1946

[radium98]

this what i used as driver output for covering a 1o km city with a tuned fm linear but with 2sc1946a 35w i would ask a volunteer if he have a easy tune or even no tune design with pcb layout or any can design me one so i can use this old transistor c1946a that i love a lot all what i have in my hands are tuned with variable cap .

[Albert H]

The 2SC1946a is an old-fashioned device, designed for 25 Watt land mobile PAs. They have about 10dB of gain, which means you'll need about 3.5 Watts of drive to get your 35 Watts. The device is actually rated for just 30 Watts, and I'd be inclined to run it at 25 Watts - you wouldn't notice the difference, and it would withstand abuse better. The gain won't be so high in a "no-tune" circuit, so you'll probably need 4 - 5 Watts of drive (2SC1947 or MRF 237 or 2N6080).

These days I'd abandon the use of old bipolar transistors - they're low gain, not very robust, and extremely expensive. These days I'd use the Mitsubishi FETs - the RD30HVF1 will give you an easy 30 Watts for just ½W of drive at 12.5 Volt supply in a simple, no-tune circuit.

[teckniqs]

The coils on the circuit are missing. That device looks like the 2N5591 popular in old 12v Taxi and Mobile PMR radio equipment, rated at 25w and with some good cooling pretty good for around 35/40w.

[radium98]

thank you for ure contributions guys but i would really like to use it Albert my problem is i dont have thoses fet transistors in my hands and all are fake i only have that rd15 but dont have a push-pull way .

[teckniqs]

Once your coils have been replaced, the first trimmer on the output could probably do with upgrading to something like a blue spot to handle the power. And you'll also need a low pass output filter.

[radium98]

RwgEULZ.jpg

@teckniqs this what i have and an output is between 18-20w from bly88c but i have to tune how i can make it no tune or even easy tune one variable capacitor

[radium98]

can anyone issue me a link for a full circad software or some software that handle to convert this file to pdf that i can print out the layout thanks
https://www.sendspace.com/file/4lo57v

[gurudattapanda]

Dear Radium98,
Can I get the Circuit Diagram or Schematic of the 2N5591 based amplifier, whose photo you have posted above?
I have a single 2N5591, and want to make a 25 Watt amp for my 7 watt FM transmitter.
Please help.

[teckniqs]

I know this is an old thread but if anyone wants any, there seems to be a seller with old MRF1946 power amps with 2sc1971 drivers on eBay for a fiver:

https://www.ebay.co.uk/itm/2SC1971-and- ... :rk:1:pf:0

[rigmo]

this what i used as driver output for covering a 1o km city with a tuned fm linear but with 2sc1946a 35w i would ask a volunteer if he have a easy tune or even no tune design with pcb layout or any can design me one so i can use this old transistor c1946a that i love a lot all what i have in my hands are tuned with variable cap .

IS this ever run?
https://www.facebook.com/k19radio/posts ... nqPnmJrWQl

[Albert H]

RwgEULZ.jpg@teckniqs this what i have and an output is between 18-20w from bly88c but i have to tune how i can make it no tune or even easy tune one variable capacitor

To be honest, you're not going to notice much difference in coverage from 18 Watts to 30 Watts.

You have unrealistic expectations, too. "No-tune" amplifier stages are considerably less efficient (especially with old bipolar transistors) - with those devices you'd be lucky to see 6dB gain in a no-tune circuit. Amplifiers using those devices were always critically tuned.

I've had no problem getting genuine FETs - just go straight to the main distributors. I just bought a couple of 70 Watt Mitsubishi FETs for about £12 each. If you go to "Enigma", you'll get genuine parts.

[rigmo]

I find this Notes still not dead even today 05-Feb-2009 06:31
-----

- Use silver mica caps in RF sections
even better are metal clad micas (www.rfparts.com)
- Use non-inductive resistors (metal oxide, most metal film) in RF sections
and for parasitic resistors
- Use a large ground plane
- Tune for EFFICIENCY, not for high rf output
- Don't run parts at their maximum ratings
- Use BNC connectors below 5 watts, N connector above DON'T USE PL-259/SO-239
- nte320 appears to be a replacement for the mrf240
- mrf238 = 2n6084 = blw60
- the led in the ipa does not behave linearly, so dont use it for
power adjust, just as a indicator for rf input
- bipoler RF amps are dead. use mosfets
https://www.aliexpress.com/item/1703862946.html?s