4 meter band at YOTA 9A by team France

This blog post is written by YOTA Team France!

On Tuesday morning, the French team (Jules F4IEY, Maxime F4IQN, and Paul F4ILV) decided to operate, using their own QRP rig, on unusual amateur radio bands during the morning break.
To do this, we deployed our own setup with a portable dipole antenna and laptop in the middle of the camp.

At first, we wanted to try to operate the 4m band using the available rigs. After finding out it was not possible, we decided to tune our own Buddipole antenna on it, using a bunch of adapters and a nanoVNA to adjust both arms the right way. Then, we tried operating 70500 kHz SSB and FT8.

In a nutshell, the 4m band in Croatia is located in the VHF low band section (VLB) limited between 70.5 and 70.6 MHz. It is pretty interesting to use in terms of propagation as it combines both ionospheric and tropospheric properties.

Why operate 4m instead of 6m or another conventional VHF band? Well…The answer is quite simple: in France, it is forbidden to use this band because it is allocated to other public services that probably do not exist anymore such as analog ambulances or firefighters. So we decided to take the 9A summer camp as an opportunity for us to operate on it (and show it to our French old fellow hams what it looks like ^^).

Another interesting band we just figured out recently, that could also be used in Croatia, is the 8m band. Located between 40 and 40.5 MHz, a special local (non-CEPT) license is required to transmit on it as the third harmonic could interfere with the air band, especially near the emergency section (around 121.500 MHz). To get this grant, it could take weeks or even months; the HAKOM (local FCC entity) needs to verify that the transmitter used makes a clean modulation with no additional harmonic waste.

To comply with the restrictions, the team members told us operation might be possible using one of our available 9A special calls. It still needs confirmation though, it could be interesting to show fellow hams, the whole potential of these unknown and unused bands.

Still, we managed to tune the dipole quite easily on this band. However, unfortunately, we could not go further than listening, after finding out that the All band ICOM IC-705 rig does not support 4m…
But even without transmitting anything, we were able to listen to some CW beacons and other weak signals.

Next level: hoping to do the same kind of operation, with at least one QSO on 4m in the next few days of 9A Summer camp.
We definitely think that these forgotten bands need more attention.
Long live QRP, a power consumption-friendly amateur radio operation, promoting portable setup, anytime, anywhere!

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