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K2: 40m bandpass filter

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David Pratt

K2: 40m bandpass filter

Don W3FPR:
A query about C228 a few days ago prompted me to look at my own K2
manual which does not show C228. Unless my old grey cells deceive me, I
recall the 40m bandpass filter being changed several years ago. In fact,
I have found an old envelope in which I have gathered together the
necessary five capacitors to make the change.

My question is: What was the reason for the change of the 40m bandpass
filter and is it worth doing? BTW, I do use my K2 on 60m.

73 de David G4DMP
--
David G4DMP
Leeds, England, UK
------

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Sverre Holm (LA3ZA)

Re: K2: 40m bandpass filter

All the proposed changes to the 40 m bandpass were, as far as I can recall, intended to decrease the bandwidth from 300 kHz to 200 or 100 kHz. These modifications can be found here:

Elecraft's EU 40 Meter Narrow Bandpass Filter and DL7MAJ's proposal which is almost the same as Elecraft's for 40 m.

However, with the increase in 40 m allocation in Europe (region 1) some years ago and the decrease in the number of strong broadcast stations, these changes should not be necessary any more. I changed my 40 m bandpass back to the original one several years ago for this reason.

David Pratt-4 wrote

I recall the 40m bandpass filter being changed several years ago.

Sverre, LA3ZA

K2 #2198, K3 #3391,
LA3ZA Blog: http://la3za.blogspot.com,
LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html

David Pratt

Re: K2: 40m bandpass filter

Thank you very much, Sverre; I now remember it. I shall not make the
change, particularly as I rarely operate above 7100 kHz anyway.

73 de David G4DMP

In a recent message, "Sverre Holm (LA3ZA)" <[hidden email]> writes

>All the proposed changes to the 40 m bandpass were, as far as I can recall,
>intended to decrease the bandwidth from 300 kHz to 200 or 100 kHz. These
>modifications can be found here:
>
>Elecraft's
>http://www.elecraft.com/Apps/eu_40_meter_narrow_bandpass_filt.htm EU 40
>Meter Narrow Bandpass Filter and
>http://www.dl7maj.de/Modifications%20for%20BPF.pdf DL7MAJ's proposal which
>is almost the same as Elecraft's for 40 m.
>
>However, with the increase in 40 m allocation in Europe (region 1) some
>years ago and the decrease in the number of strong broadcast stations, these
>changes should not be necessary any more. I changed my 40 m bandpass back to
>the original one several years ago for this reason.

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Don Wilhelm-4

Re: K2: 40m bandpass filter

In reply to this post by David Pratt

David,

The 40 meter LPF was changed to an elliptical filter - you can see by
comparing the old and new circuits.
I am not certain of the reason, but I have assumed that it provides
better performance for both 50 and 40 meters (better harmonic rejection
for 60 meters).

73,
Don W3FPR

On 1/15/2011 3:21 AM, David Pratt wrote:

> Don W3FPR:
> A query about C228 a few days ago prompted me to look at my own K2
> manual which does not show C228. Unless my old grey cells deceive me, I
> recall the 40m bandpass filter being changed several years ago. In fact,
> I have found an old envelope in which I have gathered together the
> necessary five capacitors to make the change.
>
> My question is: What was the reason for the change of the 40m bandpass
> filter and is it worth doing? BTW, I do use my K2 on 60m.
>
> 73 de David G4DMP

Don Wilhelm-4

Re: K2: 40m bandpass filter

Sorry, I saw C228 through my morning eyes and answered about the LPF,
but the question was about the BPF - it has been answered by Sverre.

73,
Don W3FPR

On 1/15/2011 8:56 AM, Don Wilhelm wrote:

> David,
>
> The 40 meter LPF was changed to an elliptical filter - you can see by
> comparing the old and new circuits.
> I am not certain of the reason, but I have assumed that it provides
> better performance for both 50 and 40 meters (better harmonic rejection
> for 60 meters).
>
> 73,
> Don W3FPR
>
> On 1/15/2011 3:21 AM, David Pratt wrote:
>> Don W3FPR:
>> A query about C228 a few days ago prompted me to look at my own K2
>> manual which does not show C228. Unless my old grey cells deceive me, I
>> recall the 40m bandpass filter being changed several years ago. In fact,
>> I have found an old envelope in which I have gathered together the
>> necessary five capacitors to make the change.
>>
>> My question is: What was the reason for the change of the 40m bandpass
>> filter and is it worth doing? BTW, I do use my K2 on 60m.
>>
>> 73 de David G4DMP
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Colin VE3MSC

Solved - XV144, XV222, XV432

Thanks to many of you on the list, I have 3 pretty happy transverters.

