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[K2] VCO Aignment L30

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andrew-2

[K2] VCO Aignment L30

K2 #7303 is slowly coming together and I thought I would check with the list the results of the VCO Alignment (Page 64).

With the core of inductor L30 wound right to the top, the lowest voltage achieved is 6.1v and the ranges are as follows:

80m = 2.29 - 6.10
40m = 1.594 - 3.115
30m = 3.253 - 3.84
20m = 3.01 - 4.97
17m = 3.71 - 3.94
15m = 2.456 - 3.638
12m = 4.92 - 5.37
10m = 3.91 - 4.88

Is it okay to continue with these results? I've rechecked the component placement and T5 winding.

Many thanks
Andrew
vk6wax
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Don Wilhelm-4

Re: [K2] VCO Aignment L30

Andrew,

While those ranges will work, I usually like to see the lowest voltage a
bit higher than 1.6 volts.

Set the frequency that produces the highest voltage (4000 kHz) and
spread the turns of T5 a bit to increase the voltage at R30. I would
suggest that you try setting it to about 6.5 volts. Then go back and
see how much the voltage at 7000 Hz has increased.

73.
Don W3FPR

On 12/30/2012 7:09 AM, andrew wrote:

> K2 #7303 is slowly coming together and I thought I would check with the list the results of the VCO Alignment (Page 64).
>
> With the core of inductor L30 wound right to the top, the lowest voltage achieved is 6.1v and the ranges are as follows:
>
> 80m = 2.29 - 6.10
> 40m = 1.594 - 3.115
> 30m = 3.253 - 3.84
> 20m = 3.01 - 4.97
> 17m = 3.71 - 3.94
> 15m = 2.456 - 3.638
> 12m = 4.92 - 5.37
> 10m = 3.91 - 4.88
>
> Is it okay to continue with these results? I've rechecked the component placement and T5 winding.
>

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andrew-2

Re: [K2] VCO Aignment L30

Thanks for the reply Don.

To clarify, I can increase the voltage by winding the core of L30 down from the top, in fact up to about 8v but not the minimum of 6.0v as per the instructions. Would using this method achieve the desired result or is spreading the primary windings on T5 a prerequisite?

Many thanks
Andrew
vk6wax

---- Don Wilhelm <[hidden email]> wrote:
> Set the frequency that produces the highest voltage (4000 kHz) and
> spread the turns of T5 a bit to increase the voltage at R30. I would
> suggest that you try setting it to about 6.5 volts. Then go back and
> see how much the voltage at 7000 Hz has increased.
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Don Wilhelm-4

Re: [K2] VCO Aignment L30

Andrew,

The 6 volt initial setting at 4000 kHz is an initial setting. And like
I said, your settings will work fine.
I prefer to see all voltages above 1.8 volts, so the voltage at 7000 kHz
is a bit lower than my preference.

If you can use the L30 setting to increase the voltage, then do so, but
if not, then adjust the turns spacing on T5. Note that L30 and T5 are
inductors in parallel, so adjusting one or the other will do the task
just fine.

The upper voltage adjustment must be limited to less than 7.5 volts.
Note that the maximum voltage is limited by the voltage to the U6 op
amp, so voltages of 8 volts indicate that the voltage range has run to
its limit - keep the high voltage below 7.5 volts.

In other words, increase the voltage at 4 MHz a bit in order to increase
the voltage at 7 MHz a bit, but keep all the voltage within the range of
7.5 volts to 1.5 volts. Actually keeping the range between 6.5 volts
and 1.8 volts is the preferred range.

73,
Don W3FPR
On 12/30/2012 10:17 PM, andrew wrote:

> Thanks for the reply Don.
>
> To clarify, I can increase the voltage by winding the core of L30 down from the top, in fact up to about 8v but not the minimum of 6.0v as per the instructions. Would using this method achieve the desired result or is spreading the primary windings on T5 a prerequisite?
>
> Many thanks
> Andrew
> vk6wax
>
> ---- Don Wilhelm <[hidden email]> wrote:
>> Set the frequency that produces the highest voltage (4000 kHz) and
>> spread the turns of T5 a bit to increase the voltage at R30. I would
>> suggest that you try setting it to about 6.5 volts. Then go back and
>> see how much the voltage at 7000 Hz has increased.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

andrew-2

Re: [K2] VCO Aignment L30

Thanks for the detailed explanation Don.

I set the voltage for 4000kHz at several points and noted the corresponding voltage for 7000kHz as follows:

4000 7000
6.10 -> 1.594
6.50 -> 1.733
6.60 -> 1.768
6.70 -> 1.800

The last set of figures, 6.70 and 1.800, appear to be the best compromise? The voltages for all other frequencies being between 2.48v and 5.55v.

Many thanks
Andrew
vk6wax

> > ---- Don Wilhelm wrote:
> Actually keeping the range between 6.5 volts and 1.8 volts is the preferred range.
>
> >> Set the frequency that produces the highest voltage (4000 kHz) and
> >> spread the turns of T5 a bit to increase the voltage at R30. I would
> >> suggest that you try setting it to about 6.5 volts. Then go back and
> >> see how much the voltage at 7000 Hz has increased.
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Don Wilhelm-4

Re: [K2] VCO Aignment L30

Andrew,

You made a good choice.

73,
Don W3FPR

On 1/1/2013 3:40 AM, andrew wrote:

> Thanks for the detailed explanation Don.
>
> I set the voltage for 4000kHz at several points and noted the corresponding voltage for 7000kHz as follows:
>
> 4000 7000
> 6.10 -> 1.594
> 6.50 -> 1.733
> 6.60 -> 1.768
> 6.70 -> 1.800
>
> The last set of figures, 6.70 and 1.800, appear to be the best compromise? The voltages for all other frequencies being between 2.48v and 5.55v.
>