Amplifier inductor question

[OgreVorbis]

I am thinking about building this amp, but I don't have the green toroid shown here:
http://www.3-mtr.info/sales/Amplifier%2 ... gineel.JPG

I can't have too much inductance here, right? It is just to feed the power into the transistor and prevent the RF from going back to the power supply, so can I just replace that toroid with a longer coil than the one on the left?

Here is the full schematic if interested:
http://www.3-mtr.info/sales/Amplifier%2 ... ctions.pdf

[Analyser]

Pretty much correct, yes, although the coil feeding the drain would be a different matter. A lot of people use the VK200 type of thing which is a small ferrite with a few turns in the core.

[MiXiN]

Sorry to go off topic, but does anyone know if these are available for sale anywhere?

An amp at this power running on 12v would be much convenient than one that runs on 24 or 48V for me.

[shorty]

They are available from free radio berkeley

http://www.freeradio.org/index.php?page ... _kits.html

If you order one it's unlikely you will get it, from comments on the old forum he's not that reliable in sending what you have paid for you wait, wait, waittttttttttttttttttt, then end up trying to get a refund.

[MiXiN]

They are available from free radio berkeley

http://www.freeradio.org/index.php?page ... _kits.html

If you order one it's unlikely you will get it, from comments on the old forum he's not that reliable in sending what you have paid for you wait, wait, waittttttttttttttttttt, then end up trying to get a refund.

I've seen a couple of that guys YouTube clips and he looks like a bad baghead if it's the same guy with long hair.

Hopefully, someone more trustworthy will start to market them.

I think these or variants using the RD30HVF1 would sell really well as there must be a few of us, including me, with beefy 13.8V power supplies that arent being used to their full potential.

[teckniqs]

I've seen that strange redneck looking guy and wouldn't be in a hurry to part my cash with him.

...It's the RD70 in this one mate.

[MiXiN]

I've seen that strange redneck looking guy and wouldn't be in a hurry to part my cash with him.

...It's the RD70 in this one mate.

Hahahahaha, yeah, he's one weird sweaty looking guy. Not the kind of bloke I'd let babysit amongst other things. Lol.

Yeah, I know the RD70 is used in this one, but a RD30HVF1 version would be nice as well.

I already have a Turkish amp and an Enigma one using the RD15HFV1, but would like some bigger boots now.

[OgreVorbis]

Pretty much correct, yes, although the coil feeding the drain would be a different matter. A lot of people use the VK200 type of thing which is a small ferrite with a few turns in the core.

Good. I think I have a some of those. I'll probably need two though because the wire is very thin for the amperage.

Another question: I noticed his PCB looks like it has a few vias around the transistor. Would using a single sided copper board effect output power?

I think these or variants using the RD30HVF1 would sell really well as there must be a few of us, including me, with beefy 13.8V power supplies that arent being used to their full potential.

Same for me. These transistors are the highest power of the 12-13V ones. Even the new freescales don't go any higher at 12V. I have enough components to make 3-4 boards, so if you really want one, I could make it. Keep in mind it will be a homemade PCB and not very "pro" looking. Also I'm leaving out the pre-amp on mine, so you'd need about 5-7W input.

If you order one it's unlikely you will get it, from comments on the old forum he's not that reliable in sending what you have paid for you wait, wait, waittttttttttttttttttt, then end up trying to get a refund.

I already contacted him weeks ago and there was no response. Clearly he's too busy tripping all the time to send orders haha.

[pjeva]

The guy you are talking about, was in jail few times. As I remember, he organized protests against FCC (American OFCOM) because he supports freedom of airwaves, and actually has school for pirate radio enthusiasts! So maybe he's doing time as we speak...


Sent from my iPhone using Tapatalk

[pjeva]

@OgreVorbis: try to ask one question at the time. It would be easier for us to quote you and easier to recognize what answer belongs to what question.

