Simplex Advice
How to improve your communication success when operating a VHF radio and or VHF/UHF radio without a repeater.
Created by Bruce, AA7PB, September 4, 2019 and edited on April 17, 2020.
With edits by Alex, KE7SIN, September 22, 2019, NET Net Topic
With edits by Jim, KJ7DMV, 14 October 2020.
Scenario: You’ve tried reaching a regional subnet controller (SNC) without using a repeater. You may have been operating from home or a NET staging using a handheld radio with its original rubber ducky antenna. You’ve had trouble hearing the subnet controller for your region during simplex exercises or you could hear the controller but weren’t able to check in. What can you do to improve the situation? Following are some things you can consider trying. They are roughly ordered from simple and inexpensive to complicated or expensive.
1. Ensure your radio is set on High power. Many handheld radios have two or more transmit power levels. Usually the highest level is labeled H.
Exception: When you know you can reach desired station(s) at a lower power, doing so will conserve battery power, e.g. Medium (M) and or Low (L).
2. Ensure your radio is set to wide deviation. Some VHF transceivers have more than one deviation setting. For FM radios, maximum deviation affects the range of the audio level. Transmitting at narrow deviation to a radio set to receive at wide deviation will make your audio volume half of other operators’ audio. If there are two settings on your radio, one is usually labeled Narrow or N and the other Wide or W. If your radio has more than one deviation level, you’ll want to make sure it is set to Wide.
3. Hold your radio vertically. The SNC will be using a vertical antenna. If you hold your handheld at an angle, its antenna will not be vertical. Its signal may reach the SNC’s antenna but not all of the available power will be received by the SNC’s antenna.
4. Fully charge your batteries. If your radio’s battery is much less than half charged, its transmit power will be reduced, especially after you have transmitted for several seconds.
5. Bring spare batteries. Some handhelds give you the option of switching to conventional batteries when the rechargeable battery is low. Other brands allow you to purchase spare rechargeable batteries. Make sure you keep these charged too.
6. Bring a way of recharging your batteries. Depending on the brand and model of your radio, you may be able to plug the radio or its charger into a “cigarette lighter” socket or an inverter connected to a 12 volt battery.
7. Adjust your location. While it's generally true that VHF radio signals travel to a receiving antenna by a “line of sight”, when line of sight is not possible, there are other possible paths. These other paths are greatly affected by exactly where you stand. Moving to the other side of a building or even a few feet from your first position can change the strength of your signal at the receiving antenna.
8. Get up higher. Your chances of getting a line of sight path to the SNC’s antenna or something closer to it can be greatly improved by finding a location 5, 10 or more feet higher.
9. Try a different subnet. The simplex region map is provided as a guideline. The path to the SNC in another region may be better than the path to SNC in your region.
10. Add a whip antenna. Replacing the short “rubber ducky” antenna that came with your handheld radio with a longer whip antenna will reduce the amount of energy that goes upward and downward from your radio and increase the amount that goes out horizontally.
11. Add an external antenna. Most external antennas for VHF radios vary from ½-meter to 1-meter long. Some “collinear” antennas are even longer. While using a longer antenna will not change the power that is radiated, it will focus that power horizontally and increase the energy that reaches the SNC’s antenna. If you have an inexpensive handheld radio, adding an external antenna may reduce its ability to hear distance signals, however. This is because the larger antenna may pick up strong commercial signals outside the Amateur Radio band, making it less sensitive to relatively weak Amateur signals. This has been a particular problem on the west side of Portland.
12. Use a directional antenna. Most external VHF antennas are vertical antennas. While they increase the portion of the energy that radiates horizontally, that energy is radiated in all directions equally. A directional antenna like a Yagi can be pointed in a particular direction and most of the energy will be radiated in that direction. While these antennas won’t work well if you’re trying to communicate with people in several different directions, if you are primarily trying to communicate with SNC, you can point a directional antenna towards the SNC’s antenna. If you use a YAGI antenna, make sure its radiating element is oriented vertically rather than horizontally like an old-fashioned roof-mounted TV antenna. If you don’t know where your SNC is located but know his/her call sign, you can look up the SNC’s address in the FCC database. Fill in the call sign in the License Detail section of the form located at https://wireless2.fcc.gov/UlsApp/UlsSearch/searchAmateur.jsp
13. Get your external antenna up higher. Your chances of getting a line-of-sight path to the SNC’s antenna or something closer to a straight path can be greatly improved by raising your antenna 10 or more feet in the air. I’ve had good success repurposing a telescoping paint pole, duct-taping my antenna to it and holding it up with nylon cords staked in three directions from the pole.
14. Move to a different location. If your neighborhood has hills or other obstacles, moving to a different part of the neighborhood or a higher elevation can make a big difference.
15. Replace your feedline (coax). Increasing the quality of your feed line will increase the amount of energy that reaches your antenna. If you’re using an external antenna and your feedline is much longer than 10 feet, you should make sure it is at least RG-8X rather than RG-58. Even better would be RG-213 or LMR 400. Note, however, that LMR 400 is less flexible than RG-8X and RG-213 because its center conductor is solid rather than stranded.
16. Shorten your feedline (coax). If you bought a 50-foot piece of antenna cable but your antenna is only 15 feet from your radio, replacing it with a shorter cable or equal or better quality can increase the amount of energy that reaches your antenna. (Be careful about making your own cables as cable connectors are notoriously difficult to solder. Be sure and test any home-made cables.)
17. Buy or borrow a fancier radio with more power. The maximum transmit wattage of most handheld radios is 5 watts or so. A mobile VHF or VHF/UHF radio will often support up to 50 watts. They can be operated from 12-volt batteries at a staging area and from a 12-volt power supply at home. Some people mount them in their vehicles and mount an external antenna on the outside of their vehicle. Another alternative is a mag-mount, which you can place on the top of your vehicle or perhaps a cookie sheet.
18. For planned exercises, try to find out where your nearby SNCs will be located. This is particularly important for directional antennas. If you know the operator’s call sign you can look it up at https://wireless2.fcc.gov/UlsApp/UlsSearch/searchAmateur.jsp
19. If your radio supports it, make a backup copy of your radio’s settings, preferably well ahead of time. Then reset to factory settings and reload your backup. This could be using Chirp or RT Systems software, or if your radio has a backup feature, use that.
20. If you have a second radio available, try using that to test your send/receive functions. Or just use it to ensure that your transmission is being heard.
21. Make certain your antenna is securely connected.
22. Certain electronic devices create radio frequency interference. For example an LED light bulb or solar charger may emit local interference with your radio. Try turning off individual items inside your house. Some interference covers a larger area. For more information visit http://www.arrl.org/radio-frequency-interference-rfi
23. Try adjusting your squelch setting, or turn squelch off.
24. Verify that your radio settings do not have an active offset as is used for repeater operation. If it does have that offset active, you will be transmitting on the wrong frequency for simplex operation.
25. If you are using an external microphone, make sure the plug is seated securely. Also try operating without it to verify it is not faulty.
Questions/Comments email [[1]]