With no time to spend on new builds, I am forced to look at some older radios that worked but not to what I would call my Left Coast Standard.
This is a twofer project in that I fixed some problems with a radio. When I accidentally found a nice 5 MHz 6 Pole Homebrew Filter, I built but had misplaced, this was the icing. It was now my chance to bring an old radio back to life using a new filter.
The end result is a two-band radio -- 20/40M with USB/LSB Switch Selected and a Tune Function. Nothing like hearing it up close and personal. Not as good sounding as the SDR but quite good.
Main Video
FT-8
As with most of my radio builds of this vintage, it uses the Plessey Circuit with a bi-directional amp stage consisting of two identical 2N3904 amps. In transmit, one of the 2N3904's is the transmit Pre-driver and in the other direction the 2nd 2N3904 is the receiver RF Amp stage. A small pot in the emitter of both circuits enables setting individual stage gains consistent with optimum performance.
The Microphone amp is a garden variety PNP transistor, and the Audio amp is a healthy NE5534 driving an LM380N (14Pin). The driver stage is the one out of EMRFD but modified by me and uses the 2N2222A driving a 2N5109. The Final is a standard IRF510 and good for about 6 watts on 40M.
I don't have a BPF or LPF installed for 20M but that is for another day. This radio when built used a large piece of PCB Board as the base and with an appropriate insulator kit is the heat sink for the IRF510. The surface area is about 100 square inches.
The Digital LO uses the Arduino Pro-Mini with a custom Si5351A built for me by a ham friend. It is smaller than an Adafruit Breakout Board and only has 4 I2C Pins plus the 3 SMA connectors.
Incidentally, last weekend using the HB SDR with the SB-200 (100 watts) I worked the contest on 40M. My best DX was Japan while also working about four Caribbean stations. I guess my Delta Loop likes the East/West propagation.
It was so nice to be able to break the pile ups with the SDR. I attribute that to plain luck but indeed a very nice sounding SDR radio does get a response.
73's
Pete N6QW