Question: What’s an easy and inexpensive way of improving my mobile radio receiver performance?

Most mobile installations, for safety reasons, position the radio out of the way, under the dashboard, on the passenger side of the vehicle, or even under the seat! As result, the mobile radio speaker is often facing down, away, up at the dashboard, or into the carpet.

Yaesu FTM-3100R VHF FM Mobile Transceivers FTM-3100RSome radios, like the new series from Yaesu that includes the FTM-3100R and the FTM-3200DR, include a “front facing” speaker. This is an improvement, but it might be facing your passenger’s knees rather than your ears.

So, what do you do?

Answer: Use an external speaker, and mount it closer to your ears!

There are many options available, but DX Engineering has a very economical speaker that works great: the DXE-281. This will allow you to position the speaker closer to your ears and reduce the interference from road and other noise.

How and where do you mount it? There are as many ways as there are different vehicle styles and configurations. You may have to use your imagination. In this writer’s case, there is an unused sunglasses holder built into the headliner of the vehicle.

DXE-281 in Sunglasses Holder

This provided a perfect place to position the speaker much closer to the driver’s ear, and it required no drilling or other modification of the vehicle. This is but one example of a simple, inexpensive, but effective mobile installation upgrade, and it cost less than $20!

DXE-281 in Car Sunglasses Holder


Many hams ask why they should bother to add the recommended radial field to their ground-mounted vertical antenna. There are reasons why it’s a good idea.

Ground Radial
Ground-mounted verticals use the Earth as their counterpoise. The vertical radiator is only half of your resonant or non-resonant vertical antenna. The other half is counterpoise; an imaginary radiator directly opposite, and on axis with, the wire or aluminum standing on the ground. This second half essentially makes your antenna a vertical dipole. Because of varying soil conductivity and chemical composition, some “ground” is better at the conduction of RF energy than others.

Why does the ground need to conduct at all? The vertical does that. Consider that your antenna represents a load at the end of your coax. Ideally, the RF current flows out the center conductor from the transmitter, but also must flow back to the transceiver on the coaxial shield to complete the current loop. If the vertical is radiating the current, then where does the returning current flow come from? The answer is the ground!

A radial field enhances the ability of the ground around the vertical to conduct RF energy. The radials “collect” the return current required for efficient antenna operation. Some hams complain that radials narrow the bandwidth of the antenna. This occurs because the radial system raises the “Q” of the antenna system. The higher the “Q” value, the more efficient the antenna will be. With a good radial field, radiation resistance will decrease, RF current will increase and bandwidth will narrow. That is just as it should be. Be aware that a poorly efficient antenna can have a good SWR. How efficient a radiator is a 50 ohm resistor across your coax? That’s called a dummy load and they all have very low SWR!

When your vertical is ground-mounted, use a good radial field to raise radiation efficiency. You’ll have a better antenna system that will benefit your station and the joy of your radio hobby.


Question: Is it OK to run an amplifier on 120 volts AC?

This is a question that many new Amateurs ask themselves when they’re buying their first amplifier. There are many reasons to ponder this, and one of them is: “I’ve already got a 120 volt outlet in the shack, and I don’t want to spend a fortune putting in a 240 volt line.  Electricians are expensive!”

“What difference could it make? I’m going to be running about a kilowatt output regardless of the line voltage. I know that a typical 1 kW output amplifier will draw a maximum of about 15 amps on 120 Vac and 7.5 amps on 240 Vac. In either case, that’s about 1,800 watts input (120V x 15A or 240V x 7.5A) and since Ohm’s law tells us that volts x amps = watts, there should be no difference – right?”

Wrong! That ignores voltage drop.

There are many reasons why running your amplifier on 240 Vac is a lot better:

  • Line voltage regulation is better.
    1. Typical voltage drop of drawing 15A on a 120 Vac 20 Ampere circuit (12 gauge wire) is about 3 percent. This means that every time you transmit, your 120 Vac line is going to sag to about 116 volts.
    2. This doesn’t seem like much of a difference, but in a tube amplifier, your high voltage is going to also be sagging by that same 3 percent! If your amplifier uses 3,000 Vdc, it will be dropping 3 percent to about 2900 Vdc (and all your other power supply voltages will drop by 3 percent, too!)
    3. This will cause the line voltage that your other appliances receive to drop whenever you transmit. This is enough to cause noticeable dimming or blinking of typical household lighting. This doesn’t go over well with spouses and kids!
  • On a 240 Vac 20 amp circuit, you will draw half as much current.
    1. By the above analysis, you’d think that this would result in your 240 line voltage dropping by only half as much as we saw on 120, or 1.5% – but, you’d be wrong.
    2. The benefit of twice the line voltage results in a whopping 4:1 improvement in line voltage regulation and your 240 volt line will only vary by 0.75% to 238.2 Vac when you transmit. Even on a 240 Vac 15 amp circuit (with smaller 14 gauge wire) you’d only have a 1.2% drop to 237.12 Vac.
    3. On 240 volts, your high voltage will only vary 0.75% instead of 3 percent. That 3,000 Vdc will only drop 22.5 Vdc when you transmit to 2977.5 Vdc – way better than dropping to 2900 Vdc! All of the other power supply voltages will remain more stable and only vary by 0.75%!

You’re making a significant investment in your amplifier. Give it the 240 Vac power it deserves so it can give you the best performance!


An RF transmission line short story about open wire feeder, ladder line, twin lead and the window line that we now use.

In years past, before the advent of coaxial cable and the need for SWR meters, uninsulated open wire feed lines were built by hams using non-conductive ceramic insulators. These efficient, low-loss RF transmission lines had a typical impedance between 200 and 600 ohms because they were between three and six inches wide.

