HELP

[flightchecker]

John and Navman,

However, it was very windy so perhaps the air movement past the antenna caused the static build-up maybe.   

Absolutely right, and if even the air appears to be "dry" due to low humidity, this will increase
risk and amount of static-build up. On all antennas as AirNav states correctly, and not only on antennas of course, as you might verify when you leave your car, and its static build up discharges through your body, as soon as you touch the car's door in order to close it.

I asked John already, if he "grounded" the antennas pole to earth, and will discuss with him via PM tomorrow on that. Did you Navman ? because this might reduce the risk of "static" to meet the receivers input, but drain to earth / ground instead of. 

Kind regards


Karl

[Dan]

Also  "undercooled" rain and hail can be the cause of a  heavy static build up especially with vertical antennas in such way that reception becomes impossible. With shorter VHF and UHF  antennas it is less noticeable but still can statics load the antenna.
This happens especilally when that rain or hail falls in the close neighborhood of the antenna and not directly on the antenna.
Rgds
Dan.

[Navman]

Hi Karl and Dan

My antenna pole is not directly grounded to earth but the coaxial cable from the antenna is connected to ground before it is connected to the RadarBox.

The coax cable from the antenna is terminated into a PL259 plug this connects to a Watson-7515 Static Discharge Device which in turn connects to the RadarBox via a short length of low loss coax with an SMA plug into the RB.

The Watson-7515 static discharge device outer casing is grounded to a good earth connection so this effectively grounds the antenna pole via the coax. Having said that the Watson-7515 is nothing more than a straight through connector with nothing connected to the inner of the coax to discharge any static on the active element of the antenna.

I think that I should replace the 7515 Static Discharge Device with one that incorporates a gas discharge fuse which would shunt any build-up on the inner of the coax.

Do you think that this would give adequate protection for the RadarBox?

Navman

[flightchecker]

Hi Navman, Dan, John,

I'd  prever to ground the antenna's pole rather than the receiver's end of its coaxial feeder, to bleed possible static-build at its "place of origin", so that it might not travel down the feeder, possibly acting via cable capacities between its inner conductor and outer shielding.
Concerning  the static discharge protectors: up to my knowledge, they are more thought to act as a countermeasure against those static build-ups, that one will find during lightning strikes in the very close vicinity. The one you're talking about Navman is a " mechanical spark gap", and static build ups, that result apart from lightning strikes probably will not force it to "fire", but reach a receiver's sensitve front end circuit, there causing possible harm. Some of them are fuse protected, but before the fuse "goes", the receivers front end might have "gone". I doubt, that "gas filled" dischargers will do better regarding the situation we are talkink about. The problem with the customer that I mentioned when I joined Johns posting, at that time, and as already told, had been solved by a redesign of the input circuitery, finally by selecting a hybrid component, whose "self protection" against "static" made it more "immun". (Resulting in no more complains on that issue anymore)
So far its all suggestions we are talking about. Let's see, what answer AirNav is coming out with on this phenomena.

Kind regards,

Karl

P.S.: May I kindly ask all readers to "cross fingers" for me: I've never in my (long) live taken a mains plug out of the wall during thunderstorm activities overhad, and  (don't trust my theories above !!!) I never removed any antenna coax from any of my "receivers" regarding the same scenario. 

But: I HAVE CONNECTED MY VIRTUAL RADARS ANTENNA POLE TO EARTH !!!

K.

[Navman]

Hi Flightchecker,

I agree with everything that you say. Unfortunately it is not practicable for me to ground the antenna pole to earth as my house is 3-floors high and I would need a very long flat copper earthing tape connected to a spike in the ground to do this effectively.

I have been a Ham Radio operator for 28 years and never had any static problem with my equipment, I have another antenna located about 4-metres away from the RB antenna for my scanners no problems.

I certainly don’t want to go back to the antenna in the attic for the RB as reception was very poor in comparison to the one the chimney.

As you say I think that we need to wait and see what the Tech Guy’s at AirNav come up with. I’m sure that they will find a solution to this problem.

Navman

[belgianguy]

What I wonder is, if this problem with the radarbox also occurs when we use a pre-amplifier, because I see that all the problems occure with installations without a pre-amplifier. Would a pre-amplifier react as some kind of buffer for the static electricity if the input of the pre-amplifier is not so critical as the input of the radarbox? Just wondering.

[flightchecker]

As you say I think that we need to wait and see what the Tech Guy’s at AirNav come up with. I’m sure that they will find a solution to this problem.

Agree Navman, and if yes,  we’d encourage AirNav to please come up with some technical details on that too.

What I wonder is, if this problem with the radarbox also occurs when we use a pre-amplifier, because I see that all the problems occure with installations without a pre-amplifier. Would a pre-amplifier react as some kind of buffer for the static electricity? Just wondering.

