[CQ-Contest] Busted Reversed Beacon Network spots

XV4Y xv4y at nature-mekong.com
Sun Jun 9 21:38:29 EDT 2013

> Bret, before you attack SDR receiver performance indiscriminately, take 
> a look at Rob Sherwood's review of the KX3.

Hi Pete,

You are right about the KX3.
In its detailed report, Rob NC0B specifically comments that despite its good close DR3 the KX3 will perform badly in a contest environment.
The "digital conversion IF" is only in the vicinity of 1 KHz and image rejection is very low (around 70dB).
The KX3 will not suffer from having its AGC pumping because of strong adjacent signal, nor it will suffer from RMDR, but just from phantom signals coming from the opposite band.
If you have a S9+50dB at, let's say 2 KHz below (not uncommon in a contest), it will appear around S7 in your receiver, loud and clear.

Rob Sherwood table classification only use one index for ranking and it is the DR3 at 2 KHz on 20m with preamp off and using a 500 Hz filter.
It was meant to compare transceiver of the 90's that were using up-conversion circuits and thus having very good sideband and image rejection numbers.

The KX3 is a wonderful SOTA and portable radio; not designed to be a contest or DXpedition radio.

Yannick DEVOS - XV4Y
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