6 Meter Quad Turnstile Antenna

6M Quad Turnstile (2)After my less than successful attempts on 6 meters with my collinear array, I decided to try another design that I had been looking at for some time. A quad turnstile consists of two cubical quad loops oriented in a diamond configuration and angled 90 degrees apart from one another with both diamonds sharing the same top and bottom points. The advantage of this design over a single quad loop is that when phased 1/4 wavelength (90 degrees) apart the combination of the two antennas creates an omnidirectional radiation pattern. This type of antenna can also be made from two crossed dipoles, however, using full wave loops instead of half wave dipoles provides about 1 dB additional gain at low elevation angles (there is a great article about building a 6 meter quad turnstile written by L. B. Cebik, W4RNL in the May 2002 QST magazine that goes into further detail about the performance and advantages of this antenna design).

Another advantage, from a construction perspective, is that the spreaders required for a dipole turnstile would have to be 10 feet across. The spreaders for quads only need to be 7 feet across meaning that the use of lightweight pvc is that much more practical. The quad configuration is also perfect for being suspended by a push up fiberglass mast since the antenna is very light weight and virtually all of the loads are directed vertically down the center of the antenna which is also the center of the mast. This results in very little flexing and stress on the light duty fiberglass section at the top of the mast. I built my antenna using the Max Gain Systems MK-6-Standard fiberglass mast which stands 32 feet tall when fully extended.

From previous experiments with 6 meter loops I have found that 20 feet of insulated 14 AWG wire is resonant at the bottom of the 6 meter band (just above 50 MHz) where the SSB activity is concentrated.

6M Quad Turnstile (5)6M Quad Turnstile (6)The feed point is the most complex component in the entire antenna. It consists of a piece of 1/4″ thick Lexan with three SO-239 connectors (one for the feedline and one for each end of the phasing line) and four #10-32 stainless bolts (one for each loop end) mounted to it. The SO-239s and bolts are then wired together such that the feedline is wired directly to one loop and one end of the phasing line and the other end of the phasing line feeds the second loop. I used red and yellow electrical tape to mark which bolts attach to which loop. I also notched the Lexan sheet to fit around the mast so that I could wire tie it in place.

6M Quad Turnstile (7)6M Quad Turnstile (8)The phasing line is made using RG-63 coax which has an impedance of 125 Ohms. This is required because the feedpoint impedance of each of the loops is also about 125 Ohms. When fed together via the phasing line the final antenna impedance is approximately 62 Ohms which matches well with the standard 50 Ohm feedline (for this antenna I used a run of 100 feet of LMR400 coax). I purchased my RG-63 coax from The Wireman. The phasing line needs to be 1/4 wavelength long at the bottom of the 6 meter band. To calculate this you can use the formula (246/frequency) = quarter wavelength in feet. Therefore 246/50.5 = 4.871 feet = 58.46 inches. Next we take into account the velocity factor of the RG-63 coax, in this case 84%. Therefore 58.46*0.84 = 49.1 inches which is the length that the phasing light should be including the connectors on each end.

6M Quad Turnstile (11)6M Quad Turnstile (10)The PVC spreaders are made using 3/4″ PVC conduit glued into a 4-way junction box. By drilling a 3/4″ hole in the center of the junction box it allows the spreader assembly to slide down the top mast section and rest on top of the 1″ section of the mast. This is left to float in place and is not attached to the mast in any other way.

6M Quad Turnstile (9)The key to the construction of my version of a quad turnstile is that the entire antenna hangs from the top of the mast. To accomplish this I used a 1/2″ PVC cross with a nylon bolt running through the center. The bolt slides in the end of the 3/4″ fiberglass mast section and prevents the PVC cross from sliding off the top of the mast. I then fed the antenna wires through the cross such that the wires intersect at 90 degree angles. This method serves to secure the wires to the peak of the mast as 6M Quad Turnstile (12)well as providing some strain relief for the antenna wires. I then splayed out the wires and ran them through notches cut at the end of the PVC spreaders. I then centered the wires relative to the top of the mast and taped the wires to the end of the spreaders to keep them in place until they are attached to the feed point. The wires were then attached to the feedpoint using ring terminals that were soldered to the ends of the wires. The ring terminals make it easy to connect the wires to the bolts mounted on the feedpoint.

6M Quad Turnstile (3)6M Quad Turnstile (1)To erect the antenna I first raised the top 3/4″ section of the mast until the top wires became taught. This only requires about 3 feet of the top section to be extended such that the spreader assembly is not lifted off of the lower mast section. I then locked the top mast section in place. Next I raised the 1″ section of mast until the lower wires were taught and secured the feedpoint in place with a wire tie and taped the feed line and phasing line to the mast for strain relief. Then I continued raising each mast section until the mast was completely raised, resulting in a peak height of nearly 30 feet. I then finished guying the mast. For this antenna I only guyed the mast at 3 intervals, the bottom, the middle, and the top since the antenna is not heavy and is very evenly loaded on the mast. Three guy lines per 6M Quad Turnstile (4)interval were used made from UV resistant rope anchored using 10″ spiral ground anchors. This resulted in a very stable mast and the antenna that has held up well, even on breezy days. A tautline hitch is a great knot to know for tensioning guy ropes for masts as well as tents when camping.

