It’s been a bit quiet around here lately – I’m just swamped with work, and it never quite goes away, but neither does the desire to do something for my own enrichment and enjoyment … and the desire to blog about it.

Seeing as I enjoyed reviving a few of Dick Smith’s Funway 2 Pocket Transistor Radio kits, I wondered if there was anything out there I could build which would be a little more attractive and perhaps slightly more sophisticated. I was aware of the Tecsun 2P3 which looks to be a very nice kit, but a bit on the pricey side for an AM only radio. So, I rummaged on eBay looking for radio kits, and surprisingly, there were quite a few! Sadly, a good number of them are very opaque in the sense that they rely on a digital auto-scan FM receiver chip and there really isn’t much to them aside from that and an amplifier chip.

I settled on one which was listed as CF210SP AM FM Radio Kit, with a few other “related” words thrown in. As expected, it’s a dual band (AM/FM) radio, with the whole kit coming in at a reasonable AU$7.99 including postage and comes complete with exterior casing. The big downside? Everything is in Chinese. The only English you will find is in the listing description, which isn’t particularly easy to read nor informative:

CF210SP is a new type of radio FM, AM two band radio, the FM band 
using the CD9088 chip, which uses patch element SMT package, the 
receive frequency range of 76-108HMZ, not only to accept the FM 
radio, can also receive campus radio and part of the audio signal 
of the television stations; AM band using direct IC the TA7642, 
receive frequency range is 525-1605KHZ circuit is simple, assembly 
success rate, a better selectivity having a little;. amplifier 
circuit using TD2822 special function ICs having loud. Sound 
quality is good.

While I am of Chinese decent, I’ll have to admit that I can’t read, nor write in Chinese. Even though the instructions are in Chinese, I didn’t feel that to be a big impediment because when it comes to components and schematics, the drawings and markings transcend the language barrier. Just another way engineering solves the day! Luckily for everyone, the board also has very good silkscreening to judge by the listing.

As a result, I accepted the challenge and put in an order for two kits. I suppose it’s just a habit – if you order kits, you know they come with just the right number of parts, so there’s no room for mistakes. Ordering two ensures that you have some spares in case things do go wrong …

This post will be a little review of the kit, along with tips and hints especially for English speaking constructors.

Kit Contents

Rather unimpressively, each kit comes in a bubble wrap package. Trouble was already spotted when a loose screw was seen rattling inside the bubble wrap – the components have broken loose and the only thing preventing them from going everywhere was a thin and somewhat torn bubble wrap.

The case for this was soon found – the components are actually wrapped inside a cellophane bag, but that sort of material has a tendency to tear when punctured by the sharp component legs – quickly the smaller components work their way out.

As you can see, inside the package, you get the case halves without anything populated, a front tuning label with the absolutely bogus Paeansonic band, the main PCB, the speaker, a telescopic whip, and a bag with the “rest” of the parts. It’s nice to see that the plastic shell has a captive battery door, which makes it a nice touch. The downside is that the moulding of the case is a little slack so the halves don’t fit together seamlessly with a few rough edges, and there are areas where the plastic was so thin that it cracked in transit and a little super-glue was needed. The components being bagged inside a cellophane bag may be cheap, but doesn’t respect the ESD sensitive nature of the ICs used, and is a recipe for bent pins.

Rather nicely, the PCB is a single sided paper-type board with silkscreening on both sides which is very descriptive, and solder mask on the rear. It seems to have a lacquer finish to stop the pads from oxidising, but is not otherwise tinned nor plated. There are some points on the rear for “tack soldering” wires, and a slot near the top to slot in a ferrite rod holder.

As mentioned, the instructions were all in Chinese. Unfortunately, the instructions are only a single double-sided sheet, so the educational value of the kit is somewhat limited. The schematic as listed is shown above. The CD9088 is responsible for FM reception, with the only datasheet I could find being in Chinese. That’s okay, because it’s a clone of the TDA7088 which is a mono FM receiver circuit. The unit has an IF of about 70kHz, and features a frequency locked loop with internal muting of weak signals. Filtering is achieved with the external components – mainly R-C filters.

The AM reception is being achieved with the CD7642. If you’ve had a feeling you’ve seen this before – you’re right. It’s exactly the same chip as used by the Funway kit mentioned earlier – one of them had a TA7642 but it is otherwise identical to the MK484 in being a tuned radio-frequency receiver, basically operating at the carrier frequency amplifying and pushing the signal through a bank of filters until it is finally detected into audio.

That leaves the TDA2822, which is a stereo audio amplifier chip to drive speakers and headphones. It’s not particularly fancy and is probably quiet hissy, and offers about 20mW into a set of 32 ohm headphones when powered from 3V. It is used to drive the headphone jack which disconnects the internal speaker once a headphone plug is plugged in.

Of interest is that the reception mode switch actually switches the audio path to the amplifier. Whenever the radio is switched on (by the volume switch that has an on/off detent), both AM and FM demodulation are taking place but just one of the signals is sent to the amplifier. I suppose this is a cheap way to do things, and the low-ish current requirement of the cells means that “wasting” half the power isn’t seen to be a major issue.

The rear has a “duotone” print image with drawn components overlaid, which makes it a handy reference in case the silkscreen is covered up by components.

There is also a list of parts included – 56 different “parts” in the table, but some values are doubled up – e.g. the 0.1uF ceramic disc capacitors on line 23, 24 and 25 with quantities of 6, 6 and 1 respectively.

Construction and Tune-Up Process

As an experienced kit builder, I wasted no time in getting started. I didn’t even bother to count all the parts as some people might do – I just started construction on the first kit right away and “learnt” a few tips along the way, which I will share.

Things You Need

No kit is entirely complete – there will be things you will need that don’t come in the kit. In the case of this kit, this specifically includes:

• About one to two hours of time to complete the kit.


• A container of some sort to empty out the components and sort through them, so they don’t get lost.


• An appropriate (~30-50w) soldering iron with a fine tip – the SMD chip absolutely demands it.


• Some solder – 60/40 is the “good stuff”, lead free is not as fun.


• Sidecutters to cut off component legs.


• Hot m