Go Wireless!

Dave - That looks great - give us a report after trying it out in the real world. Thanks, steve in so az

Based on another thread on the forum, I purchased these wireless headphones (from Amazon, not Walmart though):

http://www.walmart.com/catalog/product.do?product_id=5184024

I also bought a 1/8 to 1/8" male to male audio cord at Radioshack and used it with the 1/8" to 1/4" adapter to connect it to my metal detector. Plus, I bought some velcro squares (with adhesive on one side) at the hardware store to stick it on my metal detector.

The headphones themselves are just OK. MANY times while I'm hunting, I'll get a loud static-y noise and have to press the reset button on the headphones to get it working again. But they're cheap - not too bad for the price. I wouldn't buy them for listening to music, by the way.

I'm wondering about RF interference with that transceiver mounted on the control box.

I've wanted to do this for awhile now, but the problem I have been hearing about is that there is a second or so delay between getting the signal. Have you had this problem and for those who have used wireless successfully in the field, what type of transmitters are you using?

Re: RF Interference

Joecoin:

A legitimate concern, for sure. I just did an experiment about 1/2 hour ago, as you peaked my interest with the comment.

I am also an Amateur (Ham) Radio Operator. I hadn't tried this until just now. What I did was put the detector within a couple feet of my vehicle, which is equipped with a dual-band transceiver (2 meter and 70 cm ham bands, 146 Mhz and 435 Mhz respectively), and a dual-band antenna, which has 3.5 dB and 6.0 dB gain on those bands. This yields an Effective Radiated Power of 112 watts on 2 meters, and 200 watts on 70 cm. Obviously the RF field strength of these signals is much higher than the field strength being radiated by that little irock FM transmitter. (Due to its power being MUCH lower, probably on the order of a few tens of milliwatts).

In any case, when keying the mic of the ham radio, on either band, it definitely triggered the detector to sound off each time I keyed the mic. It would do this even 10 feet from my car. In fact, if I put the detector too close to my antenna, I could actually "crash" the detector causing the microprocessor lock up so you had to turn it off and back on to reset it.

An interesting experiment. So much for RF shielding. (We hams get to deal with that crap all the time. It is called "Part 15 Devices". Thanks FCC).

However, I myself am not overly concerned about this, as I do not think that there is enough RF being emitted by these power-limited "personal" FM transmitters. I know that I saw no ill-effects in my tests last night in the coin (and other stuff) garden. The detector seemed to behave normally.

I am hoping for an hour or so park hunt this evening after work. I will post any observations.

HH,
Dave

bearbqd said:

I've wanted to do this for awhile now, but the problem I have been hearing about is that there is a second or so delay between getting the signal. Have you had this problem <snip>

Click to expand...

Hello bearbqd,

I have read some previous threads regarding that same thing. One thing to note...with the little FM transmitter/FM receiver (headset) setup, there is no delay whatsoever. If the detector is not sounding off, what you hear is just a "dead carrier" thru the headset. Something similar to a regular FM radio station forgetting to play a commercial or something ("dead air"). When the detector sounds off a tone, you immediately hear it in the headset radio. When waving the coil over a dime, I could not tell any difference from the corded headphones that came with the detector. The dime dinged right as soon as I passed the center of the coil over it.

I am thinking that it is possible to have a delay, though, with some types of DIGITAL 2.4 Ghz wireless setups. If the audio tone has to be digitized (converted to a bitstream), then transmitted over the RF link, and then un-digitized (converted back to analog audio tones), all of this going on could concievably take a fairly large amount of time. It would have to do with the speed of the analog-to-digital and digital-back-to-analog conversion that is used with any brand of these digital wireless setups that are out. The RF link wouldn't have anything to do with it....it travels at the speed of light (more or less).

Dave

I've been using the same type set up as yours for about a year now. There's no delay in signal and everything usually works well . . . except that there's a radio station right around the 88.3 setting, and when I'm using (but not swinging) the detector, oftentimes music comes through! Fortunately, I like the type of music the station plays, so it could be worse. :-) I really wish there was another frequency available that was clear, because I love the wireless convenience! The radio station doesn't seem to interfere with the detector's signals, but it sure is distracting! There's no way to determine when it will come in or out. Does anyone have any ideas about frequency? When I'm in more "serious" hunting mode, I just use the corded headphones.

It seems like this would be an open market item for a company to perfect and sell for metal detectors only. It would most definitely revolutionize detecting. I would HAVE to buy one. I'm all for getting 'un-leashed" from my detector. Even the thought of this! Somebody, please patent this idea and market an exclusive product. Got one sold, I know!

