DXing with an inexpensive portable radio

[cyberdad]

For a great radio at a bargain price, you can't beat the GE Superradio II I picked up at a Church rummage sale a year and a half ago for a dollar! ;D

I'm jealous. Have been looking for these.

I couldn't believe it myself. I'd also been looking for one. Funny thing is, my wife dragged me along to the sale with her. I'd have never gone, left to my own devices. I walked in and spotted the radio immediately....couldn't believe my eyes! So be patient...hopefully good things will come to those who wait!

 

[boombox]

RE: Superadios & DX:
The best DX I had with a Superadio was when I took my Superadio 1 with me to Eastern Washington a few years ago. I heard WJR (1710 miles) and WOR (2180 miles). I also heard some of the Midwestern blowtorches that night. All barefoot. Superadios will definitely pull in the stations.

 

[radioman148]

RE: Superadios & DX:
The best DX I had with a Superadio was when I took my Superadio 1 with me to Eastern Washington a few years ago. I heard WJR (1710 miles) and WOR (2180 miles). I also heard some of the Midwestern blowtorches that night. All barefoot. Superadios will definitely pull in the stations.

Hearing WOR in Eastern Washington is quite impressive IMO.

 

[cd637299]

I only wish that the GE Superadio came out 2 to 3 years earlier.

I was stationed near Anchorage, and when the nights are good for DX, you can hear almost 5000 mile distance over the Pacific.

All I had at that time (1978-80) was the Realistic "AM Only" portable with a 3/32" (I think) EXT ANT jack in the back, of which really I had little use. I also was unaware of Select-a-Tenna or similar antennas.

Actually my better radio was the Delco car radio in my '75 Chevy Nova.

I was able to bag JOKR TBS Tokyo 954 & KIKI 830 Honolulu on the Realistic, and as far inside the US as WWL 870 on the Delco. Those sure were cold nights....

cd

 

[boombox]

I only wish that the GE Superadio came out 2 to 3 years earlier.

I was stationed near Anchorage, and when the nights are good for DX, you can hear almost 5000 mile distance over the Pacific.

All I had at that time (1978-80) was the Realistic "AM Only" portable with a 3/32" (I think) EXT ANT jack in the back, of which really I had little use. I also was unaware of Select-a-Tenna or similar antennas.

Actually my better radio was the Delco car radio in my '75 Chevy Nova.

I was able to bag JOKR TBS Tokyo 954 & KIKI 830 Honolulu on the Realistic, and as far inside the US as WWL 870 on the Delco. Those sure were cold nights....

cd

WWL from Alaska -- now that's an impressive catch!!

You must have had the Realistic TRF. They were popular in the 70's. They're pretty good little radios. Not quite as hot as the Superadios, but still good performers. They sound a bit tinny through the speaker, but plug in a set of headphones and they have a full sound.

 

[rbrucecarter5]

I only wish that the GE Superadio came out 2 to 3 years earlier.

I was stationed near Anchorage, and when the nights are good for DX, you can hear almost 5000 mile distance over the Pacific.

All I had at that time (1978-80) was the Realistic "AM Only" portable with a 3/32" (I think) EXT ANT jack in the back, of which really I had little use. I also was unaware of Select-a-Tenna or similar antennas.

Actually my better radio was the Delco car radio in my '75 Chevy Nova.

I was able to bag JOKR TBS Tokyo 954 & KIKI 830 Honolulu on the Realistic, and as far inside the US as WWL 870 on the Delco. Those sure were cold nights....

cd

 

[Steve Green NEPA]

@ Sam re daytime DX :
An old neighborhood axiom went, as long as you can catch a football, it's still daytime. A few moments later, the same pass hits you right between the eyes, well, then it's nighttime.
Those same grey areas in early mornings and late afternoons affect all AM DX regions, of course.
So what is defined as 'daytime DX' ? When does it begin, what's it's peak, and when does it end? On a guesstimate I'd say the peak 'normal' would be the exact midday in late June.
But you can get some wicked broad-daylight DX via the Mid-Winter Anomaly -- nighttime skip from certain regions with the sun still high. But those conditions cannot be considered average, by a long shot.

