Taking the Hiss out of QO-100

I’ve been on the QO-100 satellite for about 7 months now and I have to admit I love it!

Having a “Repeater In The Sky” that covers a third of the world really is a wonderful facility to have access to however, there is one thing that I find tiring and that is the high level of background noise that is always present.

Even though the signals are mostly 59-59+15dB the background “hiss” is very pronounced and gets very tiring after a while, especially if like me you have tinnitus.

Currently I’m using a NooElec Smart SDR for the receiver and GQRX SDR software on my Kubuntu Linux PC. This works great but, there is one short fall, there is no DSP Noise Reduction (NR) in the software or hardware.

To fix this I recently invested in a BHI Dual In-Line Noise Eliminating Module. The unit itself is nicely put together and has a good combination of inputs and outputs making it easy to connect up to my MacBook Pro to record QSOs and connect my headphones at the same time.

M0AWS BHI Dual In-Line Noise Eliminating Module
M0AWS BHI Dual In-Line Noise Eliminating Module

At £189.95 plus postage from BHI direct it’s not cheap but, it is nicely put together and comes complete with a power lead and a couple of cheap audio cables. The quality of the knobs and mechanisms is good apart from the little grey DSP Filter Level knob that feels cheap and is very wobbly on the switch below. I’m not sure how long this is going to last with prolonged use and will most likely need replacing with something a little sturdier at some point in the future.

Overall noise reduction is good but, the audio amplifiers on the Audio Input Level and Line Out Level distort very early on in their range and you cannot get them much above level 5 before distortion starts to appear on the received signal. This is disappointing as my headphones are of reasonable quality and are let down by the distortion creeping in from the audio amplifier in the BHI unit.

I’ve tried altering the levels on the input from the IC-705 and no matter what I cannot get a good audio signal in my headphones without some distortion on the higher frequency ranges.

Overall the device does do what I want, it reduces the background “hash” considerably reducing the fatigue whilst chatting on the satellite. Below is a recording from a conversation on the satellite showing the noise reduction performance of the BHI module.

M0AWS Example BHI DSP NR Recording

The recording starts with the BHI DSP NR off, at 00:07 the DSP NR is switched on, you can clearly hear the difference. At 00:23 the DSP NR is turned off again and at 00:36 the DSP NR is turned on again. The BHI DSP NR Module is set with the DSP Filter Level set at 3 out of 8 which appears to be the best level to use. Switching to level 4 starts to introduce digital artefacts to the audio which only gets worse the higher the DSP Filter Level goes.

With a setting above level 3 there really isn’t much improvement in noise reduction and the audio becomes progressively more affected by the digital artefacts than it does from the background noise.

M0AWS BHI Dual In-Line Noise Eliminating Module with Icom IC-705 QO-100 Ground Station
M0AWS BHI Dual In-Line Noise Eliminating Module with Icom IC-705 QO-100 Ground Station

The only other problem I have with the BHI Dual In-Line Noise Eliminating Module is that is comes in a plastic case. The case itself is solid and of good quality however, it offers no RF shielding whatsoever and the unit is extremely susceptible to RF getting into the audio chain and then being heard during transmit in the headphones and via the line out connections. For the money I would had expected the unit to come in a metal case that provides proper RF shielding. This is a real shame as it lets the unit down considerably.

As setup in the photo above I am using 300mW O/P on 144Mhz from the IC-705 into a perfect 1:1 SWR presented by the DX Patrol 2.4Ghz Upconverter via some very high quality LMR-400 Coaxial cable from Barenco but, I get terrible RF interference via the BHI unit during the transmit cycle. Considering I am only using 300mW I dread to think what it may be like if I was using a 100w HF radio. This is something I need to investigate further as it really is very annoying.

Moving the unit to a different location in the radio room does help a bit but, doesn’t solve the problem completely. At 300mW RF O/P I really didn’t expect there to be a problem with RF getting into the BHI unit.

Having a proper line-out facility on the BHI unit really is nice as it makes it very easy to connect to my MacBook Pro to obtain good quality recordings of signals on the QO-100 satellite as can be listened to above.

Overall I am happy with the BHI Dual In-Line Noise Eliminating Module but, do wish that more care had been taken over using a metal case instead of a plastic case to protect the unit from RF ingress and better audio amplifiers within the unit that don’t distort/clip so early on in their O/P levels.

Is this the perfect noise reduction unit?

No but, overall it is better than nothing and does help to reduce the background noise to a more acceptable level reducing the overall fatigue during prolonged conversations on the QO-100 satellite.

