Category Archives: Antennas

Articles about Antennas, Feedlines, Towers and related equipment. Fixed, Portable and Mobile Antenna Articles are included.

Field Day 2018 is Almost Here!

Field Day is an Emergency Communication Preparedness, Communications Training, STEM Learning, and fun activity all rolled up into one event! Field Day 2018 is rapidly approaching and we’ve been working for over a month now to plan our 2018 operation. Field Day at the Nashua Area Radio Society is a major undertaking so we decided to share the Chairperson role among three members:

2018 Field Day Team Leaders
Team Leaders

It takes a great deal of support from our members to put together an operation at the level we do it at NARS. We’ve had many NARS members volunteer as Team Leaders to plan and pull together the many elements of our upcoming Field Day. Many, many thanks to all of our Team Leaders and to everyone who is contributing to support Field Day 2018!

Field Day 2018 Plans & Goals

Our Goals for Field Day 2018
Our Goals

We began our planning by setting some goals for our operation. Field Day at NARS centers around being a learning experience for all involved with a special focus on getting new members, new Hams, and young people on the air.

2018 Field Day Site Layout at Hudson Memorial School
2018 Field Day Site Layout at Hudson Memorial School

Our new site at Hudson Memorial School in Hudson, NH gives us the opportunity to experience Field Day at a new site. Our 2018 operation will double as our Open House for our High-Altitude Balloon program schools.

Space Communications Ground Station
Space Communications Ground Station

It will also provide an opportunity to test the space communications ground station that we are building to support an ISS Crew Contact with the students at Hudson Memorial School in the fall.

Station Plans

High Tech SDR System at Field Day
High Tech SDR System

We always like to incorporate new elements into our setup each year. This year we’ll be increasing the scope of our Software Defined Radio Setup and using it to add more Digital Stations.

Field Day Digital Station
Field Day Digital Station

We are planning a 10 Alpha station for our 2018 operation. With the additional Get On The Air Station (GOTA), free VHF station on 6m and the additional satellite ground station and 2m/70cm GoKit for Talk-in and Messaging use, we will have a total of 14 transmitters on the air at Field Day 2018! Here’s the planned breakdown for station bands and mode:

  • SSB Stations – on 40m, 20m, 15m, and 10m/75m
  • CW Stations – on 40m, 20m, and 15m/10m/75m
  • Digital Stations – on 40m, 20m, and 15m/10m/75m
  • Free VHF Station – on 6m (all modes)
  • Satellite Station – on 2m/70cm/23cm (all modes)
  • GOTA Station – on 15m/10m/75m SSB
  • Talk-in/Messaging Station – on 2m/70cm FM
Field Day SDR-Based GOTA Station
SDR-Based GOTA Station

Our GOTA will also use our Software Defined Radio system and share antennas with the Digital Stations. This approach provides an easy to understand and high-tech view radio equipment and SSB voice operations on the HF bands.

Generator Power at Field Day
Generator Power

We will again be in the Alpha category using off-grid power via generators. We will also have a solar/battery setup that we will use to make some contacts.

Antenna Plans

60 ft Digital Tower
60 ft Digital Tower

Antennas are a large part of any Field Day station and NARS brings a lot of top-notch equipment. We are planning to put up three towers again this year and all three will have yagi antennas for 20m/15m/10m along with wire antennas for 80m and 40m.

40m V-Beam High-Performance Wire Antenna
40m V-Beam High-Performance Wire Antenna

The 40m V-Beam wire antenna will be back for SSB and it has been optimized both electrically and mechanically.

Learning Opportunities

Setting up a Tower at Field Day
Setting up a Tower at Field Day

The setup of our antenna farm is a good example of one of the many learning opportunities at Field Day. Hamilton, K1HMS, and Jamey, AC1DC have been conducting Antenna Parties to give members a chance to learn how to build, setup, and tune our antennas. We’ll also be providing extensive training and information about all aspects of setup and how to operate during our June 5th Membership and June 12th Tech Night Meetings.

Team Operating at Field Day
Team Operating at Field Day

Learning to operate is another important aspect of Field Day. It’s a lot of fun for folks who are new to Field Day or to a particular operating mode such as CW or Digital to team up with a more experienced operator to operate as a Team. Doing this for your first hour of operating time will help you get up to speed on how to use a station to operate. You can also help out the more experienced operator by helping to capture call signs and exchanges and to log contacts.

Food, Fun, and Videotape at Field Day…

A Feast at Field Day
A Feast at Field Day

Valerie Merchant has again volunteered to provide food for us during our operation. Valerie did a great job with this last year and we are very happy to have her do this again this year. THANK YOU, Valerie!

