I made an antenna

[Ism]

out of an RCA style audio cable. It is 6' long. It is thin enough to fit through the hole in the lower shaft but I chose to go outside with Velcro wraps but tywrapped it to the coil.
I cut the ends back exposing the center conductor 1-1/8 to 1-1/4 (I made it before reading the thread about antenna requirements).
Before heat shrinking the ends, I hot glued the area around the shielding and outer jacket and also the end of the center conductor. When heat-shrinking, the hot glue melted and formed with the heat-shrink to seal everything from water..
I tested the cable in a 5 gal bucket and then for a couple hours in a shallow creek. The cable end must be within a couple inches of the control box to work but otherwise it works just fine.

If I should be experiencing better distance from the control box please let me know and I will re-cut the ends to proper specs., otherwise the exacting measurements aren't a strict requirement.
These are very easy and inexpensive to make (free for me, I had everything on hand). Just wanted to share in case others were wary about making their own.

If there is interest in a step by step picture tutorial, I will be glad to make and post it.

 

[JoshuaA]

Ism, looks good! A step by step tutorial would be awesome for those wanting to make their own. I plan on working on mine later this afternoon. What did you use to connect the antenna to the coil?
Thanks for sharing!!!

 

[JBM]

I use plastic ties cheap disposable and simple to use.

Just cut them off when going back on dry land. :thumbsup:Jerry.

 

[Ism]

Thanks guys..Joshua, I used a tywrap. There are removable ones that you can purchase, but I think I will be using a velcro tywraps. That way I can unlash the antenna from the coil for charging without cutting a tywrap every time.
I will show in pictures in a day or so..

 

[Terry(Mi)]

I made 3 of them rca style antennaes and they all ended up failing within a few dunks. Sometimes they would test OK in the bucket, but fail at the lake. I ended up bucking up and making mine out of 7mm coax with the solid copper 1 mm core, it hasn't missed a beat.
I also used hot glue on mine, melted out the extra bubbles, and cinched the edge of the glue with 1" length of 9 mm heat shrink tubing.
You can sometimes tell if your not transmitting full juice with the RCA wire if your hearing the normal amount of chatter before dunking the coil, and then it runs quiter underwater.
Also, if u use the solid core coax your distance on the rec end to the remote can be much greater than an inch or two.
If you can keep the RCA antennae working then stick with it, if you start getting a lack of chatter or chopped signals then your wire is pretty much kaputz!
Good luck either way

 

[Ism]

Thanks Terry, That is important info because it can save a lot of wasted time. The reason I used the RCA style is because of the small diameter in comparison to standard coax cable. It may be important to consider the coaxial resistance and capacitance. I think that it may be necessary to solder the stranded center conductor because each strand could/will radiate if left in their stranded state. I also found that the stripped end length of 1.370 inches does not work for the RCA style audio cable (chopped signals). The only way it would work was by placing it on top of the coil. I got much better performance from 1.125 inches and could mount the cable like Finder82's photo. I may have never guessed that shortening the end would improve performance if I hadn't made the first one wrong (which works great).

I had my pictorial all ready but now I have to do more testing before I post it. Plus many don't have a soldering iron, hot glue, heat shrink and heat gun, so the outlay could get pricey just for an antenna.

Ran

 

[Finder82]

Here is the antenna, that my cousin has been using:

http://postimage.org/image/65tle9hpz/
Use regular antenna wire, strip away the outer plastic to expose the copper mesh. Cable diameter is 7mm= 0,275 inch.

http://postimage.org/image/dl6uzqe51/
Pull back the copper mesh to see the inner copper wire. Dont cut the copper mesh, leave it peeled back and seal it together with the rest of the cable. the exposed inner copper wire should be around 35mm= 1.37 inch.

http://postimage.org/image/6foaorjth/
Strip away the transparent plastic protection to expose the inner copper wire.

http://postimage.org/image/qmbhz8z9n/
Then use adhesive heat shrink tube to first seal the inner copper wire, then place another adhesive heat shrink tube over it so that the adhesive heat shrink tube overlaps the first one, then use yet another adhesive heat shrink tube to seal the whole exposed wire thing and make sure it is totally waterproof or it will not work.

 

[Terry(Mi)]

I tried 1.125" on the RCA on up to 1.37". I could never get the longer one to work and the 1.125 would work for 1-3 outings and start giving me fits.(yes it's odd the shorter copper strands worked better)
I never did try to solder the RCA strands, that may do the trick. It could get pricey for some folks to do the mod, but Hot glue guns are fairly inexpensive especially the smaller size. The shrink tube I bought was approx 1.30 for a foot, and I took my time and shrank it down with a bic lighter. Coax pricing runs all over, but can be had for less than $20 for shorter lengths. I got a 10' piece from someone who recently switched satellite providers. If time permits I'll pop up a pic later this eve.

 

[sandnsea49]

Why take off the clear plastic of the copper wire after removing the shielding, just to replace it with heat shrink? Seems like the clear plastic would be very waterproof since it is factory made.

 

[ALOBROGE]

hello good realization bravo.
I leave you two solution a first solution, which allows the immersion of the coil.
Then the second solution that allows total immersion of the device under water, with waterproof earphone.
Proposed solution on the FORUM XP.


http://www.xpmetaldetectors.com/xpforumfr/viewtopic.php?f=19&t=785#p1915

 

[sandnsea49]

n/t

 

[Ism]

It seems pretty much any coax cable will work but certain considerations must be observed. Stranded wires should be soldered (as well as the outer shielding IMHO). No need for soldering if it has a solid center conductor as well as a foil jacket.
The outer shield acts as a conduit for the RF signal. The length of exposed wire on the coax is likely a fraction wavelength making it highly conductive to the RF signal .
If you simply use "hook-up" wire, the signal would be damped by the water and never make it to the control box, in addition to the fact that its not a matched antenna and wouldn't radiate the signal very well.
So the coax behaves similar to fiber optics conducting the radiated signal at the coil through the coax and out the other end.
This is how I see it but someone else here may have a better explanation.

In my pics I didn't solder the center conductor which I recommend after reading posted concerns.
The hot glue just needs to be run down the length of the trimmed conduit.
The heat used on the heat-shrink will soften it so it flows nicely for a water tight finish.
A drop of hot glue will ooze out of the end of the heat-shrink which can be trimmed after it cools.

The length of the unshielded center conductor appears to differ depending on the type of coaxial cable used. For the thin audio cable it looks like 1-1/8" works good, for the larger RF coax cable it appears that 1-3/8 is required.
I haven't done any thorough testing I am going by what I found for the small audio coax cable and what Finder82 posted for his RF coax antenna which is usually around 7mm (1/4") dia.
Smaller diameter RF coax is available but all the fore mentioned variables must be taken into consideration.
HH
Ran