Chinese 500mW should only use QN8007 chip

[EFR]

I have seen some of these cheap ones make quite nasty spectrum if antenna is badly matched.

[FMEnjoyer]

I bet so. I don't suggest anyone use one. According to the Spectraman guy on YT the QN8007 offer hope, not pro level clean but a hell of a lot better for an extremely low power 500mW stereo TX. Which is you set up in the right place, right frequency, with the right antenna will be very surprising.

[oazz]

I dont understand why you mess with these crapboxes?

If you will buy such transmitter you will not speak any more that it is a crappy box. I have a such.

https://www.ebay.com/itm/375815723475?_ ... R5aN7sr6ZA

oazz as you own one, can you tell if there is a filter network, coils..... under the heatsink where the RF P.A transistor would be in your photo below, as there is nothing visible in the photo below that looks like filters for harmonic and spurious.

The filter in the transmitter is. The sound is much better than in crappy boxes.

[FMEnjoyer]

Some of the chips do seem cleaner than others. I found this video the BH1415K which is not too far behind the QN8007 according to info online as per the table in post 4 of this topic. He does a spectrum test and says it seems low spur and harmonics but the audio on the BH1414K is not a good as the QN8007. The QN8007 and BH1414K seems least bad in terms of spurious and harmonics BH1415K a little less good but measured ok in this video. Probably best not to run either more than 0.5 to 1 Watt to be extra cautious.

[oazz]

In my transmitter of QN8007 15 w. All FM radio stations it is audible near the transmitter. Harmonicas I do not observe.

[oazz]

[/quote]
https://www.ebay.com/itm/375748809237?_ ... R4bcvrn-ZA

[FMEnjoyer]

BH1414K in a GD-2015S model, taken at face value does not look too bad if you did a hobby 1 Watt or less to be on safe side. I think some of the newer versions have improved a lot at least from what we can see. Certainly much improved over the 500mW 8027 chips.

[mikroman]

When I see that a Chinese is measuring and advertising something, the story immediately somehow loses credibility.

[FMEnjoyer]

Yeah you sum it up, take what info you can and make your choice based on needs and what you can find out, each to their own.

[radionortheast]

They might be better getting a cze, think there is one already that does 0.5w, think they use a bh chips, the one I had 1-7w, you got a few small carriers near to the aerial, didn’t have the noise of other chips that wipe out fm like the qn/kt chips, the amplifier also wouldn’t sprog, it did have a noisy fan, not so easy to ajust the power. The only problem was the stereo, stuff going on which problaly degraded the range some what. Qn they offer better stereo, with half watt you would be ok with 8066, stereo is good on it, there are no half watt transmitters that I know that use it. In the 5-7w kits, they use the 1971 device, seems to me the amplfier is faulty in these things can sprog, suppose the 1971 could be removed, you’d just pass the signal through from the half watt transistor, it would have to checked out, then you’d have a neat transmitter.
https://www.aliexpress.com/item/1005001 ... ry_from%3A

[FMEnjoyer]

I think it is important to be really clear about the QN chips, they should not just be stated as QN as there are various model numbers and the QN8027 is total junk.

QN8027 is diabolical - unusable really, dangerous to use and in the 500mW small FM TX's powered by USB C

QN8007 is really quite good, argued as being the best by Spectraman on Youtube, videos also on this and other threads.

QN8066 seems quite good. The trouble is you never know if a Chinese manufacturer makes 1-2 units makes a video and then puts a terrible chip in. It is pure chance and luck what you may get sent.

The 500mW rigs virtue is they are very light portable and can be run off a 5V emergency mobile phone power pack. Few other rigs have this ability that you could literally tape the entire system to the top of a long fiber glass flag pole in the middle of nowhere. You cannot easily do that with higher power Chinese rigs. The PCB only rigs are hassle, you need to solder, they need more power and 12V.

But as present the 500mW black aluminium ones use the terrible QN8027 you should not use them unless you want to interfere.

This video has the table showing what ones are decent and those that are trash. QN8027 is trash. QN8007 third in the table is good.

I have concluded though that messing around at home is a bad idea, no one will hear you are you are a sitting target. A shame but that is the reality. FM for pirates of all kinds is in its death throe. There is just no point risking it as others have said. It is fun to think about but the reality is pointless and dangerous.

[radionortheast]

It got confusing you have a working pcs 2015 under your bed some were but don’t want to use it, but want to use this half a watt thing on a pole that would likely draw alot much attention to what you were doing. Would likely give other people a worry if you were putting these up in the street some were. When you have that pcs 2015 you could get going with the aerial in your back garden which wouldn’t bother anyone lower the power to half a watt.
I did think we were on the same wavelenght with wanting people to get a clean transmitter, you also say your not going to use any of this stuff, don’t know why it was so important, it did seem to me that you were towing other peoples line here. I think it was rude of you to post spectraman’s videos over and over, discount others, discount someone who was trying to help you out. None of those transmitters work off 5v It also has no audio source would add weight, another thing to power. When the batteries run out what you going to do, the fiberglass pole would stand out, your going to have disguise the aerial. I don’t think it would work as well as you think it would, more like an fm bug/science project in a tree.
I think for alittle radio station this will not work, you did say fm would reach noone, I think the wrong way to think about this, something for you to put music over when you would want too.

