Vintronics - SJV

[Ignite]

Hi,

There is a new FM transmitter being sold on Ebay from Vintronics. https://www.ebay.co.uk/itm/393884386026. Has anyone taken a look at this or is the board familiar? It can also be found on their main site https://www.sjvbroadcastservices.com

Thanks

Ignite

[mikroman]

Chinese toys packed in a metal box with three times the price.

https://www.aliexpress.com/item/3288715 ... mainSearch

[fmuser877]

at least they show what's in side.

[Albert H]

That "7 Watt" FM transmitter board is actually surprisingly good:

A hotel not far from my summer house has one. On test it did around 5.9 Watts (after all it is a 2SC1971 final). The harmonics were well attenuated (around -65 dBc) and the in-band spurs were almost non-existent. The stereo coder isn't the best, but for casual use, it's not bad.

The hotel guy had asked me to put the thing into a box, and provide a PSU and an aerial. It went into a neat Eddystone diecast box, with the '1971 screwed to the case for heatsinking. I brought the control PCB out of the main box (the ribbon cable came out through a slot) and the control / display board was bolted to an external 2U 19" panel. I added a basic stereo limiter (in its own box), and balanced audio inputs. The diecast was screwed behind the 19" panel too,and the whole assembly went into the PA rack for the site.

The owner decided that it was too powerful, so I reduced the drive, reduced the supply voltage, and altered the output match. It's now a very clean 3 Watt rig, running down a 20m length of RG213 to a "Flowerpot" half-wave vertical, which is about 22m above ground. It goes for miles, even though it's so throttled back!

[sinus trouble]

I dunno who makes them Exciters but i have seen them floating around the Internet!

Infact! I saw one recently posted on this very Forum!

[yellowbeard]

That's a plastic box that yoke is in, you can see it around the power supply connector.

[sinus trouble]

That's a plastic box that yoke is in, you can see it around the power supply connector.

Haha! Great observation there YB! I never noticed that!

Hats off to the builder for a nice neat job, However a Rookie mistake!

[radionortheast]

The sound quality is really good on these transmitters, if you feed it from stereo tool I prefer it to my pcs transmitters it dose have some downsides thought. The carrier is pretty good I don’t think it is wide like you get on cze, noriofin transmitters. It does put out more white noise in the fm band than my pcs transmitters, seems to be the chip is producing it its passed on to the output. Another problem is that rf can overload display, on both the two I have, I had to cut the lead from the first output transistor, used resistors nearby to ajust the power, you couldn’t ajust the power through the display. On one you have to ajust the frequency on the display then turn it off afterwards then on again and it will change frequency, it can be a bit tempremental.
Another thing i’ve noticed when I put it on 100.7, there is another signal near 128Mhz, it has the transmitted audio on it, its not possible to tell how strong the signal is, i'm using a scanner to hear it, it is not something I have when I set my pcs transmitter 8015s to the same frequency and power level, its possible it could be got rid of with filtering.
I did manage briefly to have the rds coming through on it, I used 1nf capacitor connected at a place on the board were it started to come through, think some inbuilt filtering kicked in it filtered out the rds signal. Theres no swr protection you have touch the heatsink see how hot it is, I turn it off it gets too hot. Overall I think it is a very nice transmitter, definately good to have going on a low level round the house, better stereo sound quailty then any transmitter i’ve ever had, suppose the good thing is the pilot level is set by the chip theres no messing about with that either. The price, the size and the sound its definately worth having.

[Albert H]

It seems that there are several versions of this "7W" transmitter. All of them are based on the Chinese "stereo transmitter" PCBs, available from Ali Express (and lots of other places).

The first one I saw was entirely clean, with no harmonic or spurious products to be concerned about. It was based on a QN8007 IC, and worked pretty well. It was housed in a standard metal box with louvres at the back, and needed a 12 - 15V DC supply. It was fairly well built, and its performance was "acceptable".

The next ones used different "stereo transmitter" ICs and produced rather a lot of worrying spurs and harmonics. They were built into the same boxes as the first one, but their performance was appalling! The unitiated won't be able to tell these good and bad ones apart - they all look much the same.....

These "stereo transmitter" ICs were developed for "audio senders" - to send stereo audio from a portable CD player (or MP3 player) to a car radio over a range of a few metres, to be used inside a car. They are simply not good enough to be used for actual "free radiating" purposes.

If you put one of these things into an aerial, you have the very likely possibility of interfering with aircraft and other PMR services.

PLEASE DON'T DO IT!!!

[FMEnjoyer]

Interesting read Albert and northeast, it appears they can work nicely without harmonics and spurs with the QN8007. What a shame for some reason they changed chip. I don't see much in he way of filtering before the chip like EFR mentioned, just the 6 output coils and yet with QN8007 worked ok unlike the GD-2015 EFR had.

It seems that there are several versions of this "7W" transmitter. All of them are based on the Chinese "stereo transmitter" PCBs, available from Ali Express (and lots of other places).

The first one I saw was entirely clean, with no harmonic or spurious products to be concerned about. It was based on a QN8007 IC, and worked pretty well. It was housed in a standard metal box with louvres at the back, and needed a 12 - 15V DC supply. It was fairly well built, and its performance was "acceptable".