After erecting the antenna I checked the SWR and found it to be 1:1 at the bottom of the 6 meter band. I also found that the 2:1 SWR bandwidth was quite large and easily covered the SSB portion of the band. I also noticed that a nearby 6 meter beacon station that was typically an S3 on my collinear array was now an S7 on my quad turnstile, which is a huge improvement.

The following day after getting the antenna on the air there was sporadic E band opening in North America and I was able to hear several stations. During this opening I worked my first 6 meter contacts, receiving good reports from stations in Oklahoma, Arkansas, Alabama, Tennessee, and Manitoba. Not too bad for 100W into an omnidirectional antenna in western Pennsylvania.

I also worked about four hours of the June 2016 ARRL VHF Contest and made 20 contacts with stations in 14 grid squares. Like a lot of antenna systems, this one allowed me to contact most of the stations that I was able to hear. I have, however, gained an appreciation for why most people use directional antennas for VHF work. While the extra gain directional antennas provide would definitely be a positive, I can see now how favoring one direction over another can be especially advantageous on 6 meters. More than once I could hear multiple strong stations on the same frequency and with a directional antenna I could have significantly nulled out one of those stations in order to make it easier to hear and work one station at a time. Another advantage would be the ability to focus your signal in the direction in which the band is open, instead of broadcasting in all directions.

With all of that said I am very pleased with how this antenna project worked out. This design is an inexpensive and effective way to get on 6 meters and make contacts which was my goal in the first place. It is also a good all around lesson in antenna design, construction, and phasing lines.

mcHF SDR Transceiver Kit

A huge part of the history of ham radio involves people building their own equipment. In fact that is how things started since at the beginnings of radio no commercial hardware was available. Over the years various companies and organizations have sold transceiver kits, but in recent years most of these have consisted of basic morse code only or single frequency single side band devices intended for digital communications. With the increased development of software defined radio (SDR), however, this is changing. Earlier this year I came across the mcHF SDR transceiver project and decided to purchase one of the kits. Unlike other basic transceiver kits the mcHF is a full featured radio with 80M-10M coverage, multi-mode support, variable bandwidth filtering, DSP (noise reduction, notch filtering, etc.), sound card interface, rig control, and band scope / waterfall capability. Not bad for a $388 kit.

mcHF (1)mcHF (2)The project was originated by Chris, M0NKA in the UK about 2 years ago and the design has gone through a number of revisions resulting in the current v0.5, which is what I purchased. One of the major reasons I was willing to undertake this project was that the kit offered by Chris includes the circuit boards already populated with about 95% of the surface-mount parts, including all of the tricky to solder chips and super tiny resistors and capacitors. The only remaining parts to install are larger, and therefore easier to solder, surface-mount parts and standard through-hole components. The builder also has to hand wind several toroid inductors and transformers. You also have to provide your own final power amplifier MOSFETs, shielding plate between the boards, and case for the radio. These requirements go along with the way this kit is sold, which is to say bare bones. The kit includes zero instructions. The builder is responsible for sorting through the mcHF downloads page, the mcHF Yahoo group, and the Github Wiki to find the details regarding how to wind the toroids and transformers as well as details on any recommended mods and instructions for how to use the radio.

Since this project is open source, both the hardware and firmware have undergone considerable development. In fact, from the time I started building the board to when when I completed the project a large firmware update was released which revised the main screen and menu layout as well as added a number of fixes and features, including the ability to control the transceiver via the usb port and detect the transceiver as a sound card device with a PC.

mcHF (3)The mcHF consists of two circuit boards called the UI board and the RF board. I built the UI board first, and then built the power supply section of the RF board so that I could power up and test the UI board. Chris has a very helpful document on the mcHF webpage that steps through the process of installing the bootloader and uploading firmware to the CPU on the UI board. So after only about 4 hours of work I had a functional UI board.

mcHF (7)Next I completed the remainder of the RF board, which was fairly time consuming since winding toroids and transformers is a tedious operation. Documentation exists for how to wind the transformers, however, the only information regarding the toroids is on the RF board schematic which details how many windings each core requires. Extra attention should be paid to stripping the enamel wire used for the toroids and transformers. Even though I diligently sanded off the outer coating and thought that I had solid solder connections to the board, I did not do a good enough job on two of the toroids which prevented the radio’s operation on the 80M band. After desoldering and re-sanding the wires I achieved a good electrical connection and consequently 80M functionality.

