[Elecraft] Update to KSYN3A FAQ (some measured dynamic range numbers)

Sat Feb 14 15:57:30 EST 2015

Hi Johhny,
I'll probably get flamed for saying this, or someone more knowledgeable that I will point out how ignorant I am, but here is my layperson's understanding of this issue:
Assuming a MDS of -128 dbm, and an S9 signal equivalent to -73 dbm, IMD will begin to be a problem when two out of passband signals combine as follows:
IMDDR      Signal causing IMD = Noise Floor
55 db    S960 db    S9 plus 5 db65 db    S9 plus 10 db70 db    S9 plus 15 db75 db    S9 plus 20 db80 db    S9 plus 25 db85 db    S9 plus 30 db90 db    S9 plus 35 db95 db    S9 plus 40 db100 db    S9 plus 45 db105 db    S9 plus 50 db
You can see that if your rig has an IMDDR of 90 db, it would take a signal S9 + 35 db before you would likely notice any adverse affects from IMD caused by two out of passband signals (at the required spacing).
So, a person who has a rig with an IMDDR of say 95 db would only notice an improvement in the IMDDR when they are exposed to two out of band signals causing an IMD product when those signals are more than S9 plus 40 db.  The question you need to ask yourself is, how often are you faced with that situation?  The constant pursuit for improved IMD performance, it seems to me, is a worthy goal, but whether it benefits a particlar amature operator depends on whether he or she is faced with two out of passband signals that combine with the spacing required to cause an IMD product in his or her rig, AND the number of times those signals are sufficiently strong to exceed the IMDDR of their rig.  For some contestants, this is a BIG factor, but for other folks it rarely matters. It all depends on your operating environment....

I'm am sure this is not 100 correct, as I am not an engineer, but you should get the general idea  
73,

Bob/AA6VB

      From: Johnny Siu <vr2xmc at yahoo.com.hk>
 To: Wayne Burdick <n6kr at elecraft.com>; Elecraft Reflector <elecraft at mailman.qth.net> 
Cc: "Elecraft_K3 at yahoogroups.com" <elecraft_k3 at yahoogroups.com> 
 Sent: Friday, February 13, 2015 4:19 PM
 Subject: [Elecraft] Update to KSYN3A FAQ (some measured dynamic range numbers)

I must admit that understanding those figures are beyond my knowledge.  In practical terms, if I can now hear a below S1 cw weak signal 10KHz away from a S9+60db station before upgrade, what will be the improvement after the installation of KSYN3A assuming operating under the same condition?
Such a demonstation was given to me when I visited Icom HQ in Osaka last year in the announcement of the IC7850/IC7851.  Again, IC7850 is known foir extremely low phase noise.
Can any elecrafters interpret the improvements in an understandable layman terms?
73
Johnny VR2XMCK-Line + KX3 + HR50
       寄件人︰ Wayne Burdick <n6kr at elecraft.com>
 收件人︰ Elecraft Reflector <elecraft at mailman.qth.net> 
副本(CC)︰ "Elecraft_K3 at yahoogroups.com" <elecraft_k3 at yahoogroups.com> 
 傳送日期︰ 2015年02月14日 (週六) 7:34 AM
 主題︰ [Elecraft] Update to KSYN3A FAQ (some measured dynamic range numbers)

Hi all,

I've updated the KSYN3A FAQ with the following information regarding testing of a K3 with the new synthesizer performed by Rob Sherwood, NC0B.

* * *

Q: What is the approximate 2-kHz dynamic range (IMDDR3) of the K3 when using the new synthesizer?

A: Our tests show in excess of 105 dB with the narrowest filters, though there are many factors, and this should be considered approximate. (A very robust test setup is required to make these measurements.) Rob Sherwood tested a K3 with a KSYN3A and obtained the following results:

    2-kHz IMDDR3 with 200-Hz roofing and DSP filter = 106 dB
    2-kHz IMDDR3 with 400-Hz roofing and DSP filter = 103 dB

Rob will be posting this information in his receiver performance chart (http://www.sherweng.com/table.html) after he completes his full suite of tests.

* * *

The above numbers were used with Rob's permission.

73,
Wayne
N6KR

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