Post by HighMountainRadio on Jan 18, 2018 15:27:25 GMT -6
Greeting To All !
I am in the process of gathering as much information as possible for each of the Chinese FM Broadcast Transmitters as possible to help any and all of you out there who may be looking for a decent, affordable FM transmitter. The model I am currently using, is known as the 'ST-15B' marketed under a few names, they 'appear' to all be the same thing pretty much from what I have been able to glean. There are THREE version of it currently marketed on EBay.
Version V1: 15 Watts (Non-Variable Output) Version V2: 1.5 / 15 Watts Low or High Power (User selectable from front panel) Version V3: 15 Watts (Non-Variable Output)
All three versions by default are set for 50us Pre-Emphasis, however, you may specify at the time of ordering, from at least a few EBay resellers, either 50us or 75us pre-emphasis ! Be SURE to inquire about this when placing your order ! Some re-sellers were willing and able to give me more information than others. Please message me and I can tell you which re-sellers are able and willing to accomodate you regarding this.
I have two of these transmitters, both set up for 75 us pre-emphasis and they both sound good on the air, however, even into a 50 Ohm Dummy Load, using a Bird Model 43 wattmeter neither one will give you more than 10 watts output. I have tweaked both units for maximum output and this seems to be the best you can expect to achieve. I personally don't see this as a major issue since I use my transmitter as an 'exciter' anyway, to drive a 80 watt homebrew HPA which it works flawlessly with ! Of the two units I have tested using a spectrum analyzer, both are very close to their rated specifications and quite 'clean' offering 24/7 use, but I recommend using an external cooling fan, muffin type or muffin (directed port) high CFM, easily obtained cheaply via surplus outlets. They both only get barely warm to the touch when only using the small built in sleeve bearing fan. For this reason, I recommend an outboard fan. Sleeve bearing fans don't usually last a long time before slowing down. I plan to replace the internal fan with the same size 'ball bearing' fan.
I purchased these units for $56.00 each on EBay with FREE shipping from China (2 week delivery), very reliable delivery from China ALWAYS from my experiences. I personally have and use two of the V2 Version. The V2 Version, and I suspect, all three versions have a built-in VSWR 'foldback' circuit which protects the final output MOSFET from high VSWR and will automatically reduce output power if your VSWR is above a safe threshold.
All three versions have LEFT and RIGHT 'RCA' type female connectors on the rear panel for audio input as well as a 3.5mm front panel mounted jack, also for audio input. They all have a front panel mounted Volume Control knob and is fully adjustable for both front as well as rear input jacks. Additionally all three versions have a front panel mounted 3.5mm Microphone input as well as a front panel Volume Control knob for the microphone input level.
From carefully studying all 'similar looking' models, some labeled simply 'ST-15B', some branded with 'NIOrfNIO', 'FMUser', 'CZH-15A', 'HLLY' 1~20 Watt, and 'Signstek', however, without a detailed internal inspection of the latter units I cannot say with any certainty that all variations (Name & Nameless Varieties) are indeed identical (for the most part) internally but I suspect that this is indeed the situation.
Overall, and considering the inexpensive cash outlay, to purchase one, I am very satisfied with both of my units and their respective performance ! If anyone has any additional questions, I would be happy to try to answer them as accurately as possible ! I hope this helps some of you make an 'informed' decision when making your purchase.
Here are images of what the 'ST-15B', 'NIOrfNIO' and 'FMUser' units look like. ***NOTE --- While all three units appear, at least from external panel layout, to be likely internally close to identical, their respective range of frequency transmit capability and output power may or do differ depending on what ones are available from each 'manufacturer'.
For instance, the 'ST-15B' V1 Version transmits from 87~108 MHz, the V2 Version, from 87-108 MHz and the V3 Version from 76-108 MHz, however, for our intent and purpose all three varieties encompass the entire USA FM Broadcast band.
Enjoy ! I hope this information proves to be useful ! Most of all, have fun, learn and educate yourself !
73... Spooky...
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"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
Post by amateurstation on Apr 23, 2019 6:28:42 GMT -6
Hi.. I have the Nio RF Nio T-15a version package..if you like I can send you photos of the cct. boards etc. One note- it worked ok for a while, then the PLL went nuts and it’s transmit range is now only from abt 60mhz up to 97 MHz. I do not believe I accedetially put it into some kind of “hidden” band adjustment by Radomly pushing an unknown sequence on the front controls- but doubtful. Other question is if the computer program available for this unit offers any band / frequency range changes.. I will be opening it up to look for any obvious cct board problems, but suspect a pll defect.
Post by 15wblumpkinpirate on Dec 4, 2019 7:12:27 GMT -6
I, too have the silver machine pictured above - at the moment I'm not using it until I learn more about it. Does it ever splatter over other frequencies or do they stay locked in and clean? Also I got the stock magnetic telescopic antenna (not weather-proof) and that antenna feels kinda shaky (like loose on the base)so I ordered a ground plane (GP) antenna, but it needs a TNC to BNC adapter which is on its way. The GP antenna came with a basic measurement chart of how much to extend the telescopic part of the GP (In Chinese)to certain frequencies. Can those measurements be close enough or do I need certain equipment to get it right? Thanks for your patience with these rookie questions.
Did you figure out how you goth that Frequency range on your transmitter . I wish mine had that range . I wish to transmit @87.7 but mine stops @ 88.00 .
