重要接收设置 11 CHAPTER Important Receiver Settings
本章要点：FTX-1 把接收链路里最常用、也最直接影响听感的几项调理功能集中在屏幕底部，触摸即可切换。本章逐项说明 ATT （衰减器）、IPO（截获点优化）、AMP（射频放大器）、DNF（数字陷波滤波器）与 AGC（自动增益控制）的作用、可用档位 与适用波段，并给出「什么现象该调哪一项」的判据表与弱信号 DX 接收的取舍建议。
接收过程中各项重要操作的状态显示在屏幕底部。要更改 The status of various operations that are important during 某项设置，触摸显示屏上相应的位置即可。 receive is shown at the bottom of the display. To change a 下列项目即为接收时的重要设置项。它们分别作用于接收 setting, touch the appropriate location on the display. 机前端或中频/音频级，各自适用的场合并不相同。 The items below are the important setting items when receiving. Each of them is applied to the receiver front end or the IF/audio stage, and each is best used in a different situation.
11-1 ATT (Attenuator) · ATT（衰减器）
显示当前 ATT（接收输入信号的衰减量）。当目标信号极 Displays the current ATT (amount of receive input signal 强，或在低频波段噪声电平很高时，可启用衰减器，以衰 attenuation). When the desired signal is extremely strong, 减来自天线的信号或噪声。 or the noise level is high on a low frequency band, activate the attenuator to reduce the incoming signal or noise from 触摸 [ATT] 后，再触摸 "ON" 或 "OFF"。 the antenna. ATT 功能仅在 HF – 50MHz 波段可用。 After touching [ATT], touch “ON” or “OFF”. ATT 按各工作波段独立设置。
The ATT feature is only available in the HF – 50MHz band. The ATT is set independently for each operation band.
判据：当 S 表被邻近广播电台打满、当噪声基底本身（而 Judgement guide: use ATT when the S-meter is pinned by 非某个单独信号）高到让 AGC 被它驱动、或强信号过载 a nearby broadcast station, when the noise floor itself (not 导致声音发糊并产生虚假互调产物时，启用 ATT。在波段 a single signal) is so high that the AGC is being driven by it, 安静、正在追弱信号时，请关闭 ATT。 or when strong-signal overload produces “mushing” and spurious mixing products. Leave ATT off when you are chasing a weak signal and the band is quiet.
11-2 IPO (Intercept Point Optimization) · IPO（截获点优化）
IPO（截获点优化）功能可设定射频放大级的增益，以适 The IPO (Intercept Point Optimization) function can 应所连接的天线与接收信号条件。IPO 可从三种工作状态 establish the gain of the RF amplifier section to 中选择。 accommodate the connected antenna and the received signal conditions. IPO can be selected from three operating 触摸 [IPO] 后，再触摸所需的工作状态。
conditions. IPO 功能仅在 HF – 50MHz 波段可用。 After touching [IPO], touch the desired operating IPO 按各工作波段独立设置。 condition.
The IPO feature is only available in the HF – 50MHz band. IPO is set independently for each operation band.
表 11-1 IPO 的三种工作状态 Table 11-1 Three IPO operating conditions
档位 电路状态 适用场合 Selection Circuit state When to use
AMP1 接入一级射频放大器，接收灵敏度与特性的 常规接收的默认选择；波段中等拥挤时 均衡表现（增益约 10 dB）
AMP2 两级射频放大器串联，灵敏度最优先（增益 天线效率低、信号极弱、波段安静时；配合小天线野外使用 约 20 dB）
IPO 接收信号不经射频放大器直接送入中频混频 低频波段恶劣信号环境（强广播台、严重互调）时，可大幅改善接 器 收
11.3 AMP（射频放大器） AMP
当接收信号微弱时，提高射频放大器的灵敏度。触摸 Increases the sensitivity of the RF amplifier when the [AMP] 后，再触摸 "ON" 或 "OFF"。AMP 功能仅在 AIR received signal is weak. After touching [AMP], touch “ON” 波段、144MHz 和 430MHz 波段可用。 or “OFF”. The AMP feature is only available in the AIR band, 144MHz and 430MHz band. 因此 AMP 可视为 IPO 选择在 VHF/UHF 上的对应项：波 段安静、目标信号处于噪声附近或以下时启用；一旦出现 AMP is therefore the VHF/UHF counterpart of the IPO 强本地信号，应重新关闭。 selection: use it when the band is quiet and the signals you want are at or below the noise, and switch it off again once a strong local signal appears.
