Hell NO!! The 150w Chinese TX is now here.

[shuffy]

If someone else wants to do the test, I'd be interested.

I won't be bothering - you've seen and believe the stats in the datasheet - that's not good enough, and you can do it properly for the same price. More interesting to me would be the performance of the PA chain, although I suppose the comment about price stands here, also.

[helpMUCHappreciated]

I'm not here to have a heated argument or trade insults.

One member said these can be very dangerous.

I heard if an aircraft gets interference then they simply change channels.

Although I wouldn't personally broadcast at that power on the cheap just to eliminate as much risk as possible.

I am however intending to purchase a similar 30 watt transmitter.

I'm more than 20 miles from an airport, I'm assuming 30 watts is going to cause significantly less 'harm' than 150 watts of cheap chinese transmitter.

With beginners like me currently with tiny budgets, some of these cheap low power transmitters can be essential to keep us motivated.

My £50 transmitter of 7 watts output has been enough to completely restart my long latent ideas and spend lots of time planning for the future.

Without the feed back it just wouldn't have happened.

Have a great day.

[Analyser]

I heard if an aircraft gets interference then they simply change channels.

As far as I know this is not true. There is no set procedure for changing channels if you get interference on an air traffic frequency.

Even though you're 20 miles from an airport you have to consider the aircraft flying above you in the sky. As they pass overhead then their distance will be a lot less than 20 miles, perhaps 1-2 miles.

You have to understand that interfering with aviation is one of the most serious things you can do with a pirate radio transmitter, and if you get caught doing so you're in the deepest shit imaginable.

[yellowbeard]

The reason for the "planes will fall" hyperbole is because air traffic control, approach and airport towers use fixed frequencies - they cannot change frequency, inbound planes from all parts of the world rely on being able to enter in the frequency 118.500 and be able to speak to the tower at Heathrow for instance:

Code: Select all

http://www.lhr-lgw.co.uk/groupfiles/heathrowfrequencies.htm

Air traffic control has precedence, if the BBC were interfering with them the BBC have to shut down, never mind me or you.

[helpMUCHappreciated]

I see.

Thanks so much for your reply

[OgreVorbis]

Maybe you understand, but I thought I'd clarify: aircraft-band interference is not really a concern because it can easily be filtered out. The problem with most chinese transmitters is the in-band spurious. This in-band spurious also seems heavily overstated on this forum. Yes, there are chinese rigs that produce way too much, but the rigs based on BH1414K or Quintic chips are not bad. 5mW of spurious radiation is going to do nothing.

The people on here who don't have access to spectrum analysers automatically assume that all these transmitters can't be trusted.

But I guess for the novice it's best to just assume they're all bad because they don't know what chips to look for and don't have an analyser.

[teckniqs]

but the rigs based on BH1414K or Quintic chips are not bad. 5mW of spurious radiation is going to do nothing.

The people on here who don't have access to spectrum analysers automatically assume that all these transmitters can't be trusted.

But I guess for the novice it's best to just assume they're all bad because they don't know what chips to look for and don't have an analyser.

It's a 150w TX not a 5mW.

[Albert H]

[quote="OgreVorbis"] This in-band spurious also seems heavily overstated on this forum. Yes, there are chinese rigs that produce way too much, but the rigs based on BH1414K or Quintic chips are not bad. 5mW of spurious radiation is going to do nothing./quote]

NO! The BH1414K produces spurs at equal level to the main carrier at 76kHz intervals above and below the nominal carrier frequency. This mess MUST NOT be amplified.

The Quintic ICs are slightly better, but not much - again, if you amplify one, YOU WILL CAUSE INTERFERENCE.

The topic of this thread is a 150W Chinese interference generator. I'm thinking of buying one, just to put it on the bench into a dummy load and see how much crap it puts out. If it's clean, I'll be stunned, and I'll tell you all about it. If (as I suspect) it produces huge amounts of crap, I'll also let you know.

[Maximus]

5mw of in band interference can go quite a long way if you have a decent aerial. The old dears from down the road will be complaining that they can't listen to their bedtime stories on radio 3 or whatever it is.


Sent from my iPhone using Tapatalk

[surefm]

I Know this is an old post but how much power wattage wise do these stereo "broadcaster" chips put out before going to the P A ?

[Albert H]

How long is a piece of string? The "stereo broadcaster" ICs have various output powers - all of them in the milliwatt range. I have one here that develops around 32mW (it's a Quintic chip) for a 5V supply. The nominal (selected) frequency was set to 98 MHz. The "carrier" was actually just under 9mW of the 32mW of RF energy coming off the board. The other 23mW of RF energy was (mostly) within about 1.2 MHz either side of the selected frequency. It was a complete mess of stereo pilot harmonics, alias products from the stereo coder switching process, and various other noises. There were larger spur products - each complete with its own mess of modulation spurs in its vicinity - at 3.2 MHz either side of the selected frequency. The lower product had an aggregate power (with all its own spurs) for 7mW, and the upper one was around 5mW.

If this mess was put into a broadband amplifier, the milliwatts of rubbish would become Watts! If (please don't try this) it went through an amplifier chain up to a broadband 150 Watts, you'd be lucky to see the chosen frequency to be more than about 60 Watts of the mess. The other big spurs would be around 50 and 40 Watts - and remember - the band around each of these signals would have a significantly raised noise floor...... It would wipe out huge chunks of the band for miles around!

[surefm]

Thank you Albert for your detailed and quick reply, Do you think with time these broadcaster chips will improve or is the whole idea of these chips definitely a no go apart from using it to transmit digital audio to your car radio ?

[EFR]

I have some chinese rigs around and R&S CRTU, I can take some shots from them, if I get my hamcall out ofthe screen corner, I dont remeber how I get it there, and quick google search didnt help.

[Albert H]

They're fine for their intended application, I suppose. They're no good to amplify.

It's easy enough to build a simple, clean exciter - particularly if you use a well-designed kit - and some of the kits around are exceptionally good. There's no real point in using one of those nasty "audio sender" efforts.

[teckniqs]

Nice to see this thread back to life again.
I heard there's now a 300w version and apparently you can switch the stereo pilot off and they are clean.

....I've never seen or used one so I can't comment.

[radionortheast]

I have one of the bh kits coming, let anyone know if I find anything out, a few mw, looked like quite a big board, don't think i've had any with bh number in, to find out the milliwatts you'll have to solder an sma lead on, use a low value capacitor between if it has none, you can get little modules that measure milliwatts.

[Albert H]

Nice to see this thread back to life again.
I heard there's now a 300w version and apparently you can switch the stereo pilot off and they are clean.

....I've never seen or used one so I can't comment.

I have, and I can! Friends of mine in Indonesia made the mistake of buying one, thinking that it might be OK. As I warned, it wiped out most of the band for a couple of miles around their site.

I got a call (in the middle of the night!) asking if there was any way they could "filter it" to clean it up. I explained that there wasn't, and that they should return it to the supplier as "unsuitable" and demand their money back. A couple of days later, I got a further call, and they said that they'd fixed the problem:

A local radio amateur friend of theirs had desoldered the "stereo sender" chip from the board, and also disconnected the first amplification stage. This guy had then built a little 750mW PLL exciter, using a PIC and an LMX-series PLL IC. It was only mono, but it was all on one frequency. The Chinese board was just being used as a PA!

I've sent them a stereo coder board that I had here,and they should be able to get great results - without interference problems - for their little radio station.