Maplin CW Filter PCB GB19V - UK Vintage Radio Repair and Restoration Discussion Forum

chrisbaker · 23rd Nov 2014, 5:25 pm

Hello
Looking for any info on the above unit, It uses 741 and marked up CW filter wonder if its a SSB/CW notch type filter??

Thanks

Chris
G4LDS

23rd Nov 2014, 7:37 pm

I would have thought a CW (morse) filter would be a peaking filter at about 800Hz.

David G4EBT · 24th Nov 2014, 12:29 am

It's the 'DXer's Audio Processor' by Robert Penfold. It used one transistor, (BC108), two diodes (1N4148) and five ICs, namely:

1458C - two
CA3080E
741C
TBA820M

If you'd like a copy of the 5-page article, which fetured in 'Maplin Project Book Seven' please PM me and I'll copy and post it to you Chris.

It was designed to be plugged into the audio output socket of a receiver, and has an output socket to accept headphones or a speaker, thus obviating the need for any internal connections to the receiver. Primarily to improve SSB reception in basic wide bandwidth short-wave receivers in poor reception conditions. (The picture shows it plugged into what looks like and Eddystone EB35 which didn't have a BFO, so maybe it was an EC10? Not relevant really).

It's a very old design - 1983 in fact. The same magazine had projects for a ZX81 Modem interface, a VIC20 RS232 interface, and how to use the Commodore 64. The magazine invited readers to visit one of Maplin's five shops - London, Manchester, Birmingham, Southampton and Southend.

Hope that helps.

chrisbaker · 24th Nov 2014, 1:05 pm

Thanks for the info & help. In my mind! I built a version in the 80's for use with my FT101 unless its a similar version as I remember a 14/16 pin 4 in one op amp!! Had a good notch which I looked at on a spectrum analyzer in my lunchhour at Marconi!!

m0cemdave · 26th Nov 2014, 1:56 am

I think your Notch filter was another Maplin project. It had a single tuning knob and some switches, and was selectable to peak or notch. The chip was probably a TL074 or 084.

23rd Nov 2014, 5:25 pm	#1
chrisbaker Retired Dormant Member Join Date: Nov 2014 Location: Morecambe, Lancashire, UK. Posts: 2	Maplin CW Filter PCB GB19V Hello Looking for any info on the above unit, It uses 741 and marked up CW filter wonder if its a SSB/CW notch type filter?? Thanks Chris G4LDS

23rd Nov 2014, 7:37 pm	#2
Guest Guest Posts: n/a	Re: Maplin CW Filter PCB GB19V I would have thought a CW (morse) filter would be a peaking filter at about 800Hz.

24th Nov 2014, 12:29 am	#3
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,761	Re: Maplin CW Filter PCB GB19V It's the 'DXer's Audio Processor' by Robert Penfold. It used one transistor, (BC108), two diodes (1N4148) and five ICs, namely: 1458C - two CA3080E 741C TBA820M If you'd like a copy of the 5-page article, which fetured in 'Maplin Project Book Seven' please PM me and I'll copy and post it to you Chris. It was designed to be plugged into the audio output socket of a receiver, and has an output socket to accept headphones or a speaker, thus obviating the need for any internal connections to the receiver. Primarily to improve SSB reception in basic wide bandwidth short-wave receivers in poor reception conditions. (The picture shows it plugged into what looks like and Eddystone EB35 which didn't have a BFO, so maybe it was an EC10? Not relevant really). It's a very old design - 1983 in fact. The same magazine had projects for a ZX81 Modem interface, a VIC20 RS232 interface, and how to use the Commodore 64. The magazine invited readers to visit one of Maplin's five shops - London, Manchester, Birmingham, Southampton and Southend. Hope that helps. __________________ David. BVWS Member. G-QRP Club member 1339.

24th Nov 2014, 1:05 pm	#4
chrisbaker Retired Dormant Member Join Date: Nov 2014 Location: Morecambe, Lancashire, UK. Posts: 2	Re: Maplin CW Filter PCB GB19V Thanks for the info & help. In my mind! I built a version in the 80's for use with my FT101 unless its a similar version as I remember a 14/16 pin 4 in one op amp!! Had a good notch which I looked at on a spectrum analyzer in my lunchhour at Marconi!!

26th Nov 2014, 1:56 am	#5
m0cemdave Octode Join Date: Feb 2009 Location: Bletchley, Buckinghamshire, UK. Posts: 1,219	Re: Maplin CW Filter PCB GB19V I think your Notch filter was another Maplin project. It had a single tuning knob and some switches, and was selectable to peak or notch. The chip was probably a TL074 or 084.