Making the Pixie QRP transceiver kit slightly less appalling
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- Опубліковано 14 лип 2024
- The Pixie QRP transceiver kit is super-cheap but comes with some performance compromises. This video discusses crystal and ceramic resonator VXO circuits to add frequency agility and make contacts easier. Coverage of the SSB portion of the band also makes it an attractive receiver costing under $20 for the kit plus extra parts needed.Source for 7.16 MHz ceramic resonator: www.minikits.com.au/
Contents:
0:00 Introduction
0:45 Switching in a second crystal
1:34 Add variable capacitor to pull crystal's frequency
2:57 Add ceramic resonator for even more frequency agility
3:55 Switchable crystal and ceramic resonator
4:24 Overcoming a certain problem
7:19 Receiving demonstration
7:40 Crossmode with SSB stations and frequency offset
10:58 Summary
If you want to buy rather than build your Pixie you can do so via this link: ebay.us/bDuyja (Note: I receive a small commission on sales at no extra cost to you)
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(then if you buy something I'll get a small commission at no cost to you) - Наука та технологія
Your switching solution around 7 mins in was Brilliant! I was puzzling it out right along with your narration and didn't see that solution coming.
Hello from Spokane WA , I am studying for my Technician test and I had come across the Pixie for listening to Morse Code and I came across your smart and informative videos. I think I will purchase the Pixie and make these modifications. Thank You.
Thank you and good luck!
I used this switching arrangement on my DC Chocolate box receiver which now lets me listen to SSB and CW bits of the 80M band. Thanks!
Thanks for taking the time to make the mods, and video the performance. I'll be taking notes and experiment with mine.
Thank you for the very informative video. Must have taken a while to put it together. That aside, your persistence with the experiments and the logical approach is excellent, especially since , in essence, its hardly worthwhile messing with the little thing. I think many people who build this kit can easily be disappointed but as your video shows, stick with it, mess with it and you can end up with something worth more than the cumulative parts. Well done
Props for the cheeky video title! "Slightly less appalling" is a great phrase for anything that relates to this kit.
years ago I built a trixie transceiver that was basically a pixie with a keyer circuit and a little better audio amp. I modified it into an AM phone transceiver. It was fun to play with but ended up in the junk drawer. For $30 dollars more get the QRP Labs QCX+.
Nice Video showing how easy to expand the Pixie. The VXO mod with inductor works well for expanded tuning.
Jay - Adding 2 crystals of the same Freq. in parallel will allow the VXO to pull even further.
Made a 4-way Pixie switch PCB & will have pics out soon on my web site. Too much fun to be had with these little rigs.
73 & thanks for the video! kc9on
Thanks Peter for sharing your experiences. Regards. LU1AR
Brings back some memories. I built one of these years ago made from junk box parts built into a tobacco tin. I still have it lying around. Would be interesting to try the mods with the ceramic resonator, if nothing else it would be a little DC receiver with a much wider range of reception. I would like to see how it receives the SSB stations. Some great ideas Peter, enjoyed the video M0DAD
Great vid Peter
The real mod is going to be adding a preselector with a narrow Q. This would prevent the overloading unless the overloader is right on top of your frequency. Great video, 73 de W6EL
Thanks for your great jobs dear OM !
I learn a lot of things with your videos.
73, Joseph f1pfc.
I love this! I heard you on the Soldersmoke podcast and decided to look here! Cheers from East Tennessee! BTW, my sister-in-law is from Perth. WA4OKO
I just got mine and am looking forward to building it. I plan to put a socket in place of the crystal so I can put any crystal I like into it.
I have build a pixie 2 from junk box parts this weekend. It is easy to replace the coil in the LP filter 80m 2.2 uH and 40m 1 uH. This is all you have to do. I found the pixie is working better on 80m. A good antenna is important for QRP work, a dipole or better. With two 2N2222 transistors I have about 250mW output. A modification to have offset is a must to get a practical transceiver I have a little 60 pF trimmer in my pixie from the Xtal to ground, a switch is parallel to the trimmer. The clicking of the audio stage during transmitting is rude to my ears, a little loudspeaker is much better. I avoid headphones with this transceiver. Ask your friends for some Xtals, most hams have a box with Xtals at home. If you are on a budget use the wire of an old transformer to cut a dipole, fishing line will fix it between to trees as high as possible. You have to buy a BNC connector and a few meters of feed line. The key to QSOs is a good CW operator not so much the gear used. 73
i got a pixie like this and just built it stock, i put a header in where the crystal goes for fast swaps...
