| Author |
Message |
    
Biged
| | Posted on Monday, June 17, 2002 - 9:11 pm: | 
|
I got this from a websight. When I try it I will let everyone know how it works. I have this problem. Ever since I had the radio modified, my talkback is extremely loud. Here it goes:
]
This one is for CBer's who have talkback in their radios, and run an external speaker. If you get too much feedback, wrap the speaker wire around an old steel bolt, etc, forming a tight coil. Use at least twelve to fifteen turns of the speaker wire to do this. This trick has worked on dozens of my own customers' radios. |
DeadlyEyes
| | Posted on Monday, June 17, 2002 - 10:49 pm: |
|
Just thinking out loud....
Wouldn't it be better to put a volume taper veriable resistor with a gross adjustment reference resistor in line with one of the speaker leads leads?
input/---/reference variable resistor/----/audio taper volume control/------/speaker output
With the audio taper volume open full blast set the reference resistor to the loudest you want to hear (set the max volume) and use the manual operated audio taper to vary the speaker volume. |
ss8541
| | Posted on Monday, June 17, 2002 - 11:29 pm: |
|
they failed to mention that this only works if rf from the antenna is getting back into the radio through the external speaker wire (rf feedback). this forms a choke to rf, but will do -nothing- for a squeal that is caused by oscillations from too sensitive of a mic, or too high of a talk back level, or even both (audio feedback). rf feedback and audio feedback are 2 different monsters.
if you use a snap together ferrite square from rshack you only need about 6 turns compared to 12-15 used in the above example. it also needs to be as close to the radio as possible. if not the length between the radio and the coil is still acting as antenna picking up rf that is then brought right inside to the radios circuitry.
i noticed you said that the talkback is extremely loud since you had your radio modified. this is common when the amc is turned all the way up(or even almost all the way up) and the neg and pos peaks of the modulating -audio- are flattopping. the distortion here appears to make it extremely loud. proper adjustment of the amc will usually fix this problem, since the distortion is then removed. this also gives you some idea of how you sound on the rxing end. |
bullet/151 southern Indiana
| | Posted on Tuesday, June 18, 2002 - 3:26 am: |
|
hey ss
can i use this snap ring ferrite cores to kill the
rf going to my wifes touch lamp evrytime i use my amp i turn the damn thing on.. i usually go comando and slide in and turn the bulb a feww turns in the socket but at last shes on to my tactics.hehe
later bullet |
DeadlyEyes
| | Posted on Tuesday, June 18, 2002 - 10:04 pm: |
|
Now you have me a bit confused....
Hmmm, are we talking about RF feedback into the radio. Or are we talking about the special circut in a radio that lets you monitor the quality of the transmitted signal.
If we are talking about the second case then my original post stands. Some radios have a user feedback system that allows the user to listen to the signal as the receiving station would hear it. You can adjust your mike gain, compression, etc.
If we are taking about RF feeding back into the radio then do the Radio Shack core fix and ground the radio and all the equipment in the proper fashion. |
Copperfan
| | Posted on Wednesday, June 19, 2002 - 7:35 am: |
|
SS
I had this great TECH in N.C. set a SP1A in a Magnum Delta Force and the radio is loud according to the on air reports.
When using the talkback on the radio in the past (prior to the tech fixing it) it didnt take much to get feedback over the external speaker but now since the SP1A has been installed and the tech set the radio up the talkback actually works well.
I can actually hear myself (My wife says I just like to hear myself talk but thats another issue). Does the SP1A affect how oneself is heard on talkback also? |
jyd
| | Posted on Wednesday, June 19, 2002 - 12:54 pm: |
|
yeah,if you want talk back,the with the sp-1 it will squeel.it does effect the talk back |
Copperfan
| | Posted on Wednesday, June 19, 2002 - 6:02 pm: |
|
my radio doesnt squeel with the SP1A and talk back |
ss8541
| | Posted on Wednesday, June 19, 2002 - 9:29 pm: |
|
if i remember correctly that radio had the limiter clipped. it was replaced, and the key thing here is that modulation was 'properly' adjusted(with assymetrical am modulation - ppe modification). just replacing the limiter will not fix the problem. and what would you know, clean audio again. so the sp1a had nothing to do with with your talkback being clear and not squealing, it was the proper tuning. infact, since the sp1a is more sensitive than a stock or power mic it should have made the feedback worse if just added without tuning. also the sp1a works better in a properly adjusted radio, than in a limiter removed/wide open radio.
funny that you mention squealing -b4- radio was properly adjusted. like i was telling biged, this is the problem with most radios out there that squeal with talkback. there is a small percentage where the mic gain/circuit is too sensitive. adding a resistor to the audio line will fix this without any loss of modulation. some external speakers will also cause this, even with a properly adjusted radio and mic circuit.
rf feedback is usaully only present with an amp, or with an antenna that was not installed properly. |
Tech671
| | Posted on Wednesday, June 19, 2002 - 11:16 pm: |
|
Isn't the talk back in the Magnum radios totally independant of the transmit audio? If you turn the mike gain all the way down, it has no effect at all on the talkback. |
ss8541
| | Posted on Thursday, June 20, 2002 - 9:22 am: |
|
yes 671, i just came here to correct myself. i thought about that 1st thing this morning. i work with radios 12+hrs a day from business band to cb/ham. so its sometimes hard to keep each model straight in your head. from memory i am almost positve that the mic audio goes to the utb b4 the mic gain. so yes the mic gain does not effect the talkback audio here. and because of this, the sp1a(if installed after utb) or even improper amc adjustment will not cause radio to squeal like in the galaxies. i forgot at the time that i posted above, that his utb was also adjusted to a proper level while in for repair.
i had the galaxy radios in mind at the time i was posting since i see them much more often. the statements above are still true for those since modulation audio is what is sampled. |
ss8541
| | Posted on Thursday, June 20, 2002 - 10:21 pm: |
|
bullet, to answer your question; basically the part of the lamp you touch to make it come on/change brightness has a small electric current on it. by touching the lamp, you are causing an electrical disturbance that tells the light to change. if your rf is coming through the power cord, the ferrite choke will work. if the 'touch' part of the light is what is picking up the rf, then i suspect there is nothing you can do. my mom has the same light, and with my 500w mobile(very clean) it does the same thing if i am pulling up in my parents yard while talking. i work ssb mostly, so it looks like an xmas tree while i am modulating. |
bullet/151 southern Indiana
| | Posted on Monday, June 24, 2002 - 12:04 pm: |
|
thanks ss, i know what you mean...... |
|