UPDATE: I tried the BHI unit with my FTDX10 on the HF bands and the RF interference is horrendous, even when using QRP power levels! This device clearly hasn’t been designed to work in an RF environment and the total lack of shielding or isolation lets it down terribly. If you are an SWL then this unit is fine but, if like me you like to monitor your transmitted audio whilst on air through headphones then this isn’t the unit for you. To prove the problem isn’t in the radio shack I put the BHI unit in the house some 30m away powered by 12v battery with nothing connected but a pair of headphones and still the unit suffered from RF interference even at QRP levels.

More soon …

Home-Brew 12v DC Distribution Box

I’ve been wanting to tidy up the cabling to the 12v DC PSU for some time in the radio shack as like many HAMs I have a number of radios/devices that all need a 12v feed but, only two connectors on the front of the PSU. The net result was a birds nest of wires all connected to the PSU making it impossible to disconnect one device without others getting disconnected at the same time.

Looking online I found that many of the HAM outlets stores sell nice little 12v DC distribution boxes that would be ideal however, they’re all priced somewhat high for what they are so, I decided to purchase the parts and make one myself.

Searching on Amazon I found all the necessary parts for less than a quarter of the cost of commercially made units. A couple of days later the parts arrived and sat on my desk in the shack for a few weeks. Yesterday I finally found the time to make a start on the project.

M0AWS home-brew 12v DC Distribution Box
M0AWS home-brew 12v DC Distribution Box

After much drilling and filing I had the necessary holes/slots cut in the plastic box for the 4mm connectors and fuse holders and started wiring them up. Part way through my 30 year old soldering iron decided to die and so I had to stop and wait for a replacement to arrive.

M0AWS completed 12v DC Distribution Box
M0AWS completed 12v DC Distribution Box

With the new soldering iron in hand it only took 30mins or so to complete all the joints and I soon had the box together ready to test with my multimeter to ensure I didn’t have any shorts or crossed wires.

With testing complete and fuses in place I connected it up to the PSU and then connected all the devices one by one checking for voltage drops as I went.

M0AWS 12v DC Distribution Box
M0AWS 12v DC Distribution Box

I now have my CG3000 remote auto ATU, GPSDO, QO-100 ground station and IC-705 all nicely connected in a much tidier fashion than before, all for considerably less than the commercially available alternatives.

More soon …

Antenna Analysers – The New World

Many years ago I had an MFJ-259B antenna analyser that I used for all my HF antenna projects. It was a simple device with a couple of knobs, an LCD display and a meter but, it provided a great insight into the resonance of an antenna.

MFJ-259B Antenna Analyser
MFJ-259B Antenna Analyser

Today things have progressed somewhat and we now live in a world of Vector Network Analysers that not only display SWR but, can display a whole host of other information too.

Being an avid antenna builder I’ve wanted to buy an antenna analyser for some time but, now that I’m into the world of QO-100 satellite operations using frequencies at the dizzy heights of 2.4GHz I needed something more modern.

If you search online there are a multitude of Vector Network Analysers (VNAs) available from around the £50.00 mark right up to £1500 or more. Many of the VNAs you see on the likes of Amazon and Ebay come out of China and reading the reviews they aren’t particularly reliable or accurate.

After much research I settled on the JNCRadio VNA 3G, it gets really good reviews and is very sensibly priced. Putting a call into Gary at Martin Lynch and Sons (MLANDS) we had a long chat about various VNAs, the pros and cons of each model and the pricing structure. It was tempting to spend much more on a far more capable device however, my sensible head kicked in and decided many of the additional features on the more expensive models would never get used and so I went back to my original choice.

Gary and I also had a long chat about building a QO-100 ground station, using NodeRed to control it and how to align the dish antenna. The guys at MLANDS will soon have a satellite ground station on air and I look forward to talking to them on the QO-100 transponder.

Getting back to antenna analysers, I purchased the JNCRadio VNA 3G from MLANDS at £199.96 + postage and have been trying it out on a couple of antennas here at the M0AWS QTH.

Initially I wanted to check the SWR of my QO-100 2.4GHz IceCone Helix antenna on my satellite ground station to ensure it was resonant at the right frequency. Hooking the VNA up to the antenna feed was simple enough using one of the cables provided with the unit and I set about configuring the start and stop stimulus frequencies (2.4GHz to 2.450GHz) for the sweep to plot the curve.

The resulting SWR curve showed that the antenna was indeed resonant at 2.4GHz with an SWR of 1.16:1. The only issue I had was that in the bright sunshine it was hard to see the display and impossible to get a photo. Setting the screen on the brightest setting didn’t improve things much either so this is something to keep in mind if you plan on using the device outside in sunny climates.

(My understanding is that the Rig Expert AA-3000 Zoom is much easier to see outside on a sunny day however, it will cost you almost £1200 for the privilege.)

