Martin's Site
  • Home
  • Ham Radio - K0BXB
    • Logging Contacts
    • The Shack
    • Operating Modes >
      • WSJT-X/FT8
      • DMR
      • D-STAR
      • Ultra Portable PSK/Digital
    • Antennas >
      • Comparing Antennas
      • The Artifically intelligent Antenna
      • Magnet Loop >
        • Mag Loop Overview
      • Portable Antennas >
        • 2 Meter Portable J-pole
        • Five Portable Antennas
        • End Fed Antennas >
          • End Fed Half Wave Antenna >
            • EFHW Summary
          • 29/35 foot end fed wire >
            • Balun or no Balun
          • 51 Foot End Fed Wire
          • 84 Foot End Fed Multi-band Antenna
        • Vertical Antennas >
          • Nine Foot Portable Vertical
          • Short Verticals >
            • DIY 40m -10m Short Vertical Antenna
            • QRPGuys DS1 40m -10m Antenna
            • Pac 12 Portable Vertical Antenna
            • Spiral Wound Vertical
          • 1/4 wavel 20 meter Veritcal >
            • DIY 6 Band Vertical
            • Make a KW4JM vertical
          • QRPGuys 3 Band Vertical
          • Silver Bullet 1000 TIA
          • Portable 17 ft. wire vertical
        • Other Portable Antenna Options
      • Dipoles/Inverted VEEs >
        • Off Center Fed Dipole OCD
        • Comparing the Trap vs. Fan Inverted Vee
        • Link Inverted Vee
        • Trap Antennas >
          • 20 & 40 meter trap dipole qrpkits
          • 40/20 Meter Trap-Inverted Vee
          • 17/20/30/40 Trap Inverted Vee
        • 40/20 Fan-Inverted Vee
        • 40 Meter Inverted Vee
        • G5RV
      • Base Station and General Antennas >
        • G5RV
      • Portable Masts
      • Antenna Test Gear >
        • NanoVNA
        • X5105 Antenna Analyzer
        • Field Strength Meter
    • Radios >
      • IC-705
      • IC-7300
      • XIEGU G90 >
        • G90 Go Kit
      • X5105 >
        • x5105 Go Kit
        • QRP (x5105) Statistics
        • Repairing Mic Cord
      • QRPLabs QCX Transceiver
      • Ten-Tec R4020 QRP Transceiver
    • Portable HF.... >
      • Pedestrian Mobile >
        • Ped Mobile Considerations
      • POTA - Parks On The Air >
        • Thots on POTA Activations
        • My Ideal POTA Kit
        • POTA - Lizard Mound State Park k-9704
        • POTA k-3383 Bald Mtn State Rec Area
        • POTA k-2314 Pine Lake State Park
        • POTA K-4429 Coronado National Forest
        • POTA K-4491 Superior Nat. Forest
        • POTA K-1440 Big Foot
        • POTA K-4265 Bong
        • POTA K-1437 Aztalan State Park
        • POTA - Ice Age Scenic trail K-4238
      • Ham Radio Field Days >
        • 2021 Field Day
        • 2021 Winter Field Day
        • 2020 Field Day
        • 2020 Winter Field Day-
        • 2019 Field Day
        • 2018 Field Day
        • 2016 Field Day
        • 2015 Field Day
      • 2020 Portable Ops
      • Thoughts on Portable Operating
      • Thoughts on Operating QRP/Portable
      • Portable Power
      • Portable CW Keys
      • Tuner/Matchbox >
        • ELECRAFT T1
        • Tuna Tunah II
        • EMTECH ZM-2 ATU
    • Going Mobile HF & VHF >
      • 2020 Mobile Installation
      • 2015 Re-install the Mobile
    • Miscellaneous Ham Radio Topics >
      • Baluns, Ununs, Etc.
      • Keeping wires and ropes untangled
      • Helping Others
      • Things Happen
  • Backpacking/Camping
    • 2020 Backpacking/Camping Season >
      • 2020 Oct Boundary Waters Trip
      • July 2020 Koehler-Andrea St. Park Birthday Camping Trip
