Hermes Lite 2 SDR Transceiver

The Hermes-Lite is a low-cost direct down/up conversion software defined amateur radio HF transceiver based on a broadband modem chip and the Hermes SDR project. It is entirely open source and open hardware, including the tools used for design and fabrication files. Over 300 Hermes-Lite 2.0 units have been successfully built.

Late last year I received my Hermes Lite SDR 2 plus N2ADR filter board. However, the enclusure, fan and other accessories did not arrive in time for the xmas holiday.

Now, in early 2020 I’ve finally assembled this amazing little SDR transceiver. The enclosure required a little modification in order to comfortably fit the PCB, but this was a simple job once I had access to the correct tools (thanks, Tampere Hacklab!).

The completed Hermes SDR enclosure

I was initially a little nervous about the complexity of the setup (loopback audio devices, PA bias adjustment, SDR software, interfacing with hamlib etc) but amazingly everything worked on first attempt.

Rather than manually adjust the PA bias I used the simple automatic tool from James Ahlstrom (N2ADR) available here:
Note: Despite being built in Ubuntu, the binary ran perfectly under Fedora 30.

Setting up Quisk was similarly straightforward; I downloaded the latest version, installed dependencies (in my case under Fedora 30, fftw-devel and pulseaudio-devel), added a new radio and configured the band pass filters. A little time was then spent configuring radio control in both wsjtx and Quisk and I was quickly on the air.

Screenshot showing Quisk (background, bottom line showing Temperature, TX Power and SWR) and WSJTX (foreground, in QSO with G6NNS). Full resolution image can be found here:-
Screenshot showing only Quisk; a portion of the 30m band (zoomed), plus band, mode, waterfall etc.

First FT4/8 QSOs using this radio (~6W to an indoor 20m dipole) were:

G6NNS, JO02, 14.081998, FT4, Sent: +04 Rcvd: -11
GB8HNY, IO93, 14.075045, FT8, Sent: +03 Rcvd: -24
PD7RF, JO22, 14.075867, FT8, Sent: +09 Rcvd: -05
PF2JV, JO22, 14.076013, FT8, Sent: -15 Rcvd: -25

Many thanks to the above operators for (unbeknownst to them) assisting with the first on-air tests!

Testing other modes (SSB voice, FreeDV) and everything has also worked as expected. My only current issue is what appears to be a lack of a CW keyer in Quisk (or the Hermes firmware). My paddle only works as a straight key connected to the Hermes front panel.

Closer view of the Hermes Lite 2 SDR front panel

Future plans include a build based on the Hermes but with additional PA and integrated PSU. Watch this space!

Hermes Lite SDR details can be found at
To purchase via group buy, check availability via
Latest Quisk can be found at

A great introduction video by the designer, Steve Haynal KF7O can be found here:

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QRP FT8 Operating Tips

A few tips on making the most out of FT8, especially when operating QRP.

  1. Listen on odds and evens *before* selecting a TX frequency. Just because you can’t hear anyone on the receive cycle doesn’t mean you’re not colliding with other stations on TX. Once a clear space on the waterfall has been found, lock your TX frequency with the ‘Hold Tx Freq’ tick box. This is linked with the following step…
  2. Don’t call a station on their TX frequency; you’ll be just one of many doing so. Call on the slot you found in step 1 above. All stations are decoded on RX regardless of frequency. This also enables you to tail-end a QSO without colliding with the 73 messages.
  3. If the receiving station can’t hear you, repeat step 2 to find another free slot. Just because a slot is quiet for you does not mean it’s quiet at the RX station.
  4. When calling CQ periodically disable TX and instead listen on your TX slot; check a more powerful station isn’t clobbering you, and if so, repeat step 1.
FT8 Waterfall.
A waterfall plot showing TX on an adjacent free slot

Finally, be aware of signal reports. I’m running ~2W with a very inefficient antenna. Commonly my reports will be ~8dB down compared to the report I send. Assuming similar noise floor at both ends (typically around -24dB), I only have a small chance of working someone with a -16dB signal, dropping to near impossible at -18dB or below. However, if I *really* want that contact I’ll hunt around the band in the hope of finding a spot quiet on the receive side. Occasionally this works.

Enjoy the mode and I look forward to working you on the bands.

