Category: DIY

Cheap & Super-Portable Magnetic Loop antenna for 20-40 meters

On: By: K7DAA

Most of you know how much I enjoy playing with mag loops. I think I have something like 5 of them from different manufacturers, as well as my first one that I built myself. I showed a few photos of my homebrew baby on Ham Fun night a few months ago. My first contacts on 10 watts were to Maryland and then Hawaii a few minutes later on 17 meters from Morgan Hill. The really fun part about mag loops is that they don’t have to be hoisted high in the air. The two contacts I made that first day had the loop base about 2 feet above the grass in my front yard!

Just for fun, here’s a short clip of my Chameleon P-Loop in action. The station you’re hearing was 59 on 20 meters from Utah to Mississippi on my Yaesu FT-818 running 2.5 watts:
https://www.youtube.com/watch?v=mpmnCcrtKAo

Anyway, I know that some of you would like to try building a mag loop, but that it might be a little fiddly or require some tools you might not have. I just happened across this video from K6ARK, a SOTA guy that’s really into super-light, backpack-able radios and antennas, and he shows one that only weighs 8.5 ounces and can be put together easily without bending copper or aluminum tubing into a loop:

https://www.youtube.com/watch?v=Uz5ZKkxGDQ4

I thought this interesting (QRP power only) build might inspire you to try making one of your own. This one is not super-hard to make, doesn’t require any specialized tools, and packs away into a very small space. You might have to come up with some minor accommodations if you don’t have simple metal-working hand tools.

For example, the nice bracket that he made for the BNC connector could be replaced by simply cutting and stripping a piece of RG-174 or RG-58 coax and using a hose clamp to connect the coax braid to the ground point. Then solder or twist a simple 8 to 16 inch length of any kind of wire to the center conductor of the coax to make the “gamma” match. You can use either an alligator clip as shown, or even just another hose clamp to attach it to the main loop body. Just move the connection points around for the best SWR.

The little plastic switch box with the tuning capacitor is maybe a bit more of a challenge, but you can even substitute it with a 18-30 inch length of coax (for 20 meters), if you’re OK starting with just a single frequency/band. The capacitance between the shield and center conductor of the coax replaces the capacitors in the box. Just attach the shield to one side of the loop at the top, and the center conductor to the other side, leaving an insulator between the two ends of the loop. Something like a piece of scrap plastic, pvc, or even just a chunk cut from a soda pop bottle would work.

Leave the far end of the coax open, and measure your resonant frequency with a NanoVNA or some other wideband SWR meter. Snip the length of coax shorter a half-inch at a time until it resonates on the frequency you want. There–done!

I’m embedding a video by VK3YE showing this “coax-as-a-capacitor” method on his mag loop. You don’t necessarily have to make a big copper loop like this, or copy his tunable capacitor made of scrap pc board and a rubber band. You can just simply cut the open end of the coax a bit at a time as I mentioned.

The interesting thing about this antenna is that you can run a full 100 watts through it. Note just how low to the ground it is. That wasn’t just for the camera. I know some hams might think it’s impossible to get out with something this small and stealthy, but it really works!

As I’ve mentioned before, the only real downside is that mag loops are very narrow-banded, giving you only about 20-30 kHz of the band without retuning. Maybe the scrap pc board and rubber band kludge isn’t such a bad idea in that case. But…let’s say you’re really into FT8, or just want to join a daily net. This might just be your ticket! Stick it up in your attic and away you go…

Quick Links to Things We Covered on Tonight’s Net

On: By: K7DAA

Here are a few web URL’s to items we discussed on the 3/30/22 net:

Online tone generator–send DTMF over a radio or other device that doesn’t have a TouchTone pad:

https://onlinetonegenerator.com/dtmf.html


Source for SDR receivers and adapters for all sorts of uses:
https://www.sdr-kits.net/

Fully assembled little adapter boards for under $25 that you can add to your radio if it doesn’t have a built-in panadapter (waterfall) display). You would then connect this amplified IF output to an SDR dongle, add some free software on to your computer, and have a great display of what’s on the bands:

https://www.sdr-kits.net/Panoramic-Adaptor-Tap-Boards

Jack W6KRK and I bought these folding panels awhile back. Well-made and fold into something close to the size and weight of a laptop computer in a soft bag:

Amazon

George N6GWH bought these portable folding solar panels and likes them. They are about $50 less than the ones I bought, and have another 20W of power as well:

Amazon

Jehu Garcia’s YouTube page. He’s been one of my favorite instructors, as well as a source of parts, for building your own lithium batteries and battery packs. Be sure to also check out his VW Microbus that he converted to a full electric vehicle:

