Reccomendations for low power TX circuit?

Hamnchips · Post by **Hamnchips** » Wed Nov 18, 2015 12:48 pm

Hello Folks,

Just joined this forum, been into radio for a while and am getting into the electronics side of things. I've got some experience with old and new hifi stuff and have constructed a few things in the past.

As a laugh I bought one of those Chinese kits (7W PLL transmitter) off ebay. I assembled it and constructed a ground plane antenna with 4 x 45 degree radials pointing downwards. Results as expected are very poor. With the antenna in my loft the signal barely travels 3 doors away and sound quality is shite.

I wondered if someone could recommend a circuit I could look at, something similar in concept to this kit, only better designed? 5w-10w, with adjustable power output would be nice.

I don't plan on operating a regular rig, its just for fun at this stage to see what I can do with it and to test different antenna builds. The main purpose in the end will be to broadcast to receivers round the house, but with better audio quality and no spurious interference in other parts of the band!

Cheers

McDonalds · Post by **McDonalds** » Wed Nov 18, 2015 4:56 pm

The NRG Pro 4 ones for £100 seem OK.

teckniqs · Post by **teckniqs** » Wed Nov 18, 2015 8:16 pm

I think the RDVV15W is a good way to go, the new one has just came out and it's worth the money. It's adjustable power and push button tuning. RF-Head sells them and he's here on the forum.

McDonalds · Post by **McDonalds** » Thu Nov 19, 2015 12:39 pm

I wonder if your 7 watt was also on a high or low setting as seen some have this setting from 1 watt to 7?

radio-berlin · Post by **radio-berlin** » Thu Nov 19, 2015 3:41 pm

You defo blown it or built it wrong if you got it in kit form.

I bought the 7watt PLL Kit from china as was curious, it was about £18.
It puts out 7watts at 88, then only 2 watts at 108, you have to tune the coils to get 7watts at 108 which then leaves you with 2watts and less at 88. So its not broadband.
There are no harmonics as such however around the carrier its a really dirty spread about 4 mhz wide, its the stereo ic causing it. When I short out the stereo its clean but then there is of course no audio as its all built into one chip.
Also when I first powerd it up two resistors smoked right away, they have two tiny smd 100ohm resistors in line with the collector to the pre transistor 2053 (i think), so I had to replace them with normal resistors.
It works and does as it says on the tin, I did put it on a dipole for 30mins and went for a spin and was covering a good 5 miles.
But YES stay clear, they wipe out anything around you, defo not clean enough to run, especially not into an amp.
Ill post some pics of it on analyser soon

Hamnchips · Post by **Hamnchips** » Mon Nov 23, 2015 11:10 am

It is certainly possible I've knackered it. Initially I received no instructions with the kit, so had to assemble by simply looking at the pictures on the listing!

My kit seems to be of a newer variety, very little to actually solder on - the ribbon connector for the LCD, LCD buttons, 5 coils plus only 1 adjustable inductor, transistors and crystal. Initially I had the LCD connector on the wrong way round, thanks to the picture! After finally getting the instructions (in Chinese

, I flipped this around and the device works. Quite possibly this has damaged something..

I adjusted the only adjustable inductor present based on (google translated) instructions, but no real difference seen.

Power settings are on max, and power controls seem to work in as much as I can bring the power down to the point where its not audible.

My antenna may also be a bit shite and this stuff is new to me. I have a small length of 50ohm coax going to it, and I assumed this was correct for a 50 ohm antenna? I understand the type of antenna I've built should be roughly 50ohms, though have no kit to measure that exactly. All radials are 1/4 wave length, or as close as I could get.

I may have a go at knocking together a basic dipole and see how that works

Maximus · Post by **Maximus** » Tue Nov 24, 2015 1:03 am

Are the coils soldered in correctly? Sometimes they don't make proper contact because of the varnish/shellac not being scratched off the ends before hand.

Sent from my iPhone using Tapatalk

Hamnchips · Post by **Hamnchips** » Sat Nov 28, 2015 12:58 am

All coil connections check out fine, and on closer inspection, the ends of them are stipped and tinned anyway. Ill try a different antenna and frequnecy, and if no improvement will rob what I can and bin the rest

radionortheast · Post by **radionortheast** » Tue Jun 14, 2016 10:14 am

radio-berlin wrote: There are no harmonics as such however around the carrier its a really dirty spread about 4 mhz wide, its the stereo ic causing it. When I short out the stereo its clean but then there is of course no audio as its all built into one chip.

real shame these transmitters look so cool and are cheap

the instructions on ebay about been good at welding are confusing maybe a blow torch is needed to put one togeather, guess its someone with bad english.

don't suppose you could put audio in before the power, with a resistor before the negative rail, thought this is a stupid idea, managed to do that with little am transmitter in the past, saw a video someone using clock radios as transmitters on youtube where they would cut the coil, then connect their audio, dosen't seem like such a great thing to do.

Xerox · Post by **Xerox** » Tue Jun 14, 2016 11:09 am

Welding haha i seen it on there site as well. Lol lost in translation. Shame really - as imagin if they stole a veronica or a dutch design - with all them maggot dicked ****** workin like ants in there sweat shop they dominate the market - every builders nightmare. Kilowatt pll in stereo for 5 yen n a box of noodles.

Xerox · Post by **Xerox** » Tue Jun 14, 2016 11:13 am

I was told there production line is like the film NewJackCity - like a crack factory where they have to work butt naked in case they steal a diode.. lol

MiXiN · Post by **MiXiN** » Tue Jun 14, 2016 12:12 pm

These last 2 posts made me piss. Lol.

shuffy · Post by **shuffy** » Wed Jun 15, 2016 12:33 am

I'm told that once you've nicked a lot of diodes, it stops hurting.

Xerox · Post by **Xerox** » Wed Jun 15, 2016 11:25 am

Haha lol. Without humour what we got? Enoch Powels illegimate children with Thatcher.
OK seriously - yes diodes do stop the pain...
NRG kits - dutchrfshop.nl - rfelectronics.nl or is it hfelectronics.nl google these! Any distributer that ends with .nl is always a winner.
The PKBee board on dutchrfshop lo0ks nice for a 5watt driver - dunno if other people agree with me tho - probably not ; (

RF-Head · Post by **RF-Head** » Wed Jun 15, 2016 6:14 pm

yes www.hf-electronics.nl
This is a nice 6W driverboard http://www.hf-electronics.nl/Webwinkel- ... 6watt.html
Easy to built and can be used without the LCD
Has adjustable power and complete broadband

Xerox · Post by **Xerox** » Wed Jun 15, 2016 6:25 pm

Yes thats the one i was thinkin about but could remember adress off the top of my head

Reccomendations for low power TX circuit?

Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?

Re: Reccomendations for low power TX circuit?