So that you avid Blog readers are not cheated, presented next is more detail of the SSB Transceiver shown but not discussed on yesterday's posting.
The genesis of this rig actually started with a project in the G-QRP Club SPRAT called the Sudden Receiver which was like an NE602 Product Detector and a simple RF amp stage and a few other bits and pieces. When I looked at that project it SUDDENly struck me that this could form the basis of a SSB transceiver.
This was the 1st time ever that I used two NE602's as the topology of an extended IF Module. Because of the way it was done, it was easier to use two Band Pass Filters.
So here goes. Looking at the photo below the Top BPF is the Receiver BPF. On the left side is a Matching transformer to match the Input of the NE602 which is not 50 Ohms. Paul Carr (SK) wrote a paper called the NE602 Primer where Carr shows that matching. Checking it now, it is like 1500 Ohms shunted by 3pF. Carr's paper also has select application circuits for the NE602. Read I researched the NE602 before I started.
[1500/50 = 30:1, with a close match to 11 turns and 2 turns where in 11^2 = 121 and 2^2 = 4. 121/4 ~ 30:1.]
The upper NE602 serves as the Receiver Mixer on Receive but as the Balanced Modulator on Transmit. Thus, the relay to the left of the matching transformer switches the Input from the BPF on Receive to the Microphone Amp on Transmit.
In the lower NE602, the relay switches the output of the 2nd NE602 to the Audio Amp stage on Receive and to the Transmit BPF on Transmit. Again, a matching transformer from the NE602 to the Transmit BPF.
Now something I try to avoid is switching LO and BFO signals across the circuitry depending on whether in transmit or receive. But it was done here. A simple DPDT relay cross connected provides an LO signal to the upper NE602 on Receive but that same device gets the BFO signal on Transmit. For the lower NE602 it gets the BFO input on Receive and the LO input on Transmit. Basically two IC's and a lot of heavy lifting.
Before anyone starts to type and chide me for not simply switching the Clock Functions in Software. In Receive CLK0 is the LO and CLK2 is the BFO. When a signal hits the Arduino from the PTT then SUDDENly CLK0 is now the BFO and CLK2 is the LO. Once transmit is cycled, the clocks revert back to the typical standard of CLK0 = LO and CLK2 = BFO. That did not work out too well in practice -- thus the relay.
Top view of the Sudden Main Board. There isn't a lot to it!
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The Sudden SSB Transceiver was published in the G-QRP Club SPRAT and I think there may be one or two You Tube videos where you can listen to the receiver.
N6QW ~ Pure Genius!
2E0NTV's Build of the Sudden
Of Note: I was contacted by a person who identified himself as a NASA employee with a PhD in Electrical Engineering, wherein, he told me I made the worst choice of any device for use in the project by selecting something made for cell phones. His take was "not good for use in a ham rig". You know the usual IMD stuff and lacking gain and subject to cross talk.
That could be but I certainly think it was a successful project with a minimum part count.
About a year after my SUDDEN project, I spotted a single board 17M SSB transceiver in SPRAT from the EA QRP Club called the Pergrino (Pilgrim). It had two NE602's and a relay steered IF Module. I acquired the board where I eliminated about half the circuitry, installed a 9 MHz filter (INRAD Model 315) and gave it the usual N6QW treatment and created the Paesano (Italian for Friend or Pal). One significant add to the Peregrino, I made, was matching to the NE602's and that was done on the underside of the board. The mismatch was too large to simply ignore.
That too was published by SPRAT and even picked up by the EA QRP Club for publication. The relay steering of the Peregrino has now found its way into my projects like the P3ST .
So if we never try we never know... This is worth a consideration and certainly NOT a Bitx. NOT from EMRFD, NOT a TIA and NOT a Facebook Group.
There, today you got a double measure of transceiver projects. However, a key point from today's post and that is the ability to see beyond just a small piece of circuitry and envision the possibilities of taking what you see and creating something entirely new or as the title says Re-New.
73's
Pete N6QW
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