| Author |
Message |
    
Twa77
| | Posted on Monday, February 03, 2003 - 11:06 pm: | 
|
i have a imax 2000 mounted on my roof. i have been coming through the neighbors television. the antenna is grounded to an 8 foot ground rod. i also added the gpk. i think the gpk did reduce the amount of tvi but it still exists. the antenna is 15 foot over my roof. anybody have any experience with imax and tvi. any help would be appreciated. |
Tech833
| | Posted on Tuesday, February 04, 2003 - 11:54 am: |
|
The problem could be spurious and/or harmonic transmissions from your radio or could be the TV itself.
Has your radio been modified or 'tuned up'? What make/model/age is your neighbor's TV? Have you tried a low pass filter on your radio or a high pass filter on the neighbor's TV set? |
Twa77
| | Posted on Tuesday, February 04, 2003 - 1:24 pm: |
|
i have not tried a low pass filter. what is a good one and where can you get it. |
Alsworld
| | Posted on Tuesday, February 04, 2003 - 8:40 am: |
|
Oh yeah Twa77,
now this one is something I know about. Lets get the facts:
1) Do you use an Amplifier? If you do, does it happen also when running without power?
2) Power mic or radio with adjustable mic gain?
3) Does the neighbor have cable?/ TV antenna?/ Sattelite dish? Any particular channels worse than the other?
4) Do you have a low pass filter inline?
5) What type of radio and how has it been modified? Limiter cut?
Throw some answers here and we'll work it out. I also have the IMAX 2000 w/GPK and have caused TVI but I was able to clean it up (except non-shielded computer speakers). Various options to choose from but first we need to see exactly what's causing it. Bruce is a tremendous amount of help as well and helped me learn about TVI and really solved my problem. If he jumps in on this thread, listen up! 
Alsworld |
Twa77
| | Posted on Wednesday, February 05, 2003 - 10:22 am: |
|
alsword.
no i do not use an amplifier. i am running a 2510 with a 636 noise cancelling mic. the neighbors have cable tv and it doesn't matter what channel they are on. i do not currently have a low pass filter inline. my radio has not had the limiter cut. it has been aligned by a reputable tech and has gotten exellent reports, referred as "smooth audio. one other thing, i do most of my talking on lower sideband , although it happens on am as well. thanks
tony |
Alsworld
| | Posted on Wednesday, February 05, 2003 - 3:54 pm: |
|
Twa77,
this one is interesting. The 2510 is an excellent radio (a super SSB talker!), and if I'm right, the 636 is a non-power mic. Running barefoot should not cause problems, especially with cable TV systems. That leads me to believe his TV isn't filtered worth a darn. However, these things happen and being you are not running an amplifier, should be an easy fix. So, here are my suggestions:
1) Double check all your coax connections for security. A loose connection could leak.
2) Buy your neighbor a high pass filter. About $7 and it screws in at the back of his TV between the cable and television coax. Now if it is coming over more than one TV in his house, he needs to call the cable company as there is a leak in his system somewhere. That would not be your fault nor your responsibility to fix.
3) Buy yourself a low pass filter. This goes between your radio and antenna so you will need a short coax jumper to hook it up. It reduces or eliminates harmonics produced by the radio (which cause interference).
I would start by doing #1 & #2 above first. #3 is always a good idea anyway but a little more expensive.
Do you interfere with anything at your own home?
What is the age of your coax?
Feel free to e-mail me at ALSWORLD@att.net and I will help you on where to find these items. I believe Copper sells low pass filters but I'm not sure about high pass filters. The cheaper the fix the better.
Legally, running this setup you probably could tell him to pack sand but it's not real neighborly. You should be able to help him fix it fairly easy.
Alsworld |
Tech833
| | Posted on Wednesday, February 05, 2003 - 10:40 pm: |
|
Since you are interfering with the TV regardless of the channel it is tuned to, there are some things that come to mind.
*Your signal could be entering the set through the case. The TV chassis should be grounded and you may need to invest in some shielding spray to shield the case of the TV (or replace the TV).
*Your signal may be entering the cable box. This is very common and is corrected by grounding and shielding.
