K2 App Notes

K2 App Notes

K2 App Notes

K2 App Notes

App Note #9
Elecraft(R) jumpers before & after
IMA: Six Jumpers Now Standard
(Click image to open PDF)

19 Ju­ly 2013 – Hence­forth the In­ter­nal Mic Adap­tor kit will only in­clude six jump­ers.


Al­though the pre­vi­ous (rev 6E) user’s guide called for sev­en jump­ers for the Elecraft® con­fig­u­ra­tion, it al­so men­tioned that the func mic5 jump­er was es­sen­tial­ly a spare, giv­en that the K2 firm­ware does not re­spond to the func sig­nal.


All af­fect­ed doc­u­men­ta­tion has been re­pub­lished since this app note was in­itial­ly re­leased.  Please re­fer to the latest versions of the de­cal, sin­gle-page sum­ma­ry sheet, and user’s guide as the un­used ver­sus ex­tra/spare lo­ca­tions have been re­op­ti­mized, to min­i­mize the need to re­po­si­tion jump­ers when chang­ing con­fig­u­ra­tions.


The in­struc­tions still call for eight jump­ers per con­fig­u­ra­tion, it’s just that now two of those eight lo­ca­tions are op­tion­al spares, in­stead of one.

Re­vised 21 JUL 2013

App Note #8
spare jumper storage locations
IMA: Onboard Jumper Storage
(Click image to open PDF)

11 May 2012 – The pre­vi­ous ver­sion of the IMA user’s guide only showed where to in­stall jump­ers es­sen­tial to the op­er­a­tion of each mi­cro­phone.  Un­for­tu­nate­ly this num­ber var­ies, so some­times you had to add or re­move jump­ers when chang­ing con­fig­u­ra­tions.


Most con­fig­u­ra­tions call for five jump­ers; but one spec­i­fies four, and one six.  Chang­ing mi­cro­phones would be even eas­i­er if the num­ber of jump­ers re­main­ed the same.


The lat­est ver­sion of the de­cal (re­pro­duced above left) shows where to store/park any “un­used” jump­ers.  Note that these lo­ca­tions vary with each con­fig­u­ra­tion.  This scheme even ac­com­mo­dates two op­tion­al spare jump­ers, not in­clud­ed with the IMA kit of parts.


The de­cal de­notes “es­sen­tial” jump­ers with black ovals; stor­age lo­ca­tions for un­used jump­ers with gray ovals; and stor­age lo­ca­tions for two op­tion­al spare jump­ers with white ovals.

Post Script

This sug­ges­tion was merged in­to the user’s guide on 25 Ju­ly 2012.

App Note #7
4.7 pf Cap Installation
Headers Kit: 4.7 pF Cap

3 May 2012 – The pho­tos of the as­sem­bled Head­ers kit – both on our web­site and in our PDF in­struc­tions – show the 4.7 pF cap on the UN-K60XV head­er “stand­ing” up­right.  In con­trast, the 3 May 2012 ver­sion of the Head­ers kit Quick Start In­struc­tion Sheet (QSIS) sug­gests that this cap should be in­stalled tilt­ed more than 45 de­grees from ver­ti­cal.  Please fol­low the in­struc­tions in the QSIS when in­stall­ing this cap and po­si­tion it tilt­ed suf­fi­cient­ly that it ex­tends no high­er off the board than the height of the in­su­lat­ing body of P15.


Even stand­ing ver­ti­cal­ly, the cap will still eas­i­ly clear near­by K2 com­po­nents when the UN-K60XV head­er is in­stall.  The only con­cern is that the cap could be dam­aged when the UN-K60XV head­er is not in­stalled in your K2, but is in­stead parked/stored on the “Foam Home” that’s in­clud­ed with the kit.

Corrective Action

If you’ve not yet as­sem­bled your head­ers kit, just fol­low the in­struc­tions in the lat­est QSIS.  If you al­ready built the kit, do not at­tempt to tilt the cap once it has been sol­dered in place, since do­ing so could dam­age/crack the me­nis­cus on its leads.  In­stead, make a suit­a­ble in­den­ta­tion/hole in the foam im­me­di­ate­ly be­low where the cap will re­side.  Then just be sure to al­ways po­si­tion the UN-K60XV board on the foam, such that the cap is di­rect­ly over this lo­ca­tion.  (You might find it help­ful to draw an out­line of the board in this po­si­tion, with a per­ma­nent mark­er.)