WK1V's Video Drone
WK1V’s Video Drone

Also, Desmond WK1V will be bringing his drone again this year. Desmond took some amazing aerial video of our 2017 operation. Check out the video which follows.

Our 2017 Field Day Highlights Video

Important: Sign Up & Don’t Miss These Meetings

Our Field Day sign-up for Station Setup/Takedown, Operating, and Meals is available in our Members Forum on n1fd.org (don’t forget to log in to our website to view this link). Take a minute to follow the previous link and sign-up to be part of Field Day 2018! If you are not a member or are having trouble accessing the sign-up, please contact us at [email protected] and we’ll answer your questions and help you to sign up.

Field Day Station Training
Field Day Station Elements and Training

Also, we’d like to see as many members as possible attend our June 5th Membership and June 12th Tech Night Meetings. We will be sharing lots of information and how-to material and training between these two meeting. Please try to attend both to learn and take full advantage of the fun at Field Day. You don’t have to be an old hand or even have ever participated in Field Day before to have a lot of fun. Just try to make it out to these meeting and we’ll get you up to speed and help you to participate!

Bring Your Family & Invite Your Friends

Field Day Public Info Tent
Public Info Tent – Videos, Information, and a Talk-in/Messaging Station

Field Day is also a great opportunity to showcase Amateur Radio to the general public. We set up and staff a Public Information tent as a starting point for visitors to learn about the Nashua Area Radio Society and what we are doing on-site. We will provide tours of the site, a chance to Get On The Air at our GOTA station, demos of the equipment we are using, and much more! Please bring your family and invite your friends to come out to Hudson Memorial School in Hudson, NH any time between 2 pm Saturday, June 23rd and 2 pm Sunday, June 24th and visit our site. Here are some direction to our site (click below or refresh your browser if you don’t see the map) –

 

See you at Field Day 2018!!

Fred, AB1OC

A 40m High Performance Antenna for Field Day

The Nashua Area Radio Society has been using a 3-element 40m wire beam antenna for Field Day for the last several years. The antenna uses three guyed 50 ft. fiberglass masts from Max-Gain Systems. The antenna uses three inverted-V style elements separated by a little over 50 ft. Since we are in the northeastern United States, we can point the antenna on a fixed, 260° heading and it covers the entire U.S. well.

40m V-Beam EZNEC Antenna View - Antenna Optimization
40m V-Beam – EZNEC Antenna View

Our 40m V-Beam antenna was initially designed using EZNEC 5.0. It was manually optimized for decent gain and front to back performance and it worked quite well. Recently, we decided to try automatic optimization software on the antenna as part of a tune-up on the design for Field Day 2018. After looking around on the Internet a bit, we discovered a software package called AutoEZ which looked ideal the my project. You can read more about the optimization project and see the results via the link below.

Source: A 40m High Performance Antenna for Field Day | Our HAM Station

Our Field Day Wire Antenna information package has been updated to reflect the results of the optimization work. We have also added additional information to make the setup and tuning of our wire antenna including the 40m V-Beam easier. You can see the information package here.

Why Does The Antenna Formula 234/f Work?

antenna formula

The formula 234/f is a handy way to estimate the size of a ¼ wave antenna element based on the desired frequency for the antenna. Here is how to derive that number using only other constants and conversion ratios.

How big is a ¼ wave for a given frequency? We can use the band name as a hint (14 MHz is called 20m) but we need a more exact size.

The speed of light in a vacuum (c) is 3 x 108meters per second. The wavelength (λ) for a given frequency (usually referred by ν, but we’ll call f) is defined to be c/λ. Wavelength is the speed of light divided by the frequency. So, the wavelength in meters is:

We only want to know the size of a single cycle for this frequency so we can divide both the numerator and denominator by a million. That makes the numbers much smaller! Wavelength in meters is now:

That is, wavelengths in meters uses this simple formula:

But, we want this in feet (because we’re Americans) so we need to convert meters to feet. One meter is about 3.28 feet. So, convert wavelengths to feet:

which is

But we don’t want a whole wavelength; we want just a quarter of that for our dipole arm. Divide the whole thing by four.

which gives us

Why is this 246 and not 234? This is because we are using the speed of light as the speed of the current in the wire. But, nothing goes as fast as light but light! We need to put in the velocity factor for the wire (which is relative to the speed of light) to know how big a quarter wave is in the wire.

Choose 0.95 as the velocity factor as a guess for most antenna wire. That is, the charge propagates down the wire at about 95% of the speed of light.

which gives us the formula

The formula 234/f isn’t “magic”; it is just a distillation of the simple formula speed-of-light/frequency with all the unit conversions and velocity factor assumptions baked-in.

