HELP

[flightchecker]

Hi Navman and Hans,

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.

if I was you, I would ask AirNav what is ment by "a continual discharge". At least I don't t know this "term", while I know pretty well, what it is about Electro Static Discharges and Static build-ups.

Secondly, I would try to get an explaination on what are supposed to be "unusual charges" (with other words, where is the difference between "usual" and "unusual" charges) or even "charges" themselves, that you should prevent your antenna from, and by what means.

Therefore this does point to either weather, certain antenna setup, accidental
discharge. However we are trying to pinpoint it.

That's indeed an honest answer that makes sense, exept for the "accidental discharge", as again I would ask where it could result result from. (My only suggestion, the antenna is almost touching a 10 KV HI Tension line, which I doubt, has not been taken care of)

AirNav should continue to "pinpoint" this problem, That's what I would agree. There are measures of testing electronic devices regarding their "susceptibilty", which is the common expression for an instruments immunity against ESD among other external influences as strong RF fields for instance, and which is part of the specs. of "commercial" equipment.

And: Yes,

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

good suggestion, even customers might not be too glad about.

I for my part will follow this thread with very much interest.
 
Regards

Karl

[AirNav Support]

All,

Our Hardware team have found the following:

Usually RF circuits are very sensitive to static, when they are connected to external outdoor antennas, where the wind, thunderstorm, rf signals, contribute to generate local static energy that acumulates and can discharge trough the device. To avoid this to Happen, for those who have external antennas, a coaxial DC Block device can be used. Distributors like W&S generally have this kind of devices."

The RadarBox does have protection built in however to a certain extent. You can view the attached document to get a sense for the best protection.

Please note while cases of these are rare they can happen.

[CarlosAbreu]

Hi to all

I read this topic very carefully as I turn ON my WiMo antenna two days ago with excelent results.

I would like to know from comunity and AirNav Support the best recomended Static Discharge Protector model from Waters & Stanton to instal in my Wimo antena.

I suppose CA23RW is agood option as it has 'N' femeale connectors, it seems that it must be instaled only in ecoflex cable without more procedures.
The only doubt I have is where it is positioned, in the antena output (external) or in amplifier input ?

However, as I'm not an expert on this subject, I would like to know other ways to ground the antena.

It's possible to connect a wire from my antena metal base to ground imput of my external climatization box in order to reduce the risk of electrical discharge or this isn't correct ?

Any suggestion is apreciated.

Thank you.

Brgds
CA

[flightchecker]

Hi Carlos and AirNav,
 
W&S's Static Discharge Protector CA23RW as far as I can judge by looking up their websites is more supposed to be what one would call a "lightning protector", that will bleed extreme static discharge as experienced during strong local thunderstoms. I doubt, that the CA23RW (as its accompaning similar devices) is designed to sense and bleed static build up beside of that mentioned before, but discussed in this thread.
And it is not at all a DC Block as refered to in AirNavs proposal. Its Specs confirm it to operate from DC to xxx Mhz / GHz, while a DC Block (which in its simplest layout is a Capacitor between a coaxial In-/output) that prevents DC to reach and (possibly) destroy a device (a receivers input for instance) if it exeeds the devices immunity against DC. It may be placed directly in front of the devices (amplifier / receiver) input. 

There is a lot of DC Blocks available in the "commercial RF world", just "google" for "DC Block".

Your mastheadamplifier might as well serve as an "ESD protector", provided its immunity against the ESD is "high enough". (whatever that means) But I would not take that too serious, Carlos

Regards Karl

(We've got the same names, hav`nt we ?)


P.S.: Check this link for a "typical" DC Block and its (relativly simple) design.

http://www.rlcelectronics.com/newpdf/2006_6/BL-20A_a.pdf

Don`t care about the connectors, there's others available, your choice.
K.

 

[CarlosAbreu]

Hi Karl

In fact German Karl is the same name for Portuguese Carlos.

Thanks for your information, excelent advise, I don't want to have any problem with so expensive hardware.

I will look carefully for the suggested link during this weekend.

Many thanks and have a nice weekend.

Brgds
CA

[Navman]

Hi all,
Since getting my RadarBox back from repair by Waters & Stanton on the 12 June 2008 I have been using it on the default antenna located inside my attic without problems as recommended by AirNav Support.

Over the last few weeks I have been carrying out some test on my antenna mounted outside on the chimney. The coax cable feeding the antenna is connected to ground at the receiver end thereby grounding the antenna and mast via the cable.

During a very heavy rain storm I decided to connect a voltmeter across the coax to see if I could measure any voltage build-up. I connected one test leads to the cable screen and as I connected the other lead to the inner core of the coax there was a crack and a spark about 4 mm long from the coax to the test lead.

This indicated to me that there was a large static voltage build-up (probably several thousand volts) on the antenna being caused by the rain storm. I waited a few seconds and then shorted across the cable ends with a screwdriver and again this produced a static spark. I have no doubt that this would have caused damage to the RB if connected.

I then connected a coax tee connector on the end of the coax and connected a 10K ohm resistor across the tee to bleed away the voltage before it could build up. With the resistor connected across the coax, shorting the coax produced no sparks and I could not measure any voltage. I then removed the resistor and within seconds shorting the coax again produced a spark.

This brings me to the DC blocking device as suggested by AirNav. These devices only give protection up to a few hundred volts some much less, the one mentioned by Karl works up to 100VDC. Static voltage can easily reach tens of thousands of volts. DC blockers rely on a capacitor for isolation which would breakdown if the working voltage is exceeded. The result of this would be goodbye RadarBox.