A couple of days later I decided to check the SWR of my 20m band EFHW vertical antenna. I’ve known for some time that this antenna has a point of resonance below 14MHz but, the SWR was still low enough at the bottom of the 20m band to make it useable.

Hooking up the VNA I could see immediately that the point of resonance was at 13.650Mhz, well low of the 20m band and so I set about shortening the wire until the point of resonance moved up into the band.

JNCRadio VNA3G showing 20m Band EFHW Resonance
JNCRadio VNA3G showing 20m Band EFHW Resonance

With a little folding back of wire I soon had the point of resonance nicely into the 20m band with a 1.35:1 SWR at 14.208Mhz. This provides a very useable SWR across the whole band but, I decided I’d prefer the point of resonance to be slightly lower as I tend to use the antenna mainly on the CW & FT4/8 part of the band with my Icom IC-705 QRP rig.

Popping out into the garden once more I lengthened the wire easily enough by reducing the fold back and brought the point of resonance down to 14.095Mhz.

JNCRadio VNA3G showing 20m Band EFHW Resonance 14Mhz to 14.35Mhz Sweep
JNCRadio VNA3G showing 20m Band EFHW Resonance 14Mhz to 14.35Mhz Sweep

The VNA automatically updated the display realtime to show the new point of resonance on the 4.3in colour screen. I also altered the granularity of the SWR reading on the Y axis to show a more detailed view of the curve and reduced the frequency range on the X axis so that it showed a 14Mhz to 14.35Mhz sweep. With an SWR of 1.34:1 at 14.095Mhz and a 50 Ohm impedance, the antenna is perfectly resonant where I want it.

It’s interesting to note that the antenna is actually useable between 13.5Mhz and 14.5Mhz with a reasonable SWR across the entire frequency spread. Setting 3 markers on the SWR curve I could see at a glance the SWR reading at 14Mhz (Marker 2) , 14.350Mhz (Marker 3) and the minimum SWR reading at 14.095Mhz (Marker 1).

I’ve yet to delve into the other functionality of the VNA but, I’m very happy with my initial experience with the device.

More soon …

Just one little rain drop is all it takes!

We’ve not had rain for over 6 weeks here in Eyke, Suffolk. The ground is incredibly dry and dusty. The farmers have been pulling vast quantities of water from their bore holes for weeks to keep the crops alive and we’ve been putting extra water out for the birds and animals that visit our garden daily.

Then one night we had about 30mins of light rain, not much at all and it was consumed by the dry earth is seconds. By morning you’d never of known it had rained however, strangely the next day when I fired up my QO-100 ground station I noticed that my signal into the satellite was way down from it’s normal S9+10dB level. Checking drive into the up-converter and SWR at the IC-705 everything looked fine. I then decided to check the SWR from the 2.4Ghz amplifier output only to find that it was off the scale.

I checked inside the enclosure for water ingress but, all was bone dry as normal. I disconnected the coax cable from the output of the amplifier and the IceCone Helix uplink antenna, tested with a multimeter and found everything was fine, no short and perfect continuity.

After scratching my head for a few minutes I decided to take both the N Type and SMA connectors apart to look for water ingress. Since the inside of the enclosure was dry I wasn’t expecting to find anything.

The N connector at the Helix antenna end on the dish LNB mount was perfectly dry, no water ingress at all. The layers of self amalgamating tape I’d put over the connector had done its job perfectly. Shame I had cut the tape off to remove the plug!

Upon removing the SMA connector at the amplifier end of the coax I noticed a tiny drop of water in the bottom of the housing where the pin goes through the white plastic insulator, not a good sign.

Sure enough upon further inspection I found that the white plastic disc that is situated above the pin on the centre conductor was wet and the coax braid felt damp. I knew immediately this wasn’t good.

At first I didn’t understand how there could possibly be water in the SMA connector when the rest of the enclosure was dry. Where the coax goes into the top of the enclosure there is a water tight junction that tightly grips the coax cable and seals it, supposedly stopping water ingress.

Since there was water in the SMA connector I feared that perhaps the water had gone further and entered into the amplifier so, I decided to remove the amp from the enclosure and remove the top cover to check.

2.4Ghz amplifier with top cover removed
2.4Ghz amplifier with top cover removed

After some close inspection I found the amp to be perfectly dry and free from water ingress, a relief for sure.

Before putting it all back together I decided solder on a pair of wires to the SWR and FWD-PWR pins on the amplifier and run them down into the radio room. This would then allow me to check the SWR and power output without having to get up to the enclosure with a multimeter.

