TroubleShoot

Author: Michel P.   

1)FM Transmitter N°1:

First you have to build the digital board described on this website.

a) Set the frequency to 98MHz..

b) Tune the VCO coil to adjust the PLL control voltage to 5.5V.

c) Set now the frequency PLL to 108MHz and adjust the coil located in the BFR96S amplifier stage, in order to get the maximum Power level for this frequency.

d) Settle alternatively the PLL frequencies to 88,98 & 108MHz and check the ripple power.(Ripple Power should be <0.5dB)

A spectrum measurement will ensure that all the settings have been well performed.

2)FM Transmitter N°2:

First you have to build the digital board described on this website.

This ultimate PLL design doesn't need any RF tuning.
Consequently, we just advise to check the control voltage coming from the PLL in all the FM range.
A spectrum measurement will ensure that all the spurious or harmonics are well rejected. (Min=-60dB)

3)100W Power Amplifier:

In fact ,there's no tuning in the FM Power amplifier design,however due to the different batch of transistor ,you could encountered some Power Gain issue during the trial test.

Through the capacitor C4 ,you can adjust step by step the Power Gain by using different capacitor values.

During this specific setting ,try to work with a moderate input power level to avoid damaging the MRF317.

After this setting if you notice that the collector current is to high for a 100W output power (I>5A at 98MHz),try to tune or check the L3 hairpin.

*For C4 :sold your ATC capacitors as close as possible to the body transistor.

*You must use ATC capacitors in all the RF path,if you don't follow this rule ,you will damage definitely this FM power amplifier.