Improved Pititico CW Transceiver, No AM Broadcast Interferences

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Pititico CW QRPP transceiver designed for the 40m band. One of the smallest QRP transceivers designed around one 2N2222 transistor by @‪@2ohh2‬ This was somehow an improved version from the first one I built. Still it was not exactly what I was trying to achieve at that time.
Latest update: I ended up changing the circuit a little for easier adjustment of the TX/RX offset frequency, to remove the AM broadcast band interferences and improve the low pass filter. Check the blog article for details and the latest schematic and PCB board design.
David ( DL1DN ) built a modified version for the 10m band, so feel free to do modifications for other bands as well.
73, YO6DXE
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DX Explorer is a channel with amateur radio related videos on: schematics, reviews, homebrewing and much more.
I am passionate about amateur radio since childhood. I got back into the hobby in 2016, while living aboard my sailboat. I received my license in 2022. I like QRP mostly, experimenting with all modes. But I am old school, so I prefer SSB or CW.
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Опубликовано:

3 окт 2024

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Комментарии : 57

@G7VFY Год назад

If you connect two, IDENTICAL crystals in parallel, and in series with a small variable capacitor, you effectively have a Super-VXO which will give you a bit of frequency mobility. You might want to try a medium-power transistor, like a BFY50 or 51 with a clip on heatsink. G7VFY.

@dxexplorer Год назад

Ohh yes Peter Parker used to do that with the Pixie. I wanted to keep it simple and close to the original so I left it as it was. But I am working on a modified version that includes the LM386 amplifier as well... so is basically a simplified Pixie... and for that... I will also include the VXO 😁😁. Thanks Stephen 73.

@dxexplorer Год назад

@@janetwinslow2039 I just posted a video on the Pixie a little while ago on that yes 😃. Only that I made the sidetone circuit instead so I used pin 7 for the sidetone. It sounds great and I love it. It didn't work well at first but I emailed Sverre and with a little help I got it to work really nice. And with the improved LPF is even better. No interferences whatsoever. 73

@janetwinslow2039 Год назад

@@dxexplorer The pin 7 mod allows better muting on receive without starving the LM386 Vcc through the 1k resistor!

@sm3981 Год назад

Very nice project my friend! Keep doing more assemblies like that. 73 from Brazil (Sergio)

@dxexplorer Год назад

Thank you Sergio.. is fun to work on little and simple projects like the Pititico. 73 DE YO6DXE.

@EC5ABG Год назад

Muy bueno.73.👍👏👏

@dxexplorer Год назад

Gracias 😃😃 73 DE YO6DXE

@4youian Год назад

Hi Chip, it's working well - great idea. Sorry to hear you were unwell. I'm just recovering from Adenovirus - there are plenty of virus's going around apart from COVID! I don't know morse but one day I'll need to learn it. CW transceivers are way more efficient and simpler than SSB. Take care, 73, VK7IAN

@dxexplorer Год назад

It is efficient indeed and the equipment so much simple to built at times, that you wouldn't be able to do if it was for SSB. Sorry to hear about the adenovirus. I'll make you laugh now... I don't know the treatment for you when it comes to it... but I know the treatment I used for the pigeons as they also have it hahaha. I could get rid of it in less than 48 hours 😅😅😅. Was good to hang out with my pigeons buddy. A lot if the diseases that pigeons have are pretty similar to what we have and the immune system seems to work the same way.. is interesting. 73 Ian.

@QRP.lifestyle Год назад

Nice one ! I just want to have more time for building rigs.

@dxexplorer Год назад

Ohhh I hear you David. Me too... I didn't even had time to make any new videos. 73 my friend.

@MrTauron77 2 месяца назад

I made a similar transmitter with a wooden box design, but integrated it with the LM386 IC, a Pixie2 oscillator and two buffer transistors.

