[HomeBrew] Validity of protection from available coaxial surge Protectors?

[Ray, W4BYG]

I would like to open up a conversation on how much receiver front end
protection is actually afforded with the currently available coaxial surge
protectors.
 
My question to the list:  Is there anyone who is knowledgeable or
experienced on what kind of thru levels are typically sustainable by today's
modern receivers/transceivers?  Has there been any research on the subject?
Or is it all conjecture?
 
My quest started out with trying to find out at what level and over what
period of time commonly available coaxial surge protectors kicked in.
Numerous brands are available from $25 or so, up to about $90.  With
multiple antennas and expensive rigs of today, it seems important to be able
to characterize the level of protection one is buying.
 
Technical information is not very well published by the various brands.  I
haven't seen much published on what is needed.  The protector marketing
types just say buy ours and you will be protected.  That seems like a bit of
"snake oil" to me, kind of like days of old, out West.
 
Without wanting to reflect poorly on MFJ, I had occasion to query a past
employee of theirs on the technical details of their coaxial surge
protectors.  The gentleman genuinely tried to find out the information, but
was unable to provide any engineering wisdom as to what represents real
protection.
 
Regarding their product he shared they had not done any actual testing of
the gas surge protectors.  They just trusted the Asian manufacturer's specs.
Also there was no real information about what does it take to actually
protect the front end of a receiver or transceiver, from induced surges on
an antenna.  I understand virtually nothing can protect you from a direct
lightning hit, but nearby strikes can induce a lot of possibly divertible
energy.  In response to my query on one MFJ model I got:
 
The gas discharge tube in MFJ-272 is SRYG-1000L.  
 
1. DC breakdown voltage(100V/s):  800~1200V
2. Impulse breakdown voltage(100V/μ s):  1500V
3. Max. Withstanding current(8/20μs):  5kA
4. Impulse discharge withstanding life( 8/20μs, 100A):  300
5. The minimum Insulation resistance at DC100V(GΩ ):  10
6. Max. Capacitance(pF):  1.5
 
I then replied in part:
 
...The numbers confirm my concern about just how much protection can there
be letting a several μs pulse up to 1500 volts (in 15μs?) into the front end
of a transceiver or receiver before the devices fires and shorts out the
energy to ground.  I don't have any factual insight on this.  
 
I would appreciate any comments from those that have tested this subject and
have come to some reasonable resolve.
 
I understand the need for a trigger voltage somewhat above what might be
experienced with a kilowatt transmitter and a moderately high SWR on the TX
line.  1000 watts of RF at 50 ohms could produce about 223 volts RF.  At 100
ohms load (2:1 SWR?), there could be about 316 volts of RF, etc.   For
peak-to-peak voltages, I would multiply both numbers by 2.828 for 630.6 v
P-P and 893.6 v P-P respectively.  
 
With such a device as spec'd ... I just wonder if there is any real
protection of the receiver first active stages other than possible
protection from fire in the shack?...
 
I repeat my question:
Is there anyone who is knowledgeable or experienced on what kind of thru
levels are typically sustainable by today's modern receivers/transceivers?
Has there been any research on the subject?  Where can one find it?  Or, is
it mostly conjecture?
 
Your attention and thoughtfulness is appreciated.
Ray, W4BYG
 
 
 
 
 
 

Ray, W4BYG 

"The Republic can survive a fool for a president...  It is less likely to
survive a multitude of fools, such as those who made him their president."