Once this was done I then set about cutting 5cm of LMR-400-UF off at the SMA connector end so that I had a fully dry piece of coax cable to refit the SMA connector to. Having to do this outside and up a ladder wasn’t the easiest but, with a little perseverance and cooperation from the breeze I managed to get the pin soldered back onto the end of the coax and the connector back together.

I reconnected the amp to the 28v feed so that I could check the SWR and power output at full rating instead of the lower 12v setting that I had been using. Checking the voltage on the SWR pin I found that it fluctuated between 0.2v and 0.44v. This wasn’t what I was expecting as the PDF manual for the amplifier states that with a 1:1 SWR you should see 1.5v on the SWR pin.

DXPatrol 2.4Ghz Amplifier Manual Page for SWR/FWD-PWR voltages
DXPatrol 2.4Ghz Amplifier Manual Page for SWR/FWD-PWR voltages

After checking all the connections and retesting and getting the same voltage reading I emailed Antonio at DXPatrol detailing my findings and asking if he could advise on the voltages I was seeing. Sure enough in no time at all he came back to me saying that the manual was incorrect and that I should see between 0.2 and 0.5v on the SWR pin for a good SWR match. Being happy that the readings I was getting were fine I emailed back thanking him for his swift reply and then moved on to check the power output safely in the knowledge that the SWR reading was within tolerances.

Checking the FWD-PWR pin I found that on SSB the voltage was fluctuating between 2v and 3v, this equates to 6w and 9w output, about right for SSB. Switching to CW mode I found the full 4v was present on the FWD-PWR pin confirming I had the full 12w output from the amp. Of course this set off “Leila” on the satellite immediately as I was a huge signal on the bird with such high power output and was a reminder to reconnect the amp to the 12v supply instead to ensure I didn’t exceed 5w output and thus keeping to a considerate level on the transponder input.

After further investigation I came to the conclusion that the water ingress could only of come from the cable inlet on the top of the enclosure, it had then run down the coax cable into the SMA connector. Somewhat annoying as the inlet is supposed to be a water tight fixing. Once I had everything back in the enclosure and securely fitted, I covered the cable inlet and coax in self amalgamating tape in the hope that this would stop any further water ingress. I also re-taped the N connector at the antenna end as well to ensure it was also protected from water ingress in the future.

2.4Ghz ground station enclosure ready for testing
2.4Ghz ground station enclosure ready for testing

I’m hoping this will be the end of my water ingress issues and that I have a dry 2.4ghz future ahead of me.

More soon …

QO-100 Satellite Update

I’ve been active on QO-100 for a few days now and I have to admit that I’m really pleased with the way the ground station is performing. I’m getting a good strong, quality signal into the satellite along with excellent audio reports from my Icom IC-705 and the standard fist mic.

I’m very pleased with the performance of the NooElec v5 SDR receiver that I’m now using in place of the Funcube Dongle Pro+ SDR receiver. Being able to see the entire bandwidth of the satellite transponder on the waterfall in the GQRX SDR software is a huge plus too.

M0AWS QO-100 Satellite Log map showing contacts as of 23/06/23
M0AWS QO-100 Satellite Log map showing contacts as of 23/06/23

As can be seen on the map of contacts above, I’ve worked some interesting stations on some of the small islands in the Atlantic and Indian Oceans. The signals from these stations are incredibly strong on the satellite and an easy armchair copy.

DX of note are ZD7GWM on St. Helena Island in the South Atlantic Ocean, PP2RON and PY2WDX in Brazil, 8Q7QC on Naifaru Island in the Maldives, VU2DPN in Chennai India, 5H3SE/P in Tanzania Africa and 3B8BBI/P in Mauritius.

There are many EU stations on the satellite too and quite a few regular nets of German and French stations. I’ve not plucked up the courage to call into the nets yet, perhaps in the future.

There are a lot of very experienced satellite operators on QO-100 with a wealth of information to share. I’ve learnt a lot just from chatting with people with some conversations lasting well over 30mins, a rarity on the HAM bands today.

We also had our first Matrix QO-100 Net this week, an enjoyable hour of chat about all things radio and more. We have a growing community of Amateur Radio enthusiasts from around the world on the Matrix Chat Network with a broad spectrum of interests. If you fancy joining a dynamic community of radio enthusiasts then just click the link to download a chat client and join group.

More soon …

My First QO-100 Satellite QSO

I’ve been waiting for over a week so far for a male to male SMA connector to arrive from Amazon so that I can connect the 2.4Ghz up-converter to the 2.4Ghz amplifier. Since it still hasn’t arrived I decided to connect the up-converter directly to the IceCone Helix antenna to see if I could get a signal into the QO-100 satellite.

To my surprise I could easily hear my CW signal on QO-100 even though the total output from the up-converter is only 200mW.

