Here you can find information about equipment I use and several tehnical projects. All equipments have been built together with Robi, S53WW
2m PA GS-35b
Power amplifier "Vasilij II." with GS-35b
is built around former Russian military base station which was used for air-ground
communication. We removed all electronics and some mechanical parts except tunable
resonator (100-150 MHz), RF output filter, directional power detector and coaxial relays.
2m PA 2x3CX300
PA was constructed based on YU1AW design in 1995 and
1996 with 4CX250B tubes. Amplifier was working just fine and stable and then one day I
forgot to connect the blower. After that output power droped down to about 500 W (tubes
became very old, hi). So I decided to replace the tubes. After unsuccessful trial with RE
025XA tubes (Tesla), I replaced them with 4CX300A. Now it delivers about 700 W.
On the photo you can see an easy solution to connect XVRT to TS-850 (separate RX and TX line). Read instructions in Dubus 2/1992 first and decide if that solution is satisfactory for you. If not:
One very good feature of TS-850 is analog AGC voltage output that can be used as very accurate receive signal strength meter (S-meter). This voltage is available on ACC2, pin 6 and comes from IF UNITas signal SM (signal monitor). When using big meter one can have under 1 dB resolution of RX signal level in 100 dB dynamic range (from -96 dBm to +4 dBm). With proper calibration absolute values of receiving levels can be read. AGC voltage goes from 5.16 V for +4 dBm to 0,22 V for -96 dBm and is fairly linear in the middle region (about 30 mV per dB). With AIP OFF one can get additional 16 dB of RX level measurement sensitivity.
Also the IP3 was checked to see if the band pass
filter switching diodes are responsible for 10 dB lower IP3 on 28 MHz with respect to the
14 MHz value (as measured in the ARRL lab). We found no deterioation of IP3 with diodes
present - it was around +19 dBm in both cases for 20 kHz signal spacing. The IP3 on 14 MHz
was only around +22 dBm for 20 kHz spacing.