bh1417f experimental transmitter

[radionortheast]

Managed to finish messing about with this experimental transmitter, It is possible to connect your own stereo encoder to it, it is also possible to use it as a stand alone encoder, seems likely the oscillator would pick up hum. It has only 8 selectable frequencies, don’t think there is anyway to change that, noise is lower than other chips in the fm band, bit noisy 1Mhz round the signal. I'm guessing there are no other chips out there were you could connect your own stereo encoder?

[Krakatoa]

The BH1415F can do any channel on the FM band, but ypu need a microcontroller to program it serially.
Anyway, both BH chips have outputs of MPX and 19kHz signals so it is possible to cleanup their mess with external filters.
The other thing I should try some day is to use an external oscillator stage, and only feed the PLL part of the chip. That should isolate the generated RF from the noise inside the chip, and make it a "decent" transmitter.

[oazz]

It is possible to give MPX signal from Stereo Tool.

[Albert H]

TBH, all of these "audio sender" ICs aren't worth bothering with - they're fine for their intended function (connecting an audio player to a car radio wirelessly), but ALL of them are filthy when amplified.

If you want a cheap, simple, reliable, clean low power stereo transmitter, get a kit! Don't go near the A****F junk, though!

[FMEnjoyer]

Where are the 500mW, stereo, PLL, no spurious and harmonics, efficient, tiny, light, easily available, easy to use available for £20.00 or even £60.00

Surely if a chip is relatively clean which one of note seems to be, then any amplification should be clean unless it is non linear, though I know little about how RF amps work.

There are probably people who could be interested who don't want to run a station on a block but 100pct of people do not want to cause interference even to their neighbours. There are a lot of people who do not find RF trivial as you suggest as there are 1,000's of people interested in a little built rig compared with those who can make them properly.

Design, make and supply them Albert, your legacy product to the masses, that would be a real statement.

[radionortheast]

Where are the 500mW, stereo, PLL, no spurious and harmonics, efficient, tiny, light, easily available, easy to use available for £20.00 or even £60.00

I do think you are right, there is no shop that is selling kits, used get little transmitters from pcs, it became harder after brexit, they nolonger have on all inclusive price at the checkout, there is noone on ebay uk selling the kits, often do get people posting links to websites like dutch shops, were you likely have people chasing you round after for vat handling fees, the Chinese transmitters will come without a problem, with ali they pay vat.
I have my own signal generator which puts out a clear signal, with my stereo encoder too, I don’t need the bh, I might post details of it sometime, they are ready available modules you can get easily, they are not plug and play, delicate soldering is required and an omp amp audio buffer is needed. I have the +5.8db output through a little amplifier, with a low pass filter on the end, puts about a watt on 12v doesn’t even get warm. I’ve been looking around to see if any chips could be good enough to put through it, it would easier to do with the stereo taken care of by the chip, just a matter of getting the +5.8db.
I’ve never properly tested the bh, the output from it was coming through crappy amplifier, I did find a duplicate signal relatively small, Krakatoa is saying is true, it could well be cleaned up, not saying they are great, the bh chips do seem to have stuff outside of them.

[FMEnjoyer]

They key points would be..

1) Stereo PLL
2) Tiny and light
3) 500mW (or even 300mW) robust can take a telescopic like the Chinese one in worst case situation
4) A lot to be said for 5v power from USB C Type
5) Stable and not sproggy
6) Easily driven, the PCS stuff needs a massive audio signal for some reason
7) Affordable, not £20.00 affordable but at scale these could be £50.00 surely ?
8) Available with ease.
9) Ready built, many have zero interest in building

I don't see where they are either northeast. And yes in UK would be the ideal though I think you only
get stuffed by Brexit import and courier if it is more than a certain value.

Maybe if a UK designer won't do it the Chinese will using a QN8007 and sell it for £35.00 delivered. Would be better than the QN8027 which
I think are amazing really but unusable due to sprogs generally.

For hobbyists mess arounders who don't want to interfere, not tower block radio which has broadly had its day.

[yellowbeard]

I wouldn't design with it and I wouldn't buy a transmitter with it in. I can get RDS and stereo encoder modules delivered from the Netherlands for €50 yoyos and build up an exciter for about €20 - for me that's game over for any of them chips.

[FMEnjoyer]

I wouldn't design with it and I wouldn't buy a transmitter with it in. I can get RDS and stereo encoder modules delivered from the Netherlands for €50 yoyos and build up an exciter for about €20 - for me that's game over for any of them chips.

One big difference, you can build the PLL exciter. Most cannot.

€70 DIY vs £20 built.

I don't expect it to be the same price if it works much better, but somehow they don't exist ready made, that's the main issue really.

Found these kits:

https://dutchrfshop.nl/en/diy-kits-pcb- ... -watt.html

https://dutchrfshop.nl/en/drfs-parts/51 ... tt-v2.html

€85 build it yourself, test it yourself, no stereo, not in UK. Would be quite unfriendly for some hobbyists.
Plus whatever it costs to get it into UK which is unknown.

