++++++++++++++++ Date: Fri, 25 Apr 2003 15:51:27 -0700 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: Elecraft List , K6BJ list Subject: [Elecraft] Elecraft K2 Temperature-Compensated PLL Reference Upgrade We've just completed field testing of an easy-to-install upgrade to the K2's PLL synthesizer stage. The upgrade uses a thermistor and a few other components to temperature-compensate the varactor-tuned crystal reference oscillator. The compensation circuit reduces the reference oscillator's temperature coefficient by as much as a factor of 10. This will be of particular interest to those who use the K2 with the KPA100 option, or who frequently operate outdoors or mobile. All of the components are mounted on a small circuit board which replaces one of the existing resistor networks. This results in a clean, no-wires installation. The changes do not increase current drain. The PLL upgrade will be included free of charge with all new K2 kits starting today (s/n 3446 and up). Existing K2 owners can purchase the upgrade kit for only $19 (order number E850138). The upgrade kits are now in stock. You can get more information at: http://www.elecraft.com/order_form_parts.htm#K2%20Parts We'd like to thank John Grebenkemper, KI6WX, who designed the temperature-compensation circuit, as well as all of those who field-tested the upgrade kit. 73, Wayne, N6KR Eric, WA6HHQ ++++++++++++++++ Date: Fri, 25 Apr 2003 20:58:31 -0700 From: Wayne Burdick Organization: Elecraft To: "David A. Belsley" Cc: Eric Swartz WA6HHQ - Elecraft , Elecraft List Subject: [Elecraft] Re: Elecraft K2 Temperature-Compensated PLL Reference Upgrade "David A. Belsley" wrote: > > Eric: > I know when John first did some of the drift tests, there were > substantial variations in how badly different K2s were affected by the > problem. How does "one size fits all" work for this mod? Hi David, I'll take this question. I think Eric is already in bed ;) The degree to which an individual K2 will benefit from this mod depends on: - whether a KPA100 is installed (this heats the enclosure a lot faster) - whether the rig is used in temperature extremes - if it has had the BFO modification installed (p/n BFOMDKT, already present in the revision B K2) - the pre-modification temperature coefficients of various components in the PLL reference and BFO The overall TC (temperature coefficient) of a given K2, pre-modification, can vary over a wide range. If the operator perceives that the TC is already low, the PLL upgrade may not offer any advantage. What we know for sure is that the combination of the BFO modification (using the new, highly stable toroidal inductor) and the PLL upgrade (using thermistor compensation) produces truly excellent results. In fact we considered simply calling this the K2 TCXO modification, but it's really a "VCTCXO" (voltage controlled, temperature compensated crystal oscillator), which is a less well-known acronym ;) 73, Wayne N6KR +++++++++++++++++ Date: Sat, 26 Apr 2003 00:30:18 -0700 From: Wayne Burdick Organization: Elecraft To: "David A. Belsley" Cc: Eric Swartz WA6HHQ - Elecraft , Elecraft List Subject: [Elecraft] Re: Elecraft K2 Temperature-Compensated PLL Reference Upgrade "David A. Belsley" wrote: > One further point, if I may. Suppose one's K2 > does indeed have low TC. Will the addition of the thermistor mod now cause > over compensation, perhaps even producing negative temperature compensation > (in the opposite direction)? If the TC seems to be low, it could simply be because the K2 is being used in a relatively temperature-stable environment. Or the PLL TC and BFO TC could be cancelling each other out only on certain bands. To check for this, you could test drift on 17 and 10 m, where the VCO is in about the same range but the BFO is subtracted/added, respectively. You may find that drift is much worse on one than on the other. But even if the TC really *is* low, the