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-   -   VHF recording (https://www.thehulltruth.com/marine-electronics-forum/366098-vhf-recording.html)

Capt_Andrew 07-19-2011 08:03 PM

VHF recording
 
Has anyone ever used or set up a system for recording a VHF transmission? I would like to set something like that up on my primary radio. The radio is an IC-504 if that changes your answer.

Thank you in advance.

GTBecker 07-19-2011 09:40 PM

Like this? https://www.cobra.com/detail/mr-f80b...-say-again.cfm

or https://www.cobra.com/detail/mr-hh42...-say-again.cfm

If you want to continuously record VHF, connecting a recorder of almost any sort to the audio out of a radio should be trivial. What do you want to do?

jhebert 07-20-2011 06:17 AM


Has anyone ever used or set up a system for recording a VHF transmission?
I think you just want to record the audio output of a receiver that is tuned to a VHF Marine Band channel. As mentioned, this is trivial. The most difficult part will be to find a source of the audio output from the receiver which is not affected by the VOLUME control. If you record the speaker output, the level of the signal will vary with the VOLUME control setting. It would be better to locate a fixed-level output or to modify the receiver to have a fixed level audio output to feed the recorder. This would eliminated the influence of the VOLUME control.

It would be rather complicated to capture and store the actual VHF transmission itself.

Mersiles 07-20-2011 06:27 AM

See if you can find a freeware that will record in "Vox mode". Basically the software will listen for activity. Once a transmition starts it will begin to record and end a few seconds after the transmition ends. This way you wont record dead air.

GTBecker 07-20-2011 09:18 AM

One such piece of software that's capable of vox recording on a Win machine, although vastly over-capable for that task, is SpectrumLab.
http://groups.yahoo.com/group/SpectrumLabUsers/
I use it to produce the spherics stream in my sig below and I also stream Cape Coral - Fort Myers marine VHF from a fast scanner. I took the link out of my sig a while ago, but the stream still runs on Ustream (sadly with increasing inserted ads) at http://www.ustream.tv/channel/cape-coral-marine-radio .

fairbank56 07-20-2011 10:19 AM

Why not just use a portable digital voice recorder? I have on old Olympus DM-10 that works great for this. It has VOX and you'll be able to record your transmissions as well. Just turn it on and put it next to the radio. No connections necessary. Just a thought, might not work well in a noisy environment though.

Eric

Capt_Andrew 07-20-2011 05:13 PM


Originally Posted by GTBecker (Post 3899516)
One such piece of software that's capable of vox recording on a Win machine, although vastly over-capable for that task, is SpectrumLab.
http://groups.yahoo.com/group/SpectrumLabUsers/
I use it to produce the spherics stream in my sig below and I also stream Cape Coral - Fort Myers marine VHF from a fast scanner. I took the link out of my sig a while ago, but the stream still runs on Ustream (sadly with increasing inserted ads) at http://www.ustream.tv/channel/cape-coral-marine-radio .

Thanks for the responses thus far, but I am not technologically inclined. How do I go about hooking up the VHF to my computer so that I can even begin to look into vox recording software.

GTBecker 07-20-2011 06:27 PM

I use a Uniden BC72XLT scanner; it has a conventional 3.5mm (1/8") headphone jack, which I connect to the audio Line input of a PC (also a 3.5mm jack) with an appropriate cable. The scanner is, of course, powered and is connector to a rooftop marine antenna. The scanner is configured to scan all marine channels except 70, which is not a voice channel.

Alternatively, you can use a marine VHF radio that has an auxiliary speaker output connector (also usually a 3.5mm jack), but the radio's built-in speaker will also be active, perhaps a concern if you'll normally want silence.

To hear and record the Line input audio, you'll need to make some OS selections. If that seems a challenge to you, find someone who can do it, someone who drinks beer. Buy him a beer.

Just what do you want to do, I ask again?

Capt_Andrew 07-20-2011 09:49 PM

I will have to verify, but I am fairly certain that my radios do not have a 3.5mm jack.

Ideally, what I would like to do is set up my radio to record when I push to talk. Continuous recording seems unnecessary, but if there are programs that will record when I PTT, surely they can and have been written to record for 90 seconds beyond the end of my speaking.

GTBecker 07-21-2011 08:54 AM


Originally Posted by Capt_Andrew (Post 3901371)
... record when I PTT [and] for 90 seconds beyond the end of my speaking...

Ah. OK, that's a different problem. Sorry that I misinterpreted your need.