I'm working on a 2nd Pixie, leaving off the oscillator section and using an AD9850 DDS to produce whatever frequency I need. I realize that increases cost but does increase the fun. lol At the very least helps me to understand all this and how to improve on what's there and build on it.
I'd go with something a bit better , i'm on with the same project and going with the frog sounds / forty 9er circuit , going to push for 3 watts out, i'd look to put a filter and the front end of the pixie if i ran with that as it's a bit wide open
NICE TUTORIAL VERY USEFUL
I built one of these in the mid 2000’s and modified it to use a VFO kit made by WA6OTP. It made it a lot more versatile. He’s no longer building kits from what I can tell but the schematic and some pictures are available on his site. It uses a small threaded brass rod and a hand turned coil around it to tune a 200k+ kHz. I had some issues with stability at first and sorted them out. Still had some common pixie issues but was fun to tune around and not be stuck to a crystal.
Great work and improvement on this kit and presentation. Can you look at Frog Sounds QRP Kit as well?
Frog sounds is virtually identical to the forty 9er , have a look at the Arduino AD9850 VFO project , it's what i'm in progress with building now, you can get the parts really cheap from eBay and you get a full VFO with digital read out, far better then a VXO. de G0KVL.
Hello Peter! Great presentation, as always. Clear, great information value, super understandable English! I built some Pixies in the past, they worked fine but i'd like to build a "talking Pixie". I never tried this one on the Internet (well known under the talking Pixie name), because i am not sure that it would work. I do not expect ssb, or even dsb, but with some linearity maybe it would be possible to transmitt some AM. Do you have any idea how to modify a Pixie to get this feature? vy 73's de gabriel-db5ag
Peter, does the ceramic resonator cover 7.100 to 7.120? These are popular slow speed cw frequencies in the US.
Best informative video and also your modification would help new ham cheer up but unfortunately we can't get tuning capacitor of radio in this era we need to remove from old radios or brew one and xtal occilator for 7mhz is also a thing here
great job thanks
good project
I got two of these really cheap. (Like $10 shipped) Going to try and replace the Crystal based LO with a signal generator and use it SSB reception on the cheap. I have also been staring at its design to think up how to make it transmit AM. (As that is way easier then SSB.) I think if I can abuse the amplifier circuit in it to do so.
Anyone know where to get the ceramic resonator in the U.S.?
Good video 73 from baghdad de Yi1hxh .
That's really interesting Peter, I hadn't realised that a ceramic resonator could be pulled as far as that. I don't have a pixie but I might need to try this! Best 73 de Alan G0NFY
VERY NICE CIDEI. THANKS A LOT !Forgive me my ignorance. But I bought an rtl sdr. It of course can't listen to short waves. But I also bought a 125MHz upconverter . And I still can't hear anything. I bet it's the antenna. How could I build a small antenna to listen to see?
I would suggest a good sized antenna like a single band coax fed dipole on a popular band like 7 MHz to start off with. A small antenna like a magnetic loop may work but needs adjusting every time you significantly change frequency.
How about and Arduino DDS ?? What would it take ? I've also seen these modified for AM, AM with DDS anyone? Thanks for all the great videos ! KB8OOE
One mod I'd like to make is change to 20 meters (14.000-14.150 or so). I have the crystal, but I'll have to change the low-pass filter. Maybe the 22 uH inductor as well? Has anyone done this?
Shouldn't need to change the 22uH. You may have issues with poor receiver sensitivity. I find 20m a very difficult band for QRP, especially if you're not frequency agile. Do it by all means but don't expect many contacts.
When you talk about overloading the front-end. What exactly do you mean? Could you elaborate on that and possibly how to fix it?
the pixie has no filtering to stop broadcast and other strong stations coming through , if i had a pixie i would put a filter circuit in line where the signals go into the NE 612 chip (pin1) there are lots of examples about just a L C circuit , looks to be either a low pass or a band pass filter
my daughter just finished hers, it started to smoke haha :-) we will get another one and keep attempting until we get it right? i notice it seemed to be reverse when keyed it did not transmit when not keyed it transmitted then it started to smoke, any ideas :-)
Nice video as always Peter, thanks. If I put an small inductor between the crystal and the variable capacitor to get a wider range what should it's value be?
