The MF and LF Field Day demonstration and outreach opportunity that has occurred for several years now is intended to expose operators to new spectrum while utilizing existing field day stations and equipment. Many operators today still have no or little idea about what is capable on these bands while others dismiss these bands altogether due to incorrect preconceived notions.
While many groups have undertaken advanced antenna projects at their field day sites in order to hear some of these stations in the past (full-size dipoles and direction loops like magnetic loops and K9AY loops), many are using existing infrastructure like 80-meter dipoles or even short HF verticals. Here are a few pointers to hopefully enhance your experience and help you find some degree of success during this operation.
- When tuning for CW signals, use either the “USB mode” or “CW mode” whose passband corresponds to USB receiver settings. This can be complicated sometimes because different rigs use different ways to describe which offset is used. Using CW mode may give you access to filters that you might not have while listening in a wider passband. Normal low band convention is to use the LSB. Things are generally opposite on MF and LF. When in doubt, switch the mode.
- Any antenna is better than no antenna. Experiment a bit to determine which antenna at your site allows an increase to the noise floor of the receiver. If you are using a large loop antenna for transmitting, consider opening up one side of the loop so that it looks like a bent random wire antenna.
- Even a small loop stick antenna or a tuned loop built into a hula hoop can allow you to hear signals at these frequencies from a very long distance. Here are a few simple ideas that someone with a junk box may be able cobble together rather quickly: http://njdtechnologies.net/a-few-unlikely-alternative-receive-antennas/
- If you have a lot of space at your site, consider a BOG (beverage on ground). While most beverages for 160m are far too short for a good pattern on 630-meters, many operators observe an acceptable improvement in S/N (signal-to-noise ratio, the most important part of any MF and LF receive operation). Even a grounded coax with a long wire on the ground can sometimes offer improved receiving conditions.
- When I was competitively operating with a club at field day a few years ago, I always made sure that I brought a K9AY loop system for use on 80m and 160m. These can also work very well at lower MF and LF.
- Propagation during the Summer will generally follow long haul ground wave during the day, switching to skywave at night. The drawback to nighttime listening in the Summer is the increased noise levels but don’t be afraid to listening around.
- USE HEADPHONES!
- Turn off your preamp and use your RF gain control and/or attenuators! Your antenna only needs to produce enough signal to exceed the internal noise of the receiver. Don’t expect S9 signals. Look for signals near the noise floor.
- If you don’t copy CW, use a program like FLDigi to help you. Decoders today seem to do a much better job than they used to.
- There will be some JT9 and WSPR activity and these modes are capable of working below the noise floor so just because you can’t hear it doesn’t mean your computer won’t be able to decode it.
- When entering frequency on your dial, remember that this is kHz and not MHz. A lot of newer radios are considered “DC to Daylight” rigs so make sure you are not listening to UHF and VHF frequencies. These signals are below the AM broadcast band!
- Check out the slides from a Hamcom presentation in 2016 by Eric, NO3M / WG2XJM, on the topic of receive antennas: https://www.dropbox.com/s/mqwpxobqv8gmlak/no3m.pdf?dl=0
- This exercise is an opportunity to explore and experiment a bit. Don’t look at it as an exercise with a box that has to be checked for field day points. While we ask that you send NTS traffic to the ARRL to let them know that you heard a station and originating NTS traffic can result in points for your operation, there are no points to be offered specifically for this exercise so operators who participate usually do so only for the love of radio.
73 and good luck in the contest!