SHF Elektronik Mini-xx Mast preamplifier 2m or 70cm

The amplifiers are simply looped into the coaxial cable. Power is supplied either by remote feeding via the coax cable or via a separate line. Most modern transceivers have a built-in remote feed for mast preamplifiers, so in these cases no remote feed crossover is required. Otherwise, various remote feed crossovers with and without sequencer are available.

Alternatively, the amplifiers can be supplied with operating voltage via a separate line. In this case, care must be taken to choke the supply line well in order to avoid interference and high induction voltages.

The amplifiers have a built-in HF-VOX, which ensures safe operation at normal power levels. For higher transmit powers, direct PTT control is required. This can be done directly from the radio or via sequence control. Especially important is a low noise figure with a good 3rd order IP, this is the prerequisite for high

large signal immunity. With most preamplifiers the gain is adjustable. This ensures that the receiver is not overdriven and yet the cable losses are effectively overcome.

For transmit-receive switching, the larger models use real coaxial relays, the 'Mini' series from the manufacturer SHF-Elektronik uses print relays. The amplifiers are built into a double-shell, weatherproof housing: Inside an RF-tight tinplate housing, outside a UV-resistant, seamless plastic housing with mast clamp. A clamp for mast mounting is included.

The preamplifier should be mounted as close as possible to the antenna to keep the cable as short (and thus the attenuation as low) as possible. The connection cable between VV and antenna should be as high quality as possible.

2m/144MHz is of the VHF/UHF bands certainly the most used, whether for Tropo-DX, EME, Meteor-Scatter or also FM. And at the numerous contest dates the band is really full. Here a Mast-VV is worthwhile in any case. Due to the sometimes very thick contest signals on 2m, a good large signal strength is essential.

On 70cm/432MHz there is less operation, but because of the higher cable attenuation a preamplifier is even more important. An adjustable gain becomes less important on this band, because there are not so many so very strong signals, on the other hand the cable attenuation is much higher.