    • 2019 Backpacking/Camping Season >
      • September 2019 High Sierra Camp Loop
      • August 2019
      • June 2019 Boundary Waters
    • 2018 Backpacking/Camping Season >
      • Oct 2018 Boundary waters
      • August 4-5, 2018 Wisconsin River Canoe Trip
      • July 16-18 Devil's Lake Birthday Campout
      • June 28-30, 2018 Backpacking/Camping
      • June 2018 ARRL Field Day Camput
      • April 2017 Ice Age National Scenic Trail
    • 2017 Backpacking/Camping Season >
      • July 2017 Camping at Timber-Lee Christian Campground
      • Cancelled Ice Age Trail Backpacking Trip
      • June 2017 Hiking/Backpacking/Camping >
        • Cave of the Mounds and Blue Mounds State Park
      • May 2017 Backpacking/Hiking/Camping >
        • May 19 Ottawa Lakes Campground
        • May 4-7 2017 Porkies Backpacking Trip >
          • Porkies Backpack Trip Day 1
          • Porkies Backpack Trip Day 2
          • Porkies Backpack Trip Day 3
          • Porkies Backpack Trip Day 4
      • April 2017 Backpacking/Camping/Hiking
      • March 2017 Hiking/Camping More Preparations
      • Feb 2017 Hiking/Camping
    • 2016 Hiking/Backpacking/Camping Season >
      • December 2016 Hiking/Camping
      • November 2016 Hiking/Camping
      • Oct 2016 Boundary Waters Canoe Area Trip
      • August 2016 Camping
      • July 2016 Hiking/Camping/Backpacking
      • June 2016 Hiking/Backpacking/Camping
      • May 2016
      • April 2016
    • Shelters >
      • Tents >
        • Reparing Tent Poles
      • Hammocks >
        • Hammock Stand >
          • Portable Hammock Stand
        • SnakeSkins or Sleeves vs. Stuff Sacks
        • Hammock Suspension
        • Keeping Warm in a Hammock >
          • Lite Top Quilt or Bag Liner
          • DIY Under Quilt
    • Glacier National Park 2015
    • Training for Glacier National Park Backpacking Trip
    • Backpacking Stoves >
      • Trangia 27-3 UL Stove >
        • Cooking with Trangia
        • ALOCS Trangia Look Alike Burner
      • Fancee Feest Stove >
        • Fancee Feest & Stanley Cook Pot
        • Another Cat Food Can Stove
      • DIY Alcohol Stove
      • DIY Igniter for Alcohol Stoves
      • Lexada Wood-Gas Stove
      • Wood Burning Backpack Stoves >
        • Emberlit Fireant
      • Gas Cannister Stoves
    • Backpacking Food >
      • Cowboy Coffee
      • Santa Fe Cheesy Beans and Rice
      • Healthy Instant Oatmeal Packets
      • Bacon Ranch Chicken Wrap
    • Other Gear
  • Adventures
    • 50th Anniversary In Alaska >
      • Day 1 Sites in Fairbanks
      • Day 2 Morning River Boat Cruise
      • Day 2 Afternoon travel to Denali
      • Day 3 Denali History Bus Tour >
        • McKinley Wilderness Princess Lodge Photos
      • Day 4 Coach ride to Anchorage/Whittier
      • Day 5 Ship Cruise at Yakutat Bay and Hubbard Glacier >
        • Photos of Yakutat Bay
      • Day 6 Galcier Bay
  • RC Planes
    • 2019 Flying Season
    • 2018 Flying Season
    • 2017 Flying Season
    • 2016 Flying Season
    • 2015 Flying Season
    • Great Planes Escapade - .40 size
    • T-6 Texan
    • Cessna 170
    • Fokker V.23 WWI Combat Sport Scale Plane
    • Great Planes PT-40 Trainer
    • Great Planes Combat Spitfire
    • Hobbico TWINSTAR
    • Other Planes >
      • Flite-Test FT-Cruiser
      • Micro Fokker Eindecker by Dave Robelen
    • Things I've learned....
  • About
    • July 12, 2017 Flood
  • Other....
    • Remembering Charles & Eva >
      • Feist Family Photos
  • KW4JM Contact Log