I didn’t expect to be able to hear my signal since it’s a tiny amount of power that has to travel some 22500 miles to the satellite but, I could hear it and was amazed that it was peaking S8 on my SDR receiver.

2.4Ghz Up-COnverter connected directly to the antenna bypassing the 2.4Ghz Amplifier
2.4Ghz Up-Converter connected directly to the antenna bypassing the 2.4Ghz Amplifier

Being excited I put out a CQ call that was soon answered by OH5LK, Jussi in Finland. Jussi gave me a 579 report which I was extremely pleased with. He was of course much stronger at a 599+ at my end. We had a quick QSO and exchanged details without any problems at all. Its really nice to get a QRPp contact without any QSB or QRM.

M0AWS QO-100 1.1m off-set Dish and IceCone Helix antenna ground station
M0AWS QO-100 1.1m off-set Dish and IceCone Helix antenna ground station

Neil, G7UFO who I chat with regularly in the Matrix Amateur Radio Satellites room has posted a connector out to me so I’m hoping it will arrive on Monday and then I’ll be able to connect the amplifier and hopefully get a few SSB contacts.

UPDATE: I’ve since had 2 SSB contacts via QO-100 using just the 200mW O/P from the up-converter. Both times I got a 3/3 report not brilliant but, perfectly acceptable for the amount of power I’m putting out.

More soon …

UPDATE: QO-100 Node Red Dashboard

I’ve been making a few improvements to my QO-100 Node Red Dashboard whilst waiting for the 2.4Ghz hardware to arrive. I’ve added the ability to split the RX and TX VFOs so that I can tune away from the TX frequency for working split stations or for tuning to slightly off frequency stations. I also added a series of tuning buttons to the top of the GQRX side of the dashboard to enable easy tuning using the trackball connected to my Kubuntu PC. This worked well but, I really missed having a real VFO knob like a conventional radio.

As I had a Griffin Powewrmate USB VFO from a previous SDR radio I added it to the flow as well so that I had a physical VFO knob for the SDR receiver. Details on how I got it working using evtest and a simple BASH script are in the Griffin Powermate article.

M0AWS QO-100 Node Red Dashboard Flow
M0AWS QO-100 Node Red Dashboard Flow

The Node Red flow is looking a little busier with the addition of split mode and the Griffin Powermate USB VFO which has really enhanced the useability of the solution. It’s very impressive what can be achieved with Node Red with a little imagination. You really don’t need to be a heavy weight programmer to make things work.

M0AWS QO-100 Node Red Dashboard as of 07/06/23
M0AWS QO-100 Node Red Dashboard as of 07/06/23

I also put together some code to calculate the S Meter reading from the dBFS data the GQRX SDR software generates. It’s not 100% accurate but, it’s close enough to be useful.

On the IC-705 side of the Dashboard I also now display the 2.4Ghz uplink frequency so that it’s available for logging.

So with the QO-100 Dashboard ready to go live I have now started putting together the 2.4Ghz transmit path of the ground station. I have the 2.4Ghz transverter and matching 12w amplifier from DXPatrol, the IceCone Helix 2.4Ghz antenna from Nolle Engineering, some LMR-400-UF and connectors from Barenco and an appropriate water proof enclosure from Screwfix to fit all the kit into however, I’m now being held up by one simple little SMA male to SMA male connector that I need to connect the transverter and amp together.

The SMA connector has been ordered but, is taking a month of Sundays to arrive! Hopefully it’ll arrive soon and I’ll finally get on the QO-100 satellite and start enjoying the fun.

More soon …

Use a Griffin Powermate with SDR via Node Red

I’ve been gradually building my QO-100 ground station over the last few months and have had the receive path working for some time now. One of the things I really miss with the Funcube Dongle Pro+ (FCD) SDR is a real VFO knob for changing frequency.

My QO-100 Node Red dashboard is configured so that I can have the FCD track the uplink frequency from the IC-705 but, sometimes I use the FCD without the IC-705 in the shack and so a physical VFO would be handy.

Many years ago when I lived in France (F5VKM) I had a Flexradio Flex-3000 SDR, a great radio in it’s time and one that gave me many hours of enjoyment. One addition I bought for that station was a Griffin Technology Powermate VFO knob. It worked extremely well with the PowerSDR software for the Flex-3000 and I used it for many years.

Many years later I’m back in the UK and much of my equipment is packed away in the attic, including the Griffin Technology Powermate VFO.

I decided to dig it out and see if I could get it working with GQRX SDR software. Sadly I couldn’t get it working with GQRX however, I did find a way of getting it working with Node Red and thus could add it to my QO-100 Node Red Dashboard and then control GQRX with it via a simple Node Red flow.

