Frequently Asked Questions

The IMA (shown at right) is an assembly consisting of two tiny multi-layer circuit boards which fits between the K2’s Front Panel and Control boards.  Once installed, it eliminates the need to dis­as­sem­ble the front por­tion of the enclo­sure if you want to use your K2 with a different microphone.  The IMA can be quickly reconfigured for any of the pin-outs described in the KSB2 manual, after remov­ing just the left side panel of the K2 enclo­sure.  It even has built-in sup­port for con­fig­ur­ing the required exter­nal biasing; with seven jumper select­able resis­tances to choose from between 820 and 10 kΩ.

There are some trade-offs with the IMA …

1. It does not permit every signal on the left side of K2-FP-P1 to be connected to every signal on the right side.
   
   
2. It hardwires two signals (DOWN to MIC3 and GROUND to MIC7) directly across K2-FP-P1.

In practice this means that most newer Alinco microphones are not supported.  However, given the large number of microphones that are supported, and the dramatically greater convenience with which the K2 can be reconfigured for a different pin-out, the consequences of these limitations would seem to be a more than fair trade-off.

The IMA is designed to support all microphones offered by Icom, Kenwood, and Yaesu that are man­u­fac­tured with an 8-pin Foster mic plug.  Regrettably, it only sup­ports a few of Alinco’s early mics that use this connector.  The list of sup­ported micro­phones includes …

Photo courtesy of
Roy Frettsome, G4WPW

• Alinco : EMS‑5, EMS‑10, EMS‑11, EMS‑42.
• Elecraft : MD2, MH2, Proset‑K2.
• Heil : iCM.
• Icom : HM‑7, HM‑10, HM‑11, HM‑12, HM‑14, HM‑15, HM‑22, HM‑23, HM‑24, HM‑36, HM‑56.
• Icom : SM‑5, SM‑6, SM‑8, SM‑10, SM‑20.
• Kenwood : MC‑42, MC‑43, MC‑44, MC‑47, MC‑48, MC‑55, MC‑57, MC‑60, MC‑80, MC‑85, MC‑90.
• Ten-Tec : 708A, 709A.
• Yaesu : MD‑1, MD‑100, MD‑200.
• Yaesu : MH‑1, MH‑10, MH‑14, MH‑15, MH‑26, MH‑27, MH‑31 MH‑36.
• Yaesu : YM‑34, YM‑35, YM‑36, YM‑37, YM‑38, YM‑40, YM‑48.

The IMA can be quickly reconfigured for any of the com­bi­na­tions of con­nec­tor pin-out and exter­nal biasing resistance illus­trated at right, while an exter­nal adaptor is typ­i­cally cus­tom fab­ri­cated for just one.  An external adaptor would be a better choice if you wanted to use your K2 inter­change­a­bly with mul­ti­ple mics having dif­fer­ent pin-outs or bias­ing requirements.  Further, an exter­nal adaptor would be required for a micro­phone having a dif­fer­ent style con­nector than the K2, such as an RJ45 or RJ25.  An exter­nal adaptor would also be nec­es­sary for a micro­phone with dif­ferent MIC3 (DOWN) or MIC7 (GROUND) wiring – as is the case with Alinco’s newer mics – since these signals are hardwired on the Mic Extender board.

Something else to consider is that frequently changing the jump­ers will even­tu­ally wear off the gold plat­ing from both the jump­ers and the jumper block.  However, in normal use this won’t be an issue since all con­nec­tors and jump­ers have 30 µ" (micro-inch) gold plated con­tacts which are rated for at least 100 instal­la­tion and removal cycles.

No, not “on board”.  However, if you add RX audio support on the K2’s Front Panel circuit board, then the IMA can route the signal to the mic connector.  Referring to the IMA schematic diagram at right, the best way to do this would be to put RX audio on the “DOWN” pin on the K2 Front Panel circuit board, which in turn is hardwired to MIC3 on the Mic Extender board.  This way it will always be on MIC3 no matter how you configure the jumpers.

Doing this would require that you also cut the existing “DOWN” signal trace on the K2 Front Panel circuit board to disconnect it from FP-P1.  Other solutions are possible.  For example, instead of cutting the trace on the Front Panel board, you could instead lift a pin on IMA-MEX-J1, but this approach would require hard­wir­ing the audio directly to the IMA.

