CHEMANDY ELECTRONICS Suppliers of the unusual

Original Size FLEXI-BOX Remotely Powered VHF Pre-Amplifier 88MHz to 108MHz

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     The Remotely Powered VHF Pre-amplifier is built in an Original size FLEXI-BOX on a dedicated PCB. The box has one 50Ω input and one 50Ω output. It is intended as a general purpose VHF amplifier and could be used in a VHF radio installation or for boosting low level signals. The input power is sourced from the center conductor of the co-axial cable, thus avoiding the need to have a nearby power source or an additional power supply cable. This amplifier is intended to be used with the Bias Tee FLEXI-BOX. 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 not just in the lab. The remote power facility allowing it to be placed near to the receiving antenna where mains supply may be unavailable, such as a loft or cupboard. Although robust and well screened the FLEXI-Box is not intended for outdoor installation and this would require a weatherproof enclosure.  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.

Circuit

   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.datasheetarchive.com/  The circuit for this amplifier and a description are available at VHF Amplifier Description.

Figure 1

[Gain and Isolation Loss Graph - S21 and S11 v Frequency]

Figure 2

[Return Loss Graph - S11 v Frequency]

      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.

Pricing

    The price of the Remotely Powered VHF Pre-amplifier FLEXI-BOX is dependant on the connectors required. For an automatic quote or to make a purchase, select your connector requirements in the boxes beside the photograph below and then hit "Quote/Purchase".

   [Photograph of VHF Preamplifier Box showing connectors]   

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