Re specifics of what, say, a GEII can receive :
Perhaps what it doesn't receive might be of some use. I was on a paint job at an empty house in south St. Clair PA once. A mile away is the tower of WPAM 1450.
On a break at the kitchen table, the radio and I managed an incredible null on WPAM. The result was two logged stations on 1440 plus two on 1460.
And here at my own place (maybe 12 miles NE of the paint kitchen) the GE SRII did such a wonderful null on the other local, WPPA Pottsville, that the lights in WPPA's studios must have dimmed. It was about 1PM here, springtime, and I heard Spanish behind them. The null wasn't a 90°, so the two stations couldn't be separated. But the null on WPPA was the main thing.

On your last question:
Both the GE SRII and the new Grundig S450 work very fine with the batteries as a tabletop radio, day and night. I'm quite satisfied with both of them. I've not used an external antenna on either of them, for the most part.
Sometimes I used to put the GE SRII just under the bottom row of wires of the loop at an oblique angle and get some awesome, beam-type uni-direction reception lobes.
Basically, though, I want a barefoot portable I can bring along to various jobs and listen to a ball game on a roof ..... or in some yard I'm I'm raking or repairing a fence ..... or hear KYW's weather while I paint ..... or as a neat, home table radio.

 

[rbrucecarter5]

I only wish that the GE Superadio came out 2 to 3 years earlier.

I was stationed near Anchorage, and when the nights are good for DX, you can hear almost 5000 mile distance over the Pacific.

All I had at that time (1978-80) was the Realistic "AM Only" portable with a 3/32" (I think) EXT ANT jack in the back, of which really I had little use. I also was unaware of Select-a-Tenna or similar antennas.

Actually my better radio was the Delco car radio in my '75 Chevy Nova.

I was able to bag JOKR TBS Tokyo 954 & KIKI 830 Honolulu on the Realistic, and as far inside the US as WWL 870 on the Delco. Those sure were cold nights....

cd

OK - I don't know what happened with the other post - here is the correct post:

You might enjoy this:

http://earmark.net/gesr/12-655.htm

I did heavy modifications to the little portable - I socketed the ferrite antenna connections so I could try various combinations of larger ferrite bars and more / less turns on the sense winding. Long ago, I got rid of the little earphone jack for the external antenna connection, and put in a coax connector - much better, but also sticks out in back of the radio.

I finally got a 200mm ferrite bar to fit in the radio, and put in a +/- 6 kHz three element stagger tuned ceramic filter to help the selectivity. It still isn't great, but it works.

The FET in the front end is a good one - this is the one time Radio Shack got serious about making a DX portable. Too bad the internal design didn't allow a better speaker - the PC board is large and intrusive. I can tap off the volume control to get a good line out signal for my stereo. This is definitely a great little radio. I'd fault it on selectivity as it comes out of the box, even with the Murata ceramic filter added it still has problems. Still, this is the radio that I used to get KILT 610 Houston in Lubbock, TX during the day, and null KCRS Midland to get KTSA San Antonio during the day in Lubbock. That was when both were McLendon stations, top-40, and worth listening to. As for side-by-side comparisons with GE Superadios - the Radio Shack has an edge on sensitivity on some stations with the 200mm ferrite bar, the GE has an edge on sensitivity on other stations. The GE wins hands down on selectivity. Radio Shack started with a four stage IF in the 12-675:

http://earmark.net/gesr/12-675_tech.htm

But they started skimping on selectivity with only two IF cans in the 12-655. But it did have a ceramic filter, unfortunately it doesn't seem that effective. Mine had a ceramic filter that obviously quit, and I ended up ordering replacement parts. I found out really quick that if you exposed the ceramic element to light, it would be destroyed. So my second installation I didn't separate the metal case from the plastic internals.

They continued skimping on the number of AM IF's in their AM-FM DX portable:

http://earmark.net/gesr/12-650.htm

The AM section used a lot of ideas from the 12-655, but substituted a bipolar transistor instead of the FET.

Radio Shack came out with their cost reduced version of the Superadio:

http://earmark.net/gesr/12-603.htm

Performance out of the box was never as good as the GE, primarily due to a shorter ferrite bar and only two IF cans again. But - a contributer to the Yahoo Superadio group has suggested some modifications that have the potential to bring it on par with a GE Superadio. I will shortly be trying them to see - a longer ferrite bar does fit and does bring sensitivity up to the level of a GE, but there is a funny AGC curve that hobbles the sensitivity and selectivity near strong local stations. I'm looking for a fix for that problem as well.

Radio Shack has attempted other DX portables, but I don't own them. I would say that the basic 12-675, even with germanium transistors and no ceramic filters - by virtue of its 4 IF cans - is on a par with the 12-655 as far as DX is concerned. Both are well worth the money if you can pick them up on eBay, especially if you know enough to get inside and make some modifications.