mcHF (10)mcHF (11)This portion of kit construction is somewhat confusing because there are a ton of possible mods for the various transformers that can improve performance of the final power amplifier. I decided to build mine in the default configuration which results in a solid 5W output on 80M-12M and about 4W on 10M. When modified, users report 10 or more watts of power output. The only modification I made was with regard to the SWR bridge where RG-178 coax is used in place of a single winding of enamel wire. Construction details for many of these mods are available in a document on the Yahoo group produced by Clint, KA7OEI who has done considerable work on both the hardware and software of the mcHF.

mcHF (18)Although not technically a mod, I did add a resistor that is regarded as “optional” on the UI board schematic. This resistor provides power for when an electret microphone is used. Since I would be modifying an Icom HM-36 I had lying around to work with the mcHF, I needed to install this resistor in order for the microphone to function. For this I used a standard 1/4W resistor since I had on of the correct value in my junk box and just soldered it to the surface mount pads. In order to avoid shorting with nearby components I carefully shaped the resistor’s leads and used electrical tape to insulate between the parts.

mcHF (5)mcHF (6)After completing construction of the boards, I turned my attention to completing the radio as a whole. The first step of this was to construct the shield plate between the boards. For this I used a thin mcHF (12)sheet of aluminum that I hand cut, drilled and nibbled according to a pattern available on the mcHF website. I then test fit and assembled the board and shield sandwich to check for proper clearance. When I was satisfied I completed the assembly using 5mm standoffs.

mcHF (19)mcHF (17)If you look around the web you will see a lot of people who have built the mcHF using the same case. This case is sold by Artur, SP3OSJ from Poland for about $63. If you email him at asnieg@epf.pl he will give you the details for how to order. The case comes with all of the knobs and buttons as well as a small piece of acrylic to protect the LCD display. The front panel is pre-machined, however, the endplates are left to the builder to complete. I also had to file some of the button holes to allow smooth operation and I had to sand the acrylic to fit the opening in the case.

mcHF (8)mcHF (9)Since the case serves as the heatsink for the power supply circuitry as well as the final amplifier transistors, a good mechanical connection between the components and the case is necessary. To mcHF (13)mcHF (14)accomplish this I soldered brass #4-40 nuts to the heatsink fin on power supply and amplifier components. I then drilled holes in the case to match where these nuts line up when the case is mcHF (15)assembled. When bolts are inserted and tightened, the electrical components are pulled tight to the wall of the case. In order to achieve a properly aligned connection, I had to grind away a small amount of material where the final amp transistors contact the case (note the hole I drilled in the wrong location due to my inability to follow the old rule of measure twice drill once). The last step in construction was labeling the buttons and ports, which I did using vinyl self-adhesive labels and my laser printer.

The final adjustment before testing the transmitter involves setting the proper bias for the final amplifier and then setting the transmitter gain for each band of operation. Documentation for these adjustments is on the Github Wiki. Basically you set the bias in one of the mcHF’s menu settings while keying the transmitter with no audio present as you watch the current draw of the radio. The transmitter gain is also a menu setting. These adjustments can be accomplished with an ammeter and a RF power meter.

mcHF (16)Finally, after probably 20 hours of work I put my mcHF on the air. After adjusting my microphone gain I made a contact on 40M SSB. I then plugged the transceiver into my PC and fired up WJST-X. Following the guide on the Github Wiki I was able to get rig control working and made a half dozen contacts using JT65 on the 30M band using nothing but the mcHF and my laptop. The next day I checked into my local 10M SSB net and received good signal and audio reports from the other regulars who are familiar with my voice.

Overall I have to say that I am incredibly happy with the mcHF kit. It has been a great learning experience and the radio itself is an incredibly capable and configurable device that offers a lot of bang for your buck. I plan to use the mcHF quite a bit in the future and look forward to any future firmware updates. I also hope that this kit leads to other similar kits in the future that can help get more hams back to building equipment.

I highly recommend this kit for anyone with some electronics experience. While the documentation has not been collected into one easily digestible package, the kit itself is actually very straightforward to put together and I was able to get it on the air with only a cheap multi-meter and an RF power meter. It is also an incredible bargain for such full featured radio; I spent under $500 total for the kit, case and other ancillary parts (not including the microphone) which is not bad at all when you compare this to what is available commercially.

Slim Jim Antennas

2 Meter Slimjim (2)2 Meter Slimjim (1)I am a big fan of the J-Pole antenna style and have built a few of them in the past (see here and here). Electrically the J-Pole is a half wavelength antenna that is end-fed by a quarter wavelength stub to achieve a feed point impedance of 50 Ohms. The Slim Jim is very similar except that there are two half wavelength segments with the second folded next to the first. This arrangement makes them ideal to be constructed from 450 Ohm ladder line. This also allows them to be incredibly compact and portable since they can be rolled up very easily.

