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Messages - gil

Pages: 1 ... 172 173 [174]
2596
Net Activity / 6m AM.
« on: May 14, 2012, 04:07:58 PM »
Hello,

I really would like to organize a 6m AM Net. I have a Gonset Communicator III, and nobody to talk to once I get my license...

Gil.

2597
Technical Corner / Building a DC20B 20m CW Transceiver kit.
« on: May 14, 2012, 04:05:55 PM »
The DCxxB from qrpkits.com fits in a box the size of a pack of cigarettes and allows you to make contact all around the world! For $30, how can you go wrong... I thought the best emergency radio is the one you will take with you. The DC20B (there are other bands available) certainly fits that bill. I also ordered a frequency counter kit from N3ZI to help setting it up.

The circuit board it small: 3.5"x2.5". All the components come with the kit, with the exception of plugs needed to mount the PCB in a box. Actually, the kit was missing an integrated circuit socket (I found one at Radio Shack), and had two extra transistors..

It had been a long time (27 years) since I had finished electronics school. I had never soldered on a double-sided circuit board, but it turned out to be fairly easy. I just made sure I had a nice solder joint on both sides. The resistors went in first, then diodes, and so on, mounting the shortest components first, finishing with the talents. This way, you can use a piece of foam to press the components side onto it while you solder on the other side. This keeps the components near the board. One exception is the transistors. You don't want to overheat them, so it is better to mount them a little further out. The final output transistor is not put in until the kit is finished and tuned. Transmitting without a tuned antenna could destroy that component. Winding the coils was a pain. You need to make sure you count the turns carefully. One turn is every time the wire goes through the center. The parts are so small, I needed to wear reading glasses!

When all the components were in, I cut off the plug from old headphones and soldered them in. I also soldered a long wire as an antenna to test reception. It worked! I did hear faint morse code and SSB voices when tuning. The oscillator frequency however seems to be wrong: 14,063.2 Mhz instead of 14,060. I am not sure if there is a problem with the frequency counter, or I am that far off. The morse code keyed works too, so I have a working radio, except for the output frequency. I will need to find someone with an HF ham radio to check my tuning. I am investigating a way to fix the frequency problem and measure it accurately for sure. My progress will be posted here soon, as well as the mounting of the project in a box. Now I just need to learn morse code; darn, why didn't I think of that?

Update (May 27th): I think I am going to ditch the DC20B. I have a box for it, and should complete the build, but after that, it's going away. I can't get it on frequency, and I am not the only one... The Rock-Mite kit should arrive this week. I can't wait to build it. Look for the article!

Update (May 30th): Well, I gave it one last try.. Changed C36 to a 100pF, and C29 to 47pF. It worked! Now I get 14,059.72 on transmit. Receive goes from 14,060.16 to 14,060.32, a perfect 600Hz offset. The problem is the receiver, which has no selectivity. I receive Chinese, French and Spanish commercial radio stations, but little, faint CW signals. Maybe the problem comes from the wire I use as an antenna, which isn't tuned. I will try a tuned dipole during the day and see if I can get clear CW (morse code). I boxed up the DC20B in a nice Hammond cast aluminum box. I made a hole in the cover to tune CT1 and glued a piece of coax outer insulation so that I can't touch anything with my screwdriver upon insertion.. The box is a little big, but it looks good and as though it would survive being run over by a semi-truck.. I might make another hole for access to CT2 and add an RCA plug for a frequency counter (for tuning).

Still waiting for the Rock-Mite (shipped today).
Elecraft K1 arrives tomorrow (June 7th).


2598
CB / Galaxy DX 979 CB Radio Review.
« on: May 12, 2012, 11:18:32 AM »
I wanted a small CB radio with Single Side Band (SSB) that could be used for emergencies. The Galaxy DX 979 seemed to fit the bill. At a mere $140, there wasn't much of a risk. I knew I was getting a cheap radio and did not have high expectations, only a few requirements: Small size, SSB, and perfectly legal. That means forty channels, AM, USB, LSB modes, with 4W max on AM and 12W on SSB (PEP). Not much, but you would be surprised (I was tonight) at how far you can reach with just a few watts, as much power as a small bicycle light bulb!

Most people know the Citizen Band through movies like "Smokey and The Bandit," "Convoy" and others, mostly involving truckers. That is just one side of the coin. The other side are the operators trying to cover the greatest distance possible, and activity called "DX."

