10 Mt Band mods and fix for old Kanga Kits Oscillator / VFO - UK Vintage Radio Repair and Restoration Discussion Forum

Malcolm T · 4th Apr 2023, 12:57 pm

I am looking for a simple Osc / VFO Circuit for QRP / experimentation in the 10 Mt band , there are many circuits for 80 and 40 etc but not as many for 10 Mts.
Transistor circuits preferred. 1 - 2 Watt o/p would be nice .
Can anyone help here please.
I have the remnants of a complete Kanga kit here , it hasn't been out of the project box for 20 odd years and want to get it finished and working on 10 Mts All the other boards are finished but the previous owner had difficulty in getting any RF from the TX output.
I have the Five boards, one of them is already in the baccy tin but no circuit diagrams either,
havnt a clue where they went too !
Any help appreciated as i want to have a bash at 10 Mts /P

Cruisin Marine · 4th Apr 2023, 7:43 pm

The QRP notebook is an excellent read and should give you great inspiration, even if you have to scale component values from say 20 metres to 10 metres. There is a design called the 'lil slugger" in the book for 10 metres, all that you would have to do is design a VFO/ buffers to replace the Xtal osc.
The book is available for download for free if you look.
There is also info on Colpitts VFO's for any frequency.

Malcolm T · 4th Apr 2023, 8:11 pm

Thanks for that , i have never seen that book before.

Radio Wrangler · 4th Apr 2023, 9:08 pm

28MHz is quite high for a VFO if you want good stability. You'd expect drift to increase pro-rata, but it's a bit worse than that.

Good components, mechanically speaking, help a lot.

George Burt, GM3OXX had a transceiver based on a 28MHz unit with band transverters for all the other bands. He used a gearbox and variable capacitor and coil former robbed from a BC221 wavemeter. I used his rig back in the eighties and it was superb. George worked far over 300 countries with 1 watt output using this.

David

Cruisin Marine · 4th Apr 2023, 9:32 pm

It is much easier to accomplish a stable VFO if you stay on one of the QRP frequencies of 28.060 CW, 28.885 SSB and 28.110 Novice?, as listed in my hard copy of the aforementioned book. By restricting the VFO range.
I have found temperature drift to be the biggest problem in the past.
I even made a VFO "oven" with a comparator and some heating resistors and a sensing thermistor from distant memory.
But the simple addition of a few warm baking/heating resistors/bulbs works pretty well, you still have to allow quite some warm up time though.

Most of that I think is covered in the book from memory.

4th Apr 2023, 12:57 pm	#1
Malcolm T Hexode Join Date: Dec 2018 Location: Lugo, Spain Posts: 483	10 Mt Band mods and fix for old Kanga Kits Oscillator / VFO I am looking for a simple Osc / VFO Circuit for QRP / experimentation in the 10 Mt band , there are many circuits for 80 and 40 etc but not as many for 10 Mts. Transistor circuits preferred. 1 - 2 Watt o/p would be nice . Can anyone help here please. I have the remnants of a complete Kanga kit here , it hasn't been out of the project box for 20 odd years and want to get it finished and working on 10 Mts All the other boards are finished but the previous owner had difficulty in getting any RF from the TX output. I have the Five boards, one of them is already in the baccy tin but no circuit diagrams either, havnt a clue where they went too ! Any help appreciated as i want to have a bash at 10 Mts /P

4th Apr 2023, 7:43 pm	#2
Cruisin Marine Heptode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 994	Re: 10 Mt Band mods and fix for old Kanga Kits Oscillator / VFO The QRP notebook is an excellent read and should give you great inspiration, even if you have to scale component values from say 20 metres to 10 metres. There is a design called the 'lil slugger" in the book for 10 metres, all that you would have to do is design a VFO/ buffers to replace the Xtal osc. The book is available for download for free if you look. There is also info on Colpitts VFO's for any frequency. __________________ "Behind every crowd, there's a silver Moonshine" Last edited by Cruisin Marine; 4th Apr 2023 at 8:00 pm.

4th Apr 2023, 8:11 pm	#3
Malcolm T Hexode Join Date: Dec 2018 Location: Lugo, Spain Posts: 483	Re: 10 Mt Band mods and fix for old Kanga Kits Oscillator / VFO Thanks for that , i have never seen that book before.

4th Apr 2023, 9:08 pm	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,876	Re: 10 Mt Band mods and fix for old Kanga Kits Oscillator / VFO 28MHz is quite high for a VFO if you want good stability. You'd expect drift to increase pro-rata, but it's a bit worse than that. Good components, mechanically speaking, help a lot. George Burt, GM3OXX had a transceiver based on a 28MHz unit with band transverters for all the other bands. He used a gearbox and variable capacitor and coil former robbed from a BC221 wavemeter. I used his rig back in the eighties and it was superb. George worked far over 300 countries with 1 watt output using this. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

4th Apr 2023, 9:32 pm	#5
Cruisin Marine Heptode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 994	Re: 10 Mt Band mods and fix for old Kanga Kits Oscillator / VFO It is much easier to accomplish a stable VFO if you stay on one of the QRP frequencies of 28.060 CW, 28.885 SSB and 28.110 Novice?, as listed in my hard copy of the aforementioned book. By restricting the VFO range. I have found temperature drift to be the biggest problem in the past. I even made a VFO "oven" with a comparator and some heating resistors and a sensing thermistor from distant memory. But the simple addition of a few warm baking/heating resistors/bulbs works pretty well, you still have to allow quite some warm up time though. Most of that I think is covered in the book from memory. __________________ "Behind every crowd, there's a silver Moonshine" Last edited by Cruisin Marine; 4th Apr 2023 at 9:55 pm.