long range RF amplifier

[JimB]

All these "FM transmitters" with parallel tuned circuits in the collector of a low power general purpose transistor, and a random length of wire for an antenna connected to the transistor collector are just kiddie toys.

It is pointless discussing which transistor will give more power and greater range with such an arrangement.

The most important things to get right for good radio range are:

The antenna
The antenna
And in case I forgot to mention it, the antenna.

For VHF the antenna needs to be either a halfwave dipole, cut to the correct frequency.
Or a quarterwave vertical cut to the correct frequency and operating over a suitable sized groundplane.
Other arrangements will work, but lets keep it simple for now.

The antenna should be as high as possible, clear of all obstructions, and fed with low loss coax cable.

When all that is right, then you can think about a proper transmitter circuit.

By the way, with a proper antenna, you will only need a few milli-watts to communicate over a 1km unobstructed path.

JimB

 

[Nepaliman]

How much range will be a transmitter used single transistor BF494 with 12V battery? Can i use 12V, 50Amp large battery?

 

[audioguru]

A BF494 transistor has not been made for many years. Today it is very obsolete.
Its sister was the old BF194 that was used as the RF transistors in a car radio made by Philips in 1967. That was 45 years ago.

Its max collector current is very low so it was used as a low level RF amplifier, not an RF power amplifier.

With a 12V battery then it will probably draw much more than its low max current rating which will destroy it.

 

[Ziddik]

Hi! For a stable output and looong range, use a "S8050" transistor! The right one for fm transmitters