[hpsdr] CASMIR HF and HORTON HF Microdesigns v 4.1

[Eric Ellison]

Phil

Excellent write up and reasoning! In the overall an AKI on the Horton should
not add that much cost over what we get in return. Especially in the
quantities we are currently looking at for Janus.

Eric


-----Original Message-----
From: hpsdr-bounces at hpsdr.org [mailto:hpsdr-bounces at hpsdr.org] On Behalf Of
Phil Harman
Sent: Wednesday, July 12, 2006 11:09 PM
To: H. Gruchow; hpsdr at hpsdr.org
Subject: Re: [hpsdr] CASMIR HF and HORTON HF Microdesigns v 4.1

***** High Performance Software Defined Radio Discussion List *****

Hi Horst,

Let me try and explain our thoughts as to why we may put an AKM chip on the 
Horton board.

The project initially started out as one to build a very high performance 
sound card for the SDR1000 and other SDRs. Along the way we added many 
features that are SDR specific and will never be found on any commercial 
sound card e.g PTT input on the mic in. By adding the OZY board we can 
provide a parallel port interface to the SDR1000 over USB so we only need 
one connection between Janus and OZY to the PC.

We are very close to achieving this goal and I am sure many folks that have 
purchased an Atlas backplane are going to be very satisfied when using the 
Janus and OZY with their SDR1000 etc.

When designing the Janus I allowed for fully balanced inputs - a feature 
very high end sound cards have. I did expect that we would be able to 
connect this input directly to the capacitors of a QSD but this required too

many design compromises so instead we ended up with a sound card - a very 
good sound card at that.

In order to use the balanced inputs of the Janus directly with a QSD we are 
going to need some additional, low noise figure, modest gain after the 
capacitors.  We could do this on the Horton board and then feed these leads 
into the balanced inputs of the Janus.   We think there is a better way - we

are not building a sound card replacement any more - so use the same 
amplifier to connect to the QSD and optimally drive the AKM ADC.

We still use the Janus for its microphone, line-in, line-out, headphones, 
PTT  so is this really a lavish waste of money - if we purchase AKM chips at

Atlas volumes then I don't think so.

This is all still in the melting pot - we may not use a QSD in which case 
the mixer we do use may have enough gain to overcome the noise figure of the

Janus card and we can use the balanced inputs anyway.

The HPSDR is about performance, and whilst we do have an eye to cost it's 
not paramount in our thinking and will take second place to producing 
something that really pushes the envelope. Even so, once we have a complete 
radio working I expect it to be very cost competitive.

The I and Q Tx audio exists in PWM format on the Atlas bus.  All that is 
needed is to add a simple LPF and we have audio for ANY exciter board that 
sits on the bus in the future. If you can do this why would you run the I 
and Q audio  into Janus then out over plugs and sockets using screened 
cables and into the exciter board? Yes,  we have 'wasted'  a few $'s of 
components on the Janus board but this seems to me to be justified in an 
more elegant solution.

Hope that clarifies how we got here and were we going in the very near 
future (but not any further out!).

73's Phil...VK6APH







----- Original Message ----- 
From: "H. Gruchow" <horst at needles.de>
To: <hpsdr at hpsdr.org>
Sent: Wednesday, July 12, 2006 10:58 PM
Subject: Re: [hpsdr] CASMIR HF and HORTON HF Microdesigns v 4.1


> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Alex,
> this is something I do not understand as well. So, why do all the
> efforts and build Janus and not use it? As far as I understood Janus has
> all provisions for 'receice' and 'transmit' audio. So, why reinvent the
> wheel once again and use another expensive AKM chip?
>
> I need some more explanation as also obviously Alberto does.
>
> 73
> Horst
> DL6KBF
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