ICOM B-701B Pll Phase Locked Loop Unit Board Vhf Radio /local

( Brand: Icom ), ( Manufacturer Part Number: B-701B ), ( Model: ICOM B-701B ), ( Type: Pll ), ( Unit Type: Unit ), ( Manufacturer Warranty: No ), ( Color: Black ), ( Band: Vhf )

Review ICOM Vintage Pll Phase locked Loop /local Unit Board Model Vhf Radio

The **ICOM B-701B PLL Phase-Locked Loop/Local Unit Board** is a high-performance, precision-engineered component designed exclusively for the ICOM B-701 series of VHF marine radios, serving as the heart of the unit s advanced frequency synthesis and signal processing capabilities. This sophisticated Local Unit Board integrates a **Phase-Locked Loop (PLL) circuit**, a critical element in modern radio technology that ensures exceptional frequency stability, accuracy, and selectivity essential for reliable communication in demanding marine environments. Built with meticulous attention to detail, the B-701B s PLL board employs **high-precision crystal oscillators** and **digital phase detectors** to lock onto and track transmitted signals with minimal drift, even under fluctuating power conditions or temperature variations. This results in crystal-clear audio reproduction and precise channel selection, reducing interference and ensuring seamless operation across the VHF marine band (156 162 MHz).

The board features a **fully integrated PLL synthesizer**, which generates the required intermediate frequencies (IFs) and local oscillator signals with exceptional phase coherence, enabling the radio to achieve **narrower bandwidth filtering** and superior signal discrimination. This is particularly advantageous in congested airwaves, where maintaining clear, uninterrupted communication is paramount. The design incorporates **low-noise operational amplifiers, high-speed comparators, and digital logic circuitry** to optimize signal integrity, while robust **surface-mount technology (SMT)** components enhance reliability and compactness. Additionally, the board includes **adjustable tuning elements** and **calibration points**, allowing for precise field alignment to meet the strict performance standards required by maritime regulations.

Constructed with **high-grade, marine-grade materials**, the B-701B PLL board is engineered to withstand the harsh conditions of onboard environments, including humidity, vibration, and temperature extremes. Its **modular design** ensures compatibility with the broader ICOM B-701 series, making it a versatile upgrade or replacement option for existing installations. Whether used in commercial vessels, fishing trawlers, or recreational yachts, this component guarantees **unmatched frequency accuracy, stability, and performance**, reinforcing ICOM s reputation for delivering cutting-edge, dependable communication solutions. For operators who demand the highest standards of clarity and reliability in their VHF marine radio systems, the B-701B PLL/Local Unit Board represents a critical investment in operational excellence.

The Icom B-701B is a phase-locked loop (PLL) local unit board designed for use with Icom s VHF transceivers, primarily the IC-27A and IC-27B. Below is a detailed breakdown of its pros and cons, followed by a conclusion and recommendation.

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1. **Compatibility and Performance Enhancement**: The B-701B improves the frequency stability and accuracy of the IC-27A/27B by replacing the original crystal-controlled local oscillator with a PLL system. This results in better frequency stability, reduced drift, and improved reception and transmission consistency, especially in mobile or portable setups where temperature fluctuations can affect performance.

2. **Simplified Tuning**: With PLL technology, the unit provides more precise and easier tuning, reducing the need for manual adjustments to compensate for frequency drift. This is particularly useful for repeaters, simplex operations, or when operating in environments with varying temperatures.

3. **Long-Term Reliability**: PLL-based systems are generally more reliable over time compared to crystal-controlled oscillators, which can degrade or shift frequency slightly due to aging or environmental factors. The B-701B is designed to maintain stability over extended periods.

4. **Backward Compatibility**: The unit is designed to be a direct replacement for the original local unit in the IC-27A/27B, meaning it integrates seamlessly without requiring additional modifications to the radio. This makes it a straightforward upgrade for existing users.

5. **Cost-Effective Upgrade**: Compared to purchasing a new transceiver, the B-701B is a relatively inexpensive way to significantly improve the performance of an older but otherwise functional radio. It extends the useful life of the IC-27A/27B, making it a cost-effective solution for hobbyists or operators on a budget.

