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  #21 (permalink)  
Old 06-12-2012, 9:10 PM
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Originally Posted by NeedtoKnow2 View Post
...My radio ownership points of reference are a 30-old GE 10 band Model 72971A , and a 15 year old Radio Shack DX390.
While I can't speak for the GE, I think this would be a very nice improvement over the 390. No major chuffing, and external antenna jacks, and more. If it's worth the money is up to you.

Let's see where to start ...

You do not want WD40 on the antenna jacks. Apparently they mistook the common complaint of popping during rotating to be purely mechanical. What you REALLY want is to open the radio, and use contact cleaner like DeOxit or similar for the rotating AM bar. Or just live with it.

The Terk and the Grundig tabletop loop are about the same. They perform a bit better than the stock am antenna, but you make the choice of clutter vs convenience. Inexpensive enough to try anyway. If you are dxing AM, these may be a better choice than the EndFedz wire, due to the loop / loopstick being very directional.

A key issue to remember is that this is a sub-$300 radio, that does a lot of things, but doesn't specialize, so there are things you have to deal with. Like easily overloading it with an external antenna. Yes, you can use the rf-gain control to sledge-hammer it into submission, but there is a "mid end" so to speak, and not just the front end, that needs attenuation when using very efficient antennas. This calls for opening up the radio, and soldering in an attenuating resistor right off the Toshiba IC chip leading to the am/ssb detectors. Even with that, it does not compare to a typical $500 radio - we are just taming it a little bit.

And yes, QC can be an issue like most radios these days - you basically take your shot and hope for the best. If this radio takes your interests a step further then great - but don't judge what even mid-level radios are capable of based on the Grundig. It is just a very convenient portable, that some like to eek out the most peformance out of - but there are just limits that can't be overcome unless you redesign it, or go hog wild with modifications - and ok, maybe then end up with a $350 radio.

Last edited by hertzian; 06-12-2012 at 9:22 PM..
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Old 06-12-2012, 10:39 PM
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As I opened up and read your reply, I just got off the phone with Amazon after asking them how to resolve the dead power supply that came with the Grundig tonight. Instead of just sending a new $5 wall wart, they have to send a whole new radio and of course I need to return the whole enchilada as well. They promised I will receive the replacement in two days.

Regarding high potential for overload, there is also a three level antenna attenuator on this radio. I would think that would help somewhat in addition to the RF gain in taming an over-aggressive signal.

Of the 1 hour I spent with the radio, aside from the dead power supply, I know I am going to enjoy it. Its ease of use, flexibility, tunability, and form factor are a lot nicer than my RS.

Sure, a $400, or even better, a $1,200 radio would be a lot nicer. But as with all things we have to decide if the time and energy we devote to it makes the price worthwhile and is it a priority for limited resources. I would imagine those who spring for the $400 to $1,000 rigs devote a lot more time to their hobby than I plan to devote to mine. Other hobbies compete, as do the mortgage and eating out occasionally.
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Old 06-14-2012, 1:55 AM
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Originally Posted by NeedtoKnow2 View Post
..They promised I will receive the replacement in two days...
Great! Ironically, the first thing I'd do is pack up that wall-wart, and run from batteries. The 750 draws very little current and can go for a loooong time on Alkalines, or better yet, rechargeable D's that are 5 amp or better rated. Beware of simple AA's inside D-cell housings. And by running solely from battery, you are disconnecting a possible noise source from either your ac wiring, or the wall wart itself.

Quote:
Regarding high potential for overload, there is also a three level antenna attenuator on this radio. I would think that would help somewhat in addition to the RF gain in taming an over-aggressive signal.
Yes, you can run it this way. But what we discovered on ssb/cw, is that you have to attenuate mild to moderate signals, that are no where near aggressive. Add to that the fact that the S-meter is about 10 - 20db optimistic. Having to attenuate clean ssb signals above the quarter-way point on the s-meter initially suggests that the front-end is overloading. Amazingly, it is the stage following the front-end rf amplifier that overloads first. With the resistor mod, you can now receive signals up to about S9 to +10 without overload, so the front-end is more capable of what was initially perceived. You may discover this when you attach the Par End-Fedz external antenna. At least the mod is there if/when you need it.

