[Elecraft] KX3 AM-breakthrough

[Igor Sokolov]

Hi Klaus,

>Matt and Don, if this is a problem with _any_ zero
>frequency IF (direct conversion) receiver then the KX3's
>concept would be a design error. ( I hope it is not.)

It is not a design error. Simply every design has it's own limitations.

>If I switch to RX SHIFT I will have a receiver with the
>most advertised KX3 feature, narrow spaced dynamic range,
>dropping to values of rigs of the last century, like IC-735
>or Lowe HF-235 or Drake SW8.
>(see http://www.sherweng.com/table.html)

Please compare apples with apples (not with oranges). KX3 is a portable 
travel radio with possibility to be used with internal batteries. Compare it 
with the similar stuff like FT817. Besides even without roofing filter and 
with 8 kHz IF it has much better DR then IC735 and many others.

>Additional I would have thrown the money for the roofing filters
>out of the window, as we say here in Germany.

That is the way I thought first, when I have discovered the direct AM 
detection problem. Then I realized that this problem only exists part time. 
All the other time I can use roofing and dual receive. Therefore your money 
are not thrown out of the window.
My KX3 is SN 051. Unlike me, you could find the information about direct 
detection of KX3 with zero IF setting here on the reflector, prior to 
purchase. The problem exist mainly in Europe and many of the US customers 
are not affected.
Yes, this design has some limitations but still IMHO this is the best radio 
of its class and it costs every dollar we have paid for it.


>I hope there is a possibility of rejection by software, but I
>have no expertise in SDR at all.

Wayne once wrote to me that he may try to enable dual receive even with 8 
kHz IF but so far it is not implemented. I doubt that direct AM detection is 
possible to be rejected by software.

>No one of Elecraft has answered up to now, so I stay curious.
Did you send message to elecraft technical support? Or do you expect them to 
answer your concerns here on the reflector? They sure are not obliged to do 
the latter.

BTW, later you may discover couple of other issues  with KX3 which are not 
that obvious and which I have already discovered. Or you may just search 
this reflector and find out.

73, Igor UA9CDC

-- 
>73 Klaus DF1TL

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