CB has a good thing going for itself right now, that is the peak of solar cycle 24. Propagation is going to be very good for probably another couple years. Radio waves in the 11m (27Mhz) band do bounce off the ionosphere when conditions are right. SSB being excellent at receiving weak signals, you have a very good chance to skip pretty far.

The Galaxy is cheaply made (compared to a Yaesu HAM radio of similar price). The buttons on the front panel are "chromed" plastic and look cheesy. The whole radio looks and feels cheap. I even had a very hard time putting in the mounting bracket screws. I had to tighten them with a pair of pliers and was lucky not to strip any thread. Looking inside the box gave me the same feeling. I like the big meter and the fact that you can dim the blue LEDs.

I connected the transceiver to my Solarcon Max2000, a 24ft. antenna mounted about 15ft off the ground, surrounded by trees, and an Astron power supply. Good thinking from Galaxy for putting the microphone plug on the front panel by the way, which I plugged in, then turned the volume knob to ON. It worked! I shouldn't be so negative, since I suspect that most CB radio manufacturers produce the same lever of "quality." I tuned to 38LSB and listened, playing with the clarifier whenever I heard someone calling DX.

[tip]The clarifier is the knob that turns the "Donald Duck" voices you hear on SSB into something you can understand.[/tip]

If you are a safe cracker by trade, you won't have any trouble with the clarifier on the 979. It takes that kind of finger dexterity to operate the darn thing. Before you have a caller "clarified," he is usually done talking.. Aggravating.. The range on the clarifier is too broad. My old President Jackson has a much better clarifier, but of course, that radio has acquired a quasi legendary status in the CB world. With a little practice, you get better at it, but geez!

Compared to HAM transceivers, CBs are noisy... I plan on replacing a few diodes with Schottky Barrier Diodes, and replace an RF amp transistor with a 2sc2999, High Gain, Low Noise model. The procedure is described here; part are on the way (about $1.60!).

I remembered that I should check the SWR before transmitting, which was a perfect opportunity to test the inboard SWR meter. I also plugged in a Workman el-cheapo meter on the antenna output. They did not agree with each other! The Galaxy SWR meter barely moved while the workman showed 1:1.8! I tuned the antenna and got down to 1.6 (probably all those trees..). Oh well. Just keep an eye on the SWR warning LED.. It works (I had a short in one plug); the SWR meter also jumped up. It might not be the most sensitive SWR meter, but it will let you know when you risk frying your final transistors.

It was getting late and the band was dying down when I heard "476" calling. He did not say where he was from, but I could hear him very well, good audio and a signal of 7. I expected him to be within fifty miles of me. I asked him about his location and he said "Jamaica!" I had a low signal but good audio (mike gain turned all the way up). Not bad for a $140 piece of gear. The antenna is everything, mind you, and the IMax2000 did it's part. The Galaxy... I hadn't wasted my money..

The Galaxy DX 979 won't win manufacturing quality contests. It does however work well. For the price, you can buy two and box one up in an ammo can for EMP protection. It is a small price for never being entirely cut off from the rest of the world.


2599
Antennas / Building a 2m Slim Jim Antenna.
« on: May 09, 2012, 03:41:07 PM »
I needed a better antenna for my Yaesu FT-270R. My requirements were to find a portable, efficient and easy to build design. The short rubber antenna works fine for me now, especially that I am not transmitting before getting my license. I do want more range however for emergency situations, in case local repeaters are down. My first thought was to make a Yagi-Uda directional antenna. They have a high gain but transmit in only one direction. While this can be an advantage, and I plan on getting one, my go-to antenna needs to be omnidirectional. I found the Slim Jim design to be my best option. It is easily made from soldered copper tubing. All you need is a couple of 5ft lengths of 1/2" tubing, 90deg corners, end caps and PVC Ts. I added an electrical junction box for the feed-point connector, but it might make it more difficult to attach the coax and tune the antenna.

Total length very-top to very-bottom is 58". Width center-to-center is 2". Gap is about 1-3/4". See the Ham-Universe articles (1 & 2) for exact measurements.

It is easy to calculate dimensions for other frequencies:

  • 3/4w : 8415/F-mhz.
  • 1/2w : 5610/F-mhz.
  • 1/4w : 2805/F-mhz.
  • Feed point : 10-20% of 1/4w.

The gap is taken off the 1/4 wave element...

Slim Jim Gap

The PVC Ts need to be reamed with a 5/8" drill bit so that the copper tubing can go through. I used a bit of WD40 to slide them down. Between the two Ts, I epoxied a 1" piece of 1/2" plastic tubing. There is one "H" PVC support assembly on the top portion and one on the lower portion, right next to the end cap.

