[hpsdr] New Hermes 2M Board.

[dan edwards]

from the 'peanut gallery'...
TWO ADC's would certainly tweak my interests...
diversity, beam forming, etc, in the suburbs..
just sayin...
73, w5xz, dan


      From: Kjell Karlsen <la2ni at online.no>
 To: "hpsdr at lists.openhpsdr.org" <hpsdr at lists.openhpsdr.org> 
 Sent: Sunday, May 28, 2017 2:33 PM
 Subject: [hpsdr] New Hermes 2M Board.
   
***** High Performance Software Defined Radio Discussion List *****

Hi All.

As Apache Labs has decided to stop the production of the Hermes board, we
have discussed to see if it is possible to get it produced by others.

I have for a long time thought of the possibility to improve the
construction and include some long wanted features. I am going to describe
the modifications I am thinking on. And of course we are open for other
ideas!

We have got all the original layout files for Hermes from Abhi and that is
a good starting point.

Endre Kiss, YO6OGJ is going to do the layout job. The first he is going to
do is to draw completely new schematics in Altium Designer. The physical
layout of the new board will follow the original as near as possible to be
sure that the good performance of Hermes is kept or even improved.

The preliminary list of modifications follows:

1: New PA giving 5W PEP output. By increasing the power output it can be
used to drive a LDMOS PA directly to >1KW output. I have tested 2 of the
newest 14V LDMOS transistors from NXP (Freescale) and they can give >5W
linear output, also on 50 MHz. With Pure Signal, the IM3 is >70 dBc at 5W.
Even at 145 MHz, the power out is >1W with good linearity.

2: After a suggestion by Leif Aasbrink, SM5BSZ the DAC is going to give  
full
output all the time and the drive regulation to the PA is done by using a
step attenuator after the first low noise amplifier. This will keep the
phase noise as low as possible in the TX signal. The same solution is going
to be used in Metis.

3:Use the newest SMPSU chips for the power supply. The latest chips are
much more "silent" than the old and it is easier to suppress the spurs. By
using one for the 5V bus and one for 3,3V and run synchronously, we need
only 2 or 3 linear regulators in addition for the most critical systems so
the total power consumption can be reduced. It might also be possible to
use only one switcher delivering 3,3V. There are only a few circuits that
use 5V so just a small linear regulator is needed.

4: Remove the ON/OFF switch from the board. In most systems the switch is
on another board or installed on the front separately. And we can use the
space for other parts.

5. Add 2 meter operation on Hermes 2M by using under sampling. By  
installing
  the 145 MHz BP filters on the bottom side of the board, the switching
 from HF to VHF should not introduce any extra spurs.
Including 70 MHz has been asked for but the restricted space forbids this.
And the chances to get extra spurs would increase.
As the new PA can give >1W even on 145 MHz, also TX is included.

6 New FPGA. Phil, VK6PH is looking for a more modern FPGA to replace the
Cyclone III that is used today.

7: There is a need for some more I/O´s. For ex. control output for use
with EER-PWM Power Amplifiers, interface to control an external ATU
(compatible with ICOM ATU)and so on.

We are open for other ideas so please give feedback.

The decision to start a production will be taken after the schematics are
completed and the cost is calculated.

A few prototype boards has to be produced and tested and eventually  
modified.

When the construction is tested and found OK, we can make a list and
produce fully populated and tested boards. Also bare boards will be
offered for the brave ones.

We also plan to make prototypes of a new Apollo board with 30W PEP out,  
also
on 50 MHz and offer ready made boards without the inductors installed.

At the moment there are no plans to make complete transceivers. But  
combining
Hermes 2M with Apollo and the PiHPSDR controller, a complete transceiver  
like
the one I showed at Friedrichshafen last summer is possible.

We hope there are enough people that are interested in this. When I read
the reflectors, my impression is that there still are a lot of people
interesting in building their own equipment.

73, Kjell


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