Herculodge

Russ Explains How to Connect a Dipole FM Antenna to Your Sangean U3

I plan on doing this to modify my favorite radio, the Sangean U3, as soon as my twin newborns give me time to run down to RadioShack:

Unscrew the antenna from the Sangean U3 and find a small machine screw that will thread into that hole where the antenna goes. If you don't have any small bolts or screws handy, you can match the threads up by taking the antenna with you to a hardware store. Then find a nut that screws onto the antenna's threads. Now that you know what the threads are (I suspect it will be something like an 8-32), you can buy a corresponding screw. You only need one that's 1/4 inch long or the same length as the stud on the end of the antenna.

When you have the correct screw, use it to fasten one lead of an FM dipole antenna to the U3. Then you can play around with finding a good position for the dipole antenna to pick up all your stations. It should pick up stations better than the original U3 rubber antenna. This will also work with a cheap set of rabbit ears which is what I just tried. Just remember to only attach one of the 2 leads, not both.

Russ Takes a Look Inside the Sangean U3 and Sangean LB-100 Lunchbox Radios

 

I took a quick look inside the Sangean U3 and the LB100 Lunchbox mainly to answer the question about the AM antennas. I discovered some interesting things about how these radios are engineered and built. Both radios are well designed and use high quality components. While not up to the standards of the old Panasonic radios for build quality, it's probably safe to say that this is about as good as it gets for today's radios. Both radios seem to be designed to be worked on and repaired. The large number of connectors allow easy dis-assembly and access to circuit boards.  

 
I've included an inside view of the U3's large speaker and the single coil AM antenna which measures about 5 inches long. The speaker is 8 ohms and is rated at 15 Watts, which is twice the rated 7 Watt output. It appears to be a high quality speaker. I want to do a more complete dis-assembly of the U3 later on and see what ICs it uses so they can be compared to what the Lunchbox has.

 

The LB100 also has a high quality speaker. I couldn't tell the ratings since they covered the magnet with foam. One half of the radio has the display and related control circuitry on one circuit board. The other board appears to be the power and audio output board. It also has the AM/FM radio circuitry and the 3 inch AM antenna mounted on it. Note the massive heatsink on the TDA7266L 5 Watt Mono Bridge Amplifier IC. The other IC is a UTC 4580 Dual Op Amp for the tone control. The unmarked IC on the reverse side of this board is probably the combined AM/FM function chip which is probably a proprietary Sangean-designed circuit.

 

The AM performance of the Lunchbox is not as good as the U3 mainly because of its smaller ferrite bar antenna. The FM performance is almost as good as the U3 because they both have very similar designs and probably use the same antenna and ICs. I'll try to confirm that when I take the U3 apart completely. I hope this answers at least some of the questions a lot of you have had about these two radios. More to come later.

Update:

There's a glaring error in the article I wanted to correct. (I blame being in a hurry, having a senior moment, my cat ate the schematic, etc.) I stated that the dual op-amp chip was for the tone control. The LB100 obviously has no tone control. It does need at least one stage of amplification before the output transistor so my guess is that's what it's for. The spec sheet for the chip says that's what they are commonly used for and I just ran with that. I like to be as accurate as I can, so if anybody sees any other errors like this, please call me on it.

 
 

Readers Set the Record Straight: The Redsun RP-3100 Is Vaporware . . . Kind Of

Paul and others have made it clear that the Redsun RP-3100 link is old and that except a few production models, the radio does not exist for sale. 

If you can find one. It's very rare. Its specs are as follows:

FEATURES: PLL SYNTHESIZED WORLD BAND RECEIVER PLL MW/FM/LW/SW1/SW2*SW3 SYNTHESIZED WORLD BAND RECEIVER FRE.RANGE: FM 87.5-108MHZ/MW 522-1620KHZ (9K STEP) 520-1710KHZ(10K STEP)/SW (1711-29999KHZ) DUAL CONVERSION FOR AM BATTERY CHARGING FUNCTION FINING KNOB&QUICK TUNING UTC/LOCAL &DUAL ALARM TIME BATTERY AND SIGNAL STRENGTH INDICATOR ALARM TO RADIO OR HWS BUZZER ADJUSTABLE SLEEP TIMER KEY LOCK & KEY BEEP LARGE LCD DISPLAY WITH GREEN BACKLIGHT AC 220~240V/50HZ & DC(6-9V) /BATTERY OPERATION JACK AM RF GAIN TREBLE/BASS ADJUSTABLE WIDE/NARROW SELECTOR SLOW/FAST/STOP TUNING 3.5MM EARPHONE;FM STEREO/MONO SELECTOR LINE OUT L/R SNOOZE &BACKLIGHT ON/OFF DX/LOCAL FOR AM RECEPT INT.&EXT. ANTENNA SELECTOR TELECSCOPIC AERIAL. 1000 MEMORIES LW 159-520KHZ; SSB FUNCTION 10 NUMERIC FREQUENCY KEYPAD ENTRY ATS FUNCTION MEMORY SCAN & DELET FUNCTION TIME COUNTDOWN FUNCTION.  SPECIFICATIONS: L290 X W185 X H70MM