Slim Jim Feed Point

I am not sure that using a plastic electrical junction box was a good idea for the feed point. Since I have not received my SO-239 socket yet, I must hold off on the electrical connection. My concern is that soldering will be difficult without burning the plastic box. I might have to use sheet-metal screws. Tunig might not be easy either, since the best SWR is obtained by moving the feed point up and down, between 3 and 4" from the very-bottom. Maybe I should have used PVC Ts, like for the two support "H" assemblies. They can be split in half, then the coax soldered after finding the best feed point. Once epoxied, it would look fine. I do like the look of my electrical box though, and if it works fine, I will be happy with the results.

Total building time was about an hour. Everything came from the hardware store, except the SO-239 connector. Soldering turned out to be pretty easy. I sanded the parts and used flux paste before heating up the assembled parts with a torch. Once the parts are hot enough, you put the solder on, which flows in the joint, following the flux. Cost could have been as low as $30, but I spent about twice that much, not counting tools (hacksaw, drill bit, epoxy, solder), which you might have already. If you are starting "empty handed," plan on $100. While it can cost more than a factory-made antenna, you get the satisfaction of building something yourself, which might be actually sturdier than a store-bought model.

Stay tuned for the finishing touches (painting), electrical connection and reception testing.

Thanks to Richard KE5FXU SK at hamuniverse.com for the article!

Update, April 11th:

Finally, I got my SO-239 plug. Drilling the PVC box was easy. I didn't even use my drill press. It only took me a few minutes by hand! Holes are one 5/8" in the middle, and four 1/8" around. I drilled in the middle of the lid, hoping I would have enough leeway to adjust the SWR by moving the contact in the box along the tube. First, as I suspected, I could not get the tube hot enough to solder the center of the coax to the copper tube using my 30w soldering iron. I solved the problem by heating up the tube with a Zippo under it while I soldered on top! It worked really well. I did the same to put soldering points in the box, every quarter inch or so. The zippo was placed an inch from the box. I was worried about melting it, but these electrical boxes are pretty heat-resistant. Sorry about picture quality:

Solder Points

It's a bit ugly, but inside the box anyway..

Feed Box

Reception works great. I was able to listen to a conversation tonight on a distant repeater that I simply could not hear with the HT rubber antenna. I get three extra signal bars with the Slim Jim. I got a cheap VHF/UHF digital SWR meter from Hong-Kong, which seems to work fine, but for the connectors which are of "N" type.

Digital SWR meter

Update, May 1st:

I painted the antenna sort of a flat olive-drab color for stealth. I can easily hoist it up a tree and it blends in very well. SWR varies from 2.4:1 on the lower part of the band, to 1.8:1 around 146Mhz, and remains around 1.4:1-1.5:1 from 146.5 up. I used a ferrite RF choke kit from Palomar Engineers (photo below), which got the SWR down to 1.36:1 around 147.5Mhz. I much prefer the ferrite choke to the coax balun type, which looks ugly and wastes cable.

Slim Jim Connection Box With Palomar Ferrite Choke
 
What I like the most about the Slim Jim is it's sturdiness and that given it's shape, you can hang it from anywhere, as long as you use an isolator to do so. When hanging it, I plug in an "L" shaped adaptor (photo above) to avoid bending the coax.
Update Oct 30, 2012: I have been using the antenna with my Icom IC-271A and it works great, even with the antenna set on the corner of my desk! I do plan on putting it outside on a pole or hoisted in a tree, but haven't had the time. I can hit distant repeaters on half-power (13W) with no problem and get good reports. What I like most about it is that I can take it with me anywhere and not worry about banging it or damaging it. It is easy to hoist up with a string or tape it to a pole. The SWR can probably be reduced by doing a better job at finding the sweet spot to attach the coax. It doesn't even look like an antenna to the untrained eye, which is always a plus.

2600
General Discussion / Frequency considerations and introduction.
« on: May 09, 2012, 03:09:47 PM »
I bought my first CB radio in 1984, a Lafayette LM300. I wish I still had it. Ten years later I got a President Jackson. After CB went ?down the drain,? I stopped all radio activity, until today.

