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[KX1] Variation in driver transistors (e.g. 2SC2166)

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Chip Stratton

[KX1] Variation in driver transistors (e.g. 2SC2166)

Just wondering here. How much part to part variation do devices like this
display in their gain characteristics? If I had ten of these transistors, is
there a good chance I could identify one with significantly better gain
and/or power efficiency than the average? Would a simple measurement of hfe
identify such a part, or is it more complicated than that?

I've seen a Youtube video wherein a guy who sells 2SC2166 devices made by
Eleflow substitutes this for the Mitsubishi made part and seems to get a
bit more power output out of a CB transmitter. Is this likely to represent a
gain of efficiency of the final amplifier, or is it just a part that is just
needs a lower bias to operate at its best?

Thanks,
Chip
AE5KA
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Leigh L. Klotz Jr WA5ZNU

Re: [KX1] Variation in driver transistors (e.g. 2SC2166)

Administrator

Here's some info to read:
http://elecraft.365791.n2.nabble.com/KX1-Q6-question-td662532.html
and here, in this erratum superseded by the revision E manual which shows the changeover:
http://www.elecraft.com/manual/KX1_Owners_Manual_Errata_Rev_D-1.pdf

It seems that Elecraft went from a 2SC2166 to a 2SC5739 for RoHS compliance.

A side benefit is that the new part eliminates a thermal pad, shoulder washer, and thus a potential for a short from the KX1 build.

Some have reported improved output on 20M with this part, albeit with the usual warnings about too much power causing you trouble later if you don't have a great match to your antenna, a strong possibility under the KX1 normal operating conditions.

Leigh/WA5ZNU

Don Wilhelm-4

Re: [KX1] Variation in driver transistors (e.g. 2SC2166)

In reply to this post by Chip Stratton

Chip,

If your goal is to get more than 4 watts out of your KX1, I would
caution against trying. If you are attempting to obtain more power when
running with internal batteries, it is fine to try it, but when
operating with a 13.8 volt power source (or any other voltage) and the
power is greater than 4 watts, I strongly suggest you back off on the
setting of the R1 pot to protect the components in the output of the PA
transistor. Note that the Eleflow 2SC2166 datasheet rates the
transistor for the 3 to 4 watt range.

Elecraft used the 2SC5739 in the KX1 for a period of time when it looked
like the 2SC2166 would not be available. It worked well, and produced a
bit more output on 20 meters, but the new KX1 kits are shipping with the
2SC2166 again.

You can try if you want - the parameter that should be investigated is
the power gain. A simple hfe measurement may not reveal changes in the
power gain. Current Gain (hfe) does not directly infer power gain.

I would suggest that if you want more output on 14 MHz, change to the
2SC5739.

73,
Don W3FPR

On 2/9/2011 6:50 PM, Chip Stratton wrote:

> Just wondering here. How much part to part variation do devices like this
> display in their gain characteristics? If I had ten of these transistors, is
> there a good chance I could identify one with significantly better gain
> and/or power efficiency than the average? Would a simple measurement of hfe
> identify such a part, or is it more complicated than that?
>
> I've seen a Youtube video wherein a guy who sells 2SC2166 devices made by
> Eleflow substitutes this for the Mitsubishi made part and seems to get a
> bit more power output out of a CB transmitter. Is this likely to represent a
> gain of efficiency of the final amplifier, or is it just a part that is just
> needs a lower bias to operate at its best?
>
> Thanks,
> Chip
> AE5KA
> ______________________________________________________________
> 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
>

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Don Wilhelm-4

Re: [KX1] Variation in driver transistors (e.g. 2SC2166)

In reply to this post by Leigh L. Klotz Jr WA5ZNU

Leigh,

Elecraft is currently shipping KX1s with the 2SC2166 again. I have
built 4 in the last month and all 4 have that transistor.

The thermal pad provides better heat conduction and should not be
eliminated if a plastic tab transistor is used - only the shoulder
washer is eliminated.

73,
Don W3FPR

On 2/9/2011 7:21 PM, Leigh L. Klotz Jr WA5ZNU wrote:

> Here's some info to read:
> http://elecraft.365791.n2.nabble.com/KX1-Q6-question-td662532.html
> and here, in this erratum superseded by the revision E manual which shows
> the changeover:
> http://www.elecraft.com/manual/KX1_Owners_Manual_Errata_Rev_D-1.pdf
>
> It seems that Elecraft went from a 2SC2166 to a 2SC5739 for RoHS compliance.
>
> A side benefit is that the new part eliminates a thermal pad, shoulder
> washer, and thus a potential for a short from the KX1 build.
>
> Some have reported improved output on 20M with this part, albeit with the
> usual warnings about too much power causing you trouble later if you don't
> have a great match to your antenna, a strong possibility under the KX1
> normal operating conditions.
>
> Leigh/WA5ZNU
>

Chip Stratton

Re: [KX1] Variation in driver transistors (e.g. 2SC2166)

Thanks Leigh & Don,

I'm not as concerned about maxing output, though getting 4 watts on 20
meters (like I'm getting on 80 meters) would be nice. I do like to
experiment a little, so trying the 2SC5739 would be interesting.

