8

Assuming that the two transmitters operate at the same carrier frequency, and that the receivers receive similar power from each transmitter, then the FM signals will suffer destructive interference and the demodulated signal will be heavily distorted. PL tone, which is part of the transmitted signal, will also be lost. If one of the RF signals gets to the ...


8

You could get several different results, depending on exactly how the receiver recognizes the expected tone. From a small amount of web research, it sounds like the usual methods are either a filter passing only the expected tone, or a frequency counter which determines the frequency of the tone in the signal which is then compared with the expected tone ...


7

"Tone", displayed as "T" on the main screen, selects tone encoder + carrier squelch (your HT will send a tone, selected by the TONE Freq menu, and receive any strong-enough signal, regardless of whether it has a tone.) The transmitted tone is necessary to "open up" most repeaters so that you can talk on them. "CTCSS", displayed as "CT" on the main screen, ...


7

I would expect some low-frequency roll-off in the amp and the speaker. You could check by putting headphones on the speaker output. Wikipedia says that a 300 Hz cutoff high-pass filter is common. https://en.wikipedia.org/wiki/Continuous_Tone-Coded_Squelch_System Also, the CTSS tone is injected at a lower level than the voice content, usually 15% of full ...


6

The ratio between PL tones is roughly constant. From a list of PL tones, you can calculate the ratio between each frequency, which turns out to be about 1.035 (with some exceptions, not sure why). Using a constant ratio rather than a constant difference avoids two different tones being exact multiples of each other. If you used a constant difference of 10 ...


5

DCS (aka DSQ/DPL) provides a slightly larger range of codes to pick from compared to CTCSS. This means less chance that a nearby station will accidentally overlap with yours. Specifically, DCS gives you 83 codes, whereas CTCSS gives you somewhere between 26-50 squelch tones depending on the radio -- manufacturers have added extra codes over time. For ...


4

Greg Hewgill's answer is correct, but merits a slight explanation. Constant (percentual) relations mean that the Q-factor of the detector for the tones remains constant. Most detector chips (like the old NE567) and algorithms are designed for a single Q, and the frequency changes don't change the Q. Distortion is quite normal in electronics — low tones like ...


4

As Michael noted, a repeater's CTCSS system is looking for a very specific frequency with a very low deviation (typically 10% or less) as low as about 40 dB down. What you are hearing is of course the whole audio range. The decoder in a CTCSS system is based on a very narrow bandpass filter which passes the desired CTCSS tone. There is a balance between a ...


4

The BF-888S radios have a 16-channel knob on the top and no LCD display nor a number keypad. The BF-888S is marketed all over the world for use mostly in licensed commercial operation or licensed Amateur Radio. The BF-888S can be programmed to use frequencies in the range of 400 to 470MHz which nicely permits programming the radios for the 70cm Amateur ...


4

You cannot limit others from using a channel. But as long as you have a license then you can operate anywhere in the band in question, and there are a lot of underutilized frequencies. Just be sure to ID at the start of your transmission and every 10 minutes if it goes on longer than that. Privacy is relative, though. Someone with a scanner might catch ...


3

Here on StackExchange we call what you asked an XY problem. You're asking how to set up CTCSS, but what you really want is to have privacy. Those are two different things. First of all, a tiny bit of theory about CTCSS. The name means Continuous Tone-Coded Squelch System. It's not a privacy system, it's a squelch system! It works by sending a tone-code ...


3

There is a way to use radio waves to hold a private conversation. It's called a mobile telephone, and they are available with surprisingly good coverage around the world. We should always use a tool appropriate for the task at hand. Amateur radio is not suitable for the use case you are describing, and a mobile phone is.


3

Your understanding of tone squelch is wrong. Tone squelch is simply an extension to the squelch system. Normally, the squelch opens whenever the received signal is stronger than the squelch threshold. With a tone squelch (and I use that term broadly here to refer to CTCSS, DCS and any other possible, similar schemes) configured for receive squelch, the ...


2

No, you can't. Based on the particular method the receiver uses to decode CTCSS, multiple tones may or may not be recognized. But that's moot, because you can't transmit all the tones anyway. CTCSS adds a low frequency tone to the baseband input to the FM modulator. Standards vary, but the amplitude of this tone is around 15% of the deviation. The amplitude ...


2

No. It is not legal. You may not hide the content of your message when making use of amateur frequencies, no matter what means you use to do so. Technically, all you would need is radios supporting a digital voice mode that includes encryption, but I can't name one that would definitely work simplex (e.g. P25 can be encrypted but is as far as I know always “...


1

This might be crazy, but you were on the TX band when you attempted to TX? You should have continued to hear the downlink of you were. Sinfulness it is the simple things. Also, if it was during the last few days, you could have been doing everything correctly but being stomped out by stronger stations. I assume you are just starting out with satellites, ...


1

It could be a bug in the repeater controller (it's perfectly possible to transmit digital data with a PL tone), but I'd suspect the Baofengs as your problem. They're not the best radios, and they're priced accordingly. Borrow a better HT (ideally Icom, Yaesu or Kenwood, but Alinco makes pretty good handhelds too although they're harder to find) and see if ...


1

They may not be transmitting a tone at all. I had this with my Baofeng and a local club repeater I wanted to access. They only receive the tone but do not transmit it because then others would know what it is and could use it without paying dues to the club. The school may be of the same mind.


1

So, you mean something that will give you the sequence of calling tone digits like used in ZVEI1 to ZVEI5? Yeah, those were fun 5 minutes: I got an example from the sigid wiki (specifically ZVEI1-5), converted it to mono WAV (it's stereo for some unclear reasons), and built this flow graph in GNU Radio companion from scratch: What is missing is a lookup ...


1

I would use the application Mathematica (by Wolfram) which has a lot of computational audio features for decoding audio streams via a given codex protocol. Mathematica is not for everyone and as the name suggests it is a very mathematically oriented application. Plus, it is something you have to buy yet there is a free trial period you could use to ...


1

multimon-ng, which I have used for other purposes, claims to be able to decode selective calling tones of the following protocols, among other things: ZVEI1 ZVEI2 ZVEI3 DZVEI PZVEI EEA EIA CCIR However, I tried it out with a couple of sample files I found on the Internet and it didn't produce any output.


1

The best way to use a Baofeng to communicate with any walkie talkie is to: Find the frequency. Make sure you are on the right frequency by transmitting from the midland walkie talkie to your Baofeng. Run a tone decoder. In the option "R-CTCS", the bafeng has a tone decoder by pressing either the # button or the * button. When the tone decoder is running, ...


1

Digital Coded Squelch will not cut any noise out of analog FM transmissions, and it will NOT "add an extra layer of image and interference rejection", DCS is not some kind of RF magic - it is simply a 'digital number sequence' imposed on the audio and it itself is a form of audio which is filtered out of the speech part of the audio. Yes, DCS is ...


1

DCS uses a rotating series of codes like 257257257257 which in this case is 257 repeated continually. CTCSS uses a sub audible single tone like say 100 hz. Once a CTCSS squelch is open, wide band noise like intermod or computer hash can keep the squelch open after the transmitted carrier when its sub audible tone stops, resulting in unwanted noise at the ...


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