I clearly remember twenty years ago, even five. I did not then have any of the concerns I have today. The future was bright with no clouds on the horizon. I don?t think the world is going to end this December twenty first, or next year for that matter. The Mayan who wrote his calendar must have been tired that night, and his wife was complaining about how much time he spent on it, so he probably just thought it went far enough and left it at that.. I am no doomsday preacher.
There is a certain unease among us however. The media is broadcasting multiple disaster and prepping shows. The economy isn?t going better. Five years ago, I had five ounces of gold, bought for less than $1500. Today, those coins would be worth close to $10,000. Only five years later! I am still hitting myself on the head for selling them before the increase. We may wonder why the value of the Dollar and the Euo have not gone down by a factor of six or seven. One only has to watch the news to start worrying.

I have always been the poster child for safety. Yet, I have enjoyed dangerous activities like ultralight flying, cave diving, motorcycle riding, parachute jumping and others, but always prepared and trained properly. The fact that I am here today has nothing to do with chance.

Being prepared for me means being prepared in all areas. I have seen people stocking up food while smoking two packs a day, shooters with dozens of guns who can't run to their 100yrd target, or people with a bunch of medical supplies but no water or any means to purify it. I have seen very few preppers with the means to communicate!

So, I am studying for my HAM licenses (yes, all of them), while enjoying my Galaxy DX 979 CB.

I have thought about HAM bands quite extensively and done a lot of research with an emphasis on emergency use.

For local communications, 2m seems the best option. I would also include a few FRS handhelds to keep track of family members and local friends in your neighborhood. I can't think of anything the 70cm band offers that 2m can't do.

A CB is a must as well, but it should include SSB, to take advantage of the 11m band's ability to skip on the ionosphere, thus allowing very long distances.

I am also intrigued by the 6m band, which at times behaves either like VHF or HF, depending on conditions. It also has the advantage of small antennas, with a half-wave being, well, 3m long! I found an old 6m Gonset Communicator III AM radio on Ebay for cheap, with a crystal for 50.4mhz. That set would probably survive an EMP sitting right in the open! If only someone else around had one...! 6m AM would make a great local frequency, if small and cheap handhelds were available. You would also get skip when the conditions are exceptionally good.

On HF, I am planning on sticking to 20m (14mhz). Lower than that and you run into antenna length problems. You can find cheap QRP kits for that band. I have ordered a small CW only transceiver kit for $30! How can you beat that? 20M is probably the most popular HAM band and would be great to listen to in a national emergency. Moreover, propagation is decent to great most of the time during the day and early evening hours.

In my opinion, better have a few radios for different bands rather than one that covers them all. I do want a Yaesu FT-817ND, but I will have a metal can with a 2m handheld, CB, 6m SSB, 20m QRP transceiver, a handful of FRS handhelds and a few accessories stored inside a cardboard box inside the can, for EMP and water protection. For a few hundred dollars, you can be well prepared as far as radios go. Much less than the cost of a good rifle ;-)

2601
General Discussion / PLEASE READ! Welcome to Radio Preppers.
« on: May 09, 2012, 02:11:40 PM »
Information is a vital commodity in a disaster situation. Whomever has any, in the absence of Internet, phone and power services will have a great advantage.

Radio Preppers aims to provide individuals interested in disaster preparedness with an independent tool for the exchange of information about emergency radio communications and preparations. Hopefully it will also help build a community of like-minded individuals who could contact and help each others in times of what is commonly known as 'SHTF' or 'TEOTWAWKI.' Like-minded here means self-sufficient, strong-willed and responsible people. Independent means regardless of nationality, race, gender, political and religious beliefs, as well as unrelated to any organizations. Whether you are a licensed HAM operator, CBer, or simply curious about radio preparedness doesn't matter here.

My motivation for creating this site came from my inability to find an emergency radio club that really wasn't related to some kind of organization, mostly governmental or politically affiliated. Survival is a personal, family or small community affair. I am always suspicious of organizations that plan on telling people what to do for their own good, or else... That said, anti-government rhetoric will not be accepted here. If you don't like your government, vote accordingly. There are plenty of other boads for political ranting. This one is not one of them.

Sign-up, it's free, and stop by once in a while. If you have anything to contribute, please do so! Topics will not necessarily be limited to radio but must be related to disaster preparedness. To avoid spamming, you do need to answer a couple radio related questions; nothing a quick Google search can't answer.

Rules are few: Be courteous. Although some civil political discussions are acceptable, try to avoid them; same goes for religion. Do not suggest anything against the law, or you will be immediately banned.

Please consider supporting this site after joining by subscribing at: Profile > Summary > Actions > Paid Subscriptions. You will get more privileges!

Note that members who do not participate at least once a year will be deleted.

Any suggestions would be appreciated. I hope you enjoy this forum and that it helps make you and your family safer.

Gil.

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