Skip to main content

A New Line of Transceivers ~ DifX

Transceiver Architecture 2.09

 

Dual Conversion Band Switching


In this posting I want to talk about some of the specifics of the band switching and how to cause the proper Band Pass Filter and Low Pass Filters to be put in line for the band in use.

The Arduino Mega 2560

The first realization I had with the dual conversion multi-band approach was that you needed a lot more pins. There will be those who immediately jump up and say but you can add a pin expander to the standard UNO, Nano and/or Pro-Mini and no need to move up to the larger footprint and more costly microcontroller. There is another requirement that is answered by the Mega 2560 and that is the 10X increase in program size. That perhaps is the bigger driver for the Mega 2560. Undoubtedly there will be more things you want to add to your homebrew rig and then pins is not the issue but programming space will be. The Mega 2560 has 54 digital pins and 16 Analog pins and thus you have many more options available to you. Now as I discovered there are differences from the  Uno, Nano and Pro-Mini so you will need to think about pin assignments and it is not a straight pin for pin compatibility. I will highlight those differences.
 
 

The Band Switching Scheme

My band switch scheme involves two band switches and has the capability for 17 band positions. One band switch has 12 positions and the second band switch has 6 position. So OK you have a blank look on your face. Hey guys Ten Tec did this with some of their transceivers, where you placed the main band switch on 10 Meters and the auxiliary band switch then selected four sub bands within the 10 Meter band.
 
For my Dual Conversion DifX when the main band switch is placed on 60 Meters  that merely connects to the auxiliary band switch where you can select the five channels on the 60M band including one channel that will be tunable as I did in my 60M DifX rig. Moving away from the 60M position in effect disconnects the second band switch.  The process of selecting the operating band with the band switch will automatically trigger a comparable Mega 2560 Pin that has 5 Volts on that Pin to control either relays or Pin Diodes in the Low Pass and Band Pass filters. One switch position changes frequency and selects the proper filters.
 

Mega 2560 Pin Assignments

 
 
 
 
 
The logic of the code is that the digital pins are read, as an example Pin 30, which is designated for 20 Meters when that pin is sensed LOW, then Pin 39 will go HIGH and that switches in the proper Band Pass Filter and Low Pass Filters. On 60 Meters Pin 49 is made HIGH for all of the 60 Meter Pins.
 
Pin A10 and A11 on the Mega 2560 are used for Encoder A and Encoder B. (Thanks Rob!)
 
Keep good notes as we are moving forward with the design.
 
73's
Pete N6QW



Popular posts from this blog

2019 ~ What is the simplest homebrew SSB Transceiver that can be built?

4/27/2019 The Future of our Hobby is Here! Forget those simple rigs with homebrew crystal filters, cranky IRF510's and the analog VFO's. SDR is the wave that is building strength just like a Tsunami. With the Soft Rock V6.3 SMD Version + RRPi2 With the Omnia SDR and RPi2 Pete N6QW How Simple & How Cheap can you  build a Homebrew SSB Transceiver? 4/26/2019 --- I just converted my websites from an obsolete Windows Based Server with GoDaddy to their cPanel (Linux). This was a cost issue as a one year renewal of the Windows Server would buy three years on the cPanel. GoDaddy is discouraging the use of what they call the Obsolete Windows System. So I had to migrate and reload the whole pastapete.com, jessystems.com and the n6qw.com sites to the Linux based servers. Some files and links got lost in the translation --so you might not be able to see everything! Essentially I have  to open every link to verify that it works --that may take some time

New Technology for 2020 ~ The Hermes Lite 2.0 SDR Transceiver

  The Hermes Lite 2.0 SDR Transceiver. November 7th, 2020 ~ It's Settled! It is done! The stain of the Trump era is soon to be removed! Thanks to all who voted. The Voice of the People has been heard.  Congratulations to President Elect Biden and Vice President Elect Harris. Pete N6QW November 3rd, 2020 -- IT WAS THE MOUSE   We all know this is Dump Trump  Day. Go out and vote! It was the mouse! Back in 1999 I stupidly was one of the very first to purchase a Ten Tec Pegasus. Never buy the first batch of a new model.  Touted as the world's first computer controlled radio , actually I think the Kachina 505 was really the first. But the Pegasus was fraught with problems including a trip back to the Smokey Mountains. I was using an older Windows 95 machine to control the Pegasus and that may be a co-conspirator. Well after many calls to TT -- finally someone who has some smarts told me: Fix your station ground, Make all leads short and Buy stock in a ferrite bead company. I did all

The Next Project Updated 10/10/2022! The rubber has hit the pavement!

The Next Project... A 2022 Transceiver. 10/10/2022 My Apologies. It is with regret that I will be terminating any further work on this project. My caregiver duties have over time become a greater time sink and it is almost impossible to build something working only 10-15 minutes at a time spread out over a day. I apologize for not getting it from design ideas to complete hardware. Most likely I have built the last transceiver I will ever build. Thanks for riding along. My website https://www.n6qw.com/  has the pdf of the postings and I will leave this blog page as is. 73's Pete N6QW 10/05/2022 Still Alive! Regrettably my caregiver duties have overtaken any free time so not much progress. But I am hopeful yet this week I will cut at least one board. A PSA from N6QW.  Think of it like Mary Jo has a "crink" in her back and unable to get in the backseat of the 57 VW Beetle. A bit of a setback but not forever.  Seems like the hired caregiver had a small emergency and not able