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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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Old 14th May 2024, 9:16 pm   #1
Phil G4jhs
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Join Date: May 2024
Location: Bradford, West Yorkshire, UK.
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Default Codar Multiband 6 info

I recently got hold of a Codar Multiband 6 (No coils) and I am in the process of restoration. I do have a set of the Denco 9 pin dual purpose coils green range but read somewhere that there are changes to be made if you want to use them with this radio? Does anyone have any info regarding this coil mod or any other info that would help me in my quest.

Kind regards
Phil
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Old 17th May 2024, 10:55 pm   #2
frsimen
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Default Re: Codar Multiband 6 info

Hello Phil,

A belated welcome to the forum

Looking at the construction information for the Multiband 6, the wiring to the valve holder for the plug in coils matches the pinout for the coils given in the Denco data for Green coils.

I've seen the same comment on line about the coil modification, perhaps whoever built that version made a mistake in the wiring. Denco green coils should work without modification. If you can't get the circuit to oscillate, swapping the wiring to pins 3 and 4 should sort that problem out.

Paula
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Old 20th May 2024, 12:22 pm   #3
Phil G4jhs
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Default Re: Codar Multiband 6 info

Hi Paula,
Thank you for the info. I was thinking along the same lines looking at the info for the Denco green coils. Regarding your comment on pins 3 and 4 for regeneration I take it that you mean reverse the connections to 3 and 4? The circuit diagram that I managed to get hold of is slightly different to the wiring of this RX. Connecting an antenna gives no signal but if I inject a signal I can detect it albeit very faintly. Will be spending more time on it shortly.
Kind regards
Phil
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Old 20th May 2024, 7:17 pm   #4
frsimen
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Default Re: Codar Multiband 6 info

Hello Phil,

If the regeneration isn't working, the phase of the regeneration winding is probably not right. Reversing the connections to pins 3 and 4 on the valve base (not on the coil!) will correct that. It does sound as if something isn't working properly. Check the AF stages first, then worry about the detector stage. If you fit a MW coil, you should be able to hear the detector oscillating on another MW radio. That will prove that the coil phasing is correct. If it doesn't work, maybe the FET has been damaged, or wired incorrectly.

Paula
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Old 20th May 2024, 9:49 pm   #5
Phil G4jhs
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Default Re: Codar Multiband 6 info

Hi Paula
I did order a couple of FETs on the off chance it is damaged. The audio stage seems ok, i do have output into a 8ohm LS and also into my headphones when i inject a signal but as soon as i get the chance i will swap the connections on pins 3 and 4 and see what happens if no progress i will change the FET and check the components around it. I will let you know how it goes.
Many thanks
Phil
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