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OH3SPN FT8 Activity

I’m now active from Tampere, Finland using the call OH3SPN, primarily FT8 on 30/20/17m due to antenna restrictions; FT817 (typically 2.5W out), G4ZLP MinoProSC interface, indoor SPX-100 antenna or short wire connected to LDG Z100 Plus.

I’m very happy to report my first contacts using this call included a scheduled contact with Mark Tanner (M0MTT) and his daughter Sally Dagger (M6LHY).

Typical coverage as shown below:-

Coverage map from
Stations hearing OH3SPN, 18.01.2019 via PSKReporter

M0SPN and OH3SPN logs are available using the links above.

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As of April 2018 I’m now located in Tampere, Finland, Locator: KP11UL.  You may see my call appearing in various logs with an OH prefix whilst I’m awaiting my official Finnish callsign.

I’m currently maintaining both (M0SPN and OH/M0SPN) callsign logs on; see ‘logbook’ link above.

Initial tests on 20m using an FT817 and a 6m loop of wire, hung around an indoor window frame (using an LDG Z100+ auto ATU) can be found below.  By pure chance I seem to be throwing all my RF towards the South West.  Hello England!

The current property isn’t well suited for proper antennas so I may be limited to CW, FT8 and PSK31 for the next few months.

Steve OH/M0SPN

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Over Voltage Protection

I recently re-homed several cheap 13.8V linear PSUs from rallies, ranging from 3 to 10A. My intention is to power smaller items of equipment; TNCs, FT817s and similar. However, after inspection it became apparent that all lacked any form over over voltage protection.
I at least expected a simple crowbar circuit!

Looking at several crowbar schematics online and considering modes of failure, I thought of another option. Instead of shorting the supply on an over-voltage condition, why not simply disable output with a voltage controlled switch? If the supply voltage exceeds a safe limit (for example 14.5V) kill the output.

The problem here is how to do this without a power transistor constantly sinking current.  In the case of a 10A supply this could require a significant heatsink; Somewhat inefficient too!

So, welcome back, my old clunky friend:  the relay.


The quick schematic above (subject to revision!) is controlled by Zener D1 (in this case a 14V Zener).  When the voltage exceeds the avalanche voltage of D1 the base of Q1 starts to climb to 0.6v, becoming forward biased and hence switching on.  This in turn activates the relay, switching the main V OUT off and instead illuminating an ERROR LED.

Both the relay and error LED are both protected from over-voltage (within reason) buy a cheap 12V  regulator.

A graph showing V IN (top) plotted against the two relay outputs can be seen below.  Note the current with just the LEDs (no load) is not equal as the ‘error’ LED is held at 12V.


Click to Zoom

It is shown that the switching point is between 14.7 and 14.8V.  For a supply set at 13.8V I’m happy for this to occur anywhere up to 15V.

Dependent on the equipment connected, you should however be aware that the time taken for a relay to energise may still be enough time for damage to occur.  In many cases, a power transistor or mosfet either passing current or acting as a crowbar may be the preferable option.

Also, these are just my thoughts coupled with a quick simulation in Circuit Lab; this is untested in practice 🙂

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Hybrid (LSD) NiMH Batteries Compared

Sanyo/Panasonic Eneloop Cells

Receiving a set of NiCad batteries as a 10 year old (for use in a ‘Knight Rider’ RC car – how awesome was that?!) started a lifelong obsession with rechargeable cells.  My interest in batteries started even earlier than this, after being given random lengths of wire, torch bulbs and supposedly dead C cells to ‘play’ with.  Well, it kept me quiet 🙂

Maha/Powerex Smart Charger

Some 35 years later and I’m still doing much the same, only with NiMH cells and a Maha MH-C9000 intelligent charger/analyser.

Recently, I’ve switched to so called ‘hybrid’ or Low Self Discharge (LSD) cells as whilst the capacities are lower, I find the low self discharge rate to be more beneficial in the long term.

All cells are new and run through a charge (0.5C) and discharge (500mA) cycle, the average capacity of 4 cells recorded. Capacities are expected to marginally improve over several cycles.

