A 10 minute 7 MHz QRP transmitter and more

[@Steve-GM0HUU]

I finished building one of these last night. Exactly as per your diagram. Built mine ugly style on copper clad PCB. I settled on 450pF coupling capacitor between oscillator and PA. Fitted with 7023 and 7030KHz crystals and get about 1KHz swing. 5W out. Managed to work a couple of stations this afternoon. Just need to find a suitable tin to house it and see if I can make a simple 40m RX to go with it. So, certainly works and thanks again for video Peter which inspired me to build this.

[@aqdrobert]

Friend was out of fuel on a forestry road. He used a transmitter like this, a barbed wire fence for a random wire antenna, and his vehicle as an earth ground. Got help from hundreds of miles away. Local authorities arrived with fuel.

[@stewartdahamman]

@aqdrobert Now that's impressive!

[@xanderlewis]

Cool! I wonder what he transmitted, and to whom.

[@aqdrobert]

@@xanderlewis He sent SOS, received a reply from California. Ham relayed message to Gila County Sheriff in Arizona via phone.

[@m0dad]

I remember building this transmitter Peter, it also appeared in other journals. The fun simple projects are the best in my book. Its great to see what can be done with minimal parts. 73 de M0DAD David.

[@derekdowns6275]

Thank you, Peter Parker. It's good to see someone carry on in the grand tradition, instead of babbling on about the latest Chinesium HT.

[@ats-3693]

Meanwhile the components used were most probably made in China.

[@mikevk4qs]

Fantastic Work Peter, I'd love to build one. You always embrace the true Spirit of Amateur Radio, Well done!!, Cheers Mike VK4QS.

[@kq6up]

The nice thing about this rig is the chirp seems to attract attention and CW QSO's. I replaced the HC-49 that I initially installed with an FT-243 socket. It still chirps like a guinnie pig being strangled, but at least it stays on frequency now. A lot of fun to use. Just going to have to build a matching little regen.

[@Steve-GM0HUU]

Good point about the chirp. I have also wondered if ops are more likely to reply to chirppie CQs as they know it will probably be homebrew QRP TX. I generally try to reply to any CQ if I can but always make a bit if extra effort if it's a chirppie.

[@propagating-radio]

Well now I need to build this too! Great video! Thanks for sharing.

[@52Warlock]

Thank you - well done. Quite enjoy seeing/hearing how you think and solve problems.

[@dxexplorer]

Nice and simple transmitter project. For sure is on my to do list of things to try hehehe. Thanks Peter... 73 and greetings from Transylvania.

[@IvanPassos]

Excelent QRP Peter

[@Steve-GM0HUU]

👍Interesting projects Peter and thanks for sharing.

[@SierraEcho]

Incredible and simple project! Congratulation!

[@joohop]

Nice Work Earthling Bless Up

[@hamradioqrper6554]

I like so much when chirps and now I prefer that with a light reverb .. 👌😎

[@Broken_Yugo]

Funny you should mention those 1000pf trimmers are rare (and expensive!) now. I was just learning that, having made the dumb move of cleaning one with compressed air and blowing too much of the magic mica glitter out.

[@jerryuhte1284]

Peter , another great article , congrats om , 73 Jerry K9UT

[@leonardoelias22]

it would be nice to insert AM modulation on it and change the crystal to AM band

[@leonardoelias22]

5W AM modulation on 40m or 80m with this easy circuit... :o

[@N_Andrews]

I have seen a 2x2n2222 into IRF510 circuit with audio inserted at the second 2n2222 and produced 5w with good audio. The transmitter was used by US Shortwave pirate Liquid Radio and logged all over the USA.

[@101blog]

Fun project Peter thanks for building it ...Is that a Kangaroo on the box ?? If so does it improve SKIPpy distance ?? Hava good un!

[@Paul_VK3HN]

Yes it should do multi-hop really well.

[@davkdavk]

Haha!

[@amerkamenica6998]

Hello from Bosnia Peter very nice

[@edbeckerich3737]

Many thanks!! Great video!!