2 Meter Slimjim (4)2 Meter Slimjim (3)I found a very useful calculator that gives you all of the dimensions needed to build a Slim Jim or a J-Pole from ladder line (you will have to convert from metric to imperial units yourself). Using this calculator set for 146 MHz (the middle of the 2 meter band), I assumed my 450 Ohm ladder line had a velocity factor of 0.91 and cut it to a length of 56 inches (not including the 0.5 inch on each end to be stripped and soldered together). I then cut the half wave radiator 36.75 inches from the top and the quarter wave matching section 18.375 inches from the bottom. This left a gap of 0.8 inches between the two. The 50 Ohm feed point was calculated to be about 1.8 inches from the bottom, however, using my antenna analyzer I found the the feed point should be 2.1875 inches from the bottom. With a piece of RG-8X feedline soldered at the feed point this antenna has an SWR under 2:1 across the entire 2 meter band. To complete the antenna I drilled a 0.25 inch hole at the top so that the antenna can more easily be hung from a mast or a tree or clipped to a wall if used as an indoor antenna.

This type of antenna is a very economical way to build a VHF or UHF antenna. It also has a considerable amount of gain compared to a standard quarter wavelength vertical and is just as easy to build and transport.

6 Meter Collinear Antenna

6 Meter CollinearI have been wanting to get on the 6 meter ham band for some time now, but I just never got around to it. Most people say that you should use a beam antenna for 6 meters, but I like to keep my antennas simple and cheap by using wire as the basis for everything. As part of my search for a good wire antenna for 6 meters I came across an article in QST from February 1997 called “Wire Gain Antennas for 6 Meters”. The article describes three different designs: the long-wire, the collinear array, and the Sterba curtain. After reading the article I decided I wanted to try building the collinear antenna because it has more gain than the long-wire while also being smaller and easier to build than the curtain.

6 Meter Collinear Antenna-4KI built my collinear array in the same manner as the article, using insulated 14 AWG wire and 450 Ohm ladder line. I cut mine for 50.1 MHz. For the 4:1 balun at the feed point, I used the balun I built recently. To securely mount the balun I used a DX Engineering Wire Antenna Balun Mounting Bracket. These brackets are specifically designed to mount to the type of enclosure I used for my balun, and they make a perfect feed point for a wire antenna. One of the benefits of 6 meter antenna experimentation is that you don’t need a lot of materials or space. This antenna when finished is only about 38 feet long and requires less than 15 feet of ladder line.

After getting the antenna in the air and the coax terminated I did some testing with my transceiver and the antenna exhibits around a 1.3:1 SWR at the design frequency and easily stays under 2:1 from 50-51 MHz. In theory this antenna should have a gain of 4-5dB over a dipole, so I am really looking forward to my first band opening to give this thing a try.

Update:

After playing with this antenna during a few band openings and not hearing many stations I realized that while this antenna is of a good design, it would work best when at a greater height than I can achieve at my location. It would also help if I was able to erect a couple of them to be able to shift the directivity of the array. Not being able to accomplish either of these goals I decided to take down the array and move on to another antenna design for 6 meters that better fits my operating capabilities and the size of my property.

Baluns & Ununs

Anyone building antennas will come across designs that either recommend or require the use of a balun or unun. The design and construction of these components can get quite complex and are beyond the scope of this blog and my own knowledge. In short these devices act as impedance transformers from balanced loads to unbalanced loads (balun) or from unbalanced loads to unbalanced loads (unun). They can also be used as a common mode choke to eliminate any RF on a coax feed line’s shield. That said, it is actually quite easy to construct your own baluns and ununs and to learn something in the process. You can also save a considerable amount of money.

1-1 Balun (2)1-1 Balun (1)Amidon sells a good starter kit for building baluns and ununs. It includes everything you need including a book with dozens of designs with various impedance transforming characteristics. 1-1 Balun (6)1-1 Balun (3)I used this kit to make a 1:1 balun. Since the kit uses 14AWG wire, it should be capable of handling 2KW of power continuously. This is overkill for me since I will never be putting more than 100W through the balun. The 1:1 balun is essentially a choke that blocks current flow on the shield of the coax feed line. It is constructed using 10 bifilar wraps on the toroid core using approximately 4 feet of wire.

For other projects I decided to use the same FT-240-K core with 18AWG wire covered in 16AWG PTFE insulation. While the 18AWG has less power handling capability, it should be more than adequate for 100W usage as well as being cheaper and easier to work with.

4-1 Balun (2)4-1 Balun (1)The first balun I made using these materials was a 4:1 current balun. This balun is intended to transform a 200 Ohm load for use with a 50 Ohm coax feed line. This type of balun is commonly used in 4-1 Balun (3)Off-Center-Fed dipole antennas because the feed-point is placed at the location on the antenna where the impedance is approximately 200 Ohms on multiple bands. I intend to use this balun as part of a 6 meter collinear antenna that I am building. The balun is constructed using two sets of 8 bifilar wraps on the toroid using approximately 8 feet of wire. Each pair of windings is then wired in series with the other pair. This design can be thought of as two 1:1 baluns wired in series and in fact an alternate design of this balun uses two separate 1:1 balun cores wired in series to achieve the same affect.

