If you enjoy the video be sure to SUBSCRIBE »
Get $5 of New User Free Credit using PCBWay. Full feature custom PCB prototype services, PCB assembly, SMD stencils and CNC / 3D Printing.
Thank you Sverre ( LA3ZA ) for the help with the sidetone circuit.
The Pixie transceiver kit and many other similar designs are great because of their simplicity. You could take that simplicity to extreme and you end up with a Pititico Transceiver. But today it’s all about the Pixie transceiver. I was happy with the kit as it was, except two things. One issue was the constant and annoying AM broadcast band interference. The second issue was the missing sidetone on TX. Here I will talk about a few simple ways to fix the issues, but also a few more modifications. I did it all for fun, but honestly I wasn’t so impressed by the results. Yes it’s fun playing around with the kit, but honestly I think it would be easier if later I would play a little more with the schematic and then design a PCB board from scratch. Then I would end up with a cute Pixie, not the Frankenstein I ended up with now ( hi ).
THE MODIFICATIONS
I didn’t want to make too many changes to the original schematic and the kit itself. So all the modifications are minimal. You could go to extremes and also use a DDS VFO etc. You know I am not into digital stuff so I kept things simple. First issue to fix was the low pass filter. I had to get rid of the AM broadcast band interferences in a way. Also to improve the harmonics suppression a little if possible. For that I modified the filter and now it acts like a bandpass filter instead. It does remove most AM broadcast band interferences, but when it comes to the transmitting part, a bandpass filter it’s not such a great idea. I will return to the low pass filter and make other changes to remove the interferences later on. I would recommend you watch this video if you want to improve the low pass filter of the Pixie transceiver.
The second problem was the missing sidetone on transmit. Some of the Pixie transceiver kits come with a buzzer. I also added one for a while, but it was really annoying. It was way too loud and sometimes I wanted to only hear it in my headphones. Luckily LA3ZA used this circuit in his Pixie transceivers. Is a little sidetone circuit originally used in the FOXX-3 CW transceiver. I couldn’t get it to work at first but with a little help from Sverre, now it works and it sounds amazing. I just changed the tone frequency in my circuit. I just had to adjust the 10K W1 trimmer a lot ( Fig. 1 ) until I got it to work right. So be patient when making adjustments.
The Pixie transceiver usually comes with a 7023 MHz crystal, but I used 7030 MHz instead. As Peter Parker ( VK3YE ) recommended, I placed a variable capacitor in series with the crystal. This allowed me to tune the Pixie between 70305 MHz to 70352 MHz. Not much, but better than having a fixed frequency. I also replaced the trimmer resistor of the pixie with a potentiometer. That is because the RX offset frequency will need constant adjustments. Because of the VXO modifications, the offset will also change. You can modify the VXO even more as I did for this simple DC conversion receiver where I could cover the entire CW portion of the 40m band.
THE SCHEMATIC
I wanted to keep the schematic as close as possible to the original one that comes with the kit. Not to create confusion, all components in black are as per the original schematic. Mine was the Pixie transceiver kit with no LED’s or a buzzer. All components in red and with an N at the end ( N from new ), are the modifications.
I built the sidetone on a separate circuit board. Not so pretty as it was just a test. There is no AF filtering yet, besides the 1mH inductor ( LN1 ) that helps me cut a little bit of the high frequencies. I do have plans on building a much better version in the future. I will keep it simple still, but adjust the circuit the best I can for better performance and I do want some simple CW audio filter as well. I just need a little free time for this. Probably this will be a cold winter days project.
Fig. 1 – Modified Pixie CW Transceiver Schematic
Fig. 2 – Modified Pixie Transceiver Kit
Here you have the completed and modified Pixie transceiver ( Fig. 2 ). Not so pretty but it does sounds really nice. I get about 550 mW of power out of it. Now I must finish learning the Morse code so I can do some fun QSO’s with it. Having no AM broadcast band interferences makes it so much better. If you want the LED to light up only when you transmit, instead of connecting it to ground, make the connection to pin 1 of the CW Key connector.
I will not lie, but I had a lot of fun experimenting with the Pixie transceiver. Both kits actually as I had one from Nigel ( ZL1NAY ) and another one from Andrei ( YO6TJJ ). But lately I started to feel bad for messing them up for mods. So from now on, all kits I will build will be just as they were designed. For all modifications and improvements ideas I will only do scratch builds. Is much more fun and I have more freedom that way. No more mods to any kits I will build from now on, that’s a promise. Most kits are presents and I’d like to respect them. People spend money to send them to me. I think keeping them as they were designed would be the right thing to do. For now I hope you enjoy this one and maybe you can improve it even more.
Honestly I always take simple transceiver circuits like the Pixie and other similar ones as toys, only that these are toys for the big boys. Used well and with patience, you may end up with surprising results. Just have fun with it and celebrate simplicity. Is nice having a transceiver that only has a handful of components and even if it’s far from perfect, it does work pretty decent.
73, YO6DXE
Thank you for the video and especially for including all the information about which kit you used. I’ve been struggling whether to get the kit that says it puts out 3 watts. When I looked at pictures on line I can see no difference. Now I’ll just get the transceiver kit.
Your mods are a nice improvement over the kits I saw on other videos. Honestly some of the videos discouraged me from getting the Pixie. Now I’ve changed my mind and I’ll get one or two of them.
Always a pleasure. I like sharing whatever I find useful. Some things and modifications are worth bothering for… some not so much. But is always nice to experiment. When it comes to the power output of the Pixie, I really don’t bother much about it. 300mW or 800mW is still little power. The fun is into building the kit and see if you can get any QSO out of it. At the end is nothing but a toy… but with a little bit of luck and good propagation, you can get some nice QSO’s out of it. If you go through the latest articles you will find the Pititico II. Is nothing but a combination between a Pititico designed by PY2OHH and a Pixie. So I say is a simplified Pixie with the same power output. Is also a toy but is nice just to spend the time building it and see how much you can get out of it. With simple kits like this you can’t really expect to get much performance. The fun part is actually in making it on your own and being able to use something you built. Have fun with the kit and I hope you also get to experiment with it as well. It is a lot of fun into that. If you mess it up… no worries as you didn’t lose much ( ha ).
73, YO6DXE