Message	Date	From	Subject
7256	2012-02-16 10:57:27	g3wie	Simple PIN diode attenuator
I'm working my way through an "open-source" 70MHz transverter design. The LO and Rx chains are done and prototyped, now I'm looking at the Tx. My proposed lineup is -6dBm -> diode mixer SBL-1/ADE-xx etc -7dB -> -13dBm -13dBm -> MSA-1105 MMIC +13dB -> 0dBm 0dBm -> triple tuned cct per EMRFD mixed form design -5dB -> -5dBm -5dBm -> MSA-1105 MMIC +13dB -> 8dBm 8dBm -> PIN diode attenuator -3dB min, -20dB max? -> 5dBm or less 5dBm -> BFG591 Ic = 150mA in feedback amp +14dB -> 19dBm The MSA-1105 has P1dB 17.5dBm so I'm expecting good 3rd order Ip from them at the proposed levels. I'm hoping the BFG591 will not degrade this at the 100mW level. The PIN diode attenuator is there so you can vary output power without messing up the carefully set mixer levels. Does anyone have any suggestions for circuits that will do the job without dozens of diodes, but will do a reasonable job of presenting a 50ohm source impedance to the BFG591 amp? Comments on the proposed lineup also welcome Chris G3WIE

I'm working my way through an "open-source" 70MHz transverter design. The LO and Rx chains are done and prototyped, now I'm looking at the Tx. My proposed lineup is

-6dBm -> diode mixer SBL-1/ADE-xx etc -7dB -> -13dBm
-13dBm -> MSA-1105 MMIC +13dB -> 0dBm
0dBm -> triple tuned cct per EMRFD mixed form design -5dB -> -5dBm
-5dBm -> MSA-1105 MMIC +13dB -> 8dBm
8dBm -> PIN diode attenuator -3dB min, -20dB max? -> 5dBm or less
5dBm -> BFG591 Ic = 150mA in feedback amp +14dB -> 19dBm

The MSA-1105 has P1dB 17.5dBm so I'm expecting good 3rd order Ip from them at the proposed levels. I'm hoping the BFG591 will not degrade this at the 100mW level.

The PIN diode attenuator is there so you can vary output power without messing up the carefully set mixer levels. Does anyone have any suggestions for circuits that will do the job without dozens of diodes, but will do a reasonable job of presenting a 50ohm source impedance to the BFG591 amp?

Comments on the proposed lineup also welcome

Chris G3WIE