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Dx88hl
New member
Username: Dx88hl
Post Number: 1
Registered: 1-2009
| | Posted on Saturday, January 31, 2009 - 10:04 pm: | 
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Great site. I tried searching and couldnt find anything on these subjects.
I run a 1.5W deadkey, 48W PEP, peaked/tuned Galaxy DX88HL on 11 meter AM with a RK56 mic through a TS DX500 and a single Wilson Silverload fiberglass antenna rated for 1000W. Output is around 500W.
I am using upgraded coax from a CB shop, I dont have the coax numbers handy, and have a Firestik Pro antenna mount bolted to the back center of the cab. The coax, 18 ft, comes into the cab through a grommet on the passenger side floor of the cab and over to the amp on the floor. I have a 9 ft jumper between the amp and the radio.
The power wires, 12 gauge, for the amp are running straight to the battery, + is fused there, and come into the cab through a grommet on the driver side floor of the cab and over to the amp on the floor.
Its all mounted in a 2006 Freightliner with a 100+ amp alt running 13.9 to 14.0 volts.
The SWR checked between the amp and antenna is 1.2 on 1 and 40 with no power to the amp, and 1.7 on 1 and 40 with the amp powered up.
The rig works great and I get lots of compliments on how clear and loud it is when the amp is off or on.
Problems;
1. There is a slight ringing noise in my talkback when I transmit with the amp on.
It makes no difference if the mic gain is almost the way up or almost all the way down. It also makes no difference how far the mic is from the speaker. (Both of the above may produce a squeal, but thats a different sound that what Im describing). The echo/reverb setting has no effect either. I even tried moving the external speaker to the other side of the cab. Still rings. If Im talking with the amp on, and the talkback is on, its ringing. Im told that the ringing doesnt transmit, so its only my external speaker thats making the noise.
2. My RK56 mic shocks/stings my lips when I talk on it with the amp on, and if my mouth touches the speaker grill. The longer I key down, the worse, hotter, it seems to get.
Ive been told that the metal grill on the mic is picking up my radio transmissions and placing ferrite beads on the mic cord will stop this from happening. Sound plausible?
If the mic is picking up the transmissions, is it possible that the external speaker is also picking it up and causing the ringing?
Thanks for any help.
Mick |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 4482
Registered: 7-2004
| | Posted on Sunday, February 01, 2009 - 11:31 am: |
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MIC BITE.....rf ground is BAD somewhere. just because your swr is GOOD does NOT mean there is not a problem with the RF GROUND somewhere...NOT DC/battery ground, though if there is too much/too many gound straps added, it can cause that problem.
There are some symptoms that may indicate the existence of station grounding problems. A list must include such obvious things as 'mic bite,' or a tingly feeling when touching metal while transmitting. A less obvious symptom is transmitted signal distortion due to RF feedback. RFI and TVI can often be traced to grounding problems. Here are a few other observations that were the result of the UNGROUND..... unfortunately, the remainder of that is not much more then a very long infomercial to purchase this guys stuff. the web address can't post here, so if you're interested in reading it all, let me know & i'll get you the address. |
Dx88hl
New member
Username: Dx88hl
Post Number: 2
Registered: 1-2009
| | Posted on Sunday, February 01, 2009 - 1:06 pm: |
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Thanks for the info Pat. I found it on Google by searching for the text.
So, I have an RF ground problem.
I did add a 10G ground wire to the amp power neg wire at the amp. That added ground wire bolts to the cab floor. No change.
The radio itself uses the ground wire in the truck wiring harness.
So, I have the radio grounded through the truck harness.
The Amp is grounded to the truck cab floor and to the battery. This also by default grounds it to the frame.
The truck has an aluminium cab, the antenna mount is bolted to the cab. Ive read that the aluminum cab may not provide a sufficient ground for the antenna mount. Ive also read that the aluminum cab should be a fine conductor since it is metal as opposed to fiberglass.
I could add a ground wire from the antenna mount to the frame. This wire would be 10G and would have to be about 6 to 8 feet long.
Alternately, I could run a short 10G ground wire from the cab to the frame to ensure that the cab is completely grounded and not isolated by rubber bushings from the frame.
Thanks for any help.
Mick |
Carolinagold
Member
Username: Carolinagold
Post Number: 94
Registered: 12-2002
| | Posted on Sunday, March 08, 2009 - 7:48 pm: |
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i had the same problem with a roof mount wilson 5000 a t/s 400v and a galaxy 44. mine was caused by rf feed back.
moved every thing around in the truck and made sure my coax wasnt ran across or under amp just where it hooks is the only place and made a flange mount for the t/s and made sure it had a good case ground. and boom no mare bit.
just my 2 cents
JAMES
CAROLINAGOLD
865
CEF#416
CCRC#2
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Kbar
New member
Username: Kbar
Post Number: 9
Registered: 2-2004
| | Posted on Monday, March 09, 2009 - 10:21 am: |
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I had the same problem in a 387 peterbuilt. I was running a sweet sixteen and a galaxy 88. This was my fix, move antenna to the back of the cab and ground to the frame. Then ground box and radio to the frame. No more bite and no more sqeul. I believe there is a after market bracket you can buy for a freightliner. I made mine out of 1/8th inche steel plate and bolted it to the stack mount. That will more than likely fix the problem. The only thing left is to ground your stereo to the frame. The only thing I didnt do. Hope this helps. |
Tech808
Moderator
Username: Tech808
Post Number: 16661
Registered: 8-2002
| | Posted on Monday, March 09, 2009 - 9:23 pm: |
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Dx88hl,
Copper Talk
» Ask The Tech
» Radio's Mobile
» CB noise Semi Truck
Posted on Tuesday, May 08, 2007 - 6:41 pm:
#1 ~ Ground Antenna's/Antenna Mounts DIRECT to the tractor frame.
#2 ~ Run a Ground wire from a case screw on Radio DIRECT to tractor frame.
#3 ~ Go DIRECT to batteries for power.
Works great on our Pete 379 and Kenworth L900 and NO NOISE or PROBLEMS.
DO NOT USE ANY FACTORY INSTALLED WIRING for your Power or Ground or Factory installed COAX or Antennas for your radio.
Also:
Copper Talk
» Subscriber (Preview)
» Articles
» Mobile Amplifier Installation Tips!
Hope this help's,
Lon ~ Tech808
N9CEF ~ EN50mk
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