#270 AM Radio DIY kit

episode 270
building and testing a 7 transistor AM radio kit
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[pichacker]

Hi great video thank you for giving up your time making it. To align AM radio like this the procedure is usually as follows...

Set the IF as you have to a predetermined frequency by signal injection and peaking. The spec said 465k, you used 455k and mine worked best on 470k. Guess this is an arbitrary value based upon where the slugs sit most comfortably in their adjustment range. For a professional circuit you would use the manufacturers data as this would ensure correct tracking of LO and AE circuits with dial readings.

AE=Aerial
LO= Local Oscillator.,

For the RF the common way to align would be as follows:-
Set the trimmers mid way. Both AE and LO.

Tune to the lower end of the tuning band and either align the dial with a known station or your signal generator if you have one.
Carefully tune the LO (red) coil to get the desired station/frequency.
Now slide the coil on the ferrite rod for maximum signal

Tune to the upper end of the tuning band and either align the dial with a known station or your signal generator if you have one.
Carefully tune the LO trimmer capacitor to get the desired station/frequency.
Carefully adjust the AE trimmer capacitor to get best reception.

Repeat the above as the items interact.

Once done, the dial will reasonably track the AM band with consistent sensitivity.

I have one of these that I set to cover the 160m ham band and can listen to the locals on a Sunday on AM :)

I found it best to mount the antenna bracket between the variable capacitor and the board.

Keep up the good work.

Steve

[monteceitomoocher]

Bit late to the party by a few years but i seem to have acquired this kit, lot of good info here to digest, cheap crappy little kits have always held a certain fascination for me!.

[chronobot]

I built this radio.

It didn't work initially.

I found out one of the coils (IF cans) was bad.

The end of the coil wasn't soldered to the leg. I was able to fix it, but it wasn't easy... very fine wire coming from the coil.

After that, the radio worked fine.

I peaked the output by ear by tuning into a station and turning each IF can for maximum signal.

Performance is pretty good.

The battery holder is garbage. Used super glue to hold it in.

Definitely worth $5 if all the parts work.

[jbqb]

Thanks, I just got same kit.This is my first.Got it to learn how to solder.will start tomorrow, This really helps as I don't read Chinese. 😢

[odindimartino]

I broke the same component assembling the same radio but in a different way. I also found some tips to assemble and test this kit without any fancy equipment : put the resistor in a way to have test point and measure the emitter voltage of V2 with a good old analog voltmeter to see if the IF is aligned (V2 is used as a variable gain stage for the AGC by varying the collector current).

[kennethrichter]

Thanks! no coils or transformers were identified in my kit but your finished product helped. I followed the colors.

[Steven-rext]

Had some heath kit(r) parts so i rummaged through. Found one slug ment for low short wave and subbed it for big red I kept the original coil just cobbed the slug. Tunes kinda high. Runs well. Have several and broke some. You did alright

[stephenwilliams]

NPO caps. were worth the effort. Along with good restors. I would not be afraid to take this radio any where.

[ralphburns]

Mine worked right off the bat even with a severely chipped disc cap in the audio output, really pulled in a lot of DX.

[stephenwilliams]

Nice radio. Next time I put one together. Will sub with NPO DISC CAPS.and get real restors. Thanks.

[juanmanuel-qgsw]

Nota: siempre que trabajes con bobinas IF hay que medir su continuidad con un multímetro antes de soldar a una placa, también he tenido estos problemas en el pasado.

[terrywilson]

IF transformers peak at 465khz for this radio i believe..

[iceberg]

thinking of replacing that detector transistor with a schottkey

[grzesiekx]

I wonder what those transformers are I mean the specifications etc. as I can't get none of those separate, only in kits like this one. I learn how to build my own radios and try to figure out the imepdance matching but I can;t buy those ttransformers anywhere :/ there are some similar ones on Mouser but expensive so for learning purposes I need something cheap. I suppose the second transformer has 600 ohm primary and 8ohm secondery otr something like that?

[VictorGarcia-xrsl]

How do you connect the coil that’s the only thing I’m missing, I don’t really understand the Chinese schematic

[batmane]

That red coil is just for the oscillator frequency adjustment. You can get a fully working radio with that broken coil, it is influencing only the scale of the radio, not the sensitivity or selectivity. Mid position for that coil is perfect. Besides, you can also adjust the oscillator frequency on the trimmer cap located on the variable capacitor. So nothing is lost.

[ralphburns]

All it takes is an ounce of confidence.

[KRAFTWERKK]

lol my kit didn't even come with a 9018G transistor. Just 9018H and 9013H. So i guess i cannot finish mine without replacing one of the transistors. Man these kits are often really hit or miss.

[eduardpascal]

Chinese quality îs very low. It happend to me also. They are not able translate in english.

[stanburdick]

makes absolutley no sense and hard to follow...this is not for a NOOB !