WIRE LESS MICROPHONE

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WIRE LESS MICROPHONE

Post by ultrasonic™ on Fri Aug 20, 2010 12:13 am

My FM Wireless Microphone has been a very popular project with beginners and experienced constructors alike. It has been used inside guitars and as the basis of a remote control system. I do however, receive many requests for a higher powered circuit and better microphone sensitivity. Now I can introduce the new FM Wireless Microphone (v5), which also has a better frequency stability, over 1Km range (under ideal conditions) and is good on microphone sensitivity. This has been achieved by adding an RF amplifier buffer (with 10dB gain) and an AF preamplifier to boost the modulation a little.



Construction is quite simple. L1 is 3.25 turns in spiral form and is an integral part of the PCB foil pattern. The two BC547 transistors can be replaced with (almost) any small-signal NPN transistor, such as the 2N2222. The final stage is a BC557 PNP general purpose device. If you use different devices then you should select the 1M0 resistor for 5-volts DC at the collector of the the first transistor. Select the 47K resistor for 3 - 4 volts on the collector of the third transistor. Here is the V5 component overlay drawing. Note that there is a modification:



There used to be a 1n0 5mm cap for supply decoupling, but after a cange of component supplier (manufacturer?) there developed some form of RF instability when the gain of the PA transistor was a little above normal. Replacing the 1n0 to an electrolytic capacitor of 22uf cured this problem totally. Any "radial" (the leads both come out of the same end) type electrolytic capacitor from 0.47uf upwards cures the problem. The finished unit draws about 30mA which should vary as you touch the tuned circuit, a good test that the unit is oscillating. You should remove the 4K7 resistor if you use a dynamic microphone.





The PCB is 50mm x 25mm, a little larger than the first version but there are three stages instead of just the one. The first prototype is shown above, beside the battery powering it. The output power is about +10dBm which is about 10dB more than the first FM Wireless Microphone. This would theoretically give it 3.12 times the range (1.6Km) but I have only tested it using a handheld receiver with the TX laying on the bench indoors. But I got a comfortable 700 meters (and a few funny looks from our neighbours).



Above you can see the addition of a "gimmick" capacitor added across the 12p tuning capacitor to lower the frequency of the transmitter. Make the capacitor by twisting two lengths of single core insulated hook-up wire, about 2cm long. This will reduce the frequency to the bottom end of the band. Cut short the capacitor to increase the frequency to the desired final frequency. If you cut it a few KHz too high then just twist the gimmick a little tighter.

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Re: WIRE LESS MICROPHONE

Post by makoy on Sun Sep 16, 2012 10:02 pm

tol,pwede tuning capacitor na nsa fm radio ang gamitin instead of trimmer??? makakarecieve dito kahit anong klasing fm radio dito sa atin????nice to,. ilan over all cost dito?????

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Re: WIRE LESS MICROPHONE

Post by ultrasonic™ on Mon Sep 17, 2012 1:03 pm


teka sis... di ko mkuha wla nmn trimmer sa diagram scratch

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Re: WIRE LESS MICROPHONE

Post by triac on Mon Sep 17, 2012 4:49 pm

salamat for sharing sir ultra..wala akong project na ganito.. Very Happy

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Re: WIRE LESS MICROPHONE

Post by Digitap on Mon Sep 17, 2012 7:05 pm


sir hindi mo pinost ang source link. hala ka. iisipin ng iba sayo ang circuit Razz

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Re: WIRE LESS MICROPHONE

Post by makoy on Mon Sep 17, 2012 10:07 pm

gano kalaki ang pcb/./????

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Re: WIRE LESS MICROPHONE

Post by ultrasonic™ on Tue Sep 18, 2012 1:17 pm

Mylene wrote:
sir hindi mo pinost ang source link. hala ka. iisipin ng iba sayo ang circuit Razz

lngya ka princess nnakot ka pa..
ito ang Link

makoy wrote:gano kalaki ang pcb/./????

di ko maalala ang akin sis.. basta gnaya ko lng ang nasa link...
same size ng 9V/6LR61 package.


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Re: WIRE LESS MICROPHONE

Post by Digitap on Wed Sep 19, 2012 7:46 pm

ultrasonic™ wrote:
lngya ka princess nnakot ka pa..
ito ang Link

lol!

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Re: WIRE LESS MICROPHONE

Post by xyrrej on Wed Sep 19, 2012 10:56 pm

mga sis may ask ko lng may receiver po ba to?

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Re: WIRE LESS MICROPHONE

Post by ultrasonic™ on Thu Sep 20, 2012 2:51 pm


ordinary FM radio. pwde na sis

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Re: WIRE LESS MICROPHONE

Post by makoy on Tue Sep 25, 2012 6:50 pm

sis pano kuba gawing 102.4 ang frequency nito ???pki tulong naman,.,.,ok na ang ginawa ko 94.3 ang frequency

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Re: WIRE LESS MICROPHONE

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