The contest club I am part of uses 2M Loop Fed Array (LFA) yagis for their QRO station. It’s always been advised to use a choke of some sort as close to the feed point as possible to prevent stray RF traveling back down the outer of the coax and into the station. The cheapest way of doing this is by creating a coax choke using 2 to 3 turns of coax around 2″ in diameter but this is also quite messy and risks fracturing the center conductor or foil in the feeder.
There are several commercial ferrite chokes available which replace the messy coax choke and one of our members has a large stock of unknown mix ferrite beads (which can be purchased in a pack of 5 for under £2) so we decided to test how well the unknown mix ferrites worked. Continue reading “Using cheap ferrite beads for an LFA choke”
Many people have asked for a better copy of my original FT-857 Manpack Frame over the past 5 years and I usually email a copy to them. Now, I have managed to get round to creating a larger print version for anyone that is having trouble reading the original file or who can’t open the DWG file.
Large format image (right click and save link to your computer)
Have fun building!
I’ve been running my TM-D710 in the car for a while using a Garmin GPSMap 60CSX which works well but does add clutter to the dashboard and is just another device to remove when leaving the car in a public place. I could upgrade to the newer TM-D710G but I can’t justify the £550 price tag just to get a built in gps so I have decided to add a gps unit to my existing unit.
Continue reading “External GPS for TM-D710”
I did this repair many years ago after the mounting failed on the X-300 (original single bold stub mast) which allowed the antenna to sway. It gave a few more years of service after the repair and mounting modification and was only taken down to be replaced with a new X-510 which has the same mounting modification.
The X-510 has been up for many years with no issues despite being battered by the winds and salt coming off the North Sea.
Continue reading “Diamond X-300 repair”
I love a good T2FD antenna and have built a good few. There’s a few variations but they all work well and are easy to construct. I’ve been asked a few time about the length and spacing so I made a small Excel sheet to work it all out and provide data for the 3 most popular variations.
Free free to download and use. The sheet is protected to prevent the formulas from getting messed up but if you would like to experiment with alternative formulas then please just contact me for the password. All I require is for my original credit to remain on any derivative works.
M0LMK T2FD Calculator
A cheap but very useful item of test equipment that would be an asset to any experimenter’s tool box. I picked up a BG7TBL Noise Source from ebay and built it into an enclosure.
There are reports that the PCB gets very hot during operation so mounted the entire PCB onto a piece of copper clad PCB which I also used to secure inside the enclosure. Continue reading “Wideband Noise Source”
I’ve been wanting to built a good 4:1 BalUn as part of the never ending project that is my HF antenna system for some time and today, I finally got around to the job. This is a “true” 4:1 Current BalUn that is wound as two separate 1:1 current baluns and then placed together to create the 4:1 ration. Any 4:1 built on a single core that claims to be a current BalUn is lying and is actually a Voltage BalUn! Continue reading “4:1 BalUn”
I usually get static build up on my HF doublet due to sand particles (I live above the beach) in the air so have been thinking about a way to bleed off the static and provide some protection to my TS-590SG. After a little research, I came up with this, a lightning arrestor/static bleed device that provides a permanent path to earth for DC whilst allowing RF to pass and providing protection from nearby lightning strikes. Continue reading “Ladder Line Surge Suppressor”
Another part of my antenna experimenting equipment. A simple ugly choke for HF made with 30 turns of RG213 coax around a 4″ plastic pipe.
I needed a 1:1 balun to use with my home brew doublet but I needed it to go between the ladder line and the SGC-230 tuner so it needs to have stud terminals on both the input and the output. I took a look around and decided that making one was the best option.
It’s made using 11 turns of figure 8 twin lead on two stacked FT240-43 cores. See the pictures below…
Continue reading “1:1 BALUN for ladder line”
I’ve been meaning to build a good 1:1 choke or line isolator for a while now and the parts have been sitting on the shelf for over a year. Well today I finally got around to it.
I chose to build something that would handle the full UK power limit (400W) with no problem and used G3TXQ’s excellent chart to select the best combination of core and windings.
Continue reading “QRO 1:1 Choke”
I like to take part in the 2M UKAC run by the RSGB when I can so I made a simple, lightweight 5 element yagi that I can put on my 10M mast and use portable.
Continue reading “Portable Yagi for 2M”
My poor FT-857 has had a rough life. It’s been used portable and usually ends up being thrown in a bag with the ATU, battery and other parts. I decided it was time to show it some respect and create a military inspired manpack to keep it safe and secure.
Continue reading “FT-857 Portable Manpack”
A quick post about my homebrew 100W dummy load.
Made by following the excellent instructions over at http://www.k4eaa.com/dummy.html, the basic dummy load is easy to build, cheep and effective. Every shack should have one. I used a 1 Litre paint tin and filled it with liquid paraffin to keep things cool.
Continue reading “100W dummy load”
I started to work on a simple APRS transmitter today so that I could use it as a antenna test bed for Project Swift.