Please contact us if you require further assistance.

Our “product requirements” focus group for the IMA insisted that we avoid using 2 mm pitch con­nec­tors and jumpers in favor of 0.100" pitch parts.  This require­ment only added to the design chal­lenge since 0.100" parts are 21% longer.  In addition, our man­u­fac­tur­abil­ity con­straints for the PCB were: 1) trace width and copper clear­ances shall both be at least 15 mils; and 2) there shall be no more than four cop­per layers.  (These con­straints were imposed to ensure man­u­fac­tur­a­bil­ity while con­trol­ling cost.)

Working within these requirements and constraints, the task of fitting the IMA between the K2 Front Panel and Control boards presented two seem­ingly impos­si­ble chal­lenges:

1. Making the Mic Patch Panel (MPP) board suf­fi­ciently nar­row so that it could sit at right angles in the 0.500" gap between the Front Panel and Control boards.
   
   
2. Mounting a mating socket for FP-P1 – the K2’s Mic Con­fig­u­ra­tion head­er ter­mi­nal strip – on the Mic Extender board, given that there’s only 0.170" clear­ance be­tween the posts on FP-P1 and the back of the Con­trol board.

Further complicating both of these chal­len­ges was the fact that the tails of a con­nec­tor and the leads of many other parts pro­trude from the back of the Con­trol board into the nar­row space be­tween the Con­trol and Front Pan­el boards.  Although for­tu­nate­ly there are very few com­po­nent leads in­trud­ing in­to this area from the back of the K2 Front Pan­el board.

Key to accomplishing the first chal­lenge was the deci­sion to hard­wire MIC3 to DOWN and MIC7 to GND on the Mic Ex­tend­er board.  Referring to the x-ray ren­der­ing at right which shows the two inner cop­per lay­ers, you can see that the Mic Patch Pan­el board’s nar­row width is pos­sible in part due to how dense­ly the traces are routed between the two connectors.  Excluding a 0.080" tall spacer on its left edge, its max­i­mum width is just 0.405 ±0.005".

The solution to the second challenge was to use a sur­face mount pass-through sock­et to mate with FP-P1 since it re­quires es­sen­tial­ly zero clear­ance be­yond the posts of the K2’s Mic Con­fig­u­ra­tion head­er ter­mi­nal strip.

Photo courtesy of Mark Raybould, G3XYS

Yes there’s plenty of room for both.  However, depending on where you originally installed it, the SMT CW tun­ing indi­ca­tor might need to be reposi­tioned.  For­tu­nately its exact location isn’t critical.  The photo at right shows one pos­si­ble loca­tion for it.  Although in hind­sight we would rec­om­mend a bit more clear­ance between it and the IMA, to allow for flexing of the Mic Patch Panel board while the jumpers are being inserted.

Although it’s not necessary, Mark has obviously removed the stubs from the break away tabs.  More importantly, he has also mistakenly removed the spacer along the left edge of the Mic Patch Panel board.  (It’s difficult to tell because we are viewing the board edge on.)  DO NOT REMOVE THIS SPACER!  Doing so will permit the IMA assembly to eventually fall off of the K2’s mic config header, espe­cially when the tilt bail is extended and/or when operating in a high vibration environment!  (Unfortunately, our original beta release assembly instructions did not metion that this spacer is a intentional feature of the IMA.  This point is now made very clear in our instructions.)

Since taking this photo, Mark reports that he has repositioned the CW tuning indicator PCB slightly to the left to allow for flexing of the IMA’s Mic Patch Panel board, and as high as possible to permit access to the set­screw on the multi-turn pot.  (Access to the set­screw when the front panel is installed only requires removal of the left side panel and the nearby 2D fastener.)

Photo courtesy of
Phil Carter, WD8QWR

Yes, although it may be necessary to reposition some of the “sidetone mod” com­po­nents which you tacked onto the back of the Control board.  Depending on the length of their leads and the required repositioning, it may be desir­a­ble to replace some of those com­po­nents with new ones, or to extend their leads. 

