logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Analog AM Radio Receiver Without Chip - UL1111 Replacement with BC847CW Transistors

piotr_go  47 12990 Cool? (+39)
📢 Listen (AI):

TL;DR

  • A retro analog AM receiver for long-wave reception of Polish Radio Program I at 225 kHz replaces the UL1111 chip with discrete BC847CW transistors.
  • The circuit uses SOT323 and 0402 parts, a 1.5V cell, and headphones that can be switched in parallel or series with underside jumpers.
  • One ferrite version uses a 5mm x 50mm core, L1 wound with 20mm of 0.1mm wire and L2 with 17 turns of 0.15mm wire.
  • It receives loudly enough, and it also picks up interference from computer converters, light bulbs, and other electronics unless you keep your distance.
Generated by the language model.


Hello.
This time analog retro. The AM receiver on the basis of the article from Young Technician from the 1980s. Radio to receive "Polish Radio Program I" on long wave, at 225kHz.
The UL1111 radio is the first chip I have assembled. It was a "RADIO HOBBY" set bought around 1990.
In the presented UL1111 receiver I replaced with BC847CW transistors. To make it not too easy, the smallest size elements I had, SOT323 and 0402.
I used headphones from walkm ... phone. By means of jumpers on the underside of the PCB, the headphones can be set to be connected in parallel or in series.
The whole is powered by a 1.5V cell.

Reception like reception, the radio is heard loud enough. By the way, you can listen to converters in the computer, light bulbs and other equipment :) .
It's best to keep your distance from all modern electronics.

Diagram:


I have kept the original item numbering, so you can read the exact description in the article from the link.

PCB:


Antenna on ferrite with ...:

Ferrite dimensions: 5mm x 50mm
L1: 20mm wide, 0.1mm wire
L2: 17 turns, 0.15mm wire
Ferrite probably from the Neptune monitor. It lay in junk for over a quarter of a century.
0.1 wire from the choke from TV Lazuryt. Also 25+ So that retro antenna. :)

Antenna on ferrite from "DCF" (including: WVB-0860N-03A):

Ferrite dimensions: 8mm x 60mm
L1: 25mm wide, 0.15mm wire
L2: 14 turns, 0.15mm wire

Between the ferrite and the PCB, I put a laminate pad on one side and fastened the whole thing with cable ties.
Thanks to this, you can freely move the coil along the ferrite.

Tuning L1:
Wind the antenna on a non-tightly rolled (so that it can be moved) piece of paper.
We wind a little more turns. If the strongest reception is when the coil protrudes from the ferrite, then we have too many coils (unwind a few and check again).
How it picks up in the middle is not enough. We aim with the number of turns so that the strongest reception is between the center and the edge.
Attachments:
  • radio_am.tar.gz (185.74 KB) You must be logged in to download this attachment.
About Author
piotr_go
piotr_go wrote 2904 posts with rating 3336 , helped 94 times. Been with us since 2003 year.

Comments

Mateusz_konstruktor 03 Oct 2022 00:08

The first picture confuses this chip. I made a lot of research about where to find it in the diagram and where all the additional individual transistors come from ... It would better make sense of something... [Read more]

piotr_go 03 Oct 2022 00:45

I put for a size comparison. Ordinary 2 * 16?. UL1111 sounded quite quiet from what I remember, although I don't know if it was a matter of headphones or boot errors. Anyone have a schematic... [Read more]

Mlody_Zdolny 03 Oct 2022 10:25

Perhaps it is the same diagram as in MT, there was even an implementation on the electrode https://www.elektroda.pl/rtvforum/topic3100861.html It's probably in a detector radio with no power... [Read more]

bsw 03 Oct 2022 12:00

I've been thinking about this radio for several years now. I remember when a friend made one in the 80's - then it was something! So, after more than 30 years, I wanted to do it myself. But I... [Read more]

minus3db 03 Oct 2022 13:03

Kind of retro - and the modern, beautifully made tile definitely gives it the charm of its second youth :) I remember that 30 years ago I tinkered with a little radio from Wojciechowski's book "Modern... [Read more]

bsw 03 Oct 2022 13:41

The basic problem is that our country is always run by short-sighted idiots. We used to have one of the strongest radio stations in the world with the world's tallest mast in Konstantynów. You could... [Read more]

katakrowa 03 Oct 2022 13:43

Probably not the same scheme but a similar idea. https://obrazki.elektroda.pl/9416525400_1664797371_thumb.jpg https://obrazki.elektroda.pl/7728801100_1664797371_thumb.jpg https://obrazki.el... [Read more]

Mlody_Zdolny 03 Oct 2022 14:32

You mean medium waves? LW and MW transmitters are disappearing because they are uneconomical. AM modulation is very energy inefficient and low quality of the presentation. How many audiences are currently... [Read more]

bsw 03 Oct 2022 16:34

Yes, but I was talking about the situation 30 years ago. 7 years of building a new broadcasting center, which was completely pointless ... [Read more]

piotr_go 03 Oct 2022 19:54

Initially, it was supposed to be on UL1111, I also combined something with TA7642, I even bought THT capacitors / resistors (SMD is in abundance with us). In the end, I opted for transistors (I also bought... [Read more]

Simon79 03 Oct 2022 21:01

Do you have any bad experiences with this scalak? In my opinion, it works like any other radio. In total, for over 25 years I have made a dozen (AM and FM), from detector, tube and transistor ones, through... [Read more]

piotr_go 03 Oct 2022 21:13

It was waking me up, but it was probably the antenna's fault. I have to check on the new one again. What can you pick some smaller ferrites from? (5mm * 50mm) Any chokes or something? I searched... [Read more]

