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
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.
The male to male SMA connector that Neil, G7UFO kindly posted to me arrived late this afternoon and I wasted no time getting it connected between the 2.4Ghz up-converter and the 12w amplifier.
Male to Male SMA connector for QO-100 Ground Station
Initially when I powered up the 12v to 28v converter board the output voltage was only showing 22v and so I had to adjust the onboard variable resistor to get the voltage closer to the recommended 28v for the amplifier. I decided to run the amplifier at 27v so that it wasn’t being pushed to it’s full and so readjusted the voltage converter back down to 27v. This seems to work very well with the amplifier not getting very warm at all during use.
M0AWS QO-100 2.4Ghz Uplink Hardware.
Getting on air I was really impressed at how strong my signal was on the 10Ghz downlink. With my own signal peaking 5/9+10dB I was very happy with the performance of the ground station.
I made a few contacts very quickly with the first being OH5LK, Jussi from Helsinki Finland. Jussi was actually the first station I worked on CW too when I was running just 200mW, it was great to have him for both of my first contacts on QO-100.
I then went on to work a few stations from Wales, Germany, Poland and Belgium but, the one that I was totally shocked to get on my first real day of QO-100 operations was ZD7GWM, Garry (HuggyBear) on St. Helena Island, South Atlantic Ocean. This is an Island that I have never had a contact with before on any band and so I was extremely happy to get a new first especially on my first QO-100 day.
Garry and I chatted for some 25 minutes covering many topics, it was great to have an armchair copy over such a distance, something that would be impossible on the HF bands. What a great way to start my QO-100 satellite career!
One of the things I really like about the operators on QO-100 is that they have time to stop and chat, this is so refreshing and a rarity today. I’m really going to enjoy this satellite.
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
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
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.
For some time now I’ve been using my Funcube Dongle Pro+ (FCD) as my QO-100 downlink receiver. It’s worked fairly well and has given me the ability to listen to stations on the satellite over the last few months.
During this time I have noticed a couple of things about the FCD that has lead me to the final decision to change to a new SDR device.
The first of these ‘things’ is the fact that the FCD gets seriously overloaded when there are multiple large SSB signals within the receive pass band. The only way to manage this is to constantly keep changing the software based AGC, mix and LNA settings to reduce the levels of the incoming signals so that the overloading stops. This is great except when you tune to a quiet part of the satellite transponder you have to turn all the settings back up again to be able to hear the weaker signals. After a while this becomes tiresome.
The fact that there isn’t a hardware AGC in the FCD is a major drawback when being used for satellite reception especially when it’s on the end of a very high gain LNB and dish antenna.
The second of these ‘things’ is the fact that I can’t see the whole transponder bandwidth at one time with the FCD as it has a very small receive bandwidth capability. This means that I am constantly tuning up and down the transponder to see if there are any stations further up or down in frequency.
Funcube Dongle Pro+
Talking to more experienced satellite operators in the Matrix Amateur Radio Satellites room they recommended replacing the FCD with a NooElec NESDR SMArt v5 that has hardware AGC and is capable of receiving and displaying a much wider bandwidth.
Looking on Amazon the NooElec NESDR SMArt v5 is only £33 so I decided to place an order for one and give it try.
In typical Amazon style the SDR receiver arrived the next day and I wasted no time getting it plugged in and connected to the QO-100 ground station.
The NESDR SMArt v5 is based on the well known RTL-SDR that came onto the market some time back but, has a number of improvements in it that take it to the next level.
The first thing that I was happy with was the fact that the GQRX SDR software I use recognised it immediately on startup, no configuration or drivers were required it just worked, straight out of the box. Since I use Kubuntu Linux on my radio room PC I did wonder if I would need to get into installing extra libraries etc but, thankfully none of that was required.
Looking at the signals from the QO-100 satellite initially they appeared to be nowhere near as strong as they were on with the FCD. Looking at the settings in GQRX I noticed that the hardware AGC was off and the LNA setting was back to it’s default very low level.
I switched on the AGC and then increased the LNA setting to 38.4dB and found that the signals were now plenty strong enough on the display but, not overloading the receiver.
I then went on to adjust the display so that I could see the whole satellite transponder bandwidth on the screen. This is great as it enables me to see the low, middle and high beacons that mark out the narrow band section of the transponder and at a glance see all the stations using the satellite. This was a massive improvement in itself and one that I am very pleased with.