The next ones used different "stereo transmitter" ICs and produced rather a lot of worrying spurs and harmonics. They were built into the same boxes as the first one, but their performance was appalling! The unitiated won't be able to tell these good and bad ones apart - they all look much the same.....

These "stereo transmitter" ICs were developed for "audio senders" - to send stereo audio from a portable CD player (or MP3 player) to a car radio over a range of a few metres, to be used inside a car. They are simply not good enough to be used for actual "free radiating" purposes.

If you put one of these things into an aerial, you have the very likely possibility of interfering with aircraft and other PMR services.

PLEASE DON'T DO IT!!!

[FMEnjoyer]

Sorry after the chip.. ""work" if you filter output after chip before next stage, filter that next stage before PA and last lowpass filter." The boards above do not seem to show any such filtering but did seem to work.

What we know is that you have no idea what exactly is going to ship when ordering anything from China.

[FMEnjoyer]

They must have revised the entire circuit on the so called 7W boards as the QN8007 and QN8066 have entirely different pins on the IC, not even the same layout physically.

https://pu2clr.github.io/QN8066/

https://file2.dzsc.com/icpdf/18/07/11/6 ... 915924.pdf

[oazz]

Chinese toys packed in a metal box with three times the price.

https://www.aliexpress.com/item/3288715 ... mainSearch

This transmitter on QN8066. I have a such. Quality of a sound is not pleasant to me.

[radionortheast]

This transmitter on QN8066. I have a such. Quality of a sound is not pleasant to me.

The volume from the sd card is too high, you can use 2 resistors at the input from the 3.5mm jack between left and right to ground this reduces it alot. There is volume through the display if you use the jack, there are two jacks one is for a microphone, I think on mine the colour coding was the wrong way round, make sure its the right input, you do want to be careful with the volume as it can start the inbuilt clipper.

I had one of these I took out the ouput stage, walked around a mile away left my radio recording back on home, with a wire aerial above and below in a black box, I could hear it very weakly, obviously much better when I tried it the other way round. It fascinated me for quite a while with the sd card it starts transmitting straight away, never considered doing anything of this nature before, thought of course you can just use it with the 3.5mm jack, suppose thats how it would usually be used, will work much better from 12v. The 2nd one I had the output stage was in-tacked, a bypassed the 5v regulator, unjusting the biasing the output did come on abit, power them off a few aa or aaa batteries, it could work directly off of a little solar panel the angle had to be correct, so no transmission if the sun isn't shining. The results not great with the other thought, I didn’t bother anymore they are very interesting devices though, make sure you turn down the rf if your getting one.

[FMEnjoyer]

Chinese toys packed in a metal box with three times the price.

https://www.aliexpress.com/item/3288715 ... mainSearch

This transmitter on QN8066. I have a such. Quality of a sound is not pleasant to me.

As long as it is stereo I would not worry much. I am more worried about interference as should everyone.

I am more surprised the chip changed from QN8007 to QN8066 at some stage and required a total redesign of the circuit ? The spurs/harmonics got bad according to Albert when the chip changed, yet the spurious and spurs are supposed to be somewhat similar give or take 5db between the 2 chips. I imagine they both had the same 6 coils on the output for filtering.

You can see my frustration here, these "cheap" chips TX can work without too much sprogging. AlbertH confirmed it above.

The problem is it is suggested they change the circuits through necessity if they did use a QN8007 first. And then Rf being what it is, as I understand it is very sensitive to layout, any inductances and capacitances messing thing up and making them work out of spec and essentially malfunctioning with sprogs.

Northeast you could put audio from a sd card into audacity and drop the level 12db or something, put it back on card and then it will be ok level prob, if you really wanted.

[FMEnjoyer]

I appreciate I am beating a dead horse with the chips now. I have given up. I just had hope. And with no clean output 500mW or above stereo/PLL/ stable cheap rigs ready built it's over. Seems many have been through it before and it is confirmed that out of all of the many
Chinese concoctions 1 was ok according to Albert and that now no longer exists. And they never even knew it was decent when it was, that says it all, they changed the chip and it shows the Chinese have no clue what they are doing when it comes to chip rigs that work ok.

[Novaro]

I got one of these :

https://www.ebay.com/itm/404500271136?m ... media=COPY

It seems a different ic. I have a metallic box from a broken transmitter and want to house it there with all the connections etc. The ic has 24 pins but i give a chance this is a controller and usually the 8027 is hidden somewhere. This time maybe is under the lcd!!!

[FMEnjoyer]

It has no coils at all so it seems there is no attempt to filter the output that PCB trace 'coil' etch won't do much. This means you will be entirely reliant on chip spurious and harmonics. Unless it is BK1414K/QN8007 or a QN8066 which have the better specs when not amplified I would not get your hopes up. I wish it works well for you though Novaro.

At 190mW output it must be amplified and we know this is where it goes wrong usually.

[EFR]

Two 75nH SMD inductor on back (blue ones with 75N marking) and 4 SMD capacitors near them.

Looks like Chebyshev one.

[FMEnjoyer]

My bad. Test it and find out Novaro.