Changed the receiver

Hello everyone,

And happy weekend! Well, after the initial tests with the AM/FM headset radio shown earlier in this thread, I had to return it to the local store. I found that the headset radio was the most uncomfortable thing I could imagine! It kept shifting positions, back, forward...and fell off once. Hated the thing, really. So, I took it back and exchanged it for a Radio Shack Cat. number 12-469 digital portable pocket radio. It is a much nicer unit....digital freq. readout, 10 presets. It comes with ear buds but I elected to use some nicer Sony headphones that I had laying around here. It still serves the purpose of disconnecting me from the detector. The headphones are connected to the radio which clips to my pants pocket or belt loop. The irock! transmitter shown in the pics earlier in this thread is still attached to the detector, transmitting on 88.3 Mhz. Pics of the new receiving setup are below. It works great! Nothing but a solid dead FM carrier until the detector sounds off.

I did a quick 15 minute hunt around the grounds at my work at lunch today, and managed 1 quarter (1973), and two clad cancerous pennies, as well as 2 pull-tabs and a piece of can slaw. It works as if I had headphones directly connected to the detector.

HH to all,

Dave

b-boop said:

I've been using the same type set up as yours for about a year now. There's no delay in signal and everything usually works well . . . except that there's a radio station right around the 88.3 setting, and when I'm using (but not swinging) the detector, oftentimes music comes through! Fortunately, I like the type of music the station plays, so it could be worse. :-) I really wish there was another frequency available that was clear, because I love the wireless convenience! The radio station doesn't seem to interfere with the detector's signals, but it sure is distracting! There's no way to determine when it will come in or out. Does anyone have any ideas about frequency?

Click to expand...

b-boop: See the previous post regarding my change to the receiving setup. With these types of portable radio receivers, what they do is use the shield (ground) inside of the headphone wiring to become the radio antenna. When headphones (earbuds or other kinds) are plugged into the radio, the shield becomes the antenna.

The point I am trying to make is that the wire to the Sony headphones is about 4 feet long. Makes a <reasonably> good antenna. But, by wrapping it up and tying it up with bread ties shown in the picture, you can effectively reduce the antenna length and its ability to receive some of those stray broadcast signals. It still easily receives the signal mounted to your detector; which is close.

I have the same problems here. There are a few low-power college stations around here that were gettting through. Wrapping up the headphone cord to "just enough length" solved the interference problems and also keeps me from tripping

Plus, my transmitter has the ability to select 4 different frequencies...88.1, 88.3, 88.5, and 88.7 Mhz. With the "shortened" receiving antenna and the various frequency choices, the whole thing works pretty good. I select 88.3 around my home, and 88.7 at work (50 miles from here).

Hope this helps!

Dave

laserfocusguy,

If it's not too much of a hassle, could you loosen the transmitter and hold it away from the MD body at different lengths while swinging over a known target? Just to see if proximity to the box causes any issues.

A test not required

joecoin said:

laserfocusguy,

If it's not too much of a hassle, could you loosen the transmitter and hold it away from the MD body at different lengths while swinging over a known target? Just to see if proximity to the box causes any issues.

Click to expand...

Hi Joecoin,

I didn't think that the test is necessary. I did do something like that and what I found is that it affected the quality of the signal received by the radio on my belt; not anything with the detector. The transmitting antenna on the irock! unit is actually in that little short cord that plugs into the detector. About 4 inches long, and not near long enough to be optimized for the frequency of use. The position of it did make a difference in the signal. I ended up with what you see in the photos. Oh well, ya get what they make...

In any case, I show no interference to the detector...it works like it always did but with no cord. This is true of my Bounty Hunter.

Unfortunately, all electronics, and their shielding to stray RF interference is a matter of the design of the device. Can I say that it wouldn't interfere with your detector? Nope. I guess you would just have to try it.

Above posts I mentioned that I could swing the detector over a dime and see no difference as if I had the original corded headphones plugged in.

Dave

Have to admit I had a lot of interest in rigging up some sort of wireless system but found that hip or shoulder bagging the control unit pretty much accomplished getting the HP wire out of the way. I know some units don't have enough coil cable to do this but an extension would be cheaper than trying to rig all the stuff needed to go wireless.

For silent search or SS only units I would be constantly worried that the wireless unit is broadcasting properly. Last thing I need in the field is one more technical uncertainty.

I shoulder bag my sov unit and the HP wire runs up my back(yes it does look like I am carrying a purse). I can then set the rod down for digging with no HP wire pulls or entanglements. But that's just me, I could be wrong

Thanks, laserfocusguy. I'll give your new setup a try and will post results.

Hold Off

b-boop said:

Thanks, laserfocusguy. I'll give your new setup a try and will post results.

Click to expand...

Hi b-boop,

This will be just a quick post (I am at work right now).

I discovered something over the past weekend. There could be some problems with other brands of the FM transmitter; other than the irock! brand I showed in the photo in the original post. Don't go out and buy one just yet.