In the photo at right you can see that rather than repo­si­tion­ing the side­tone mod com­po­nents, Phil has instead covered the bot­tom portion of the IMA’s Mic Patch Panel board with elec­tri­cal tape to insu­late it from them.  If you study his photo, you can deter­mine that Phil has con­fig­ured the jumper block for the Icom pin-out, with 10 k of bias resistace.

Perhaps, although  we strongly discourage attempting to remove and replace K2-FP-P1 due to the pos­si­bil­ity of damag­ing the K2’s Front Panel circuit board.  Instead, it may be pos­si­ble to suf­fi­ciently clean P1’s con­tacts.  If you attempt this, be sure to remove all flux res­i­due from P1 before install­ing the IMA to avoid per­ma­nently con­tam­i­nat­ing the inter­nal con­tacts of sur­face mount socket J1 on the Mic Extender board.

It’s unlikely that it would.  For one thing, the Mic Extender and Mic Patch Panel boards both have dual ground planes as shown in the two very high res­o­lu­tion (2,000 DPI) photo-realistic renderings (top and bottom) at right.  Thus, all traces are shielded on at least one side, and on both sides except where they run between / under con­nector pads.

However we can’t say for sure that you won’t experience RF feedback since many other fac­tors can affect this condition, including:

• your antenna system’s design.
• your operating frequency.
• the proximity of your operating position to your antenna.
• the direction your antenna is (currently) pointing (if it’s rotatable).
• the routing of your feedline (if it’s balanced).
• your RF ground or the absence of one.
• your transmit power level.
• the microphone itself.

We haven’t received any reports of “hot mic” issues from any users.  However, one user has reported that a mic that had previ­ously been hot before the IMA was installed, is still hot afterwards.

The assembly and instal­la­tion instruc­tions would have you affix the self-adhesive decal (turned sideways) inside the left side panel of the K2 enclosure.  Its pur­pose is to pro­vide con­ven­ient ref­er­ence to the lay­out of the 3 × 7 jumper block.  It also shows how to con­fig­ure the exter­nal bias resis­tance for the three stan­dard val­ues called for in the KSB2 man­ual.  (You’ll note that four addi­tional bias resis­tances are avail­a­ble, yield­ing a total of seven from which to choose.)

We have no plans to offer just the PCB by itself.  However, if there were a suf­fi­cient demand for it, we could make the boards avail­a­ble in pairs on a 0.900" × 2.800" sheet, which is how they arrive from the manufacturer.  If offered, the sheet would retail for about $14.50.

Prior to installing nine of the ten available internal options, additional option supplied parts must first be added to the K2, and a small number of original parts must be removed.  This packaging strategy – of providing some K2 parts with the options that require them instead of with the base radio – is one of the reasons the K2 is such a bargain!

Packaging the K2 this way does have its tradeoffs: (1) a small amount of PCB rework is required to replace some original K2 parts; and (2) disassembly of the enclosure is required when adding most options.  For seven options this disassembly is extensive, requiring removal of either the rear I/O panel heatsink, the Control circuit board, or the Front Panel circuit board. 

Fully loading a new K2 with options entails the installation of 27 additional parts:  15 components and 12 connectors.  In some cases original K2 parts must first be removed to make way for these additional parts (i.e. PCB rework):

• Resistor RF-R88 is changed from 470 Ω to 2.7 kΩ.
• Resistor RF-R89 is replaced with a jumper wire.
• Jumper wires CTRL-R18 and CTRL-R19 are removed so that connectors CTRL-J1 and CTRL-J2 can be installed.
• Capacitor RF-C6 is replaced with connector RF-J15.
• Capacitor RF-C71 is changed from 82 pF to 120 pF.

Seven other original K2 parts must also be removed:

• Resistor RF-R90.
• Capacitor RF-C167.
• Jumper wires RF-W1,W2,W3,W5,W6.

These changes – the removal of 13 original K2 parts and the instal­la­tion of 27 additional parts – 9 on the Front Panel board, 2 on the Control board, and 16 on the RF board – require at least partial dis­as­sem­bly of the K2 enclosure.  For seven options, extensive dis­as­sem­bly of the enclosure is required to initially prepare the K2 for their installation.

Initially, an “Option Ready” K2 is one without any internal options.  However, it has been upgraded as required in preparation for the installation of all of the options.  Where necessary, inexpensive option bypass headers are temporarily installed in place of each circuit board mounted option.

