Whites MXT with Logitech wireless headphones Bluetooth technology

[Gen. Breckinridge]

White's MXT with Logitech wireless headphones Bluetooth technology

I hate the hassle of the headphone cable so I bought a set of Logitech wireless headphones that use Bluetooth technology. As I understand it in the U.S. Bluetooth technology is confined to a band of frequencies of 2.4ghz to about 2.5ghz. Now to me that would mean that there should be absolutely no interference between the transmission in the low microwave band (Bluetooth) and the low frequencies of the MXT BUT...

When I started using the new headphones I was delighted at first. The freedom of movement, excellent sound, ultralight headphones, no sweating ears, then I went to pinpoint and nothing! At first I thought I must have pulled the pinpoint switch back over some kind of junk but it happened every time I tried to pinpoint. Finally I took off the Logitech headphones and went back to the old ear cookers and immediately pinpointed every hit that I had with no problem.

Looking at the problem as an electronics engineer (I was the supervising engineer of three TV stations for the last dozen years of my working life) the first thing I did was check the frequency allocation for Bluetooth wireless devices and found them on the frequencies earlier mentioned.

To me there should be absolutely no interference but it seems that the Bluetooth frequency is desensing the metal detector in the pinpoint mode. Considering that the pinpoint frequency is not given in any of the MXT documentation I assume it is on 14khz or a lower VLF frequency, I could be wrong, but no way is it going to be in the microwave range of frequencies. I also considered what frequency the local oscillator might be running in the Bluetooth transmitter but there is no way it would be as low as 14khz. I have not drug out the spectrum analyzer to "look" at the headphone transmitter since it is buried under other test equipment and would serve no usefull purpose since there is no way to change it. The only thing I can come up with is a subharmonic of the oscillator is the culprit here.

If anyone has had the same problem I would like to hear from you OR if anyone is using wireless headphones with the MXT I would like to hear from you also. I know that infrared would not work dependably so the headphones will have to use an RF frequency to make the connection.

To compare the difference in frequencies:
Bluetooth is 2,400,000,000 hz
White's MXT is 14,000 hz
A long way apart!

Thanks to all of you who have read this post and I hope I can find a dependable set of headphones that will do the job with out the interference.

 

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[Sheldius]

Re: White's MXT with Logitech wireless headphones Bluetooth technology

Were you pinpointing while standing or when you were diging the target? I just ask because maybe you weren't in the line of sight for the wireless system anymore.

Good luck.

 

[Gen. Breckinridge]

Re: White's MXT with Logitech wireless headphones Bluetooth technology

I was standing in the same position that I used to find the target. I tested the range of the headphones prior to hunting and found the signal could not be lost, no matter where I stood within 20 feet or more, even through the wall in my basement. I'm sure I was not losing signal from the transmitter. Thanks for getting me to clarify that point.

 

[Gen. Breckinridge]

Re: White's MXT with Logitech wireless headphones Bluetooth technology

After some serious serarching on the net I found some favorable comments on the Sentry Wireless Headphones that Wal-Mart sells for $18.73 on line. The range is up to 100 ft. so they are not bluetooth. Although the ear cups are full, padded there were favorable comments on their comfort. I ordered a set and will post the results here when they arrive. I also ran into some comments about time delay in the bluetooth devices (makes sense since they probably packetise the audio which could cause a delay). The Sentry model number is H0900 and although I couldn't find any comments about frequency of operation I'm guessing they are in the wireless phone band around 900 mhz. That would be a perfect frequency for what we want to use them for. I'm going to give the Logitech set to a friend who is a detector dealer and hunts with a Tesoro most of the time, so he can see if they will work OK on the Tesoro.

 

[Tom_in_CA]

Re: White's MXT with Logitech wireless headphones Bluetooth technology

Very interesting! I am very dubious of using any type of chordless headset, for this very reason. I have seen my detector loose depth and start to stutter around certain power lines, and in the middle of busy dense downtown big city traffic, d/t lots of radio signals @ peak hours. It makes me wonder if cross-talk can "only" occur if the signals/frequencies are exactly the same, or if more subtle cross-talk can occur just if they are close.

One time I was detecting, while using my blue-tooth cell-phone set under the cups of my earphones. My phone rang, and I answered it using the blue-tooth. As I was talking to the person, I decided that......... since it was hands free..... I could keep detecting even while talking on the phone But as I tried to do so, I noticed that my Explorer was acting very cr*ppy. Once I ended the call, the Explorer cleared up. Was it the cell phone? Was it the blue-tooth? I dunno.

 

[Tom_in_CA]

Re: White's MXT with Logitech wireless headphones Bluetooth technology

Vito, you're right, the major interference is the cell-phone itself. That is totally audible interference, w/o the blue-tooth. But I still wonder if there isn't un-audible cross-talk, since....... the blue-tooth is emitting so much less power, yet enough that it's under the audible range, but still there. Like in the analogy of two detectors moving far enough apart so that the audible cross-talk ends, yet they have to move further still, to truly be out of cross-talk range. There continues to be a range at which it's in-audible, yet you're loosing depth.

I guess the answer to this question is: Is there a gaurantee that only exact-like frequencies interfere with each other? What if they are close in frequency, like only a few #'s off?

 

[Gen. Breckinridge]

Re: White's MXT with Logitech wireless headphones Bluetooth technology

Update, the Wal-Mart Sentry headphones failed about 5 minutes after I turned them on. Who knows why! I'll be looking into the problem but if I can't find it I'm going to convert them to wired since they feel so good on my head. More later.
Ken

 

[Gen. Breckinridge]

Re: White's MXT with Logitech wireless headphones Bluetooth technology

I decided to check out the Logitech headphones in the yard on the Garrett Ace 250. The delay is obvious and I attribute it to the Bluetooth technology. The information is probably digitized and put into packets to sent to the receiver in the headset, all which creates delays in transfering the information. This is not a problem on music but it sure sucks when using it for metal detecting. On the Ace the delay is about 5-7 inches on a normal swing rate. When I swing the detector it takes about 3 seconds for a pass so the delay would probably be less than a 1/4 of a second. In the pinpoint mode it worked OK but move the coil VERY slowly! As far as I'm concerned the headphones using this type of technology are useless for metal detecting. How simple could it be to make a transmitter to transfer the sound to the headphones? Not hard at all but no one seems to be doing it with quality equipment. Anyone want a set of Logitech headphones cheap?