Alberto,
many thanks but I need just to "calibrate" (I should say invent) a
S-Meter for a BITX20a QRP Radio, and possibly double check the
sensitivity in some very relaxed way. My equipment:
- MiniVNA Pro with a 2 signal generators from approximately 0 to -60dBm
(not clear if they have an additional 12 or 18 dB attenuator inside).
Obviously it is not calibrated nor checked.
- The 2105
- Dummy load and VNA calibration set (short, open and 50Ohm dummy load)
- several SMA/BNC adapters (probably not enough ones)
I need the typical -73dBm and something in the -112dB range to be
satisfied. I don't know if and how much the MiniVNA is accurate, I
should ask some ham in ARI to double check it.
Toto I have a feeling we are not in Agilent anymore...
Giuseppe Marullo
IW2JWW
On 1/10/2014 4:50 PM, Alberto di Bene wrote:
On 1/8/2014 11:13 PM, Alan Melia wrote:
/Hi Alberto it is quite interesting to continue that test with no
attenuator
but the shells of the coax plugs connected together. I would guess
with the
gear you have the resultant would be at least 120dB down........but
this is
not the case for all signal generators!/
Hi Alan,
quite true. I performed the test you suggested, using as generator a
Rohde&Schwarz SMDU
that has a calibrated output down to -140 dBm, so it must be well
shielded...
I used 10 MHz as frequency, and, given that the settings of this forum
do not allow HTML (why ?)
these are the links to the screen captures stored on my Dropbox account.
As selective voltmeter I used the ELAD FDM-S1 receiver together with,
guess what... Winrad :-)
This is what I see with the Hatfield attenuator set to its maximum,
i.e. 100 dB :
https://dl.dropboxusercontent.com/u/15089947/hatfield-100dB.gif
Setting it to 0 dB gives this result :
https://dl.dropboxusercontent.com/u/15089947/hatfield0dB.gif
So you can see that the difference between the two measures is just 88
dB, not the theoretical 100...
And it is almost all to be attributed to internal leakage of the
attenuator, because, excluding the attenuator,
and just connecting together the two BNC shells, leaving the center
pin unconnected, gives this :
https://dl.dropboxusercontent.com/u/15089947/hatfield-shells.gif
So the Hatfield attenuator IMHO can be fruitfully used only if you do
not pretend from it the utmost
precision at high attenuation settings.
73 Alberto I2PHD
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