Comments for Hacking With Gum

Comment on Hacking The Cenzic POV Fan by Michael

Michael — Thu, 22 Jul 2010 22:27:59 +0000

My work is now handing this out at trade shows, however at the cap, there is a small piece that removes to expose a small 5 pin port

http://i18.photobucket.com/albums/b109/ursusblue/IMAG0047.jpg

Comment on Hacking The Cenzic POV Fan by JJ

JJ — Thu, 10 Jun 2010 04:14:38 +0000

Thanks for the tutorial. It was a great starting point for hacking a similar product.

Comment on Hacking The Cenzic POV Fan by LED POV message fan hacking

LED POV message fan hacking — Sun, 09 May 2010 17:56:17 +0000

[...] Full story, tutorial and videos at http://hackingwithgum.com/2009/10/06/hacking-the-cenzic-pov-fan/ [...]

Comment on Installing OpenWRT On The GT-704WG by Bobby

Bobby — Tue, 20 Apr 2010 03:32:38 +0000

This command did the trick…

quote SETENV mtd5,0×90010000,0x903e0000

and this…

put “openwrt-ar7-squashfs.bin” “openwrt-ar7-squashfs.bin mtd5”

Comment on How Crystal Radios Really Work by Hacking With Gum » More About Crystal Radios

Hacking With Gum » More About Crystal Radios — Tue, 23 Mar 2010 00:51:41 +0000

[...] receiving a few questions about my previous post describing how crystal radios work, I’ve updated it with a lot more information including [...]

Comment on How Crystal Radios Really Work by Craig

Craig — Mon, 22 Mar 2010 14:26:35 +0000

Vaibhav,

Good question, and one which I did not address in the original article. For the answer, take a look at the image of the modulated vs. un-modulated signal.

Notice that the transmitter frequency is much higher than that of an audible frequency; in the above image, the audio tone imposed on the transmitter is spread out over eight cycles from the RF oscillator. This is important, because it allows variations in both the strength and the frequency of the audio tone to affect the modulated RF signal.

For example, if the audio tone were of a higher frequency, it might only cause an amplitude change in five of the oscillator’s cycles. In other words, the amplitude change in the transmitted signal will be shorter (amplitude changes will occur more frequency) or longer (amplitude changes will occur less frequently) depending on the frequency of the imposed audio tone. When these time variations in amplitude are converted back to an audio at the receiver, the audio wave will be respectively shorter or longer, thus re-producing the higher or lower frequency audio tone.

I’ve updated the article with this information, plus some corrections to other explanations. I will add some screen shots / videos of what the audio looks like on an oscilloscope later, which will hopefully make some of the explanations more clear.

Comment on How Crystal Radios Really Work by Vaibhav

Vaibhav — Sun, 21 Mar 2010 18:04:54 +0000

I have a doubt. If only the amplitude of the radio wave changes according to the
audio signal then how are the different frequencies in the human voice are reproduced at the speaker ? I would be grateful if you could answer this.

Comment on How Crystal Radios Really Work by Vaibhav

Vaibhav — Sun, 21 Mar 2010 15:44:44 +0000

You’re Great!! Such a good explanation and from the very core of things. I was
exhausted finding such an explanation on the web. Thanks a lot!!!

Comment on Just How Bad Is DTV? by Jack

Jack — Tue, 02 Mar 2010 16:17:42 +0000

DTV was tested using a yagi with a rotator. In order to get the number and
quality, you need to aim your antenna. Early front ends were very poor, and
yeilded miserable results. I had a wintv-d board running on redhat with
myth, and got a few miserable channels. the Tube network was a brightspot.
Later front ends are much better. Low cost/quality converter boxen are not
good, but (I’m an EE) I did design a miserably complex DTV antenna that
provided man channels and very good quality, especially the audio. Various
channels provide various quality transmissions.
I’m going to test the boxee, based on your appraisal. I have been running
GBPVR.
j

Comment on Installing OpenWRT On The GT-704WG by Jim

Jim — Wed, 27 Jan 2010 19:45:49 +0000

I was finally able to get OpenWRT flashed to my GT-704WG. From monitoring the serial console I was able to determine that the FTP transfer would start at a good speed, but then slow to a crawl. Sometimes it would transfer quite a bit before it slowed down (evidenced by many dots on the console showing progress of the flash process). By using “dm” to see how far the flash had made it before slowing down I was able to break up my transfer, starting the next stage after the last chunk that was already in flash. I created a new mtd6 variable using “setenv” and gave it a range beginning where the transfer had ended (rounded down to the prior block boundary, i.e. 0x90XX0000), then rebooted the router into adam2 and restarted the FTP connection. I would then put the remaining chuck of the openwrt image using ‘put openwrt-partx.bin “fs mtd6″‘, and see how far that made it. If I didn’t get at least 4 dots before it slowed down, I would reboot the router and try again. After many restarts and a total of 5 seperate uploads the last chunk made it to the router. I then cleaned up the mtd6 variable and rebooted the router, and OpenWRT came up.

Whew!