locked Re: Using the FlexRadio IQ channel with WSJT-X and MAP65 #Q65 #map65 #FlexRadio #Windows10

Bill Somerville


as you think it is a simple software job to synchronize  pair of independent I/Q data streams, then I propose you tell us the algorithm to do so. You must decide which I or Q sample in one stream is taken at exactly the same time as an I or Q sample respectively from the the other stream. Given that all that is received over an audio channel used to convey I/Q data is a continuous stream of samples, how do you propose to identify the exact capture time of samples with respect to the other continuous stream of samples?

IMHO the only way to do this is either to have timing information embedded in the data streams (that is not what happens here), or the two streams are interleaved at their sources such that each pair of I/Q samples is transmitted as a pair of pairs, i.e. a 4-channel interleaved data stream.

I don't know where you got the information that the Flex Radio multi-slice SDRs use a common clock for all ADCs, which may well be the case but, once those ADC samples are divide into two independent streams the synchronization information is lost!

Is the Flex Radio SDR software able to deliver *interleaved* I/Q data for two or more slices? If so then doing so at an 96000Hz sample rate is exactly what MAP65 needs for polarization diversity. If not then there is no way to proceed IMHO.


On 14/10/2021 12:51, Amos Sobel 4X4MF wrote:

1. WSJT-X accepts the IQ stream it does create almost similar  FT8 results as the base band.

3.1 I am using an H/V Yagi with symmetrical horizontal and vertical 10 by 10 elements  on the same boom.
3.2 Flex 6600 has 2 antenna inputs with a 16 bit A/D converters on each antenna input creating a  base band and an IQ data stream. Both ADC operate from the same clock.
3.3 Merging the 2 data streams into an interleaved single stream appears to me as a simple software job that can be done by WSJT-X or Flex.

Amos 4X4MF

-----Original Message-----
From: main@WSJTX.groups.io <main@WSJTX.groups.io> On Behalf Of Bill Somerville
Sent: Thursday, October 14, 2021 1:20 PM
To: main@WSJTX.groups.io
Subject: Re: [WSJTX] Using the FlexRadio IQ channel with WSJT-X and MAP65 #Q65 #map65 #FlexRadio #Windows10

On 14/10/2021 08:47, Amos Sobel 4X4MF wrote:
I have recently discovered that WSJT-X v.2.5.0 does accept the DAX IQ 
RX audio channels of my Flex 6600 instead of the DAX Audio Rx I did 
use for years.
1. Does WSJT-X take advantage of the additional information in the IQ 
stream in FT8?
2. Same question for Q65.
3. I have an H/V antenna connected to dual 2m transverter connected to
2 instances of WSJT-X running Q65. Is there a way to combine those 2 
channels same way as MAP65 does?

Amos 4X4MF
Hi Amos,

1) no WSJT-X does not currently understand I/Q data, you will get some decodes by selection one of the I or Q channels but that is sub-optimal and you should use a base band audio stream of up to 5 kHz bandwidth as input.

2) Q65 is no different, the front end audio processing in WSJT-X is the same for all modes.

3) I have explained this before to you, for polarization diversity mode
MAP65 requires a pair of synchronized I/Q data streams. That can only happen if the two data sources are received from co-located aerials (receiving the same wave-front), use a pair of ADCs sharing a common clock, and the two data streams are interleaved so that MAP65 can process each sample together with its partner from the other ADC (other polarization). As far as I know none of this is possible using a Flex Radio multi-slice SDR since the I/Q data sources are independent (think Humpty Dumpty https://en.wikipedia.org/wiki/Humpty_Dumpty, once broken some things cannot be easily reassembled!)


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