At first glance, you can see a significant reduction in the base level of the
transmitted 70MHz signal, as well as minimal increase in power output.
Other spurious/unwanted frequencies seen before modification, including
45.6MHz and 49.035MHz and 21MHz almost completely gone, or are suppressed
more than 50dB compared to the basic +39dBm signal on 70MHz.
It is worth to note, that the 49.035MHz also disappeared!
In summary:
Transmitter measurements taken before modification:
Power
10W out, QRG 70.100MHz = +37 dBm
Unwanted signals
45.600MHz = 34 dBm! 49.035 MHz =-2dBm
Transmitter measurements made after the modification of the track TX:
10W power out, QRG 70.1MHz: QRG 70.100MHz = +39 dBm
Unwanted signal 45.600MHz =-22dBm below 70MHz Carrier Point
Thus, suppression of unwanted signals is about 55-60dB which is more than
adequate.
Now your FT847 should have output about 60W, with a supply voltage of 13.8 V and
a current of ~ 13A.
Of course, getting this effects in efficiency/performance would not be
possible without prior modification of the PA stage described in outstanding
professional article about 847 filters written by Marc PA1O. Kudos Marc!
The description of the implementation of this PA mod (by SP3RNZ) will be in
the second part of the study.
