RADIO advice sought for URBAN prepping

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UHF ( Ultra high frequency) with its very short wave length works quite well in cities. It still gets blocked by big, tall buildings but has the ability to bounce around them. Position can be very critical. Just moving a few feet often will make a difference between perfect reception and no reception at all. The other advantage of UHF is that there are many hand held walkie-talkie type units available. Because the wavelength is so short, antennas for this band are also tiny. UHF radios can be very discreet.

Most readily available UHF radios are PMR446 units or Ham radio 430 Mhz bands.

Guerrilla repeaters constructed to operate autonomously from tower block roofs are also a good way to get signals across the cityscape. Again, UHF frequencies work well in this application. Built using one of the generic low powered Chinese radio clones, secured in a water tight box, with a small PV charging unit, this sort of installation can stay operational for a long time without need to touch it.

Another alternative is to use NVIS ( Near Vertical Incident Skywave) The idea here is to design antennas that encourage signals to be transmitted at a high elevation ( Near vertical), and for those signals to be reflected back to earth off the ionosphere, with the signals being received from overhead, so leapfrogging tall buildings. This is a system that is tried and tested. But there's a snag with it. Only certain frequencies get reflected off the ionosphere. The higher angle of incidence, the lower the frequency required. For Near-Vertical incidence frequencies of 3.5 Mhz to 7 Mhz are generally used. These frequencies have very long wavelengths and so antennas have also to be very long, and to achieve the near vertical transmission effect, those antennas must be horizontal. Basically the more manageable 7Mhz frequency requires an antenna 66ft long! Not portable at all. But anyone with a small garden could rig up the required horizontal length on top of garden fence and get viable results. This sort of antenna is a great Bug-In Antenna as its very effective, and very low profile.

Diverting a little, but on the subject of emergency bug-in antennas: Since a week ago, I've been bugged-in at our bug-out. After the foul winter, the experimental emergency coms antenna that I put up a year ago by literally throwing into a nearby tree from an upstairs window, is still in place, and still performing fine. For bug in application, simple end-fed wire antennas are worth considering as they discreet and effective.