[Elecraft] OMNI VII vs Elecraft K3

[FISCHER,GREG]

Hi Bob,

This is from the FAQ.  Hope it answers your question.

73
Greg


With a first IF of around 8 MHz, how can the receiver be 
general coverage?  Will there not at least be hole in the 
coverage around the IF frequency?

General does not mean continuous in this case. There is a 
small gap at 8.215 MHz. You may be able to tune to this 
frequency, or not, depending on the firmware. There is a 
trap circuit to suppress response at this frequency, so 
the receiver won't work very well within several kHz of 
8.215 MHz if it does allow you to tune there.



On Mon, 14 May 2007 14:03:30 -0700
  Bob Nielsen <nielsen at oz.net> wrote:
> 
> On May 14, 2007, at 1:53 PM, Bill W5WVO wrote:
> 
>> Anthony,
>>
>> I spent a long time lurking on the OMNI-VII Yahoo group 
>>and was  
>> primed to buy one -- until the K3 was announced. In 
>>addition to  
>> everything Greg says below, I think the most significant 
>>single  
>> difference between the two receivers is that the 
>>OMNI-VII uses a  
>> typical up-conversion scheme for the first IF, with its 
>>narrow  
>> filters in the 2nd IF. The K3 uses a down-conversion 
>>scheme at the  
>> first IF. This allows use of very narrow roofing filters 
>>in the  
>> first IF, while the OMNI-VII must depend only upon 
>>optimizing IF  
>> stage gain distribution to minimize close-in IMD through 
>>the first  
>> IF. They obviously did a good job of that, as the 80 dB 
>>2 kHz DR3  
>> shows, but it is expected the K3 will test significantly 
>>higher  
>> than that, most likely in the vicinity of the ORION-II. 
>>Of course  
>> that's speculation at this point, since the actual 
>>numbers aren't  
>> out yet, but it is well-informed, highly credible 
>>speculation.  :-)
>>
>> And you don't give away general-coverage receive 
>>capabilities, as  
>> you do with many ham-optimized down-conversion 
>>receivers. It is  
>> simply a brilliant design, IMO. I have one on order.
>>
>> Bill / W5WVO
> 
> That lead to a question I hadn't considered before.  How 
>is general  coverage in the vicinity of the first i.f. 
>achieved?
> 
> Bob, N7XY
> 
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