SHF Mast preamplifiers 6m - 13cm

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Top Features

  • Weatherproof housing
  • Built-in HF VOX

Supply Scope

  • MVV VOX Mast Preamplifiers
  • Mounting bracket
  • Mounting material
  • Operating instructions German, English (including wiring diagram and assembly instructions)
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. A low noise figure is particularly important with a good 3rd order IP, this is the requirement for high large signal strength. 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. Most amplifiers (except Mini 2) 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 preamp and antenna should be as high quality as possible.

The MVV xx/2 models have two antenna connections, which can be switched via an additional signal. For example, the preamp can be switched between a horizontal Yagi and a vertical omnidirectional antenna. For switching, a switching signal (0V / 13.5V) must be supplied via a separate control line, the required connector is included. The supply voltage could also be fed via the same socket, alternatively the supply is done via the coaxial cable. 
Without power supply all preamplifiers of the manufacturer SHF Elektronik (MVV-xx models) switch to 'pass-through'. This prevents damage to the amplifier even in the event of a power failure.

Even if the cable attenuation on the 4m and 6m bands is not as high as on 2m, the antennas are larger and therefore the gain is smaller - this can be compensated well with a preamplifier. The activity on 4m and 6m is strongly dependent on the ionosphere - with Sporadic-E you hardly find a free frequency on 6m, in normal conditions it is much quieter. The pre-amp should have good large signal strength for the sometimes strong signals.

2m/144MHz is certainly the most used of the VHF/UHF bands, no matter if for Tropo-DX, EME, Meteor-Scatter or FM. And at the numerous contest dates the band is really full. Here a mast preamp 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.

The model MVV 2000 VOX is a broadband mast preamplifier for the amateur radio bands 2m, 70cm and 23cm, and with some limitations also usable on 13cm. Good gain of about 20 dB over the frequency range from 90 to 2000 MHz. This means that the preamplifier can also be used for broadcasting, aeronautical radio (also ADS-B!) or DAB+ and DVB-T. 
Technical Data
Product Name SHF Mast preamplifiers 6m - 13cm
Supply Voltage [V] 13.8 V
Connector A N Socket
Connector B N Socket
Brand SHF Elektronik
Max. Mast Diameter [mm] 56

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