Monday, 3 December 2018

$30 Low Power Echolink Node for the Shack

Over the years I've tried many different EchoLink setups. I have been dissatisfied with all of them. There were always too many wires or they consumed too much electricity or they were just too damned difficult to deploy.

For a while now I've been thinking about what I really want. What I really, really want. I came to the conclusion that I only need something that can be used in the shack to augment other activities there.  It has to be small, self contained, as few wires as possible and also portable.


I think I've achieved it! It's a complete EchoLink node (compute, RF, interface etc) in only 2 1/4 inches square (6cms). What's more it's entirely powered by a single USB connection.

I cannot claim that it's my design. I found it entirely by accident on Oshpark one day. Take a look at this web page by UR5TLZ. In turn he is using a software distribution called "Spotnik" which is based on SM0SVX's repeater software, SVXlink. I've used that software before.

The design is based on an Orange Pi Zero. With the addition of an RF addon board and some signalling transistors etc the OPi-zero can become a complete node. Unlike RPi-Zero the OPi-Zero has a built in bi-directional sound card that is presented to one of the many pins on the GPIO headers.


The addon board uses one of the Dorji DRA818 radio modules. This is a complete FM radio with built in CTCSS/PL facilites as well as audio in and out. It can operate at up to 1W but I have it set to 0.5W as otherwise the 5V supply fails. 0.5W is probably way too much for around the shack anyway. The rest of the components are SMD type soldered to the bottom of the addon board.

For my MMDVM project this summer I bought a load of surplus 433MHz spring style antennas. These would have gone into things like radio pagers, handheld radio's etc. I got 50 of them for $1.  So rather than add an SMA antenna connector and then install an external antenna I soldered one of the spring antennas in place of the SMA. The result is that I can now install the whole thing into the case without any extra holes being drilled.


I found that I needed to do a few mods to the design. Firstly, there is no RF decoupling capacitor in the PTT line. I found that the PTT would remain on when the software had something to say. Touching the antenna would make the PTT drop. The addition of a 100nF capacitor from the PTT to ground solved this issue.

The board set would not fit into the enclosure either. Upon further investigation I discovered that the issue was that the addon board aligned with the screw towers in the case thus preventing the set to slide in further. To overcome this issue I filed the corners from the addon board. Where they were square with a round hole in them as in the above picture, they are now a diagonal. The board set now fits into the case properly.

The sum total for this project was less than $50.

Orange Pi Zero  = $17
Dorji DRA818U = $8
Spring type antenna = $0.02
R's, C's, Q's etc = junkbox
PCB from Oshpark = $6 (you buy 3 units for $17 - use the spares to make one for your car?)
TOTAL = $31.02


You know you're in Virginia when ...

Even the menu is redacted. VA is the home of all those ABC agencies that may, or may not exist.




Monday, 5 November 2018

Stupid stuff you see at the Home Center

Yep, you guessed it. It's a toilet roll holder with a platform for your phone.

Add caption

Monday, 11 June 2018

More power!!!!!!!!

I own a 2018 Dodge Grand Caravan. It's the baseline model with absolutely no frills or addons whatsoever. And that included things like USB charging outlets. So I decided to add a few outlets of my own.

The USB outlets were purchased from amazon and are wired in parallel with the cigarette outlet so that they will follow the ignition. The Anderson Powerpoles are wired directly to my Ham Radio fuse box in the back of the van and are fused for 10 Amps. Again, the outlets were purchased from Amazon. I also purchased a set of large step-drill bits. The required holes for the outlets were 1-1/8" and you can see the remnants of the panel on the floor. I was able to source a replacement panel just in case I sell my van. I can then return it to factory condition.


Can you prove you have a brain?

Can you prove you have a brain? I can! Take a look at this. It's an MRI (one of MANY!!) of my brain. Clever bastards reading this will be able to spot my 1/2 ventricles, 3rd ventricle and 4th ventricle. Look really close you'll also see a Pineal Cyst right at the back of my 3rd ventricle.


According to my brain guy (he's my 3rd on this journey) my enlarged ventricles are suffering from something called Obstructive Hydrocephalus most likely cause by the Pineal Cyst. And whilst the ventricles are not "impressive" (thanks, Doc) my other symptoms were causing alarm. Alzheimer's like memory issues, incontinence, difficulty descending stairs, wide gait etc, etc, etc. So it was decided that we should "fix" the issue. The Ventricles are full of spinal fluid and because the fluid cannot drain as normal its like inflating a water balloon in my head.

I was scheduled for a procedure to install a VentriculoPeritoneal Shunt. Basically its a McDonald's straw connected to a valve that then dumps out into your stomach. After almost 9 months of chasing this issue down and a few wrong diagnosis and even being thrown out of a brain surgeon's office (thanks, Penn Med!!!), being told another surgeon did not have the tools for the job I ended up at Jefferson University Hospital in Philadelphia. These guys know what they are doing!!!

The night before surgery I had to shave my head.
Surgery day was June 1st 2018. As I write this I am 10 days post surgery. I'm still very sore but getting 500% stronger every day.

Erin and I share a laugh in the pre-op waiting room. My head is shaved but yet still I have to wear that ridiculous hat. 
So in a nutshell they put a hole in my skull. Into the hole they inserted a tube which was pushed through my brain into the right side Ventricle. This will allow the buildup of fluid to drain safely and thus deflate the balloon effect.


