SteveShannon

@Blaise, So, I finally installed Rattlegram. Everything you said is exactly what they represent. I don’t understand how the speakers and microphones in smartphones can transduce ultrasound, much less the speakers and microphone in a two way radio. I also don’t understand how the radios modulate signals in the ultrasonic range. I’m intrigued.

Yeah, but I’ve kinda been wanting to pick up an Android tablet for ham radio anyway.

Fascinating. I haven’t loaded the app yet. My iPad says it’s too old and I don’t load test apps on my iPhone usually. I probably need to pick up a couple inexpensive Android tablets to play radio.

I’m not questioning you, please don’t take it as a personal attack. We see too much of that. Here’s why I’m questioning what really happened. Because we use FM the frequency of the RF signal varies with the frequency of the audio which modulates it. But the government (and courtesy) stipulate how much bandwidth we’re allowed. For FM stereo broadcast transmitters are allowed a wide bandwidth so they can broadcast a wider audio spectrum. But two way radios is only expected to reproduce speech. In fact I would expect our radios to have a filter between the microphone and the modulator to avoid creating too wide of a bandwidth. I would also expect that neither the speakers nor microphones on the inexpensive radios to be able to reproduce ultrasound. I thought I read in their PDFs, that Ribbit attempts to send digital data by converting data into audio tones that are in the center of the spoken voice audio spectrum, between 500 Hz and 2500 Hz. Their centerpoint is 1500 Hz and they go 1000 Hz either side. 20,100 Hz is way above that, but 2100 Hz is right in there. If you were able to transmit at 20100 Hz, I would be interested in what an RF spectrum analyzer would measure. But, I always say you can’t argue with empirical evidence, so I’m trying to understand what really happened.

UncleYoda, Ribbit is an application that sends text messages between two smart devices using two way radios. The smart devices emit an audio tone that’s picked up by the radio’s microphone. A burst of white noise is emitted first to activate squelch at the other end, but at the sending end the person pushes the PTT. At the receiver end the radio speaker reproduces the sound for the smart device to translate into the text message. No cables or modems are involved. A Talkpod is a just another brand of two way radio.

No, that is not supposed to . How did you measure the audio frequencies? Edited to add: I don’t know if you saw the other thread where Ribbit is mentioned, but if you did then you know I’m not against it. I intend to play with it in the amateur bands.

Yes. Where GMRS differs is that FRS users may not transmit on the main 467 MHz channels (23-30) that are (mostly) reserved for repeater inputs.

But there is a possibility :

If you’re receiving it it’s interfering with your station. But that’s not stated in the requirement anyway: a) In addition to the prohibited uses outlined in § 95.333 of this chapter, GMRS stations must not communicate: (1) Messages in connection with any activity which is against Federal, State, or local law; (2) False or deceptive messages; (3) Coded messages or messages with hidden meanings (“10 codes” are permissible); (4) Music, whistling, sound effects or material to amuse or entertain;

Just as I asked….why don’t you report it?

It’s difficult to know what you’re complaining about, but if it bothers you, why don’t you report it?

No, he was testing both the shield and the center conductor at once by putting a jumper at one end and the ohmmeter at the other end.

Did you test the mount or just the coax? You may need to put an antenna analyzer on the antenna that gives you the high SWR and see where you are on the SWR curve. Without knowing where you are on the curve it’s more difficult to know how to tune an antenna and Marc’s right, the MXTA26 doesn’t need tuning. By shortening the whip, you might have just increased the SWR.

I guess you’d have to ask Blaise what he meant when used the term “ultrasonic”. To me it sounds (no pun intended) like he thought that he was saying that this method of sending text messages would not be audible to people listening to the affected frequency because they would be in the ultrasonic range:

The Midland MXT575 doesn’t allow you to choose repeater channels until you have activated them. That’s covered on page 10 in the manual.

Well, officially,GMRS is:

Here’s the nickel tour of GMRS repeaters: First: You transmit on one frequency, which is in the 467 MHz range and listen on another which is in the 462 MHz range. As long as you choose a repeater channel on your GMRS radio, that’s automatically done. If you’re transmitting on a 462 MHz channel you’re not on a repeater channel. Second: If the repeater has an input or uplink tone (called CTCSS by most companies or PL by Motorola), you must set a transmit tone that exactly matches or the repeater will just ignore you. There’s a digital alternative to that called DCS (or DPL by Motorola of course) that might be required instead. Third: the repeater probably has an output or downlink tone as well. That’s optional, but if you try to use it be sure to get it right. I usually tell people to leave the receive tone empty when getting started. That allows you to hear everything your radio receives. There are some GMRS nets in Phoenix that I listened to the last time I was there. That’s a good way to test your configuration because you have a high degree of confidence that there will be signals for you to listen to and it’s a non-intimidating way to test your ability to transmit. Check out https://www.azgmrs.org/

Ultrasonic frequencies are not transmitted by voice mode radios such as GMRS. The available bandwidth severely limits both the audio frequencies that can be carried as well as the data rate. Any Ribbit transmissions will be right in the most audible frequencies that humans hear. Ribbit transmits using the audio frequency range of 500 Hz to 2500 Hz.

My friend’s Baofeng UV5R transmits at just slightly more than 5 watts as measured by an MFJ UHF power meter.

I’ve never heard of coax being cooked at low wattage. I don’t think that’s what happened. But it certainly might have gotten damaged in a way that allows a short or open. Try another piece of coax.

@marcspaz Assuming the repeater had been established for some time, folks using a channel that’s known to be in use by a repeater is a bit like fly fishing directly beneath a dam. Sooner or later the dam will spill.

Alright, I’ll give it a rest.

Here’s the official regs: https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-E I will try to list the different types of stations but I apologize for missing any: Base Station, Control Station, Fixed Station, Mobile Station, Portable Station, Repeater Station. Unless regulated specifically, Portable Stations are a subset of Mobile Stations. Handhelds are simply a type of Portable Stations. There are a very few regulations that apply to handhelds to the exclusion of other station types. This forum has a long and possibly inconclusive discussion about Fixed Stations.

If you read the regulations you’ll find references to several different types of stations.

If you click on where it says “quote” at the bottom of the post you’re replying to, you won’t need to copy and paste and put quotation marks around it. It’ll automatically put it in a nice box.