Is that a decent one for price or are there other suggestions? Preferably pre-built though I probably end up building one in a few months anyway.
Also I saw in the starting out tutorial the OP said a basic setup was mic-transmitter-antenna but he himself was using a 1 watt transmitter with 30 watt amp. Is this just how transmitters work, low wattage with an amp or is there a reason that would be a preferable setup?
Plus whats the difference in the pole #s for lpfs?
Also does anyone have a good starting out point for the basics behind antennas? I know theres some different types but have already confused myself reading around this site. I keep hearing about tuned and seeing numbers plus I never realized there where as many types of coax as there are. (Though I should have guest being a computer guy and dealing with miles of ethernet all day)
It's a hell of a lot to learn isn't it? The funny part about pirate radio is that if you do this alone you are playing a lot of roles that the licensed broadcasters cover with multiple people. In other words you are the engineer, the DJ, the learner, and eventually become the expert.
I know it seems like a lot to gather right now, but you should understand THAT IT IS! No one can setup their own radio station by scratch by themselves without a great deal of learning. It's that learning curve that will set you well above the "professionals" that work at licensed stations, and if the day comes that you do get a job in radio broadcast you will be so far ahead of the ones who studied niche jobs in the industry that you will put them to shame.
That said and moving on to your questions..
Ripple and harmonics usually refer to the noise a transmitter puts out on frequencies that you don't intend to put out. Cheaply built transmitters (especially those built in countries which don't have the tight specifications of ours in the US) are prone to causing out of band interference. This interference is caused by not using properly built in filtering of the signal before it goes into the antenna. What happens is that the imperfect transmission not only broadcasts on the channel you want, but it will broadcast on multiples of your frequency with lower power. It's much like a musical instrument when you pluck a low E string on a guitar and it makes the higher octave E string vibrate. They are similar in octave, but dissimilar in frequency. So if you broadcast on 90.1 MHz for example using an unfiltered cheap transmitter you will also put out a weaker signal on 180.2 and even a weaker signal on 270.3 MHz. You should see why this makes it VERY important to filter out anything released by a cheap transmitter above your intended broadcast frequency!
Those upper frequencies may be much less in power but they could drop on important two way communications used by local police, airband, and other mobile communications.
Then there are what is called spurious harmonics. Those aren't always associated with multiples of your signal. Sometimes cheap transmitters use those all in one digital chips to produce your initial low powered FM signal. These chips use digital high speed switching to generate your stereo signal and can cause what is called "spurs". Those are interference near your actual broadcast frequency which causes your signal to interfere with frequencies right next to your own like other radio stations and once again possibly the aircraft band right above 108MHz.
This is why it's an ABSOLUTE must to use a filter. Those chinese transmitters have no care in the world at producing harmonics or spurs. Anything over 1 watt of power NEEDS a LPF and possibly even a band pass filter.
Stability of Frequency: This is easier to explain. Think of your transmitter as a guitar string that is plucked. The stability is how much that guitars note wobbles off of its note. If your transmitter doesn't have the stability it can wobble off of its solid note, or worse it can drift off causing your guitars note to sound flat or sharp. Sorry for using guitars as an example lol but I just got done playing mine
What stability comes down to is keeping your frequency ON ITS frequency. Some cheap transmitters, especially those built with cheap VFOs or instable PLL circuits will drift slightly off your frequency that should be solid on the exact spot on the dial. This tiny, sometimes unnoticeable change can cause your listeners to lose their stereo pilot causing your signal to default into mono, or can cause interference to stations right next to yours on the dial a channel apart. It can also cause digital receivers people own to not track your transmission and may cut off your broadcast or cause distortion in their received audio.
Freq. Response: This is almost always related to audio input and how HIFI your station will sound. The larger the response from bottom to top the more it sounds realistic and less telephone like to put it simply. The absolute limit of the aural range of FM broadcast is 20hz to 15kHz. As long as your transmitter covers this range with little distortion, the more it will sound like a professional broadcast. This is very similar to buying a good set of headphones. You want the broadest range of audio reproduction to cover the human ear and you want it mostly flat across its range. On the other hand you DO NOT want an FM transmitter to cover above 15kHz response for audio, unless you are using that ultrasonic range to send out digital information for RDS (so that peoples radio can decode the special information to list song titles and such that you broadcast using specialized digital stuff, outside the scope of this topic).
