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Highfields Amateur Radio Club
Constructors Corner.
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A simple RF Sampler.

A useful piece of test equipment for any radio amateur is a device that lets you connect a frequency counter or an Oscilloscope to the RF output of your transmitter. This project is for such a device. The original circuit was noted as able to handle up to 200 Watts at a frequency range of 1.8 to 450 MHz.

Parts List:

C1 = 5pf 1kv.

D1, D2 = 1N914.

R1 = 50Ω 5% ¼Watt.
(I've had emails asking where a 50Ω resistor can be obtained. The E12 series has 47Ω as the nearest, this would do the job (if you have several you could test each one and select the closest to 50Ω) or you could parallel 2 100Ω to make 50Ω)

J1, J2 = Your preferred coaxial sockets (BNC is usually a good choice).circuit layout

B1 = Metal box.

Ring terminals.

Nuts and bolts to suit.

Method:

1: Mark out and drill the holes to mount the coaxial sockets at opposite ends of the box.

2: Mount the sockets onto the box, ensuring a good electrical contact between socket outer and the box. This is important as the box is the 'ground' connection.

3: Using the hook up wire (if required) to mount the other components as shown. Solder the ground connection of the diodes to a ring terminal (you can solder the ends together and extend with hook up wire) and fix to either a socket mounting bolt or drill a hole in a convienent location and bolt to the box.

4: Before closing the box ensure that the likelyhood of short circuits is negated. The use of some insulating tape may be required, but if you keep all the leads as short as possible all should be well. Also mark the outside of the box Input at J1 and Output at J2.

Layout:

On the right is the general layout.



connection diagram

To Use:

Referring to the diagram above, connect it up to a 'T' coaxial adptor to suit your connections, the transceiver under test and a dummy load.

Connect your oscilloscope or frequency counter to the output.

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