As a service to my readers and for my own future knowledge, I wanted to explain how to move a WordPress blog from one web host to another. As I wrote previously, I recently moved to a new web host. My strategy for migration is to bring up the blog on a subdomain for testing purposes. Once I have fully tested the site at its temporary location, I use DNS to point the active URL to the new site. Let’s walk through the steps: Read More »
Category: Technology HowTos
I previous blogged about my experience with the Wilson Electronics 801247 which is a short range wireless repeater. In my tests, the product worked as advertised, but the short range was somewhat frustrating. I was aware of the limited range upon initial purchase and continue to wonder whether a longer range option (like the 841262) would have been a better choice. However, I always come back to some key factors to justify my decision. Read More »
One of the challenges in today’s connected world is that we expect Internet and cellphone signals just about everywhere. However, many rural areas are lacking in coverage and I recently embarked on a project to provide wireless service where previously there was little to none.
I frequently visit a summer house on a lake that has minimal cell coverage. When walking outside, you are lucky to get one bar with AT&T while Verizon is a bit stronger, but still of questionable usability. My goal was to find a way to deliver consistent coverage to a desk in the house. Note that the objective was not to provide signal for the entire house, but simply to one location. (This is an important distinction.)
I researched many solutions. The first option was a femtocell. Carriers provide femtocells which provide cellular coverage in houses using voice over IP and existing Internet connections. The idea is a good one, but did not work in my case because the house did not have Internet access. Additionally, the carriers charge around $10 a month for this service which is ridiculous. Clearly, I needed an alternative approach.
The second choice, which I eventually went with, was a wireless repeater. These systems include an outside antenna, inside antenna and an amplifier. The outside antenna receives the carrier’s signal while the amplifier amplifies it and re-broadcasts it through the internal antenna inside the house. Thus, all cell phones inside the house work normally because they connect to what is effectively the outside signal amplified. There are a number of options to choose from including units from Wilson Electronics and Wi-Ex. In general, the reviews of both units were positive. Note that both companies also offer a range of accessories to improve signal quality and internal coverage area.
One of my colleagues is in the process of buying a Digital Rebel XT. This is my current favorite camera. I am sure that my colleague will ask about what format of picture to take. Well Steve, this is for you.
There are couple of different formats that you can take with the Digital Rebel XT and equivalent Digital SLR cameras. Their are typically two different formats that you can take, JPEG or RAW. Pretty much all cameras take JPEG and RAW is something quite different. Read on for more information.
JPEG — This is the standard format used by most digital cameras. JPEG is a lossy format meaning that when the picture is taken and the camera creates the JPEG some of the image data will irreparably lost. This may not seem like a big deal but if you then edit the JPEG and then re-save it, you lose more detail. Thus every time you edit a JPEG and re-save the image as a JPEG the quality will degrade.
There is a an upside to JPEG which is that it is the most commonly used and understood format and can be viewed in any standard web browser. The other element is that the resulting file sizes are smaller than alternatives because of the lossy nature of the algorithm.
Pros: Well understood and easily viewable, small file size
Cons: Reduced image quality, image degradation when editing
RAW — This format is a lower level format. When you a take a picture, the sensor in the camera captures the image on its sensor and the sensor outputs the image information. In a JPEG environment, that output is then processed in camera and turned into a JPEG. The RAW file contains all of the raw from the sensor with no processing. Thus it contains all of the possible image data from the sensor and is the highest resolution image possible from the sensor.
Also because the image has not been processed inside the camera, you can fix common image problems much more easily. An example of this is improper white balance which often occurs with digital cameras. The result is that the colors in a picture are skewed and you may see a bluish tint. This is easily fixed with RAW images and is more difficult to treat with JPEG.
The downside of RAW is that it is a proprietary format for each camera manufacturer. Thus if you shoot a RAW photo and send the RAW picture to someone, it is unlikely that person will be able to view the file. This means that some element of post-processing will be required with all RAW images to convert them to a more common image format such as JPEG.
Pros: Highest resolution image, improved image editing ability
Cons: Proprietary format, larger file size than JPEG
For the average photographer JPEG is adequate. However, if you are looking for the best image quality you should look at RAW. The Digital Rebel XT also has the ability to simultaneously take RAW and JPEG. This potentially overcomes the weeks of RAW, but results in more than 2x the required storage space for each picture which is problematic IMO.
I generally find shooting RAW to be the preferred method. I always take RAW and then perform a batch conversion of all RAW photos to JPEGs using Photoshop. This way I always have RAW and JPEG version of all pictures. I prefer to perform the conversion on my computer to minimize the amount of space required on my CF Card.
One common confusion relates to the variety of wireless networking options available and what the available options are. Pretty all of today’s wireless networking technologies are call 802.11x where x is a letter. The first six characters are not that important, and while the final letter is vitally important. The common technologies are 802.11A, 802.11B, 802.11G, 802.11N. The differences between these technologies are substantial.
First, you should be aware that all performance specifications provided by any of these standards are woefully overstated. Generally you will see substantially less bandwidth than promised by the standard. That said, here are the various standards and performance and radio frequency used:
- 802.11A – 54 Mb/sec, 5 GHz
- 802.11B – 11 Mb/sec, 2.4 GHz
- 802.11G – 54 Mb/sec, 2.4 GHz
- 802.11N – 540 Mb/sec, 2.4 or 5 GHz
The first thing that you should notice is the frequency differences between the standards. The first standards were A and B and they differed by both bandwidth and frequency. At the time, there was a question about which would prevail given the performance trade off. The G standard was released to solve the performance issues of B and leverage 2.4 GHz. The future standard is N which will bring an entirely new level of performance.
The other issue is that initially wireless cards only worked with A or G and not both. At the time there was a big question about which of the two technologies would prevail. Today there are cards that can do both frequencies, but it does not really matter since the 2.4 GHz technologies prevailed and A is seen infrequently.
As you look at the above performance numbers, you should always remember that they are overstated. I just ran some specific tests to illustrate. (Note all tests were running using the iPerf utility and each performance run was completed twice.)
|802.11G 20 Feet||
|802.11G 2 Feet||
|100 Base-T (wired||
As you can see, the wireless standards underperformed their specs. It is also interesting to compare them to wired which is spec’d at approximately 2x the performance of wireless. Yet even with that spec, we saw performance that was almost 5x faster than wireless. A very big difference.
What should I buy?
The industry has standardized on 2.4 GHz technologies and so must customers are buying 802.11G wireless devices today. This is the safe choice and is recommended.
Should I buy 802.11N since faster is usually better?
The clear answer here is no. The issue is that the N standard has not been ratified by the standards thus it is unclear if N products shipping today will be compatible with the final standard. Thus if you purchase a unit today you not only pay a premium, but you run the risk of your hardware becoming obsolete and not supporting the standard. This particularly important since in the future it is likely that this technology will be embedded in laptops.
If I have 802.11B is vitally important that I upgrade to G?
The typical answer is no unless you have very bandwidth intensive applications. I find B/G wireless to be more than adequate for every day use. The only issue is transferring large files. I sometimes copy photos across the network and notice a major performance degradation with wireless. (I use G and B would likely be even more painfully slow.) If you are working with large files over the network, you are better off sticking with wired than trying to use any of the wireless standards. I would consider upgrading to N once the standard is ratified as that technology looks like it will bring new levels of wireless performance that were previously unattainable.