9-1 Unun (2)9-1 Unun (1)Next I made a 9:1 unun for use with an end-fed antenna I am building. End-fed antennas exhibit very large impedances and consequently require considerable impedance transformation to 9-1 Unun (3)get the feed point within the range of an antenna tuner. Unlike a dipole, an end-fed antenna is unbalanced and therefore an unun is used instead of a balun. This design uses 8 trifilar wraps on the toroid using approximately 6 feet of wire. Each wrap is then wired in series to create the desired impedance transformation.

1-1 Line Isolator (2)1-1 Line Isolator (1)I also made another 1:1 balun. The main difference here is that I constructed it using two SO-239 connectors because I intend it to act as a coaxial feed line isolator. My plan is to use this in conjunction 1-1 Line Isolator (3)1-1 Line Isolator (4)with the 9:1 unun as part of my end-fed antenna project. The idea here is that a section of coax from the 9:1 unun acts as the counterpoise for the end-fed antenna and the line isolator is used to choke the RF current in the shield of the coax and allow the remainder of the feed line to continue to the antenna tuner without risk of radiating RF.

For all of these projects you can see that I used colored electrical tape to mark the various windings. This is essential to keeping track of the wiring and assuring that the windings are wired together correctly. For all of these I also used standard NEMA 4X 4″x4″x2″ plastic electrical boxes which are cheap and commonly available. I also used 10-32 stainless steel hardware for the antenna connections and silver-teflon SO-239 connectors.

Ham Radio EMCOMM Go Kit – Laptop & Software

EMCOMM Laptop (1)This is the fifth part of my emergency communications system. The system I am building is intended to be modular. When complete I will have a VHF/UHF station, an HF station, a battery box, an antenna system, and a computer system.

I had a few key priorities for an EMCOMM laptop: EMCOMM Laptop (4)adequate performance, decent screen size, full size keyboard, lightweight, good battery life, low price. After looking around at the laptops available I decided to get the Acer Cloudbook 431. While this laptop is by no means a speed demon, its processor has no problem running EMCOMM software (especially after ditching Windows 10 for Linux Mint). It is also a very solidly built machine with a good keyboard and trackpad all for the low price of $230. To top it off it sports 12 hour battery life.

EMCOMM Laptop (3)Acer Aspire One Cloudbook 431 Specs

  • CPU – Intel Celeron N3050 (Dual Core, 1.6 GHz)
  • RAM – 2GB
  • SSD – 64GB
  • Display – 14″ (1366 x 768)
  • Wireless – Wifi, Bluetooth
  • EMCOMM Laptop (2)Ports – USB 3.0, USB 2.0, HDMI, Audio
  • SD Card Reader, Webcam, Microphone
  • Battery – 4780mAh
  • Weight – 3.53 lb

Software

After using the Cloudbook 431 for a few weeks it became apparent how much Windows 10 was bogging down due to the low system specs. At idle Windows used almost half of the system’s RAM. With a little research I found the following tutorials that provide some good instructions for installing Linux and tips to get all the hardware working properly.

With Linux Mint installed the Cloudbook 431 is like a completely different computer. It boots faster, loads software faster, and is just a much more responsive system in general. Multitasking with Windows 10 was very slow, but with Linux Mint it works perfectly fine.

In my area, digital EMCOMM communications centers around NBEMS which uses the W1HKJ software package (FLDIGI, FLMSG, FLWRAP, FLAMP, etc.). This software works just as well in Linux as it does in Windows and the SignaLink USB interface I use is detected perfectly in Linux Mint as well.

Power Usage

EMCOMM Laptop (5)The processor in the Cloudbook 431 is not particularly fast, however, it balances that by sipping electricity as shown in the power readings below.

  • Idle Maximum Brightness – 5W
  • Idle Minimum Brightness – 4W
  • FLDIGI, FLMSG, FLAMP, File Browser Open, Maximum Brightness – 7W
  • FLDIGI, FLMSG, FLAMP, File Browser Open, Minimum Brightness – 5W
  • Charging Battery – 33W

While this extremely low power usage provides the benefit of great battery life it also means that the Cloudbook 431 can run for hours and hours on an external battery pack like the Energizer XP18000 or the Intocircuit 32000mAh battery pack. Starting with a fully charged laptop and battery pack this laptop could easily run for over 24 hours without needing to plug into 120V. Being low power also means that the system doesn’t get hot, there’s not even a fan for the processor.

Nitpicks

For such a cheap laptop I really don’t have any major complaints because you can’t expect too much for $230. That said, the screen on the Cloudbook 431 has poor contrast, color and viewing angles. It is perfectly usable, but it just doesn’t look very good. Other than that I have to say that this laptop is a fantastic value and very well made for such a low price point.