Griffin Technology Powermate VFO
Griffin Technology Powermate VFO

Plugging the Powermate VFO into my Kubuntu PC it wasn’t immediately recognised by the Linux O/S. After a little searching I found the driver on Github. I added the PPA to my aptitude sources and installed the driver using apt.


Once installed the default config for the Powermate device is to control the default audio device volume. To make the device available for use as a VFO knob you need to change the configuration so that the default setting is disabled. To do this is relatively easy, just edit the config file using your favourite command line editor (Vi/Vim in my case) and add the following entry.

vi /etc/powermate.toml

# Entry to control HDMI volume with Powermate
#sink_name = "alsa_output.pci-0000_01_00.1.hdmi-stereo"

# Set powermate not to work with volume control
sink_name = ""

As shown above, comment out the default “sink_name” entry (Yours may be different depending on audio device in your PC) and add in the Powermate “sink_name” entry that effectively assigns it to nothing.

Once this is done, save the file and exit your editor and then reboot the PC.

Next you’ll need to install a small program called evtest.

sudo apt install evtest

To check the evtest program has installed correctly, plugin your Powermate VFO to any available USB port and run the following command in a terminal.

evtest /dev/input/powermate

Turning the Powermate knob you should see output on the screen showing the input from the device. You should also see BTN events for each press of the Powermate device.

Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x77d product 0x410 version 0x400
Input device name: "Griffin PowerMate"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 256 (BTN_0)
  Event type 2 (EV_REL)
    Event code 7 (REL_DIAL)
  Event type 4 (EV_MSC)
    Event code 1 (MSC_PULSELED)
Testing ... (interrupt to exit)
Event: time 1685816662.086666, type 2 (EV_REL), code 7 (REL_DIAL), value -1
Event: time 1685816662.086666, -------------- SYN_REPORT ------------
Event: time 1685816662.318638, type 2 (EV_REL), code 7 (REL_DIAL), value -1
Event: time 1685816662.318638, -------------- SYN_REPORT ------------
Event: time 1685816662.574615, type 2 (EV_REL), code 7 (REL_DIAL), value -1
Event: time 1685816662.574615, -------------- SYN_REPORT ------------
Event: time 1685816663.670461, type 2 (EV_REL), code 7 (REL_DIAL), value 1
Event: time 1685816663.670461, -------------- SYN_REPORT ------------
Event: time 1685816664.030421, type 2 (EV_REL), code 7 (REL_DIAL), value 1
Event: time 1685816664.030421, -------------- SYN_REPORT ------------
Event: time 1685816664.334389, type 2 (EV_REL), code 7 (REL_DIAL), value 1
Event: time 1685816664.334389, -------------- SYN_REPORT ------------
Event: time 1685816665.334255, type 1 (EV_KEY), code 256 (BTN_0), value 1
Event: time 1685816665.334255, -------------- SYN_REPORT ------------
Event: time 1685816665.558230, type 1 (EV_KEY), code 256 (BTN_0), value 0
Event: time 1685816665.558230, -------------- SYN_REPORT ------------
Event: time 1685816666.030161, type 1 (EV_KEY), code 256 (BTN_0), value 1
Event: time 1685816666.030161, -------------- SYN_REPORT ------------
Event: time 1685816666.182151, type 1 (EV_KEY), code 256 (BTN_0), value 0
Event: time 1685816666.182151, -------------- SYN_REPORT ------------

At this point you’re ready to stop evtest (CTRL-C) and then create the following little BASH shell script that Node Red will run to collect the O/P from the Powermate USB device.


# Griffin Technology Powermate control script #
# for Node Red.                               #
#                                             #
# 04/06/23 - M0AWS - v0.1                     #
#                                             #

echo "STEP-1Hz"

/usr/bin/evtest /dev/input/powermate | while read LINE 
   case $LINE in

      *"(REL_DIAL), value 1") echo "$VAL"

      *"(REL_DIAL), value -1") echo "-$VAL"

      *"(BTN_0), value 1") case $VAL in

                              "1") VAL="10"
                                   echo "STEP-10Hz"

                             "10") VAL="100"
                                   echo "STEP-100Hz"

                             "100") VAL="1000"
                                    echo "STEP-1Khz"

                             "1000") VAL="10000"
                                     echo "STEP-10Khz"

                             "10000") VAL="1"
                                       echo "STEP-1Hz"

Once the BASH script is copied and pasted into a file called powermate.sh you need to make it executable by using the following command.

chmod 700 ./powermate.sh

If you now run the shell script in a terminal you’ll see a similar output to that shown below from the device when used.


As you can see above the shell script outputs a positive or negative number for VFO tuning and changes the VFO step size each time the Powermate is depressed.