PLL upgrade mod can only make it better. The upgrade kit includes a new highly stable reference crystal in addition to the thermistor compensation components. Every K2 tested during field-testing of the PLL upgrade showed a factor of about 5 to 10 improvement. Given the possible PLL/BFO TC cancellation scenario, you should certainly make the BFO modification at the same time to eliminate the BFO as a variable (unless your K2 is s/n 3000 and up; these already have the new BFO inductor). One other feature of the thermistor compensation circuit is that the amount of compensation can be fine-tuned (if you insist) by changing just one resistor value. Details on how to test the residual drift and tweak this resistor value are included. But such tweaking IS NOT REQUIRED or recommended. Some experimentally-inclined builders will want to do it anyway, which is why we include the info. 73, Wayne N6KR +++++++++++++ Date: Sat, 26 Apr 2003 16:42:32 -0100 From: "Julian (G4ILO)" To: "Elecraft List" Subject: Re: [Elecraft] Elecraft K2 Temperature-Compensated PLL Reference Upgrade That was the case when I ordered the BFO upgrade kit (which I still haven't installed.) I think the postage cost was about $7. 73, -- Julian, G4ILO. (RSGB, ARRL, G-QRP, K2 #392) G4ILO's Shack: http://www.qsl.net/g4ilo "Dave" wrote: David I think you will find the cost of post/packing might be less than that quoted on the Elecraft web site. When I ordered some of the other mod kits for my K2, they charged "cost" rather than the typical price on the shopping basket. My K2 "TCXO" kit is on order... Dave, G4AON ++++++++++++++++ Date: Sat, 26 Apr 2003 09:03:34 -0700 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: Jibeji Cc: Elecraft at mailman.qth.net Subject: Re: [Elecraft] Elecraft K2 Temperature-Compensated PLL Reference Upgrade Cost of shipping this to Europe is not $18. For a padded envelope I expect it is less than $5. We will email any Eu orderers with the actual expected cost. 73, Eric ++++++++++++++++ Date: Sat, 26 Apr 2003 09:52:11 -0700 From: Wayne Burdick Organization: Elecraft To: Larry Benko Cc: Elecraft List Subject: [Elecraft] Re: Elecraft K2 Temperature-Compensated PLL Reference Upgrade Larry Benko wrote: > Can both the temp. compensation upgrade and the > audio filter board be installed at the same time? Yes. We allowed for the audio filter when we designed the PLL reference PC board. 73, Wayne N6KR ++++++++++++++++ From: "Ken Wagner" To: "Larry Benko" , "Elecraft List" Subject: Re: [Elecraft] Elecraft K2 Temperature-Compensated PLL Reference Upgrade Date: Sat, 26 Apr 2003 12:55:15 -0400 Hi Larry: The new l'il PC board fits quite nicely right beneath the KAF board. I removed the KAF board when I took the picture. 73, Ken K3IU ++++++++++++++++ Date: Fri, 02 May 2003 13:33:21 -0400 From: WA9GQT at aol.com To: elecraft at mailman.qth.net Subject: [Elecraft] K2 Temp Comp PLL Mod Hi All! Found the problem. When I reinstalled RP3 CAL PLL worked OK. Everything was fine. Rechecked the Mod board and found a solder bridge between RC and RF resistors. I have corrected the board but not insatlled it yet. That seems to be why I could not do CAL PLL. 73, Rod WA9GQT K2 #1900 KPA100 +++++++++++++++++++++ From: "Len Koppl" To: Date: Sat, 3 May 2003 08:41:22 -0600 Subject: [Elecraft] K2 Temp Comp Upgrade Well, I built and installed the K2 Temp Compensated PLL Reference Upgrade last night. What a difference! The shack was uncomfortably warm last evening, and uncomfortably cool this morning, yet the rig stayed within 10 Hz of WWV on 10 MHz. For the last hour and a half, it has been right on 10.000.00. I highly recommend this upgrade. I do a lot of camping, and the K2 always comes along. Since I tend to camp at fairly high altitudes, the rig cycles through some wide temperature ranges. I am confident that the mod will do a good job under these conditions. 