Bi-Directional IF Amplifier Stage from G4GXO
So, you just popped for 100 Pieces of the SMD version of the J310 for about $20 and that is when you discovered that China didn't pay the 10% tariff -- you did. About $2 extra to buy 100 pieces. Stupid decisions have consequences! A Tip of the Cap to you MAGA-O-Lytes.
Now what do you do with those 100 Pieces? With due recognition to Ron Taylor, G4GXO who designed this circuit which appeared in SPRAT #128 you build it. Yes, it is a bilateral circuit and signal reversal is done with Voltage switching. If you are a serious homebrewer, then you need to join the G-QRP club and purchase the SPRAT on a Stick!
In case you bought the SMD version of the J310 it has a max voltage of 10 Volts and this circuit should work at 10 VDC -- it might need some resistor tweaking but don't fret it will work OK.
This circuit simulates a Dual Gate MOSFET and does have an advantage of being able to adjust the gain by what is applied to Gate #2. In several of my transceivers where I used this circuit, a relay applies AGC to Gate #2 on Receive but switches in a fixed voltage on Transmit for max gain.
With a bit of twizzling in LT Spice you could make this a single J310 but lose the ability for AGC or ALC or Fixed Gain at Gate#2. Since the J310s are in cascade, the current flow (current draw) is less than for two separate devices.
This circuit has seen service in my Tri-Band SS HW-100 and the KWM-4. You can see the SS HW-100 at https://www.jessystems.com
So, another piece to homebrewing a rig that has a low current draw with flexibility and bilateral. No, this is not a Bitx Topology although most likely a (TIA) termination insensitive array. The 820 Ohm resistors across the Toroid windings force a 16:1 match -- yes in/out is 50 Ohms.
BTW a really cool side benefit is that when you apply AGC to Gate #2 and have the level set just right -- the LED's Blink/Wink and show the AGC action. See the video at about 1min 20sec.
When you know you can make things go!
73's
Pete N6QW