CD4007-Based Voice Changer

Voice Changer (Ring Modulator) based on CD4007

This project is my entry to the 7400 Contest. It's a Voice Changer/Distorter based on a CMOS IC originally intended for digital use, the CD4007 IC. CD4007 contains two Complementary MOS pairs with the third pair connected as an inverter.

Simulation: Single Balanced Modulator

Warming up for a personal project in my virtual lab. This Single Balanced Modulator based on MOS devices will be one part of the project. 

Here are some simulation screenshots before I make the actual circuit.

LTspice Transient Analysis
Circuit under test above plotted trace

LTspice FFT Analysis

Simulation: Headphone Passive Bass Enhance

LTspice simulation

Acer Aspire 4715z Touchpad Repair

Here's another quick video on a repair job on my Acer Aspire 4715z. This time, it's a replacement for the tactile switches on the touchpad (they died during the popularity of Plants vs. Zombies :D).

Acer Aspire 4715z Keyboard Replacement

My Acer Aspire 4715z has served me for 3 years now. Unfortunately, its keyboard is already missing a lot of keys (picked by my daughter Anika when she was one). Typical laptop repair costs around PhP 2000 but I found a replacement keyboard on eBay, and, it only costs approximately PhP 650 (including shipping).

Nillkin Hard Case For My Cherry Mobile Magnum

I just received my Nillkin Protective Case for my Cherry Mobile Magnum. I purchased it from ebay (at approximately PhP 870.00) as custom-fit cases and screen protectors for the Magnum are rare, if not available locally. The case is for Huawei Ideos X6 U9000 which is the same unit as the Cherry Mobile Magnum.

Android Phone Audio Signal Generator

An Audio Generator is a very useful tool in a hobbyist's lab especially during experiments and testing of audio circuits such as amplifiers. Unfortunately, this is one of those equipment that a hobbyist may not be willing to buy (that includes me) as it may not serve him much in other circuits i.e. digital circuits. Fortunately though, there are Virtual Instruments available for computers, and now as smartphones get smarter, they are now also available on phones.

Iwatsu SS-7810 100MHz Analog Oscilloscope

One great scope for serious hobbyists on a budget

HP 54503A 500MHz Digitizing Oscilloscope

Perhaps I was lucky enough to have owned this scope :D

Just Another Day At Work: Band Filter Testing

Quick and dirty Scalar Network Analyzer
Graph is noisy as there is no video filter after the detector

While waiting for a Network Analyzer, a quick and dirty Scalar Network Analyzer is realized by using an Anritsu Signal Generator on sweep mode, Analog Oscilloscope on XY mode, and a ADL5513 Log Detector. A box on the grid denotes 10dBm, thus, rejected bands are 40dB below passed bands. Both passed bands are Globe's GSM 900 bands, rejected bands are first 25 channels of Globe, and Smart's GSM 900 bands.

These Band Filters are replacement for the Frequency Shift Filters found on Globe's Frequency Shifting Repeater. The Project is to modify these repeaters to Band Selective Repeaters.

From Frequency Shifting, it's now Band Selective

Top 5 Android Games On My Cherry Mobile Magnum

With my Cherry Mobile Magnum, gaming on my mobile has been more fun. For now, here are my top 5 favorite games (most of the times, Angry Birds bore me :D).

Cherry Mobile Magnum HD: First Impressions

I've been reading about the Cherry Mobile Magnum HD since last year. Specifications-wise, it's nearly the same as HTC Desire HD, running on a 1Ghz Qualcomm Scorpion Processor and an Adreno 205 Graphics Processor (Qualcomm MSM8255 SoC - Snapdragon). Just last month, Cherry Mobile slashed off the prices of their Android products putting the Magnum at just PhP14,000 (also their tablet, Superion, is now only 14,000). At this price point, I guess it's one deal I can not pass. I now have an early Christmas and Birthday present for myself. :D

Playing "Pusoy Dos" on Android: Big Big Big 2

Pusoy Dos is one of the card games I grew up with. While it's far too easy to get a Texas Hold 'Em Poker game for my Android, Pusoy Dos or Big 2 Poker is not as common. One of the Pusoy Dos games that can be found on the Android Market is big Big Big 2 from 2-Person Studio. By far, I can say that it's the best that I've played on my Android phone.

2 Cool Ways To Take Screenshots on a Rooted Android Phone

Taking screenshots on an Android phone can sometimes be a pain. The most referenced way of doing this is using the DDMS or Dalvik Debug Monitor Server. This requires the installation of Android SDK on your computer which consequently requires the installation of Java Development Kit. While the method is intended for developers, it also works quite well for casual users.

With a rooted phone, I find 2 cool and easy (and best of all, free) ways to take screenshots. The first one makes use of a browser on your computer, and the second one is done on the phone itself.

Software Data Cable for Android

For all Android users who always misplace (that would be me) or doesn't want to carry their USB Data Cable, this is the application for us. Software Data Cable, by Proid Mobile, Inc., turns your Android device into a FTP server - a file server that can easily be accessed through a network. For Android devices, that would typically be through WiFi.

Qucs: Quite Universal Circuit Simulator

Qucs is an open source circuit simulator that is, quite universal. It can solve from DC and AC analysis, to circuit S-Parameters. It can also design matching networks and filters. It's not yet finished (here's the roadmap to what is already available and what the project aims to include), there are some quirks with the GUI, and it is hard to troubleshoot some error messages. But as it is, I already find it useful.

Just Another Day At Work: Prototype Antenna Testing

One of the exciting parts of work, doing actual field tests. Antenna is mounted at the side of a small multicab.

Building my pfSense Machine - Reviving my Old Desktop

For quite some time, I’ve wanted to have a second internet connection. We’ve been served by PLDT DSL for 7 years now and I can say that the connection is quite reliable, though, it also has down times. I’ve wanted to have a continuous internet connection even when one connection is down, a failover. I also wanted to distribute the load between two connections, to minimize slowdown when somebody is downloading a large file or watching some video in YouTube.

Just a week ago, we registered for that second internet connection, wi-tribe’s WiMAX network. We opted to try wi-tribe, as their nearest base station to our home is just a block away, or, roughly, just 30 meters away. I cannot yet say whether the connection will be reliable for the days to come, but so far, it’s providing a continuous connection at consistent speeds of 0.7Mbps to 1Mbps.