[Elecraft] Elecraft technology

[Don Allen]

Bill Coleman wrote:

>On 9/4/03 12:40 PM, Sverre Holm at la3za@qsl.net wrote:
>
>  
>
>>I received an interesting comment that it is basically the architecture
>>of the K2 which is unique for a ham receiver, i.e. the single-conversion
>>design and the narrow ham-band filters at the RF input -
>>http://www.elecraft.com/Apps/why_is_the_k2_receiver_single.htm, and I
>>agree this is key to the K2's performance. I could rephrase my question
>>differently, why did it take until 1998 for this architecture to make it
>>into ham receivers, why didn't it happen say ten years earlier?
>>    
>>

Actually, it occured twenty years earlier (circa 1978 and 1979) with the 
original Ten-Tec Omni.  The original Omni was a ham-band only 9 MHz 
single-conversion design (9 MHz I.F.) with a high-level diode ring DBM 
up front in the signal path directly followed by an 8-pole 2.4kHz xtal 
lattice filter.  L.O. injection was xtal, and the linear PTO was 
non-synthesized, thus phase noise and reciprocal mixing was minimal.  
The R.F. amp was fixed-biased (you should never AGC the RF amp for best 
dynamic range), and the R.F. Gain control on the front panel actually 
controlled I.F. gain.

In fact, many CW ops changed out the 2.4kHz filter and installed a 
6-pole or 8-pole 500Hz filter, properly terminating the filter, and 
including a post-amp to make up for the extra  insertion loss.  The Omni 
Series B added xtal switching which allowed the 2.4kHz filter to remain 
inline, and cascading either a 1.8kHz 8-pole SSB filter or 500Hz CW 
filter - all at the same 9MHz I.F.

Since the original Omni series used audio-derived AGC, the audio filters 
(and, the audio notch) were within (not outside) the AGC loop.  
Therefore, the audio filters worked quite well, and were not "pumped" by 
a signal outside the passband of the combination of xtal and audio 
filter(s).

And, to carry this a bit, further - albeit not a single-conversion 
concept - the Sherwood Engineering' highly-modified Drake R-4C receiver 
uses a narrow-band (either SSB or CW bandwidth filter) in the first 
I.F., but uses a multi-conversion process after the "up-front" narrow 
filters to provide for more xtal filters in the 2nd I.F., Passband 
Tuning, and an I.F. notch circuit.

Thus, it was thought of and implemented before, but Elecraft's design is 
state-of-the-art and a kit - which makes it even more attractive.  Eric 
and Wayne did it right - period.  The fewer mixers in the signal path - 
the better.

73 es Best 2004 to all,
Don W9CW