Edit: Some have pointed out that I should a) be testing remaining capacity after 6 or 12 months and b) my tests are not the IEC standard.  Firstly, I’m not so interested in specific rates of self discharge (these tests are available elsewhere online).  Secondly, I find the standard IEC test (0.1C charge, 0.2C discharge, from memory) entirely unrealistic for my typical workloads such as amateur radio, DSLR, etc.  My 500mA discharge rate was chosen as a reasonable average figure for my typical use.

AA Hybrid

BrandTypeRated mAhMeasured mAh
SanyoEneloop Pro (black)24002386
SanyoEneloop (white)19001858
EnergizerACCU Recharge Extreme23002075
7 Day ShopGood To Go21502220
VartaRecharge Accu26002570

AAA Hybrid

BrandTypeRated mAhMeasured mAh
SaynoEneloop (white)750726
EnergizerACCU Recharge Extreme800742

This post will be updated as further brands/types are tested.

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Chord DM01 vs Samson Q7

I’ve been very happy with my cheap dynamic mic (a Chord DM01) and have received many complementary reports on my audio.  However, having recently been asked to co-present a podcast I needed to confirm the mic was up to the job;  high fidelity podcasts are a world away from audio squashed into 2600kHz and bounced off the ionosphere.

Chord DM07 on Desk Stand

Chord DM07

Initial tests sounded a little flat and lifeless;  nothing that couldn’t be solved with a little compression and EQ but this started me thinking about better solutions.  My previous ‘go to’ mic has always been the Shure SM58 but I was reluctant to spend the money, especially when recent reviews of other brands claimed better performance for significantly less cost.

So, meet the Samson Q7.  Great reviews almost everywhere you look.  Many users reporting better real world performance than the Sure SM58, some saying it’s now their preferred choice of mic and some even going as far as saying they’ve replaced all their mics with Q7s.

Samson Q7 and Chord DM01

Samson Q7 (top), Chord DM01 (bottom)

Fantastic! Just what I need, at at £25 delivered it seemed a bargain!

First impressions?  Flat, dull and lifeless with booming bass.  Suddenly, my Chord DM01 is sounding like a microphone costing many times the cost.  Perhaps I underestimated the Chord all along?

I tried several tests (both recorded and on the air) including varied positioning.  The Chord performed better in all tests, sounding significantly livelier.

For communications in poor conditions this extra clarity is of utmost importance but even for podcast use, I think the Chord wins hands down.

If you’re curious, I recorded a brief test and review; click the play button below.  This was recorded directly from the mics; no pop shields, EQ or compression was used.

Play Button

Click to Play

Can you recommend a better dynamic microphone?  I’m open to suggestions regardless of brand or model but would prefer to avoid condensers as my shack/studio environment is far from quiet.

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Adventures with Software Defined Radio


Some time ago I purchased an RTL ‘TV’ USB tuner. I was immediately impressed by the way whole chunks of the RF spectrum are visualised; tuning as simple as clicking a signal of interest plus ‘brick wall’ filters by the drag of the mouse. However, the novelty did soon wear off due to the lack of HF coverage.

SDR(X)When a colleague (Graham G6IXM) offered me an SDR(X) I jumped at the chance to have a play.  This interface is based on the RTL but contains an upconverter plus pre-filters, covering 0-1850MHz. Performance was really very good indeed and I had hours of fun playing with this under both GQRX and GnuRadio (Linux).  However, is still lacked something: TX.

Spurred on by the incredible performance of the SDR(X) but not wanting to get too spendy, I researched a few of the lower end SDRs available.  Whilst there’s been several recent developments, the SoftRock RXTX Ensemble seemed highly respected and has been available long enough to develop a good user base.

A few emails to Tony KB9YIG later and I had a built SoftRock RXTX crossing the pond to the UK.  I did consider a kit but seeing the complexity (and size of the SMDs) I thought better of this.  Attempting to keep costs down I purchased a cheap eBay USB soundcard (48KHz only) – figuring I can always upgrade later if I wish.  In order to re-use my existing shack mic, I also ordered a £10 XLR-USB cable (a mic cable including pre-amp and sound card).

SoftRock RXTX & USB Soundcard

The $89 SoftRock and USB Soundacrd

I decided to go with Windows first as despite being a Linux person, there seemed to be a few potential ‘gotchas’ and I was keen to play, not fight configuration issues. On initial startup (HDSDR) I noticed I could only see the LO signal.  A post to the SoftRock group later and I soon realised I’d connected the wrong SoftRock ‘out’ to the wrong soundcard connector.  Feeling a complete numpty, swapping cables made 40m spring into life.

