On the front of the head is the filter carousel. In this case it’s only fitted with a 2.5mm Aluminium filter. These are used to filter out the low-energy X-Rays from the beam, reducing the overall dose to the patient of radiation that does not contribute to the resulting image,
A while back I found myself in the need of an adjustable RF attenuator capable of high-GHz operation. As luck would have it I had an old Spectrum analyser on the shelf at work, which we had retired quite some time ago. Spectrum analysers being quite capable test instruments, I
Recently I found the need to do some measurements on 75Ω CATV equipment, only having 50Ω test equipment to use. For this, matching networks exist to convert 50Ω to 75Ω, but they’re fairly simple, so building them was a viable option. Above is the very simple schematic to create the
There’s a common problem with all Software Defined Radios – their input stage is wide open, and therefore susceptible to desensitisation by local high power transmitters. The main culprits are broadcasts in the FM band, from 88-108MHz. Commercial stopband filters are available to solve this issue, by cutting out the
There’s quite a nice desktop app for the new NanoVNA v2, NanoVNA-Qt. It’s released as an AppImage for Linux, but unfortunately there is no version to run on a Pi supplied. The version below is built to run on the latest version of Raspbian (as of writing this, 2020-05-27). Enjoy!
Since I inherited an old HP 8753C Network Analyser from work, I figured updating a few things to relatively modern standards would be good. The factory CRT, being 28 years old, is definitely getting a little tired, not to mention being slow to warm up. I read over on the
This enormous box is the S-Parameter Test Set from a HP 8753C 3GHz network analyser. This unit contains the required components to automate the testing process for items such as cables, antennas & RF networks. The main EUT test ports are APC-7mm type connectors – a very expensive genderless RF
Since I fitted the new “8kW” diesel heater to the camping power trolley, it has occurred to me that there is a lot of energy in the exhaust gas stream that ordinarily would be wasted into the atmosphere. Since we’re all still on lockdown here in the UK, I figured
Since rebuilding the burner for the Webasto water heater on board nb Tanya Louise, I figured it was about time I sorted the exhaust out as well. The standard Eberspacher / Webasto type exhaust system components are shit. Nothing is properly gas tight, no matter how you build the system,
Since the entire country is on Coronavirus lockdown at the moment, I figured it was time to get round to finishing off a couple of small blog posts while waiting for the restrictions to be lifted 😉 This is a small two-stage linear amplifier module available on eBay fairly cheap
Time for another projector! This one was brought to me with a fault, described as a shadow in the middle of the image, shortly after the lamp was replaced after exploding. This is an older DLP projector, with a UHP mercury lamp. I’ve already removed the top cover of the
I figured it was about time I added to the medical kit, and since Contec, who makes my SPO² meter seems to have a decent level of manufacturing quality, one of their ECG machines seemed like a good choice. This is the ECG80A handheld Electrocardiograph. This is a single channel,
It recently became rather obvious there was something amiss with the water heater on board nb Tanya Louise – lots of smoke from the exhaust, failed starts, and finally a total refusal to start altogether. On disassembly, it was clear the burner was the issue – above. The mesh at
eBay yet again doesn’t disappoint when it comes to fake kit. Here is a claimed dual-band antenna, a Nagoya NA-771. This is supposed to be good for both 144MHz & 433MHz. The first clue is in the logo printing on the base, it’s not straight, or even. The base isn’t
Yet another wonder of Chinese mass-production, this is a cheap (£10 shipped) oil/fuel transfer pump from eBay. Primarily intended for removing oil from engines through the dipstick tube, these are usually sold for all kinds of pumping uses. As will become clear, pumping highly flammable liquids with these might just
Another Chinese eBay teardown! This is a “720p” LED projector, available from nearly everywhere for very little cash. But they are very little cash for a reason – they’re total shit. The resolution as stated is a blantant lie – the LCD panel used in these is usually around 320×240,
Well, this is what happens when a Variac rated at 3A is subjected to 15A for a while – a complete burnout. The smell associated with this failure was formidable, it’s a shame I can’t convey odour through photos! Above is the burned section of the winding (it was set
These projectors were very popular when they first appeared on the market with the laser hobbyist community, and for very good reason – they contain a massive array of 445nm Royal Blue laser diodes in their optics engine. Originally very expensive, these units can now be had for under £50
Here’s a recently failed 5W GU10 lamp, which is completely dead – not even a single LED still shining. According to the markings, this lamp draws 50mA at 230v & outputs 345 lumens After popping the lens off the body, the failure mode is obvious. The top right LED has
This unit recently appeared on eBay, as a spare part from a refrigerant charging machine, and I figured it would make a good explorational post. This unit analyses the purity of R-134a refrigerant gas, using an Infrared sensor cell, and communicates over RS-232. The sensor cell itself is at the
Time for another eBay delight! This is a little UV lamp for curing false nail glues. These are definitely taking over from the older Fluoroescent tube based units, and seem to work well enough. In my case, they work well for exposing UV-sensitive PCB substrates for etching as well! Here
Having had a wee issue with Jellyfin Media Server’s database this week after an upgrade, I decided to avoid the requirement for a 24 hour database rebuild, to start backing things up with Borgmatic. Borgmatic is a handy wrapper script to automate BorgBackup.
Jellyfin Borgmatic Config
# List of source directories to backup.
# Path to BorgBackup repository
# Retention policy for how many backups to keep.
# List of checks to run to validate your backups.
# Custom preparation scripts to run.
- systemctl stop jellyfin
- systemctl start jellyfin
This is a very simple configuration,
Here’s a blast from the past, before the time of GSM networks. This is a power amplifier from an Analogue mobile phone, on the ETACS system. This unit will output, according to the TACS standard, about 10W of RF power in the 900MHz band. RF connections on this unit are
So, it’s time to finish off the upgrades to the core storage server on my network. Now a new motherboard, CPU & RAM have been obtained (MSI GA-X58-USB3), Core i7 950, 12GB), along with new SAS/SATA HBAs for the disk rack I can get everything fitted into place. Proper branded
So I figured it was time to get a hardware update sorted for my network’s core storage server, which I have posted about before. The way I had the drives anchored to steel rails really doesn’t make moving or replacing disks easy, so a proper case needed to be sourced.