reception I was trying to obtain but the radio was overloaded with Short Wave stations and WWV! I ended up yanking out the internal loop antenna and and connected a random longwire antenna outside the house (about 75 ft.) to the input connection were the loop used to be. I was able to receive certain AM stations better but I also ended up picking up a lot more noise and static too.

Hi again!

I spent part of the weekend trying to improve reception on a pocket radio. I appreciate the suggestions and the links. I didn't have any dramatic results with the radio I was testing. If you'd like to see how it was done and the modifications I tried visit the link below. I have pictures there showing the modifications and the results I received. If anyone has any other suggestions please let me know. I don't mind trying them just to see what happens. Thank you!

http://www.techpuppy.com/radio