The bands the last two days have been appalling so I’ve not had a single QSO; although sending CQ in CW on 40m did net a couple of spots on the Reverse Beacon Network (Wales and Germany).  It lives!  What a fantastic bit of kit it is, too!

reverse beacon

Spotted via the Reverse Beacon Network

SoftRock RXTX

(Click to Zoom)

The SoftRock RXTX Ensemble is available from Tony KB9YIG via in both kit ($89) and pre-built ($124) form.  The device is supplied with an external LPF which must be built before using TX. Output power is stated as 1W but using my power meter and a dummy load, I measure 3W on CW keydown (40m). Build quality is absolutely superb and I found Tony incredibly helpful.  As expected, I had VAT and a handling fee to pay before collection in the UK but this IMO is still tremendous value.


HDSDR (Windows)

When band conditions improve I can see the SoftRock RXTX Ensemble rapidly becoming my radio of choice.  Whilst I love my FT847, this has opened my eyes to a whole new way of operating.  I fear there’s no way back.  I’m addicted.

Huge thanks to Tony KB9YIG for making this not only possible, but affordable.

Steve M0SPN

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Multi Band Slinky Doublet

Designing an HF antenna for Swindon Makerspace presented several challenges:-

  1. Routing coax from Makerspace to the roof is potentially tricky
  2. High external vertical antennas would require lightning protection
  3. No convenient external earths available
  4. Counterpoises impractical due to size
  5. Large horizontal antennas (long wire, dipole) would probably not be appreciated by the property owners.


Initial WSPR Results

These issues ruled out my ‘go-to’ antennas; fan dipoles and verticals.  Not sure how to proceed, I visited the Makerspace armed with an FT817, a short loaded 40m vertical, some random lengths of wire and an LDG auto ATU.

Running WSPR (~2W) resulted in many spots on several bands all around Europe. This gave me hope 🙂

The Makerspace is approximately 10 metre square, with a sloping roof.  I considered folded dipoles and loops but both have their limitations (single band antenna or very high Q).  A doublet seemed a potential solution but the highest path in the roof space is only 10m long, too short for anything below 20m (14MHz).

The Raw Ingredients


I’d previously read several articles (eHam, RadCom) regarding the use of Slinkys as antennas. Further research showed a single slinky can stretch to ~5m in length and contains ~20m of coiled wire. To make this a multiband antenna I figured I could feed with twin-feed (aka ladder line) connected to a balanced ATU.


The Finished Slinky Antenna


Say hello to the Makerspace Slinkyantenna!

Supported with nylon rope and with slinky’s extended to almost touch the walls.  It’s a compromise on several levels but initial tests (FT817, LDG ATU, DIY balun) suggest it’s usable on most bands >= 40m (7MHz).  Initial frustrations when Gergana LZ1ZYL (Bulgaria) couldn’t hear us were later explained when the other stations calling mentioned the power they were using.  When our ~2W QRP signal was finally heard, an S8 report was received and details exchanged without issue (she was S9+10, running significantly more power).

Test Station Showing First Contact QRZ


We plan to kit out the space with a balanced manual ATU and a 100W transceiver.  The station will be available for use by licensed members on a 24×7 basis.

Our long term aim is to recruit other full license holders and ultimately request a dedicated Swindon MakerSpace club callsign.

Interested in joining the Makerspace?  Have a solid state HF radio you may be willing to part with? Please get in touch :o)


 What is Swindon Makerspace?


Makerspace Wall Logo

Swindon Makerspace; a not-for-profit registered C.I.C. (Community Interest Company). We like to break and make things.  Many different things – robots, aircraft, computers, electronics – anything goes.

For more information see Swindon Makerspace.

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Introduction to Packet (ax.25)

When starting out with packet I found it difficult to find my way.  Several resources exist online but all seem to assume some basic level of understanding, which I clearly lacked.  I have to admit here, I’m still new to the mode myself so my please forgive any errors.  This article could also be titled “packet walk-through” or “the packet guide I wish I had when starting out”!

