HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: Matt285 on January 13, 2020, 2350 UTC
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What would be a basic pirate set up as far as transmitter type (Wattage output) input cables from a laptop to produce the music and soundboard to be able to transmit your own voice? Thanks. Chris, feel free to move if there is a more appropriate area for this.
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I completely understand if these are trade secrets and are not to be discussed..... I'm asking for a friend anyways.
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Also depends on the "strength" that you want to become your station.
And .. can you assemble / solder something yourself?
On my Google-drive - some Schematic Diagrams etc!
https://drive.google.com/drive/folders/1XSkQ0RjUuR3Sp53ULmuOH5UePFvAS53y?usp=sharing (https://drive.google.com/drive/folders/1XSkQ0RjUuR3Sp53ULmuOH5UePFvAS53y?usp=sharing)
André
CoolAM Radio - Shortwave
the Netherlands
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There are many variables..
What mode? AM or SSB? AM requires more power for good reception but generally better audio quality.
What distance is your audience from you? The farther away your audience, generally the higher the power.
What frequency? Lower frequencies generally require more power to overcome higher local noise levels at low frequency.
This time of year NVIS can be had during the day on 4-6 MHz. Assuming a location on the east coast and also targeting said such, 50-100W (200-400W PEP) AM should be sufficient. SSB will require about 1/4 to 1/2 above values.
Everyone's definition of bare minimum is different. I would recommend some sort of audio processor before the transmitter to both protect it, and prepare the audio for transmission. If everything you will do is canned, this can be done in the computer after a final mix is made.
It is important also that the transmitter is well matched to the antenna.
No real 'trade secrets' in any of this stuff. I have worked on and off in commercial radio engineering for almost two decades, and most of my airchain is modeled after what the commercial guys do. This is after all a hobby.
+-RH
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Yes..... 'This guy' has built a couple of transceivers. and has access to an antenna analyzer for tuning such antennas. Interesting to bring up AM or SSB. I see a lot of people using SSB and i figure theres a reason for it. Although I see AM activity as well. Whats the pros and cons of the two modes and reason for one vs the other? Thanks
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One advantage of AM over SSB of course is that every SW receiver does AM, but not all can do SSB. Of those that do SSB the cheaper ones often are not EXACTLY on frequency which is good enough for speech but not music. These days though good SSB gear has come down in price a bit & with an SDR its easy to get right on frequency.
One disadvantage of AM is that it's not as efficient and gear tends to run a bit hotter since the carrier is being transmitted even during silence.
As for sound quality tbh I kinda like the sound of SSB better. It's not gonna have the low end like AM but its not as prone to sounding "muddy" like weak AM signals can. Just my .02 -Justin
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'Soundboard'
That's an interesting term!
I sell transmitters.
You'll need a dipole antenna, easily made and a 1/4" jack to connect to your sound source.
Power supply is 24V but 12V if you're happy with lower power.
PM me if you want any more info.
Regards.
Stretchy.
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My two cents.. what do you want? Well FM, in US FCC watches in cities, shortwave on clear channels, bcareful, use diffrent modes, bands.. times, not to excess, -- way to go.
Tx.. best would be probably more expensive, not impossible, just lets face it most peope use junk or their ham gear.
AM.. its ok, not good unless you have 100 watt old buzzard tx. Better in the frequency stability not an issue.
SSB wide band, if possible best efficiency, problem many people don't have what they need, first class digital rx with a PC, these are available for 70-what ever dollars.. need a PC. These are great Rx for SSB, stable.
Tx SSB best, tricky old ham radios are worthless because of phase noise and music will sound like szit.
Needed a phase stable DDS radio. These are out there kits and ham rigs. With ham stuff YOU will need modify to get on a band. Never do it in ham bands, they are vicious in reporting, no sense of humor at all.
Just my two nickles and a dime.
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'Soundboard'
That's an interesting term!
I sell transmitters.
You'll need a dipole antenna, easily made and a 1/4" jack to connect to your sound source.
Power supply is 24V but 12V if you're happy with lower power.
PM me if you want any more info.
Regards.
Stretchy.
LOL! Yep. Attach the coax and the power source wrap the audio feedline around a snap on ferrite to stop RF from getting in your audio source and fire that baby up! You can sit under the antenna and not have to sweat it.