Antenna Test Gear

2018-10-29 How do you tell whether an antenna will work? Perhaps the best way is to use it! Second best is to read other's experience with a particular antenna or antenna type. This is probably more subjective than your own on-air use. Not only are your reading (or talking) about the actual antenna performance, but that is all filtered through the other person's situation and opinions which will be different than your own. If I've learned anything about antennas it is that my own prejudices on the topic, coupled with propagation conditions which can be dramatically different every time you hit the key or press the push-to-talk button, both factors severely clouding the actual "objective" performance of a given design or antenna. Few of us have contexts and equipment that allow us to make truly objective and accurate measurements that "prove" the performance of any given antenna. Ultimately the true measure is whether the guy I want to hear and be heard by can usefully hear me and I him. If so, the combination of power, transmitting/receiving skills, propagation and antenna work!
But there are some tools that help us get to that "working" place. SWR measuring tools are close to indispensable. Thankfully most rigs today include some form of SWR measurement. The primary and minimal point of SWR is that it must be low enough at the transmitting terminals that the transmitter can push  signal into the feedline, hopefully all it is capable of. With today's rigs that is generally somewhere around 2.5:1 or below. If the transmitter simply won't transmit or reduces the power so much that it is as if it weren't transmitting, all else is irrelevant.
Everyone pretty well agrees that the "best" antenna will look to the feedline and then the transmitter to be 50 ohms resistive, which is approximately the case with a resonant half wavelength dipole. That supposedly minimizes losses in the feedline and delivers the most of the power sent into the feedline by the transmitter to the antenna. Of course a dummy load, by that measure is a perfect antenna since it is a 50 own resistor across a 50 own feedline which attaches to the transmitter which is designed to see a 50 ohm resistor. That also means that the feedline length, generally coax, is not important beyond the fact that the longer it is the more power is lost in the wire of the feedline. But, the dummy load is actually a terrible antenna since almost all of the energy fed to it is dissipated as heat rather than RF into the outside world.
That brings us to the second most important aspect of an antenna. Assuming it looks good to the transmitter and feedline, how well does it radiate the power it is receiving? The standard for that is a resonant half wavelength dipole. It looks very much like a 50 ohm resistor to the feedline and transmitter and according to people who have researched such thing for many years delivers most of the power it receives to the outside world.
That brings me to the next issue. Given that the antenna itself is both receiving and delivering most of the power that the transmitters sends to it, how much of that power is going where I want it to go? Answering that question requires mostly magic! I'm joking but it's not far off as things like surrounding objects; the ground below, trees, buildings, countryside, ionosphere, sunspots, solar storms, and more now come into the equation. And when it comes to communications all those factors ALSO impinge on "the other end" as well. A perfect signal going into a perfect antenna over perfect ground, etc. will appear terrible at the other end if the other guy is using a dummy load as his antenna!

SWR Bridge

My conclusion is that though the lowly SWR is both blessed and cursed by many in terms of its ultimate usefulness, it is just about the ONLY thing most of us will ever be able to use somewhat helpfully as it deals with an essential thing that we have some influence over through decisions we make; i.e. dipole, vs, vertical, inverted vee, traps, links, etc. All of those are irrelevant if our transmitter won't transmit! So for me, the most essential piece of antenna related test equipment is an SWR bridge of some sort at the antenna terminal of our transmitter.
Over the years I've had many of them. Only a couple were stand-alone type like this MFJ-860 model. Some were integrated into a tuner like this MFJ-971 tuner. And I believe every purchased rig I own now has one incorporated into it so usually no outboard SWR bridge is needed. But I wouldn't be caught without one anymore. Almost every time I tap a CW key or press a push-to-talk button I glance at the SWR.

Antenna Analyzer

2018-11-07 An antenna analyzer is a very useful, almost essential piece of test gear, especially if you want to build your own antennas. I borrowed an MFJ-259b (now superceded by the MFJ-259c) from a neighbor when I built the 40/20 meter fan and trap inverted vee antennas for Field Day. It was so helpful. I don't think I could have made them without it.
Then when I got my Xiegu X5105 QRP rig back in August I began playing with its SWR sweep feature. It is not as good as a true stand-alone analyzer but it is pretty good, far better than anything I've ever had before. I've used it exclusively while building and tuning my 18, 20, 30 & 40 meter link inverted vee and my trap version of the same antenna. It works so well that I cancelled an order for a MFJ analyzer. I wouldn't recommend the X5105 just to get that function but it is a very effective tool.

Antenna Bridge

Another useful piece of antenna test gear that is much less expensive than a true analyzer is the MFJ Antenna Bridge. I've had the 204B model for some time which has been superseded by the MFJ-207. The one I have has one major drawback, the frequency dial is not all that accurate. I actually added a CW audio output frequency counter to mine which helps but the signal level is too low for it to read anything above 20 meters. Never-the-less it is a major enhancement. The Antenna Bridge will tell you the resonant frequency and the approximate "resistance" at resonance. It is pretty close and is far better than nothing. I've used it a lot over the years when I had no other practical option and got my antennas pretty close to what I wanted.

Field Strength Meter

Another piece of gear I have "always wanted" and wondered what it would tell me is a field strength meter. it just makes sense in concept. And so a YouTube video on building a cheap field strength meter caught my attention. And since I had the very digital meter used in the video and all the parts lying around, I decided to build one. I have yet to use it but it looks impressive!
Proudly powered by Weebly