*Your signal may be entering through the AC cord. This can be solved by using ferrites or filtered power strips to plug the TV in to.
Either way, the 'tune up' could be suspect too. Unless your reputable dealer has examined your radio's output on a spectrum analyzer, they cannot verify if it is clean or not. Clean sounding audio can come from a dirty radio too. I have NEVER seen a CB radio shop that has and uses a spectrum analyzer in the tune up process. It boggles my mind. In my field, unless you use a spectrum analyzer on the transmitter during tune up, you can't run it. In fact, harmonics and spurs are required to be measured on a regular basis to ensure compliance. CBers would find themselves in a better public view if they did the same. |
Twa77
| | Posted on Thursday, February 06, 2003 - 5:12 pm: |
|
the only thing it interfers with my house is my tv. but it only does when i am going through the vcr. if i turn off the vcr i get absolutely no interference. before i got the gpk it would interfere with a boom box that i had in the radio room. since i put up the gpk it doesn't bother that anymore.i am running mini 8 coax from copper that i put up last winter.. would getting bigger coax help? i would like to thank everyone for helping. all your input is appreciated. thanks
tony |
Tech833
| | Posted on Thursday, February 06, 2003 - 10:00 pm: |
|
The coax will not change a thing. You need to address the real problem. |
Alsworld
| | Posted on Thursday, February 06, 2003 - 10:40 pm: |
|
Twa77,
I tried responding to your e-mail but it got returned. Coppers does stock various low pass filters. I'll wait and see if the e-mail does go through.
Tech833, what is your best recommendation for a typical CB'er to research the cause and affects of TVI? I have some Ham books, and will receive the ARRL antenna handbook next month, but what are our learning options available without studying for your job . If there are some better learning tools out there, I'm all ears.
Alsworld |
Ironmask
| | Posted on Friday, February 07, 2003 - 9:25 pm: |
|
Alsworld and all,
ARRL publishes a TVI handbook that I have used and highly recommend. It has chapters that address each type of TVI and ways to address the specific problem. Example of topics: Television, vcr, Phone, computer, etc.
It can be purchased on line at ARRL's site |
Alsworld
| | Posted on Friday, February 07, 2003 - 10:17 pm: |
|
Outstanding! Thanks Ironmask. I'll add it along with the antenna book. Looking into some homemade antennas in the future. Might shoot for a quad but will get the book and surf for something that looks fun. Dipoles have been easy to learn.
Thanks again Ironmask.
Twa77, did you get the e-mail? I sent it to that specific address you gave me, ***@yahoo.com.
Alsworld |
Twa77
| | Posted on Friday, February 07, 2003 - 10:17 pm: |
|
i purCHASED A TVI LOW PASS FILTER WHEN IT COMES I'LL LET YOU KNOW WHAT HAPPENS. ONCE AGAIN THANKS EVERYBODY FOR THE HELP.
TONY |
Twa77
| | Posted on Friday, February 07, 2003 - 10:17 pm: |
|
i purCHASED A TVI LOW PASS FILTER WHEN IT COMES I'LL LET YOU KNOW WHAT HAPPENS. ONCE AGAIN THANKS EVERYBODY FOR THE HELP.
TONY |
Tech833
| | Posted on Saturday, February 08, 2003 - 12:08 pm: |
|
Ironmask, The ARRL TVI book is indeed a great place to learn about TVI prevention, good call.
After you get through the ARRL book, pick up a Decibel Products catalog at your local professional radio dealer and read the back several pages in it. That picks up where the ARRL book leaves off, and it is free. |
N8fgb
| | Posted on Tuesday, February 18, 2003 - 6:06 pm: |
|
Cable TV operators are notorius for leaks.If you have a programmalbe scanner,punch in 145.25 mhz,this is cable channel 18'video.If there is a fairly strong signal there,then it is up the the cable company to fix it.You want to be there and show the cable guy the signal,he will always blme you,not the system.
Rich |
Twa77
| | Posted on Tuesday, February 18, 2003 - 8:00 pm: |
|
hey guys as far as i know the problem is fixed. i am going to try that scanner trick just for kicks.thanks for all the great input. |
|