Quote:
Of the 1 hour I spent with the radio, aside from the dead power supply, I know I am going to enjoy it. Its ease of use, flexibility, tunability, and form factor are a lot nicer than my RS.
I'm sure you will as I do mine, even though I own a few other radios in different price/performance brackets.

Quote:
Sure, a $400, or even better, a $1,200 radio would be a lot nicer..
Yes, but even that is no guarantee of long-lasting quality either these days. I think you'll have a blast with the 750, but just remember that there is always something $100 better all the way up the scale into the stratosphere - so enjoy what you are getting now - you may be on the way to a lifelong upgrade process like many of us. There is no perfect radio.

Last edited by hertzian; 06-14-2012 at 2:03 AM..
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Old 06-14-2012, 5:35 AM
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Thanks, hertzian.

I'll have to develop some courage and confidence before I do the mod. I'll see how tolerable the status quo is for awhile and then come back for high resolution step by step guidance. And it doesn't help that I'm partially color blind. Didn't help much when I put together an Eico kit when I was a teenager. Got a few resistors put in the wrong place - dang little colored stripes!
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Old 06-14-2012, 3:39 PM
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Originally Posted by hertzian View Post
Great! Ironically, the first thing I'd do is pack up that wall-wart, and run from batteries. The 750 draws very little current and can go for a loooong time on Alkalines, or better yet, rechargeable D's that are 5 amp or better rated. Beware of simple AA's inside D-cell housings. And by running solely from battery, you are disconnecting a possible noise source from either your ac wiring, or the wall wart itself.
Cost effectiveness question:

What does a good quality, well filtered 6 volt power supply cost compared to 8 good quality rechargeable D cells and a quality charger?
8 pcs of Tenergy D Size 10,000mAh High Capacity High Rate NiMH Rechargeable Batteries - $54, not including charger. $85 with charger.
http://www.amazon.com/Universal-Batt...9709206&sr=1-7

Is there such a thing as a filtered noise free 6 volt DC wall wart? I spent a half hour Googling 6-volt power supplies/converter/adapters/wall warts, etc.(center pin negative) and it is almost impossible to tell how noisy they might be. Amazon may reveal noise levels based on extensive customer reviews, but I haven't spent the other half hour necessary to fully explore those options yet.

I anticipate running this radio at least 4 hours a day.

Last edited by NeedtoKnow2; 06-14-2012 at 4:34 PM..
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Old 06-14-2012, 7:01 PM
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Couldn't a toroid choke be used on the wire right before it plugs into the radio? Something like this from RadioShack?
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  #27 (permalink)  
Old 06-14-2012, 9:05 PM
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Originally Posted by vagrant View Post
Couldn't a toroid choke be used on the wire right before it plugs into the radio? Something like this from RadioShack?
Being less knowledgeable about electronics than most on this site, could you please elaborate about how that choke would be used for my benefit? Have you tried this?

How would it be hooked up? What is attached to what? In conjunction with the wall wart?

Yes, Herttzian was correct. I got my new Grundig wall wart via UPS today (thank you Amazon) and tried it out with headphones, and yes, there is a slight 60 cycle hum that can be heard when the volume level is fairly low. I doubt I would notice it without the phones or even with the phones with normal programming, i.e. without silent spots.
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Old 06-14-2012, 11:37 PM
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Originally Posted by hertzian View Post
we discovered on ssb/cw, is that you have to attenuate mild to moderate signals, that are no where near aggressive. Add to that the fact that the S-meter is about 10 - 20db optimistic. Having to attenuate clean ssb signals above the quarter-way point on the s-meter initially suggests that the front-end is overloading. Amazingly, it is the stage following the front-end rf amplifier that overloads first. With the resistor mod, you can now receive signals up to about S9 to +10 without overload, so the front-end is more capable of what was initially perceived. You may discover this when you attach the Par End-Fedz external antenna. At least the mod is there if/when you need it.
Will this mod affect the MW band? I have a strong medium wave (640kHz) station that creates audio distortion. I have the antenna attenuation turned up and the rf gain turned all the way down, and still hear it. But I discovered that detuning the rotatable MW antenna on top helps quite a bit to eliminate this distortion even more than reducing the rf gain or increasing antenna attenuation.

Regarding that mod, are there any details such as high res photos, detailed parts specifications/pictures, connection points, location within the radio, how not to fry anything, etc.? I searched the yahoo 750 user group and saw discussion of it but no detail.