Heat problem - solved by replacing thermal pad between heat spreader
and case. Use Thermalcote heatsink grease instead.

Scraped paint off the case under screw heads, using a cylindrical
dremel bit, for all 3 XVs. Replaced the black screws with chrome or
stainless on the XV432. This helped the output substantially.

XV144 - the supplied crystal is out of range, and Elecraft will be
replacing. Turns out they started using same one for XV144 and the
internal K144XV. But XV144 will be more than 10KHz off, so you can't
correct for it. I added a small series variable inductor between
xtal and ground, and this helped me get it within 5KHz. You can't
bend these crystals very far.

XV222 - I removed L19, jumpered it out, and replaced C12 with a
variable capacitor. Schematic says 12pF, assembly guide 18pF, and a
variable let me get the frequency within a few hertz.

XV432 - drilled a couple holes near U6 and jumpered top to bottom.
There just arent enough vias on this board. Replaced my U6. Output
now pretty stable. I still think PA Bias instructions in alignment
are wrong for this unit.
Fan wires would not go through the big via, so I soldered it at the
diode on the top of the board.

73 VE3MSC
Colin

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Johnny Siu

Re： Solved - XV144, XV222, XV432

Thanks for good summary. It was quite a huge investment in 3 transverters and
certainly you would expect more value for money. Your suggestions could be the
manual errata.
cheers,

Johnny VR2XMC

________________________________
寄件人﹕ Colin VE3MSC <[hidden email]>
收件人﹕ Elecraft Reflector <[hidden email]>
傳送日期﹕ 2011/1/15 (六) 10:35:27 PM
主題： [Elecraft] Solved - XV144, XV222, XV432

Thanks to many of you on the list, I have 3 pretty happy transverters.

Heat problem - solved by replacing thermal pad between heat spreader
and case. Use Thermalcote heatsink grease instead.

Scraped paint off the case under screw heads, using a cylindrical
dremel bit, for all 3 XVs. Replaced the black screws with chrome or
stainless on the XV432. This helped the output substantially.

XV144 - the supplied crystal is out of range, and Elecraft will be
replacing. Turns out they started using same one for XV144 and the
internal K144XV. But XV144 will be more than 10KHz off, so you can't
correct for it. I added a small series variable inductor between
xtal and ground, and this helped me get it within 5KHz. You can't
bend these crystals very far.

XV222 - I removed L19, jumpered it out, and replaced C12 with a
variable capacitor. Schematic says 12pF, assembly guide 18pF, and a
variable let me get the frequency within a few hertz.

XV432 - drilled a couple holes near U6 and jumpered top to bottom.
There just arent enough vias on this board. Replaced my U6. Output
now pretty stable. I still think PA Bias instructions in alignment
are wrong for this unit.
Fan wires would not go through the big via, so I soldered it at the
diode on the top of the board.

73 VE3MSC
Colin

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wayne burdick

Re： Solved - XV144, XV222, XV432

Administrator

Hi Colin,

These issues will all be addressed in our transverter kit, PCBs, and
documentation as required. Sorry for the inconvenience.

73,
Wayne
N6KR

> Thanks to many of you on the list, I have 3 pretty happy transverters.
>
> Heat problem - solved by replacing thermal pad between heat spreader
> and case. Use Thermalcote heatsink grease instead.
>
> Scraped paint off the case under screw heads, using a cylindrical
> dremel bit, for all 3 XVs. Replaced the black screws with chrome or
> stainless on the XV432. This helped the output substantially.
>
> XV144 - the supplied crystal is out of range, and Elecraft will be
> replacing. Turns out they started using same one for XV144 and the
> internal K144XV. But XV144 will be more than 10KHz off, so you can't
> correct for it. I added a small series variable inductor between
> xtal and ground, and this helped me get it within 5KHz. You can't
> bend these crystals very far.
>
> XV222 - I removed L19, jumpered it out, and replaced C12 with a
> variable capacitor. Schematic says 12pF, assembly guide 18pF, and a
> variable let me get the frequency within a few hertz.
>
> XV432 - drilled a couple holes near U6 and jumpered top to bottom.
> There just arent enough vias on this board. Replaced my U6. Output
> now pretty stable. I still think PA Bias instructions in alignment
> are wrong for this unit.
> Fan wires would not go through the big via, so I soldered it at the
> diode on the top of the board.
>
> 73 VE3MSC
> Colin
>
>
> ______________________________________________________________
> 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