Posted by
Ramiro Aceves on
Nov 25, 2010; 9:56pm
URL: http://elecraft.85.s1.nabble.com/Re-K3-Rx-IMD-tp5768777p5775605.html
Thanks Geoffrey for the interesting information about IMD measuring. I
see that it is a difficult task, it implies using carefully made
equipment and care. Everything is out of my possibilities at the moment.
I have made these easy experiments just trying to have an explanation of
what occured in my K3 when tried to see aircraft reflections and got
duplicated reflections. While they are not perfect, these tests have
teached me implications of AGC-F/S and have duplicated a IMD problem
under more "controlled" circumstances.
Trying to obtain a decent test gear is a difficult task for me, and
perhaps it makes no sense to invest time and money on it. I am not a
receiver tester, just a curious person who likes to know why things
happen.
Anyway, since I changed AGC-F to AGC-S or even better AGC-off, I have no
longer received duplicated traces on the screen. If I change to AGC-F I
get consistent duplicated traces. I do not certainly know if the spurs
are generated out or inside the K3, I tend to think that the latter. But
who knows, perhaps the K3 receiver is not as perfect as many of us think.
Thank you, will keep in touch.
Ramiro. EA4NZ.
Geoffrey Mackenzie-Kennedy escribió:
> Ramiro,
>
> Some very good information about Combiners is published on Jack Smith's
> website (Clifton Laboratories), also how to perform "IMD" tests.
>
> The reason for using a lowpass filter between each generator and the
> combiner is to prevent the second harmonic of generator "A", for
> example, getting into generator "B", mixing with the fundamental of "B"
> to produce a third order product 2A - B. Similarly to keep the second
> harmonic of "B" out of "A". Any mixing of other harmonics can also
> result in "alien" third order products.
>
> If you build a "pretty" version, I would suggest that each generator be
> built in its own metal box, with all DC supply leads filtered. What you
> do not want is the generators talking to each other :-)
>
> Good luck with your project.
>
> 73,
> Geoff
> GM4ESD
>
>
> Ramiro Aceves wrote on Thursday, November 25, 2010, at 7:52 AM:
>
>> No problem. I cant resist what you propose. I am going to build Xtal
>> oscillator. I have a 4 MHz cristal here. The the combiner.
>> Keep tuned!
>>
>> Ramiro
>
>
>
>
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html