VHF Power Amplifier Construction Rochester VHF Group 9 November 2007 VHF Power Amplifier Construction Presenters: Frank Pollino, K2OS John Stevens, WB2BYP 11/6/2015 Rochester VHF Group.
Download ReportTranscript VHF Power Amplifier Construction Rochester VHF Group 9 November 2007 VHF Power Amplifier Construction Presenters: Frank Pollino, K2OS John Stevens, WB2BYP 11/6/2015 Rochester VHF Group.
VHF Power Amplifier Construction Rochester VHF Group 9 November 2007 VHF Power Amplifier Construction Presenters: Frank Pollino, K2OS John Stevens, WB2BYP 11/6/2015 Rochester VHF Group 2 VHF Power Amplifier Construction Why more power? “I don’t know why he wasn’t hearing me…” “Nobody seems to know we are out here in this grid…” “Always keep a few dB in your side pocket…” “You need more goo…” 11/6/2015 Rochester VHF Group 3 VHF Power Amplifier Construction Trade offs of higher power? Pros Higher contact statistics – more stations to work, open new modes of operation Troposcatter circle radius extends Better link margins – fade bridge, perceived reliability of communications in QRM and QRN Cons Higher potential for interference Spectral considerations – you will raise profile in the neighborhood. Harmonic and Inter-Modulation Distortion (IMD) products need to be managed in the design Space and Weight 11/6/2015 Rochester VHF Group 4 Triode or Tetrode ? Cathode Driven Triode (Grounded Grid) Require higher driving power 50-100W Simple cathode bias with Zener diode No neutralization required No screen supply and screen protection circuitry Easy tune-up 8877 / 8938 tend to be pricey for new tubes 11/6/2015 Rochester VHF Group 5 Triode or Tetrode ? Grid Driven Tetrode: Lower drive requirement High power gain may require more attention to construction May require neutralization (plan for it) Requires a screen supply (typ 200-500VDC 100mA) Proper tune-up required (monitor g1, g2 currents carefully) Some Tetrodes can be configured as cathode driven grounded grid – may have to bypass G2 for RF and apply appropriate DC voltage Some Tetrodes can be G2 RF & DC grounded (4-1000A) Transit time limits this possibility at UHF Interelectrode dynamic problems – bypassing and low PS impedance on G1 and G2 11/6/2015 Rochester VHF Group 6 Tube Selection Triodes: 3-500Z or 3-1000Z (50 MHz only) 3CX400A7 (8874) 3CX800A7 3CX1200A7 3CX1500A7 (8877) 8938 GS35b TH-308/318/328/338 11/6/2015 Rochester VHF Group 7 Tube Selection Tetrodes: 4X150A / 4CX250B family GS-15b 4CX400A 4CX800A 4CX1000A / 4CX1500B 4CX1600B 4-1000A 7650 / 7213 TH-327 / TH-347 11/6/2015 Rochester VHF Group 8 Tube Socket & Chimney Socket: Few dollars to a few hundred dollars for a new unit Hamfest and e-Bay availability Coaxial type can be homebrewed Chimney: New units are expensive Hamfest and E-Bay availability Often can be homebrewed Choose materials carefully 11/6/2015 Rochester VHF Group 9 Metal Work Metal Bending Brake Shear Press Hand Tools Snips, Nibbler Jig Saw Hole Punches – Greenlee, Hole Saw Shielding Considerations – overlapped joints, reduce the possibility of slot antennas, RF hazards Plenty of screws – covers top and bottom 11/6/2015 Rochester VHF Group 10 Parts Acquisition Shop e-Bay and Hamfests – put the word out on the nets / email Local surplus outlets – Where would we be without Glenwood Sales, Conkey Ave and Avenue D, etc? Surplus Sales of Nebraska, Fair Radio, All Electronics, Jameco, DigiKey Use appropriate RF connectors on the interconnect, relays and antennas Transformers – size for continuous duty Filter Caps – allow for voltage rise and continuous duty Diodes – expect transient behavior that will need 2-3X voltage and current rating HV Connectors – rated for service RF Connectors – minimum Type N but consider larger if there is the possibility of anything other than a flat load. UHF connectors can and will arc / evaporate. 