Looking at the Insides of the Tecsun R-308 and Eton S350 DL

"Scooby" takes a close look at two similar radios for our edification:

I took apart my R-308 today, just out of curiosity. I found good and bad things when I looked inside.

The bad thing is that the ferrite rod is rather short, at about 5" long. I was hoping there was a longer one in that big radio case, but it seems to do well with the 5" rod.

The good thing is that the tuning mechanism is better than what is found in the S350/S350DL radios. It is believed that some of the S350 series radios have mechanical drift due on AM to having one dial string operate both of the separate AM and FM tuners. I had always thought a gear based mechanism would make better sense, since the string is spring loaded and causes the tuning to recoil slightly. There is one spring on each tuner pulley, and it appears that one tuner springs back against the other tuner after turning. This is why you can sometimes get it to stay on frequency better (with AM) by tuning slightly past the station and then tuning back to the station.

The tuning on the R-308 is gear driven, just as I thought would have worked on the S350. The tuning on the R-308 doesn't drift on AM at all. There is a dial string that operates the dial only, but not either the FM or AM tuner.

I was glad to see separate tuners for AM and FM, like on the S350DL, as it appears to be a better setup than having AM and FM together on one tuner.

I still like the R-308 as a basic radio to use around the house and out in the backyard. My second one should arrive soon.

AREAS FOR IMPROVEMENT

1) The tone control is simply a bass boost, and it only kicks in when you are near the bottom of the slider's travel. I would've made it control the bass in a more linear manner, and I would've liked a treble control right next to it. The bass boost is nice, as it improves the sound when listening through the speaker, and headphone listening sounds better when the bass is decreased.

2) The headphone jack is wired for stereo, but has the phases switched (like on the original s350). This does allow it to work with either a mono or stereo headset, but the bass response is lost when using a stereo headset. The solution to get good bass response when using a stereo headset is to use a mono to stereo adapter. I would've used either a mono jack or a properly wired stereo jack.

3) The sound output through the headset jack is too loud, meaning that you get a noticeable audio hiss when the volume is turned down. The original s350 also suffers from this, as do many other portable radios to some degree or another. The easy solution is to use an inline headset volume control, available from Radio Shack. I simply turn down the volume 50% on the inline control, and then I can listen quietly with absolutely no hiss. A complex solution would to be change out a resister or two in the radio, which I've only tried on one radio before. I probably won't get around to it with the r308, as I like using the inline volume control with my headphones anyway.

4) The dial pointer is not quite as accurate as I'd like. It's not too bad, and it is probably a result of cheap Chinese mass production. I can probably move the pointer up on the string a couple of millimeters and improve things considerably, but I'm already used to finding my favorite stations on the dial as it is now.

5) A dial backlight would be nice.

6) I've heard reports that people have difficult getting some brands of batteries to fit in the radio, but mine doesn't have this problem. Duracells, Energizers, and my cheap zinc chloride batteries all fit in my radio without any problems.

That's about all the negatives I've found after having the radio for a while. It's a good value to me for AM/FM radio for $32.90 (including shipping).

Comments

[Paul]

You should be able to replace the ferrite rod with a longer one if there is space ...

How can Tecsun make such a basic mistake on the headphone jack?

[jeffrey McMahon]

Paul, thanks for reminded me about that subpar Toshiba. I deleted the post. Thanks again.

[Scooby214]

There looks to be plenty of space for a longer ferrite bar.

As far as the mistake on the headphone jack, it is the same way on the original S350. (I also used to have a cheapo vintage lookalike radio that was wired the same way.) It appears that they did it to allow for either stereo or mono headphones. Since the original S350 didn't send FM stereo to the headphone output, I guess this was their way of making it compatible for more users. I'm pretty good with a soldering iron, so I may try to tackle correcting it.

[Stetsiwawa]

I like the boxy, minimal, strictly functional design of the R308 - a clear compact tuning scale, with the rest of the cabinet devoted to the sizeable speaker; nice big tuning and volume knobs (how's the feel of these? reasonably smooth, not too stiff, etc?), pleasing integrated carry handle, handy rear stand, etc (all very plasticy no doubt).How about the actual sound of the R308 through the 4 inch speaker: full and rangy when compared to the likes of DE1103 etc? on a par with the S350? Thanks.

[Scooby214]

The knobs are reasonably smooth, though there certainly is no flywheel effect to the tuning. The actual sound of the R308 is just slightly less than that of the S350DL, probably due to not having separate bass and treble controls. It doess sound bigger than the small portable receivers I've used, like the Grundig YB400PE. It has a pleasant sound when listening in a large room. (I use mine in my classroom before and after school). The handle feels surprisingly sturdy, and the radio has a sturdy feel overall.

