If you dabble with homebrew then most likely at one time you have used a Dual Gate MOSFET (DGM) and Type 43 Ferrite Cores.
Type 43 cores especially the FT 37-43 form the backbone of much of our homebrew gear. They show up as matching transformers or RF Chokes. The Type FT 82-43 can become a 2.5 Millihenry RF Choke with about 70 Turns of #28 enamel wire.
Amidon is a short distance from my QTH -- about 70 miles but a standard shipping fee of $14 for $12 worth of product is not cost effective. The W8DIZ Kits and Parts is of course a great alternative especially since he is known as the Toroid King.
But a funny thing showed up on my phone yesterday and that is that Digi-Key sells the Fair-Rite Toroid stock. Don't get too excited they only sell the ferrite side not powered iron. Below is a link to the equivalent FT-37-43 cores and 100 pieces are about 21 cents per unit.
The Al values are the same so whatever turns are specified in the design will work with these Fair-Rite cores. Thus, a Ferrite Toroid lot can be an add on to any Digi-Key order and the shipping is much better.
One of the most frequently used DGM's in designs of old was the RCA 40673. Alas no longer made and a Surface Mount rival the BF991 also no longer made. Before you dash off an email about BF998's still being made -- that is true and can be purchased "Mounted" from www.mostlydiyrf.com. The one difference is the BF991 can operate with 20Volts Vdd but the BF998 has a 12Volt Vdd limit.
An alternative to the 40673 is to connect two J310's with the Source of one J310 connected to the Drain of the second J31o. This LINK features a N6QW Direct Conversion Receiver using the J310's c0nnected as a DGM.
The J310's are employed as DGM's in three areas in the above photo: the RF Amp stage upper LH corner, two in the IF Module (center) and one in the Product Detector lower middle.
BTW that IF Module was converted into a steerable IF Module shown in yesterday's posting.
So why even consider a DGM -- the all important Gate #2. The Bias setting on Gate #2 can control the stage gain. In one transceiver build I have the stage gain set with an AGC circuit on Receive and with a small relay switches over to a fixed bias on transmit. Look for the blinking LED's showing the AGC Action on Receive. (Yes, this is a work of Art! WYKSYCDS.)
Those are your two Tech Tips for today.
73's
Pete N6QW