EME213 9MHz IF Noise Blanker
The Mini-Kits EME213 is a high performance 9MHz IF Noise Blanker with an optional noise antenna input, and is a total rethink on past designs and the ability to effectively blank power line noise without introducing audio distortion. Noise Blanker 1 ( NB1 ) uses the IF noise which is tapped from a 9MHz 100kHz wide input filter that is amplifier by an adjustable high gain amplifier to produce noise pulses. The use of a manually adjusted amplifier instead of a commonly used Automatic Gain Controlled ( AGC ) amplifier reduces audio distortion on strong on frequency or adjacent signals. The noise pulses generated are used to switch a high speed comparator to produce accurately delayed pulses that are used to drive a balanced diode noise blanker gate circuit. The 4.3uS delay through the 9MHz input filter, and the delayed blanking pulses from the comparator allow the NB gate to precisely eliminate the noise without punching big holes in the signal. When using NB2, an optional wide band noise antenna can be connected and the adjustable high gain amplifier then becomes a tune-able receiver between 9 and 13MHz. The tune ability allows the amplifier to be tuned to avoid strong shortwave broadcast signals to a clear band to receive the noise only. The NB2 is very effective against very high levels of power line noise > S9, and when this mode is used there is basically no audio distortion on the signals.
The module is controlled through a single 16 Pin IDC header connector, making it easier to interface to logic circuitry. See the Block diagram for the connections to this module.
The EME213 is a part of the M1 series building blocks to construct a high performance M1 HF Transceiver. The M1 HF Series Kits have been designed to allow easy construction due to the use of mainly leaded components for those that don't like surface mount devices. Modern SMD components are only used when required due to availability of components, or for better performance. The RF modules are all designed with a 50ohm impedance making it easy to interconnect with the other M1 series modules, and your own home brew circuit designs.
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The images below show both sides of the board. The module uses a small number of very tiny SMD devices that could not be avoided as it makes the module more compact and offers better performance.
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