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rbrucecarter5
Guest
My experiment to find out which "Superadio" is really the best. Surprising result. Sorry the audio is so poor -
https://youtu.be/8o4JivGyFnA
https://youtu.be/8o4JivGyFnA
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Fwiw-feedback,
Two DXer pals from school got me a GE Superadio II for my 45th birthday.
Swell, swell radio. Nestled in the X crook of the loop, I got some interesting nulls.
And of course, it sounded terrific. I could get X-Band stuff on my Lafayette HA-600, so I didn't miss that feature. The '2' only went up 1640, but no big worry.
Several years later, I saw a III on sale for like $48. Despite having read some discouraging reviews, I had the money and I bought it. Supposedly, 3 in 1000 of them worked, well, worked super. How bad could it be?
It was bad. I must've gotten one of the 997.
Even with me tuning with the narrow bandwidth setting, the stations smeared onto the adjacent frequencies (the span of the dial from around 850 to 960 was a particular disgrace).
The FM dial seemed to work pretty well. But I get these things for the AM section.
A few years later I saw a good-condition GE SRII in a local thrift store, behind the counter. It was tuned to WKSZ 102.7 in Williamsport. I suggested to the girl that I have a newer GE Superadio model at home .... it gets great FM .... that I can 'use this '2' for parts for the old one I have home' .... and that I'd give her the new model plus $10 for the one that was playing.
She said, 'Sure'. So we swapped. She got a new, sleeker FM radio; got $10 for a 'relic' -- and I got rid of that useless thing that couldn't tune properly on AM * plus * a backup 2.
Never heard (or even seen) a '1'. I've seen pictures of one, but never saw one in person.
Nice post, Carter! Thx !
Two DXer pals from school got me a GE Superadio II for my 45th birthday.
Swell, swell radio. Nestled in the X crook of the loop, I got some interesting nulls.
And of course, it sounded terrific. I could get X-Band stuff on my Lafayette HA-600, so I didn't miss that feature. The '2' only went up 1640, but no big worry.
Several years later, I saw a III on sale for like $48. Despite having read some discouraging reviews, I had the money and I bought it. Supposedly, 3 in 1000 of them worked, well, worked super. How bad could it be?
It was bad. I must've gotten one of the 997.
Even with me tuning with the narrow bandwidth setting, the stations smeared onto the adjacent frequencies (the span of the dial from around 850 to 960 was a particular disgrace).
The FM dial seemed to work pretty well. But I get these things for the AM section.
A few years later I saw a good-condition GE SRII in a local thrift store, behind the counter. It was tuned to WKSZ 102.7 in Williamsport. I suggested to the girl that I have a newer GE Superadio model at home .... it gets great FM .... that I can 'use this '2' for parts for the old one I have home' .... and that I'd give her the new model plus $10 for the one that was playing.
She said, 'Sure'. So we swapped. She got a new, sleeker FM radio; got $10 for a 'relic' -- and I got rid of that useless thing that couldn't tune properly on AM * plus * a backup 2.
Never heard (or even seen) a '1'. I've seen pictures of one, but never saw one in person.
Nice post, Carter! Thx !
R
rbrucecarter5
Guest
Yeah - the GE Superadio III is the definitive textbook case of cost-cutting sinking a product. The moment they went to that cheap tuning pot, the product was doomed. Sure, I can fix them, but I have to strip it down to the PC board, remove the old pot, install the new one, add resistors to trim it down to 300k, then re-align the whole thing. And the dial calibration is awful afterwards. I think if GE did it on an assembly line, it would still take 30 to 45 minutes to re-habilitate the radio, which is WAY too cost prohibitive to justify. Somewhere, in a warehouse is - or was - all of the returns and unsold radios. Probably shredded for scrap to recover precious metal.
Whenever I find a defective III at a bargain price - I buy it to re-habilitate it for myself or a friend. Properly repaired, they are darn good radios. But the selectivity is not as good as a "II". I am wondering, though, is that because of the extreme sensitivity, or is it inherent to the design. I may run some tests on a bare board to get to the bottom "III"'s selectivity issue and see if there is a fix.
Whenever I find a defective III at a bargain price - I buy it to re-habilitate it for myself or a friend. Properly repaired, they are darn good radios. But the selectivity is not as good as a "II". I am wondering, though, is that because of the extreme sensitivity, or is it inherent to the design. I may run some tests on a bare board to get to the bottom "III"'s selectivity issue and see if there is a fix.
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rbrucecarter5
Guest
A bit of detective work based on this tech page: https://interrocknation.blogspot.com/2015/10/fixing-sangean-pr-d5s-low-headphone.html
leads me to believe the PR-D5 lacks a tuned RF stage on AM. Turning up the volume on weak stations is a dead giveaway that there is not a lot of RF gain up front.