[Stetsiwawa]

My Tecsun R-308 arrived a few weeks ago. Speaker audio sounded a bit flat, I thought, so I changed it for this one:
http://www.radioparts.com.au/ProdView.aspx?popup=1&Category=SXBB6005&Product=38852301&ProdDesc=SPG2301+100MM+SQUARE+SPEAKER
from a Radio parts shop here in Oz. It's 8 ohms like original. Power rating is 10w vs 2w original; seems to be just as sensitive/efficient though - the low power radio amp distorts at highest volume anyway. Replacement was simple - plenty of room in the large cabinet to work in. A Phillips head screwdriver was required to remove speaker and a couple of circuit boards. The new 4 inch speaker has the same standard square shape and mounting holes as the original. So it was a simple matter to replace speaker and screws, then solder wire. The magnet on the the new speaker is, however considerably larger in diameter (and weight), so I had to neatly cut away a section of the battery compartment to refit the rear panel (cabinet is just deep enough to accept speaker depth). Batteries fit easily now. Otherwise, the whole operation was dead easy. And the result is a spectacular improvement in sound quality. The rolled cone surround and whizzer cone has greatly broadened the frequency range. Lovely warm and bright balanced sound, particularly on FM (AM is OK, but I wish the radio had a more comprehensive tone control). The sliding bass control is, as Scooby says, just a scratchy bass boost which only kicks in near the bottom. It is however, quite effective, and once I adjusted that to my liking, I've rarely had to change it again. Speakers this size usually require much more (mid) bass than treble boost anyway. This is a cheap (US $32 delivered from China) plasticy radio. The tuning knob fell off immediately - a bit of Blu Tak (Sticky Tak) solved that problem (I also used some Tak to line the circumference of the new speaker - Tak is a very effective dampening agent). Otherwise, it's solid enough. The tuning mechanism is just a little stodgy, but the volume knob is smooth and perfectly incremental.
Anyway, it's now a completely satisfying table radio. And It probably sounds as good as anything it's size (costing xxxx $ more).

[Carrie]

Stetsiwawa,

Thanks for the detailed comment. I'll post it tomorrow. Jeff on my wife's computer.

[Paul]

Stetsiwawa,

Can you comment on the AM, and especially FM performance, especially in comparison with other radios you may have?

Also did the tuning knob fell off as a result of you opening the radio up and putting it back together, or is construction quality really that bad that the knob just fell off when you started using the radio?

Thanks very much

Paul

[Stetsiwawa]

I second Scooby's comments: FM is definitely this radio's strength. It's sensitive alright. I can get most of my local FM stations quite clearly with the antenna entirely unextended. My little Tecsun PL-450 certainly can't do that trick. (By the way, I also swapped the 57mm speaker on the PL-450 with one from an old Panasonic RF-P50 - once again, a marked improvement, with a newly pronounced difference between high and low tone settings. It seems to me that nasty original speakers may be a major hidden cause of disappointment among radio buyers.) When the antenna is extended, things obviously improve greatly. Selectivity is good too: seems to have a marked lock in/lock out "fencing" effect (if that makes sense) between stations. I haven't noticed drift on either band. Sensitivity and selectivity on AM are fine for me too. DXers may think otherwise. The ferrite rod is a little shorter than 5" if I remember right (Scooby confirms this). AM somehow doesn't sound that great to me - a slight personal tonal preference - I wish the radio had proper bass and treble controls - that said, I've already grown accustomed to the AM sound. When I make these audio-related comments, keep in my mind that I've replaced the original speaker with a superior after-market one (which has certainly improved both AM and FM audio quality).
I can also confirm Scooby's observation that the tuning scale on the R-308 is more accurate on FM than AM.
The tuning knob fell off the moment I took the radio out of the box. The tuning and volume knobs are designed to pull off with a bit of force; so the fit simply wasn't tight enough. You can put that down to poor quality control.
Earlier this year I bought a Redsun RP2100 (sold here in Oz, with local guarantee, under the Digitech brand for a great value US$90) for my sister, so she could listen to Radio Australia from Hong Kong (Total failure - she lives in one of those 100 metre high metal cages, through which no radio wave on earth can penetrate). That was a fine sounding machine with a 5 inch speaker and bass and treble knobs. I wish I could compare the R-308 to it. The R-308 does me fine. It sounds great with the new speaker, and the compact size makes for easy room to room portability.

[Scooby214]

On my two R-308 radios, the knobs didn't fall off. Instead, they were pushed too far onto their shafts. This caused them to rub against the case. They were securely glued into place, but I was able to carefully pry them out to a proper placement.

I bet that they neglected to put the glue on your knob. Probably a result of poor quality control.

You just can't find radios that are built with the attention to detail that was put into the vintage sets.