Getting this output from the BASH shell script into Node Red is really simple to achieve using just 3 or 4 nodes.

In the Node Red development UI create the following nodes.

Griffin Powermate Node Red Nodes
Griffin Powermate Node Red Nodes

The first node in the flow is a simple inject node, here I called it trigger. This sends a timestamp into the next node in the flow at startup to set the flow running.

The Griffin Powermate node is a simple exec node that runs the script we created above.

M0AWS Powermate exec node
M0AWS Powermate exec node

Configure the node as shown above and connect it to the inject node that’s used as a trigger. Note: Change “user” in the Command field shown above to that of your username on your Linux PC)

Once done create the third node in the flow, a simple switch node and configure as shown below.

Switch Node for Powermate
Switch Node for Powermate

The switch node has two outputs, the top one is a text output that is fed into a text field to show the current step size of the Powermate device and the lower output is the numeric output that must be fed into your VFO control flow so that the VFO value is incremented/decremented by the amount output by the Powermate device.

I’ve found the Griffin Technology Powermate USB device works extremely well with Node Red and GQRX that I use for controlling the FCD SDR radio and it’s now part of my QO-100 ground station build.

M0AWS QO-100 Dashboard with Powermate Step Display at bottom
M0AWS QO-100 Dashboard with Powermate Step Display at bottom

As shown above you can see the Powermate Step size at the bottom of the dashboard, this text changes each time the Powermate device is depressed and will set a step size of 1Hz, 10Hz, 100Hz, 1Khz, 10Khz in a round-robin fashion.

The next stage of the build is the 2.4Ghz transmit path. I now have all the necessary hardware and so this part of the build can finally commence.

More soon …

20m – 10m Bi-Directional Slot Fed Antenna

The bi-directional slot fed HF antenna isn’t mentioned very often these days for some strange reason. It’s a real shame as it is an excellent antenna that gives high gain through the loop between the frequencies of 14Mhz and 29Mhz.

M0AWS 20m - 10m HF Slot Antenna
M0AWS 20m – 10m Slot Fed HF Antenna

Construction of the antenna is relatively simple, 3 x 3m long horizontal wires and 2 x 9.2m long vertical wires. I’ve modelled the antenna using 20mm diameter copper tubing for the horizontal conductors and 2.5mm wire for the two vertical conductors. Using the 20mm copper tubing provides a rigid platform for the mounting of the antenna on a non-conductive mast whilst reducing weight by using 2.5mm wire for the vertical conductors. You could of course use 20mm copper tubing for all the conductors if you have a non-conductive mast that can handle the weight.

An alternative option is to hang the antenna from a high tree and secure it in position with non-conductive nylon cord. This works very well and makes it extremely easy to manually rotate.

The antenna is fed at the centre of the middle horizontal tube (conductor 2 in the image above) using one of the following methods:

Method 1 – Use a 4:1 Balun and ATU either in the radio/Radio Shack or connected directly to the Balun. Connecting a remote auto ATU to the balun directly at the feed point is the best option as you will then have a perfect 50 Ohm impedance match to the coax cable going back to the radio. (I’ve used my AH-705 and a 4:1 Balun at the feed point in the past with excellent results).

Method 2 – Connect a remote auto ATU directly to the feed point of the antenna and then 50 Ohm coax back to the radio shack. This will provide a perfect SWR match on all bands and works extremely well. (I’ve used my AH-705 remote auto ATU in this configuration as well in the past, again with excellent results and no discernible difference to method 1).

Method 3 – Feed the antenna with 450 Ohm open ladder line and use a 4:1 Balun and ATU in the radio shack to match the antenna to 50 Ohm radios. It’s important to bring the 450 Ohm ladder line away from the feed point horizontally and not vertically downwards. This will then help to protect the radiation pattern.

Looking at the 2D Far Field Plots this antenna provides excellent gain at relatively low radiation angles on all bands 20m – 10m making it an ideal antenna for chasing DX.

20m Band 2D Far Field Plot
20m Band 2D Far Field Plot
17m Band 2D Far Field Plot
17m Band 2D Far Field Plot
15m Band 2D Far Field Plot
15m Band 2D Far Field Plot
12m Band 2D Far Field Plot
12m Band 2D Far Field Plot
10m Band 2D Far Field Plot
10m Band 2D Far Field Plot

The gain on each band is as follows:

20m Band – 7.83dBi at 24 Degrees
17m Band – 9.07dBi at 20 Degrees
15m Band – 9.63dBi at 16 Degrees
12m Band – 10.36dBi at 14 Degrees
10m Band – 10.99dBi at 12 Degrees

10m Band 3D Far Field Plot
10m Band 3D Far Field Plot

The 10m Band 3D Far Field Plot above shows the typical radiation pattern for the antenna. Maximum radiation is through the loop with very little high angle radiation making it ideal for chasing DX stations. Gain increases as frequency increases however, angle of maximum radiation decreases as frequency increases improving DX capability of the antenna on the higher bands. It’s worth ensuring that the antenna is rotatable as this will then enable you to point the antenna at the DX station to maximise signal strength at the DX end. Pointing this antenna North/South makes it great for working VK/ZL over the North Pole whilst at the same time being able to work South Africa from the UK.