73, Len, KDØRC +++++++++++++++++++++ From: "Dave" To: Subject: Re: [Elecraft] K2 PLL temp upgrade - problem Date: Sat, 3 May 2003 18:11:17 +0100 Further to my last... If I read the upgrade instructions more carefully and checked in my K2 original manual, then I would have realised RP2 in my K2 is 82K and not 100K of the earlier models. I've removed the 10 K resistors from pins 1/2 and 3/4 and now my K2 performs as per the instruction sheet. The instructions may need clarification on this point? Just awaiting the K2 warming for a few minutes to do a proper CAL PLL. Dave, G4AON K2 #1892 ----- Original Message ----- From: "Dave" To: Sent: Saturday, May 03, 2003 5:46 PM Subject: [Elecraft] K2 PLL temp upgrade - problem > Hi gang > > The modification kit arrived in this mornings post. All went well until I > came to alignment and test. > > Connecting frequency counter probe to TP3, CAL Fctr and tapping BAND- gives > a counter reading of 12083.71, pressing BAND+ gives an unstable reading. > > Setting the K2 to 7000.1 KHz and connecting the counter probe to TP1, > running CAL PLL gives an initial reading of 11042.35 (approx.) and then > shows a "INFO 232" error. > > I can confirm that all supplied resistors measured their specified values, > L31 has been fitted and is marked 12uH, the BFO modification had previously > been carried out, there is a 2K7 resistor across pins 7 & 8 of RP2, 10 K > resistors have been added across pins 1 & 2 and 3 & 4 of RP2 and that X1 has > been replaced with the one supplied. > > I've checked the VCO alignment as per the manual (DVM to R30) and checked > that the K2 receives on all bands on more or less the correct dial reading > (error of about 3 KHz on 7 MHz and worse higher up due to not being able to > run CAL PLL). > > Other than asking for a replacement RP2 and reversing the modification, any > ideas appreciated. +++++++++++++++++++ Date: Sat, 03 May 2003 17:54:07 -0400 From: "David A. Belsley" To: Dave , Elecraft at mailman.qth.net Subject: Re: [Elecraft] K2 PLL temp upgrade - problem Dave: I hope your messages have had typos, because it is RP3, I believe, that is involved in the PLL temp upgrade, not RP2. best, dave belsley, w1euy --On Saturday, May 3, 2003 6:11 PM +0100 Dave wrote: > Further to my last... If I read the upgrade instructions more carefully > and checked in my K2 original manual, then I would have realised RP2 in > my K2 is 82K and not 100K of the earlier models. I've removed the 10 K > resistors from pins 1/2 and 3/4 and now my K2 performs as per the > instruction sheet. -- snip -- +++++++++++++++++++ Date: Sat, 3 May 2003 18:33:13 -0700 From: Bob Nielsen To: Elecraft at mailman.qth.net Subject: Re: [Elecraft] K2 PLL temp upgrade - problem No typo, although RP3 is replaced by the upgrade board. In early K2s with 100K RP2s, it is necessary to add a couple of resistors across parts of RP2. Bob, N7XY On Sat, May 03, 2003 at 05:54:07PM -0400, David A. Belsley wrote: > Dave: > I hope your messages have had typos, because it is RP3, I believe, that > is involved in the PLL temp upgrade, not RP2. > > best, > > dave belsley, w1euy -- snip -- +++++++++++++++++++++++ Date: Tue, 20 May 2003 09:16:03 -0700 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: Elecraft List Subject: Re: [Elecraft] K2 Temp. compensated PLL mod I would start with the recommended 3.7 xtal settings and then adjust them to your liking. They are only an approximate starting point, especially for TX audio settings with BF1t. 73, Eric Phil Wheeler wrote: > > Welcome back, Eric. > > I did the 14 xtal mod, the BFO mod and the PLL stability (thermistor) > mod. I did record the BFO freqs before I started. But when done, I > used the BFO settings recommended for the 3.7 (written on the envelope) > xtals in the SSB module instructions. > > Was I correct in assuming that with new xtals this would be the best > course vs. going back to the old settings? > > 73, Phil ++++++++++++++++++