CHEMANDY ELECTRONICS Suppliers of the unusual

HF Amplifier in Original Size FLEXI-BOX


High Frequency Amplifier 300 KHz to 50 MHz
Gain 14.4  dB ± 0.3 dB
Gain Ripple < ± 0.2 dB
Output Power > 11 dBm @ 1 dB compression
Return Loss > 20 dB
Impedance 50 Ohms
Supply 7.5 Volts @ 66 mA
Box Dimensions
63.5 mm x 50 mm x 30.5 mm


From GBP £26.36 + Connectors
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The price of the HF Amplifier FLEXI-BOX is dependant on the connectors required. To find the price for your connector preference or to make a purchase, select your connector requirements in the boxes beside the photograph below and then hit "Add to Cart". 



 [Photograph of HF Amplifier Box showing connectors] 


The High Frequency amplifier is built in an Original size FLEXI-BOX on a dedicated PCB. The screened box has one 50Ω input and one 50Ω output. It can be used as a test measurement aid or a general purpose HF amplifier. The DC input is fitted with a feed through capacitor with a solder tag. The RF connectors can be selected from BNC, N, SMA and TNC. Other connector types could be fitted if required in quantity. It could therefore be used in many applications that require a HF amplifier not just in the lab. We can build and test these at Chemandy with a minimum gain of 14 dB and a 1 dB compression output power of greater than +11 dBm at 30 MHz, the gain ripple is less than ± 0.2 dB from 3 MHz to 30 MHz. Input and Output return loss better than 20dB.    


   The amplifier is built around the BFS17 in a shunt series pair configuration. A full description of this amplifier and how we built the prototype is available at Building a HF amplifier in a FLEXI-BOX Part 1. This article shows several photographs of using the FLEXI-BOX for circuit development. The amplifier is referred to as being an HF amplifier but it can be seen in Figure 1 that the 3 dB frequency response is far wider than the HF band and it could also be used as a LF amplifier or a MF amplifier.

Figure 1

[Gain Graph - S21 v Frequency]

Figure 2

[Return Loss Graph - S11 v Frequency]

The isolation S12, has been omitted because it is better than -65 dB from 0.3 MHz to 50 MHz and would cramp the scale of the other measurements.

The above results were obtained with SMA connectors and the performance will most probably be inferior with any other type fitted.

 This test aid is available Ready Built or in Kit form. The Kit contains the hardware only; i.e. box, pcb, connectors, screws etc. Components are not included because they are surface mount and  it is impossible to supply the correct amount because of the 'ping' factor. Anybody who has fitted surface mount components will know that when a component is being placed with a pair of tweezers there is often a 'ping' and the component disappears into thin air. We would have to supply at least two of every component thus doubling the cost.

A selection of escutcheon drawings are available for downloading as .zip or .bmp files.