Your LPF (Low Pass Filter) question has it's own thread. Please don't ask in multiple places. I already answered you in your own thread as to a suggestion.
The more poles a LPF has the more it filters. 5 to 7 poles is recommended for FM broadcast, though even 3 poles is good enough for some low powered applications. Being as you are using the infamous chinese jobby I recommend at least a 5 pole+.
As far as antennas... that's a topic unto itself. Most pirates recommend either the 5/8 wave ground plane or the homemade j-pole which can be tricky. A simple dipole cut and tuned to frequency will outperform most 1/4 wave GP antennas but will have a higher angle of radiation if I remember correctly. 5/8 wave antennas have some gain over a dipole (1/2 wave) because they focus more power towards the horizon rather than up into the sky where no one is listening. A j-pole is basically identical to a dipole antenna, only difference is a j-pole is an end fed antenna, and the dipole must be fed at the center which makes the dipole more complex to erect into the air since its cable is connected at its center instead of base if used vertically. Supposedly the j-pole has some gain over a dipole but only because the imperfections actually cause horizon gain.
So in order I would say from least quality to best it would be 1/4 wave whip, 1/4 wave GP, 1/2 wave dipole, 3/4 wave j-pole, 5/8 wave GP, and finally the best being directional yagi if you want to project your signal into one spot (you live on the skirts of town). Circular polarized antennas exist also but divide your power up so that 50% is being projected horizontal and 50% vertical which reduces efficiency but can work as a benefit to listeners if you use multiple bays like commercial stations do. Us pirates can only dream of that sort of setup, so thus vertical is the only practical way for us as most car radios have vertical antennas.
Holy shit I could have wrote a book. Good thing I am sipping some brews. Hope this helps you and many others.
Oops I was confusing you with another person who just joined. Either way the information is still 100% relative lol. Glad to see some new people get on here and ask questions. Welcome to the forum!
Thank you for all that information it was very helpful. I would gladly read about the lpf if you could direct me to the thread. Im still wondering what the poles actually are and mean. Also what do the different fractions mean in the antennas? also i was reading about people modding the cheaper czh transmitters. would i be better off doing that or just straight spending the extra money on a nicer one?
The thing is if you can gain a bit of soldering skills and a bit of ingenuity it's actually rather easy to design a LPF, but for now it is indeed best to just buy one until you learn the basic concepts.
Poles of filtering depend a lot on how the filter stages itself is implemented. There are various types of high frequency cut off filters and they can be read about on WIKI by even looking at how audio filtering works. It doesn't matter if it's radio or audio, it's all the same theoretically.
I will leave this explanation as simple as I can since going into a description of poles and various types of filter designs deserves not only a thread on the internet, but also a whole encyclopidea around the topic that you can pretend and rightfully so that the more poles the more the sharper cutoff the filter has.
Think of it as a pillow to a loud persons mouth but the stuff you want to hear is spoken in a deep voice and the annoying shit is spoken at an annoying high pitched voice all coming from the same mouth. The more poles = the more density of the pillow stuffing in front of their annoying loud bitchy mouth. The filter stage itself is the pillow. The stages are more pillows, or more dense pillows to block out the annoying person.
That person that is annoying is up a few vocal octaves than you. So if you smother them enough you won't have to worry about annoying your neighbors with their annoying voice.
solder? who said solder? i have a toolbox just for irons, solder, desolder and the like. Ive soldered everything from paper clips on missile defense systems for the US Navy (thats right america paper clips are what keep you free) to desoldering and resoldering an original xbox board because i got bored. and you anology ,while somewhat morbid, makes sense
One thing I forgot to mention is that the more poles of filtering the more diminishing results. This is why the common filters for RF are 3-7 poles because beyond that it becomes a matter of money over matter. What I am conveying is that there does seem to be a standard for radio broadcast that dictates that 5 or 7 poles are plenty assuming the antenna and transmitter itself are cooperating without high SWR (Standing Wave Ratio) and other issues. The more filters you add the more they become less productive. It's funny how many things in radio work this way. Even RF power does. The more RF power the more it becomes less important. Those first few watts make the whole show. Just something to keep in mind. It's too bad commercial broadcasters didn't understand this. They think the higher the numbers the more linear the results. It never works that way. /rant
solder? who said solder? i have a toolbox just for irons, solder, desolder and the like. Ive soldered everything from paper clips on missile defense systems for the US Navy (thats right america paper clips are what keep you free) to desoldering and resoldering an original xbox board because i got bored. and you anology ,while somewhat morbid, makes sense
Hey if you can build a LPF then great! There are a ton of plans online showing how to design a LPF for <108MHz. In fact that would be my first recommendation to build your own instead of buying. The plans are pretty basic. Just do a google for LPFM LPF circuit for example. Even if you don't own a scope to check how clean it's working you can get a great idea by simply tuning the filter and then your TX and looking at its output, then jumping a few FM channels above (all via dummy load) and seeing if it's cutting off RF power above your frequency.
