Hi
I have tried to improve my IMD test setup. It is far from perfect, but I
have got rid of the broadcast station by bulding quick and dirty Xtal
4 MHz oscillator. It is built using a BC547 NPN bipolar transistor.
http://ea1abz.ure.es/XTAL.jpg
This is the beaufitul 4 MHz signal as received
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
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
Ramiro,
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
Geoffrey Mackenzie-Kennedy escribió:
Hi Ramiro,
Unfortunately I do not have a K3 to test because my receivers are
homebrewed.
That is a very interesting thing. I have also homebrewed receivers. They
are far from perfect but I love them, hi.
I still believe that the IMD is generated by
Sorry for being slow to reply.
Oh yes, a coil wound on a core made from Ferrite or Powdered Iron will
be a source of IMD products, the culprit being the core. The level of the
IMD products generated by a core depends on a number of factors, which we
could discuss Off List if you wish.
While I
Please stay on the list, guys, this is interesting stuff that I'm sure many
would like to hear more of.
David
G3UNA
Sorry for being slow to reply.
Oh yes, a coil wound on a core made from Ferrite or Powdered Iron will
be a source of IMD products, the culprit being the core. The level of the
Hello all
As David suggested we continue the discussion on the list. I have done
some new poor man tests, using a local AM carrier on Medium Wave at 917
KHz. For generating the other tone, I am using the same home made DDS
generator as before. At this lower frequencies the signal generated by
You do know that you cannot do valid IMD sweep measurements with AGC on?
First thing I have to do for any measurements is turn off the AGC and set
fixed levels. Particularly very fast config of fast AGC won't work. It
won't be valid for absolute measurements, but the bandwidth needs to be at
Thanks Guy for the explanations about IMD measurements. I need a signal
generator to do better tests and get rid of the need of receiving a
broadcast carrier. I was thinking in building a simple Xtal oscillator
and some attenuators.
73, Ramiro. EA4NZ
Guy Olinger K2AV escribió:
You do know
Hi Ramiro,
Unfortunately I do not have a K3 to test because my receivers are
homebrewed.
I still believe that the IMD is generated by something outside of the
radios, one reason being that your results from the K3 and the FT-897 are
not very different. The differences between the AGC-S, AGC-F
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