Here's one answer: you can put 2 VK200 in parallel to reduce current on thin wire


Sent from my iPhone using Tapatalk

[pjeva]

Regarding single sided pcb, it is not usable at RF, and for sure not to be used on higher power


Sent from my iPhone using Tapatalk

[Sietedj]

Sorry to go off topic, but does anyone know if these are available for sale anywhere?

An amp at this power running on 12v would be much convenient than one that runs on 24 or 48V for me.

I'm also looking for a 30w amplifier and this is something I've found if you are interested.
A greeting!!!
http://www.ebay.es/itm/FM-Broadcast-Pow ... 1742556625

[OgreVorbis]

I have one of those 30W amps. The guy soldered the transistor backwards and it shorted out. He said that all his boards are tested and wouldn't give a refund. You might get lucky, though.

I have this chinese one. It's pretty good, but a bit expensive. I checked it on an analyzer.
http://www.fmuser.org/RF-Power-Amplifie ... t-30W.html

[OgreVorbis]

Regarding single sided pcb, it is not usable at RF, and for sure not to be used on higher power

So I would have to use a double sided PCB with vias where I place a wire through and solder both sides?

Thanks for the help!

[Analyser]

Regarding single sided pcb, it is not usable at RF, and for sure not to be used on higher power

So I would have to use a double sided PCB with vias where I place a wire through and solder both sides?

Thanks for the help!

Not really. You can use a single-sided board but screw it down to the heatsink in several places, the heatsink will act as the lower layer. If you really want to go crazy with grounding the emitter leads you can pass copper foil from the top to the bottom side near where the emitter leads contact the board, if you don't have that then a few screws passed through the board in to the heatsink near those leads will do.

[Sietedj]

I have one of those 30W amps. The guy soldered the transistor backwards and it shorted out. He said that all his boards are tested and wouldn't give a refund. You might get lucky, though.

I have this chinese one. It's pretty good, but a bit expensive. I checked it on an analyzer.
http://www.fmuser.org/RF-Power-Amplifie ... t-30W.html

Ok thanks for the information. Right now I'm just looking, I'll buy it later.

[Maximus]

Looks a bit dodgy to be fair. I'd rather pay £40 for one of those 100w DIY Chinese copy amp boards. It might not last for long, but will most certainly be fun to build.


Sent from Tapatalk

[Maximus]

I'm quite lucky being able to buy 2U 19" for just over a tenna. Plus massive heat sinks for a fiver.
Goodness knows what the x-ray dudes will think of a suitcase full of electronics lool


Sent from Tapatalk

[pjeva]

Not really. You can use a single-sided board but screw it down to the heatsink in several places, the heatsink will act as the lower layer. If you really want to go crazy with grounding the emitter leads you can pass copper foil from the top to the bottom side near where the emitter leads contact the board, if you don't have that then a few screws passed through the board in to the heatsink near those leads will do.

This with heatsink used as second layer can be used but you have to put a lot of screws and you need to drill lot of holes on the heatsink to be sure that you have good ground. I think it may be easier and cheaper to buy double sided pcb and solder wire links between


Sent from my iPhone using Tapatalk

[shuffy]

I've seen a couple of that guys YouTube clips and he looks like a bad baghead if it's the same guy with long hair.

Showing my age here I know but In the early 90s he was quite outspoken on the scene and a bit of a legend... most of us used the usenet group alt.radio.pirate which was all we had by way of a forum, and the nature of usenet being what it was, there were a lot of Americans on there and relatively few Brits including myself. As for the chap from FRB, I expect time and other things have caught up with him since then

So, on to his RD70 attempt. He's done his best with the matching on this amp to make it broadband however due to the low impedances it's still quite critical and therefore with this design I'd be impressed if he manages 70W across the whole band, if at all. Most other designs I've seen using these 12V Mitsubishi FETs drive the RD70 with an RD15 using the extra power to compensate, however that's swings and roundabouts with some of the designs and you've got to watch that bias current. In short, with this design, your mileage may vary - expect to do a bit of "tweaking" to get the power you want.