Horizontal Wire Lengths: 3m @ 20mm Diameter
Vertical Wire Lengths: 9.2m @ 2.5mm Diameter
Modelled Height above ground at Centre (Conductor 2): 10.6m
Feed Type: 4:1 Balun + ATU / Remote Auto ATU / 450 Ohm Ladder line with 4:1 Balun & ATU

QO-100 Satellite Ground Station Build

Over the long bank holiday weekend I started putting together my QO-100 ground station. To start with I’ve concentrated solely on the receive path. I’ll start the transmit path once I have the receive path operational at a satisfactory level.

A few weeks ago I purchased a 1.1m off-set dish antenna and a Bullseye LNB. These have been sat in my garage waiting for the weather to improve so that I could start the build in the dry.

Fortunately we’ve had a mini-summer for the last 2 days and so I started work on getting the dish mount built. Using some timber from the local saw mill I made a braced 3m tall post which I screwed to the side of the cabin to provide a stable fixing platform. I used a couple of threaded bars to bolt through the walls of the cabin to ensure a solid fixing.

Next I mount the metal dish bracket to the top of the wooden post taking the total height up to around 3.2m above ground. This gives plenty of head clearance down below.

Next I assembled the dish and and attached it to the metal dish bracket at the top of the wooden post.

QO-100 1.1m dish mounted on the 3.2m AGL fixing

Attaching and cabling the Bullseye LNB was an easy job. I used some high quality coax cable that I purchase from the Satellite Superstore when I purchase the dish. I also had to set the LNB skew to -17.8 degrees. The marking on the LNB are tiny and go up in fives and so it’s pretty much impossible to get exactly -17.8 degrees so I turned it to 15 and then a tiny bit. It was as close I could get it!

Next I needed the information on where to point the dish. Fortunately there is a great web app on the BATC website where you can move a pin on a map to your location and all the information you need to align the dish is automagically calculated for you.

Armed with this info I set about aligning the dish. Getting it as close as possible I lightly locked off the dish and continued getting the coax in to the radio room so that I could connect it to my Funcube Dongle Pro+ (FCD) SDR receiver. Since the LNB needs a 12v DC feed I had to put inline a “Bias Tee” unit. This unit allows you to inject 12v onto the coax going up to the LNB but, stops it from coming back into the receiver. I used a Bias Tee that I purchased from Amazon with the Bullseye LNB.

Bias Tee mounted under the station desk

Connecting the coax to my Funcube Dongle Pro+ I was really pleased to see that I was receiving signals from the satellite perfectly well. I decided to take my laptop up onto the roof of the cabin and see if I could improve the reception further. To my amazement with very tiny changes in elevation and azimuth I was able to improve the QO-100 beacon signal by a further 10dB.

Being pleased with the dish alignment I started to tighten it so that it couldn’t move in the wind. Unfortunately this caused the dish to move a tiny amount which reduced the signal strength. I loosened the bolts off again and realigned the dish once more. This time when I tightened the clamps I did it a bit at a time on each bolt working my way round them so that the dish didn’t move. Doing it this way I still lost 1dB off the QO-100 beacon signal due to tiny amounts of movement but, decided I could live with the 1dB reduction.

QO-100 dish successfully mounted & aligned with HF antennas in the background

Below is a very short video clip showing a German station talking on the QO-100 satellite. As you can see the signal is nice and strong and extremely clear. I did find that the output from the LNB was actually too much for the FCD SDR and so I reduced the LNA setting in GQRX to 0dB. This reduced the background noise level considerably as the receiver was no longer being overloaded and made the signals much more prevalent above the noise floor.

Short video clip showing signal clarity from the QO-100 Satellite

I’m really pleased at the performance of the receive path and have now ordered the 2.4Ghz hardware from DXPatrol and Nolle Engineering so that I can build the transmit path.

I have also made some improvements to my QO-100 Node Red Dashboard so that I can work split on the satellite using my IC-705 and FCD SDR.

QO-100 Node Red Dashboard with ‘Split’ capability

Once the 2.4Ghz hardware arrives I’ll update the blog with progress.

More soon …