Going one step further, the detailed instructions in our Companion Guide describe how to seamlessly integrate these “option preparation” changes during the initial assembly process.  Beyond simplifying the task of adding the options, this approach also eliminates the need for any PCB rework.

Rework-free “Option Ready” K2 construction seamlessly combines initial assembly with all required “internal option preparation” changes.  This eliminates the need for the significant disassembly that’s normally required when adding most options.  Thus, an “Option Ready” K2 will be far easier to upgrade with options.  The time you’ll save adding the options will more than make up for the extra time that was required to build your K2 “option ready” in the first place.  You’ll also avoid the wear and tear that comes from repeatedly disassemblying the enclosure.

This approach also eliminates the need for PCB rework that’s normally required when adding some options.  It reduces the possibility of serious damage to the K2’s circuit boards, and can potentially result in a more reliable radio.  In the end you’ll save time, learn more, and have a more rewarding overall kit building experience.

The end result of both assembly methods is essentially the same; at least it’s supposed to be!  However, depend­ing upon your desol­der­ing skills and your access to spe­cial­ized desol­der­ing tools, the tra­di­tional assem­bly method might leave your K2 with serious circuit board damage after you’ve attempted to add some of the options.

To eliminate the possibility of circuit board damage while improving reliability, our “Option Ready” method has you build the radio so that no desol­der­ing is required when install­ing the options.  Until the options are installed, un-modules (simple option bypass headers) tempo­rarily take their place inside the K2.

It is only after the radio is completed and it’s time to add the options that the dif­fer­ence between the two methods truly becomes appar­ent.  The spe­cific dif­fer­ences are shown in the table below, which com­pares the assem­bly steps required to add all of the options.  (It doesn’t show all of the steps, just the ones that differ.)

As you can see, much less effort is required to add options to an “Option Ready” K2.  In comparison, a lot of additional work (that could have been avoided) is required to prepare a K2 that has been assembled using the traditional approach.  But what isn’t immediately obvious is that if you add the options one at a time, then you must (at least partially) disassemble and reassemble the enclosure many times over!

Building an “Option Ready” K2 requires …

1. Un-modules (option bypass headers).
2. All of the “unique” K2 PCB parts that are provided with the K2 internal options.  (In a few cases two different Elecraft® options provide the same K2 parts.)

If you buy a fully loaded (QRP or QRO) K2 to start with, then you will already have all of the necessary K2 PCB parts.  If you get some options with your K2, then you will have at least some of the parts you need.  If you are starting out with just a stock K2, then you will need all of the parts provided by our All Option Supplied Parts kit. 

If you are getting some options with your initial K2 purchase, then please continue reading below to deter­mine which of our indi­vid­ual parts kits you’ll need …

Building an “Option Ready” K2 requires 46 additional parts which are provided with Elecraft’s optional K2 internal expansion modules (options).  So the answer depends on which options you already have.  The more options you get up front before you start building your K2, the fewer additional parts you’ll need to obtain from us. 

Since there are 431 valid option configurations, it isn’t practical to list every possible combination here.  Fortunately, it is relatively easy to determine what’s required for any combination of Elecraft® options.  However, properly answering this question is sufficiently involved to warrant devoting a separate webpage to the subject. 

The table on the What Else Do I Need? page matches up our Duplicate K2 PCB Parts kits with the Elecraft® K2 options that provide the same parts.  Building an “Option Ready” K2 requires the additional parts listed in each row of that table, however you might choose to obtain them.

Yes you can, however you may not want to for the K60XV unless you will definately be installing it.  This is because the option ready preparations for the K60XV will require that you perform some realignment of the K2 when the changes are made and possibly a second time when the option is installed.

This concern does not apply if you wait to make the changes until you are ready to install the K60XV, since you’ll have to do this re-alignment then anyway.  It also does not apply to building an “Option Ready” K2 from the outset.  It is only an issue for upgrading an existing K2.  If you are intending to do a top to bottom realignment anyway, then this concern is not applicable. 

Another issue is that you must have the latest firmware (supplied with K2s since S/N 4060).

Please contact us if you have still have questions about making your existing K2 “option ready” the K60XV option.