gerryk.com

Wherein I write about things that interest me….

New run of the Sparetime Gizmos SBC6120

I have been following the Sparetime Gizmos Yahoo group since I first heard of the SBC6120, basically a single-board computer reproduction of the DEC PBP8. It was based on the Harris Semiconductors HD6120, which is basically a PDP8 CPU on a single chip, as opposed to multiple flip-chip boards. So, in essence, turning this into this… However, the HD6120 is in very short supply, and expensive, and the Sparetime Gizmos board is out of production, and Bob Anderson has said that he will not be doing any future runs. Read more →

Building KV4QB’s SNA Jr II

57,I came across the highly informative and interesting website of DuWayne KV4QB through Bill Meara M0HBR who has the excellent Ham Radio podcast Soldersmoke. DuWayne has documented many projects on his site, but one that caught my attention is the SNA Jr II. An SNA is a Scalar Network Analyser, which is a device that has the capability to measure RF amplitude. The SNA Jr II is the second iteration of this project by DuWayne, and is based on a number of enexpensive modular components. Read more →

DIY 10dB Pi-Attenuator

Attenuators are expensive, especially the fancy calibrated ones, and it seems that they are the only ones available. SMD resistors are cheap, though, and I have SMA connectors, so I thought I would try to make my own. I used the calculator;here, to come up with a design that used resistors I had, gave an impedance of 50 ohms and an attenuation that was useful (10dB). The schematic for the attenuator is as follows. Read more →

Parental Control using OpenWRT

As a parent, I am somewhat torn regarding ‘parental control’ of Internet Access where my daughter is concerned. She is 8, so has limited access anyhow, but I would like for that access to be as unrestricted as possible while at the same time avoiding her stumbling any age-inappropriate content, which as we all know can often be only 2 or 3 clicks away. I have decided on a multipronged approach, with the main home router, a TP Link N600 running OpenWRT Chaos Calmer being the crux of this. Read more →

Reflashing the Meraki MR12 AP with OpenWRT

Meraki (now part of Cisco) are well known for their high-quality enterprise grade networking hardware. Over the last number of years, they have been promoting their kit by way of providing ‘evaluation’ units for the cost of simply attending a webinar. They specify that the attendee should be a ‘networking professional’, but it is possible that not every attendee is. I recently acquired a number of these, where the evaluation period had expired, and the cloud-management interface was no longer accessible without a license key. Read more →

Reflashing the SamKnows TP Link Router

SamKnows;is a global Broadband Quality Monitoring service. They are funded by a number of national regulatory bodies, including the FCC and OfCom, and are to all intents unaffiliated. On sign-up, they will ship a heavily customised;OpenWRT, mainly for its rich collection of addons and customisability. It might be a little harder to get to grips with than Tomato or dd-wrt, but I fell the additional functionality makes it worthwhile. A build of;OpenWRT 15. Read more →

Morse Code Beacon for the Raspberry Pi

Among other great features of the Raspberry Pi is the General Purpose Input Output array (GPIO). This is an array of pins that can be programmed to behave as pretty much any I/O type that can be represented digitally. The pins can be switched on or off to represent binary 1s and 0s and controlled so as to emulate any communication protocol that uses bits (I2C, SPI, RS232 etc. etc.). However, as a first attempt at working with GPIO, I took a recommendation from Steve EI5DD and wrote a program that will key a transceiver and generate morse code. Read more →

SSTV on Raspberry Pi

Following a suggestion by Galway VHF Group mamber Steve, EI5DD, I thought I would give SSTV a shot. It’s not a mode I have any experience with, apart from hearing the transmissions at 14.230MHz when I tune around. Steve mentioned a cross-platform SSTV program QSSTV, which seems to run well on a Pi 2, so that’s what I decided to use. I have a Pi 2 that I use for playing with SDR and radio software already set up with the current Rasbian (wheezy). Read more →

a small matching unit to use the watson w2000 triband antenna on 70mhz

I recently upgraded my shack to an;ICOM IC7300, which in the EU specification includes the 4 meter / 70MHz band. I do not have a vertical for 4m, or space for one right now, but had read about others using a small matching unit to provide the necessary match using the;Diamond V2000, or Watson W2000, as my version is badged. Two blogs I got my inspriation from are;Miguel EA4EOZ’s blog;and that of;Tony EI4DIB, so having done some reading, and some rummaging in the junk box to see if I had the requisite parts, I got to work. Read more →

Plotting Antenna Response using a Wobbulator and Return Loss Bridge

At the Mayo Amateur Radio Rally a couple of years ago, a NI ham, Tom Herbison, MI0IOU was selling an interesting kit for the Raspberry Pi. It combined an Analogue Devices Clock Generator (AD9850) and an RF power meter (AD8307) to give a programmable sweep generator & detector… commonly known as a Wobbulator. I bought one and had anenjoyable afternoon not long afterward building it. It was a relatively easy build, and I got some use out of it tuning some Band Pass Filters I had built for use on multi-station portable ops. Read more →