Jehu Garcia on YouTube

Will Prowse has a great YouTube channel that has very informative info on batteries and solar systems:

Will Prowse on YouTube

WebSDR: Listen to Repeaters in Salt Lake City, and Make Other Fun Radio Links

On: By: K7DAA

The Northern Utah WebSDR receiver system has a unique feature that allows you to listen in on local repeater activity in the Wasatch Front area of Utah. Like the other WebSDR receivers, it allows you to listen to activity on the 1.8 to 30 MHz HF bands, but they’ve added another remote receiver for local VHF/UHF activity. This receiver is located southeast of downtown Salt Lake City, on the face of the mountains, about 600 feet above the valley floor. For those of you familiar with the area, it is near the entrance to Parley’s Canyon, where I-80 and I-215 meet. To get from the SLC Airport to Park City, you go right past this area.

Someone has taken the time to mark all of the repeaters that can be heard on the tuning ruler, so all you have to do is click on one of the little brown flags to move from one repeater to another.

NOTE: Before you go any further, if you use the Chrome browser, or any based on Chrome, make sure you remember to click the colored box above and to the right of the tuning dial that says CHROME AUDIO START or you won’t hear anything on any of the WebSDR receivers. Also, please know that if you click these links from an Android or iOS device, you may get re-directed to a different receiver page that might not have the same capabilities. Nothing wrong with your stuff, just a limitation of the design of these awesome receivers. In fact, I sometimes listen to 75 or 40 meter nets with my iPhone, so it works, just a bit differently.

Here are a few web links you can copy/paste (or just bookmark this page) that you can save into your web browser:

This is the 146.62 repeater, the busiest in SLC, and links to one in Park City

Here is the 146.76 repeater, also quite busy, and is my “home” repeater, covering Salt Lake, Davis and Utah (where I am) counties area.

147.12 repeater near our TV towers on Farnsworth Peak (named after Philo Farnsworth, the actual inventor of television), southwest of SLC. This repeater is part of a wide area network of RF-linked repeaters up and down Utah. It is called the Intermountain Intertie system, rivaling the famous Cactus Net for sheer coverage. It also covers southern Idaho (Boise, Idaho Falls), parts of Wyoming, Montana, Yellowstone Park, Flagstaff and Phoenix, AZ, and Las Vegas. Lots of activity here as well. Unlike Cactus, all may use it without fees or membership. Read more about it here

By the way, many of the WebSDR receivers allow you to make your own weblink that you can save or bookmark. It allows you to instantly go to a particular WebSDR receiver, frequency and mode. You can see how I did this by examining the URL’s in the links above. Or, for example, if you like listening to the NoonTime Net on 40 meters from about 10 AM to 2 PM every day, your link would look like this one below. Go ahead and click on these examples if you’d like. I made sure they work:

http://websdr1.sdrutah.org:8901/index1a.html?tune=7284lsb

Note the data after the question mark. Just replace the frequency in kHz with whatever you want, and then add the mode, such as cw, usb, lsb, fm, or am. That’s all there is to it. If you want to listen using a different WebSDR receiver, just use its URL, and add the same frequency and mode data at the end. Here are two more examples of the NoonTime net again, but listening first from the KFS receiver near Pacifica, and right below it is the same net, listening from Phoenix.

http://69.27.184.62:8901/?tune=7284lsb

http://w7rna.com/?tune=7284lsb

Easy, right? Here’s another hint if you’d like to monitor several frequencies or repeaters at once. All you need to do is start one receiver session by clicking one of the above, then open a new browser instance or tab, then either click another link or paste one in, then go. Note that sometimes opening just a tab doesn’t give you audio from both receiver instances at the same time, depending on your browser. It worked OK for my Chrome browser, but your mileage may vary, etc.

OK, here is one last bonus link. If you would like to practice listening to CW, here is a link to 7047.5 kHz. It is the ARRL’s station W1AW. Every day it sends plain text from a recent issue of QST magazine at varying speeds. Very good practice, but don’t freak out if you happen to arrive while it’s sending at 35+ WPM! Yeah, I can’t copy most of that either. If you look at the web link, note that I inserted the frequency as 7046.75 kHz to get to 7047.5. I don’t know why, but on CW, it’s 750 Hz higher. Maybe a quirk. I dunno. I’ll come back and edit this if I figure out why.

There you go–you’ve got lots of cool receiver power all over the planet for the price of…nothing. Can’t beat that!

