Saturday, April 17, 2021

Hermes-Lite 2.x

 Hermes-Lite 2.x, a 3rd Generation SDR 

In the month of Dec 2020, I was reading up on FPGA and wanted to know more about this topic. I was attracted to this YouTube https://www.youtube.com/watch?v=qlgq52IIUo8 titled Hermes-Lite: Amateur Radio SDR.



This Hermes-Lite 2.x is considered a Gen 3 SDR ( see below)



How is this different from other USB SDR dongle out there ? Here are some summary points :
  • Uses a low cost cable modem IC called AD9866 for ADC / DAC
  • No USB port , you get the SDR I/Q signals via Gigabit Ethernet / LAN
  • uses FPGA ( Field Programmer Grid Array ) to process the vast amount of I/Q signals 
  • 5W power amplifier
  • Remote control
  • Open Source

The most significant feature that caught my attention is the ability to view the entire HF spectrum from 0 to 38Mhz in ONE screen. Snapshot from video at 6:00




After watching this video, I did a quick search and found one of my supplier called makerfabs.com is currently doing a 2nd group buy for this SDR radio. https://www.makerfabs.com/hermes-lite-2.html

There are 3 parts for the order, the main hermes-lite 2 board, the N2ADR filter / relays and the enclosure with faceplates and all the necessary stuff.


I posted this "group buy" to a local ham radio fb group to get some interest check and got a few crazy ham people to join me for a group buy just before Chinese New Year 2021. As China closes for a long break during Chinese New Year festival, we need to get it shipped out before everyone closed down.

Really nice to see they recorded the video on how these boards are actually made.
https://www.makerfabs.cc/article/pcba-in-production-hermes-lite-2-0.html

After a short wait, a few units arrived. According to the instructions, we need to drill a hole and install a aluminium heatsink at the bottom.







 
Purchased this chamfer tool recently, so put it to good use. Once everything is done, install the latest PowerSDR and power it up.



How is this SDR radio different from the current SDR out there, firstly, it is connect to the software over the Local Area Network, means you can place the radio far away from noisy electrical items and do remote control.





I also loaded the HPSDR on RPI4 https://github.com/g0orx/pihpsdr with a 9.7" display that I plan to use a 7" pi display and add knobs and buttons to them like this picture below.


Here is a picture of a commercial product from ApacheLabs, Controller V2 that run PIHPSDR by John Melton.




Generations of SDR

Before we continue, let's explain about different generation of SDR radio out there, a really good youtube by Justin Giles-Clark VK7TW https://www.youtube.com/watch?v=2oKDxI09UkY . In the middle of the video, he also mentioned the Hermes board that the Hermes-Lite is based on.



Generation 1

  • Direct Conversion, HF to AF, 192kbps
  • Radios like Funcube, Flex3000, Elecraft KX3, RTL SDR
  • Relies on soundcard ADC
  • image rejection issues


Generation 2

  • ADC  ( Digital Down Converter ) / DAC ( Digital Up Converter )
  • Direct sampling
  • Need powerful PC and fat pipes
  • Radios like SunSDR
  • FlexRadio's PowerSDR made open source

Generation 3

  • Processing in the radio
  • FPGA doing the processing
  • band pass filters, attenuator
  • hugh dynamic range
  • remote operations
  • Flex 6000, ANAN-200, HPSDR, Hermes-Lite


Generation 4 

  • Gen 3 with knobs and buttons
  • Looks like an actual radio
  • Radios like SunSDR,  Flex-6700, EG-ELAD, ApacheLabs

Summary Links :-
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