[Elecraft] K3 & ADAT ADT-200A by HB9CBU

[Bill W4ZV]

Nico Palermo, IV3NWV wrote:
> 
> 
> If we follow the definition of BDR as made by ARRL tests you are right.
> Unfortunately this definition does not give an exact idea of the true
> dynamic
> range of a receiver.
> I can demonstrate, and I think that Phil can do it as well with his QS1R,
> that if you feed a so called SDR with a + 7 dBm (S 9+80) carrier
> interferer,
> you can comfortably listen to a - 104 dBm (S 4) signal which is 2 kHz
> apart
> the interferer.
> 

In that case the BDR would be 111 dB, would it not?  I believe the K3 was
measured at BDR of 140 dB at 2 kHz spacing on 14 MHz in the most recent ARRL
test.  Not that we would actually try to operate so close to such a strong
signal on CW due to key clicks, etc, but BDR results at wider spacings are
very important if there are other stations on the same band (e.g. one on SSB
and one on CW in Field Day or during a DXpedition like VP6DX, or if you had
a close neighbor on the same band).   

Can you briefly explain why you feel ARRL's definition of BDR below is not
correct?

5.7.1 The purpose of the Blocking Dynamic Range Test is to determine the
level of gain compression, or desensitization, that occurs as a result of
another signal on a nearby frequency. The blocking dynamic range is the
difference between the level of the noise floor from the level of undesired
signal that produces a 1 dB decrease in a weak desired signal. Frequencies
of 3.520 MHz, 14.020 MHz, 50.020 MHz, 144.020 MHz and 432.020 MHz are used
for this test as appropriate for the DUT. The calculation is as follows:
Blocking Dynamic Range = Blocking Level - Noise Floor (expressed in dBm)

73,  Bill  W4ZV

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