- According to the ARRL, the Flex 6700 has 14 dB worse preamp-off
BDR than the K3.
- If you turn the Flex's preamp ON, the BDR is probably 24 dB (or
more) worse than the K3's. But if you turn the preamp on the 6700
OFF, its 2-kHz IMDDR3 is 8 dB worse than the K3's. You can't win
Here are the comparisons I pulled from ARRL's reviews of the Flex-6700,
Flex-6300 (April 2015) and K3 (January 2009) and VA7OJ/AB4OJ's noise
power ratio testing (http://www.ab4oj.com/test/main.html#NPR):
ARRL Labs shows the *blocking dynamic range* of the Flex-6700 to be
much *worse* than the K3 at all spacings with the preamps off. I've
added the MDS for comparison. Note: ARRL tested the original K3 with
KSYN3 *not the new KSYN3A*.
(preamp off) 20 KHz 5 KHz 2 KHz MDS
Flex-6700 126 dB 126 dB 126 dB -119 dBm
Flex-6300 127 dB 127 dB 126 dB -119 dBm
K3 142 dB 140 dB 139 dB -130 dBm
(preamp on) 20 KHz MDS
Flex-6700 (+20) 130 dB -135 dBm
Flex-6300 127 dB -128 dBm
K3 (+10) 138 dB -138 dBm
IMDDR3 is difficult to compare since ARRL did not report 2 KHz IMDDR3 with
the preamp turned on. This means that the Flex MDS is more than 10 dB
worse
than the K3. Note that the Flex-6700 drops by nearly 9 dB at 20 KHz if
the preamp (+10 dB) is turned on.
IMDDR3 20 KHz/Off 20 KHz/On 5 KHz/Off 2 KHz/off
Flex-6700 103 dB 94 dB 103 dB 103 dB
Flex-6300 92 dB 89 dB 92 dB 92 dB
K3 106 dB 103 dB 105 dB 103 dB
Using a different test protocol (Noise Power Ratio), AB4OJ/VA7OJ reports:
Noise Power Ratio 160M 80M 60M 40M
Flex-6700 no preamp 71 dB 73 dB 75 dB 74 dB
Flex-6700 +20 dB 76 dB 71 dB 71 dB 70 dB
K3 no preamp 82 dB 82 dB 82 dB not measured
K3 Preamp On 83 dB 82 dB 80 dB not measured
Note: the Flex was tested with 10 to 15 less noise power signal than K3 to
prevent ADC clipping.
73,
... Joe, W4TV
On 9/15/2015 6:28 PM, Jim Brown wrote:
On Tue,9/15/2015 1:52 PM, Tony Estep wrote:
On Tue, Sep 15, 2015 at 3:36 PM, Joe Subich, W4TV <li...@subich.com>
wrote:
....noise power ratio testing hides the fact by not providing MDS
values under each test condition *and* fails to indicate that even
with *no preamplifier* the total noise signal is more than 10 dB
*less*...
=========
I take this to mean that the test results are not comparable across
radios, and the SDRs are 10db worse than they show up on the
comparison chart. If this is true, it ain't good.
You've got the concept right -- the only difference is that 10 dB is not
a "hard" number -- it could be anything from 5 to 30 dB, depending on
how much test signal strength has been turned down, or preamp gain
removed, to get the input of the digital system out of clip!
Here are some comments by an engineer i trust.
73, Jim K9YC
= = = = =
- According to the ARRL, the Flex 6700 has 14 dB worse preamp-off BDR
than the K3.
- If you turn the Flex's preamp ON, the BDR is probably 24 dB (or more)
worse than the K3's. But if you turn the preamp on the 6700 OFF, its
2-kHz IMDDR3 is 8 dB worse than the K3's. You can't win
This all stems from the poor NF of their ADC and its low input voltage
range. The MDS of the Flex is only -118 dBm (according to Sherwood) with
the preamp off. (A K3's MDS with preamp off is -134 dB.) So you have to
turn the Flex's preamp ON to get good MDS. The 2-kHz IMDDR is then good,
but the BDR is terrible. Sherwood was so baffled by the weird responses
he saw that he simply put "A/D Limit" in the BDR column for the Flex.
He's still thinking about how to test it.
ARRL measured Flex's BDR, but only using the conventional method. To
properly assess the damage caused by an ADC at the front end, you have
to inject MANY signals into its input to give them a chance to combine
in phase and hit the ADC's clipping threshold. And ADCs do NOT
gracefully degrade.
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to li...@subich.com
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
