40Metre SSB exciter.... Needs PA.. - UK Vintage Radio Repair and Restoration Discussion Forum

Wendymott · 29th Jul 2016, 6:13 pm

Hi Peeps. I am at a "cross roads"...Using various circuits I have cobbled together a... I think .. reasonable 40m SSB Exciter... however... the PA design is giving me a problem.. in as much.. I cannot find a decent FET type linear with good inductor info. All the circuits I have found, except a couple of French ones, do not specify the Toroid or Ferrite , winding data etc..The intention was to use two IRF510's in series.... but the inductors are a problem. The pre driver uses a 2N2222, and I guessed at the collector Bi Filar toroid, using a binocular type with 7 turns of 34swg or 0.016mm... However the IRF510's are more powerful and would obviously need bigger toroids or ferrites and heavier gauge wires.. its the turn ratio I have no idea about... is it experimental ??
I attach the schematics I have up to now.
It would be a great help from the members to suggest inductors or an alternative circuit.
Thanks in antisiptaion

Wendymott · 29th Jul 2016, 6:41 pm

Sorry peeps I forgot the schematics

G8HQP Dave · 29th Jul 2016, 9:33 pm

I think the thing to remember is that typically an FET gate looks like a capacitor with some resistance in series. Miller effect will add extra capacitance (and this may be signal level dependent). At a fixed frequency you can transform the impedance to a capacitance with resistance in parallel.

Jon_G4MDC · 3rd Aug 2016, 11:04 pm

Not sure how much power you are looking for but the Cirkit 20W PA using CB bipolar transistors did me very well some time ago. Assuming it's still possible to get info and the parts.

I don't quite remember the origin of Cirkit. Believe they had a shop in Broxbourne in 90's - now it's a housing estate / flats -or??
Sad,

Radio Wrangler · 4th Aug 2016, 7:33 am

The Cirkit kit with the CB power transistors was by a guy called Chris Honey if I remember rightly.

It worked well. I used one on the end of a Redifon GK203 exciter, with a homebrew bank of lowpass filters. I think George Dobbs has it now.

David

G8HQP Dave · 4th Aug 2016, 12:16 pm

Cirkit started as Ambit International - Bill Poel. I believe there was a connection with something called Amateur Radio Bulk Buying group.

Jon_G4MDC · 5th Aug 2016, 11:41 am

Thanks - that's the one.

5th Aug 2016, 11:55 am

One of these http://www.ebay.co.uk/itm/DIY-KITS-4...item4d3ac91264 may do the trick.

Wendymott · 5th Aug 2016, 1:38 pm

Thanks Melin.. ordered..

29th Jul 2016, 6:13 pm	#1
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	40Metre SSB exciter.... Needs PA.. Hi Peeps. I am at a "cross roads"...Using various circuits I have cobbled together a... I think .. reasonable 40m SSB Exciter... however... the PA design is giving me a problem.. in as much.. I cannot find a decent FET type linear with good inductor info. All the circuits I have found, except a couple of French ones, do not specify the Toroid or Ferrite , winding data etc..The intention was to use two IRF510's in series.... but the inductors are a problem. The pre driver uses a 2N2222, and I guessed at the collector Bi Filar toroid, using a binocular type with 7 turns of 34swg or 0.016mm... However the IRF510's are more powerful and would obviously need bigger toroids or ferrites and heavier gauge wires.. its the turn ratio I have no idea about... is it experimental ?? I attach the schematics I have up to now. It would be a great help from the members to suggest inductors or an alternative circuit. Thanks in antisiptaion __________________ Should get out more. Regards Wendy G8BZY

29th Jul 2016, 6:41 pm	#2
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: 40Metre SSB exciter.... Needs PA.. Sorry peeps I forgot the schematics Attached Thumbnails __________________ Should get out more. Regards Wendy G8BZY

29th Jul 2016, 9:33 pm	#3
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: 40Metre SSB exciter.... Needs PA.. I think the thing to remember is that typically an FET gate looks like a capacitor with some resistance in series. Miller effect will add extra capacitance (and this may be signal level dependent). At a fixed frequency you can transform the impedance to a capacitance with resistance in parallel.

3rd Aug 2016, 11:04 pm	#4
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: 40Metre SSB exciter.... Needs PA.. Not sure how much power you are looking for but the Cirkit 20W PA using CB bipolar transistors did me very well some time ago. Assuming it's still possible to get info and the parts. I don't quite remember the origin of Cirkit. Believe they had a shop in Broxbourne in 90's - now it's a housing estate / flats -or?? Sad,

4th Aug 2016, 7:33 am	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,901	Re: 40Metre SSB exciter.... Needs PA.. The Cirkit kit with the CB power transistors was by a guy called Chris Honey if I remember rightly. It worked well. I used one on the end of a Redifon GK203 exciter, with a homebrew bank of lowpass filters. I think George Dobbs has it now. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

4th Aug 2016, 12:16 pm	#6
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: 40Metre SSB exciter.... Needs PA.. Cirkit started as Ambit International - Bill Poel. I believe there was a connection with something called Amateur Radio Bulk Buying group.

5th Aug 2016, 11:41 am	#7
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: 40Metre SSB exciter.... Needs PA.. Thanks - that's the one.

5th Aug 2016, 11:55 am	#8
Guest Guest Posts: n/a	Re: 40Metre SSB exciter.... Needs PA.. One of these http://www.ebay.co.uk/itm/DIY-KITS-4...item4d3ac91264 may do the trick.

5th Aug 2016, 1:38 pm	#9
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: 40Metre SSB exciter.... Needs PA.. Thanks Melin.. ordered.. __________________ Should get out more. Regards Wendy G8BZY