Last edited by NeedtoKnow2; 06-15-2012 at 12:08 AM..
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Old 06-15-2012, 2:06 AM
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Originally Posted by NeedtoKnow2 View Post
...I'll have to develop some courage and confidence before I do the mod. I'll see how tolerable the status quo is for awhile and then come back for high resolution step by step guidance. And it doesn't help that I'm partially color blind. Didn't help much when I put together an Eico kit when I was a teenager. Got a few resistors put in the wrong place - dang little colored stripes!
Ok, here's what the mod looks like on mine. I put two 5600 ohm resistors in parallel to get me to 2800 ohms (2.8K) since I didn't have that value around. Anything from 2.5K to about 3.3K seems to find the right balance. An electrolytic capacitor 4.7uf 12v or thereabouts was added to block any dc, and was simply soldered to a nearby can. Of course look out for shorts to the board. This was my first one, and was pretty ugly, but there is room enough even when the case is screwed back down. (6 screws - 4 in the corners, one in the battery compartment, and one below the loopstick on the back). When you replace the cover, be sure to properly align the plastic tab slide that goes under the rotatable antenna. Again, many thanks to the Yahoo group where this mod first came about.

The resistors and cap were soldered as an assembly prior to placing it on the board so as not to drip solder onto the main board! Insulation would be nice, but the fat components I used were stout enough to hold above the board. The can was scratched a little bit to make soldering the electrolytic easier, with the negative side to the can. The resistor(s) are attached to only one pin - do not accidentally make a solder bridge, which I accidentally did at first as you can see. Of course this will immediately void your warrantee.

With this mod, I normally run the rf-gain control anywhere from 12 to 2 oclock. When the bands are quiet, I can crank it beyond that. When busy, I might just play with the rf-gain pot - rarely do I have to use the fixed attenuators.
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Last edited by hertzian; 06-15-2012 at 2:48 AM.. Reason: antenna tab alignment
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Old 06-15-2012, 2:16 AM
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...8 pcs of Tenergy D Size 10,000mAh High Capacity High Rate NiMH Rechargeable Batteries - $54, not including charger. $85 with charger...
I have that exact charger, and like it for it's ability to charge cells individually. Takes a fingernail to push the front latch to open. Yep, it isn't like my Maha 808M charger, but that charger with the batteries that would do ok. You'll have no problem running 4 hours at a time for maybe a few weeks.

I prefer low self discharge rechargeables myself, especially when there is no way you'll tap into 10amps of current daily - I run Maha/Powerex Imedion D cells in this application, however the Tenergy combo would work until you become a battery geek like me.
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Old 06-15-2012, 2:20 AM
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Originally Posted by NeedtoKnow2 View Post
Will this mod affect the MW band? I have a strong medium wave (640kHz) station that creates audio distortion.
Yes it does. However, many people don't notice the distortion in AM mode unless they are getting just hammered like you are. And, it vastly improves the airband AM reception as well when dealing with very stong sigs. Yeah, I'm not going to sit around and play with the attenuators and rf gain control for every plane that comes my way. The resistor mod makes the 750 a LOT easier to use for airband monitoring as well.

This mod tames that detector stage, but this might be a situation in which you are just being totally bombarded, and even higher quality receivers would have an issue on that freq.

Last edited by hertzian; 06-15-2012 at 2:54 AM..
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Old 06-15-2012, 2:59 AM
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Originally Posted by NeedtoKnow2 View Post
...I got my new Grundig wall wart via UPS today (thank you Amazon) and tried it out with headphones, and yes, there is a slight 60 cycle hum that can be heard when the volume level is fairly low. I doubt I would notice it without the phones or even with the phones with normal programming, i.e. without silent spots.
With phones, you may also notice a small amount of crackling in one of the channels when the volume pot is really low. I sometimes run at very low audio levels, and while the crackling isn't a showstopper, your brain can filter it out a little bit by using a mono adapter to make it appear in both ears strangely enough. When the bands are super quiet and I run low volume, this can appear - if it bugs me enough, I just raise the volume. Communications headsets alleviate this to a degree, unlike hi-fi phones. Another alternative is to use the line-level outputs into a higher quality audio headphone amp, which works very well, although you lose the bass control. The treble control still works with line level out.
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Old 06-15-2012, 12:15 PM
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Originally Posted by hertzian View Post
Ok, here's what the mod looks like on mine. I put two 5600 ohm resistors in parallel to get me to 2800 ohms (2.8K) since I didn't have that value around. Anything from 2.5K to about 3.3K seems to find the right balance. An electrolytic capacitor 4.7uf 12v or thereabouts was added to block any dc, and was simply soldered to a nearby can
With this mod, I normally run the rf-gain control anywhere from 12 to 2 oclock. When the bands are quiet, I can crank it beyond that. When busy, I might just play with the rf-gain pot - rarely do I have to use the fixed attenuators.
Thank you for the photo; makes things perfectly clear.

