DIY "Wonder Loop" QRP Antenna

Submitted by gerry on Wed, 04/19/2017 - 16:26

I am a member of a group on Facebook that shares and discusses antenna designs, usually of a portable nature. Recently the topic of the WonderWand WonderLoop antenna came up, particularly how expensive it is relative to its apparent complexity. A number of members had posted pictures of a torn-down control box, and it really seemed to contain little more than a transformer wound on a mix-6 toroid and a variable capacitor. 

mcHF: a Next-Generation QRP SDR kit - Part II

Submitted by gerry on Mon, 03/13/2017 - 13:01

Since the last post, I had gotten involved in a Facebook group with a focus on the mcHF transceiver. As well as being a great forum for sharing knowledge and experiences, it gave me the opportunity to get a very nice case in a group buy organised by one of the members. The case is 2-part design, which is easier to work with than the one I bought  previously. It also comes with buttons, a speaker and very nice machined aluminium knobs.

New run of the Sparetime Gizmos SBC6120

Submitted by gerry on Thu, 03/02/2017 - 09:16

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

PDP8 Flipchip boards

into this...

DIY 10dB Pi-Attenuator

Submitted by gerry on Thu, 02/09/2017 - 09:26

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. 

Parental Control using OpenWRT

Submitted by gerry on Tue, 02/07/2017 - 22:47

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.

Reflashing the Meraki MR12 AP with OpenWRT

Submitted by gerry on Mon, 01/30/2017 - 22:45

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. This in effect makes the unit useless. Unless...

Morse Code Beacon for the Raspberry Pi

Submitted by gerry on Wed, 08/10/2016 - 22:38

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.