On 11/08/17 19:29, Josh Branning wrote: > Hi, > > Recently I attempted a 9km communication via 4W CB radios and a homemade > 1/2 wave dipole, from a rural village, to a town. I figured with more > power and a low frequency, they might fare for unlicensed > communication. (I am based in the UK.) Unfortunately, I didn't manage a > voice signal over that distance. Someone other, who is into amateur > radio told me it may be to do with being at the peak of a solar cycle.
In the distant past I regularly managed 15-25km local regular conversations on 27MHz with 4 watt transmitters and 1/2 wave dipole. Further with a 3/4 wave Sigma 4. The critical issue is to ensure the standing wave ratio (SWR) is really low (lower than 1.5:1 and preferably 1.2:1) and that the antenna has a good ground plane, otherwise the signal footprint for the vertical elevation, instead of being flat along the ground like a a baguette, will be elliptical or even circular, meaning that the signal close to the ground will get weak quickly the further out the receiver is. I know some people that would top-feed the antenna rather than bottom-feed it to avoid needing to add a ground plane. > I am pretty surprised that the unlicensed link you used in the talk went > 39km. I would be interested to know the make and model of the USB > transceiver you used. Other people always seem to be able to go real far > on little power [7][8], I myself am jealous and have had little success. Using a pair of TP-Link CPE510 5.8GHz WiFi units I am able to link 2 farms 13km apart. The antennas are internal planar 2 x 2 MIMO and have a very directional footprint. _______________________________________________ Replicant mailing list [email protected] https://lists.osuosl.org/mailman/listinfo/replicant