Ham Radio EMCOMM Go Kit – Antennas

This is the fourth part of my emergency communications system. The system I am building is intended to be modular. When complete I will have a VHF/UHF station, an HF station, a battery box, an antenna system, and a computer system. Having a bunch of hardware and the power to run it is all fine and good, but if your antennas aren’t capable of getting the signal out all of those radios are useless.

Mast System

Like with my go kits, my first priority was to have a good VHF/UHF antenna system. A magmount on the roof of your car is OK, but for local line-of-sight communications the gain and height of your antenna are very important. I also wanted something that I could easily transport and erect by myself.

Antenna Mast (2)After some investigations I decided to aim for a simple lightweight mast system that I could mount to the trailer hitch on my car. The base for this setup is a hitch mount flagpole mount. For the mast I chose the MFJ 1904H. This mast solves a lot of potential problems for a portable mast system:  it is 5 feet long when collapsed making it easily transportable in my car, it is non conductive and will not interfere with any antennas mounted on it, and despite being made of fiberglass it is fairly sturdy (each tube wall is 1/8″ thick). I don’t intend to heavily load this mast so this should serve my needs well. In order to achieve a tight fit between the flagpole mount and the mast I used a section of 2″ PVC pipe as a spacer. When fully extended the top of the mast is about 21 feet high.

VHF/UHF

Antenna Mast (3)Antenna Mast (1)For the VHF/UHF antenna I chose the Two Way Electronix Dual Band Slim Jim. As someone who uses a J-Pole antenna as my base VHF antenna, I am very familiar with how well these antennas perform. The Slim Jim is a J-Pole made from 450 Ohm ladder line so that it can be rolled up for easy storage and transport. I mount the antenna to the mast using a nylon bolt and wingnut the passes through the insulation at the top of the antenna and a hole drilled in the top fiberglass section. This setup is very light weight and has virtually no wind loading which makes guying the mast unnecessary (under average wind conditions).

HF

For HF I did considerable research regarding what type of antenna is appropriate for emergency communications. A lot of ham radio is focused on making contacts at great distances (DX). This necessitates a low angle of radiation from the antennas being used. For a dipole this means that the antenna should be at least a half wavelength above ground. The most common HF EMCOMM bands are 40 & 80 meters (one half wavelength on 40 meters is about 66 feet, double that for 80 meters). For EMCOMM purposes, however, we only want to communicate within a couple hundred mile radius of our location. This requires a Near Vertical Incident Skywave (NVIS) propagation path. It turns out that this makes our lives a lot easier since a dipole can be used for NVIS when it is mounted much lower than it would typically be. Instead of trying to get a dipole very high, mounting it at 15 feet is ideal for this application. Another benefit of this approach is that at this height the dipole loses almost all of its directionality and is essentially omnidirectional.

Hamsticks

Antenna Mast (4)In an effort to maximize portability and reduce both setup time the footprint of the EMCOMM station I decided to try MFJ’s hamstick dipoles (MFJ-2240, MFJ-2275). These are loaded antennas that use a base section coil wound on a fiberglass rod with a stainless steel whip on the top. While a small loaded antenna will not have the efficiency, or the bandwidth of a full size antenna, it is considerably smaller (15 feet vs 66 & 133 feet). The hamstick dipoles actually perform fairly well. I was able to tune them for the digital portion of the bands and using the antenna tuner in my Icom 703 I can tune either dipole across their entire respective band. The dipoles are also fairly light weight and my fiberglass mast seemed plenty strong enough to support their weight. I would still like to try stacking the dipoles on the mast simultaneously in a cross configuration and seeing if that effects anything.

Short Dipole

EMCOMM Short Dipole (2)EMCOMM Short Dipole (1)In addition to the hamsticks I also built a shortened dipole for 40 & 80 meters. This antenna is based on a design I found here that uses ladder line to make a linearly loaded dipole. This design results in a dipole that is 33% shorter than a standard dipole with very little drop in performance. The main drawback for this design is reduced bandwidth, however, the tuner built into my Icom 703 was capable of tuning across the entire 40 & 80 meter bands. In order to make this antenna work on both bands I first made the 40 meter dipole section and then made EMCOMM Short Dipole (3)EMCOMM Short Dipole (4)separate 80 meter extensions that can be plugged into the ends of the 40 meter dipole using Anderson Powerpoles. When used on 40 meters, the 80 meter sections are unplugged and a small jumper is installed at the ends of the 40 meter dipole. This allows for easy band switching and quick setup of the antenna. Strain relief is critical when using ladder line, so I used a DX Engineering EZ Build Center T for the center feed point and PVC pipe with nylon bolts to secure the EMCOMM Short Dipole (5)ladder line in place (I also used hot glue to secure the nylon nuts in place). The PVC ends are dry fit together with a coupler and secured with a bolt and wingnut when the 80 meter extensions are used. This allows the antenna to be shortened when only the 40 meter band is needed. My final construction of this design used 300 Ohm ladder line and results in a 40 meter dipole that is 46 feet long (20 feet shorter than normal) and an 80 meter dipole that is 89 feet long (44 feet shorter than normal). For the center EMCOMM Short Dipole (6)EMCOMM Short Dipole (7)balun I used a Unadilla W2DU HF Maxi-Balun wire tied to the center T. DX Engineering’s 300 Ohm ladder line is made using 18 AWG stranded copper weld wire which is very strong, but also light weight. 300 Ohm ladder line also has the added benefit of being more tangle resistant than regular wire which makes it easier to handle when setting up and tearing down the antenna.