[@suleymandavudsargon9576]

I prepared this circuit and it worked fine, but it crashed after 10 minutes. I used 2222 instead of Bfy51. I have no idea what it is yet. I was powering it with a 12v battery.

[@Tocsin-Bang]

Just seen this in the latest issue of Sprat. I think I have all the parts, so maybe time to warm up the soldering iron!

[@munichman1968]

Very nice transmitter, Peter!! Thumbs up!! 73 de DG1MJH, Roberto

[@soldadodecristo9254]

Gracias por compartir

[@joeblow8593]

Excellent

[@ThiagoPaes_mrprompt]

Really cool!

[@michaelrobertson575]

Interesting! So it's a Pierce Oscillator onto which you've put an Output Stage and the Filtering on the output is a nice touch. I don't know if you get Practical Wireless out there but it reminds me of the work of the late Reverend Dobbs. Just out of curiosity is there any interest in this hobby shown by the Aboriginal People?

[@vk3ye]

You used to see PW in the newsagents here. I do get Sprat. Oscillator based on a design from that. Not aware of high Aboriginal participation in AR.

[@jasonsnyder9394]

Great work. I am in the process of putting together this kit, but wanted to ask what type of capacitor are the silver one part of the low past filter? Can one use regular disk ceramic caps for these? Keep up the great videos!

[@paulschmolke188]

Interested to see a final schematic if you have one you can post. Pretty cool little XM tar. KE5TJ.

[@py5lgpaulosergioabarroso266]

Is there any way to make a VXO in place of this oscillator crystal to be able to change the frequency?

[@vk3ye]

Via the series variable capacitor, this circuit already has a VXO. You could try adding series inductance for more range but you might get more chirp.

[@davidnunkt4751]

I think in the first version without pa mosfet you can add an high z earphone in parallel to 100n to get a trx :)

[@vk3ye]

Yes. G3XBM has some designs. Very low audio level though so an extra transistor or two is highly desirable.

[@sevdetyavuz4271]

when we make an amateur CW call on the air, we use "CQ" instead of "V". "V" is used for professional communications. VA3ESV

[@vk3ye]

Sending a series of Vs is customary when testing equipment and a reply is not expected and may not be answered. CQ is used when seeking a reply.

[@wohlsson]

Nice work Peter...my first try on a bread board and it worked perfect though it took me all day to put it together. What changes other than the crystal to put it on 20 or 80...tried a 20m crystal but output was only about 1 watt.

[@vk3ye]

The big change is the pi network output filter. If that's at too low a frequency you won't get much output. Also you might expect some drop off in output power with increasing frequency.

[@bill-2018]

The BD139 is normally used in audio circuits so it's pushing it to expect any more on 20m. G4GHB.

[@dm.2023]

That's pretty neat. 700km is quite impressive! 4:16 Is that a duck in the background?

[@vk3ye]

One of these kzbin.info/www/bejne/haqQZq13qaagkKc

[@mohammadalfauomey3443]

Please: 1 : What is the meaning of " QRP" ? 2 : The "10 minutes " is the time of what ? Thanks very much .

[@vk3ye]

1. QRP is low power amateur radio. 2. 10 min is the time in which you might be able to build the transmitter (if you're quick).

[@mohammadalfauomey3443]

@@vk3ye Thanks very much sir .

[@hthring]

How come in the first power meter reading you read off "2" as 200mw but then after adding the amplifier you read of "8" as 8 watts ??

[@vk3ye]

Hayden - the meter has two ranges. 2w & 20w.

[@jeromegrzelak8236]

@@vk3ye do we have a circuit for the power meter om kg6mn

[@juancamps8961]

Could i use this tx with a 20m half wave end fed wire without using any antenna couplers? Just the wire straight to the output. Sorry for my bad English and thank you.

[@vk3ye]

No. The 20m of wire fed at the end will be high impedance. If you don't want a coupler the wire must be fed in the middle with coax as a half wave dipole.

[@juancamps8961]

Thank you, i have another question. Have you ever build this kind of circuits inside an ATX PC Power supply case? Did it give good results?

[@vk3ye]

@@juancamps8961 Any metal case would be OK.