Static Discharge Protectors for example the CA23RW is not a DC blocker. It is designed to discharge static to ground when the voltage across the coax reaches 230 volts DC. This is not guaranteed to give protection to very sensitive equipment against static. It is more of a lightning protection device.

My suggestion is to use a CA23RW with a good solid ground connected to it to capture lightning strikes (not direct hits) followed by a coax tee with a 10K ohm resistor soldered into a plug connected to the tee. The tee then connected to the RadarBox. The 10K resistor across the coax will prevent the static build-up in the first place. I have tested this setup on the default antenna in the roof and the 10k resistor does not affect sensitivity.

I have been monitoring for voltage build-up across the coax from the outside antenna for a few days with this arrangement and detected nothing.

I would appreciate comments from anybody including AirNav support on this.

Jeff       

[flightchecker]

Hi Jeff, it's me again.

Excellent contribution regarding this thread, and Yes: I forgot about the "susceptibility" of "DC Blockers" rearding "ESD".
Originally they are supposed to prevent (RF/ MW) measuring- equipment and -setups (for instance) to be confronted with Dc- rather than RF Signal -components only, that sometimes happen to appear both in the applications mentioned before. And Yes: they are specified regarding their ability to withstand DC components up to a named amount, and ESD could well be harmful to them, the "capacitor" finally being the critical element.

Jeff, you won't have much success trying to measure static build ups with a common Multimeter, as the discharge, that you have noticed across your "spark gap" is "transient", while following its "naturally" behavior , and cannot be catched by a DVM, but needs a "storage oscilloscope" (for instance instead) with its ability to capture "transients".

Anyway, your "solution" sounds good, at least, if AirNav will not propose a better one.

Take care, to "design" your solution from an "RF point of view", means, choosing a "low inductance"  (metal film, and as small as possible) resistor, which you probably already have done.

Another methode to overcome ESD problems would be a "DC grounded" Antenna, which will eliminate Static at its "place of origin".

I will PM you on that, Jeff

Karl

[Navman]

Hi Karl,

Thanks for you comments, I have over the last few days been using a storage oscilloscope which I borrowed from work to monitor the static voltage on the coax and the bleed resistor seems to be doing a good job.

I have installed the bleed resistor inside an N-type plug so that it is completely screened. As already mentioned I have tested this arrangement on the default antenna in the attic and it seems to have no detrimental effect on the performance.

I agree that a DC grounded antenna would be a good option but my antenna was quite expensive to install so I don’t want to change it for another type.

Anybody using an external antenna (not the one included in the RadarBox package) that is DC open circuit should be aware that damage could be caused to their equipment if precautions are not taken to prevent static build-up (ESD).

Regards Jeff

[flightchecker]

Agree Navmann,


Karl

[John Racars]

Hi All,

I am not a technical-specialist, so I do not exactly understand what I have to do when my RadarBox will be back from repair. Unfortunately I still do not have my RadarBox back. Here some questions I have:

Should I stop using my WiMo GP-1090 and re-use the AirNav default antenne?

Should I ground my WiMo GP-1090 so I may use this antenna again without any danger?

Should I buy a CA-23RW? And, if so,  is this module compatible with my WiMo GP-1090 (and ECOFLEX 10 cableconnection) or should I buy an adaptor or so?

Thank you again in advance for your reaction(s)!

[Cumulus]

Hi All,

Should I stop using my WiMo GP-1090 and re-use the AirNav default antenne?

Should I ground my WiMo GP-1090 so I may use this antenna again without any danger?

Hi John,

You may also consider replacing your antenna with the SSE 1090SJ mk 2 which is DC grounded with excellent peformance and at £50 + p&p an inexpensive option.

Regards,

Peter

[flightchecker]

All

AirNav’s responds regarding this thread’s subject makes it obvious to me, that during the development of their instrument, care has been taken concerning  its susceptibilty against ESD.
For me (maybe there’s other menbers of the forum too) the applied ESD test standard (Human Body Model  [HBM] IEC61000-4-2 f.i. ? ) and its accompaning compliance level would be a matter of interest. Also, if  the corresponding “discharges” have been applied directly to the RF Input (sma- connector) rather than to other PCB components.

Would you tell me, AirNav?


Regards
Karl

[CarlosAbreu]

I've checked on Google a lot of sites with DC block's and ESD's...however I still confused.

I'm not an expert on this matters as many other users, I would appreciate from Airnav Support, if possible, a recomendend ESD model to aply on ANRB as they have done with Wimo antena (the one I use) in order to buy it as soon as possible.

This is only to prevent any damage on the hardware, there's any guarantee for this kind of problems, however, the risk can be strongly reduced with an efective protection.

Comunity, please send your feedback to this sugestion.

Brgds
CA

[AirNav Support]

We will see if we can find one to promote. Please remember if you have antenna with a preamp which dcs blocks anyway (the one sold on our site does) then you do not need to worry about this.

[flightchecker]

Hm,

does this mean, one has to worry about the pre-amp then? It faces the same "static" as does RB.

Would you say, it's got a higher "ESD robustness" as has RB ?

And: "DC - blocking", as already mentioned in earlier postings is not an answer regarding the issue it is about. Even not if achieved via a pre-amp.


Regards

Karl


P.S.: For those who are interestet a bit more in "ESD Protection", exspecially if applied for "RF receiver inputs", I have attached a link below, that covers this subject in some depth.
Similar App. Notes might be available by other producers than the one publishing this, which was found purely accidently.

http://www.eetindia.co.in/ARTICLES/2004DEC/A/2004DEC03_RFD_AN02.PDF?SOURCES=DOWNLOAD

K.