Hard to say. It will vary depending on crystal. Several in series may work better than one. Could be between about 1 and about 20 uH worth.
@@vk3ye Thanks Peter, I bought 3 of these kits so I will give it a go. Enough toroids and wire so time for some serious experimenting. ;-) I intend to try your AM mod as well.
How much does the frequency of a quartz crystal change? Up or down?
can you run multiple crystals together and make a 3rd freq? (in series)
+Jay Mee No. Better to switch them.
How does the variable capacitor work with the onboard trimmer pot to tune?
The variable capacitor provides a much bigger frequency range. The onboard trimmer adjusts the cw tx/rx offset. You may need to adjust it to provide the right amount (1 kHz) though note that shift will vary a lot over the tuning range. One of the many compromises!
Hmm i was thinking. What if i have a rotary switch with 6 pol and have 6 capacitors in series with it. Would it be usable as a channel selector like chn1 to 6.
Yes that could work.
I'm going to mod mine similar to the way you did yours. I was wondering what your best distance on contacts has been with the Pixie? 73 de KK6IQK - Jon
I found that adding 3 different ceramic resonators, (they cost next to nothing,) and a tuning cap for frequency agility, building band pass filters, an RF driver stage and a push-pull IRF510 output amp with low-pass filter, then running the amp on about 22 to 26 volts from a pack of old laptop 18650's solves the problem of not being heard. Folks tell me my CW note doesn't sound very clean. But I just explain that I'm running a Pixie. I figure they couldn't tell me that if they didn't hear it, so problem solved.
What does the 10-200 on the variable capacitor mean?
Its range - ie 10 to 200pF. Not that critical - ie 160pF maximum would be fine.
What can you do to limit broadcast AM interference? I hear that alone can ruin pixie performance. Thanks!
I used a magnetic loop antenna. 8m circumference makes for a loop size that 2.7m lengths of timber can be used to keep it in place. I used 1” wide 1/16” thin flat aluminium bar stock. 2 x 4m lengths. Decent efficiency with an appropriate capacitor
Being a resonant narrow band antenna. It naturally rejects stuff that outside the 20-50KHz you get.
Hi Peter, I have severel cheramic resonator 7,16MHz. Can i put these in parallel or in serie to cover other bands? /Isak
No.
Where did you get the ceramic resonator from ? I've been looking on eBay but no luck, lots of 4,6,8mhz ones but no 7mhz
www.minikits.com.au/ had them last time I checked
www.ebay.com/itm/5PCS-3-Pin-Ceramic-Resonators-use-in-oscillator-circuits-select-freq-from-menu/223555023467?hash=item340ceaf26b:m:mwN5tbJsW32mxjUe5viaF2Q
KITS! whoot, now I'm on board. Or at least bought some boards and components. KITS if you don't like it--fix it. A physical/electronic version of what you can do with Linux! (if you're coding-inclined, or can apply patches). My Pixie is in the mail, and I've a uBitx as well.
Have you tried the LM386 pin-7 mod suggested by LA3ZA to overcome some Pixie rx shortcomings? He describes the mod for the Pixie here: la3za.blogspot.co.uk/2003/04/using-pin-7-of-lm386-to-reduce-bci-and.html
I'm about to assemble my kit, but wondered if it's worth doing this mod as I assemble the kit, or try it after! Thanks.
Hi, please PCB Thanks
Mine just dosent work
Check out the simple mods by LA3ZA to reduce the broadcast breakthrough. It just moves D3 to keying line and pin7 and considerably reduces value of R3. Also 47uF pin7 to ground helps.
la3za.blogspot.com/2003/04/using-pin-7-of-lm386-to-reduce-bci-and.html
I've also added 10n across the headphones to reduce the very wide audio bandwidth, and also two back-to-back silicon diodes (1N4148) to minimise keying clunks.
(They are still very basic kits of limited use!)
HI this is VU3YWB
by mistake I ordered this kit online actually I want 40 m tarns receiver kit ...this kit is not useful for me..If anybody wants I am ready to dispatch as it is
Nice video de Yi1hxh
visiting ant at 0m47s
find the best way to fix a pixie
use a rock to smash it in to little pieces