Sunday, November 1, 2015

Hacking the Ten Tec Model 150A ~ Final Chapter

The Final Round Up ~ Hacking the Ten Tec Model 150A

This is the last in the series on the "hack" of the Ten Tec Model 150A. In a few words -- highly successful and worth the effort. This same approach possibly could be applied to other commercial radios such as the Kachina 102/103 or the Heathkit CAP transceivers.
Many of the blog readers have most likely been bored with this subject and want me to get back to the Simpleceiver -- Believe it or not, what I learned here will end up in parts of the Simple Transreceiver.
I could not find the LSB Filter which was an option; but was apprised by the filter manufacturer, Network Sciences,  that by adjusting the BFO frequency it would be possible to make the USB Filter work on LSB. That was in fact a reality. The secret was the use of the Si5351 to generate the VFO (operating frequency + 12.7 MHz) with Clock 0 and a switchable BFO on Clock 2.
Based on some work I did nearly a year ago my Arduino Pro-mini has been connected to a keypad so that band selection are Keys 1 through 6 (160M, 80M, 60M, 40M, 30M and 20M). Two Keys (0 and 8) enable up/down tuning of the radio from the keypad based on the step rate chosen. Keys 7 and 9 introduce non-standard tuning steps not normally chosen by the encoder switch ( 10 Hz and 100 kHz). That leaves two unassigned Keys. Selection of USB/LSB is done from the front panel of the Model 150A. The LCD Display shows the frequency, the band, USB/LSB and the step tuning rate. If the color TFT display were to be used then you would need more IO pins such as the Mega.
In summary the work that was done was to:
Change the Band Pass and Low Pass Filters to extend the range to 15 MHz. The channel selector switch was programmed so that Channel 5 = 1.8 -3 MHz, Channel 6 = 3 - 5 MHz, Channel 7 = 5 - 8 MHz and Channel 8 = 13-15 MHz.  All filter networks to expand the coverage to 15 MHz were simulated in LT Spice before any changes were made. All original inductances were retained and only the capacitance was changed.
Program the Arduino Pro-Mini and Si5351 to cover the ham bands based on the keypad selection
Create the USB/LSB functionality. [A separate Arduino + AD9850 was used to find the correct LSB BFO Frequency and then that frequency was included in the Si5351 sketch for Clock 2.]
Wire the radio using jacks on the back panel so that the LO, BFO, USB/LSB Selection and Power for the Arduino/Si5351 are plug ins to the radio.
The radio has been tested on 60, 40 and 20 meters with all excellent signal reports. Not bad for about a $120 investment.


In the photo above the two boards shows the low pass/band pass filters that were changed. In the upper board (low level amp) the filter is located in the very upper right hand corner and in the lower board which is the RxTx mixer board that filter is also located in the upper right hand corner. The Ten Tec construction methodology made the task one of simply unplugging cables and removing four screws and then  removing the boards The traces are very large and a simple task to remove components --try that trick with your FLEX 6300.

Thanks for your patience whilst I dabbled with this project. You can find the manual for the Model 150A at the Ten Tec website under the Obsolete Manual Tab.
Back to the Simpleceiver in the next post. Final comment to the naysayers of the Si5351: Here is one more example of its versatility to modify (hack) commercial radios for use on the ham bands. I am having a lot of fun with this "hacked" radio.
Funny comment: While I was having a QSO with a friend whom I asked to listen to the signal since he knows what I sound like -- suddenly a phantom operator (no call sign just a voice) saying he was using his FLEX 6300 said I was over 100 Hz low (since corrected) and that he saw an energy spectrum of about 3 KHz. Thank you for your input.
Pete N6QW
PS I used jpg. and not GIF's this time --sorry!