Choppy Translation Info About the New Anjan DTS-10 Radio

Thanks to Andreas for THIS TRANSLATION for the new Anjan DTS-10 Radio. 

Ed from Canada Shares His Info and Photos of the Panasonic RF-7270 Royal Aire Radio Recorder

 

Addressing Dan's restoration of his Panasonic RF-7270 Royal Aire Radio Cassette Recorder, Ed M from Canada writes:

I too have 3 of these RF-7270 radios around all in good working condition. 2 of them which I purchased off of ebay some years ago and one that my dad purchased new in 1969- 1970 for almost $200.00 at Eatons. 

 

From what my dad told me many years ago is that the RF-7270 is a Phillips/Norelco cassette tape recorder adapted with an fm am radio and this RF-7270 unit was first available in late 1968 which would put it at 42+ years.Really you could say that this radio is the inception of the first real ghetto blaster.It came with a microphone and stand, ear phone and 5 blue Panasonic Hi top batteries and instruction book, warranty card and a demo cassette tape which i still have. 

 

This was standard with Panasonic during those days to include batteries, a cassette tape, microphone and earphone. For my dads unit he had also purchased which was an option at the time a multi voltage AC adapter from Panasonic as so the unit could be powered from 120 volts ac outlet to 7.5 dc volts in the house instead of using the batteries.

 

I recall that this radio was a pig on batteries when using the cassette deck with the volume turned up and the tape speed would change as the batteries went weak.Also available was a car mounting bracket in which you could use the radio in the car and then remove it from the car and use it as a portable. When you would use the radio in the car the round fm/am station numbers would light up blue in color when you turned the radio on in which you could see the station dial in the dark. This also being possibility the first car stereo radio even though this is a mono unit it has superb sound and tone quality and sensitivity.

  

I will also mention that the Panasonic RF-3100 cassette player recorder uses the same cassette design as the RF-7270 and the RF-3100 was made in 1967 a year earlier which was Panasonic first small potable cassette player recorder in 1967.

 

Also in my collection I have an RF-7280 circa 1969 which is the same as the RF-7270 except it has a weather band for listing to weather reports also instead of the one control knob for the cassette player as in the RF-7270 the RF-7280 incorporates the piano key type of operation for the cassette deck also along with this I have 2 RF-7490 stereo cassette radio recorders which are in working order all units use the 4`x6`powerful speaker.I also have service manuals for all 3 models RF-7270,Rf-7280 and the RF-7490.

Also as you mention there is a large, printed copy of the RF-7270's schematic -- carefully folded and tucked between the chassis and the case which is true as is the same for my units.The speaker is a powerful 4`x6`oval speaker
All of these units at the time were top notch in there class and were built very well to be enjoyed in the many years to come.

Best Regards,

Ed M.

"A Boat Load of Changes": Sangean Updgrading the ATS-909 with the 909X for 2010

(Re-post)

Tom writes: "I called Sangean yesterday and they indicated a major upgrade of the ATS-909, called the 909X, is coming in 2010." (Thanks, Matt and Leonardo, for the photo links)

More Photos of the Anjan DTS-10

Thanks, Paul, for providing THIS LINK to more photos of the Anjan DTS-10. 

Real Or Vaporware? The Redsun RP-3100 Table Top Radio Surfaces Again

Neil has apprises us of this Redsun RP-3100 link, but I don't know if the link is old, chicanery, or very real. I hope it's the latter. 

