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Western Winter Teslathon 2011
Hello all,

I will be in attendance today at the Western Winter Teslathon 2011. Details here: http://www.drsparksite.com/teslathon2011.htm

Hope to see some of my fellow 4hvers at the thon, and looking forward to having a great time. There will also be a live feed at http://www.teslauniverse.com/stream.html. Check there, and http://www.teslauniverse.com/ for updates. I'll be posting a full report and lots of pictures soon! I'm also creating a thread for myself and others to blog about the thon, here:

Apologies for not getting a post up about this sooner, but Dr Spark asked me not to promote the event on 4hv.org.
Posted by Chris Russell on Saturday 05 March 2011 - 17:09:43 |Comments are turned off for this item |printer friendly create pdf of this news item
Site Restored from Backup
4hv.org was restored from a backup early this morning, due to the catastrophic failure of the server's primary hard drive. All data on the drive was lost. Unfortunately, as Murphy's Laws would seem to dictate, the hard drive failed while the backup was at its greatest possible age. This means the site has effectively reverted one week into the past.

I know this is frustrating for everyone. To ensure it cannot happen again, I've purchased an off-site nightly backup solution for 4hv.org. The expense is unfortunate, but I want to make sure this is the last time that something like this can happen.

If you've made any posts, created any threads, or sent any PMs over the last week, please feel free to recreate them.

If you stopped by Finn's Project Thread for Thumper, or even if you haven't, please drop by and let him know what you think of his project. He had collected a lot of nice praise and interest over the last week, and he's really earned it.

Finally, as an incentive to get things going again, I'd like to announce a small contest. Anyone who makes an interesting, thought-provoking, or high quality post over the next week will be entered into a drawing to win a 4hv.org t-shirt. The new shirt will incorporate elements of the upcoming site re-design, so the winner gets a first sneak-peek at more of the new site.
Posted by Chris Russell on Thursday 24 June 2010 - 19:47:49 |Comments are turned off for this item |printer friendly create pdf of this news item
Featured Project
This featured project goes out to a long-time 4hv.org members who has been pouring his heart and soul into an amazing project for over a year now. For those who haven't heard or seen, Finn Hammer, with help from Daniel Uhrenholt, has been doing some really incredible work on his latest coil, Thumper. His design is innovative to say the least, and he's really gone out of his way to not only create a work of art, but to document it thoroughly. He has posted images, videos, schematics, layouts, and extensive commentary. Here's just a small sample of images from his project thread:

The end result is quite possibly the world's largest DRSSTC coil, but that's not even the best part. It's the first DRSSTC coil with a primary tap adjustable at run time. That's right, it can be tuned in real-time:

This also marks the debut of the Predikter circuitry, which may just change the way a lot of people will be coiling in the years to come.

If you haven't had a chance to stop by the project thread, please do so and let Finn know what you think.

Update: Thumper has been featured on Hackaday. Congrats, Finn!
Posted by Chris Russell on Thursday 17 June 2010 - 01:05:14 |Comments are turned off for this item |printer friendly create pdf of this news item
Junk Box Update
The 4hv.org Community Junk Box is now ready! Visit http://wiki.4hv.org/index.php/4hv.org_Community_Junk_Box to see what's currently in the junk box, and learn how to participate.

As I'm sure most of you know, the 4hv.org Migratory Junk Box was lost along with most of its contents. The contents that weren't lost are apparently not going to be returned. I've been unable to even secure the return of the log book -- the person who currently has it has gone completely silent. We've made some changes to the way the junk box will be handled from here on out, to ensure a devastating loss like this cannot happen again. The junk box is now operated from a central location, saving postage and allowing the box's size to grow without restriction. It's just getting off the ground; I hope to add much more in the weeks and months ahead.

Here is a small sample of the junk available right now:

All are welcome to participate in the junk box. However, postage for those outside of North America may be high for larger items. If there is anyone who is interested in running a similar, centralized junk repository in another geographical region, please contact me. At the very least, it would be helpful to have additional repositories in the UK and EU. Our Australian members may also be able to generate enough interest to sustain a sizable junk box. If there's enough interest, I'm also looking into creating a "free stuff" board, so that members who'd like to give away items but don't want to participate in a junk box can also list what they have up for grabs. Again, please contact me if that's of interest -- the more feedback I receive, the better.
Posted by Chris Russell on Tuesday 11 May 2010 - 23:32:11 |Comments are turned off for this item |printer friendly create pdf of this news item
Featured Project
This featured project was called to my attention recently. IamSmooth put a lot of hard work into his Residential Grid Tied Wind Turbine. If you haven't seen it yet, take a look. Here's a preview:

Basically, the project consists of building a tower that is easy to raise and lower; building the generator; carving the blades to match the generator; running the power to the grid with the appropriate disconnects and power diversion features. Most people charge batteries with wind energy. This requires a compromise in power output. This is because wind energy goes up with the cube of speed. Low winds have little energy and high winds have enormous energy. One has to determine if they want to harness more consistent lower energy winds, or capture infrequent high energy winds. This is because the stator and blades need to be matched. A stator that can handle high power levels in high winds will stall out the blades in lower winds. If the blades are too large for the stator they will run away in high winds and fry the stator, or cause the turbine to self destruct from high RPM. I chose to feed power to the grid, allowing the inverter to draw off the appropriate amount of power at various wind speeds.


