6400M/6600M Front End Protection

While others have addressed best practices for protecting ham radio gear from lightning, I'd like to address the "more sensitive to over-power damage, electrostatic charge on the antenna and nearby lightning surges" comment.

First off, all electronic equipment, regardless if it is a superhet or a direct sampling SDR that has a connected antenna is always vulnerable to the EMP from a direct or near lightning strike; the amount of energy and fast rise times can damage a whole array of electronic components.  The only way to mitigate this threat is with proper lightning grounding techniques and good lightning arrestors.

Electrostatic discharge is handled similar to lightning mitigation, but to ensure it presents a lower risk, the lightning arrestors used for lightning mitigation should also have circuitry to bleed off DC static from the center connector of the coax.  The ICE designed lightning arrestors (now Morgan Manufacturing and sold by Array Solutions) are very good for this purpose.

There is also protection built into the FLEX-6000 themselves to mitigate EMP and static discharges with the use of sacrificial ESD diodes that are designed to **** and break the RF signal path before the sensitive components experience any damage. This protection should NEVER be your first line of defense.

Overpower damage is a different type of risk that has to be managed differently.  The FLEX-6000s can tolerate high signal levels, higher than other direct sampling SDRs. The FLEX-6000 constantly monitor the RF input signal levels and have a relay that will open if the signal level reaches the threshold point below where the ADC would experience damage. This is accompanied by an error message indicating that a signal overload condition was detected.  This condition usually happens when transmitting while receiving, which is when operating in full-duplex mode or you are using a radio with multiple SCUs (ADCs).  If you are not operating this way or there is not another transmitting antenna in your receiver's near field, you really don't have to be concerned about overload situations

It is the operator's responsibility to manage the amount of signal entering into the radio's ADC in these situations.  We have a signal level worksheet that can help you determine if your setup is going to exceed the signal level threshold. http://www.flexradio.com/downloads/flex-6000-fdx-power-calculation-worksheet-pdf/

I live in central NC and while not the lightning capital of the lower 48, we are #3 on the list.  In the 23  years I have been at my QTH, lightning has struck the house across the street twice, the house 3 doors down once and struck trees behind my house twice (one as close as 100').  My antennas and house are higher in elevation that all of the other strike points and I have never experienced any lightning-related damage other than a cordless phone. I have incorporated extensive lightning grounding at my QTH, using a halo ground around the home, all of my coax shields are grounded to a bulkhead connected to the halo ground before entering the house and I use the ICE lightning arrestors too (I have blown a few of these up as a result of the near strikes).  I have a set of coax switches that ground the center pins to the halo ground when the radio is not in use.  This grounding system based on best engineering practices and grounding antennas when not in use works and works well.  You just have to access your risk factors and decide how much lightning mitigation engineering you feel is necessary for your particular situation.