I suspect that a capable Ham would be able to find the modulation audio in your radio and extract it and the receiver audio, but that would not be trivial.

Another approach might be to use a separate receiver on the same channel, but then you might encounter RF overload and not get clean audio of the transmission.

I think you need to find a technically gifted friend.

Edit: In the US it is not legal, unless you are a licensed facility like a marina, to transmit on a VHF channel from land. Otherwise, your idea is fine if you intend to do it on your boat.

Capt_Andrew 07-21-2011 01:16 PM

I wanted to do it on the boat. It already has the radios and the desktop computer, so I thought it might be something easy to set up.

Rick1632 07-22-2011 08:02 AM

Looking at the rear of the radio, the left-most cable coming out of the center connector is for an external speaker. You could connect a recorder to that, however you would need an impedance matching attenuator and you'd only record the receive side of the conversation.

My suggestion is to find a used VHF radio or scanner with an external speaker connector and use that as a source. It will record both sides of the conversations.

Birdman 07-22-2011 09:52 AM

just and FYI, I'm pretty sure it is illegal to record, or re-broadcast any VHF transmission. ;)

GTBecker 07-22-2011 10:06 AM


Originally Posted by Birdman (Post 3904235)
just and FYI, I'm pretty sure it is illegal to record, or re-broadcast any VHF transmission. ;)

If that is so, Cobra is in trouble with Rewind-Say-Again. http://phx.corporate-ir.net/phoenix....564&highlight=

And rebroadcasting is exactly what SeaTow does with their automatic radio check services, isn't it? http://www.seatow.com/boating_safety/ARC.asp

tiaramisu 07-22-2011 12:16 PM

In the U.S. it is never illegal to record when there is no copyright or expectation of privacy. The VHF environment has neither.

Capt_Andrew 07-22-2011 03:17 PM


Originally Posted by Birdman (Post 3904235)
just and FYI, I'm pretty sure it is illegal to record, or re-broadcast any VHF transmission. ;)


I am going to need a cite for that. I have a hard time swallowing that when the USCG publishes has published radio recordings on the net. Before you say that the USCG can do what they want when they write the rules, the FCC is the agency which writes the rules relevant to radio communications.

fairbank56 07-22-2011 05:33 PM

As long as you keep the recordings to yourself, your fine. Here are the rules.


80.88 Secrecy of communication.

The station licensee, the master of the ship, the responsible radio
operators and any person who may have knowledge of the radio
communications transmitted or received by a fixed, land, or mobile
station subject to this part, or of any radiocommunication service of
such station, must observe the secrecy requirements of the
Communications Act and the Radio Regulations. See sections 501, 502,
and 705 of the Communications Act and Article 23 of the Radio
Regulations.

The communications act regulations state:

" No person not being authorized by the sender shall intercept any radio communication and divulge or publish the existence, contents, substance, purport, effect, or meaning of such intercepted communication to any person. No person not being entitled thereto shall receive or assist in receiving any interstate or foreign communication by radio and use such communication (or any information therein contained) for his own benefit or for the benefit of another not entitled thereto. No person having received any intercepted radio communication or having become acquainted with the contents, substance, purport, effect, or meaning of such communication (or any part thereof) knowing that such communication was intercepted, shall divulge or publish the existence, contents, substance, purport, effect, or meaning of such communication (or any part thereof) or use such communication (or any information therein contained) for his own benefit or for the benefit of another not entitled thereto. This section shall not apply to the receiving, divulging, publishing, or utilizing the contents of any radio communication which is transmitted by any station for the use of the general public, which relates to ships, aircraft, vehicles, or persons in distress, or which is transmitted by an amateur radio station operator or by a citizens band radio operator."

GTBecker 07-22-2011 07:23 PM

Ah, the beauty of the art of confusion and obfuscation. Lawyers rule (but should not, IMO).

Do not the sections you repeat say "The master of the ship [etc.] ... must observe the secrecy requirements..." which "... shall not apply to ... ships..."?

fairbank56 07-22-2011 08:19 PM

"which relates to ships, aircraft, vehicles, or persons in distress"

i.e. ships in distress.

Maybe I'm wrong, but that's the way I read it.

Eric

jhebert 07-22-2011 08:49 PM

In simpler language: you can't disclose any radio communication you happen to hear that was not intended for you, unless it was from a broadcast transmission, from an Amateur Radio station or a CB Radio station, or a ship, vehicle, plane, or person in distress.


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