Perfectly suited for the vacuum tube era of high impedance link-coupled tuner coils, their evenly-spaced insulators made those feedlines appear somewhat like rope ladders, hence the term “ladder line.” This moniker was indelibly etched into Amateur lore with the introduction of manufactured versions in the 1960’s and ’70’s, often made with white plastic insulators melted into the parallel solid copper wires. Conversely, earlier TV twin lead and transmitting twin lead were much narrower, old plastic-clad parallel transmission lines that had much higher losses at high SWR, like coax.

So let’s fast-forward a couple of decades to our modern, efficient 300 ohm and 450 ohm parallel-wire feedlines which have far lower losses than the old twin lead. Just as with open wire feeders, elevated SWR isn’t a problem for the present day version due to advances in plastics and the use of air. Originally called “window line,” because of the shape of missing sections of dielectric, now these feedlines are generically relabeled as Ladder Line, because hams just do that.

These lines are sometimes colloquially referred to as twin lead or open wire feeder. Our Ladder Lines are now used on DX Engineering Reversible Beverage Antenna Systems or DX Engineering baluns with wide range tuners to create extremely efficient HF transmitting multi-band wire antenna systems.

DX Engineering Ladder Line

In contrast to the impedance extremes of true open wire feeder, and avoiding the excessive losses of coax on non-resonant systems, our lowest impedance, 7/16 in. wide, 300 ohm Ladder Line allows tuners to cover more HF frequencies. DX Engineering “ready-to-use” Ladder Lines eliminate the tedious construction process of true open wire feeders. Comparatively, our Ladder Lines exhibit a virtual constant impedance and equivalent low-loss with the absolute practicalities of lower weight, less wind load, full power handling and, most importantly, durability.


When is an antenna tuner not an antenna tuner?

Answer: all the time!

“Antenna tuner” is really a bad name for the devices that present a low SWR to our transmitters and amplifiers. In the ’50s and ‘60s they were often, and more correctly, called “transmatches” for transmitter matchers.

Palstar BT1500A 1500 Watt Double L Balanced Antenna Tuners BT1500A

Palstar BT1500A 1500 Watt Double L Balanced Antenna Tuners BT1500A

When used in the shack, an antenna tuning unit (ATU) “looks” at the antenna, the feed line, the connectors or adapters and other factors to adjust the impedance and resistance values to an acceptable level for the transceiver. This process may be done manually by adjusting capacitors and inductors via front panel controls on the tuner, or automatically with microprocessors and relays switching inductors and capacitors without user intervention. Whatever method is used, the ATU doesn’t “tune” the antenna. It electrically matches the antenna SYSTEM to your transmitter.

To prevent feedline losses, a remote ATU mounted very near the antenna feed point can be a better way to go. This is especially true with ground mounted verticals, where access to service the ATU, if necessary, is easily accomplished. This approach will also limit common mode currents on the feedline, thereby reducing RFI and stray RF in the shack.


Have you heard Heard Island?

Big gun or little pistol… Here are 10 tips from DX Engineering to help get VK0EK in your log.

  1. Check the Forecast…Watch the propagation forecast for peak openings. dxa3.org has a map showing the grey line.
  2. Get Schooled…Study the band plan. Learn where they plan to operate. This will give you a good idea of where they will be transmitting and where they will be listening on each band.
  3. Signals, signals everywhere… SPLIT! SPLIT! The Team on Heard Island will always be working split frequency. They will transmit on one frequency, and listen elsewhere. Study the band plan and listen to the operator for instructions on where they are listening.
  4. Listen Lesson…As always; LISTEN, LISTEN, LISTEN. Listen before calling. Try to determine the operator’s patterns and style.  Are you moving around or listening in one spot? Anticipate their next move.
  5. Makes Sense…If you can’t hear them, don’t call them.
  6. Call of the Wild…Give your full call phonetically when trying to break the pile-ups on phone.
  7. Lil’ Pistol…Be patient. Don’t get frustrated….have fun. The team will be on Heard Island and operating until April 10th. Plenty of time for stations of all sizes to get an ATNO (All Time New One) in the log.
  8. Stop and Drop…Don’t Be a DX COP! Do not cause further QRM by yelling “Split”, “Up”, “Lid,” etc. it only makes things worse. Do not tune on the DX frequency or where they are listening.
  9. Transmit, Listen, Repeat…Give your call once and listen. If they are not going back to station throw out your call again. Do not continually call; listen to the timing and pattern of the DX station.
  10. Take a Chance…Your best chance of working rare DX in a pile-up is when the station is working split. Analyze their operating patterns, pick a transmit frequency that gives you a good shot, call – listen – call. Now go log a new one!

SITUATION: The Sound Card interface you just installed (SignaLink, RigExpert, Soundblaster) is not sending digital tones through the transceiver. The natural conclusion you may draw is that the sound card interface or cabling is at fault.

Digital Mode InterfacesFirst, let’s verify that the software you are using is actually generating tones to transmit.

To confirm your software (FLDIGI, MMTTY, 2TONE, DM-780, etc.) is generating tones, temporarily change the configuration of your digital software to transmit through the standard sound card and speakers in your PC, and send a test CQ from the software. If you do not hear the digital tones through the speakers, examine and correct the configuration of the software before proceeding.

NOTE: this is a good way to learn the sounds of various digital signals (RTTY, PSK31, OLIVIA, HELLSCHRIEBER, etc.) if you are not already familiar with them.

If you hear the digital tones in your speakers, return the configuration of your digital software to point to the sound card interface address(es), and review the transceiver’s menu settings (if applicable) with regard to AFSK signal source and level settings (these settings vary widely by transceiver make and model). You will need to consult your radio manual for assistance.




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