App Note #6
K2/100 toroid depictions
K2/100: Toroid Winding Guide
for Fully Loaded K2/100 + KAT100
(Click image to open PDF)

20 April 2012 – If you are build­ing a K2 and wind­ing the to­roids your­self, then you will sure­ly find this guide use­ful.  It de­picts how to even­ly dis­trib­ute the wind­ings over the core di­am­e­ter, for all of the turns counts you’ll en­coun­ter in the course of build­ing a ful­ly load­ed K2/100 and a KAT100.  It al­so shows the di­rec­tion (i.e. over ver­sus un­der) that the turns must be wound. 

In all but one in­stance, the wind­ings are spaced over 85% of the core and the core is shown ac­tu­al size.

App Note #5

When NOT to Externally Bias

9 May 2008 – In a recent Reflector post Don Wil­helm (W3FPR) wrote …

“Cau­tion: you must know your … mi­cro­phone el­e­ment type – a dynamic el­e­ment can be damaged if bi­as is ap­plied to it.”


The two types of mi­cro­phones com­mon­ly used with am­a­teur ra­dio equip­ment are electret and dynamic These terms re­fer to the prin­ci­ple on which their trans­duc­er (el­e­ment) op­er­ates.  The out­put of an electret trans­duc­er is in­her­ent­ly low, so electret mi­cro­phones al­ways in­cor­po­rate a built-in pre-am­pli­fi­er.

In con­trast, the out­put of a dynamic trans­duc­er is nor­mal­ly suf­fi­cient to drive a mod­ern solid-state trans­ceiv­er di­rect­ly.  Thus, pre-am­pli­fied dynamic mi­cro­phones are rare­ly en­coun­tered.


Re­gard­less of its el­e­ment type, if a mi­cro­phone has an in­ter­nal pre-am­pli­fi­er it needs to be pow­ered some­how.  In am­a­teur ra­dio ap­pli­ca­tions, this pow­er is pro­vid­ed in one of two ways …


Pow­er is ap­plied to the mic AF out­put line through an ex­ter­nal bi­as­ing re­sis­tor.  This meth­od is typ­i­cal of Ele­craft, Heil, and Icom electret mi­cro­phones.  If the op­ti­mal val­ue of this re­sis­tor is not spec­i­fied in your mi­cro­phone’s doc­u­men­ta­tion, then you should re­quest this in­for­ma­tion di­rect­ly from the man­u­fac­tur­er.


The pre-am­pli­fi­er is bi­ased in­ter­nal­ly ei­ther from an in­ter­nal bat­tery or from pow­er pro­vid­ed by the trans­ceiv­er.  This meth­od is com­mon to Ken­wood and Yae­su electret mi­cro­phones.  They put the bi­as re­sis­tor in­side the mi­cro­phone hous­ing, so you should not ap­ply ex­ter­nal bi­as.  (Of­ten these mi­cro­phones will in­clude a DC block­ing ca­pac­i­tor in the mic AF out­put line to pro­tect your ra­dio.)


Dynamic mi­cro­phones rare­ly have a built-in pre-am­pli­fi­er, and most that do are bi­ased in­ter­nal­ly.  How­ev­er, a very small num­ber of pre-am­pli­fied Icom dynamic mi­cro­phones do re­quire ex­ter­nal bi­as­ing.  If your dynamic mi­cro­phone does not have cir­cuit­ry to pro­tect its trans­duc­er, then mis­tak­en­ly ap­ply­ing an ex­ter­nal bi­as will dam­age it!


The best way to en­sure that you are prop­er­ly con­fig­ur­ing the IMA jump­ers is to “know” your mi­cro­phone(s).  Yes, our IMA User’s Guide will get you start­ed.  How­ev­er, much of its con­tent is de­rived from in­for­ma­tion that has not yet been ver­i­fied by hands-on test­ing.  So your saf­est re­course is to know the el­e­ment type, pin-out, and bi­as re­quire­ments of your mi­cro­phone(s).

In ad­di­tion, many oth­er mi­cro­phones and head­sets be­yond those de­scribed in the User’s Guide can be used with the IMA, pro­vid­ed you know how they are wired.

App Note #4
IMA mic patch panel board with arrow indicating the built-in spacer

IMA: Do Not Remove Spacer

29 Feb­ru­ary 2008 – In De­cem­ber 2007 we learned that – while re­mov­ing the rem­nants of the break­a­way tabs – one of our K2 In­ter­nal Mic Adap­tor (IMA) cus­tom­ers had al­so mis­tak­en­ly re­moved the built-in spac­er on the left edge of the Mic Patch Pan­el board.  At that time, we ad­dressed this is­sue by fur­ther em­pha­siz­ing the im­por­tance of this spac­er in the IMA Quick Start In­struc­tion Sheet (QSIS).  More re­cent­ly we learned of a sec­ond oc­cur­rence of this as­sem­bly er­ror, prompt­ing us to raise this is­sue to the lev­el of an app note.