OK Ill definitly look into that. I was thinking about building my own transmitter but decided to just buy one so I can learn all the tweaking parts of everything then possibly build one. But building just an lpf( i have used them before but we just replaced the whole thing if it broke and never learned about them) will let me get my messing with electronics jollies off for a while. Do you have any recommendations for a decent transmitter or just go with a czh chaeper one and modify it to be decent?
OK Ill definitly look into that. I was thinking about building my own transmitter but decided to just buy one so I can learn all the tweaking parts of everything then possibly build one. But building just an lpf( i have used them before but we just replaced the whole thing if it broke and never learned about them) will let me get my messing with electronics jollies off for a while. Do you have any recommendations for a decent transmitter or just go with a czh chaeper one and modify it to be decent?
In all honesty I have never owned one of the CZH transmitter. I just know the specifications and user reviews of people I trust. I say go for using the CZH rig. It may have it's share of worts but there is no reason that they can't be modified over time.
I will come out and say I used a Ramsey FM10c for a long time as an exciter and yes it was a toy... a literal TOY for a radio transmitter. Kids use that stuff for broadcasting around their schools or churches. However I get really touchy when people flame these little transmitters not understanding how they operate or how they can be modified into actual professional class rigs.
Even the BA1404 chip used in the really awful Ramsey FM10 that many of us have started playing with as teenagers can be modified to run a clean signal that still rivals some of the older 1970s tube type FM MPX units if designed properly.
I know I am ranting lol but I need to say this.
People make a lot of fun of those chinese, the Ramsey FM kits, the Veronica setups, and so on. They have no idea that the electronics don't matter one difference as long as the proper sweeps and levels show up on the oscilloscope. They think because it's junk that it has to be junk.
Those chinese CZH transmitters CAN BE MADE to sound and work clean/good respectively. It takes modifications and there are threads on these forums for those discussions.
Just don't get confused thinking just because it's cheap that it can't be made to work well. It's the people who work well that buy cheap stuff that don't get it. Money is not the answer to good transmissions, it's the owners understanding of their equipment. I know ham radio operators that spend a ton on equipment and can't rival a CB radio, and I know others who build their own QRP ham radio equipment using radio shack shit that contact all 50 states.
to add my 2-cents WRT to antennas - my NRGkits 1-watter (RIP Steve Moss)VFO (nice almost no drift, clean sound, good separation) increased her range by about 1/3 when I switched from my original dipole to my new j-pole (both homemade from plumber's copper tubing).
j-poles are pretty easy to build - just get a diagram from the net and cut the pipe to the freq you intend to use. you need a flame source (like the acetaline canisters) and some solder to weld the copper pipes together.
to add my 2-cents WRT to antennas - my NRGkits 1-watter (RIP Steve Moss)VFO (nice almost no drift, clean sound, good separation) increased her range by about 1/3 when I switched from my original dipole to my new j-pole (both homemade from plumber's copper tubing).
j-poles are pretty easy to build - just get a diagram from the net and cut the pipe to the freq you intend to use. you need a flame source (like the acetaline canisters) and some solder to weld the copper pipes together.
about 2-hours of work overall.
You can always use conduit pipe. It is far cheaper and works equally well. Only issue is you need to build it slightly different from not being able to solder to it, but with clamps and a bit of ingenuity it can be designed by most people. Another variation on this is to use PVC and twin lead wire and make a slim jim out of the twin lead and slide it up the PVC, cap the ends off and will work well.
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