The alleged specs are as follows:

FEATURES: PLL SYNTHESIZED WORLD BAND RECEIVER PLL MW/FM/LW/SW1/SW2*SW3 SYNTHESIZED WORLD BAND RECEIVER FRE.RANGE: FM 87.5-108MHZ/MW 522-1620KHZ (9K STEP) 520-1710KHZ(10K STEP)/SW (1711-29999KHZ) DUAL CONVERSION FOR AM BATTERY CHARGING FUNCTION FINING KNOB&QUICK TUNING UTC/LOCAL &DUAL ALARM TIME BATTERY AND SIGNAL STRENGTH INDICATOR ALARM TO RADIO OR HWS BUZZER ADJUSTABLE SLEEP TIMER KEY LOCK & KEY BEEP LARGE LCD DISPLAY WITH GREEN BACKLIGHT AC 220~240V/50HZ & DC(6-9V) /BATTERY OPERATION JACK AM RF GAIN TREBLE/BASS ADJUSTABLE WIDE/NARROW SELECTOR SLOW/FAST/STOP TUNING 3.5MM EARPHONE;FM STEREO/MONO SELECTOR LINE OUT L/R SNOOZE &BACKLIGHT ON/OFF DX/LOCAL FOR AM RECEPT INT.&EXT. ANTENNA SELECTOR TELECSCOPIC AERIAL. 1000 MEMORIES LW 159-520KHZ; SSB FUNCTION 10 NUMERIC FREQUENCY KEYPAD ENTRY ATS FUNCTION MEMORY SCAN & DELET FUNCTION TIME COUNTDOWN FUNCTION.  SPECIFICATIONS: L290 X W185 X H70MM

Herculodge Compares the Panasonic RF-888 with the RF-1108 (With Updates)

(Re-post)

I purchased a Panasonic RF-888 (the black, more stout radio on the right above; the 1108 is the taller gray model), a model from the early 1970s, a few months ago and it's a very good radio, huge speaker, silent background on AM, strong FM. Its tuning meter is operational, but being ontop and small it's hard to see. There's no static while tuning or changing volume. Update: The RF-888 is my official AM radio in my workout room. My esteem for this radio has continued to grow after a year. 

Enter now a newer vintage, what appears to be a rare model from the early 1980s, the Panasonic RF-1108 Big Sound AM/FM/PSB radio. A side by side comparison for AM and FM proved to be virtually identical. Perhaps on AM I'd give a slight nod to the RF-888, but I feel I'm splitting hairs here. Speaker sound is virtually the same as both radios look like "Big Mouths." Update: A year later, my 1108 fluctuates on volume. Without warning, the volume will increase, then decrease, than increase again. It's now in storage. 

I shouldn't be surprised that the 1108 has problems. I had a cheap build quality, nothing like the tank that is my beloved RF-888. The 1108 seems to be made of lesser, hollow plastic materials. But I won the bid for $54 plus $9 shipping. In contrast, the RF-888 cost me $220. I see the RF-888s bidding for half that much, but mine is mint. 

I like the tuning meter on the 1108. It's in the front and big enough to see without squinting my eyes. 

While both radios are top performers, I hate to say that the tuning meter is way too close to the red zone, struggling around the 3 or 4 mark with the strongest being 10, while fine tuning 103.1, the weakest FM station I regularly listen to. 

Now here's the biggest revelation I received from today's comparison test. After being disappointed with the way both radios received the weak 103.1, I decided to try my Sony ICF-5900. I placed the 5900 on the kitchen table right where I had tested both the 888 and the 1108. Friends, listen carefully: The Sony ICF-5900 BURIED THE NEEDLE INTO THE 10, RECEIVING 103.1 WITH FULL POWER. So let's be clear: If you're going to spend around $200 on a vintage, you might want to get the 5900 over the 888. 

I wasn't done with 103.1 yet. I put the 5900's smaller cousin, my ICF-5500, on the kitchen table, tuned to 103.1 and needle buried itself until it landed securely on the 9. Slightly less than the 5900, but I paid $80 for it. 

Having done this comparison, I have a new esteem for my Sony models. But I wasn't ready to give up on my Panasonics. I took out my RF-1130, tuned to 103.1 and the needle hit the 9.5 mark, better than the 5500 but not as good as the 5900.

One more radio to go: My Panasonic RF-870, the one I bought for $80 with a broken antenna tip. I tuned to 103.1 and buried the needle on 10.  That 870 didn't even need its full antenna!

Based on these tests, I'll probably sell the comparatively weak performers. What started out as a 2-radio comparison, ended as an FM vintage test. Yes, as a radiophile, I am a tyrant with my radios: Perform like a champion or be gone with you. 

Photos of the Anjan DTS-10 Digital Table Top Radio

Thank you, Paul, for providing THIS RADIO BLOG LINK containing photos of the Anjan DTS-10. Is this the answer to the never-produced Redsun RP-3100 or an inferior copy?