G4HUP 4 Way Distribution Amplifier Page

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Performance Figures

General Purpose 4 Way Distribution Amplifiers

DA1-4 Manual - including circuit descriptions, typical performance, circuit diagrams and PCB overlays etc - click here

The DA1_4 provides a 4 way split from a RF input signal down to approx 1MHz, and is usable up to around 1.8GHz. As supplied the kit contains attenuator components to configure the gain of for standard 10MHz operation from a nominal +10dBm source. There are five attenuator positions available within the unit:

All attenuators are Pi types - suitable resistor values can be looked up from the table

There are no frequency shaping components in this amplifier, so it is broadband - however, it would be easy to implement lowpass Pi filters in place of one or more of the attenuators, using 0805 size L and C elements. Such filters, and isolation transformers, can often be found in old ISA ethernet cards - see this link for some excellent guidance notes!

The architecture of this unit is a resistive splitter (4 way) followed by individual MMIC amplifiers.

An extra feature is the option to provide 5v/80mA power feeding from the input socket, enabling it to be used as a GPS antenna distribution unit, for connecting a single GPS active antenna to multiple GPS receivers. In this application the coupling capacitors throughout are decreased in value, and the gain per channel is approx -1dB nominally.

Typical gain per output at 100MHz is 5dB nominal, and it should be noted that at higher frequencies there may be some variation in level between outputs, however, internal track lengths have been equalized very closely.

Important

Please note that no connectors are supplied with the kit - BNC connectors are more convenient for 10MHz applications, whilst SMA may be better for higher frequency work. Remember to mount the PCB higher up the box if using BNC connectors!

Performance

Thanks to the excellent test equipment available at Mid Atlantic States VHF Conference 2009, more detailed measurements have been possible than I can make in my workshop. Specifically, the 'added' phase noise of the unit, and the differential phase and gain at 10MHz (ie the difference in phase or gain between the output channels). The phase difference measured was +/- 0.4dB, and the variation in gain was +/- 0.05dB. These figures were taken on a R&S Network Analyser. The 'added' phase noise was measured on the R&S FSUP Signal Source Analyser, which has a built in 10MHz reference (also used as the DA input for the gain and phase measurements above). In the graph below, there are two traces - the first (blue) was a capture of the phase noise of the source alone, while the second trace (black) was with the source run through the DA. As you can see, there is very little difference between the traces, indicating a very low added phase noise contribution from the DA.

Excess phase noise introduced by DA1-4L
DA1-4 gain comparison from 10 to 1800MHz. Mkr at 1297MHz
Output phase variation at 10MHz
DA1-4G with SMA connectors
DA1-4L with BNC connectors
Internal view of DA1-4L

The gain measurements shown above are with 0dB attenuation configured in the module, and 0dBm nominal input level. For the LF version, the gain at 10MHz is approx 5dB per channel, dropping to approx -1dB per channel at 1.5GHz.

All unused outputs should be terminated in 50R for correct performance.

For kit availability and price please see the Orders page.

Page created: 29.07.2008

Last updated: 4 Oct 2009