NooElec v5 SDRNooElec v5 SDR
Using the NooElec NESDR SMArt v5 SDR it very soon became clear that it copes with multiple large signals in the pass band so much better than the FCD did. There’s no more overloading of the receiver, no more ghost signals appearing on the waterfall due to the front end not being able to cope and no more having to constantly keep playing with the settings to get things under control. The hardware AGC built into the SDR device does a great job at keeping it all under control whilst receiving a much wider bandwidth than the FCD ever could.
The satellite beacons are now received at S9+15dB without the receiver being overloaded, the first time I have seen this since starting out on my QO-100 venture.
The other thing that became obvious very quickly is that frequency stability is much better than it was with the FCD, it doesn’t drift up and down the transponder now and stays tuned exactly where I put it. It’s also on frequency whereas, the FCD was always 1.7Khz off frequency.
GQRX showing QO-100 Transponder signals
The NooElec NESDR SMArt v5 is very well put together, it has an aluminium case that acts as a heatsink (it does get warm!) and overall the build quality is much better than the plastic cased FCD. When I think that I paid close to £100 for the FCD and the NooElec NESDR SMArt v5 only cost £33, I am amazed at the build quality.
Overall I’m extremely pleased with the purchase of the new SDR, it slotted in perfectly as a replacement for the FCD, works great with GQRX, my QO-100 Node Red Dashboard and performs considerably better than the FCD. Overall money well spent!
You can find the NooElec NESDR SMArt v5 spec sheet here.
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
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
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.
M0AWS Waterproof enclosure from ScrewfixM0AWS Laying out the 2.4Ghz TX kit in the enclosureM0AWS LMR-400-UF coax from Barenco
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.
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
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)
Properties:
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.
#!/bin/bash
###############################################
# Griffin Technology Powermate control script #
# for Node Red. #
# #
# 04/06/23 - M0AWS - v0.1 #
# #
###############################################
VAL="1"
echo "STEP-1Hz"
/usr/bin/evtest /dev/input/powermate | while read LINE
do
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"
;;
esac
;;
esac
done
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
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
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
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
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.
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 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 17m Band 2D Far Field Plot 15m Band 2D Far Field Plot 12m 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
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.
Summary:
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
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.
QO-100 Dish MountThrough wall bolt
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.
Following on from my 2m Band Eggbeater Satellite Antenna here’s the design for the 70cm Band version that will enable duplex satellite operation.
The design is basically the same as the 2m antenna but, with smaller dimensions. All modelling has been done with the antenna at 5m AGL.
70cm Band Eggbeater Satellite Antenna
Each of the Eggbeater loops has a conductor size of 5mm and a circumference of 73.5cm with the radials exactly 5cm below the bottom of the loops. The 8 radials are exactly 34.15cm long each. The distance between the bottom of the eggbeater loops and the radials must be 5cm to get the best radiation pattern from the antenna.
With these dimensions the antenna has an SWR of <1.5:1 across the whole 70cm band making it ideal for both satellite and general repeater/SSB working.
70cm Band Eggbeater Satellite Antenna 3D Far Field Plot
The 3D far field plot shows that the antenna has a good mix of high and low angle radiation that makes it ideal for working satellites at all elevation angles.
70cm Band Eggbeater Satellite Antenna 2D Far Field Plot
The 2D far field plot shows that the antenna has the following high gain lobes:
The null at the top of the antenna isn’t as pronounced as on the 2m model and so this antenna should perform better when the satellite is directly above. Just like on the 2m band version, this antenna must also have a feed phase angle of 90 degrees between the two eggbeater elements. It’s very important that the phasing harness is built accurately as it can impact the radiation pattern of the antenna if the phase angle isn’t correct.
ON6WG has written an excellent article on how to create the phasing harness using 2 pieces of coax cable, this is an ideal solution for this antenna.
I had a listen for the ISS FM Repeater this morning using my Dual Band End Fed Vertical Dipole antenna. Not the best antenna for satellite chasing especially since it was a high angle pass this morning however, I did get a relatively good copy on the ISS before it got too high in the sky and fell into the null at the top of the vertical.
A short clip form the ISS pass 25/04/23 AM
I think with an eggbeater antenna reception will improve considerably.
More soon …
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