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The VHF Pre-amplifier is built in a FLEXI-BOX on a dedicated PCB. The box has one 50Ω input and one 50Ω output. It is intended as a test measurement aid and could also be part of a VHF radio installation. The DC input can be fitted with a feed through capacitor with a solder tag, or a standard DC Connector for a 7.5 Volt mains power adaptor. The RF connectors can be selected from BNC, N and SMA. They could also be Belling Lee (Television Type 75 Ohms!) or Type F to special order. Other connector types could be fitted if required in quantity. It could therefore be used in many applications that require a VHF Pre-amplifier and is also available as a Remotely Powered VHF Pre-amplifier. We can build and test these at Chemandy with a gain of approximately 13 dB and an output power of approximately +5 dBm, the output ripple is less than + 0.5 dB from 88 MHz to 108 MHz.
The amplifier is built around the BFS17, which is a NPN 1 GHz wideband transistor manufactured by Philips. The datasheet for this device can be obtained at http://www.nxp.com/acrobat_download/datasheets/BFS17_2.pdf The circuit for this amplifier and a description are available at VHF Amplifier Description.
Figure 1
![[Insertion Loss Graph - S21 v Frequency]](../../images/prod111.gif)
Figure 2
![[Return Loss Graph - S11 and S22 v Frequency]](../../images/prod112.gif)
The above results were obtained with SMA connectors and the performance will most probably be inferior with any other type fitted.
A selection of escutcheon drawings are available for downloading as .zip or .bmp files.
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