11-4 DNF (Digital Notch Filter) · DNF（数字陷波滤波器）
数字陷波滤波器（DNF）是一种高效的差拍消除滤波器， The Digital Notch Filter (DNF) is an effective beat-canceling 可把接收通带内若干个干扰差拍音调一并陷除。由于它属 filter that can null out a number of interfering beat notes 于自动陷波（Auto-Notch）功能，因此没有与之关联的 inside the receiver passband. Because this is an Auto- 调节旋钮。 Notch feature, there is no adjustment knob associated with this filter. DNF 通过 [FUNC] 旋钮的功能列表开关；启用后即自动工 作，所以当通带内同时存在多个稳定差拍音时，应首先尝 DNF is turned ON/OFF from the [FUNC] knob function list; 试 DNF。 it works automatically once enabled, so it is the first thing to try when several steady heterodynes sit inside the passband at the same time.
注意 · 与 IF NOTCH 的分工 NOTE
DNF 是自动多频点陷波，按下即工作、无需调谐；第 15 章讲的 IF NOTCH 是手动单频点陷波，需要用 [MAIN] 旋钮把陷波点 对准干扰音调。两者可以配合：先用 DNF 灭掉大部分差拍，剩下最顽固的一个再用 IF NOTCH 精确点掉。 DNF is an automatic multi-tone notch: enable it and it works, with no tuning. The IF NOTCH described in Chapter 15 is a manual single- tone notch whose null must be tuned onto the interfering heterodyne with the [MAIN] knob. The two complement each other: let DNF kill most of the beat notes first, then remove the most stubborn one precisely with IF NOTCH.
11-5 AGC (Automatic Gain Control) · AGC（自动增益控制）
显示当前所选的 AGC 设置。AGC 系统用于补偿衰落及其 Displays the currently selected AGC setting. The AGC 他传播效应带来的电平变化。AGC 特性可按各工作模式分 system is designed to help compensate for fading and 别设定。AGC 的基本目标是：一旦信号强度达到某个最低 other propagation effects. The AGC characteristics can be 门限，就维持恒定的音频输出电平。 individually set for each operating mode. The basic objective of AGC is to maintain a constant audio output 触摸 [AGC] 后，再触摸所需的时间常数。 level once a certain minimum threshold of signal strength AGC 可按各工作波段设置。 is achieved. 选择 "AUTO" 时，机器会按接收模式自动选取最优的 After touching [AGC], touch the desired time constant. 接收恢复时间。 AGC can be set for each operation band. The “AUTO” selection mode selects the optimum receiver-recovery time for the reception mode.
表 11-2 AGC 时间常数的选择 Table 11-2 Selecting the AGC time constant
档位 菜单项 可调范围 推荐用法 Selection Menu item Adjustment range Recommended use
AUTO （屏幕直接选择） — 日常通联首选；由机器按接收模式自动选取恢复时间
FAST AGC FAST DELAY 20 – 160 – 4000 (msec) CW、竞赛快速抄收、信号强度变化剧烈的场合
MID AGC MID DELAY 20 – 500 – 4000 (msec) SSB 通联、一般 DX 呼叫的通用档
SLOW AGC SLOW DELAY 20 – 1500 – 4000 (msec) 数据模式（DATA / RTTY / PSK）、追求平稳听感的 SSB 守听
上表中的延迟值对应菜单项 [AGC FAST DELAY] / [AGC The delay values above are the menu items [AGC FAST MID DELAY] / [AGC SLOW DELAY]，可在各模式菜单下 DELAY] / [AGC MID DELAY] / [AGC SLOW DELAY], which 以 20 msec 步进细调。菜单表中加粗的中间值为出厂默认 may be fine-tuned in 20 msec steps under each mode 值。 menu. The bolded centre value in the menu table is the factory default. 实用建议：CW 选 FAST，使增益在字符之间完成恢复，能 跟上快衰落中的信号；SSB 选 MID，避免音节式的音量抽 In practice: choose FAST for CW so that the gain recovers 动；数据模式选 SLOW，使短促噪声脉冲不会在一次发射 between characters and you can follow a station through 中途把接收机压死。 fast fading; choose MID for SSB so that syllabic pumping is not heard; choose SLOW for data modes so that a short noise burst does not desensitise the receiver in the middle of a transmission.
