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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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8th Feb 2020, 1:45 am | #1 |
Hexode
Join Date: Apr 2011
Location: Stirlingshire, UK.
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Freq. adjustment on regen receiver with Denco coils
Hi All
I got this vintage Maplin regen kit receiver for 80m. It seems tune between 3560khz - 3700khz. I wanted it to tune either from 3500khz or 3700 kHz, so it would tune ham band CW or SSB DX signals. I am wondering if this is possible to adjust on this simple rudimentary regen receiver. It uses 2x ICs, and 2x transistors and 2x Denco coils. Tuning is done by what looks like variable resistor.
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8th Feb 2020, 3:02 am | #2 |
Dekatron
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,935
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Re: Freq. adjustment on regen receiver with Denco coils
I'm sure that such a change could be made, but it will be a million times easier to do if you find a circuit diagram.
B
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8th Feb 2020, 4:29 am | #3 |
Nonode
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 2,340
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Re: Freq. adjustment on regen receiver with Denco coils
If it has the following marked on the pcb
Maplin 80mtre GB59P Then the full article is in Maplin Magazine March-May 1984 |
8th Feb 2020, 5:56 am | #4 |
Dekatron
Join Date: Apr 2009
Location: Oxfordshire, UK.
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Re: Freq. adjustment on regen receiver with Denco coils
That 1984 design https://www.americanradiohistory.com...1984-03-05.pdf ticks most of the boxes for the OP description but it has 4 transistors rather than 2.
Looks very much as if it was intended to tune the full 3.5-3.8MHz, so may just be a setting-up problem or component tolerances to blame if it isn't doing that. B
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Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch. |
8th Feb 2020, 10:49 am | #5 |
Nonode
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 2,340
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Re: Freq. adjustment on regen receiver with Denco coils
That's the only one I can find in the Maplin mags that uses Denco Coils and is varicap tuned.
There are a couple of others but not 80m specific but they also use a variable capacitor and again, different number of transistors. |
8th Feb 2020, 11:07 am | #6 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,208
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Re: Freq. adjustment on regen receiver with Denco coils
I will just add that in the parts list for that article, the PCB has part number GB59P. Sounds like it must be the same project.
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8th Feb 2020, 11:13 am | #7 |
Heptode
Join Date: May 2015
Location: Chatham, Kent, UK.
Posts: 964
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Re: Freq. adjustment on regen receiver with Denco coils
Hi the components around t2 set the rx tuning range the pot rv4 is main tuning this varies the voltage across the ba102 d3 diode changing its capacitance. The
easy way to change this is to change the inductance of the coil t2 this is by ajusting the brass screw in the top of the coil noting its posision before so it can be put back if expected resaults are not acheived . Less inductance higher in frequency Denco coils have a wide range of ajustment. |
8th Feb 2020, 11:31 am | #8 |
Hexode
Join Date: Apr 2011
Location: Stirlingshire, UK.
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Re: Freq. adjustment on regen receiver with Denco coils
Indeed, it says MAPLIN 80mtre GB59P on the PCB. And I see at least 3x transistors this morning under the morning Sunlight. But the last is TR4. I see TR1, TR2 and TR4, but cannot spot TR3 on the PCB.
I tried to rotate the top star like hat on the T2, hoping it would tune down a bit to CW part of the band, but it didn't. Tried rotating the hat of the T1, but hardly moved the freq. The set was working OK on 3600khz SSb reception, lots of Russians were having their local net rag chewing, sounded like. But it stops tuning at about 3570khz where digital noise is very loud. It also doesn't go up over 3695khz, so that I couldn't hear usual DX hunting strong stations from the continent at nights.
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ORAWA = Old Radios And Wire Antennas Last edited by ORAWA01; 8th Feb 2020 at 11:51 am. |
8th Feb 2020, 11:39 am | #9 | |
Hexode
Join Date: Apr 2011
Location: Stirlingshire, UK.
Posts: 407
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Re: Freq. adjustment on regen receiver with Denco coils
Quote:
I thought it might be a regen, but learn that it is a DC receiver. It sounded very dynamic and clean on the band.
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ORAWA = Old Radios And Wire Antennas Last edited by ORAWA01; 8th Feb 2020 at 11:53 am. |
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8th Feb 2020, 11:53 am | #10 |
Heptode
Join Date: May 2015
Location: Chatham, Kent, UK.
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Re: Freq. adjustment on regen receiver with Denco coils
Hi its the brass screw that ajusts the coil the plastic star is to hold the coil to a chasis if not used in a holder. It should be the red coil this is the osc the aerial blue coil is wide enough to cover the 80mtr band hope this helps Mick
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8th Feb 2020, 11:55 am | #11 |
Hexode
Join Date: Apr 2011
Location: Stirlingshire, UK.
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Re: Freq. adjustment on regen receiver with Denco coils
Aha, got you. Will try that tonight when the band comes alive. Thank you Mick.
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9th Feb 2020, 10:55 am | #12 |
Hexode
Join Date: Apr 2011
Location: Stirlingshire, UK.
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Re: Freq. adjustment on regen receiver with Denco coils
Yes, it did work treat. I rotated the copper screw on the red coil, and the tuning shifted to the cw part of the band. Thank you for the advice and info.
https://youtu.be/S0He4tqAJrQ
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10th Feb 2020, 11:19 am | #13 |
Hexode
Join Date: Apr 2011
Location: Stirlingshire, UK.
Posts: 407
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Re: Freq. adjustment on regen receiver with Denco coils
It is now tuning from 3480khz to 3810khz, tested with the general coverage sw receiver side by side oscillation.
This morning trying out the set in the 80m ssb top end of the band. Antenna was 20m long wire in the garden. https://youtu.be/JMh2BV1UnlM
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