A radio that lacks a tuned RF stage can still be a good performer - I put a 200 mm ferrite bar in my daughter's 15 year old "Mary Kate and Ashley" radio - and - WOW! That thing is hot. Not quite up to Superadio standards, but the twins hired a good company to design the radio they branded. A very respectable performer, but - it acts exactly as described in the PR-D5 page. I would not be a bit surprised if it used the exact same "radio on a chip" that the MKA radio used. It is an LA1824: http://earmark.net/gesr/super.htm (second radio). If you will notice, the other radios used a 200mm ferrite bar antenna, and they are also good peformers. What is lacking, though, is that last bit of noise floor elimination which comes from actually amplifying the RF prior to mixing. Mixing is a noisy process, and a high performance radio really needs to boost the incoming weak signals before they are subjected to mixing. The other thing the tuned RF stage does is give some immunity to images on the AM band. By having an active bandpass filter out there to boost the signal you are interested in, you also reject others you are not interested in. This will be more apparent in urban areas with lots of stations.
Superadio III is one of the five most disappointing purchases I've made in my lifetime
(and I'm over 50). Very poor AM selectivity and signal rejection. I packed it up 48 hours
later and got my refund.
Still kicking myself for not buying a Superadio II at the Hills Department Stores Going Out Of Business Sale.
They had been marked down to twenty-eight bucks.
(and I'm over 50). Very poor AM selectivity and signal rejection. I packed it up 48 hours
later and got my refund.
Still kicking myself for not buying a Superadio II at the Hills Department Stores Going Out Of Business Sale.
They had been marked down to twenty-eight bucks.
That was a very inclusive review,
I think the audio levels might have been more consistent if the reviewer had used the headphone jacks.
We never encounter reviews which include my favorite series of rigs because they are so far-removed from the hobbyist price range.
The Potomac Instruments FIM-XX series definitely qualifies as "SuperPerformers", none the less.
An added benefit is that the listener can give very accurate, objective signal reports on all stations received,
and good, functioning used ones can occasionally be found at garage sales and flea markets for well under the cost of small used cars.
Does anyone have any experience with or thoughts about these highly polished industrial diamonds?
I think the audio levels might have been more consistent if the reviewer had used the headphone jacks.
We never encounter reviews which include my favorite series of rigs because they are so far-removed from the hobbyist price range.
The Potomac Instruments FIM-XX series definitely qualifies as "SuperPerformers", none the less.
An added benefit is that the listener can give very accurate, objective signal reports on all stations received,
and good, functioning used ones can occasionally be found at garage sales and flea markets for well under the cost of small used cars.
Does anyone have any experience with or thoughts about these highly polished industrial diamonds?
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I have lugged around various models of Potomac FIM field strength meters, on countless AM directional proofing campaigns and "monitor point" checks. Just used one the other day in fact.
They are really, really good receivers. They have to be, as their intended purpose is precise measurement of AM broadcast field strength levels, close by and far away from the AM broadcast antenna. They can also be used to check harmonics (one model has coverage up to 5 MHz as well as the standard broadcast band).
I have forgotten details about the circuit design and specific components in the FIM series. Somewhere at work I have manuals with that info. I know they have a tuned front end that works very well. You will not hear images on an FIM, unless they are actual harmonics coming from the transmitter. The tuning knob has a mechanical two-speed action that I find quite pleasing.
I don't believe these instruments are manufactured by Potomac anymore, as some of the components and assemblies are no longer available. They now offer a digital FIM that retails for somewhere around $15K. It is becoming difficult to repair the analog units. The signal strength meter in particular cannot be replaced by the factory any longer. In fact, if you happen to find one of these at a hamfest or flea market, most likely the meter or calibration circuit will be inoperative, which makes it useless for field strength measurements. But if the radio part still works, it would be a fun receiver to play with.
They are really, really good receivers. They have to be, as their intended purpose is precise measurement of AM broadcast field strength levels, close by and far away from the AM broadcast antenna. They can also be used to check harmonics (one model has coverage up to 5 MHz as well as the standard broadcast band).
I have forgotten details about the circuit design and specific components in the FIM series. Somewhere at work I have manuals with that info. I know they have a tuned front end that works very well. You will not hear images on an FIM, unless they are actual harmonics coming from the transmitter. The tuning knob has a mechanical two-speed action that I find quite pleasing.