@dxexplorer 2 месяца назад

How cool hehe. I love these "Frankenstein" constructions. This is what makes them beautiful and unique. Very nice... I want to stick to wood and aluminum combined from now on in most of my builds. Let's see how that will turn out. I miss classic equipment I guess 😁. 73, YO6DXE

@karkuwaa Год назад

Hi I 'm watching your videos for about two months and I must tell your videos are very interested and professional. I want to bulid this TRX but I can't find 7.023 MHz crystal. Can I use 7 MHz crystal instead and where I can find 7.023 MHz. 73!

@dxexplorer Год назад

Thank you for the nice words. Well sharing what I learn.. even if is not much... is a pleasure for me. Hopefully it gets more people into the hobby )). 7 MHz crystal will work... but unfortunately I don't think there will be many signals around that frequency, but you can try as you can replace the crystal any time later on. Instead of 7.023 I would recommend 7.030 as usually that frequency is more used for QRP and QRPP. I usually buy the crystals from a shop here in Romania at RoWaves. But I am sure that on eBay or Amazon and AlliExpress should be available as well.

@karkuwaa Год назад

@@dxexplorer Thanks!

@dxexplorer Год назад

@@karkuwaa Always a pleasure my friend.

@JennyEverywhere 2 месяца назад

How about using the metal can 2N2222 and add a heat sink? I've got a bag of those transistors.

@dxexplorer 2 месяца назад

Those are even better. Or even a 2N2219. Those are bigger and they don't seam to heat up as much as the little 2N2222. If it fits on the board is great 😁. 73, YO6DXE

@lesismologueamateur Год назад

Super ! Best 73. F5NDL Jean-Pierre

@dxexplorer Год назад

Thank you so much. 73, YO6DXE.

@dexterGg-kt2eg 2 месяца назад

Bv. Foarte frumos explicat . Nu am vazut daca cutie de lemn este ecranata in partea de jos.

@dxexplorer 2 месяца назад

Ecranata 100% nu as spune. Dar am lipit pe interior peste tot acea folie de aluminiu de o folosesc instalatorii. Este ca o banda de autocolant. Nu e mare lucru comparat cu o cutie metalica in adevaratul sens, insa vad va isi face treaba. Ma rog... isi facea. Acum Pititico asta este la YO6TJJ cadou asa de amintire 😁. 73, YO6DXE. P.S. Vreau sa fac la fel acum cu Pititico II... varianta de aici de pe canal la care i-am pus si amplificator audio.

@janetwinslow2039 Год назад

Nice project. Maybe add a R/C key-click filter and a capacitor across the audio output to reduce the frequency response a little?

@dxexplorer Год назад

I will need help please on the R/C key click filter ? Is it like a low resistance in parallel with a let's say 100nF capacitor ... in parallel with the key output ? About the audio output... I do want to try that and I had it in mind but didn't do that yet. I will do some changes soon. By the way... the diodes on the audio output to reduce the key click don't seem to do much.. and sometimes the audio level is lower because of them. 73 Janet, YO6DXE.

@dxexplorer Год назад

Excellent.. I will do the mods for the key click on the pititico. I just have to be careful as I believe it will also influence the offset frequency. I must test it anyway. About the Pixie.. I will soon have a version built from scratch. I think you will like it. But I won't say more until I finish it )) Surprise )). I no longer use Facebook but I did find a lot of articles on blogs. Thank you Janet. Time to play this evening and see how good I can get that Pititico to work 😃😃.

@lesismologueamateur Год назад

Good morning ! What is the impedance of the earphone? 8 ohms, 16 ohms, 32 ohms other? Thanks in advance. 73 QRO F5NDL Jean-pierre

@dxexplorer Год назад

If you built it as it was in the original design ( like in this video ) ... PY2OHH recommended a 500 Ohm telephone speaker. I didn't had good results so always used an external audio amplifier. Since then... I decided to modify the schematic and ended up with a new version. Here is the new one I have now. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-sRwcFen1aUs.html

@lesismologueamateur Год назад

@@dxexplorer THANKS! Thanks for the links. 73 QRO F5NDL Jean-Pierre

@dxexplorer Год назад

@lesismologueamateur Always a pleasure 😁

@lakshminarayan6727 2 месяца назад

Very Nice Project

@dxexplorer 2 месяца назад

Thank you. I am working on making one more. 73, YO6DXE

@ssubaihi Год назад

So cute

@dxexplorer Год назад

I made it as a present to my friend YO6TJJ... working on a few more now with the new version... the Pititico II. 73, YO6DXE.