Son of “LancePod”

On: By: N6DZK

A couple years ago now, our local craft person, Jonathon, W6BID put together a club build for a tripod for the Wolf River Coils SB1000. The WRC TIA (Take It Along) kit t is an excellent, economical, portable, base loaded, vertical for pretty much any band. The community around this antenna has spawned all manner of modifications, whip options, radial options, and in this case a DIY tripod. The “out of the box” tripod, while mostly adequate, was tippy in windy conditions. Several of us have also adopted either the MFJ-1979 or Chameleon SS-17 stainless steel whips for better performance on the lower bands. The problem being with the longer, larger whip, the base needs more stability. Enter W6BID…

For a club meet, W6BID organized kits for us to assemble in a weekend garage project. Each of us taking turns drilling holes, and assembling our new WRC tripods. The original kit consisted of a piece of plate steel, a 3/8″ thru-hole, stainless steel antenna mount, 6 L brackets that Jonathon had welded to the plate ahead of time, 3 sections of 1/2″ steel square tubing, and some bolts here and there. All that and a quick coat of spray paint resulted in one stout tripod base. It has served us well!

But some issues crept in over time and after multiple uses. For starters, this thing is chonky! And secondarily, since the plate is steel, oxidation formed in between the plate and the stainless steel antenna mount creating resistance with the radials. This was finally identified as to why SWR readings were so out of whack from when the last time it was used.

So back in the shop it went for an update.

To address the chonk, I drilled holes down each of the 3 legs at 3/4″ intervals, and then turned the leg 90 degrees, and repeated at offset 3/4″ intervals. The end caps which had fallen off long ago, were replaced, but this time filled with hot glue before being re-attached. The base metal plate also had large holes drilled where I could safely remove material. This reduced the weight considerably, but still providing a solid stable base for the antenna.

To solve the oxidation issue I used a product called DeoxIT L260Cp that is a lithium grease that is infused with copper particles. Once the steel surface was cleaned back down to bare metal, a dap was applied to the surface and everything reassembled. Other changes made along the way…

  • Much experimentation with radials
    • Out of the box are 3 33′ radials made of black silicone coated wire.
      • Pro – Fairly quick to roll out.
      • Con – Performance was “Ok”.
    • Doubled to 6 33′ radials
      • Pro – Increased performance significantly
      • Con – When out in the field, you are taking up a circle nearly 70′ across. When camping this is valuable site space. The black wire was hard to see in the grass. Gopher/ground hogs actually tried to drag radials down one of their holes one night at a camp site.
    • Swapped out wire radials for 33′ tape measures
      • Pro – Fast to deploy. Easy to change the length if you want to “tune” the length for the band. Super fast to roll back up. Bright yellow tape is easy to see when deployed so people are less likely to walk through your radials.
      • Con – They rust. They are heavy. They are bulky.
    • Swapped out tape measures for 9 8′ radials constructed from a bright yellow silicone wire, and added quick disconnects.
      • Pro – Very fast to deploy. Bright yellow for visibility when camping or portable. Shorter length is way way less prone to tangling. Very lightweight. Compact. Works just as well as the 6 33′ radials.
      • Con – Not quite as efficient on 40 or 80 meters, but is still below 2:1.

Overall this has been a great project that has now gone through a couple iterations resulting in a very portable HF antenna solution that has performed exceptionally well. I just recently also picked up a padded tripod bag to store it in, and have a 50′ length of ABR Industies ABR240-UF (Ultra Flexible), with 5 ferrite beads shrink wrapped to the end. This entire solution can be in place in moments, is easy to tune, and with the larger SS17 whip is an efficient antenna system.

Side Projects – Air Quality Sensor

On: By: N6DZK

As we have all been acutely aware the past few weeks, the air quality in the Bay Area has been abysmal at times due to the various wildfires. The smoke blanketing the area was the product of 10,000 buildings, and the nearly 100 people that perished. This was not just ordinary wood fire smoke. It was full of all kinds of nasty particulates, carcinogens, and burned over areas that previously contained radioactive waste. Not good. You could go to sites like airnow.gov to see what is going on regionally. But what about in your area specifically? Or even in your home? There are actually very few sensors in South County. One solution is purpleair.com which is a network of personally or corporate sponsored sensors. But they are again, expensive, around $250 or more with shipping.

There are certain benefits to these more expensive sensors. They typically have additional data like temperature, barometric pressure, and humidity. They also use dual sensors in a parity configuration to help ensure accuracy. But what if you don’t really need all that?

