Common knowledge of using sub tones, reverse frequencies, and direct frequencies in walkie talkies: Sub tones in walkie talkies are divided into two types: transmitting sub tones and receiving sub tones. In order to be able to access the relay, it is necessary to use the transmission of sub tones in order to open the relay. And the relay itself chooses to "accept sub tones", signals without sub tones are excluded. Some of the signals relayed do not contain sub tones, but there are also signals with sub tones.

Similarly, when accepting oneself, in order to exclude signals that one does not need to hear, one can also add accepting consonants. In this way, the agreed upon sub tones can also be used between two (or several) radio stations to eliminate external interference signals.

Although it is said to be a sub tone, it can actually be heard, especially when the sub tone is set at the high limit (near 250Hz) or when the low-frequency response of the receiver is relatively good. Therefore, when setting the sub tones, we try to set them as low as possible to avoid unnecessary interference.

Another type of consonant is DCS (DigitalCoded Squelch), which belongs to the category of digital consonants. Motorola calls it DPL and has 104 consonant points (DPL is less). It is more advanced and uses digital encoding methods to transmit before and after speech. This type of sub sound can only be emitted and accepted simultaneously (i.e. cannot be set to only emit and not accept).

Misconception: When emitting sub tones, the receiver only needs to set it to sub tone reception in order to accept them.

In fact, it's exactly the opposite. When transmitting sub tones, the receiver must set it to "non sub tone acceptance status" to be able to accept them. When setting it to "sub tone acceptance status", it is necessary for the sub tone types and codes to be common in order to be accepted.

Inverted frequency of walkie talkie

The so-called intercom frequency inversion refers to a communication method in which one party does not use the relay when using it, but reverses the two transmitting and receiving frequencies used by the relay. Also known as "inverse frequency".

The reverse frequency of walkie talkies has a direct signal (without relay) and does not alter the other party's use of relay, making it suitable for direct communication tests without the other party's awareness.

For example, if the uplink frequency of a certain relay is 434M and the downlink frequency (i.e. listening frequency) is 439M, then after selecting the reverse frequency, we will use 439M for reception and 434M for transmission. In this way, directly listening to the uplink frequency of the other party's walkie talkie instead of the frequency coming down from the relay, the other party's walkie talkie receives the direct frequency and not the frequency coming down from the relay, because the relay was not opened at the time of transmission.

The advantage of doing so is that the other party can still use the relay method without changing any settings, while also being able to experiment with the direct connection between the two frequencies. Inverted frequency is often used to check the strength and quality of the other party's uplink signal.

The weakness of this approach is that as long as one party's signal is presented in the relay, it appears quite strange. But if the listeners are close to the frequency reversal users, they can receive direct frequency transmissions at the same time. Generally speaking, if the reverse frequency communication is found to be very smooth, it can be changed to direct frequency communication and the relay can be released.

Some walkie talkies are equipped with shortcut keys for the convenience of reverse frequency operation, making it easy to use reverse frequency during relay operation.

Direct frequency intercom

The so-called walkie talkie direct frequency refers to two radio stations using the same frequency for communication. The direct frequency communication of walkie talkies has the characteristics of good signal (without relay), small impact scale, no interference to relays, and no modification to relay listening, making it suitable for close range communication.

For example, if the uplink frequency of a relay is 434M and the downlink frequency (i.e. listening frequency) is 439M, then the direct frequency is 439M used for both receiving and transmitting walkie talkies. After one party chooses direct frequency, they should advocate for the other party to also switch to direct frequency. Otherwise, although both sides can communicate, the other party's signal is relayed and still affects the overall situation, making it sound strange as long as one party speaks. When both sides are using direct frequency, the relay signal is still being monitored during the interval of the walkie talkie conversation.