My observations and question below have probably been all hashed before, but I'll ask anyway...

1. The 930 watt 640 kHz radio station tower that overloads that signal is less than a mile away. Why isn't the 20 db antenna attenuation plus turning down the rf gain ALL the way adequate to reduce the overload sounding distortion WHILE detuning the AM antenna DOES eliminate the overload? Does this simply mean that the signal is so strong that it requires a lot more than 20db antenna attenuation? Does the antenna feed bypass the rf gain even though the S meter shows a reduction when the rf gain is turned down?

2. Cheaper radios or even car radios don't experience this type of overload distortion (at least not that I notice) even when I drive within a few blocks of that AM transmitter. What is the best explanation?

3. This mod has been out for some time now with good results by all who implemented it, true? Why do you think with all the radio expertise of Grundig or Eton or whoever is responsible for the circuit design plus the precision of the computerized design process has this $0.50 improvement not been included either originally or subsequently with later updates?

4. What are the performance downsides of this mod? What else is being affected (aside from the warranty)?

Last edited by NeedtoKnow2; 06-15-2012 at 12:17 PM..
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Old 06-15-2012, 12:33 PM
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Default Power supply questions

The owner's manual states: "A battery symbol appears in the lower right of the LCD, indicating battery or AC adapter power." So as I understand, the battery symbol is supposed to remain whether the radio is running from battery or wall wart power.

The owner's manual continues: "If there's a power failure with the AC adapter attached and batteries installed, the batteries will take over and supply power to the radio." This is not my experience. When I plug the wall wart into a switched outlet, with batteries installed, have the radio running off the wall wart and switch of the outlet, the radio turns of, while the clock remains on. Is my experience unique, or is the user manual in error?

Is anyone aware of a totally noise/hum-free 6-volt wall wart or other power supply? The one that comes with the radio sells for $10. I would think for double or even triple the money a well-filtered, hum-free power supply should be out there somewhere. A lot cheaper than a rechargeable battery setup.
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Old 06-15-2012, 1:00 PM
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Originally Posted by hertzian View Post
While I can't speak for the GE, I think this would be a very nice improvement over the 390. No major chuffing, and external antenna jacks, and more. If it's worth the money is up to you.
Let me say this about the GE: The Radio Shack 390 was about the same order of magnitude better than the GE as the 750 is better than the RS 390.

I liked the analog tuning of the old GE; no transmission would be missed with the continual audio coming out of the tuner. Not so with the RS. Not sure if it has a digital tuner or not, but I can't just spin the dial and expect to hear any indication of what might be out there. There is silence between each frequency. It seemed to take a microsecond for any transmission to kick in. Not so with the tuning of the Grundig. Much more user friendly like the analog GE, with MUCH better sensitivity and selectivity.

Can't wait to get my adapter and cable from Universal so I can hook up my Endzfeed longwire. Don't know why Universal has to wait 4 or 5 days before they even ship an order.

Actually, regarding the slight wall wart hum, it is so miniscule in my case (the only time I can hear it with headphones is when the volume is turned ALL the way down) that I am not going to worry about it. I never hear it through the speaker. For those who may experience a more bothersome hum, I'm not sure if this would do any better, but it might be worth a try: http://www.altex.com/Philmore-Multi-...A-P143093.aspx

Last edited by NeedtoKnow2; 06-15-2012 at 1:54 PM..
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Old 06-19-2012, 3:35 PM
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Default Loose antenna input?

Is anyone aware of the form of physical connection of the BNC shortwave BNC antenna connection on the side of this radio, specifically, is there anything inside that can loosen up that would allow wiggling the cable from the outside to cause a change in signal strength?

With my hand on the cable an inch or two from the BNC, when I slightly move the cable up and down, I get a change of signal strength of a bit more than 10db according to the meter.

