[Elecraft] [KX3] SDR transmitter issues?

[Fred Smith]

I agree after rereading all of his post and charts twice they seem to be
flawed, again by someone without a real radio to test. He does seem somewhat
confused about the measurements of the QST labs and that of Rob Sherwood
both of which have had hands on testing.

IMHO only, a Flex is a nice bench setup but any SDR radio needs to operate
without a computer hooked to it all the time to function. I have not owned
one but have considered a 1500 if I find one reasonably priced.


73,
Fred/N0AZZ
K3 Ser # 6730--KX3 # 5210--K2/100 # 6470-KAT100
P3/SVGA--KAT500--W2
Amps Elecraft KPA500 HF/6m--Alpha's 9500 HF--87A HF--Mirage B-5030-G
300+w--(2) B-5016-G's 165w 2m



-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of David Anderson
Sent: Monday, December 30, 2013 8:52 AM
To: Rick Stealey
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] [KX3] SDR transmitter issues?

Yes I was confused by that too, it appears that Leif has adjusted the TX
noise figures from the QST dBc/Hz to a bandwidth of 500 Hz which is what QST
use for RX measurements.

Leif has not actually measured the K3 or KX3, just used the QST results (the
graph of "composite noise" and converted them for his purpose of showing
differences between receiver and transmitter noise. He has measured the
particular brand that exhibited very poor noise sidebands on transmit.

David Anderson GM4JJJ

> On 30 Dec 2013, at 14:34, Rick Stealey <rstealey at hotmail.com> wrote:
> 
> 
>> 
>> With regard to SM5BSZ's SDR wideband-noise performance table
(http://www.sm5bsz.com/dynrange/dubus313.pdf):
> 
> 
> Something doesn't jive with the table in the above report.
> I spot checked by looking up the Flex5000A in July 2008 QST, fig 3.
> QST shows wideband noise never gets worse than -120dbc, although the
report says it is -77 at 350 KHz.
> And (as I remember) the K3 report from QST showed phase noise way out at
the extremes of the meausrement dropping off much more than this author
reported, down into the range of -155 db.
> 
> Am I reading something wrong?  Apparently this report is not recent
because the worst performer of late (from QST measurements)  has been the
FT3000.  Too bad SM5BSZ didn't comment on it.
> 
> Rick  K2XT
>                         
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