Most like­ly there was no men­tion of the im­por­tance of this built-in spac­er in the be­ta re­lease QSIS that ac­com­pa­nied our in­itial (Sep­tem­ber 2007) IMA de­liv­er­ies.  This spac­er en­sures that the IMA can­not slide off the K2’s Mic Con­fig­u­ra­tion head­er (FP-P1).  One cus­tom­er re­port­ed that with­out the spac­er, the en­tire as­sem­bly had even­tu­al­ly worked it­self loose.  This is more like­ly to oc­cur if you op­er­ate in a high vi­bra­tion en­vi­ron­ment with the tilt bail ex­tend­ed.  It may al­so be more like­ly to oc­cur if you fre­quent­ly re­con­fig­ure the jump­ers, due to the re­sult­ing lat­er­al forc­es on Mic Ex­tend­er sock­et J1.

Corrective Action

If you re­ceived your IMA kit pri­or to Jan­u­ary 2008 but have not yet as­sem­bled it, you should down­load and use the lat­est IMA QSIS to en­sure that you don’t over­look this im­por­tant point dur­ing as­sem­bly and in­stal­la­tion.  If you in­stalled your IMA be­fore Jan­u­ary 2008, please in­spect your Mic Patch Pan­el board and ver­i­fy that you did not mis­tak­en­ly re­move this spac­er.  If you did, then please contact us to make ar­range­ments to re­place your IMA.

App Note #3

Headers Kit: Resistance Checks

17 Sep­tem­ber 2006 – The ex­pect­ed UN-KNB2 (J12) head­er board re­sis­tance meas­ure­ments are trans­posed in the Quick Start In­struc­tion Sheet (QSIS) that was in­clud­ed with in­itial ship­ments of our new rev. G Head­ers kit.  Our lat­est QSIS has the cor­rect val­ues, which are re­pro­duced here …

4.  Per­form re­sis­tance checks be­tween all ad­ja­cent con­nect­or pins, i.e. 1-2, 2-3, 3-4, etc..  They should all be “open” ex­cept for …
o     J14-7,8,9 – which should be ze­ro Ohms.
o     J12-1,2 – which should be be­tween 260 and 289 Ohms.
o     J12-5,6, – which should be be­tween 267 and 297 Ohms.

5.  Al­so, meas­ure the re­sis­tance be­tween J12-1 and J12-6.  It should be be­tween 86 and 96 Ohms.

The re­main­ing app notes are in­cor­po­rat­ed in­to Head­ers kits and boards that shipped af­ter Sep­tem­ber 2, 2005 …
  • The res­o­lu­tion for app note #2 was to pro­fes­sion­al­ly mill the rev. D board to al­low ac­cess to RF-L4.
  • The res­o­lu­tion for app note #1 was to pro­vide SIP con­nect­ors with long­er pins (318 ver­sus 230 mils) for the UN-K60XV.

App Note #2

Rev. D Headers PCB: RF-L4 Access

2 Sep­tem­ber 2005 – An is­sue has been iden­ti­fied where the rev. D UN-K60XV head­er board par­tial­ly blocks the ad­just­ment slot of L4 in the 80/160m band­pass fil­ter (as shown be­low left).

Partial blockage of RF-L4 by the UN-K60XV PCB Notch cut into the UN-K60XV PCB

To al­le­vi­ate this ob­struc­tion, we rec­om­mend cut­ting a small notch in the board (as shown above right).  This may be eas­i­er to do be­fore pop­u­lat­ing the board with parts.

App Note #1

Headers Kit: Longer UN-K60XV Pins

30 Au­gust 2005 – Do not in­stall the orig­i­nal­ly sup­plied “short” male ter­mi­nal-strip con­nect­ors on your UN-K60XV!

An is­sue has been iden­ti­fied with re­gard to the male con­nect­ors in­clud­ed with your kit.  In or­der to clear band­pass fil­ter in­duc­tors L2 and L4, the UN-K60XV re­quires con­nect­ors with long­er pins than were orig­i­nal­ly sup­plied.  There­fore, please use the en­closed con­nect­ors with 318 mil con­tacts for your UN-K60XV.

If you pur­chased our “Head­ers PCB (as op­posed to our “Head­ers Kit”), please note that the UN-K60XV board re­quires con­nect­ors with long­er con­tacts than the oth­er boards.

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