Not sure if there are many audio installers familiar with amateur/ham radios, but I seem to have a problem when I'm keying the mic.

For background info, my radio operates on the 144-148 MHz (2m) band, so its not operating on CB frequencies, but the setup is similar to a CB in case you are not familiar with these radios. It'll put out 55W on high power, it still uses an external antenna, and power is straight to the battery (highly recommended by the manual), so both positive and negative are to the battery.

My positive connection from the amp (powering the sub) also goes to the battery, and I have the negative from the amp going to the same ground as my rear tail light. So the only thing my audio and amateur radio share is the positive terminal on the battery.

The problem is when I key the mic, the sub will give out a single thump when I press the mic, and a single thump when I release the mic. The thumps are usually louder than the bass from the music. Nothing else other than the single thump when I first press down and the one when I let go.

Does anyone know where I might need to start looking to fix this problem?

 

Cell phone transcievers (3 watt) used to cause that too in the old days - it is the RF output from the antenna causing it. The front end on the amplifier is picking it up. Happens with us all the time in the lab - the powered computer speakers go "whap whap" everytime we key up a 5 watt portable, let alone a 40 watt LMR.

Don't know what to suggest to solve the problem though, other than trying a different amplifier for the subs if you have one. That one seems to have a sensitive front end (preamp stage), and some amps don't pick up the RF as badly.

Sometimes moving the transciever as far away from the amp as possible helps, also check the antenna connection and make sure it isn't leaking RF.

Mark

[ February 13, 2005, 05:46 AM: Message edited by: NOBASS ]

 

Try the radio on a different power source and see if it goes away... If it does you need to isolate power ground for the radio....

Ive had this happen with CBs..

[ February 13, 2005, 03:01 PM: Message edited by: Haunz ]

 

My brother was getting a thump through his subs when he was using his Mike phone in his truck too. We were checking all of the connections, he though his deck had a problem..... [img]smile.gif[/img]

 

My initial thought too,power supply noise/ or too much demand

 

Thanks for the suggestions, i'll give the different power source a shot.

I have also been told that I may want to put on some ferrite chokes onto the cables as well.

 

Well, I haven't checked the alternative power source yet, but I did try out the ferrite chokes and it seems to work.

I turned the amp off (disconnected remote wire) and keyed the radio. The sub still thumps with no power.

I then added 2 ferrite chokes onto the speaker wire from the amp to the sub as I thought the speaker wire may be acting as an antenna, but there was no difference.

I moved the ferrite chokes to the RCA cable input right where it enters the amp (so the RCA from the deck to amp) and it seemed to supress the thumps. I can only hear it a little bit, but not too much. I may add another ferrite choke to further supress it. I guess this seems to fix the problem as the RCA cable looks to be picking up RF from the amateur radio.

 

Id still try the different power source for the HU.. using a choke or a DCDC supply here can often fix noise problems..

using a choke on the RCA might not be the greatest as it could affect your sound... since this is happening on your sub amp only that might not matter...

But, why not try the choke on the base of the transmiter antenae ?? That should filter the sub harmonic being produced before it can get into the RCA/signal ground in the first place...


Aside from that- what kind of range do you have on that radio ? do you need a licence for it or what.. ???

[ February 13, 2005, 03:39 PM: Message edited by: Haunz ]

 

The range is pretty much dependant on your equipment. Usually you can access repeaters/towers which will further increase your range. There are actually contests to see how many contacts you can make and how far. You do need a license for it.

In Canada, you can get more info at www.rac.ca