crivoli

Thanks a ton for the response. Just to double check I am thinking of this correctly: A wire goes from A to O. Then a wire from O tp the circuit. ( this is connecting them in parrell, or did you mean in series? ). Then a wire from G to the circuit. This gives me the 220pf? So I would have only two wires running from the cap to the circuit, not 3, and I would have the 220pf. Is that correct? Thanks again PS. Is there a schematic of a variable cap I can find online? Thanks

So is that a wire from O to A and then a wire from A to the circuit and a wire from O to the circuit, and dis-regard G all together? Sorry, I am new to this! In my mind I see a wire from A to the circuit and G to the circuit gives me 160 O to the circuit and G to the circuit gives me 60 A to O with a wire from A to the circuit and O to the circuit is 220. Are these correct or just plain wrong? Thanks again

I am using a transistor from a pack of common NPN-Type switching transistors. I do not have the exact model. The are probably like the MPS2222A transistors. I swapped out the transistor for another one and got the same voltage readings and same results to the speaker. I will post more on the other site.... thanks

Hey Guru Plz Help, I built the AM receiver circuit and fed the output to the "'AM Radio Power Amplifier" on the LM386 datasheet. I have everything hooked up except I am not using "ferrite beads" on the output of the LM386. I actually get a Radio Station around 900AM, but the sound is VERY VERY VERY low!!! I have the IC at a gain of 50 but I have ti put my ear right next to the speaker to hear it. I tried increasing the gain to 200 but no luck. I tested the voltages given on the AM receiver schematic at the specified transistors and had the same voltage at every spot except Q3 ©... no idea why!!: Q1 (b) 1.31V Q2 (b) 0.71V Q2 © 1.34V Q3 (b) 0.62V Q3 © 3.87V <==== I have around .1 V Is there anything else I can do to increase the volume or to fix Q3 ©???? Thanks man -crivoli

Can someone please explain the leads of this variable capacitor and how to hook it up? I have never used one and I want to make sure I get this correct. Thanks -crivoli

My question is if I build this simple AM receiver and feed the output to the LM386 using a gain of 50, should the output to the speaker be good quality audio? I saw the datasheet for the LM386 and it shows an "AM Radio Power Amplifier" schematic, but can I use one of the other setups without having to add the "ferrite bead" etc... ? AM Receiver: http://www.electronics-lab.com/projects/rf/006/index.html LM386 datasheet: http://cache.national.com/ds/LM/LM386.pdf Thanks a ton -crivoli

i believe I solved this problem with your help... Thanks a ton. I seperated the mic and speaker and I also changed somve values of what I was using. Please check my other post on a "Simple AM receiver" Thanks again.

Question 1: I built the circuit on the LM386 datasheet with the amp at a gain = 20. Everything works fine. I then adjusted the gain to 50 and it works correctly. When I adjust the gain to 200 the speaker just squeals horribly. I have built this circuit before and used a gain of 200 with no problems. Any idea of what I could be doing wrong? LM386 datasheet: http://cache.national.com/ds/LM/LM386.pdf Queation 2: I hooked up a preamp circuit using a LM741 and send the output to the amp I built with the LM386. Needless to say the output to the speaker is very bad quality. Is there anything special I need to do with the output of the preamp before it goes to the input of the audio amp? I have attached the LM741 preamp schematic Thanks all -newb

I was going to use alligator clips :) Just wanted to make sure this wouldn't throw anything off. Thanks again

The designer of the AM ciruit said he built this on a breadboard. Any idea how to hook up a variable cap on a breadborad since the connectors don't fit?

So am I able to replace the coil and tunning capacitor in the schematic with any coil and tunning capacitor I find that are compatable with each other? Thanks

So, I could be safe in replacing those components of the schematic with those I found on e-Bay. Does that sound right? Also, on the transmitter schematic it is not clear of what L1 is: http://www.electronics-lab.com/projects/rf/011/index.html Is it another ferrite coil, or magnet copper wire? I assume it is another ferrite coil since this is AM and it's tuning cap is the same value as the other. thanks again

audioguru, No I didn't realize that. How then on that schematic is the antenna a 220uH and the resistor is a 500pf? Do you have to tune the capacitor until it reaches the matching value?

The AM receiver schematic specifies a 500pf variable capacitor. The one on E-bay is 60/160pf. Do you think that will work, or will I need to change values of other coponents on the schematic? Thanks

audioguru: I appreciate your patience with me. Would this work for the am receiver as the 220uH component? http://cgi.ebay.com/Ferrite-Loopstick-Antenna-Coil-Crystal-Radio-Radios_W0QQitemZ6619389741QQcategoryZ7275QQssPageNameZWD1VQQrdZ1QQcmdZViewItem also I can not seem to find any good variable capacitors..... any suggestions? thanks man