John, K9JMS recently received permission from the FCC to carry out propagation tests at 40 MHz (8m) and 70 MHz (4m) and he was granted the callsign WQ2XDM for a period of two years.
Note that this is NOT an amateur radio licence and no two way communications are allowed. Its purpose is strictly for "scientific and engineering-based propagation research".
The 40 MHz and 70 MHz bands are NOT amateur radio bands in the United States and this is a case of someone getting a permit to make narrow band digital transmissions and seeing if the signals were heard.
John describes it as follows... "WQ2XDM Propagation Research - Florida-based experimental station studying low-VHF propagation on the 4 meter (70 MHz) and 8 meter (40 MHz) bands using weak-signal digital modes including WSPR and FT8."
The licence has the following conditions attached...
8m band - 40.660 to 40.700 MHz - 10-watts ERP max (FT8 & WSPR)
4m band - 70.000 to 70.200 MHz - 25-watts ERP max (FT8 & WSPR)
40.660 to 40.700 MHz is the 40 MHz ISM (Industrial, Scientific & Medical) band.
70 MHz in the United States was used in the past for analogue TV broadcasts.
The image above shows where the experimental bands are located. The 8m band at 40 MHz is between the 10m and 6m amateur radio bands and shares a lot of the propagation characteristics of both bands.
The 4m band is located between the amateur 6m band and the 88-108 MHz broadcast band and again, it shares characteristics of both bands.
Licence application... This is part of the licence submissions... "Although the applicant holds an amateur radio operator license, that license is not being relied upon for any aspect of the proposed testing. All transmissions associated with this application would be conducted exclusively under the authority of the requested Part 5 Experimental Radio Service license, and not pursuant to Part 97.
The applicant's amateur license is incidental and does not define, authorize, or govern the experimental operations described in the application.
To confirm, the testing requested is not amateur service testing under Part 97, and the proposed operations are not intended to be conducted as amateur radio communications or amateur experimentation. The requested authorization is sought under Part 5 (Experimental Radio Service) for the purpose of scientific and engineering-based propagation research and measurement on the specified frequencies.
The proposed experimental operations consist of controlled test transmissions initiated solely under the authority of the Part 5 experimental license. These transmissions are intended to generate propagation data and are not communications, message exchange, or amateur experimentation within the meaning of Part 97.
Use of Digital Waveforms and Third-Party Reception - Digital waveforms such as FT8 are proposed solely as standardized, well-characterized signaling formats used to generate predictable, spectrally efficient emissions suitable for propagation detection and measurement. The transmissions will be non-interactive and will not involve acknowledgments, responses, or completion of two-way communications.
Reception and confirmation of these experimental signals relies on passive observation and reporting, including reception by licensed amateur radio operators located outside the United States and by automated third-party signal reporting networks (such as PSK Reporter and WSPR-based reporting systems). These entities function only as passive receivers and reporting sources and are not participants in the experimental transmissions."
In the past, a number of radio amateurs in the USA received experimental callsigns for the 40 MHz band. These were used to make contacts which I suspect in the view of the FCC was quasi-amateur radio operation and they refused to renew the permits after the two year period had expired.
What to expect???... The 40 MHz and 70 MHz bands are likely to experience a number of the familiar propagation modes.
This is a map of the USA with some range circles...
40 MHz - The red line shows the typical range of one-hop Sporadic-E at 40 MHz (8m). In late April, early May & August, the range is typically about the 1200 to 1600 km mark and will sometimes extend as far as 2200kms.
During the peak of the Sporadic-E season in late May and the months of June & July, the openings become more intense and the skip distance can drop to below 1000kms.
The distance to the Caribbean is pretty good for Sporadic-E reception reports.
The Yellow line shows the possible range of F2 layer propagation and it's possible that WQ2XDM will be heard in California in months like November and February near the solar maximum peak. That essentially means maybe Feb 2026, Nov 2026 and Feb 2027. After that, conditions will decline and there will be fewer east-west openings.
The maximum usable frequency (MUF) is above 30 MHz most days at the moment but it doesn't quite reach 50 MHz. The question is whether it will reach 40 MHz? Reception of a 40 MHz beacon can indicate that an opening on the 50 MHz band is on the way.
In terms of tropo and local conditions, ranges out to about 200kms should be possible.
70 MHz - The green line shows the typical Sporadic-E distances at 70 MHz and the most common openings are around the 1500 to 180km mark.
Outside the USA... Let's look at the bigger picture...
40 MHz should be excellent for F2 layer propagation on north-south paths from Florida and the signals from WQ2XDM to South America should be possible for several more years.
The purple line shows the path for TEP (Trans-Equatorial Propagation) and the optimum path will be to Chile (CE) around 8pm local time. 40 MHz is a low enough frequency that there should be a considerable amount of east-west spread and openings to N Argentina (LU), Uruguay (CX) and S Brazil (PY) should be possible.
TEP openings at 70 MHz to Chile should also be possible but I think the problem here is finding people who are interested in trying to listen.
The yellow line on the map shows the possible range of some signals via F2 layer propagation. Openings to Europe are very likely as Florida is the most south-easterly state. The further south in Europe, the more likely the openings. i.e. I'd expect to see plenty of openings on the 40 MHz band to Spain and Portugal.
As for 70 MHz? It would be really interesting to see any reports of multi-hop Sporadic-E openings on 4m across the Atlantic. A lot of paths on the 40 MHz path have been done before but we're still in the early days of exploring very long paths on frequencies like 70 MHz.
In conclusion... It's good to see some experimentation on low-band VHF frequencies in the United States. I can see several challenges with the reception of the signals on the two bands. One is the relatively low power and the other is that a lot of people will be using compromised antennas tuned for other bands for reception.
If you're in the US then trying listening on 40.680 MHz FT8 and see what you can hear.
Links...