[@southernexposure123]

Thanks for the videos. I've watched a lot of them. I have good audio on thise one. Others are low audio. I have a neophyte question which will make me sound like a novice. I'm looking at the low pass filter. I wonder IF one coil canbe used by center tapping the coil and leaving the capacitors as they are designated. I suspect it won't work because the coil turns will couple. Am I right? I suspect if could be done as I asked about that builders would have imlemented that already. Thank you. Edited to say on the next of your videos I watched I saw a 4:1 transformer that was almost the same thing I described and asked about in this comment. The difference is the bifillar wires of the 4:1 transformer are twisted instead of parallel wound. That video is 20 watts not qrp. Again, thank you for your videos.

[@vk3ye]

You're right re the single coil. I wouldn't do it.

[@southernexposure123]

@@vk3ye Thank you. I'm making a shopping list for qrp VFOs based on schematics of the Wes Hayward era. Some of the parts are listed "obsolete" but they're still available from sources other than the usual makers.

[@kj7mmc]

Just wanted to say, thank you for your videos. kj7mmc

[@johnkemas7344]

HI Hi VK3YE Nice little project! Have you considered replacing the crystal with a VFO say an Arduino based VFO or similar?? Could be a nice touch to a fairly powerful unit for its size.

[@DavidALovingMPF102]

For the USA hobby guys, Electronic Goldmine has most of the parts for this project.

[@MarkPentler]

If I wanted to use the output of a DDS instead of a crystal do I just take out the crystal and the variable capacitor? Connect the +ve clock output at the top with the collector and the ground to the base?

[@vk3ye]

In theory yes but you need to make sure levels and impedances are matched. The output would be coupled to the base.

[@MarkPentler]

@@vk3ye I did later find the answer, namely connecting to base. Trying to go the Arduino/Si5351a route with a VFO.

[@msnepaliman]

HI! It is so.... interesting! I cannot get RF transistor or genuine MOSFET here. Can I use MRF620 or MRF630 similar MOSFET as RF amp there?

[@vk3ye]

I don't know those transistors but I suggest you try it anyway.

[@johnrees44..G4EIJ]

Excellent Peter..A great video with a clear, informative explanation..Thank you.. Am I right in thinking that the circuit could be easily adapted for 14mHz? Cheers..John ..G4EIJ

[@vk3ye]

John, it may work on 14 MHz, but 1. Gain will drop off and 2. 14 MHz is a terrible band for crystal control. You really need all CW band coverage.

[@johnrees44..G4EIJ]

Thank you for your advice, Peter..I’ll think again.. Please keep making the videos.. I’m an ‘old timer’, and I miss the ‘home brew’ days of a few decades ago.. It’s great to see someone keeping that aspect of ham radio alive..Thank you again.. John.. G4EIJ.. UK

[@matthalsey387]

I would think 60m would be a good candidate as the CW channel freq's are already locked down. Have you made any xtal Tx for 60?

[@vk3ye]

I started one when it looked like we would get 60m as I already had a suitable crystal. But VK & ZL authorities have rejected amateur access to 60m due to defence usage so it's not happening any time soon.

[@matthalsey387]

@@vk3ye Wanna sell the xtal?

[@soldadodecristo9254]

Saludos desde santiago de chile 73

[@pallabsikder3626]

can I make the transmitter with 11.059 mhz crystal

[@vk3ye]

It might work but you'd need to change low pass filter components. And it would be illegal as it's out of the amateur band.

[@khalidtarawneh2289]

you mean 800mW afret the IRF510 not 8W QSL?

[@vk3ye]

Sorry I don't understand your question.

[@khalidtarawneh2289]

@@vk3ye at minute 2:00 you said you're getting around 200mw output when the meter pointed at around 2. Then after adding the irf510 on the same meter when it was pointing at 8 you say it's 8W. I thought since it's on the same meter it would be reading 800mw and not 8W. Plz clarify thnx and sorry for confusion

[@vk3ye]

@@khalidtarawneh2289 The meter has two maximum power ranges and a switch to switch between the two.