If you are looking for FM - don't even think of a 12-650 unless you know how to add the narrow ceramic filter. Out of the box it has the extremely aggressive AFC that holds a station way beyond reason as you tune - you never want to leave it enabled unless you can't tune a radio very well. Switched off, out of the box selectivity becomes reasonable for a cheap IF strip - the narrow filter makes all the difference in the world. If you are 50 to 100 miles out from the station you want, you almost have to do the narrow filter. Do that, and it will work. 12-603 FM - good - on a par with GE, just don't expect deep fringe DX from any of these portables. I can do rim shots out to 100 miles or so, not much more.

 

[boombox]

Mr. Carter, have you ever tried out the Realistic TRF 12-656? It looks nearly identical to the 655, with a few modifications to the circuit (AF chip, tone switch instead of fader, 3 IF cans).

Aside from the AF chip (which seems to have a bit mellower AGC than the 655) the biggest difference is that they took out the ceramic filter and added an extra IF can in its place.

The 656 has sharper selectivity (at least my 656 does), but the 655 seems to have a bit wider selectivity with narrower 'skirts', if that makes any sense. Rating the two against each other is a toss up. Fun little radios, though.

 

[rbrucecarter5]

Mr. Carter, have you ever tried out the Realistic TRF 12-656? It looks nearly identical to the 655, with a few modifications to the circuit (AF chip, tone switch instead of fader, 3 IF cans).

Aside from the AF chip (which seems to have a bit mellower AGC than the 655) the biggest difference is that they took out the ceramic filter and added an extra IF can in its place.

The 656 has sharper selectivity (at least my 656 does), but the 655 seems to have a bit wider selectivity with narrower 'skirts', if that makes any sense. Rating the two against each other is a toss up. Fun little radios, though.

I don't have a 12-656, but the derivation of the design makes sense - especially with the finicky ceramic filter that I suspect went out again in mine long ago --- hence the external one. Everything you say makes sense for a 12-655 vs. a three IF can version. Deeper skirts with a ceramic filter, but better selectivity with three cans. I have some old Radio Shack table radios with only two cans - and they have poor selectivity and birdies all over the band - prime candidates for ceramic filters.

 

[stacker]

I have a later version of the Superadio (one of those sold with an RCA badge on the front). Great radio, but the varactor tuning makes it hard to tune due to the tension from the dial string.

My favorite portable continues to be the Sony ICF-2010.

 

[cd637299]

Bruce, yes that's the baby....I sure am not handy with mods like that, so I wouldn't have a clue on how to modify one. IIRC in late 1978, Anchorage had only one dealer that sold that thing, and I am not sure if it was even officially called Radio Shack---but I was able to purchase one.

A Superadio II up there would sure have made the hobby more fun.

As to the Superadio III, it does seem true that the thing has a hard time staying on frequency.

cd

 

[rbrucecarter5]

I have a later version of the Superadio (one of those sold with an RCA badge on the front). Great radio, but the varactor tuning makes it hard to tune due to the tension from the dial string.

For you and cd637299:

Its not the dial string or the varactors. When dozens of people started reporting this on technical forums - got out the test equipment, borrowed a defective unit, and diagnosed the tuning problem. It is the pot:

http://earmark.net/gesr/sr3_instability.htm

Another test I did but didn't mention was to supply the tuning voltage directly from a lab supply. Absolutely stable again.

It is a real pain in the posterior to change out the tuning pot, because you have to disassemble the radio down to the bare board:

http://earmark.net/gesr/SR3_disassembly.htm

After a lot of experience, I got to where I can change one out in about 45 minutes.

I charge fellow DX'ers a nominal fee for doing it - but with postage it still costs as much to stabilize the tuning on one as it does to buy the radio in the first place. Cost reduction - the Chinese way. Only this time it rendered the GE Superadio 3 virtually unusable, and probably doomed the product. Just changing one pot.

By the way - 300k is also the value of pot used in some electric guitars, and I've had suggestions to try one of those. Its been a long time since somebody sent me a radio for repair, so I never tried the electric guitar store source.

 

[boombox]

Mr. Carter, I have a SR3 (1993 model) with a questionable varactor tuner, the radio drifts while warming up. Consequently, I don't use it much. I'll probably have to put in a new pot.

I also have a 1995 SR3 that works fine -- the tuning is reasonably stable, just a little bit of backlash (which I can live with), but I can zero in on stations o.k., and it doesn't seem to drift. Now I wonder if the pot in my good SR3 will wear out or go funky on me.

