Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Does this radio come with a power cord / wall wart, or it is battery only?
Document: But the Long wave band, you will need a huge loop with alot of gain for this radio unless you live in other parts of the world with long wave broadcasters who use lots of RF power.
Performance is as expected. However controls are difficult and the manual is not very helpful. Example: turning power on too quickly puts the radio in "sleep" mode. To turn sleep mode "off" the station-tuning dial must be turned to display "On".
The radio sounds great, has average sensitivity. The big problem with it is that it cuts out, actually shuts off after ten minutes or so of playing. I have to hit the power button again and it plays for a while again and so on. It would be a good radio if it did not have quality construction and or design short comings.
The Grundig g8 receiver is well designed. With the auto tuning, reception power, and sound quality in such a compact  size, this radio is all you will ever need in a portable unit. I would have liked to have had an external antennae connection for better short wave reception, but all the other features make up for this one shortcoming in my estimation
Gary Debock said all that needs to be said about this radio.The only thing that was sub par was the owners manual or lack of.FM with headsets is just plain fun to listen to. I love the back-light with the rubber coating. If you do add a power supply be aware that center  connector is minus 6 volts. Check out the Yahoo Ultralight-dx group for any other information on this model & the Chinese like radio.
As long as you're aware of these things, they don't really interfere with normal operation.I ordered a separate power adapter from the manufacturer for indoor use, just in case, but I bought this radio primarily for travel. Also, a connection for an external antenna would've been nice a option in theory, but in practice, I doubt that I'd ever use an external with this particular unit. In order to keep the price low, it makes sense that these two features were excluded.
I bought it for the office which is a typical glass/steel building. Some radio stations didn't come in well with my old radio but this one does an excellent job in pulling in stations. Quality of build is good with a lot of functionality. Good on batteries.
As many others have noted, this is a great little radio with lots of features. However, I was shocked to discover that it does not come with its own AC adapter. In all my years of buying electronics I can't recall a single time this has happened.Maybe this is standard practice for portable radios (?)
Don't expect to hear stations 100 miles away or more that may come in better in your car, this is a small radio with a small antenna after all.A con I have is lack of antenna jack, but for a radio this size, I'm not that upset.LW (longwave) really has never worked for me here in the Western U.S.
This is the best little radio i have ever owned. I have bought many. It is clear sounding. The stations come in clear and the far away stations are easier to receive. I love the short wave, I like to listen to ewtn radio. When i turn on the radio the last station i listened too is still there. I would recommend this radio to anyone.
Answer: This radio requires 3 AA batteries which you must purchase. Additionally, it has a 6 volt dc socket for an after market transformer or power source ( check radio shack or Wal-Mart)  next to the plug for a head phone.  I usually get about 50 to 60 hours before changing batteries depending on brand.