1. Duplexer Repurposing Duplexer retired from Ely PD Originally tuned to TX 155.45 RX 158.970 MHz Frequency separation of 3.52 MHz Retune to Gilbert TX 147.150 RX 147.750 MHZ Gilbert Frequency separation of 0.600 MHz Designed for – Frequency range of 144-174 MHz – Minimum Frequency Separation of 0.5 MHz

2. Duplexer Anatomy

3. Duplexer Tuning Duplexer Instruction Manual located on web Recommended Test Equipment – Spectrum Analyzer – Return Loss Bridge (SWR Meter) – Balanced Load Procedure – Tune the passband – Tune the rejection notch

4. Modified Tuning Procedure Impedance Measurement MFJ-269 Antenna Analyzer Tune for lowest SWR at RX and TX frequency Frequency tracking using TS2000 running HRD Drawbacks – Stability of frequency generator drift of 100 KHz – Frequency resolution +/- 50 KHz – Lack of a sweep function to measure rejection

5. TS2000 and HRD Bandscope

6. Equipment Set-up Dummy Load Drake DL300 Analyzer MFJ-269 4-Cavity Duplexer Vari-Notch 28-37-02A

7. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.750 MHz Bandscope reading of 147.700 MHz Frequency Offset of +50KHz Analyzer Calibration at Gilbert Receive Frequency of 147.75 MHz Spurious signal

8. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.200 MHz Bandscope reading of 147.150 MHz Frequency Offset of +50KHz Dummy Load Calibration with SWR 1.3

9. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.800 MHz Duplexer Vari-Notch - Can RX1 SWR 1.4 Bandscope reading 147.75 MHz

10. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.800 MHz Duplexer Vari-Notch - Can RX1 SWR 1.4 Bandscope reading 147.75 MHz

11. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.150 MHz Bandscope reading of 147.100 MHz Frequency Offset of +50KHz Analyzer Calibration at Gilbert Transmit Frequency of 147.15 MHz

12. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.200 MHz Duplexer Vari-Notch - Can TX1 SWR 1.3 Bandscope reading ~147.15 MHz

13. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.200 MHz Duplexer Vari-Notch - Can TX2 SWR 1.3 Bandscope reading ~147.15 MHz

14. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.800 MHz Duplexer Vari-Notch – Combined RX SWR 1.3 Bandscope reading 147.75 MHz

15. Bandscope Reading using TS2000 with MFJ269 Analyzer set at 147.200 MHz Duplexer Vari-Notch – Combined TX SWR 1.4 Bandscope reading ~147.15 MHz

16. Test Results Frequency calibrated against TS2000 Balanced Load measured at an SWR of 1.3:1 Cavities tuned for TX & RX frequencies at SWR of 1.3:1 Rejection unable to be tested quantitatively

17. Test Findings Frequency calibration at 147.150 not precise Cavity Interconnect cables not cut to ¼ Wave Antenna Junction Assembly not cut to ½ Wave Rejection not adjusted

18. Operational Setup K5PFF w/GE Repeater Vertical antenna mounted on porch roof at 36’ AGL

19. Operational Setup K5PFF w/GE Repeater Vari-Notch Duplexer CAT 300 Controller GE Repeater 147.150 MHz Amplifier 12VDC Power Supply

20. Operational Results Fusion repeater disabled for testing GE setup GE repeater returned to service without testing GE repeater installed with Veri-Notch Suplexer on 2/10/2016 at K5PFF QTH Antenna SWR7 on MFJ-269 Repeater functional at short range Failed to function at distance

21. Conclusions GE repeater needs to be checked out Vari-Notch duplexer should be tuned using a service monitor – Used service monitor $2K / new $4K – Rental of service monitor $600/month – Request service from local technicians John’s station should be grounded Penny Uber makes a good lunch