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.

I have also posted this in the General Discussion forum.

 

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[Gen. Breckinridge]

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

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.

 

[JohnNZ]

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

Hi I too an am Electronics Engineer
I use Bluetooth a fair bit.

It sounds highly unlikely that BT is jamming the MXT. Are you sure that the bluetooth freq range for the audio is wide enough for the high pinpoint tones? ie sufficient audio bandwidth?
are you also sure that in pinpoint mode you still have sufficient battery voltage for the bluetooth power supply.
let us know how you get on

John

 

[Gen. Breckinridge]

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

JohnNZ,
That is exactly what I assumed that the freq. of the Bluetooth was so high that even if the L.O. was 1/1000 the final freq., it still would be way to high to interfer and I doubt they are multiplying the oscillator by 1000.
The specs on the headphones were 20-20,000 hz so that would not be an issue. The batteries in the detector were new and I had just charged the NiMH Bluetooth batteries.
By the way the Wal-Mart headphones arrived today. Much to my dismay they are not on 900 mhz, but are on 49mhz, still, theoretically, that should be OK unless the frequency of the oscillator is a third overtone of the fundamental crystal frequency (just over 16mhz which is getting close and could desense). I hope to test them out tomorrow so I will try to report tomorrow night about any interaction. The Wal-Mart headset certainly feel and fit good and are not to heavy, although the transmit unit is a good bit larger by comparison to the Logitech. The headset itself is of much higher quality than the "$59.95 professional headphones" that Kellyco gives with detectors they sell which is not saying much for either set (grin).

 

[JohnNZ]

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

Hi

I still find it strange- you would think in pinpoint mode the audio would be just different in frequency. So it works well in non pinpoint mode?
is the bluetooth unit on the mxt side powered by its own batteries?
I wonder if its losing partnership with the headphones when in pinpoint mode? when you exit t pinpoint mode does it work OK again??
I have thought of getting some of these imported from the USA (I am in New Zealand) but will not if it does not work properly
let us know how you do

regards
John

 

[Gen. Breckinridge]

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

I still find it strange- you would think in pinpoint mode the audio would be just different in frequency. So it works well in non pinpoint mode? It works fine in the coin/jewelry mode. No loss of depth noticed.
is the bluetooth unit on the mxt side powered by its own batteries? YES, built in rechargeable
I wonder if its losing partnership with the headphones when in pinpoint mode? when you exit t pinpoint mode does it work OK again?? I hear the threshold sound but it doesn't increase when I pass over the target.
I have thought of getting some of these imported from the USA (I am in New Zealand) but will not if it does not work properly
let us know how you do. If you are considering the Logitech I would look elsewhere. The headphones are very uncomfortable which is why Ebay is loaded down with them for sale.

Like I said in the earlier post I have the Wal-Mart brand and hope to try them this afternoon. The headphones are very comfortable but the transmitter is much larger.

 

[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

 

[JohnNZ]

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

Ken

hmnnn.. i think ill just stick to my long cord - sounds very unreliable..
if you just switch the first ones on and have them close to the whites does it work OK - IE give correct sounds - that will test whether they are jamming it or not..
john

 

[Jonesin]

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

I bought the Creative CB2530 bluetooth, and they had about a 1 second delay. I ran a "Y" adaptor from my MD, plugged the Creatives in 1 and the wired in the other, and there it was. Took a s**t load of empty holes to figure this out. So I tried the Radio Shack #33-1253 and they don't have the delay, but like you said, it cuts out sometimes in the pinpoint mode, it's kind of choppy audio. I run a DFX, so it should be the same. Do you think since pinpointing runs in DC and motion runs in AC that the DC could be interfearing?

Tom

 

[khouse]

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

WS4B,
What model Logitech are you talking about?
Also I posted about 4 months ago that the Creative 2530 had a delay in the signal. Don't buy them. I run the RS#33-1253's with very little problems. I have noticed that when I have a deep iron coin beep the headphones will break up a little. I have now dug enough targets to know it's pretty accurate. I don't know why - but it's just another tool I use. But I'm always trying different set ups looking for the perfect wireless headset.

 

[Gen. Breckinridge]

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

After buying two sets I'm getting a little tired of blowing the money. I can't find a model number on the Logitech bluetooth set but they are all over Ebay for around $30. It ended up that I had to wear them upside down to make them a little more comfortable. They are the design that the headband goes behind your head, not over it. I really like the feel of the Wal-Mart wireless set but they are on 49mhz and I was afraid that was going to be a problem. Besides that the transmitter is huge. I'll try the Logitech with my Ace 250 and see if that may work. The Wal-Mart set may get converted to wired if I can open them up and not breake them. We ahve a Radio Shack here in town and I may give them a try to see if I encounter problems with them. At least I can get my money back if I don't like them or they cause problems.
Thanks for the input.
Ken, WS4V