Monday, January 9, 2017

Back to Bitx40 and OLED Displays

Expanding the Bitx40 Horizon ... More Hacks!

1/10/2017 ~ I was asked what does Size 1 look like on the display?

The frequency information is in Size 2 and the other info was in size 1. I guess it is readable but small letters. It is obvious you could pack more info on to the display. But I think I will stick with Size 2.
Pete N6QW

1/9/2017 Posting

In the course of adding a few refinements to my Bitx40 OLED display, I now have found  new dimensions to displaying information and some additional possibilities for the rig. In the realm of "cool factor" I now have managed to juggle information locations so I can include my call sign (N6QW) on the display.

This is not ego stuff but more of displaying pride in your homebrew rig. Well there is some ego stuff too, where it is something I did and you can too!. BTW you can adjust the print size of what is displayed and what you see is Size 2. The Size 1 selection is almost unreadable but none the less gets you "The Lord's Prayer" on the head of a pin head. Keep in mind the size of the display below is less than 1 inch on a side.

A bit more of what happens to the display and the capabilities when various modes are exercised. The display shows a 100 Hz step tuning rate which is the default setting. Engaging the Push Button located on the encoder control will step that to 1 kHz, 10 kHz, 10 Hz and then back to 100 Hz. The display will show each of these steps. Additionally when you hit the Push To Talk Switch on the Microphone the display changes the line "Bitx40" to "On the Air". When the button is released the display reverts back to "Bitx40". Pretty cool!

I feel confident these are changes that could be done to the VU2ESE supplied LCD/Arduino Nano/Si5351as the changes are in information displayed but does not disturb how frequencies are generated. So maybe someone reading this blog and has the VU2ESE board can make the changes and contact VU2ESE to include it on the hfsigs hack page.

The other aspect is the ability to tune outside of the ham bands which in this case shows a frequency of almost 33 kHz above "40 meters". This feature is good for listening only! I don't believe there is any world wide amateur operation permitted above 7.300 MHz; but there are shortwave broadcast stations that operate in this range. There are even websites that will help you locate these stations based on the frequency being read on your display.
Now before you get too excited -- typically the designs of our transceivers include Band Pass and Low Pass Filters. These filters by design limit your frequency excursions (especially on the transmit side). So tuning 30 to 50 KHz above or below 40 Meters will result in your ability to hear stations. A well designed set of filters will make it seem like the rig has gone deaf once you get slightly above or below the specific band --it should work like that!
Another limitation is what are the frequency end points set in the Arduino code. So in addition to the hardware limits (BPF and LPF) there are frequency limits typically coded into the sketch. Thus one of the hacks is to somewhat expand the lower and upper frequency limits so that the Arduino will tune either the AD9850 or Si5351 slightly above and below the 40 Meter Band.
The rig now being sold by VU2ESE includes the LCD display along with the Arduino Nano and the Si5351. I am unaware of the limits set in the code. So if you have one of the new rigs drop me an email N6QW  and let me know the limits. Of course I "rolled my own" so I picked the limits.
My OLED is now being driven with an Arduino Nano (versus what I did for the original development using the Uno). One report I received from Mike WA3O who is using an OLED with his Bitx40 is that he is hearing noise generated in the OLED being induced into the Bitx40. He further advised that having a separate power supply for Arduino/OLED abated the noise generation problem. Thus I have not had the OLED in the rig but will run that test and report the results.
More refinements the 100's, 10's and 1's are displayed in a window like view of the actual frequency. Helps focus quickly where you are in the band. Another hack!

Pete N6QW