Yep - the K2 uses LM380, but the Sierra uses only an LM386 as headphone amp. My ill formulated sentence. But it doesn't matter - its all AF dBs.
My point is that the Sierra and the K2 uses an IF amp MC1350 before the product detector 602 (612, NE, SA ...), and gets a 'proper' AGC. The K2 is of course a better design since it uses a TUF-1 mixer (w. pre- and post amp) in stead of the 602 mixer. But the K1 - a later design then the Sierra and K2 - is imo one step back and down by not having an IF amp. The main rcvr guts of the K1 looks something like: 602 MIXER - XFIL - 602 PROD DET - LM386 AF PRE AMP - LM380 AF POWER AMP There is no IF amplification, and the AGC is based on the very slow CW AF signal. Anyway - it is a piece of cake to mod the K1. Quite a few of the other QRP rigs (in addition to the Sierra) from the period are 602-1350-602. I just wanted to know why they chose the all AF way. I guess someone has asked before - but the answer is imo not all clear. http://elecraft.365791.n2.nabble.com/RE-Re-K1-AGC-time-constant-and-how-to-radically-improveK1-AGC-td388515.html Roy RF Tinkerer On Sat, Oct 18, 2014 at 9:37 AM, Don Wilhelm <w3...@embarqmail.com> wrote: > Roy, > > I think one of the reasons for the change from the MC1350 to the NE612 > followed by the LM386 was due to the fact that when the K1 was designed, > the MC1350 in its DIP format was "not to be used for current designs". > Yes, the MC1350 is still available in SMD format, and Elecraft has designed > a carrier board that allows its use in the DIP format holes (for the K2 > ongoing support). > > To redesign the the K1 to use the MC1350 would be challenging. The AGC > system would have to be changed to use that part. There is nothing wrong > with the "dual NE612" designs - there are several out there, and they > perform quite nicely. > > BTW - the K2 used the LM380-8 audio amplifier, not the LM386. > > 73, > Don W3FPR > > > On 10/17/2014 9:50 PM, r j wrote: > >> Well ... Thanks for the history. One can also look at Elecraft's website >> >> http://www.elecraft.com/about_elecraft.htm >> >> >> But my question remains: Why did the (very early) Sierra and the (first >> Elecraft product) K2 have IF amp (MC1350 - and of course the standard AF >> amp LM386), but the K1 was equipped with no IF amp but two AF amps (LM386 >> and LM380) and an accordingly somewhat problematic AF based AGC. >> >> Thanks. >> Roy >> RF Tinkerer >> >> On Sat, Oct 18, 2014 at 8:34 AM, Eric Swartz - WA6HHQ, Elecraft < >> e...@elecraft.com> wrote: >> >> More history - Elecraft was formally created July of 1998. (We began >>> working on the K2 design well before that.) >>> >>> We shipped the first 100 K2 Field Test Units January and Feb. of 1999. >>> We >>> took orders for production K2 kits at Dayton in May of 1999. >>> >>> We followed that with the K1, then the KX1, the K3, and most recently the >>> KX3. >>> >>> 73, >>> >>> Eric >>> elecraft.com >>> >>> >>> > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
