I heard on a video earlier that a low pass filter should be grounded, is there any truth to this? I'm running one mobile ungrounded and notice if you touch it it'll give you a little zap. I haven't been able to find any other information on this and am curious if it's not grounded if it's working right etc. thanks for your help.
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Low pass filter grounding
- Thread starter Mgmac07
- Start date
i just installed the filter to make sure I wasn't interfering with anything and my buddy said it was fuzzed his truck radio up a little when I keyed up while we were sitting next to each other so I just wanted to see if it needed grounded or if the filter is just junk and I was only able to find one video reference stating it needed grounded and no mention of it anywhere else I have looked. It's a little rm filter.
Basically it should already have a ground thru the coax cable shield. There is no way it should give you a "little zap" unless you have lots of power out and some common mode currents on the shield which is quite possible being mobile. As for the radio next to you being overloaded that can happen with a barefoot radio at that close range.
Not sure what your antenna situation is but make sure the mount is making a good connection to the vehicle body and no coax is damaged.
Then try winding a coax choke at the antenna feedpoint. About 5 turns on a 4 inch form or use a stack of ferrite cores around the coax right under the antenna. Check the datasheet to make sure the ferrite mix you choose is effective at 27mhz.
Bingo on common mode current but if the installation is bad enough it doesn't take that much power. I have a amplifier here with a odd looking spot on the side of the case where it arced to the seat bracket. Nothing major, most people would never notice it.
A couple hundred watts and a bad antenna install will give you a tingling sensation that escalates into a burning sensation shortly...the good old days.
Then try winding a coax choke at the antenna feedpoint. About 5 turns on a 4 inch form or use a stack of ferrite cores around the coax right under the antenna. Check the datasheet to make sure the ferrite mix you choose is effective at 27mhz.
Bingo on common mode current but if the installation is bad enough it doesn't take that much power. I have a amplifier here with a odd looking spot on the side of the case where it arced to the seat bracket. Nothing major, most people would never notice it.
A couple hundred watts and a bad antenna install will give you a tingling sensation that escalates into a burning sensation shortly...the good old days.
It happens usually after I've done some transmitting, i haven't tried touching it while I'm transmitting. I'm using a tri mag mounted to the trunk with two 10 gauge wires ran from the mount base to the chassis for a ground and my swr's are a flat 1 according to my meter. I ran a ground wire from the filter to the chassis earlier and I'll see how it goes tomorrow. I really appreciate everyone's help.
Common mode will only zap (burn) you when you are transmitting. Is this simple static build up like from dragging your feet on the carpet? An rf burn is a much different experience.
Get yourself at least a quarter mile away from whoever you're talking with rather than trying to get a meaningful signal report from less than ten feet away. Receiver overload might be the least of the worries.
Your wires are doing nothing for grounding for RF. Go to www.k0bg.com and read up the section on bonding and do that to your trunk lid and as in the page use braid, not wire.
Something doesn't smell right if that is indeed the case. For that to happen he would have to have a total break in the shield of BOTH coax cables on either side of the filter since the cables are grounded at each end of the system.
I agree, there is something he isn't posting.
I would remove one of the ground wires and ground all parts of the shield/filter/radio to one point
Mgmac07, get yourself a cell phone to talk to your buddies and forget the CB radio, or remove the filter and move on down the road before talking to your buddies.
I agree with a previous post...something is missing in this story.
I agree with a previous post...something is missing in this story.