So why not build your own? For about $70 and a couple hours of your time, you can assemble the components and get a fairly good quality particulate sensor up and running for your home or office. You can get output that looks similar to this:

Current N6DZK air quality: PM1.0: 3ug/m3, PM2.5: 6ug/m3, PM10: 9ug/m3, PM2.5 AQI index 25 (good)

Electric Imp is a company that enables IOT (Internet of Things). They are based here in the Bay Area, and naturally were also impacted by the air quality crisis at the time. I have built projects with their products before. They have proven to be extremely reliable, with one project having been online for several years now. Over on their blog, their CEO and co-founder, Hugo Fiennes, published a post on how to build your own AQI sensor using their card, and a little development breakout board, and a sensor from Amazon.  So, why not? I ordered up the parts, and 3 days later assembled them together, ran the provided code, and had a working sensor telling me how dirty my home office air really is (turns out it was actually not that bad).

Follow the directions on the blog post. It is not much to look at, but it does get the job done for a fraction of the cost of commercial versions. And you can then alter the web page to look like anything you wish. It is cloud hosted, no local server to run or deal with. And Electric Imp has proven to be a robust, reliable, long term solution.

There are some intermediary steps that someone new to Electric Imp will have to complete prior to getting your sensor online. You will need to create an account, download the app to your phone that programs the Imp device to get on your home WiFi, and a few other minor steps. But Imp devices are remarkably easy to get up and running.

Enjoy!

 

Category: DIY

Get on 40 meters SSB voice for $59

On: By: K7DAA

http://www.hfsigs.com
The BitX40 “you finish it” kit for $59

On tonight’s net, I mentioned that you can get on 40 meters for under $60, and without the need to be a virtuoso on the soldering iron or know tons about radios.  Say hello to the BitX40, an almost completely-finished 7 watt transceiver.  All you need to do is supply a box or case of some sort to put it in, a battery, and an antenna.  Everything else is already there for you.  To finish it, you solder on wires to a few controls, the battery (or 12 volt power supply), the antenna connector, and you’re ready to get on the air.

The BitX series of radios have an interesting back story.  A ham in India named Ashhar Farhan, VU2ESE, was concerned about how low the number of hams there were in his country, as well as other third-world countries.  After pondering this issue for a bit, he decided that one of the greatest problems a prospective ham faced was the high cost of even used ham equipment there.  He set out to make a 20 meter voice transceiver that used less than $20 in materials.  Thus was born the BitX20 about 10 years ago.  He cut costs in some very innovative ways.  For example, instead of the relatively-expensive ferrite toroids that are often used in radios, he substituted fiber or metal washers and wound his coils on them instead.  He decided to limit the power output to less than 10 watts so that a very common power MOSFET transistor could be used.  He also designed a novel main VFO tuning system made from a plastic drinking straw and a coil of wire.  I have one of these original (slightly improved) kits.

About 6 months ago, Ashar decided to try and help employ women in India to make a radio that might sell in higher quantities if he made it easier to build, but still supplied a quality product.  He created the BitX40, and founded a new small business to support it.  This is what I have in a my hands today, and I have to say that it is a very high-quality product, and he’s made it very easy to complete.

Gone is the drinking straw VFO, replaced by a very cool “Radiuino” board.  It is a very hackable Arduino that drives a 2-line LCD display and a DDS chip that outputs a highly-accurate, clean RF signal.  This one item alone increases the “fun factor” quite a bit, and helps contribute to a feeling that you are using a high-quality product that you yourself completed and mounted in your own custom housing.  Mount the display face and knobs to a plastic or metal ammo can and throw in a small battery pack, or put it in a cigar box (do they still have those?), or make your own custom wood enclosure.  It’s all up to you.

I suggest you give this cutie a try.  It’s not very intimidating, you’ll be very pleased with the results, and you’ll be helping some folks in India become more self-supporting.  You can find his website and ordering info here:  http://www.hfsigs.com/

 

 

Ham Radio 360 Podcast features local hams

On: By: K7DAA

George, KJ6VU, has a great podcast and accompanying web page with some interesting gear and DIY projects going on. They are presently doing a group build of a 1-30 MHz antenna analyzer based on the Arduino platform. Have a look and/or listen at www.hamradio360.com

 

I mentioned this on tonight’s tech net at 9 PM.  While you are perusing that website, have a look around at a few other very interesting things.  For instance, see George’s presentation from this year’s Dayton Hamvention, where he introduced the very handy portable end-fed antennas from his new company called PackTenna.

 

The presentation does a very good job of showing you how to wind some simple baluns (actually they are un-un’s) to get your 50 ohm feedline matched to the very high impedances of either a resonant, end-fed dipole, or a random-length end-fed antenna.  Or…you could buy one ready-made from PackTenna for $89.  If you go to www.packtenna.com and look around, be sure to read the QST magazine “test drive” of his antennas.  Highly recommended.

