I bought >>this<< transmitter, which sounds phenomenal but is a total POS. It overheated out of the box despite good SWR. I had to strap a heat sink to it and put a high powered fan over the output final. This has worked ok but the transmitter will no longer transmit on higher frequencies. Just ones below 92.0 (approximately) and below.
Based on the specs, I'm looking for something at www.elecsky.com that will sound just as good, but offer the swr protection and heat protection. I really don't want another muddy sounding transmitter like the one I had before this one, which was an hlly 5w. Nor do I want something that is going to overheat and burn up.
I've seen in the specs stereo separation, audio distortion, etc. Based on these, can anybody point me in the right direction to get a transmitter with the same great sound I have now?: Here are the specs of my existing transmitter. Thanks.
Power supply voltage: DC-12V Current work: ?4A Frequency range: 76 ~ 108Mhz or 76-90mhz or 87-108mhz Frequency Step value: 0.1MHz Frequency stabilization way: PLL Frequency stability: ± 10 ppm (-10 ° C +60 ° C ) Frequency Modulation: ? ± 75kHz (100%) Work methods: continuous work Clutter and Harmonic: less than-60dB SNR: ? 75dB Stereo separation:-50dB Audio frequency response: 50 to 18000hz Audio distortion: <0.3% Modulation: 15% Input Level:-15dBV RF output impedance: 50 Ohm
Things to look for are good stereo separation, low audio distortion figures and a good SNR rating.
If you want high quality audio then getting a transmitter with the option to disable pre-emphasis is a must so that you can do pre-emphasis prior to the transmitter in your audio processing software or hardware. Using a transmitters built in pre-emphasis is a huge nono if you want quality audio, stereo pilot protection, and brick wall audio filtering.
If you ever plan on using RDS or adding SCA then you will need to make sure the audio input allows for frequencies that high. Some of the more fancy transmitters have built in provisions for those accessories.
If you want the best possible audio and setup your station much like a professional one would then you want to get a mono only FM transmitter. It will simply have one audio input usually labeled "MPX". You then use an outboard audio processor which can either be a computer running something like breakaway, or a hardware processor. That will then generate your MPX for you which contains stereo audio, your RDS information, and properly filtered audio.
Of course that is not always the cheapest way and sometimes just using the earlier method I mentioned is more obtainable for hobby broadcasters. Most of the cheaper transmitters like the one you linked to tend to have built in brick wall audio filtering and pre-emphasis which can sound alright but not a good decision if you plan on using outboard audio processing. If you do go that route then make sure to disable pre-emphasis in your outboard processing as the transmitter forces you to use its.
The specs on that is 45db of stereo separation. That is not much better than a cheap ramsey kit would offer. It could sound alright if you don`t mind some left/right channel bleeding. As always make sure to run that chinese jobby into a good LPF before the antenna.
Thanks for the info. I may go with a transmitter where I can turn the pre-emphasis off. I'm surprised this isn't an option on most. I've noticed that transmitters with RDS or multiplex inputs have BNC connectors. How would I go about feeding these BNC inputs through my sound card?
You should be able to just prefabricate your own cable to go from the soundcard to the MPX input, or get a simple BNC>RCA jack adapter and run a cable between that and your computer which may then need an RCA to 3.5mm headphone plug. It would be much cheaper to just whip together your own cable and jack ends if you have the soldering iron. Any quality audio cable should work fine. If you use the MPX jack I would guess that pre-emphasis would be bypassed by default in the transmitter. You would know right away if it is being used because your audio would sound very bright and brittle if not outright distorted.
Thanks for that info. I will definitely make my own 3.5 mm to BNC connector. I hope you don't mind my asking one last question, but would you think that transmitter I linked above (which states 0 to 50 watts) would heat up if I lowered the power output? I had one cheap transmitter that would get really hot and I wonder if the more expensive ones have a better way of reducing the power without generating heat.
that is a CZH transmitter. i highly recommend a 9 pole adjustable LPF or a BPF on those. i have been told by a very reputable commercial broadcast engineer i know that while the on air sound is fairly good the harmonic output is very dirty. on the upside he says when you add a LPF or BPF they are pretty decent transmitters. just my 0.02 cents
JD
"The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane."
Flush Rush, Pull your head out of Fox Boobs, tune in more C-Span, Norman Goldman, and Thom Hartmann, you might just surprise yourself and learn something!!!
The one is a kit, the other is fully built. There is a similar one without SD card slot. Don't get that one, it uses a shitty chip (KT0803L). These use QN8066 which is good.
The 30W yellow board transmitter is also good if you want a bit more power, but it seems unavaible at this time. Maybe it's still on aliexpress. The 30W can be upgraded to 70W. I am currently speaking with a man from Croatia who is documenting the process. It involves replacing the mosfet with RD70HVF1.
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