Hi-Z Input Preamp

NEW!

Interested in a preamp for a small whip or low gain Rx antenna?

Here is a new Hi-Z input amplifier for HF Rx.

This unit is configured with a slight amount of gain to overcome system losses, about +10db. The gain is fairly flat from 1MHz..30MHz. The first stage is a JFET which provides the high input impedance and some gain. It is followed by an NPN emitter follower which provides a low output impedance. The circuit works well with +12VDC applied.

The standard configuration is for Power-Over-Coax. This is important for remotely mounted preamps as using unshielded cable for power acts as antenna for noise and undesired broadcast signals.

Power over Coax (PoC) or direct +12V DC input. A "bias T" is available to feed +12V up the coax.

This PCB allows a variety of configurations to fit you needs. There are 3 jumpers on the PCB to allow:

First stage: Common source amplifier
Second stage: Emitter follower
Power-Over-Coax or direct +12V

Purchasing Options:

Default configuration is Power-Over-Coax.

All SMD's assembled $15 (no case or coax connectors)
All SMD's assembled, + 50mm case + 2x SMA female bulkhead connectors (not installed). User needs to install connector and drill the case end plates. $20
Fully assembled with SMA output connector and completed case. SMA for input supplied but not installed. $25
If you want another configuration, please email.

Please select an option from the menu below: Note: Bias T sold separately.

Preamp Schematic

This is a 2 stage preamp with about 10db of gain in the FET stage. The default configuration is Power-Over-Coax, which requires a Bias T (available separately).

For independent power, you need to make a cut at JP3 and verify that DC power is NOT going to the radio.

PCB

Here is a blow up of the PCB. This fits into a 50 x 25 x 25mm extruded aluminum enclosure.

Coming Soon - Frequency gain plot

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