@mikej-38qso22 Год назад

Glad you came back to the El Pititico CW TRX Thx. I watched your video a year ago on the Pititico TRX and you connected a homemade watt meter, can you share the build on that or at least how we can view the schematic? Thank you Mike 73

@dxexplorer Год назад

Actually I am playing to make a video on that one in a week or so )). I just made a little enclosure for it and just waiting for it to dry so I can fit all the stuff inside and make a video about it. Maybe next week before the weekend I will have it posted. I love the Pititico... it helped me understand the simple transceivers like the Pixie and so on. I'm still not wise enough for more complicated schematics when it comes to transceivers )). 73 Mike, YO6DXE.

@petrumanole9684 Год назад

Nice wood box, where did you find it?

@dxexplorer Год назад

Sunt la magazine cu produse de handmade. Sau cele cu suveniruri de multe ori. Se gasesc in tot felul de marimi. Faine tare pentru montaje asa micute ))

@petrumanole9684 Год назад

@@dxexplorer Asa e, multumesc mult! Eu vreu sa bag intr-o carcasa din aia un radio cu reactie cu ECC81-82 la 12V anodica si un mic final cu LM386.

@dxexplorer Год назад

Ohhh da. Cred ca sunt unele si ceva mai mari sa poata intra si condensaror variabil si ce mai trebuie inauntru. Presimt ca iese ceva frumos 😁.

@315_RC_l22 Год назад

Super !👍👍👍

@dxexplorer Год назад

Thank you 😁😁 73

@why.k5max Год назад

Can I use bd139 and 2n2222a instead of 2n3904 transistor? And would the results be the same if possible?

@dxexplorer Год назад

I tried BD139 but there are a few more things that need to be changed in the schematic for it to work. The results were not so great though. 2N2222A is fine yes. I may write something stupid but I can't remember the name... I thinks is 2N3553 that I tested these days and is a little bigger ( metal can ) so It can take some sort of heatsink. I will correct later if I am wrong about the name but I think this is the one. P.S. Have a look at the video with Pititico II. Not much more extra parts... but is nearly a Pixie... with one transistor and an LM386 amp. I like it more.

@why.k5max Год назад

@@dxexplorer Can you explain why I hear this cw frequency on the FM radio scale in the 96mhz and 108mhz frequency range. I use a 12mhz crystal and it emits a number of RF However, I don't have an AM radio yet so I don't know whether it transmits AM or FM waves or neither and keep in mind that in FM mode it sounds quiet, there is no sound Like CW in AM mode in general

@why.k5max Год назад

I also tried it on a 24mhz crystal and the results are still the same it is locked on a 96mhz FM radio but as I said earlier I don't have a radio that can detect AM waves from pititico I created

@dxexplorer Год назад

How far was the transmitter frim the transceiver ? If is close then yes you should hear as there is RF leaking out. The reason why so quiet is because is diferent modulation.

@dxexplorer Год назад

Pititico is transmitting CW. You can still hear it on AM or FM radio but it sounds more like a shadow to say it in not so technical terms. You hear something but not properly. You may hear it on FM radio because is close by and the frequency you are listening may be harmonic of the crystal you are using. 7MHz will also transmit on 14MHz, 21MHz and so on... the further from the fundamental frequency of 7MHz the quieter the signal is. So your 12MHz crystal or 24MHz crystal is also transmitting harmonics on 96MHz.

@SteveHacker 2 месяца назад

Is this available as a kit?

@dxexplorer 2 месяца назад

Unfortunately no. I built it for fun frim stuff I found in the junk box. I do have a PCB design for it available on the blog, or even better the Pititico II that also has the audio amplifier into the circuit as well to make the life easier. Both have articles on the blog. The PCB boards can either be made at home, or ordered from PCBWay. I honestly think is fun to build it from scratch from recovered components. 73, YO6DXE.