Performance

I plan to compare the dipole to the hamsticks to see how they perform in real operating conditions and will post my findings when I have them.

Ham Radio EMCOMM Go Kit – Battery Box

Battery Box (1)This project is the third part of my emergency communications system. The system I am building is intended to be modular. When complete I will have a VHF/UHF station, an HF station, a battery box, an antenna system, and a computer system. A portable battery system is a very handy item to have for ham radio in general (think field day, special event stations, etc.) and is essential for an EMCOMM kit.

Battery Box (2)I based my battery box around a deep cycle lead acid battery and I ended up choosing a group 27 battery with a reserve capacity of 160 (66.7 Ah). Reserve capacity refers to the number of minutes a fully charged battery is discharged at 25 amps before the voltage drops below 10.5 volts. This figure can be converted to amp-hours by multiplying the reserve capacity by 0.4167. According the Battery School within a BCI group size, the battery with higher ampere-hours (or RC) will tend to have longer lives and weigh more because of thicker plates and more lead. While lead acid batteries are heavy, they are also versatile and can be continuously trickle charged to keep them at full charge until they are needed. A deep cycle battery is appropriate for this application since their power level can be drained very low without damaging the battery, unlike a typical car battery.

Battery Box (3)For ease of transport and to keep the wiring organized and neat I store my battery in a plastic battery box and hardwired it to a Rigrunner 4005 power distribution block mounted on the box. I went with a small Rigrunner since this system will only be used with a few items at a time (1 or 2 radios, inverter for laptop power, low voltage lighting, etc.). I keep the battery charged using a NOCO Genius G3500 charger which is smart enough to not overcharge the battery and powerful enough to recharge the battery at a decent rate. After years of thinking about it I finally got around to standardizing all of my power connections with Anderson Powerpoles which make 12V power connections very modular and interchangeable.

This is a very useful and simple project that performs well for my purposes. I could easily parallel another battery with this one for increased capacity if the need arises in the future. You could buy a premade battery box with a Rigrunner, but doing it yourself is a lot cheaper.

Ham Radio EMCOMM Go Kit – HF

HF Go Kit (1)This project is the second part of my emergency communications system. The system I am building is intended to be modular. When complete I will have a VHF/UHF station, an HF station, a battery box, an antenna system, and a computer system.

HF Go Kit (3)After building my VHF/UHF go kit I realized that I already had almost all of the components I would need to build a low power HF go kit and decided to build one. I had an Icom 703 HF/6M transceiver sitting around not seeing much use and so I decided to use this as the base for the go kit. At full power this radio can output only 10 watts, however, it does have a built-in antenna tuner and is small in size which simplifies the go kit’s construction. It also has a detachable faceplate which allows for a lot of flexibility regarding where and how the transceiver body is mounted.

HF Go Kit (2)HF Go Kit (8)For power, I used the Radio Shack 3 amp switching power supply which came with the radio when I bought it on eBay several years ago. Unlike the VHF/UHF go kit I decided to include a battery pack in the case. This is more practical for this build vs the VHF/UHF station because the Icom 703 only draws 3 amps at full power, while the Kenwood TM-V71 draws 10 amps (10 watts vs 50 watts). The small lithium battery packs suited for this application only output about 4.5 amps maximum. For the battery pack I used an Intocircuit 32000 mAh lithium battery pack. This is a very versatile device that can output various voltages through its coaxial power jack in addition to 5V from its two USB ports. For this application I set the output to 12V, but if I needed to power my laptop I can also set the output to 19V or 20V. With 32000 mAh of capacity this battery pack should power the Icom 703 for hours. I also have the option to unplug the transceiver’s powerpole connection from the power supply or battery pack and plug it into my battery box.

To house the electronics I chose the Monoprice 22″ x 14″ x 8″ weatherproof hard case which is similar to Pelican cases at a fraction of the price.

