[MRCA] M151 DC Distribution and the MX-7777

[Ray Fantini]

I have a MX-7777 and the pre-built cables that go from the GRC-106 to the MX but everything I have seen for the M151 shows the direct connection method or what I am doing with a stud in the battery compartment. Looking at the MX have to wonder about running all the power thru the signal connector on the back of the unit, like the big three pin plugs on both sides of the MX but not the smaller input.
I tried to open the MX but it appears sealed, want to see what's inside but imagine that will remain a mystery. If anything if all it is just a big zanier diode or MOV maybe will install that across the stud that's the distribution point for all the radios or perhaps I can throw together a simple L/C high current filter between the battery and electrical system of the mutt for that function?
Would wonder if the batteries themselves tend to work as both transient suppressors and brute force regulators and issues occur when you have the charging circuit from the vehicle somewhat isolated from the batteries and the radio equipment falls in somewhere between. In my layout all the electrical system of the mutt terminate at the starter switch and a #0 cable runs from that point back to the battery where it's connected directly to the battery. Another #0 cable goes from that point to the slave connector and a third #6 to a 60 Amp fuse and the distribution stud where all the radios are feed from. The one foot jumper from the battery terminal to the stud are the weakest link in the system with its line mounted fuse but would like to think if there is trouble anywhere that's where I want it to be. The jumper was from the battery tray of a commercial UPS system that we junked at work, the old APC UPS systems are a good source of used parts for short high current wire and fuses.

Ray F/KA3EKH

From: mrca-bounces at mailman.qth.net [mailto:mrca-bounces at mailman.qth.net] On Behalf Of WA5CAB--- via MRCA
Sent: Tuesday, June 13, 2017 1:52 AM
To: mrca at mailman.qth.net
Subject: Re: [MRCA] M151 DC Distribution

I'm sure that you're correct about early installations but installation of the MX-7777/GRC is not limited to armored vehicles.  I've had people report having it in M37's, M38's.  It wasn't the vehicle that determined whether you got one or not.  It was the radio.  Vehicles equipped with AN.GRC-3...8, etc. don't need it.  All the solid state stuff does.  They can't hack the transient spikes generated by the starter motor.  The T-195B might need it.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 06/12/2017 17:36:45 PM Central Daylight Time, kg2bz at comcast.net<mailto:kg2bz at comcast.net> writes:

ray. the original  grc106 install instructions
called for all cables hardwired to the batt terminals.  later on the standoff terminal kit for the 151 was developed probably to make it easier to disconnect or replace batteries. all the other install kits for different vehicles called for hardwiring right to the batt post.  the only vehicles that had dc overcurrentptotection of radio power cables was on the armored vehicles using the mx7777 combination breaker and transient suppressor
Sent from my iPhone

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