| Author |
Message |
    
Bigfoot
Junior Member
Username: Bigfoot
Post Number: 46
Registered: 12-2001
| | Posted on Saturday, November 11, 2006 - 8:54 am: | 
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Ok, I have a 1994 148, in mint condition, the radio works flawlessly. I have a problem with SSB when I run my amp. The radio sounds great on ssb without the amp, but when I transmit through my amp I sound like white noise to anyone listining. Am sounds fine. I tried my 2510 through the same amp (4 pill) and no problem. I put the amp on my base radio with a power=supply, and no problem. So what is going on????????????? The radio has both TR-24 and R-131 intact. Adjusting mic gain lowers the drive on ssb, but it still sounds like white noise through the amp. It sounds great on ssb without the amp. My guess is a bias mismatch, but why would my other radios work so well with the same amp/coax/antenna setup? Any info would be helpful!
Thanx.................... |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2255
Registered: 9-2004
| | Posted on Saturday, November 11, 2006 - 11:51 pm: |
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wow, that is a stumper!
sounds like you've checked everything.
no ideas for you yet, but i wanted you to know people are reading your thread.
good luck,
c'mon techs.
matt |
Bigfoot
Junior Member
Username: Bigfoot
Post Number: 47
Registered: 12-2001
| | Posted on Sunday, November 12, 2006 - 6:38 am: |
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Thanks Matt, your input has always been positive and helpful! |
Hotwire
Senior Member
Username: Hotwire
Post Number: 2008
Registered: 1-2005
| | Posted on Sunday, November 12, 2006 - 1:14 pm: |
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Has the radios transmitter been alighned by a professional tech and the ssb modulation adjusted for the amp?
I have a Cobra 148 that was tuned by a pro for maximum barefoot operation. I have tried it on my 4 pill Texas Star and it sounds awful like yours is doing.
The particular tune up he did was his own "supertune" for barefoot operation. Really cranks up the modulation and I have been told, when running a smaller amp{2 pill that did sound fair} that I sound overdriven at just 20 watts PEP. Its just that my 4 pill is refusing to work well.
Have you tried a different mic?
Maybe you need to find a good tech and just have the radio matched up to the amp using all the appropriate tools,actually look at the wave form on a scope. That would be a start. If the waveform is bad from the radio(undetectable by the ear) then its gonna be even worse out the amp and very noticeable.
Just sounds like to me you need a good tuneup. good luck
Kenny
cef491 |
Bigfoot
Junior Member
Username: Bigfoot
Post Number: 48
Registered: 12-2001
| | Posted on Tuesday, November 14, 2006 - 5:03 pm: |
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Well the radio has never been modified, I did set the AM power to 2 watts carrier, and turned the modulation to 100%. I adjusted L22 for center slot on clairfier. Like I say it works flawlessly without the amp inline. Anyway I put my 2510 in the car and no problems, I brought the 148 in the house put it on my power-supply and it works fine on my small base amp........... |
Yankee
Senior Member
Username: Yankee
Post Number: 1363
Registered: 7-2003
| | Posted on Tuesday, November 14, 2006 - 8:30 pm: |
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Man, this is a real stumper. You say it sounds great on a smaller amp. This is only a guess, possible you don't have enough sideband drive to fully kick the four pill, with TR-24 and R-131 still in the circuit. It's possible that a good professional tune up, at a well known shop, not a truck stop, might help.
Remember the radio is now 12 years old and circuit components can change value over a period of years. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2264
Registered: 9-2004
| | Posted on Tuesday, November 14, 2006 - 8:37 pm: |
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do you sound like white noise in USB and LSB or just in one mode?
matt |
Bigfoot
Junior Member
Username: Bigfoot
Post Number: 49
Registered: 12-2001
| | Posted on Wednesday, November 15, 2006 - 4:57 pm: |
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Both upper and lower..................And the 4 pill is a low-drive. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2271
Registered: 9-2004
| | Posted on Wednesday, November 15, 2006 - 7:05 pm: |
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i think yankee may have something there.
what is the model and make of the amp?
what kind of base rig are you running, and how many watts does it put out on SSB?
matt |
Bigfoot
Member
Username: Bigfoot
Post Number: 51
Registered: 12-2001
| | Posted on Friday, November 17, 2006 - 4:47 pm: |
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The amp is a Silver Streak 400 (4 MRF 454 Finals). The radio works fine on my 2 pill. When I use my 2510 on the Silver Streak, I have the ssb peak adjusted to 12 watts. I use a RK 54 non-amplified mic. My base amp is a GB 200 (2 mrf 454 finals)with a Washington base with 12 watts ssb peak. All equipment works perfectly, except for the 148/ Silver Streak / mobile combo. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2279
Registered: 9-2004
| | Posted on Saturday, November 18, 2006 - 11:35 pm: |
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i was hoping to find some info on whatever amp you listed, but i cant find anything on the silver streak 400.
here's the only thing i can think of right now.
maybe the 148 has been modified in such a way that the output impedance is not exactly 50 ohms, and this mismatch is not noticable on any amp but the silver streak 400.
see, the output of the radio is only 50ohms with 4 watts out.
if the radio was extensively modified, then it may not be 50 anymore.
one thing to try is to re bias the final and driver in the 148 gtl.
set them for 40 and 80mA.
if that does not work, try 35mA and 70mA (35 for driver, 70 for final)
to learn how to do this, check this thread:
it is towards the end.
http://www.copperelectronics.com/cgi-bin/discus4/show.cgi?tpc=34&post=113535#POST113535
good luck,
matt |