11/6/2015 Rochester VHF Group 11 Assembly Tips Consider the fact that RF connections in the output network have 10’s of Amperes of RF current – connections have to be heavy, clean, and have good dielectric insulation to ground or other HV gradient points Meter everything – inexpensive and crucial for troubleshooting Fuse or Circuit Breaker everything you can Plenty of Air for the Anode and to the Cathode/Filament seals If possible make it such that you can get at the output coupling for loading adjustment – ideally front access Build in a method for power output measurement 11/6/2015 Rochester VHF Group 12 Power Supplies – Step Start 11/6/2015 Rochester VHF Group 13 Pre-Tune Up Find a friend to help you with the initial turn-on-smoke-test Fresh set of eyes to review the implementation Watch (meter) filament voltage – variac if possible Electrically purify vacuum on old tubes! Do an emission – bias check on the tube Especially for old/used tubes – operate for a test phase with full voltage and normal idle bias to check for contaminated vacuum – gassy tube Glass tubes – look for inter-electrode glow – often a bad sign – varies with tube type 11/6/2015 Rochester VHF Group 14 Final Tune Up Bring up power slowly the first time – gain some confidence Use all your senses – listen for arcs, sniff, look for smoke Make sense from all the meters - Use a wattmeter that is rated for the frequency Take the time to compute both the DC operating conditions efficiency, and the RF gain / power efficiency If you can, inspect the spectral content with an analyzer Two tone test will tell you an important clue – all distortion products should be at least 30 dB down and 35-40 dB is real good. Get some honest believable on-the-air reports from a reasonable distance – with reduced signal levels Investigate reports 11/6/2015 Rochester VHF Group 15 Safety Tips • RF Hazards - Know what your ERP is and consider the environment around your antenna http://www.ve1alq.com/downl oads/software/vk3um.htm 11/6/2015 Rochester VHF Group 16 Interface To Station Ensure that you have a good ground connection that will take fault current to ground Keyline to ground vs voltage to key – your choice, but buffer the keyline that goes to the rig HV on TX: Bias off the Amplifier vs Key Control of HV – advantages to both Sequence the Power Supply and the Antenna Relay Provide for a protection relay for Preamp 11/6/2015 Rochester VHF Group 17 T/R Relay Transco 11000 Series “Y” 11/6/2015 Rochester VHF Group 18 Data Sheets for High-Power Triodes http://www.df6na.de/df6n a/tubes.htm http://www.g8wrb.org/trio des.php 11/6/2015 Rochester VHF Group 19 Data Sheets for High-Power Tetrodes 11/6/2015 Rochester VHF Group 20 50 MHz Power Amplifiers http://www.qsl.net/gm3woj/8877amp.htm http://www.nd2x.net/OZ1DPR.html http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=13214 http://www.qsl.net/yu1aw/index.htm 11/6/2015 Rochester VHF Group 21 W6PO 144 MHz 8877 PA 1.5 KW 11/6/2015 Rochester VHF Group 22 W6PO 1.5 KW Amplifier 11/6/2015 Rochester VHF Group 23 144 MHz Power Amplifiers http://web.wt.net/~w5un/8877-1.htm http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=13217 http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=15726 11/6/2015 Rochester VHF Group 24 222 MHz Power Amplifiers 11/6/2015 Rochester VHF Group 25 432 MHz Power Amplifiers http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=13197 http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=13216 11/6/2015 Rochester VHF Group 26 903 MHz Solid State Amp 11/6/2015 Rochester VHF Group 27 903 MHz Solid State Amps http://www.vhfsouth.org/tutorials/902.htm 11/6/2015 Rochester VHF Group 28 1296 MHz Amp – DB6NT SSPA 11/6/2015 Rochester VHF Group 29 1296 MHz Amp 11/6/2015 Rochester VHF Group 30 1296 MHz Amp Multiple 7289 Triode Amps 11/6/2015 Rochester VHF Group 31 1296 MHz Amp TH-328/338 Triode Amps 11/6/2015 Rochester VHF Group 32 1296 MHz Amp GS15b Tetrode Amps 11/6/2015 Rochester VHF Group 33 Water Cooling Tubes http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=13215 11/6/2015 Rochester VHF Group 34 2304 Solid State Amp 11/6/2015 Rochester VHF Group 35 2304 Solid State Amp 11/6/2015 Rochester VHF Group 36 Commercial Power Amplifiers http://home.cshore.com/lunarli nk/info.html 11/6/2015 Rochester VHF Group 37 Commercial Power Amplifiers http://www.ssbusa.com/be komos.html 11/6/2015 Rochester VHF Group 38 Commercial Power Supplies Power Supply for HV – Lunar Link Switcher for HV – www.wattsunlimited.com 11/6/2015 Rochester VHF Group 39 Show and Tell 11/6/2015 Rochester VHF Group 40