This is the hole they put in my head. You can clearly see the tube exiting under my skin to the right.


Here we can see the valve placed under my skin on the side of my skull. There's another tube that goes behind my ear, down my neck, across my collar bone and eventually to my abdomen in a single feed. That's the output with the waste spinal fluid.


Finally, the tube arrives in my abdomen where they cut me open, grab the end and secure it behind my muscle wall. Of all the wounds I got this is the one that hurts the most!!!

The tube from my ear to my abdomen is one complete section. The surgeon basically stabbed me from my ear to my stomach in one go. He used a sharp long steel tube with a wooden handle on the end and rammed it under my skin. I can actually feel the hose!

So that's pretty much it. I'll have to go for annual checkups on it and even though mine is an "MRI Safe" model I will still need x-rays taken before and after I get another ride through the MRI scanner. This would be so they can tell if the valve settings have changed. I'm good for up to 3 Tesla's - whatever they are? It also has a service life of about 5-7 years so I'll be back in there fairly shortly. Although, I'm told a replacement is not as bad as an initial installation. I'll let you know.




MMDVM based digital modes hotspot

Now that there are so many different digital modes around for the V/UHF bands I decided that it was time I had a hotspot that could cover all the modes at the same time.

I've been following G4KLX's MMDVM project since it's initial inception and have even donated one of my NQSMHS modems to the project (it started out as a D-STAR project). Today the project has gained quite some momentum and is now able to run on a Raspberry Pi Zero W along with other hardware addons such as screens and buttons etc. Significant work has also gone into creating a RPi distro explicitly for the MMDVM.

My hotspot is based on the RPI0W and ZumSPOT hotspot board that you can get from HRO here in the US. I followed this HowTo which said to download the latest image from the PiSTAR site and transfer it to an SD Card (just like any other RPi distro).


And this is the finished result. The 3D printed case is by George, M1GEO and is available from Thingiverse. It only supports a 3.5" Nextion LCD display but having also tried a 2.8" display I can tell you that you want the bigger screen! I have asked George to knock up some designs for other screen sizes and also to add some cooling holes into the box as it can get quite hot in there after a good round table QSO!

The Nextion screen is quite clever in that you upload a handful of screen images to it when setting it up. These images also have various text fields that will be populated with data every time the MMDVM host sends some info to the screen (eg, which screen image to display, what frequency, RX Callsign etc). Below is a selection of the screens that mine does.

The bootup screen. I decided to abandon this particular one as I couldn't really see it properly.
Traffic arriving from the Internet. This will be broadcast via the built in 20mW TRX. Note the RPi3 mounted next to it on the left. That's an Echolink system.
It's listening for my local input. It'll do this for 10 seconds. If I do not respond in YSF (in this case) it'll drop back to listening for any mode.

Receiving my YSF signal from my HT in the shack. Note the BER. This is quite high and can be attributed to overload in the RX. When I'm on the other side of the room the BER is down to almost 0%.

Monday, 5 February 2018

Anytone Apollo 1 "10 Meter" CB mod

On a recent road trip to Detroit I spent almost 12 hours of silence in my car. My Ham radio was on but nobody was heard. I have found this to be the case on many road trips of late. That's why I installed an HF radio into the car - maybe I can talk to people further afar? Not on this trip at least. So I tuned my HF rig to the CB channels and was able to have some interaction with other travelers on my route.

This led me to thinking that I need a CB in my car. But I don't have room for another display on my dashboard. Looking around the usual online places I found this Anytone Apollo 1 "10 Meter" CB. Out of the box it comes preset to 40 channels between 29.4-29.6MHz. Great! I have a license for that. I had also read reports that it could be modified to cover other frequencies such as CB too.

The manual isn't too bad for a Chinese radio. And it does indeed explain how to change the 10 Meter frequencies. However, one has to take it apart and remove some solder links to get it going on other frequencies. The manual does not tell you how to do that. So I took mine apart to see what I could find. The usual caveats apply. Do this mod at your own risk. Your mileage may vary. I take no responsibility. Ask your doctor if Viagra is right for you.

Remove the power from the radio and unplug the microphone. Using a T8 Torx bit unscrew the bottom panel and also the face plate. This will reveal 2 solder jumpers at the very front of the board almost in the middle going across. See the below pictures for guidance.



Using a solder pump or wick remove the solder from the 2 Jumpers being careful not to disturb the SMD parts just above the pads.


Before putting the covers back on power up the radio and check that it still works. You should notice the display now shows "EUH 01" indicating that your radio is on CB channel 1.

Just for good measure do a factory reset too.

  • Power the radio off by using the mic "POW" button.  
  • Hold the "FUNC/FRQ" and "POW" buttons at the same time. The display will read "RE S"
  • Release the "FUNC/FRQ" button. The radio will power off.
Here are some before and after shots of my rig.



Before putting the covers back on the radio take a look at the face plate. Can you see how much room there is on the inside of it? It occurs to me that one could add 2 small toggle switches to the plate. Wire them to the solder pads on the radio's PCB and now you can dynamically change the frequency of the radio without a soldering iron. I've ordered some small switches. More about that when I get them.