Mlody_Zdolny 03 Oct 2022 22:12

Older Dior receivers, turn-of-the-century "dachshunds". Available in olx or at a flea market at a ridiculous price. The ferrite rod can be easily shortened by cutting the groove with the dremel and breaking... [Read more]

piotr_go 03 Oct 2022 22:19

I was thinking of something cheap and generally available like these DCF modules. It's a pity to break one radio to make another. [Read more]

Mateusz_konstruktor 04 Oct 2022 22:49

Not. The point here is that the radios were designed to connect headphones with an impedance of 100-400?, with an impedance of headphones of the "Walkman" type, probably 32?, and people were looking for... [Read more]

Mlody_Zdolny 05 Oct 2022 00:06

What were they supposed to design here? The handset is in series in the collector circuit and behind. The lower the resistance, the more power and the stronger the sound. A resistance of 32 ohms is approximately... [Read more]

Krzysztof Kamienski 05 Oct 2022 03:08

Ya ... and what is the voltage drop at the CE connector even of a saturated transistor? [Read more]

Mlody_Zdolny 05 Oct 2022 09:36

Tia, the power on the transistor at 50 mA and Uec = 1.5 V is 75 mW, the catalog Ptot for a single transistor is 300 mW. The voltage Uec contributes to the collector current drop in a directly proportional... [Read more]

bsw 05 Oct 2022 09:59

When connecting two channels of headphones in parallel, the resultant impedance is 16ohm, but you can connect in series - i.e. connect the jack between R and L without ground - then the situation is b... [Read more]

FAQ

TL;DR: A 100 W medium-wave transmitter 1 km away caused audible distortion; “desoldering R6 improves reception” [Elektroda, piotr_go, post #20227305] Replacing a UL1111 IC with six BC847CW SOT-323 transistors keeps the 1.5 V pocket-radio spirit alive. Why it matters: the FAQ shows how to revive long-wave/medium-wave listening with easily sourced parts.

Quick Facts

• Supply voltage: single 1.5 V AA/AAA cell [Elektroda, piotr_go, post #20218554] • Headphone load options: 32 Ω–400 Ω; series wiring gives 64 Ω, parallel 16 Ω [Elektroda, piotr_go, post #20218731] • Long-wave coil (225 kHz): L1 ≈20 mm wide, 0.1 mm wire on 5×50 mm rod; L2 = 17 turns, 0.15 mm wire [Elektroda, piotr_go, post #20218554] • Medium-wave retune: ~60 turns, tuning cap 30-220 pF [Elektroda, PiotrPitucha, post #20234649] • BC847C hFE: 110-800 (typical) [NXP, 2021]

1. Why replace the UL1111 with discrete BC847CW transistors?

UL1111 chips are scarce; six BC847CW transistors recreate its four-stage topology, fit SOT-323 pads, and cost < €0.10 each [Elektroda, piotr_go, post #20218554] Discretes also let you tweak bias resistors and gain for LW or MW use.

2. Does the receiver work with modern 32 Ω earbuds?

Yes, but in parallel the load is 16 Ω, drawing ≈46 mA at 1.5 V—near the 50 mA Ic-max of one UL1111 stage [Elektroda, Mlody_Zdolny, post #20221744] Series wiring (64 Ω) halves current and reduces distortion.

3. How do I wind and tune the long-wave coil?

  1. Wrap L1 on loose paper so it slides on the rod.
  2. Add extra turns; slide until signal peaks.
  3. If peak occurs off-center, remove or add turns until it peaks midway [Elektroda, piotr_go, post #20218554]

4. What changes are needed for medium-wave (530-1600 kHz)?

Use a 5×50 mm rod with ~60 turns of 0.1-0.15 mm wire and a 30-220 pF tuning capacitor; reduce C5/C6 values accordingly [Elektroda, PiotrPitucha, post #20234649]

6. Where can I source small ferrite rods today?

Salvage 5-8 mm rods from old DCF77 clocks, chokes, or 1990s portable AM radios; shorten with a Dremel groove then snap [Elektroda, Mlody_Zdolny, post #20220152]

7. Are TA7642 or CD7642CP drop-in IC alternatives?

Yes. TA7642 and its clone CD7642CP in TO-92 house an entire AM receiver needing only an LC tank and audio amp [Elektroda, TechEkspert, post #20943244] They run from 1.1-1.6 V and draw ≈0.3 mA (datasheet).

8. How does the ANL diode noise reducer work?

The audio from the detector feeds a 1N4148 biased by the AGC line. Impulse spikes reverse-bias the diode, clipping noise while leaving speech intact—tech used in CB sets [Elektroda, robert123, post #20962042]

9. Can I build a zero-voltage-drop detector?

Use a depletion MOSFET (e.g., ALD110900) with gate tied to drain; it acts as an ideal diode but is ESD-sensitive and costly [Elektroda, PiotrPitucha, post #20242097]

10. What battery life should I expect?

With 64 Ω load the radio draws ~20 mA. An alkaline AA (2000 mAh) yields ≈100 h. At 16 Ω load current doubles, cutting life to ~50 h. Add an LED low-battery indicator if critical.

11. Edge case: What happens if R6 is removed entirely?

Audio volume drops because T3 no longer biases T4; C6 current becomes unidirectional, reducing gain by >12 dB [Elektroda, Mlody_Zdolny, post #20227442]

12. How can I reduce part count further?

Replace T3-T5 with a single rail-to-rail op-amp like LMV951; at 1 V supply and 2.7 MHz GBW it rectifies and amplifies audio with three passive parts [Elektroda, PiotrPitucha, post #20243680]
Generated by the language model.
%}