[@SunilAruldas]

I was about to make a similar observation, but the matters cleared up now

[@whitefordpipeshandmadebymi7238]

Pretty cool experiment I wonder what would have to be modified to get it for 80m ? Anyway enjoyed watching ! 73 de ve3hip in Welland Ontario Canada 🇨🇦

[@vk3ye]

80m would just need a different crystal and a scaled-up pi-network low pass filter.

[@Paul_VK3HN]

Fun project. What power diid you get from the IRF510? Its a good time for simple transmitter projects. With Kiwisdrs Reverse Beacon and WSPRNet who needs a receiver?

[@vk3ye]

Paul - 8w max.

[@Dazzwidd]

I think that the IRF520 and IRF530 would be great candidates for more output at these low frequencies but more output would be required from the oscillator so a single BD139 as a driver would be good. The oscillator could also be run lighter to get only 50mW for the driver. With 1 to 1.5W driving the FET, 25W may be seen with an IRF530 I believe

[@Paul_VK3HN]

@@Dazzwidd It's pretty good value from three transistors worth $3 in total. The IRF530 could tolerate a higher drain voltage, maybe 24V safely. just heatsink it well. This configuration reminds me of the MOPA or two-valve crystal CW transmitters of yore, about the simplest and best performing homebrew transmitter that could be built, typically comprised of a pentode as oscillator driving a serious PA tube such as a 6146 or even an 813 for 50 to 150 watts carrier. And a real coffee-table show-piece too, the power tube glowing all infra-blue with each key-down...

[@vk3ye]

@@Dazzwidd I think the main thing needed would be higher voltage. Eg 25-30v. The IRF510 might even do 20w with that. I'd also be wanting to check that impedance matching between osc and PA was OK - I suspect there's a mismatch.

[@Dazzwidd]

@@vk3ye a major thing is the gate capacitance when you're dealing with fets, but yes there would be mismatch. In the case of your circuit the 470p coupling capacitor would be acting as a voltage divider with the gate capacitance. The inductor in the oscillators collector is an interesting question concerning it's resonant frequency with this divider across it

[@101blog]

I forgot to ask about this thing of using the minimum number of transistors. All this stuff is fine back when transistors were expensive but now they are cheaper than the caps wouldn't you be better off using using a few more and gett a nicer result say by buffering the oscillator stage for example?!

[@Dazzwidd]

ease of construction and the beauty of simplicity: doing more with less. However if a much more versatile transmitter was wanted, a intermediary stage between the oscillator and amplifier would be good. That way it could have ports to be able to apply modulation to the driver/buffer and final. In this way it could be changed to an am transmitter OR used as a CW transmitter

[@vk3ye]

@@Dazzwidd True. But crystal controlled AM is pretty useless in terms of getting contacts. On a contacts per transistor basis CW is much better. A basic DSB rig that was frequency agile (like the Beach 40) would also be excellent. But I do have an AM rig along these lines described here: kzbin.info/www/bejne/fanZZHdvZ5KdiZY

[@101blog]

@@vk3ye Hi Peter, I understand the points made .. I was more about the fact that now you can buy a transistor for a penny a pop which are perfectly functional at HF why are folk quite willing to use extra Caps/resistors /inductors etc but they baulk at a transistor which may well be cheaper ... I agree minimalism may well be an art but 5 descretes and not more minimal than 1 transistor say. A maximal transistor build would be quite fun in that case!

[@ObamaoZedong]

Does a variable capacitor affect performance or could you theoretically add say dozens of them to get a much wider frequency range?

[@antenaseinterfacescb]

Could I use this project to build on 27 MHz tks.

[@vk3ye]

Not easily. Transistor gain drops off with frequency. And you would need an overtone xtal osc circuit.

[@antenaseinterfacescb]

@@vk3ye tks 7351.

[@georgelstuart]

optimization took a lot longer than 10 minutes eh

[@jeromegrzelak8236]

sweet kg6mn

[@godohembon]

Awesome...What kind antenna did you use for this TX? How high ?

[@vk3ye]

g5RV. 10m up at apex.

[@awaismushtaq5719]

It's just a Pierce oscillator. And it's not cool. It's dirty! And I have never seen a 1000 pF capacity variable capacitor