I am interested getting some idea about part to part variability. I have a
lot of experience with LEDs and the variability they exhibit coming off the
assembly line, and am wondering if other semiconductor devices - like the
2SC2166 - show similar variability in efficiencies?

Thanks,
Chip
AE5KA

On Wed, Feb 9, 2011 at 7:22 PM, Don Wilhelm <[hidden email]> wrote:

> Leigh,
>
> Elecraft is currently shipping KX1s with the 2SC2166 again. I have
> built 4 in the last month and all 4 have that transistor.
>
> The thermal pad provides better heat conduction and should not be
> eliminated if a plastic tab transistor is used - only the shoulder
> washer is eliminated.
>
> 73,
> Don W3FPR
>
> On 2/9/2011 7:21 PM, Leigh L. Klotz Jr WA5ZNU wrote:
> > Here's some info to read:
> > http://elecraft.365791.n2.nabble.com/KX1-Q6-question-td662532.html
> > and here, in this erratum superseded by the revision E manual which shows
> > the changeover:
> > http://www.elecraft.com/manual/KX1_Owners_Manual_Errata_Rev_D-1.pdf
> >
> > It seems that Elecraft went from a 2SC2166 to a 2SC5739 for RoHS
> compliance.
> >
> > A side benefit is that the new part eliminates a thermal pad, shoulder
> > washer, and thus a potential for a short from the KX1 build.
> >
> > Some have reported improved output on 20M with this part, albeit with the
> > usual warnings about too much power causing you trouble later if you
> don't
> > have a great match to your antenna, a strong possibility under the KX1
> > normal operating conditions.
> >
> > Leigh/WA5ZNU
> >
> ______________________________________________________________
> 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
>

Don Wilhelm-4

Re: [KX1] Variation in driver transistors (e.g. 2SC2166)

Chip,

My experience with the KX1, K1 and K2 indicates that you will find
little variation in power gain, even when the hfe of the PA transistors
vary considerably. There are design parameters such as the collector
load resistance that swamp the variations - and the PA output circuit is
designed for that load resistance.

Take a look at Experimental Methods in RF Design - the section on
Practical Power Amplifiers, and you will find that the most important
consideration is in the formula R(load) = Vcc (squared)/2 times Power
Out. So the load resistance is the predominate factor in determining
the power output capability of the amplifier - as long as the PA
transistor can stand the required current and voltage for that power.

73,
Don W3FPR

On 2/9/2011 8:39 PM, Chip Stratton wrote:

> Thanks Leigh& Don,
>
> I'm not as concerned about maxing output, though getting 4 watts on 20
> meters (like I'm getting on 80 meters) would be nice. I do like to
> experiment a little, so trying the 2SC5739 would be interesting.
>
> I am interested getting some idea about part to part variability. I have a
> lot of experience with LEDs and the variability they exhibit coming off the
> assembly line, and am wondering if other semiconductor devices - like the
> 2SC2166 - show similar variability in efficiencies?
>
> Thanks,
> Chip
> AE5KA
>
> On Wed, Feb 9, 2011 at 7:22 PM, Don Wilhelm<[hidden email]> wrote:
>
>> Leigh,
>>
>> Elecraft is currently shipping KX1s with the 2SC2166 again. I have
>> built 4 in the last month and all 4 have that transistor.
>>
>> The thermal pad provides better heat conduction and should not be
>> eliminated if a plastic tab transistor is used - only the shoulder
>> washer is eliminated.
>>
>> 73,
>> Don W3FPR
>>
>> On 2/9/2011 7:21 PM, Leigh L. Klotz Jr WA5ZNU wrote:
>>> Here's some info to read:
>>> http://elecraft.365791.n2.nabble.com/KX1-Q6-question-td662532.html
>>> and here, in this erratum superseded by the revision E manual which shows
>>> the changeover:
>>> http://www.elecraft.com/manual/KX1_Owners_Manual_Errata_Rev_D-1.pdf
>>>
>>> It seems that Elecraft went from a 2SC2166 to a 2SC5739 for RoHS
>> compliance.
>>> A side benefit is that the new part eliminates a thermal pad, shoulder
>>> washer, and thus a potential for a short from the KX1 build.
>>>
>>> Some have reported improved output on 20M with this part, albeit with the
>>> usual warnings about too much power causing you trouble later if you
>> don't
>>> have a great match to your antenna, a strong possibility under the KX1
>>> normal operating conditions.
>>>
>>> Leigh/WA5ZNU
>>>
>> ______________________________________________________________
>> 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
>>
> ______________________________________________________________
> 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
>