[hpsdr] Pennylane

[Phil Harman]

Hi Gordon,

Jeremy is quite correct in his explanation of the differences between
Penelope and PennyLane.

PennyLane makes use of the improvements we made to the Penelope schematic
when we developed Hermes.  There are two improvements.

1. We vary the power output by varying the DAC current rather than the
amplitude of the I & Q signals.  As far as I am aware most SDRs use the
latter method so Penelope is in good company.

This is really only an issue if you use Penelope to generate a very low
level signal - say less than 10mW. In which case you should place an
resistive attenuator on either the input or output of the LPF that follows
the DAC. That way you can drive the DAC harder and maintain a high S/N
ratio. Alternatively fit the resistive divider at the output and use the
low level output connector.

2. We split the PA stage into two gain stages to give a more constant
power output vs. frequency and more output on 6m.

If your current Penelope board meets your needs then there is no reason to
purchase a PennyLane board.

PennyLane will be plug compatible with Penelope and supported by all the
current HPSDR software.


73 Phil...VK6APH



> ***** High Performance Software Defined Radio Discussion List *****
>
> On Dec 21, 2010, at 2:00 PM, Gordon & Lois Duff wrote:
>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> I have Penny.  Why would I want Pennylane.  I looked in the archives and
>> could find no description of what I would gain.  Am I looking in the
>> wrong place?
>
> The biggest feature about Pennylane is what Phil has explained in an
> earlier message.  On Penelope the way we vary the power output is by
> scaling the magnitude of the samples going into the DAC.  This causes us
> to use less of the 16-bit sample size on the DAC, which decreases the S/N
> on the transmitter.  Instead of doing this, Pennylane has a separate
> control for power out, like Hermes, that vary's the output of the DAC
> without reducing the number of bits going into it.  This makes for a
> better S/N ratio from the transmitter.
>
>> Gordon, KA2NLM
>
> --
> Jeremy McDermond (NH6Z)
> Xenotropic Systems
> mcdermj at xenotropic.com
>
>
>
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