[FMEnjoyer]

Hi northeast sorry if you felt it was rude, why I don't know.... but sorry anyway.
Spectraman seems pretty reliable to me, he calls the really bad stuff out..

Fact: PCS 2015 is not stereo, needs 12V. If I did want to put something I would never do mono.

At least I brought a debate up where 500mW very clean chip based QN8007 most likely, PLL stereo that was you know.. actually available in reality to buy from uk/euro and not in someone head or PC PCB drafts.

Seems the Qn8007 GD2015 that EFR tested was rubbish after all still waiting for what oazz thinks of this by the way.

Some of the same people shunning the Chinese stuff promoted crap from Netherlands also that is more than likely worse as it had zero filtering I could see and was VFO. No one is perfect. Historically people must have used total junk up blocks to think this was all super clean PLL all the time is total rubbish. I have heard insanely sproggin rigs on blocks.

I am not a perfect human being here. There are many ways to do a bit of radio than mono 200W off a block playing the same old in mono. And I suggest that if this has any kind of life beyond a few years people get inventive.

Do whatever you want, all risks on on every individuals head. This is why I don't bother... once every now and then I think of radio and then just do something else cause it is too much bother. but.. a super easy clean 500mW Stereo from USB C 5V could be very interesting.

Different ideas that spring to mind have different solution needs. 5v stereo PLL 500mW light with SMA and a telescopic whip + clip on ground planes has soemthign really quite interesting for me. I have a 500mW, a friend tested it and it is going 1.5miles, with more imrpovemenst I think it will do 2.5, all self contained, no coax, no swr meter, no big psu, no trouble, ALL self supported and powered and weighing about same as a smart phone 300-400g, but now I know it uses a terrible Q8027 chip, I will never switch it on ever again.

[yellowbeard]

Nah mate - you are rude, it's not a feeling I have or anything. You lost this arguement already, but you start it off again in the face of evidence with the same old lines. That's rude right there. Also be succinct if you are going to flame me, I might miss if the post is TLDR.

[EFR]

When I have some time in my hands (and get some genuine MRF237 transistors).

I will build one Stentor transmitter, and hook it up to the testgear.

I have now 20 "MRF237" labeled transistors that are 2N2222 or 2N2219A in diffrent can.

[FMEnjoyer]

Nah mate - you are rude, it's not a feeling I have or anything. You lost this arguement already, but you start it off again in the face of evidence with the same old lines. That's rude right there. Also be succinct if you are going to flame me, I might miss if the post is TLDR.

You are probably just a bit upset that I called you out for suggesting VFO garbage on another thread, you cannot have it both ways.

I lost the argument and admit it. It seems at least if we take EFR's analysis as the only valid analysis, that's all.
I will waste no more of your or my time on here. Enjoy the radio whatever you do.

And for all of us sakes it is really probably best we understand the entirety of this, it is a massive waste of time playing a bit of music with the risk of a criminal record. It's deeply idiotic really, through all of this I have learnt something really good, spend time on anything except pirate radio, even thinking about it.

So on that positive note have a good life everyone. I will still enjoy reading the forum and maybe giving a little RX report here and there.

[Novaro]

Personally i like the versatility of these small boxes. But the broadcasting dreams stop here. You can use them for your hobby plug a phone and do walks with the car that's enough and that's why i bought myself 2-3 of these cute small boxes! One of them the old classic 5w black (bh1415f) with the red leds is really good!

There are people here that are Legends in the broadcasting area for many years. Reading them i am not satisfied only using a box, i like to learn how a transmitter works, make mods from one design to another to eliminate problems, try some components and the effects in the sound and rf quality, solve problems by searching the net, try from simpler to more advanced designs , make my own working boards that they broadcast on fm! It is a trip for me it is not only to plug something on power and work but it has to relate with my efforts into that because i am broadcasting with the machine and not the machine alone.

[FMEnjoyer]

The trouble comes from amplification. QN8007 spec sheet, if it is true even? Verified ? How ? Benefit of doubt was say all down 50DB spurious and harmoncs, great... its good enough.. but then when amplifying I guess this is not linear ? So then sprogs start up, other circuit issues, wrong loading, I bet it then makes efficiencies for spurious and harmonics. And then totally random application of filtering... if barely any at all.

I saw 6 coils in 500mW I just wished or hope somehow a QN8007 would work in the 500mW ones with good filtering, then it would be ok for 500mW.

500mW PLL stable stereo is a very attractive power output as it allows quite low need for VSWR, should not burn, out 5V is fine, SMA out, add telescopic whip with 3 very roughly 45 degree solid core hook up wire ground planes with croc clips, that's close enough 50 ohm tuned GPA.. this gives with imagination some very interesting possibilities. Hike up a tree on fishing line and a weight thrown But even 500mW using 8027 is scary with its spurious.2 miles all round easy peasy disposable.

Such potential yet useless, no one wants to interfere. Anyway unless I find something stereo pll, 5V 500mW, minijack sma that is clean i will put all this to bed.