My AEX PK-88 before restoration

My AEX PK-88 before restoration

Firstly, I’m running a PK-88 TNC (radio modem) configured for KISS mode operation. This means the TNC is acting as a dumb modem; it’s using the native ax.25 support within Linux.  If you’re new to packet, I’d suggest using your TNC in the normal interactive mode. The only difference is the initial setup/connection:-


Initial configuration in KISS mode (Linux)

The above image shows association of the KISS TNC with a serial port, output of ‘ifconfig’ listing the status of the interface and a request for Linux to ‘axcall’ my local node, GB7BA. GB7BA is located in Bampton, Oxfordshire and is accessible from Swindon on 2m (144.950MHz) and 70cm (432.675).

NOTE: If not using KISS mode, you’d connect to your TNC via a communication package (typically Minicom in Linux or Hyperterm/Putty under Windows) then issue a ‘c gb7ba’ from within the interactive TNC session.  From this point onwards all steps are identical regardless of connection mode.


Initial connection to GB7BA

We’re connected to GB7BA!  The data continues to arrive and some handy shortcuts for connection to popular nodes are listed.  At this point you can simply type ‘help’ or ‘/h’ for basic help.  Commands typed typically appear in the bottom part of the window, responses from the remote station appear in the larger section above.

I issue an ‘n’ command to list attached nodes, followed by a ‘c lvchat’ to connect to a chat node (which was previously listed under the nodes returned).  Chat nodes are typically all connected (BPQ Chat?) so the exact node is not important here, although a local node would be better.


Connection to LVCHAT

Looking good!  Another user says hi, so I respond :-


LVCHAT Discussion

Unsure what commands are available?  ‘/H’ is often a safe bet for help:-


Chat Help

After this, I type ‘/QUIT’ or ‘/B’ to disconnect.  I then reconnect to GB7BA but this time issue the command ‘c cowbbs’ to connect to my home BBS.  COWBBS (actually GB7COW) is located in Devon, England – the county where I grew up, hence me choosing this as my home BBS.  Your ‘home’ is where packet emails addressed to you are delivered.



I’m connected! My password has been removed from the above screenshot. Now, let’s check if I have any emails.  ‘lm’ is List Mine:-


Checking for Messages at GB7COW

No new messages. Well, this is a BBS (Bulletin Board) so let’s check for the latest 5 bulletins aka broadcast messages.  I type ‘ll 5’ (list latest 5):-


Checking for Bulletins at GB7COW

An interesting list of TECH, HUMOUR and SWPC (Solar?) bulletins.  If interested, I’d issue an ‘r <article number>’ to read one of the above.  If I typed just ‘ll’ it would list all and likely take forever. In this case simply issuing ‘a’ will usually abort the listing. If unsure of commands, ‘/h’ or ‘help’ will return useful information:-


Help on command syntax at GB7COW

For now, I’ll disconnect and show one more commonly used tool, the DX Cluster.  From my local node GB7BA I issue the command ‘c 8 dx’ (for some reason just ‘c dx’ failed – I had to specify the port (8 refers to IP – help was provided when the first command failed):-


Connected to a DX Cluster (GB7RDX)

The above shows the connection to ‘dx’ (actually an alias for GB7RDX) and the DX spots slowly flowing in.

One resource I did find particularly useful was Larry WB9LOZ’s Introduction to Packet, in particular the ‘TNC Commands’ (for those not using KISS mode) and ‘BBS Commands’ for a more thorough walk-through of  the BBS basics.  Just be aware that some of the commands he mentions may not be valid on certain BBSs.

Also, whilst I’ve used ‘axcall’ under Linux (or suggested new users use an interactive session on their TNC) there are software packages available which offer more functionality. Winpack (Windows), Linpack (Linux) and AmiCom (AmigaOS) all offer extended functionality, multiple sessions etc.  However, in the case of Linpack (Winpack clone) I found the interface a steep learning curve in itself; I assume Winpack is similar. If you’re looking for a fully functional and easy to use client (and have an Amiga; if not why not?), I can highly recommend AmiCom by Gerhard Loder DL3MGQ.

Much of the above may seem simple but as a new user I found it totally baffling.  If I’ve misunderstood or otherwise made errors please feel free to leave a comment either here or via my packet mailbox:  M0SPN@GB7COW.#44.gbr.euro.


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