Posted by Chris Russell on Saturday 23 January 2010 - 20:55:14 |Comments are turned off for this item |printer friendly create pdf of this news item
Site Restored
Due to a server move, the site was accidentally reverted this morning to the way it appeared on Sunday afternoon, EST. I've now restored the missing posts from Monday. Any posts made in the early hours of today, Tuesday, have vanished, however. Please feel free to re-post anything that was missing.

Apologies for the interruption!
Posted by Chris Russell on Tuesday 10 November 2009 - 15:11:39 |Comments are turned off for this item |printer friendly create pdf of this news item
New Site, Featured Projects
This is just a quick update to let everyone know that due to faster-than-expected progress on the new site, featured projects will be on hold for a little while. However, just to keep things interesting, here's a classic project from early 2007 that you may have missed. Behold, Marko's DRSSTC v1.1:

Stay tuned for updates regarding the new site's rollout, and feel free to drop by Marko's thread.
Posted by Chris Russell on Sunday 11 October 2009 - 03:27:32 |Comments are turned off for this item |printer friendly create pdf of this news item
Registrations Re-Opened, Donations Address Changed
Hello all,

This is just a quick update to make everyone aware of what's going on with 4hv.org. There are some important things that I'd like to cover, so bear with me.

First, I apologize for getting behind on featured projects. I intend to restart this feature and keep it going every other Friday, starting August 7th. If you have any projects in mind, please feel free to drop me a PM or put a note in the suggestion box forum. Otherwise, I will continue to select ones that I think will be interesting to the most people.

Second, registrations have been closed for a while. This was partly due to some database tests I was performing with regards to getting existing user profiles integrated into the new site, and partly due to a large flood of users registering and not doing their part to follow the rules or keep the board clear of clutter. Registrations are now re-opened. If you've signed up and haven't received a verification email, please sign up again. Remember to observe the rules of the site; I don't want to have to step up to things like warnings and bans.

Third, the paypal address for donations has changed, both to keep things secure, and to keep things simpler. Donations will now go to **link**, the same address used for collecting webhosting payments. So, if you decide to make a donation, which I always appreciate, don't be alarmed if the address has changed. Note also that I currently bold and highlight the names of people who have donated recently. As always, if you'd like to donate in someone else's name, or would like your name displayed differently, send me a PM or include a note with the donation.

Fourth, I know times are tough. I am extremely grateful that even with the economic downturn, people have continued to donate when they are able. This really means a lot to me, and even though I know it isn't always visible, it makes a big difference in how much time I'm able to spend working on the site, even if it just means testing a script or a database link for the upcoming new site. As a way of saying thank you to everyone who has donated, if anyone whose name appears on the donation list would like a free @4hv.org email address for life, just let me know via PM and I will gladly set it up: email accounts can be accessed via IMAP/POP3 clients, or through a webmail interface.

Last, but not least, as many of you may be aware, I'm moving to northwestern Pennsylvania in August. I will no longer be living in Maine. Both money and time will be tight during the relocation, but I think everyone will be happy with the end result; starting in September, I'll be able to set aside much more time for 4hv.org. That means the long-awaited changes won't be far off, which is good news for everyone concerned. Fortunately, much of the behind-the-scenes work is complete. Exciting times lie ahead!

Posted by Chris Russell on Friday 31 July 2009 - 16:37:22 |Comments are turned off for this item |printer friendly create pdf of this news item
Featured Project
This week, we have another gem from the archives: WaveRider's low power 433 MHz BPSK data transmission system. WaveRider single-handedly designed and implemented a complete data transmission system, using a highly efficient method of modulation. He's also obviously gone through extreme pains to document the entire project thoroughly. This is a special treat for those of us who enjoy telecommunications as a hobby.

Feel free to stop by the thread and let WaveRider know what you think. And, as always, feel free to send me a PM with suggestions for next week's featured project.

WaveRider wrote ...

It's been a while since I have done a radio project. So, I thought I would experiment with data transmission using BPSK (Binary Phase Shift Keying) on the 433 MHz European ISM band.

