The next relatively comprehensive TRFMW radio circuitcan be built using just a coupe of FETs. It is designed to provide a decent headphone reception. For a longer range a longer antenna wire could be attached with the radio, or else it could be utilized with lower sensitivity by depending o...
L2 and L3 are Bourns, 1.2 µh , subminiature, RF chokes. S1 is a DPDT mini toggle switch. J1 is a banana jack for the antenna. The antenna can be less than 5 feet in long, which could be a normal telescopic antenna readily available from the market. Using an Electret MIC In the...
Using an antenna analyzer, I was able to tune my antenna to 1.1:1 SWR and an impedance of 45 ohms at a frequency of 147.02 MHz. I was shooting for 147.06 MHz, but the setting knob on most analyzers can be really touchy, so this was close enough for me. I did have to trim a li...
Antenna and Earthing I stretched roughly 20 feet of 24-gauge copper wire over the ceiling to serve as the antenna for this single transistor receiver. This looks quite long, but since I'm almost 100 miles away from any strong AM station, I did not have any other choice. I had a single...
You can use a 30 inch long single cored wire as antenna if telescopic antenna is not available. A high value capacitor C2 is added to the relay contacts which makes sure that the relay is not triggered immediately due to some false RF signal but only after making sure the signal is genui...
This DTMF output is fed to a FM transmitter circuit which picks up the audio data and transmits it in the air through its antenna. The shown FM transmitter stage is a bit different from the ordinary ones as it encloses an additional stage in the form of T3 and a centered tapped LC ta...
Your smart phone FM radio would also work but the range would be significantly less than conventional radio having a telescopic antenna. If you intend to operate the units for a room to room conversation then probably your phone would do the job as the receiver, ...
Lenses in optical communicators do what the antennas for RF circuits. The significance of perhaps basic lenses cannot be over-stressed. If a high-frequency RF engineer is able to construct an antenna with 60 dB gain for under 10 dollars, we could have probably witness many satisfied RF technic...
9-The receiver tuning dial, mounted on C3 could be calibrated using an AM signal generator attached to the antenna and ground terminals. Plug-in high-impedance earphones or AF voltmeter to AF output terminals, with each tweaking of the generator, adjust C3 for getting optimal level of audio ...