Is there a way to treat the good one so the potentiometer will last? Would Deoxit or some similar lube extend the life of the good one?

 

[rbrucecarter5]

Mr. Carter, I have a SR3 (1993 model) with a questionable varactor tuner, the radio drifts while warming up. Consequently, I don't use it much. I'll probably have to put in a new pot.

I also have a 1995 SR3 that works fine -- the tuning is reasonably stable, just a little bit of backlash (which I can live with), but I can zero in on stations o.k., and it doesn't seem to drift. Now I wonder if the pot in my good SR3 will wear out or go funky on me.

Is there a way to treat the good one so the potentiometer will last? Would Deoxit or some similar lube extend the life of the good one?

The pot is either a good one - with a "ball" making contact with the element, or it is bad. Even an SR-3 with a good pot can drift slightly at the high end of the bad, but if you have a defective tuning pot, you will really know. I have long suspected that the culprit is not the contacting element itself, but too loose of a tolerance in the shaft / bushing of the pot. Not much you can do to correct it, but I did notice quite a few SR-3's where there was a pad of some sort on the top of the pot - maybe they got some improvement if there was vertical pressure on the pot.

I never recommend de-oxit in pots - I recommend just the opposite. When I carefully disassemble and clean them, I clean the metal contacts with a pink eraser, the carbon with a paper towel. I then coat all mating surfaces with a very thin coating of silicon bearing grease - and never have another problem with them. But since the problem with the tuning pot appears to be mechanical tolerance, no amount of cleaning will help. Replacement is the only strategy.

There are hobbyists who put a digital readout on the radio, and tune with a twenty turn precision pot - they get complete stability. Some users even bypass the scale all the way, and just tune by memory, or intimate knowledge of the local band. If you get rid of the range pots, you can tune a wider range into very low shortwave frequencies and upper longwave frequencies.

 

[dx23]

I have a eton g8 world traveler that works quite well. it was at the time about $50 from Radioshack, now they are asking $60 for it. It is a good little radio for an inexpensive radio to DX on. I have thought of adding an external antenna jack for when Im at home I can connect to my rooftop antenna. it works well with out it, but my house has all kinds of interference in it.

 

[stacker]

Its not the dial string or the varactors. When dozens of people started reporting this on technical forums - got out the test equipment, borrowed a defective unit, and diagnosed the tuning problem. It is the pot:

Thanks RBC. Makes perfect sense.

 

[Icangelp]

I know one receiver not to buy...the Grundig S350. It is a table top portable AM/FM/SW receiver that looked good in the picture.

A couple of weeks ago, Amazon had one on their Gold Box deals page. I bought one. It arrived. I tried using it.

The appeal for me is that it has an "old style" tuning knob combined with digital readout. The inner dial is fine tune, and the outer dial is speed tune.

Unfortunately, it is next to impossible to get either dial to stop at the desired frequency. I tried to get it right for almost an hour. No luck.

Back it went.

 

[FreddyE1977]

Along the lines of this topic...

The inexpensive Tecsun portable I was so impressed with is now suffering from the same
fatal malady that eventually claims most inexpensive radios (the cheap as hell little potentiometer
they use as an on/off volume switch is crapping out. Can no longer control volume and radio
frequently blanks out or goes to static).

Aside from this the thing is in near-mint condition. Any point at all in exploring getting this fixed?
I am sure if it's possible at all it will cost me much more than the list price of the radio.

 

[cyberdad]

I'd also have to suggest avoiding the Eaton E-10. I bought one about 10-12 years ago, thinking it would be a suitable replacement for a Grundig Yacht Boy 400PE, which was a great radio. The Eaton had many of the same features, and was also similar in size as well as the price point. On top of being offered by the company that had taken over the Grundig radio business.

It wasn't a bad radio by any means, but performance....which was never quite up to the Yacht Boy....quickly degraded. Particularly the volume control pot and the headphone jack. It also seems to have lost some of its sensitivity (although the selectivity is still reasonably good). On balance, I've been somewhat disappointed. Especially when comparing it to the Yacht Boy.

At the moment, it's the only radio I have with fully operational SW, so I use it for that (despite the lack of a BFO function). There's a tunable antenna trimmer that I've always thought was rather pointless, although it does work. Bottom line is that this radio is reasonably good on FM, moderately adequate for shortwave, and mediocre for AM. That is....once you get past the volume control and headphone jack issues.