What's so special about BPSK?
Most commercial systems seem to use frequency shift keying (FSK) or some form of on-off keying (OOK). I wanted to explore the possibilities of constructing a simple system for binary phase shift keying (BPSK). Binary phase shift keying is a form of modulation that is very "power efficient." This means that to achieve a certain bit error rate, the required signal to noise ratio is lower than that required by, e.g., frequency shift keying or on-off keying. BPSK (or QPSK) is often the modulation mode of choice for deep space probes where power consumption must be minimised and signal path losses are enormous. See graphic (taken from ) for comparison of error rates....

Why 433.92 MHz?
Besides sitting in the middle of the 433MHz European ISM (industrial, scientific and medical) band, it is also in the amateur 70cm band, so parts were easy to get and it can be modified to operate under amateur radio rules. For those in the US, I think this band also falls under Part 15 of FCC regulations for low-power communications devices. Also, the local oscillators use of-the-shelf SAW resonators instead of a PLL synthesizer. This simplifies the design greatly (at the expense of having to operate on a fixed frequency).

What will the transmitter power be?
Operating below 10mW in this band is permitted without a license. I plan to limit the emissions to somewhat less than this. Many garage door openers and automotive key fobs seem to operate in this band (altho' at much below this power level). Hopefully this won't mean intolerable interference in my experiments!

First step: The receiver design
Since the receiver design is more challenging than the transmitter, I started off there. Here is a block diagram of my proposed receiver.

I am basing the system around the Philips SA639 RF/IF subsystem chip, which is really designed for FSK systems, using a 10.7MHz IF. I managed to find a 500kHz bandwidth ceramic IF filter which should allow upwards of 384kbit/sec communications. BPSK demodulation is not as easy as FSK. Basically, we need to add a carrier regeneration system (a PLL) for demodulating the BPSK signal coherently. I do this with a simple "squaring loop" which doubles the IF carrier frequency. A NE564 PLL/VCO system is the heart of this.

The system
The received signal enters the system (as you would expect ) at the antenna input. A low noise amplifier, based on the BFR540 NPN transistor amplifies the antenna signal. I was a bit torn about whether to put the microstrip-based band/image-reject filter before the low noise amplifier. If I put the filter before the amplifier, the filter insertion loss will kill the noise figure of the system. However, putting the filter after the amplifier increases the chances of amplifier overload by strong out-of-band signals. I opted for putting the filter after the amplifier. I will rely on the antenna system to reduce out-of-band signals. Plus, the BFR540 amplifier as I have designed it should be able to withstand -20dBm on the input terminals without saturating.

The next stage is the downconverting mixer. I found a SAW resonator for 423.22MHz which is exactly 10.7MHz away from 433.92MHz. Hence, the local oscillator (based on a BFR92 transistor) fed to the mixer (part of the SA639 chip) downconverts perfectly to 10.7MHz. The ceramic IF filter passes a sharply defined 500kHz channel to the
first IF amp and limiter.

At this point, we split off the signal to the second mixer as well as a push-push active frequency doubler. The output of the doubler is passed through a 21.4MHz (second harmonic) bandpass filter (with a band-stop notch at 10.7MHz) to the PLL carrier regeneration circuit. The 21.4MHz signal is divided by 2 using a flip-flop. After a phase correction and level adjusting circuit, the regenerated carrier is fed to the final mixer, where it is mixed with the original amplitude limited IF signal. The output will be the original BPSK digital data signal (a 250kHz low-pass filter on the output remives any residual RF). A schmitt trigger squares up the output and produces a TTL compatible signal.

I am hoping for a BER at 384kbit/sec of under 10e-6 with -106dBm input at the antenna terminals (in the absence of other interfering transmitters).

Additional Pictures:

Posted by Chris Russell on Friday 29 May 2009 - 19:36:16 |Comments are turned off for this item |printer friendly create pdf of this news item
Featured Project
This week, some suggested that I dig something up from the older threads. So, I present to you, Dr. Spark's Small Bi-polar SSTC, a project from November of 2006. Dr. Spark's meticulous construction and careful attention to detail here does not disappoint. Please feel free to stop by the thread and let Dr. Spark know what you think. I believe some of you have now witnessed this coil operating in person.

If you have any feedback or suggestions for a project that you think deserves some recognition, please let me know. There are some really great current projects on the projects board, as well as quite a few on the following pages that have probably been overlooked.

Dr. Spark wrote ...

Good day great coilers,

I am now madly in love with solid state Bi_Polar coils. How little power they take and how fast they can respond is incredible ! Demo Lady Red for DC Cox this weekend and he was grinning big time.

I have 1.2 months left before the W.W.T. so thought I could squeeze one more project in for demo at the Thon. A small SSTC Bi-Polar with a surprise feature. So pics tonight are the starting project, coil will be all plexy with UV LED’s. Will update with pics but this will be the fastest built coil I have done in many, many years….. Have a goal to meet, so off the computer and back in the garage…



Posted by Chris Russell on Thursday 21 May 2009 - 15:18:12 |Comments are turned off for this item |printer friendly create pdf of this news item
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