表 11-3 接收链路调理速查表 Table 11-3 Receiver chain quick-reference (symptom → what to adjust)
你遇到的现象 该调哪一项 建议动作 Symptom What to adjust Suggested action
S 表被强台打满、声音发糊、出现幻影信号 ATT 打开 ATT；仍过载则把 IPO 设为 IPO 档
低频波段噪声基底整体很高、听不清弱台 ATT / IPO 先开 ATT；若噪声来自强广播台造成的互调，改用 IPO 档
波段安静、目标信号弱到几乎听不见 IPO / AMP HF – 50MHz 用 AMP2；AIR / 144MHz / 430MHz 打开 AMP
通带内有多个稳定差拍音（吱吱声） DNF 打开 DNF，自动多频点陷除
只剩一个顽固单音差拍 IF NOTCH 用第 15 章的 IF NOTCH 手动对准
信号忽大忽小、衰落严重 AGC 调慢一档（FAST → MID → SLOW）
SSB 音量随音节一鼓一鼓地抽动 AGC 由 FAST 改为 MID 或 SLOW
CW 抄收时跟不上快衰落 AGC 改为 FAST，或缩短 AGC FAST DELAY
HAM 实战 · 弱信号 DX 接收时 ATT / IPO / AMP 的取舍 FIELD NOTE
追 DX 弱信号时最常见的错误是"一律把增益开到最大"。正确顺序是：①先在 AMP1 下听，如果目标信号只是比噪声略高、且 没有强邻近台，再切到 AMP2（约 20 dB 增益）；②如果切到 AMP2 后背景"沙沙"声抬高幅度明显大于目标信号的抬高幅 度，说明你放大的主要是天线噪声而不是信号，此时应退回 AMP1 或直接切 IPO，改用更好的天线而不是更多增益；③160m / 80m 夜间遇到广播台互调产生的"鬼影"时，IPO 档往往比 ATT 更有效——ATT 把信号和噪声一起衰减，IPO 则从根本上消 除放大级产生的互调；④遇到强台把 S 表打满、且目标弱台就在其附近几 kHz 时，先开 ATT 压住整体电平，再配合 IPO，通 常能同时保住动态范围与弱信号可读性；⑤AIR / 144MHz / 430MHz 波段没有 IPO，只有 AMP 开关，判断方法同上：安静 波段开 AMP，强信号环境关 AMP。（社区经验） The most common mistake when chasing weak DX is “always run maximum gain”. The correct order is: (1) listen first on AMP1; only if the target is barely above the noise and there is no strong neighbour should you move to AMP2 (about 20 dB gain). (2) If switching to AMP2 raises the background hiss noticeably more than it raises the target signal, you are amplifying antenna noise rather than signal — go back to AMP1 or to IPO, and improve the antenna instead of adding gain. (3) On 160 m / 80 m at night, when broadcast-band intermod creates “ghost” signals, IPO is usually more effective than ATT: ATT attenuates signal and noise together, while IPO removes the intermodulation generated in the amplifier itself. (4) When a strong station pins the S-meter and the weak target sits only a few kHz away, engage ATT first to hold the overall level down, then combine it with IPO; this normally preserves both dynamic range and weak- signal readability. (5) The AIR / 144 MHz / 430 MHz bands have no IPO, only the AMP switch — apply the same test: AMP on for a quiet band, AMP off in a strong-signal environment. (community-reported)