It was very simple to build using only an Arduino Uno, a Venus GPS receiver a Radiometrix HX1 module (on 144.800Mhz) and an SMA PCB socket.
The completed board looks like this…
After playing around all day with the APRS message format, I managed to get it working and updating to aprs.fi via my own igate.
Next up will be a test with it installed in the car.
I’ve been using my Homebrew multiband HF vertical for a few months now and have decided that it’s time to have a go at laying a good radial system for it.
Continue reading “Building a radial system”
After deciding that my doublet works better than the multi-band vertical that I built from a 10M fishing pole, I decided that I wanted to try a mono band vertical.
20M seemed the obvious choice as I could use the 10M pole to create a 1/4 vertical with radials.
Continue reading “20M vertical”
I’ve had a vertical up for a while now but it was just a quick and messy install to test the results.
I have been pleased with them so have decided to have a go at installing the vertical in a better position with a more permanent solution…
Continue reading “Homebrew multiband HF vertical”
Since the test payload is now finished, I have started on the actual HABAT unit.
Here are some parts I have to get me going…
Continue reading “Parts for HABAT”
I finally managed to get the NTX2 and GPS working together thanks in no small part to NigeyS and fsphil from UKHAS.
One small problem still is that the RTTY signal from the NTX2 has a small “blip” in it that destroys the string. This must be an issue with my code somewhere as I can run some demo strings through the NTX2 using some simple code with no problems.
See the blip? Not sure what is causing it but I guess I better find out!
The blip was due to a drop in voltage. The GPS was drawing more current than the power source could supply. Plugging in a 1A 12V PSU fixed the issue.
So the weather station has been up and running for a while now but something has been bothering me. About twice per hour I get a “lost sensor contact” message from the software. Occasionally, it looses contact for a few hours at a time before it comes back.
Continue reading “Lost sensor contact”
I have started on the tracking transmitter that I will use to send dummy date to the HABAT via dl-fldigi. I have ordered a few GPS boards to use in the project and since I already have a Radiometrix NTX2, I have started work on the transmitter.
Continue reading “Basic tracking transmitter”
I will be using a Arduino the base building block of project HABAT.
The fact that is is mall, inexpensive and easy to work with are the main reasons that I chose the Arduino. There is also a large community of users who I hope to be able to turn to when I need help!
This Arduino will form the base of the tracking transmitter that I will be building to test HABAT.
So lets get project HABAT off to a start.
Like any good project, I need to break this one down into bite sized chunks. Here is what I have come up with:
Aim: To create a automated platform capable of receiving the balloons GPS coordinates, performing the necessary calculations to determine the balloons position relative to itself and then actuating a pan and tilt platform to aim a high gain yagi antenna at the balloon.
Sounds simple huh?
Continue reading “Breaking it down”
High altitude ballooning is an interesting hobby where you can launch a balloon into near space (100,000 feet) with a payload attached. The payload could consist of an RF tracking device so that you can follow the balloon, a digital camera to take images or an array of sensors like temperature, pressure and radiation.
Continue reading “High altitude balloon antenna tracker”
For future referance, the TG-UV2 has the same pin out as most Kenwood radios..
I made this up to help out anyone who wished to build their own programming cable for the Quansheng TG-UV2 handy.
The image shows the serial plug that goes on the other end as you are looking at the solder buckets.
Operations this weekend are taking place thanks to this impressive vertical.
Continue reading “Tempoary vertical”
Following the death of my cheap fibreglass tri-band collinear, I decided to have a go at constructing a simple dual band antenna for use at home.
I was looking for something that was vertical, omnidirectional and with good gain that I could make quickly and easily. The answer came from Sean, M3FVB in the form of his excellent article on building a 8db collinear.
Continue reading “Simple stacked J-pole for 2M & 70cm”
I have an SGC 211 ATU. Its a great bit of kit but I wanted to mount it outside.
A simple post for a simple job so here are the pics…
Continue reading “External enclosure for ATU”
I don’t have a permanent HF antenna set up at the moment and I wanted a weekend of operating so I threw together this Inverted V.
Continue reading “Temporary inverted V”
I was itching to get on the air with my new FT-857 so I made up a quick and dirty set of simple interface leads.
The FT-857 has a data port on the back and a digital mode that is selectable from the menu system. It also has a data port VOX function so any audio being presented on the data port will activate the TX.
Continue reading “Quick and dirty PSK leads for FT-857”
I love a good Yagi. I also love folded dipoles. So why not mix the two up and make a nice Yagi driven with a folded dipole?
This 12 element monster is easy to make and produces a theoretical 12.75 dBd gain. The dimensions were calculated using this tool. The details are: Continue reading “12 Element Yagi for 70cm”
I’ve got a strange fascination with folded dipoles. Single or stacked and phased, I just can’t seem to shake the need to build one from my head. So toady I have made a simple jig to help bend up a batch of folded dipoles.
Continue reading “Folded Dipole Jig”