I don't believe these instruments are manufactured by Potomac anymore, as some of the components and assemblies are no longer available. They now offer a digital FIM that retails for somewhere around $15K. It is becoming difficult to repair the analog units. The signal strength meter in particular cannot be replaced by the factory any longer. In fact, if you happen to find one of these at a hamfest or flea market, most likely the meter or calibration circuit will be inoperative, which makes it useless for field strength measurements. But if the radio part still works, it would be a fun receiver to play with.
Of course, new models would also have to cover up to (1.7x3) 5.1 MHz.
That would also give them full coverage of all three tropical bands.
You know you might be a nerd if...
You drive by an AM transmitter site and tune to their second harmonic.
I am absolutely fully, totally guilty if the station is below 860.
That would also give them full coverage of all three tropical bands.
You know you might be a nerd if...
You drive by an AM transmitter site and tune to their second harmonic.
I am absolutely fully, totally guilty if the station is below 860.
I have a GE SuperRadio II. Great Radio. IBOC and switching power supplies in nearly everything have taken much of the fun out of DXing, along with FM Band overcrowding, though. I bought a GE SR III as a gift for a family member. It works well, but is not nearly as good as the GE SR II.
A CE at a neighboring market cluster offered me an old AM FI meter with a spring tension linearity problem with the d'Arsonval meter movement. He unfortunately left the cluster before I could get there to pick it up. AM FI meters typically receive and measure down to 10 microvolts per meter. Makes it difficult to do upgrade applications with measured conductivity radials on Class I-A/I-B/A frequencies where you need 5 microvolt per meter protection. But you usually extrapolate on those anyway.
A CE at a neighboring market cluster offered me an old AM FI meter with a spring tension linearity problem with the d'Arsonval meter movement. He unfortunately left the cluster before I could get there to pick it up. AM FI meters typically receive and measure down to 10 microvolts per meter. Makes it difficult to do upgrade applications with measured conductivity radials on Class I-A/I-B/A frequencies where you need 5 microvolt per meter protection. But you usually extrapolate on those anyway.
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Great video Mr Carter. Nice to see the SRIII is a contender. They had a poor rep, but I think the good ones were very good.
Mine is the most useful of all three Superadios, barring a bit of overload on two channels. It matches the other two models in sensitivity and selectivity. It has a 36K resistor in the antenna circuit, lower than the one listed on the schematic, maybe that's why its a decent performer.
The II sometimes has an edge, but not when using headphones, for some reason. All three are good radios.
RE: the Sangean PR-D5:
My PR-D5 is as sensitive, if not moreso, than either of my three Superadios (1, 2, and 3).
The headphone volume is low because of the dropping resistors in the headphone jack.
The PR-D5 doesn't have super hot AGC, but it is just as sensitive as a Superadio, at least the ones I have.
Whether it's a tuned RF or not, that depends on how you define 'Tuned RF' section in the day of SiLabs DSP chips with low noise amplifier sections that retune the antenna circuit (or re-tune to the antenna) each time the radio is retuned. I'm no tech, but that sounds similar in operation to a TRF. But because of the way a DSP chip seems to be set up -- perhaps it's not like a TRF.
The SiLabs datasheets have block diagrams, but whether a SiLabs DSP chip is equivalent to a 'Tuned RF' section radio I don't really know.
But the low audio described in that blog post: that's the resistors in the headphone circuit, combined with the DSP chip's slower AGC characteristics. Compared to a PR-D5, your average Superadio has ultra hot AGC.
Mine is the most useful of all three Superadios, barring a bit of overload on two channels. It matches the other two models in sensitivity and selectivity. It has a 36K resistor in the antenna circuit, lower than the one listed on the schematic, maybe that's why its a decent performer.
The II sometimes has an edge, but not when using headphones, for some reason. All three are good radios.
RE: the Sangean PR-D5:
My PR-D5 is as sensitive, if not moreso, than either of my three Superadios (1, 2, and 3).
The headphone volume is low because of the dropping resistors in the headphone jack.
The PR-D5 doesn't have super hot AGC, but it is just as sensitive as a Superadio, at least the ones I have.
Whether it's a tuned RF or not, that depends on how you define 'Tuned RF' section in the day of SiLabs DSP chips with low noise amplifier sections that retune the antenna circuit (or re-tune to the antenna) each time the radio is retuned. I'm no tech, but that sounds similar in operation to a TRF. But because of the way a DSP chip seems to be set up -- perhaps it's not like a TRF.
The SiLabs datasheets have block diagrams, but whether a SiLabs DSP chip is equivalent to a 'Tuned RF' section radio I don't really know.
But the low audio described in that blog post: that's the resistors in the headphone circuit, combined with the DSP chip's slower AGC characteristics. Compared to a PR-D5, your average Superadio has ultra hot AGC.
