[ARC5] SCR-183/-283 4-5 MC Coil on 75 MTRs

AKLDGUY . neilb0627 at gmail.com
Tue Jul 8 08:25:32 EDT 2014


>> Referring specifically to the BC-xx-230 model:
>> How does one determine the setting for the roller inductor?

> I got a pencil, a slide-rule and a stack of paper.
> Looked-up the tube characteristics, made exact measurements, graphed load
lines and spent an entire afternoon doing > eight pages of advanced
calculus.
>
> Then I folded the pages into paper airplanes, flew
> them out the window and did it by "trial and error."
> Took about 5 minutes.

Ahahahhaha!

 > I have both a "stock" 3.2-4.0 MC and a "padded"
> 4-5 MC coil set for 3890 KC. I'll post the tap positions later today or
tomorrow when I write-up the successful use of
> 6AQ5 in all stages.

OK.

>> Has anyone tried using the 1626 triode for VFO and PA?

> I did some time ago with a BC-230.  I jumpered the Modulator filament
connections and supplied
> 12 V to the 1626 filaments.  I made no other circuit changes.
> The 1626s neutralized and worked without trouble, delivering
> (IIRC)  4 Watts out, which is spec for this little rig.
> I don't remember if drift or chirp was an issue with them.

That is very encouraging.

> I have not yet tried 1626 in the Modulator stage.
> To do so would almost certainly require a minor change in the biasing
scheme.  I've recently had good success doing so > with 6AQ5s, which have
actually taken the "hard service" quite well.

Modulation would be an unlikely proposition here as the mod tranny's are
not available. I'd be content with just CW.

>> If so, what B+
> Dynamotor B+ of 330 V under load.

I presume you mean with the 1626's, not the stock VT-52/VT-25 combo,
but 330V greatly exceeds the 1626 ratings.

>> what bias resistor did you use?
> with the 1626s as OSC and PA, I made no changes
> from the stock 20K grid bias resistor.

Again, that's very encouraging.

Thank you David. At some stage I may come back to you for circuit values.
All I have to go on at the moment is the schematic for the BC-AH-230 you
posted awhile back.

There'll be no replies for at least 8 hours as it's now after midnight on a
stormy winter's night.

73 de Neil ZL1ANM


On Tue, Jul 8, 2014 at 10:46 PM, David Stinson <arc5 at ix.netcom.com> wrote:

>
> ----- Original Message ----- From: "AKLDGUY ." <neilb0627 at gmail.com>
> Subject: Re: [ARC5] SCR-183/-283 4-5 MC Coil on 75 MTRs
>
>
>
>  Referring specifically to the BC-xx-230 model:
>> How does one determine the setting for the roller inductor?
>>
>
> I got a pencil, a slide-rule and a stack of paper.
> Looked-up the tube characteristics, made exact measurements, graphed load
> lines and spent an entire afternoon doing eight pages of advanced calculus.
>
> Then I folded the pages into paper airplanes, flew
> them out the window and did it by "trial and error."
> Took about 5 minutes.
>
> I have both a "stock" 3.2-4.0 MC and a "padded"
> 4-5 MC coil set for 3890 KC. I'll post the tap positions later today or
> tomorrow when I write-up the successful use of 6AQ5 in all stages.
>
>
>  Has anyone tried using the 1626 triode for VFO and PA?
>>
> I did some time ago with a BC-230.  I jumpered the Modulator filament
> connections and supplied
> 12 V to the 1626 filaments.  I made no other circuit changes.
> The 1626s neutralized and worked without trouble, delivering
> (IIRC)  4 Watts out, which is spec for this little rig.
> I don't remember if drift or chirp was an issue with them.
> I have not yet tried 1626 in the Modulator stage.
> To do so would almost certainly require a minor change in the biasing
> scheme.  I've recently had good success doing so with 6AQ5s, which have
> actually taken the "hard service" quite well.
>
>> If so, what B+
>>
> Dynamotor B+ of 330 V under load.
>
>  what bias resistor did you use?
>>
> With the 1626s as OSC and PA, I made no changes
> from the stock 20K grid bias resistor.
>
>
> 73 DE Dave AB5S
>
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