Good question belgianguy, and it  makes sense at a first glance, but build-ups might reach the receiver via the outer conducter (shielding) of the feeder cable. Lots of theories so far, again: AirNav will “tell the truth”.

Had a discussion with one of my former customers this morning on the subject it is about, and he reminded me, that it prooved to be good practice placing a “bleed resistor” between the inner and outer conducter at the antennas feed end. If its value is about 50 to 100K (and preferable even carbon- (or another "low inductivity") type, it will create only a marginal influence  on the low (50Ohms) Antenna- / feeder- / receiver impedance, but , by its name,  “bleed” static build-up to ground /earth, assuming, the latter provided!!!.

Just another idea, lets wait for AirNavs answer.

Karl

[flightchecker]

Hi WiMo / Ekki, Do you read?
You might be the one to have the answer for all of the above ???


Karl

[Cumulus]

I have a Solid State Electronics 1090SJ Mk 2 antenna which is DC grounded . I have checked both the Wimo GP-1090 and the BS1100 and both are open circuit with no ESD protection. The SSE antenna is connected to a Kuhne LNA 1090 A TM preamp also with ESD protection for the preamp frontend.

http://www.ssejim.co.uk/sseads1090sj.htm
http://www.kuhne-electronic.de/en/shop/143_Vorverstaerker/article:342_KU_LNA_1090_A_TM

[flightchecker]

Sounds good, Cumulus, sounds very good.

I myself, using the Wimo 1090GP since about one and a half year: NO complains at all so far.

Karl

[flightchecker]

Hi belgianguy,

Would a pre-amplifier react as some kind of buffer for the static electricity if the input of the pre-amplifier is not so critical as the input of the radarbox? Just wondering.

(your question)

had another discussion with an earlier customer of mine this afternoon, and he indeed used
many of "victim type amplifiers " (my best best translation of the german expression for this solution) between his antenna and receiver feeders. They indeed were "sacrificed" if it came to Electro Static Discharges. Relatively "simple" amplifier modules, that only served for the purpose discussed above. Discharge travelling on the outer conductor / shielding was taken care of by grounding the outer conducter at the receivers input connector. Unfortunatly in "case of a case", the "victim" was gone. Probably not a satisfying "solution" for us hobby guys.

I think we (I!) definitly should stop theories now and here, as there have been sufficient.

AirNav will tell us more.

Karl

[Navman]

My RB has now been repaired by Waters & Stanton; I sent the email below to AirNav support. Their reply is not very helpful.

Do I go-ahead and connect it to the outside antenna and risk another failure?

Email to AirNav support:

My RB is being dispatched back to me tomorrow from Waters & Stanton after being repaired for the second time. From reading on the forum there certainly seems to be a problem with static build-up on outside antennas reported by some users causing such failures. I am concerned that it will fail again if I connect it to the outside antenna.

Can you tell me if anything has been done to my RB to prevent further failures and are here any precautions that I can take here to prevent this happening again?

Reply from AirNav Support:

Thanks for your email.

The RadarBox parts are being tested further and sent back to us. However the RadarBox does come with static protection however the damage we are seeing usually shows a continual discharge.

I would suggest making sure nothing is causing your antenna to get this unusual charge.

What is very important so far is that we see nothing wrong with RadarBox, it does have protection but in these cases its facing a high voltage which is beyond normal conditions.

Please do not hesitate to contact us if we can be of any further assistance.

Navman

[AirNav Support]

The important part of the message is that its still being tested and that so far nothing has been found pointing the blame at the RadarBox.  (if we had kept hold of it and tested you would have emailed as you did requesting a return asp)

We did suggest did you early on to use it with the default antenna untill we pinpoint the cause.

All in we have over 1,000+ RadarBoxes across the world now and we have only had a handful of repeat cases where this issue has come up. Therefore this does point to either weather, certain antenna setup, accidental discharge. However we are trying to pinpoint it.

[Navman]

AirNav,

I will run the RB on the default antenna in the attic as it was before it first failed. If you can suggest any changes that I can make to my antenna i.e. fitting a more efficient static discharge device or maybe a bleed resistor across the coax then please let me know.

I am willing to try anything that will enable me to use the outside antenna as the performance is much better than the default antenna in the attic.

Navman

[Allocator]

I'm still using the BS1100 external antenna, as I have since shortly after I got my RadarBox.  I use the standard RB antenna when I go portable or working away from my home location.

I always unplug the antenna when I switch off the PC and when there are thunderstorms in the area.  All I can say is that My RadarBox is still just as sensitive as when I got it.

Of course, it doesn't mean that it won't blow up tomorrow, but I think that it's unlikely after all this time (looking out of the window for passing thunderstorms!)

Edit:  I've just checked when I ordered my RadarBox - July 2007 - has it really been almost a year, wow!

That means that its been almost a year since I stopped using my SBS-1, which I got in July 2006 - amazing!