Re: [smartBridges] Why no varistors in outdoor units?

[Bill Clark]

Bobby, I agree that TVS devices should be used to protect the radio's Ethernet port. It's almost certainly cheaper for sB to do that than not.   That said, the common cause of blown Eth PHYs -- whether or not protected -- is failure of the installer to 'bond' the ground rod used to ground the antenna to the mains-panel ground rod. In the US, the NEC requires this and specifies how to do it. (But the NEC does not teach that an overlong bonding wire is useless or that it is sometimes better to not ground the antenna. For sure, don't leave an antenna ungrounded unless you *fully understand* the issues!)   Also note that were sB to add TVS devices, the NIC at the other end of the cat5 run is likely to be damaged unless it is also protected. Internal protection of Ethernet ports is uncommon.   Bill ----- Original Message ----- From: Bobby Bounds To: [EMAIL PROTECTED] Sent: Saturday, 09 August, 2003 15:39 Subject: [smartBridges] Why no varistors in outdoor units? If you look inside a decent quality modem you'll see two blue capacitor looking parts soldered on the board. These varistors protect the modem from electrical surges coming in from the phone line. If you look at the boards on the SB outdoor radios no such varistors exist. So, I ask why not? If SB units had these would they be much better at dissipating static charges in the ethernet before damaging the radio?   We've had terrible problems with induced charges in the ethernet that runs from the outdoor unit to the indoors. We've seen the ethernet side of ABO's and APPO's blow out. We've seen the WAN port of routers blow out and we've seen the charge travel through the router and zap the NIC's in the PC as well. So, for those of you who are new to installs and live in areas where electrical storms exist, you have no choice but to come up with a grounding solution. This is a very big deal not just because of the need to prevent equipment damage but also because a good grounding system can increase the WISP's cost to do an install by a couple of hundred dollars if you consider both parts and labor. The problem is if you use SB equipment, there is no provision on SB radios to facilitate setting up a decent grounding system. In fact, because the ethernet that comes with the unit is unshielded, it can be argued the SB outdoor radios are improperly designed to address the 'induced charges in the ethernet' problem.   I know the subject of 'grounding' has been beaten to death on this list but there seems to be many opinions on the correct way to do grounding and it is not really obvious to us as to the best way to go....and SB offers very little help and advice on this. You can go broke buying coax lightning protectors and ethernet surge protectors and shielded CAT5 and on and on.   Clearly, putting the radio outside complicates the grounding situation. This negates the advantage of the outdoor radio. So, SB it is in your best interest, if you want to sell lots of outdoor units, to really solve this problem. I hear you are going to sell a beefed up PowerShot w/lightning protection but it will cost extra (bad idea). It is in your best interest that your units don't get easily zapped as is the case now.   These are the things I know of that can be done or need to be implemented in the outdoor radios:   1. Redesign the radio with an internal connection system for CAT5 (maybe a punch down block...I dunno).   2. Metalize the radio enclosure.   3. Publish an installation spec that leaves no doubt as to what constitutes a proper grounding system.   4. Improve the design of the ethernet circuity so that it is more resistant to static, such as the use of varistors.   Regards,     Bobby Bounds Airwave Internet