Captain Midnight and the Moonlight Raiders PART III
Ok, so basically the last design setup sucked big time. Power hungry and provided very little output for that power consumed.
I did a complete redesign of the oscillator circuit to run 10-20mW with low voltage <4.5volts and low current drain of less then 200mA and all going into 50ohms or close to 50ohms as we can get everything.
Here is what we have so far... I'm keeping the JF tin as it's a good size and seals well.
1. The new RF circuit. We kept the uC pcb unit and the power supply board(far background).
1A. I forgot to add this one. It shows the antenna matching tuner I made for this oscillator test. It works ok but I need to pull a few windings off the coil and it should match the longwire antenna a bit better...However, it does work! :-) Yeah I know... no shielding!
2. Here we see the unit running. The Homebrew power meter uses the bottom scale and x100 so here the unit is at about 12mW output power into a 50-Ohm dummy load and the spectrum analyzer confimsthis value. I tacked everything onto this ugly orange plastic pulled off a kitty litter pale (Note: this material is a PV blend and nothing bonds to it not even the super glue it really needs to be melted together to hold properly... then you have to deal with toxic fumes of melting it so i'll deal with the super glue snapping off from time to time).
Some notes here;
* Crystals rated at 10.140MHz are not actually 10.140 but rather 10.137.43MHz? Cheap crystals and rated at 100ppm what did I expect?!?!
* Running the circuit at 10.136MHz was amazingly stable and this is a good place to leave it during this design phase. I know it places it way outside the normal Visual MEPT range of 10.140.00-10.140.10MHz but it has good power and stability to make up for this location difference... or so I hope.
* Updated the beacon message to include QSL information is causing me to rethink changing to a uC with more memory, or using a I2C ram chip to increase message size if I stick with this 12F675 (Currently 874 bytes out of the 1024 are used, I do have some EEPROM area on the chip I can squeeze a few things in but no big deal I'll just switch to 16F628's or go all out with 18F8722's from the parts shelf when the time comes... still I like this 12F675 and should use more in future projects. A secondary note to this is a portion of this memory almost 241bytes are filled up with an experimental PWM program that only runs during start up as part of a test... this could be removed without problems).
* My power supply budget was dead on this time... I'm very happy with that.
* No sinewave on this one... just simple clean DFCW the PWM program is a test of the future sine-saw generator output from the PIC uC.
* Output control of the DFCW by the uC is perfect, a nice 10hz shift is generated with 0 slope issues from the RF circuit not pushing that crystal up to 10.140MHz is the reason I feel.
* Kitty litter plastic bonding agent that works quickly (other then melting the PV plastic material).
* Buy/Build shelf unit to house MEPT's and new propagation beacons inside lab area... this will help drifting issues and keep me from having to fight spiders and wasp when I need access to the units.
* Still no real schematics to post... scribbels on paper. I know I suck! Still looking around for a decent schematic drawing program.
Questions & Comments are always welcome.
Disclaimer:
This information and the circuits are provided as is without any express or implied warranties. While every effort has been taken to ensure the accuracy of the information contained in this text, the authors/maintainers/contributors assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.
I disclaim everything. The contents of the articles might be totally inaccurate, inappropriate, or misguided. There is no guarantee as to the suitability of said circuits and information for any purpose whatsoever other than as a self-training aid. I.E. If it blows your equipments, trashes your hard disc, wipes your backup, burns your building down or just plain don't work, IT ISN'T MY FAULT. In the event of judicial ruling to the contrary, any liability shall be limited to the sum charged on you by us for the aforementioned document or nothing, whichever is the lower.
I will not be held responsible for any damages or costs which might occur as a result of my advice or designs. All of my designs are allowed to be used for commercial purposes without my written authorization.
Chemical Safety:
Use of any and all Chemicals is simple “Read the damn Label” and don’t be a Hero or an Idiot.
Use, Recycle, Reuse and Dispose of everything properly.
I did a complete redesign of the oscillator circuit to run 10-20mW with low voltage <4.5volts and low current drain of less then 200mA and all going into 50ohms or close to 50ohms as we can get everything.
Here is what we have so far... I'm keeping the JF tin as it's a good size and seals well.
1. The new RF circuit. We kept the uC pcb unit and the power supply board(far background).
1A. I forgot to add this one. It shows the antenna matching tuner I made for this oscillator test. It works ok but I need to pull a few windings off the coil and it should match the longwire antenna a bit better...However, it does work! :-) Yeah I know... no shielding!
2. Here we see the unit running. The Homebrew power meter uses the bottom scale and x100 so here the unit is at about 12mW output power into a 50-Ohm dummy load and the spectrum analyzer confimsthis value. I tacked everything onto this ugly orange plastic pulled off a kitty litter pale (Note: this material is a PV blend and nothing bonds to it not even the super glue it really needs to be melted together to hold properly... then you have to deal with toxic fumes of melting it so i'll deal with the super glue snapping off from time to time).
Some notes here;
* Crystals rated at 10.140MHz are not actually 10.140 but rather 10.137.43MHz? Cheap crystals and rated at 100ppm what did I expect?!?!
* Running the circuit at 10.136MHz was amazingly stable and this is a good place to leave it during this design phase. I know it places it way outside the normal Visual MEPT range of 10.140.00-10.140.10MHz but it has good power and stability to make up for this location difference... or so I hope.
* Updated the beacon message to include QSL information is causing me to rethink changing to a uC with more memory, or using a I2C ram chip to increase message size if I stick with this 12F675 (Currently 874 bytes out of the 1024 are used, I do have some EEPROM area on the chip I can squeeze a few things in but no big deal I'll just switch to 16F628's or go all out with 18F8722's from the parts shelf when the time comes... still I like this 12F675 and should use more in future projects. A secondary note to this is a portion of this memory almost 241bytes are filled up with an experimental PWM program that only runs during start up as part of a test... this could be removed without problems).
* My power supply budget was dead on this time... I'm very happy with that.
* No sinewave on this one... just simple clean DFCW the PWM program is a test of the future sine-saw generator output from the PIC uC.
* Output control of the DFCW by the uC is perfect, a nice 10hz shift is generated with 0 slope issues from the RF circuit not pushing that crystal up to 10.140MHz is the reason I feel.
* Kitty litter plastic bonding agent that works quickly (other then melting the PV plastic material).
* Buy/Build shelf unit to house MEPT's and new propagation beacons inside lab area... this will help drifting issues and keep me from having to fight spiders and wasp when I need access to the units.
* Still no real schematics to post... scribbels on paper. I know I suck! Still looking around for a decent schematic drawing program.
Questions & Comments are always welcome.
Disclaimer:
This information and the circuits are provided as is without any express or implied warranties. While every effort has been taken to ensure the accuracy of the information contained in this text, the authors/maintainers/contributors assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.
I disclaim everything. The contents of the articles might be totally inaccurate, inappropriate, or misguided. There is no guarantee as to the suitability of said circuits and information for any purpose whatsoever other than as a self-training aid. I.E. If it blows your equipments, trashes your hard disc, wipes your backup, burns your building down or just plain don't work, IT ISN'T MY FAULT. In the event of judicial ruling to the contrary, any liability shall be limited to the sum charged on you by us for the aforementioned document or nothing, whichever is the lower.
I will not be held responsible for any damages or costs which might occur as a result of my advice or designs. All of my designs are allowed to be used for commercial purposes without my written authorization.
Chemical Safety:
Use of any and all Chemicals is simple “Read the damn Label” and don’t be a Hero or an Idiot.
Use, Recycle, Reuse and Dispose of everything properly.