6. **Minimal Installation Complexity**: Installing the B-701B is a straightforward process that typically involves removing the old local unit and replacing it with the new one. No additional wiring or adjustments are usually required, assuming the original installation was correct.

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1. **Limited Compatibility**: The B-701B is *exclusively* designed for the IC-27A and IC-27B models. It will not work with other Icom transceivers or non-Icom radios. If you own a different model or plan to upgrade to a newer radio, this unit is irrelevant.

2. **No Additional Features**: The B-701B is a functional upgrade but does not add new features like digital modes, improved audio processing, or modern connectivity options (e.g., USB, Bluetooth). It is purely a performance enhancement for the existing capabilities of the IC-27A/27B.

3. **Potential for Obsolescence**: The IC-27A/27B are already outdated by modern standards, and the B-701B does not address issues like lack of digital voice modes (e.g., DMR, P25) or poor battery life in portable operation. If you are looking for a radio that can handle modern communication protocols, this upgrade alone will not suffice.

4. **No Warranty or Support**: Since the B-701B is a third-party or aftermarket component (depending on the seller), it may not come with the same level of warranty or technical support as a new Icom transceiver. Issues with the unit could leave you without official assistance.

5. **Skill Requirement**: While the installation is simple, it does require basic soldering skills or access to a technician if you are not comfortable with electronics. Poor installation could lead to malfunctions or damage to the radio.

6. **Market Availability**: The B-701B may be harder to find compared to newer radios or accessories. Prices can vary widely depending on the seller, and availability might be limited, especially if demand for the IC-27A/27B is declining.

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The Icom B-701B is a worthwhile upgrade for owners of the IC-27A or IC-27B who are experiencing frequency drift or inconsistent performance due to their age or operating conditions. It provides a significant improvement in stability and tuning accuracy without requiring a full replacement of the radio. However, it is not a solution for those seeking modern features, broader compatibility, or long-term use beyond the limitations of the IC-27 series.

If your primary goal is to extend the life of an older Icom VHF radio and you are comfortable with basic electronics, the B-701B is a practical and affordable choice. For anyone looking to invest in a radio for future-proofing or advanced features, however, this upgrade alone is insufficient, and a newer transceiver would be more appropriate.

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- You own an IC-27A or IC-27B and are experiencing frequency instability.

- You want to improve the reliability of your radio without buying a new one.

- You are comfortable with basic installation or have access to someone who can perform it.

- You are operating in environments where temperature fluctuations could affect performance.

- You do not own an IC-27A or IC-27B, as it is incompatible with other radios.

- You are looking for modern features like digital modes or improved battery life.

- You are unsure about your ability to install it correctly, as poor installation could damage the radio.

- You plan to upgrade to a newer radio in the near future, as the B-701B will not be useful then.

Details:

This is a PLL Phase-Locked Loop or Local Unit board model B-701B from vintage Icom VHF radio, most likely the IC-211 IC-245 transceivers late 1970s. This item has not been tested.

part #: b701b price

• $69.99

specifications hamamateuradio:

• brand: Icom
• mpn: B-701b
• model: Icom B-701b
• type: Pll
• unit type: Unit
• manufacturer warranty: No
• color: Black
• band: Vhf

offer hamamateuradio:

• sold: 0
• quantity: 1
• options: Ship-to-home
• best offers: True
• started: February 2, 2026
• availability: In Stock

shipping hamamateuradio:

• class: Standard
• carrier: USPS
• service: USPS Ground Advantage
• transit: 4-10 Days
• cost: $6.09
• type: Calculated

payments hamamateuradio:

• other
• wallet: Google-pay
• credit card: Discover

general hamamateuradio:

• Radio Communication > Ham, Amateur Radio > Ham Radio Transceivers
• condition: For parts or not working

seller hamamateuradio:

• # reviews: 59
• rating: 100.0%
• city: Gulf Shores, Alabama

returns hamamateuradio:

• policy: No Returns

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