My set up includes a PL-259 screwed onto a PL-259 to BNC adapter installed onto the BNC antenna input.

Is it more likely that one of these external connectors is causing the signal loss or something on the interior of the radio antenna connection.

My "fix" would be to install a BNC end to my coax and have a more direct input if you believe my adapter junk is messing things up.
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Old 06-22-2012, 10:52 AM
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Default Loose BNC jack inside radio

I solved my variable signal strength problem created when the coax is moved. The nut that holds the SW BNC to the ground inside the radio was totally off the threads. I finally discovered the cause of this issue when I noticed that the FM BNC was tight, and the SW's was loose. This can be determined from the exterior of the radio. Loose innards was my first suspicion. So my radio repair equivalent to Pepto-Bismal was to re-install and tighten the nut using a small flat head screw driver. I don't know of any wrench that can fit in there without removing the small circuit board located 1/16" behind the threads. Someone suggested the application of nail polish to assure the nuts stay tight.
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Old 06-22-2012, 11:08 AM
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Default MW antenna for Grundig 750

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Originally Posted by ka3jjz View Post
While any wire antenna would improve MW reception, it's at a price - everything comes in from all directions with no way to null one station over another. That's why loops are a very popular tool when DXing MW stuff.

As I recall, the PAR really isn't designed to go down that low - if it were me, I'd look at getting (or building) a box loop or similar if I were into MW DXing. I'm quite sure the NRC or the IDXC websites have plans for such, and it shouldn't be hard to find plans with a well structured Google search. In addition we have a few linked in our Loops wiki below...

Loops - The RadioReference Wiki

HTH...Mike
I recently tried the Terk ($31 at Amazon) and sent it back. Why? Primarily because the tuning knob, being located in the middle of the loop, is oriented away from me when the antenna is positioned where it tunes best. There is a good reason why the tuning knobs for the similar Kaito and Grundig loop antennae are located on the side of the unit. Performance-wise, the Terk did significantly improve a barely listenable 540 signal on the Grundig. At night, for reasons beyond my understanding, this antenna created more noise than signal when tuned to the highest S-value. It was a rainy night - maybe this influenced the result.

I just ordered a Kaito AN-100 ($21 at Amazon). There is also a Kaito AN-200 for $25 that appears identical with the Grundig AN-200 that sells for $30. The only difference I am aware of between the 100 and 200 besides the price is the 100 has a more functional base/platform, and the 200's have a more stylistic base - in my opinion a bit of form over function. One reviewer who owned both claimed no difference in performance between the 100 and 200.

Google "External AM antenna" on Amazon to see these, along with extensive reviews.

Last edited by NeedtoKnow2; 06-22-2012 at 11:11 AM..
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Old 03-31-2013, 8:08 PM
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Complete newbie here.

I know this is a rather old thread but...

I am interested in purchasing Grundig Satellit 750. I would like to know what the personal experience of other owner here is. I can tell you that this will be sitting on my computer desk. I will mostly be listening to AM/FM stations on it and will be exploring the shortwave world too. Outside of that, I am just generally looking for a solid shortwave radio that is not an internet based radio. In addition to having it sit on my desk I also want to be able to take,e it camping and use it out on my deck on summer evenings.

If there is a better radio for these purposes I am open to suggestions but I have to say that I am rather smitten with the Grundig Satellit 750.

Thanks,

Rob
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Old 04-01-2013, 4:21 PM
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Originally Posted by rosborn View Post
I can tell you that this will be sitting on my computer desk. I will mostly be listening to AM/FM stations on it and will be exploring the shortwave world too.
SW will be all but useless if the 750 is indoors and next to a computer. You'll likely get a ton of RFI. You'll have to set up an external outdoor antenna.

Get this PAR antenna and buy some RG-8x coax and a $3 BNC adapter. Orient the antenna away from the house (and any metal structures) if possible.

PS. For camping purposes, the stock whip antenna should be fine. Of course, you'll obtain even better reception with the PAR antenna strung up in a tree, etc.

PAR antenna: http://universal-radio.com/catalog/sw_ant/2205.html
Coax: http://universal-radio.com/catalog/cable/cable.html --> #0497 (or whatever length you need)
Adapter: http://universal-radio.com/catalog/parts/bncadapt.html --> #2122


-Nick

Last edited by nickcarr; 04-01-2013 at 4:25 PM..
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