[jvok]

For a while you could buy the zozo 1w pll ready built on ebay which ticks most of the boxes, think it was 45-50 quid. Can't find them any more though

[Albert H]

The problem with the whole concept is that a kit is (mostly) impractical - getting beginners to solder a bagful of components neatly into the right places in a PCB, wind coils to the right specification, and then test is impossible. If there's anything that could go wrong, it would!

Your average kid with a soldering iron isn't going to have the instruments needed to calibrate a transmitter - dummy load (though a couple of resistors could do), multimeter, frequency counter, a means of detecting harmonics and spurs and so on....

[Krakatoa]

The only way these all-in-one chips could get my attention is if they could be configured for MPX output instead of sproggy RF only.

DSP processing nowadays has become so versatile and low power that they could make a chip that could include dual band agc and limiter, RDS and oversampling stereo encoder.
The RF part could then be taken care separately, in another circuit, isolated from the digital noise.

[FMEnjoyer]

I think the concept of the 500mW little TX's which are about £20.00 or less is superb. Built ready to go.

But the QN8027 is

This is why the next best thing is the QN8007 for such devices running really low power that would be ok. And as the Chinese seems tooled up for this surface mount stuff.

The kits.. I can solder quite well but I don't want to box it, wire it, add a load of connectors, test it, align it, and then it's mono untill you fork out more for Stereo encoder and PSU. I am sure those kits are good quality and they are a worthy option no disrespect to them or the PCS stuff which is also good. The dutch shop even sells BH1415F chips.

Very good value, I think they are 15 and 25W and stereo for not much money. Bear in mind any tax and import, courier etc on top.

https://www.pcs-electronics.com/shop/fm ... -exciters/

And will definitely suit some people.

But for an hour or 2's fun for 2-3 miles station-on-a-stick, not viable as there is a risk of interference and unless you are a grade 1 berk you don't want to do that. The 500mW Chinese rigs are feather light, they weigh about the same as 3 pound coins. There is much to be said for a stereo rig in a box with minijacks and all that for a very low price.

I wish they would just put a QN8007 in them. It would be a step in the right direction. Or someone in Europe design
one with it in.

[shuffy]

I wish they would just put a QN8007 in them. It would be a step in the right direction. Or someone in Europe design one with it in.

In terms of small pre-built TX's or exciters, I don't think anyone's going to compete with the Chinese economy of scale. Most of their customers aren't going to care much if they can hear something on the frequency they select. So I can see where you're coming from with this, it would be best if these guys were more responsible with their exciter designs instead of just going for margin. Can't see it happening though. Has anyone seen a Chinese board that DOESN'T use one of these BH/QN things? I touched on this in another thread but does anyone know if the larger (150W+) boxes these guys sell are also using them?

Someone posted something earlier from facebook, I think it was a Polish design. Couldn't find a circuit diagram but the feature list looked like it might be using the Q8007 (or whichever chip supposedly can do RDS). Also looked at his .net code on github, but it's not giving much away. So if he's using a Q chip, I guess he's just transferring the RDS parms into a microcontroller first.

For kits - I'm sure the small Chinese boxes have killed a big chunk of this market. It will have taken out those buyers who want a small TX for some reason and aren't interested in the technical aspects of their signal. I've never been big into kits but for an exciter, I think the NRG PLL PRO's had many of the important aspects nailed (apart from the size of the PLL but that design keeps the components commonly available and less likely to go obsolete like the old PLL ICs I still see people trying to get hold of). I had a quick look and didn't find anyone selling these at the moment, so that's a shame. Dutch stuff looks pretty good these days though.

@Albert & Yellowbeard do you remember the Ramsey FM10 discussions from the 90s on Usenet? That's 30 years we've been talking about these chips! Probably since the BA1404 appeared.

[FMEnjoyer]

150W on a chip, even the best one would be a very scary proposition.

A clean, tiny, PLL stereo, mini jack input, would be a handy, fun thing.

What I like is the survivability of a mismatch which they clearly can take using half of a dipole or GPA - an SMA coupled telescopic whip antenna, which is even supplied. Not at all suggesting a mismatch is recommended but makes it last longer than 1 wrong antenna match.

You can super easy crocodile clip the other leg of a dipole on the SMA negative/ground side - or 3 solid core hook up wire radials, that alone probably doubles the range. Maybe it is a 1 - 2 Watt output transistor running at 350mW or so and can take any mismatch heat ok.

I think I have said what I can now, you never know maybe someone in China starts to use the QN8007 in the 500mW ones and that will be something at least.

Happy xmas all.

[jvok]

Last time I tried to order from PCS it was like 50 quid just for shipping. Gave up and went to DRFS instead, boards were more but still came out cheaper after shipping. DRFS labelled the box as a gift worth £50 too to beat the import tax

Ive had an idea rattling around in my head for a while for a cheap 1w pll using 7400 logic and rd01 fet for the output, all smt so you could have somewhere like JLC rattle off 50 of them and sell on ebay for cheap. Think those rd01 fets will take a 50:1 mismatch so should be pretty robust. Stereo could be done in dsp with an fast-ish stm32 micro (<£5) and a cheaper 192khz codec ic for adc/dac.