I've had all 3 models of the Superadio and the II was probably the best, although I've had the III the longest and it still did good for getting the weak Memphis area CCM stations I was trying to get at the time (late 80's and 90's). I still have it but I really don't use it much now since there isn't much on AM that I care about trying to get any more.
It was not until I borrowed a friend's SR-II and passive loop antenna a few years ago
(this one) that I realized how effective they really are, especially in the daytime.
I had always thought that they were smoke and mirrors lubricated with a few drops of fresh snake oil,
but they really do work, bringing stations from being buried in the background up to very listenable levels.
In fact, these band-pass filters tune so sharply that they even reduce strong adjacent stations.
(this one) that I realized how effective they really are, especially in the daytime.
I had always thought that they were smoke and mirrors lubricated with a few drops of fresh snake oil,
but they really do work, bringing stations from being buried in the background up to very listenable levels.
In fact, these band-pass filters tune so sharply that they even reduce strong adjacent stations.
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I built my small loop antenna in a rectangle using 2 X 4s, and #22 hook up wire from Radio Shack. Can't remember where I got the 365 pf variable capacitor. Anyway, you can easily rest small radios inside the loop to maximize the inductive coupling.
Hey Bruce. I loved this video. a little OT, but have you been able to play with a Sangean HdR-16 yet? Would like to hear your thoughts on it.
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rbrucecarter5
Guest
Nope - haven't. I don't have the funds to go out and buy any more radios, and the wife would be furious if I did! But if somebody wants to loan me a rig, I could do a side-by-side comparison with my best performer to date.
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rbrucecarter5
Guest
Covering three points ---
That 36k in the antenna tune section sounds like one of my modifications. You have to be careful - make it too low and the radio will start oscillating on one end of the band or the other. I get away with 39k in just about every SR-3 I have tested or modified.
Technically, the antenna stage of a radio is "tuned RF", even though it is passive. From the early days of the AA5 tube radios, there has been a variant where a sixth tube is added to amplify the antenna stage, so even using the term "amplified tuned RF" isn't enough. I will call them "amplified antenna stage" to differentiate. I have an old GE from 1947 that uses this design. It is not a good performer. The famous Sony SR-59's have an amplified antenna stage and are excellent performers. I don't have a radio based on the Silabs chip, at least not an AM radio. I do have an FM version and it is OK - not great, but OK. Wide selectivity, sensitivity good for local and near rim shots.
The low audio on the Radio Shack 12-603 - someone pointed out I should have used the headphone jack to direct audio in. Maybe next time - if I make another video. the low volume is real, I had to turn it all the way up. Since it uses the same chip as CCrane-EP, which does NOT have that problem, maybe I can trace down what is different and come up with a fix for Radio Shack. A CCrane EP schematic would be really beneficial! The thing that worries me is that the CCrane EP is prone to overload. If modifying the 12-603 also makes it prone to overload, then the problem is the IC, which dooms radios based on it to mediocrity. Perhaps there is a middle ground between low volume on distant stations and overload on locals. The IC may not be able to handle a tuned RF stage in front.
Which is where I get to my definition of "tuned RF stage". A separate, amplified stage. Three sections in the tuning capacitor / 3 varactor diode tuned circuits (or more).
Have you looked at the datasheet for one of the SiLabs chips in many of the modern popular DX and SW radios? According to their datasheet blurb, "the integrated LNA and AGC optimize sensitivity and rejection of strong interferers allowing better reception of weak stations." Isn't that similar to what a tuned RF section does: amplify and tune the antenna circuit ahead of the IF section? There's a block diagram in the datasheet, although it's not super detailed.
Here's a datasheet for the chip I believe is in the newer Sangean PR-D5's:
http://www.silabs.com/documents/public/data-sheets/Si4730-31-D50.pdf
Of course, with DSP, you probably don't have the standard superhet design after the RF section. According to the datasheet I'm looking at, the next stage after the RF section is the Analog to Digital converter. As I said before, I'm not a tech, so a lot of the info on the datasheet is probably above my pay grade.
But it looks similar to a TRF to me, in concept -- at least the way they describe it (I wish they described it better). It doesn't sound like it's a dumb RF amp section, like most modern analog IF chips have (including the chip in the SRF-59). The block diagram shows a tuner symbol in front of the RF amp. Then again, maybe it's a 'dumb RF amp' like the one you described was in the GE tube radio.
Although I'll admit, a lot of those 'dumb' RF amp sections in those analog IF chips do quite well. My Sony ICF-38, which has one of those chips, almost performs as well as a Superadio II, even though it has a 60mm loopstick inside it.
I wonder what a good RF section that rejects Images, IF Beat, Blanketing, and RITOIE combined with a narrow IF AND DSP would do.
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