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another damm issue with this philly made 148

1iwilly

1iwilly

Sr. Member
Dec 7, 2008
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i need help with this 148 gtl that i bought to use it on my work truck. here is my issue

1st off i tested it on 3 other mobile and the same scenario. the radio sounds good, good power for a 148. i know you check reflect with no audio which in this case all 3 mobile + mine are ok but i like to see what it does when i apply audio if it goes forward i'm happy backward i see a problem. well only with this 148 when i check the reflect 2 watt at 600 watt dead key,on my 2x8 when i say audio this damm 148 pegs the 25 watt slug.with my other 2 cobra 29 it only goes up to about 5 watts of reflect radio was check and is fine as far as alignment any thing to worried about or what should i look for.:bdh::bdh::bdh:
 
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1iwilly said:
i need help with this 148 gtl that i bought to use it on my work truck. here is my issue

1st off i tested it on 3 other mobile and the same scenario. the radio sounds good, good power for a 148. i know you check reflect with no audio which in this case all 3 mobile + mine are ok but i like to see what it does when i apply audio if it goes forward i'm happy backward i see a problem. well only with this 148 when i check the reflect 2 watt at 600 watt dead key,on my 2x8 when i say audio this damm 148 pegs the 25 watt slug.with my other 2 cobra 29 it only goes up to about 5 watts of reflect radio was check and is fine as far as alignment any thing to worried about or what should i look for.:bdh::bdh::bdh:
Click to expand...


I assume that the average output with audio is swinging to 800+....that comes out to 3% reflect and there is nothing wrong with that.
Comp amps with built in drivers do strange things sometimes, it's the nature of the beast. My first 2x4 comp amp was a Davemade and the reflect was off the scale with the amp on.........changed the jumper from the amp to the meter from a 3 ft to a 9 ft and the reflect went back to less than 2%. Sounds strange and it makes the purists scream from the highest mountains but I never blew the amp up and I would hammer on the box until it was too hot to hold.
Then I bought a Worldwide MF-400 2x4 and the reflect was less than 1% no matter what length jumpers were used. I can't explain it but comp amps with built in drivers are flakey and these amps were just designed to be used as drivers for larger amps anyhow.
The radio should have no effect on the reflect unless it is hitting a different wattage level that the amp isn't tuned good for.
The first amp I owned was a Gray 300 4 stage old school box......low and medium stage the swr was 3-1+ but the high and max stage was perfect. Certain amps will show more reflect at various power output levels, crazy yes!
********************Disclaimer*********************
I AM NO EXPERT!
 
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thanks but i'm not complaining about my amp just about the 148 like i stated my other cobra radios 29 ltd classic don't give me that problem.?/?




psycho said:
I assume that the average output with audio is swinging to 800+....that comes out to 3% reflect and there is nothing wrong with that.
Comp amps with built in drivers do strange things sometimes, it's the nature of the beast. My first 2x4 comp amp was a Davemade and the reflect was off the scale with the amp on.........changed the jumper from the amp to the meter from a 3 ft to a 9 ft and the reflect went back to less than 2%. Sounds strange and it makes the purists scream from the highest mountains but I never blew the amp up and I would hammer on the box until it was too hot to hold.
Then I bought a Worldwide MF-400 2x4 and the reflect was less than 1% no matter what length jumpers were used. I can't explain it but comp amps with built in drivers are flakey and these amps were just designed to be used as drivers for larger amps anyhow.
The radio should have no effect on the reflect unless it is hitting a different wattage level that the amp isn't tuned good for.
The first amp I owned was a Gray 300 4 stage old school box......low and medium stage the swr was 3-1+ but the high and max stage was perfect. Certain amps will show more reflect at various power output levels, crazy yes!
********************Disclaimer*********************
I AM NO EXPERT!
Click to expand...
 
1iwilly said:
thanks but i'm not complaining about my amp just about the 148 like i stated my other cobra radios 29 ltd classic don't give me that problem.?/?
Click to expand...