Amazon = Radio Shack + Frys + Halted + everyone else

On: By: K7DAA

This is probably old news for some of you, but if you miss having Radio Shack around, Amazon is the new Radio Shack, including all the other electronics parts stores rolled into one.

If you are a regular Amazon buyer, you’ve probably noticed that the Chinese “quick and dirty” module and parts suppliers that started out on eBay have all opened stores on Amazon now as well.  Being on Amazon generally means that they have to live up to a higher standard, if that kind of thing kept you from clicking the “Buy it Now!” button on eBay, but I’ve never gotten ripped off by any of them on eBay either.

Anyway, these guys offer just about anything imaginable for the Ham, DIY’er, or even an RF engineer like me.  I’m truly amazed at all the parts and pre-made modules you can buy from them.  If you have an Amazon Prime membership, which I highly recommend, you can buy just about anything and find it on your doorstep a day or two later, often without tax or shipping charges.

The prices are almost always way better than Radio Shack’s ever were.  Here’s just one example:  I needed to buy a 2.1 x 5.5 mm coaxial power plug–the type that you often see on the end of the “wall wart” power supplies.  Looking on Amazon, I had tons of choices, including whether or not I wanted some with wires already soldered on them and ready to go.  I finally chose these:

Coaxial power plugs with pigtails

So, for less than $.60 apiece, I got 10 plugs with wires already attached.  No tax charged, and free two-day shipping.  Can’t beat that!  Stock up for your next project!

 

Category: DIY

DIY Bluetooth Powered Speakers

On: By: K7DAA

Bluetooth BoomBox

 

There are dozens of videos on YouTube showing how to build your own Bluetooth speakers or boom boxes.  A number of them have ready-made Bluetooth radios and audio amps in common.  These Bluetooth and audio amp modules are interesting because they are quite cheap (most under $20–see this one on Amazon as an example), fully built and tested, and easy to interface to.  You could probably build one of these without even knowing how to solder!  It’s a simple matter to fit one of these small BT/amp boards into a box with speakers you’d mount yourself, or even retrofitted into an old plastic-fantastic boom box you have laying around, or maybe purchase for next-to-nothing at a Goodwill store.  All you really need is the housing and the pair of speakers.  Everything else can go!

For those of you that are old enough, remember the little transmitters you could buy or build that output a fairly unstable signal somewhere on the 88 to 108 MHz FM broadcast band?  They were often called FM or wireless mikes.  Plug one in, and tune in to it on of your FM radios you happened to have around the house.  They worked sort-of OK, but were never very good, and the 9V battery usually went dead in a few hours’ use.  In the Bay Area, you also had lots of trouble finding a fairly open radio channel to use.  The whole system was, as the British say, kind of fiddly.  It was more of a science experiment than anything else..

With Bluetooth, it’s so much easier, and the sound is just light-years ahead of the old analog FM stuff!  Most of us carry smart phones with Bluetooth built into them already, so it’s almost trivial to play the music or podcasts on your phone through your car stereo system or an inexpensive set of Bluetooth tabletop speakers.  Most of the cheaper BT speakers don’t have such great sound, though.  They tend to be small and tinny-sounding, but that’s not Bluetooth’s fault.

Anyway, here are several links to folks that have built their own Bluetooth speaker systems.  Maybe they’ll inspire you to roll your own:

DIY Bluetooth Speaker

Overnight Sensation Bluetooth Speakers

DIY Bluetooth Speaker: Super Easy

DIY V5.0 Boombox, Bluetooth

DIY How to Make the Best Bluetooth Speaker EVER!

 

Here’s an under-$20 BT dongle that plugs in to any 3.5 mm jack, giving you instant Bluetooth audio for a home stereo system or maybe even a car stereo.  This is sold by Parts Express (good company–lots of speakers and speaker kits as well), but there are many similar and cheaper units on Amazon as well:

Add Bluetooth to amplifiers, receivers, car stereos, computers, iPod docks

 

Emergency Power

On: By: N6DZK

2016-06-30 23.27.51The big one just hit. An accident just took out a utility pole. You forgot to pay your electric bill? All the things in your life that require go-go juice just became inert. But it doesn’t have to be that way. A few minutes on Amazon, and a couple trips to some of our favorite places to shop, and you can have plenty of electricity for lighting, communications, and charging your other devices. Read on to build one for yourself. Continue reading “Emergency Power” →

Category: DIY