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Understanding the uBitX.

Ravi Miranda
 

Hi,

I understand that this may have been tackled before, but I'm trying to
understand the best way to resolve signals on my DIY uBITx Rx/Tx.

The attached pic shows the frequency response of my filter using NWT Lite.

In the conventional way, the USB and LSB can be shifted. But in the
case of uBITx the shifting is done by the LO2. Which means that if the
centre of the above filter is 11,058,109Hz, then the LSB will have to
be at 11,056,000 and the USB will have to be 11,060,000. which would
be +/-2KHz on either side of the BFO frequency. Any of the other
frequencies chosen at the three or four intersecting points on either
side of the centre would mean narrower filters and therefore good for
cutting out interfering signals. Is this interpretation correct?

Which then leads me on to the following:
For a Display frequency of 10MHz, the VFO frequency should be 55MHz?
The LO2 frequency should be offset as follows:
+/-2KHz from the centre of the Xtal filter (assuming 11058100Hz), LO2
should be set at 33943900Hz and LO2 set at 56060100Hz for USB.
Measuring the frequencies at VFO, LO2 and BFO indicate that
frequencies generated (using V1.2) are way off these expected values
and I was wondering if any one on the group had seen similar behaviour
from the code?

Many thanks.


Ravi/M0RVI

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