If the swr is fine with the amp off, then higher with the amp on it's a minor tuning glitch in the amp. I'll bet the swr with the amp off using all the radios is the same.
 
ok lets try it this way 1st- the amp is fine 2nd- swr are fine . i'm not complaining about an amp issue or a swr issue i'm trying to find out if anybody else with a 148 has seen this kind of problem with every other radio it is fine but not with the 148
i want to fix the issue because i like the radio better than the 29 classic



psycho said:
If the swr is fine with the amp off, then higher with the amp on it's a minor tuning glitch in the amp. I'll bet the swr with the amp off using all the radios is the same.
Click to expand...
 
Jose, I've been telling you for a year it's the amp and not the radio. Please believe me when I say your amp is not running stable. I understand it does not do this with another radio but it still does not indicate a radio problem. Someplace in this forum is a tread called "High SWR with more power added" it explains your problem well. Most likely RF is feeding back from the final stage into the driver inside that amp. Could be on the DC line or direct RF coupling. RF bypassing on the DC line, copper shielding between stages, or a tuned input circuit on the driver and or final may solve your problem. This assumes you already have negative feedback installed.
 
donald we been thru this amp with no fault found yes all the feedback circuits are in.if the amp was acting up would it mess with the electronics in my van xm radio no issues when running amp dvd no issues when amp is on
you have heard how clean the audio sounds when i'm out there.i even did a bleed over test only bleeds 9 channels up or down compare to you friends 16 pill that bleeds 120 channels. hehehehe



Shockwave said:
Jose, I've been telling you for a year it's the amp and not the radio. Please believe me when I say your amp is not running stable. I understand it does not do this with another radio but it still does not indicate a radio problem. Someplace in this forum is a tread called "High SWR with more power added" it explains your problem well. Most likely RF is feeding back from the final stage into the driver inside that amp. Could be on the DC line or direct RF coupling. RF bypassing on the DC line, copper shielding between stages, or a tuned input circuit on the driver and or final may solve your problem. This assumes you already have negative feedback installed.
Click to expand...
 
1iwilly said:
ok lets try it this way 1st- the amp is fine 2nd- swr are fine . i'm not complaining about an amp issue or a swr issue i'm trying to find out if anybody else with a 148 has seen this kind of problem with every other radio it is fine but not with the 148
i want to fix the issue because i like the radio better than the 29 classic
Click to expand...


Bypass the 2 pill driver section in the amp and use an external driver........problem solved permanently. It's impossible for a particular radio to show more reflect than another 2 radios unless the 148 is off frequency by 80 channels.....not likely.
If you think the radio has a problem, give me your paypal info and I'll give you $50 for it and put it in my pickup.
 
well here is an update after talking to another amp builder in florida he said a guy came in with the same issue he didn't beleive it so he went and look in the guys mobilee yea reflect was crazy then he ask the guy did he have a different radio another 148 done=modified by the same tech well the problem
is the tech use the galaxy trick to get a few more watts with the diode resistor mod from r228 i belive it is. will have to look at mine later on tonight.
 
Did you buy the radio new? If not then someone probably turned up the carrier and that would make it swing backwards. You need to open it up and turn it back down to 4 watts or less to get the forward swing. Talking average power here, which is what the swr meter uses. It will swing forward on pep even if it is set to high. It is not the radios fault, but who ever cranked it up too high.
 
1iwilly said:
well here is an update after talking to another amp builder in florida he said a guy came in with the same issue he didn't beleive it so he went and look in the guys mobilee yea reflect was crazy then he ask the guy did he have a different radio another 148 done=modified by the same tech well the problem
is the tech use the galaxy trick to get a few more watts with the diode resistor mod from r228 i belive it is. will have to look at mine later on tonight.
Click to expand...


Don't any of the techs you use know what they are doing? It's not the radio and you have been told that by everyone on this thread. If you aren't willing to listen to advice, don't ask for it.
 

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