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

Sat Apr 5 00:12:29 EDT 2014

Ray,

Like Bill it has been quite awhile since I have done any research into the 
subject myself.  I was a Broadcast Technician doing some work for the 
military during the early stages of the wars and have direct experience with 
the Poly-Phaser inline coaxial suppressors.  We used the high-end model 
(=high dollar) but the exact part number escapes me.  Our antennas took some 
direct and very close hits by lightning and the only thing we generally 
needed to replace was the filter.  However in two instances where our 
antennas took direct hits by lightning we had to replace the filter and an 
antenna element in one instance and in the other instance we had to replace 
the filter and coax feed between the antenna and filter.  To give you an 
idea of the type of equipment attached to the other end of the coax we used 
military grade ICOM receivers, Rockwell Collins transmitters and Raytheon 
Receivers to name a few.  These items were not cheap.  Bill is also correct 
in identifying that you can get the protection you need but it will not be 
cheap and you still have to design the system properly which includes clean 
power sources and proper grounding.  The Poly-Phasor website should be a 
good place to start along with some military TM's that cover broadcasting, 
grounding, and power systems.

Jeramy, KG4AZT

----- Original Message ----- 
From: "Bill Cromwell" <wrcromwell at gmail.com>
To: <homebrew at mailman.qth.net>
Sent: Friday, April 04, 2014 9:30 PM
Subject: Re: [HomeBrew] Validity of protection from available coaxial surge 
Protectors?

> ** Please do NOT cross-post messages when posting to HOMEBREW **
>
> On 04/04/2014 08:38 PM, Ray, W4BYG wrote:
>> ** Please do NOT cross-post messages when posting to HOMEBREW **
>>
>> 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/ì s):  1500V
>> 3. Max. Withstanding current(8/20ìs):  5kA
>> 4. Impulse discharge withstanding life( 8/20ìs, 100A):  300
>> 5. The minimum Insulation resistance at DC100V(GÙ ):  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 ìs pulse up to 1500 volts (in 15ìs?) 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
>>
> Hi Ray,
>
> I looked into this some time ago. You aren't going to get a lot of 
> protection from "a gas discharge" tube. You really can protect delicate 
> equipment form direct light lightning hits. But that requires a system 
> approach. $pell that with lot$ of dollar$. I don't know why you need to 
> operate when thunderstorms are approaching but I'm just an amateur and I 
> don't need to. I elected the much cheaper route of unplugging and 
> disconnecting *everything*. I'll see if I can find the name of that 
> company and point you at their web site. I think it's something like 
> Poly-Phaser. They have the numbers and the info you want. They'll sell you 
> as much or as little protection as you want. And yes - they have 
> documented cell and trunking sites taking multiple direct hits and 
> surviving.
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