[Just found out you can buy the Big Boy version of newly announced 500-watt Integrated FLEX SDR Radio for about $10K (with a few options). Sell the wife and kids, mortgage the boat and get on the Reservation List.]
Today we will cover another Resurrection Radio. This rig built close to 10 years ago has been hardly used. Was it a Turkey Radio? Often when I suggest a particular item is a Turkey, it is to disparage something I bought or built. You know... It's a real Turkey!
I built this Rig long ago but to this day am searching for a reason why it has been in a closet for nearly a decade Aside from one circuit element everything else was a proven circuit and used previously. This one circuit element was something entirely new to me.
Now I have homebrewed over 50 Transceivers with most of those being SSB and so you sort of get a feel of what works and what may be needed to have something work better. This was an attempt to see if there was something better
This rig bypassed the shelf of shame and simply put in the back of a closet. It's been there for nearly a decade, and yet I haven't missed it. A true mystery as to the neglect.
So, last week I thought I would make one more attempt at making it work and to discern if there was some reason for the disfavor or was it a Turkey.
In fact, the build of this radio named the ZIA was documented in an extensive You Tube video shown below.
The current state of the ZIA shows I even have resorted to a bit of cannibalism
At some point I even started cannibalizing the radio for parts such as the Arduino, Si5351, the encoder, display etc. A place to start before doing anything else on this resurrection sojourn is to reinstall the taken parts. This puts the rig at the near original Baseline.
I should confess this project started a bit off on the wrong foot when I installed a NOKIA Black and White display which was very difficult to read. That was changed to a Color ST7735 display which made things very readable but somehow still did not turn this project into a go to or favored rig.
As you watch the video, this was shot during the peak of Cycle 24 and just listen to the DX stations on 20 Meters. You do not hear those signals during the peak of Cycle 25 a decade later. We were sold a bill of goods regarding the possibilities of Cycle 25! See yesterday's posting
I will now identify the new elements. Drum Roll -- two TIA amplifiers. For those who may not know, the TIA or Termination Insensitive Amplifier is based on circuitry developed by Hayward and Kopski. My term ZIA is to reflect Impedance Insensitive Amplifiers.
In short, the Zin/out of the amp stage will not be affected (changed) by whatever you connect to the TIA circuit. The TIA configuration has its gain set by what resistance is initially installed in the build. You have the option of setting the gain from Tepid to really Hot! I set it for Hot!
Termination insensitivity has many benefits ranging from immunizing opportunities for self-oscillation, to reducing internal circuit distortions and finally inducing the maximum power transfer by providing a constant impedance set at 50 Ohms. In other words, it is the sliced bread of the electronics world.
Our 1st chore is to build another digital LO/BFO board which I have started. From that point I will measure the sensitivity as compared to several "standard" receivers I have.
Has the TIA circuit been oversold?
There is a huge chasm between Termination Insensitivity and Stage Gain. We all want both and simultaneously! Just because it is termination insensitive does not make for a superb amplifier stage. The resurrection will give us another shot to evaluate performance as I want to eliminate performance as a cause for the closeting.
Stay tuned and we may be on cusp of getting this rig back to a whole state and perhaps understand why it was relegated to the back of the closet.
Them That Know Can Make Things Go!
73's
Pete N6QW