Ramsey FM100B FM Transmitter: Difference between revisions
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== MRF557 == | == MRF557 == | ||
The standard Ramsey FM100B kit does include the MRF557 transistor (Q6) as part of its final amplifier stage. The GAL5 IC (U6) functions as the exciter/driver, generating the modulated VHF signal and delivering a low-level output (a few milliwatts) through a 0.001 µF capacitor to the base of the MRF557. The MRF557 then provides the necessary gain and buffering through the PI network to achieve the FM100B’s standard output of approximately 25 mW, compliant with FCC Part 15 regulations. The notion that the MRF557 is omitted in the standard model is a common misconception; it is an integral component in the standard configuration, not just in the optional 1W high-power upgrade (FM100BEX). | |||
The MRF557 is | |||
[[Category:Electronics]] | [[Category:Electronics]] | ||
Revision as of 20:13, 28 November 2025
Operation
To change the broadcast frequency on your Ramsey FM100B:
- Press and hold both FREQ UP and FREQ DOWN buttons simultaneously (this enters frequency setup mode).
- Release the buttons.
- Use FREQ UP to increase the frequency or FREQ DOWN to decrease it (in 100 kHz steps, 88.0–108.0 MHz range).
- Tune a nearby FM radio to the desired frequency and adjust until you hear the carrier (quieting signal; no audio input needed).
- Press FREQ UP and FREQ DOWN together again to exit and lock the frequency.
MRF557
The standard Ramsey FM100B kit does include the MRF557 transistor (Q6) as part of its final amplifier stage. The GAL5 IC (U6) functions as the exciter/driver, generating the modulated VHF signal and delivering a low-level output (a few milliwatts) through a 0.001 µF capacitor to the base of the MRF557. The MRF557 then provides the necessary gain and buffering through the PI network to achieve the FM100B’s standard output of approximately 25 mW, compliant with FCC Part 15 regulations. The notion that the MRF557 is omitted in the standard model is a common misconception; it is an integral component in the standard configuration, not just in the optional 1W high-power upgrade (FM100BEX).