A tip for the monitoring receiver, clip the plug off a non-working pair of headphones and stick it in the antenna jack. Then tune the radio to the second harmonic of your tx. It will give you a better idea of how you're sounding. Adjust the audio if you need to. Then take a nap. You've probably heard the show five or six times before you air it. Good luck!
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Go Bluetooth, no wires. But it depends on many things. Where do you want to operate from. A home or mobile. When do you want to operate,24/7, evenings/weekends, holidays? Who is your target? FM is the mode/band of choice for most pirates.
~
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Great advice. Yes as a ham myself that would be frowned upon for sure. Other than the transmitter and antenna. What equipment is used as far as an interface to get the sound audio into the receiver and also what would be used for the voice. This may sound a bit silly, but I would imagine theres more to it than keying down a microphone while playing music through a speaker. I used the term soundboard because it was the first thing to come to mind. Thanks for all the feedback.
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Great advice. Yes as a ham myself that would be frowned upon for sure. Other than the transmitter and antenna. What equipment is used as far as an interface to get the sound audio into the receiver and also what would be used for the voice. This may sound a bit silly, but I would imagine theres more to it than keying down a microphone while playing music through a speaker. I used the term soundboard because it was the first thing to come to mind. Thanks for all the feedback.
A cheap mixer like a behringer and a mic pre-amp (some come with compressor, limiter and de-esser built in). These can be found at a good price from sweetwater. You also need XLR cables and maybe an XLR to 3.5mm so you can plug in a comp to the mixer for the audio. The third and final thing is the audio processor. That's pretty much all you need. The most expensive part will be the audio processor. The cheapest way if you have some technical skills is the ADAU1701. On aliexpress, you can find modules with this DSP installed. Make sure you get the programming board also. You don't need to know how to program. You can use SigmaDSP which is an audio processing program that uses visual drag and drop style processing blocks. Takes a bit of work, but it's not very hard to learn. If you want to go the easier route, then you can probably find an old optimod AM processor on ebay (but it takes some time to find a reasonable deal) and it's going to cost a bit more money. The SW200 is pretty good too. To start out, you don't even really NEED the audio processor. Just build a low pass filter for 5 kHz or whatever you want. You'll need to get some XLR cables that you can rip apart and put some resistors to combine the stereo output into mono. On this same board, you can make a little low pass filter (just need some caps, resistors and a copper clad board). Look up stereo to mono audio schematic and low pass filter schematics (there's probably a calculator online somewhere). Now you just combine that on one small copper clad PCB. Then that leads directly into the transmitter. If you use an audio processor, then you won't need the filter part, but you may still need the stereo to mono conversion.
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Soundboard = mixer, ok I get it now...
Just record and process everything on a PC. Playback as an MP3 or whatever. Simple cheap. No need for any expensive hardware..
Str.
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I've still got several cassette decks I used. The things are robust when it comes to RF. I used an audio production program called "Cool Edit" some naughty pirate type cracked in the mid-90's. My soundcard had a built in limiter, but so did the later "Walkman" type players, pick your poison. Boomer built his Grenades, the transmitter I used, with a built in compressor/limiter. If you got the pre-emphisis and de-emphisis right you couldn't screw it up. ID's and general yapping were a little tougher. Get the best mic you can afford and play around with the EQ settings until you're sounding good through the studio monitor speaker then label it "voice" or "id's" and leave it alone. I have to cut the bass twice, I've got a deep voice and when it changed it went deeper. I had a HS teacher who was always giving me the "Bring it up, Barry White." Eh, what the Hell, the girls liked it.
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What Stretchyman said. And put all your work and money into making RF power and putting up the best antenna. K.I.S.S. 8)
~
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Soundboard = mixer, ok I get it now...
Just record and process everything on a PC. Playback as an MP3 or whatever. Simple cheap. No need for any expensive hardware..
Str.
Yeah, you could just use stereotool, but I think you still need at least a cheap mixer to connect your mic. The kind of mics you can connect directly to a PC sound card are not the best and then you can't fade it in or talk over.
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There are still a few Radio Shacks around that sell mic mixers for around 20-25 bucks. They'll do both mono and stereo.
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Spend some $ on a decent USB audio interface, one with an XLR mic input + get a decent mic. Will be all you need, that and a TRANSMITTER!
Str.