[hpsdr] Janus Rev B Update

[Phil Harman]

Helmut,

The opposite sideband suppression  is a function of the  amplitude and phase 
balance between the  I/Q transmit signals.  From memory  60dB of suppression 
requires 0.01 degree of phase balance and 0.01dB of amplitude balance.  Both 
of these are within the capabilities of the PowerSDR software. But in 
practice you may be limited by what hardware the I/Q signals drive.  The 
carrier balance is dependant on the modulators used in the I/Q hardware and 
 >60dB is certainly achievable with relatively simple circuits.

With my current hardware the sideband suppression is much less that the 
intermods produced by my 100w PA so there is no real need to improve it.

No reason why the Janus board can't appear as a sound card in Windows - we 
just need to find someone to write a driver for it!

One reason perhaps for not doing that, at least for the HPSDR, is that we 
don't want to add any processing overhead on the data to/from the A/D/A 
converters. With the current code that Bill has added to PowerSDR we grab 
the A/D data directly off the USB interface and work on it immediately.

73's Phil...VK6APH


----- Original Message ----- 
From: "vk4str" <vk4str at netspace.net.au>
To: "Phil Harman" <pvharman at arach.net.au>
Cc: <hpsdr at hpsdr.org>
Sent: Saturday, May 13, 2006 8:05 PM
Subject: Re: [hpsdr] Janus Rev B Update


> Phil,
>
> I would like to know how good the opposite sideband / carrier suppression 
> in SSB mode is, have you measured that?
>
> Looking forward to your draft. My preferred option would still be that the 
> Janus board shows up as a soundcard in Windows OS.
>
> 73, Helmut
>
> Phil Harman wrote:
>> Helmut,
>>
>> I have the prototype Janus breadboard running on my bench - it runs full 
>> duplex fine. The PWM D/A converters in the FPGA work just fine also and 
>> no reason to think this wont be a great satellite rig. If I get time over 
>> the weekend I will post the latest draft of the protocol that we are 
>> using over the USB - from that you will see that full duplex is not a 
>> problem.
>>
>>>
>>> Hi Lyle,
>>>
>>> Nice job! However, as I have discussed before with Phil_H, this design
>>> may not be full duplex capable, ie useable to work a satellite
>>> transponder. I understand that PWM has certain limitations, please
>>> correct me if I am wrong.
>>>
>>> The AK5394A is used for RX and the processed audio is output on the
>>> speaker or headphone of the TLV320AIC23B.
>>>
>>> The TX audio is fed to the MIC input of the TLV with the only TX output
>>> option being PWM. The Line-out cannot be used if the speaker is in use.
>>>
>>> Would a DAC for TX output not be a better option? I somehow dont trust
>>> that the PWM option will be satisfactory for TX.
>>>
>>> 73, Helmut VK4STR
>>>
>>>
>
>
>
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