I will fill everyone in on the details this evening, and include a photo. I have another brand of FM transmitter....it didn't work right. (NOT RF interference, but something else).

More to come.........

Dave

Thanks for the info. I'll hold off. Can't wait to hear the details!

Gwen

sandflea said:

Have to admit I had a lot of interest in rigging up some sort of wireless system but found that hip or shoulder bagging the control unit pretty much accomplished getting the HP wire out of the way. I know some units don't have enough coil cable to do this but an extension would be cheaper than trying to rig all the stuff needed to go wireless.

For silent search or SS only units I would be constantly worried that the wireless unit is broadcasting properly. Last thing I need in the field is one more technical uncertainty.

I shoulder bag my sov unit and the HP wire runs up my back(yes it does look like I am carrying a purse). I can then set the rod down for digging with no HP wire pulls or entanglements. But that's just me, I could be wrong

Click to expand...

Hi sandflea,

Sounds like a nice setup. As you know, my original goal was to "detach the umbilical cord" between me and the detector. The BH SS II detector has the control box fastened to the search coil shaft. Since you are able to "wear" your control box, I wouldn't see the advantage to having a wireless link between the headphones and the control box. Like you said, it could just add one more possible problem to the whole mess.

Unless you're a super tekkie, and you like to have all kinds of equipment hanging on your belt.

HH,

Dave

.....More

Hello all,

To continue the saga of the FM wireless setup....

I have to back up a little. The irock! FM transmitter I showed in the original post starting this thread I have actually have had for a couple of years. As I mentioned earlier in this thread, I am a ham radio operator, so I have a mobile VHF/UHF radio in the vehicle like most of us do. Helps pass the time during the commute. I have a model made by Kenwood, which is a type that has a detachable faceplate (which is velcro'd to my steering column), but the bulk of the radio sits under the driver's seat. That includes the speaker. So, to hear the person you are talking to, you would have to have an external speaker mounted somewhere up front. I elected to, instead, plug an FM transmitter into the external speaker jack and transmit the receive audio on a regular "broadcast" FM frequency. I used 88.3 Mhz. It sounds really nice, full stereo quadraphonic sound through the car radio (oops, I just dated myself)

OK, since this worked so nicely, I bought a different brand of FM transmitter sometime later, to use with my Ipod Nano. Wanted to play digital tunes through the car radio while I am driving. I bought a brand named "Accurian". It seemed like a nice one...It had an adapter to plug into the cig lighter for power (it can use batteries too, but I have never used it that way), and I especially liked the fact that it had 8 transmit frequencies to choose from. Pics of this unit are shown below in this post. It turns out that I didn't use the thing too much, so it sat in my glove compartment for awhile.

When I first decided to try the wireless metal detector idea, I used the Accurian transmitter from the glove compartment. The signals when plugged into the Bounty Hunter MD when listened to on the "hip" radio, sounded very strange. Totally distorted and the audio tones seemed really distant and weak. Hmm. Didn't like it at all. So, for the heck of it I tried the irock! brand transmitter from the car, and sure enough, the signals sounded good. Evidently the audio signal level from the detector is too high for the Accurian, but OK for the irock!. So much for "standard" input signal levels. Gotta love today's consumer electronics. I think that the Accurian was getting "overdriven" by the MD. So, I ended up putting the irock! one on the metal detector and the Accurian one in my car. With the volume control on my ham radio, I can lower the signal into the Accurian so that it doesn't distort. I got lucky with these two setups for different uses working the way they did.

Now, to make the point....I think it is possible to "overdrive" these "personal" FM transmitters as they are called, with the signal from the metal detector's audio output. At least with mine it is. Only a 50% success rate. However if a White's, Garrett, Tesoro, Minelab, etc. MD has a volume control ON ITS CONTROL BOX I think it would work with any brand of FM transmitter, since you can attenuate the signal to the FM TX with the volume control on the control box, so not to overdrive it and get an undistorted signal/tones. My BH SS II, with its included corded headphones, has the volume control along the cord before it gets to your ears. That attenuates the signal at that point, which means the output from the detector is a fixed level.

Well, I hope this info has helped anyone reading it.

HH everyone,

Dave

Anyone ever try one of these wireless systems with a minelab Sovereign GT? I notice the bluetooth types for sale over at kellyco will not work with this detector.

Despite my last post I sill like the idea. When running a threshold it should be pretty obvious if the wireless system has stopped transmitting assuming of course it transmits the threshold.

Truth be known I detest wires of any kind and I think they have it in for me too. I can lay two wires down beside each other and look away for a few seconds and when I look back they have magically entangled with each other.

Ok that's an exaggeration but some times it seems like they have a mind of there own.