** Dipole animation from wikipedia.org

Posted by Scott, NE1RD

Daiwa CNW-419 Tuner Repair

Although I am brand new to the hobby of ham radio, I have been playing around with electronics and digital circuits for as long as I can remember. I am a software engineer by trade and have always loved the problem-solving challenges that software and hardware engineering offers.

Given my unfamiliarity with the ham radio world, however, I thought it might be fun to find a project in that space. Enter the Daiwa CNW-419 manual tuner.

Our Next Victim

My father found this poor soul on eBay, and it was in a bit of a bad way. It had some missing feet, the tuner button “didn’t work”, and there seemed to be a couple of loose pieces in the pictures, but generally the interior of the tuner looked very clean.

After looking up some reviews of the tuner and finding nothing but praise, I thought what the heck, paid the $75 and took the plunge.

It arrived carefully packaged, and after unwrapping it, I found that the tuner switch was indeed broken. In addition, the switch to change the antenna (it supports two antennas), didn’t seem to be working properly either. Both of the switches were push buttons, and neither of them would latch.

Taking It All Apart

A first look under the covers

Time to take the cover off and see what was going on. With just the top cover off, we can see the two problematic switches in the back. If we’re going to get to those switches, a lot more stuff is going to need to come off.

After removing the bottom, and disconnecting the back panel, we get a better view of the switches. Some black charring there, perhaps some RF arcing took place? Looking at the rest of the box and how neat and organized the soldering and wiring is, this looks out of place. I am beginning to suspect something is amiss here.

After pulling the switches completely out, there definitely appeared to be some sort of overload. Or perhaps just bad soldering? More investigation is clearly required.

Our problematic switches

The Game is Afoot

Examining the part number for the switches I pulled out, I was able to find the equivalent switch on DigiKey. The schematic for this switch indicated that it was simple non-latching push button ON-ON DPDT switch. Clearly not the original part, as the tuner front panel artwork indicates that these are latching push button switches.

At this point, I headed back to google to see if I could find what the original switch was, but could find nothing. Finally, I stumbled across an interior shot of the tuner from a guy in Thailand. After some zooming, it looked like an ordinary latching switch.

But First Some Math…

The tuner is rated for a maximum of two hundred watts, so we should figure out what our switches need to be able to handle. We don’t want to trust the previous components ratings since they were not original.

One hundred watts at fifty Ohms yields an RMS voltage of about seventy volts which is what my receiver puts out. Since the tuner is rated to two hundred watts our max RMS voltage should be one hundred volts. 125VAC switches are plentiful, and to be safe we should also probably shoot for a switch that can handle around five amps. Eight dollars and fifty-two cents later, we have a pair of switches rated at 125VAC and seven amps. Perfect.

Putting It All Together

I took lots of photos and notes while removing the switches but knowing that they could have possibly been installed incorrectly, I took a little extra care in laying out the connections for the new switches.

The switch for the antennas was straight forward enough. This was simply a DPDT doubled up and wired as a SPST with the center poles connecting to the center pole output of the tuning circuit switch.

The new switches installed

The switch for the tuning circuit was a little peculiar. When the tuning circuit is disengaged, the switch should connect the output from the amp making sure it passes through the metering circuit and bypasses the tuning circuit. Originally, the switch connected the first pole to the second pole of the switch using only the thin wire of a small capacitor hanging down. This was clearly insufficient, and somewhat dangerous as that thin wire would be passing the full power RF output of the amp. I suspect this probably happened at one point as the capacitor wire was extremely brittle, and broke after I removed it.

A Puzzle for Our Readers

The dangling capacitor was likely a power filter circuit (that’s my guess). You can find these on regular power circuits where a high voltage cap connects the power to ground. I assume they are also used on RF power circuits. Is this correct? Ham radio experts feel free to chime in. I tested the untuned circuit path both with and without the cap filter but could discern no difference. I suspect it might have been affecting my output signal, but I had no way to test that. In the end, I left it connected, figuring I would not do much transmitting with the tuning circuit disabled.

Tuning it Up

Time to test it out. Here it is with some new rubber feet from the hardware store ($2.47) sitting on top of my FT-450D.

The new, and the slightly less new

I purposely detuned my vertical, disabled the ATU on my receiver and checked the SWR. Infinite SWR readings for both the tuner and my receiver. Great. The auto tuner on my receiver can’t touch that. I then enabled the tuning circuit on the Daiwa, found the best band setting, and tuned it up. In no time I had the SWR down to one, and the forward power at maximum.

I love this thing.