HF Go Kit (4)HF Go Kit (5)The mounting of all of the equipment is done in the same way as my VHF/UHF kit. This consists of a base of 1/2″ plywood which is glued on top of a four 1/2″ spacer blocks in order to raise the sheet above the bottom of the case. This doubles the thickness of wood that the mounting screws have to grip when screwed in through the bottom of the case in addition to providing space to store excess cable from the faceplate separation kit.

HF Go Kit (6)HF Go Kit (7)Mounting the transceiver to the plywood is done using the mobile mounting bracket for the radio. The power supply is mounted using angle brackets and screws for a strong connection to the plywood. The microphone is attached with velcro to the lid of the case. The faceplate is mounted to the lid of the case using the separation kit HF Go Kit (12)HF Go Kit (13)mount which uses very strong double stick tape. The SignaLink USB is mounted to the top of the power supply using industrial strength velcro which allows for easy removal of the unit if I want to use it in a different configuration while holding it very secure when I want to leave it in the case. The lithium battery pack is also mounted using velcro (this stuff is pretty strong, it claims 1 lb per square inch, the battery weighs about 2 lbs and I am using about 10 square inches of velcro).

HF Go Kit (11)HF Go Kit (14)Before I mounted anything to the plywood I applied a coat of clear polyurethane. This not only makes the oak veneer look a lot better, it also seals the wood and provides some protection. The equipment was then mounted to the board and it was mounted in the case using 4 wood screws driven through the bottom of the case. In order to help restore the weatherproofing of the case I used silicone caulking to seal around the screw heads.

HF Go Kit (9)HF Go Kit (10)Overall I am very pleased with how this go kit turned out. To get on the air all I have to do is open the case, hook up power (either 120V or 12V), hook up the coax to the antenna and plug in the USB cable to my laptop if I need to run digital. In all it’s a very capable HF/6M station that weighs about 21 lbs and is the size of a small suitcase.

Ham Radio EMCOMM Go Kit – VHF/UHF

VHF Go Kit (7)Recently myself and others in my ham radio club have been getting more involved in emergency communications (EMCOMM) training and activities. As part of this effort to be better prepared for emergencies I decided to build a go kit or “station in a box” that could be used as a portable communications system. The system I am building is intended to be modular. I will have a VHF/UHF station, an HF station, a battery box, an antenna system, and a computer system.

VHF Go Kit (2)VHF Go Kit (1)Since VHF and UHF are the most used bands for EMCOMM I started with that. I already had a Kenwood TM-V71a dual band (2 Meter and 70cm) transceiver which is an ideal radio for this application. At full power it can output 50 watts and unlike many transceivers of this kind it features a data port on the back for easy connection to an external sound card (I use the SignaLink USB) for digital communications. It also has a detachable faceplate which allows for a lot of flexibility regarding where and how the transceiver body is mounted.

To house the electronics I chose the Monoprice 14″ x 16″ x 8″ weatherproof hard case which is similar to Pelican cases at a fraction of the price.

VHF Go Kit (4)VHF Go Kit (3)For power, I chose to include a 10 amp switching power supply in the go kit. I used the Astron SS-12 since its dimensions were such that it fit perfectly in the case when mounted next to the transceiver. In case 120V is not available, I can simply unplug the transceiver’s powerpole connection from the power supply and plug it into my battery box.

In order to mount all of the equipment in the case I built a base of 1/2″ plywood. The base consists of a single sheet cut to fit in the case glued on top of a four 1/2″ spacer blocks which raise the sheet above the bottom of the case. This serves two purposes:  first it negates the need to round the bottom edges of the sheet to match the curve of the case and second it doubles the thickness of wood that the mounting screws have to grip when screwed in through the bottom of the case. An added bonus of raising the sheet is that it provides space to store excess cable from the faceplate separation kit in an out of the way location.

VHF Go Kit (6)VHF Go Kit (9)Mounting the transceiver to the plywood is done using the mobile mounting bracket for the radio. The power supply is mounted by removing the rubber feet from the bottom of the power supply and replacing them with spacers and screws for a strong connection to the plywood. The microphone mount is also simply screwed to the plywood. The faceplate is mounted to the lid of the case using the separation kit mount which uses very strong double stick tape. The SignaLink is mounted to the top of the power supply using industrial strength velcro which allows for easy removal of the unit if I want to use it in a different configuration while holding it very secure when I want to leave it in the case.

VHF Go Kit (5)Before I mounted anything to the plywood I applied a coat of clear polyurethane. This not only makes the oak veneer look a lot better, it also seals the wood and provides some protection. The equipment was then mounted to the board and it was mounted in the case using 4 wood screws driven through the bottom of the case. In order to help restore the weatherproofing of the case I used silicone caulking to seal around the screw heads.

Overall I am very pleased with how this go kit turned out. To get on the air all I have to do is open the case, hook up power (either 120V or 12V), hook up the coax to the antenna and plug in the USB cable to my laptop if I need to run digital. In all it’s a very capable VHF/UHF station that weighs about 17 lbs and isn’t much bigger than a shoe box.