Here's a cross post of mine from the FlexRadioSmartSDR Yahoo group: I've been mulling over the same question.
One needs between 40 and 50dB of gain to get to 25 or 50 watts (44 to 47 dBm) output. I'm waiting to find out just how much output one can expect from the 6700 transverter transmit port on 2 meters. The documentation says 0 to +10 dBm, max. I want to find out whether this figure varies from one 6700 to another as well as how much it may differ between the 0-77 MHz configuration and the 135-165 MHz selection, let alone variations in each segment. Being conservative, let's assume 0 dBm is the max that comes out of the transverter port on 2 meters. I looked at the DownEast Microwave 2 meter, 30 watt amplifier, the 2M30PA. Its specifications say it requires +10 dBm, typical, and +14 dBm (25 mW) saturated, drive power. Clearly, the 6700 won't drive it to saturated output. The question is, "How far will it drive it?" It's likely that an interstage amplifier (post-amp?) with 10 to 15 dB gain will be required to boost the 6700 2 meter output up to the point where an amateur-market device will serve as a useful "barefoot" transmitter. Some folks (like me) want to drive an EME amplifier directly with the 6700 without going through a 28 MHz IF transverter. I like the idea of very clean transmit characteristics (phase noise, for one) when running 1 KW near other 2 meter contesters. 50 watts seems like the right target output power to serve most needs. Here's what I am likely to chose among: 1) Spend WAY too much money and purchase a Mini-Circuits ZHL-100-52+<http://www.minicircuits.com/pdfs/ZHL-50W-52.pdf> instrumentation amplifier that could be used for 2M, 222, and 432 with appropriate output filters. It has 50 dB of gain (47 dB min.), but has an absolute maximum drive limit of +2.0 dBm. It might need a safety pad on the input if the 6700 has more than that amount of drive available. This method requires the least amount of ingenuity and/or engineering work, but is very expensive, not comfortably robust, requires a 24V power supply, and still needs lots of T/R switching, etc. 2) Spend less money and buy a W6PQL 80 watt 2 Meter amplifier kit that uses an SAV36 power module. <http://www.w6pql.com/2_meter_80w_all_mode_amplifier.htm> It needs +17 dBm of drive, so 20 dB of gain and a 1 dB compression output of +20 dBm seems right for a post-amp leaving the 6700. The post-amp might be a Mini-Circuits ZHL-2500VH+<http://www.minicircuits.com/pdfs/ZFL-2500VH+.pdf> . It has 18.5 - 21.5 dB of gain and a 1 dB compression power of 200 mW (+23 dBm). It can also tolerate +10 dBm of drive with no damage. It can run from 13.6 Volts and costs more than double the W6PQL kit, but it comes ready to go. 3) Purchase a DownEast Microwave L144-28HP 60 watt output transverter<http://www.downeastmicrowave.com/PDF/Manuals/L144-28rB.PDF> and "weird-wire" its guts to eliminate (disconnect or remove) the LO and mixer sections. I propose to use only the low-level transmit chain amplifiers all the way through to the PA module. The 6700 transverter output would connect where C44 feeds the IC3 (MAR3) transmit pre-driver. I would remove C44 from the circuit-board and feed a coax (reconnect C44 in series) to the input of IC3. The other end of this coax would go to where I propose to remove C90 and connect to the junction of R35 and R36, the output of the TXIF adjustable pad. This pad works well enough at 10 meters and will probably work just fine at 2 meters if one isn't terribly choosy about perfect VSWR. I propose similar messing about with the receive pre-amp sections to provide a really great pre-amp with at least 2 dB better noise figure than the internal 6700 135-165 front-end pre-amp. Details to be easily worked out. This option uses high quality, robust components in the both the transmit and receive signal chains, includes T/R switching, and runs from standard 14V power supplies. Plus, if one ever tires of this way of doing things, it can be put back to a useful condition with reasonable value at resale. END OF LIST! If anyone else has an idea or two, please let me know. Cheers, Mike - W8MM - EM79sd --- In [email protected]<mailto:[email protected]>, "DrPaper" wrote: > > The output of the 6700 is 0 dbm or 1 mW on 2 meters > > Anyone have any suggestions for an amplifier to raise the power levels to > something useful? > _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software innovation and other technical SDR topics.
