2N4427 1Waat FM Verici


Tanınmış Üye


Values for the 1W FM transmitter:

L1 L2 L3 L4 L5 L6
Diameter: 8mm 8mm 5mm 5mm 5mm 5mm
Turns: 4 2 1/2 4 1/2 4 1/2 4 1/2 4 1/2
(3 1/2 + 1)
L1 and L2 are winded on the some form with adjustable core.
All coils are made of 0,5mm^2 Cu.
DR: 0.5mm^2 Cu through 5x10mm HF choke
L3 works at the double frequency of L1.

Values for the 25W FM amplifier:

L7 L8 L9 L10 L11
Diameter: 10mm 8mm 7mm 8mm 8mm
Length: 5mm 10mm 10mm 10mm 10mm
Turns: 2 4 2 4 3

All coils are made of 1.5mm^2 Cu.
DR: 0.5mm^2 Cu through 5x10mm HF choke
Instead of BLY89A you may use 2N6082, which can take more SWR.

25W FM transmitter
Use a two layer board, and connect the two sides by drilling holes and
soldering a copper wire in it. This is marked as doughnuts.
The transmitter is built as two separate units, in two shielded boxes. All
capacitors should be ceramic. Both power transistors needs good cooling.
A heat conducting paste should be used, and a cooling rib should be placed
on the outside of the box.Short about how it works
The oscillator (BFY90) is oscillating on half the frequency. Frequency
doubling takes palace in the following stage, where the 2.nd overharmonic
is amplified. Since all stages is working in class C, you don't have to use
a switch to turn of the amplifier. When the 1W transmitter part is turned
off, the 25W amplifier also shuts off, as no base current is given.Trimming
For this you need a SWR meter, and a 50 Ohm dummy load. Make the 1W unit
work first. When you know this unit is adjusted properly, you can connect
the amplifier and start trimming it. The trimming part can be a bit tricky,
since all variable capacitors have to be correct set. Start from the left
and work yourself against the output, and repeat this procedure severaltimes.


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