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Can I Install a MRF455 In A Cobra 29 ?

pimphand442

Member
Jun 11, 2011
72
0
16
35
i have several amp transistors and was wondering is there anyway to install mrf455 or s2c2290 inside the radio just want to have sumthing to drive my palomar hd 600.....

i had a cobra 148 and it dk at 8 watts and swing to 13 and with amp on it was dk at 100watts and swing to 500watts avg.

I got a cobra 29 ltd classic and it dk at 2.5 watts and swings to 5 maxx my swr is a 1:2 with both radios and ive put a 1969 final in it and a 2166 driver and changed a cap or two and still same 2.5dk and 5 watts maxx

with amp on it dk at 30 watts and swings to a 100 wats avg maxx any help would be appriciated thanks.
 

wavrider

W9WDX Amateur Radio Club Member
Jun 2, 2009
3,393
1,246
173
Cobra has a problem, those are swingin rigs, get it fixed and it will be nice in front of the amp.

As far as your question? Why go through the hassle, re engineering circuits, just buy a dual mosfet export and call it done.
 

Se7en

Well-Known Member
Jun 27, 2010
4,576
216
73
Ca
Cobra has a problem, those are swingin rigs, get it fixed and it will be nice in front of the amp.

As far as your question? Why go through the hassle, re engineering circuits, just buy a dual mosfet export and call it done.

i see nothing wrong with what the guy wants to do. have you seen the price tags on dual final radios? + most of them are JUNKCHINA anyways:closedeyes:
it is very do-able if you have the knowledge and proper tools.
 

9C1Driver

Sr. Member
Aug 13, 2008
3,584
1,468
173
i have several amp transistors and was wondering is there anyway to install mrf455 or s2c2290 inside the radio just want to have sumthing to drive my palomar hd 600.....

i had a cobra 148 and it dk at 8 watts and swing to 13 and with amp on it was dk at 100watts and swing to 500watts avg.

I got a cobra 29 ltd classic and it dk at 2.5 watts and swings to 5 maxx my swr is a 1:2 with both radios and ive put a 1969 final in it and a 2166 driver and changed a cap or two and still same 2.5dk and 5 watts maxx

with amp on it dk at 30 watts and swings to a 100 wats avg maxx any help would be appriciated thanks.


There are plenty of custom mods that can be done to a radio. Check out this guy, Site Disclaimer - Custom CB radios


That said your Palomar 600HD is not the best amp to be pushing hard. A radio that dead keys 3-4 watts and swing 20-25 should drive it just fine.

If you really want to do a mod I had Sparky cb do up a Cobra 25 with an IRF520 mosfet final. It did 30-35 watts from a 2 watt carrier. Had a receive mod and an audio kick kit as well. It was a butt kicker.

Last, you really have to know what your doing when you do these custom mods. You can't just solder crap into a radio and tada it works great. Gotta have the right gear and know how. Doug at custom has a 2290 mod on his site and he had to remove and re engineer a whole pile of parts.
 

9C1Driver

Sr. Member
Aug 13, 2008
3,584
1,468
173
I think you need a new meter as well. There is no way a dead key of 8 watts with only 13 watts peak into a Palomar 600 will give you 100 swinging 500. You will be at something like 150-175 watts and if your lucky maybe 300 peak. The dead key input is too high for that amp and the the peak swing is too low. A 3-4 watt carrier and 25-30 watts peak will drive it very well.
 

9C1Driver

Sr. Member
Aug 13, 2008
3,584
1,468
173
Cobra has a problem, those are swingin rigs, get it fixed and it will be nice in front of the amp.

As far as your question? Why go through the hassle, re engineering circuits, just buy a dual mosfet export and call it done.

No, thats not correct at all. The Cobra 148 and Uniden Grant xl radio are very much low drive radio's. When properly tuned they peak on AM at 12-16 watts and 15-18 watts PEP on SSB.
 

pimphand442

Member
Jun 11, 2011
72
0
16
35
i tried 4 different meters all the same my galaxy 99 will dk at 8 and swing to 20 i would just like to use this 29 for my mobile but its not pushin this 600hd like my other radio i know its capable of it but cant get radio up in power
 

137

Member
Jun 6, 2011
54
1
18
Middle TN
I have a buddy of mine that does these types of mods all the time, adding extra finals of all types to cobras, he has really gotten into adding and extra mosfet in the 29 lx's with some good results. He's added pills, mostly 1446's but the cost of them has had him to move away from it as of late. He goes by Sign Painter, he runs a CB shob here in TN.
 

9C1Driver

Sr. Member
Aug 13, 2008
3,584
1,468
173
i tried 4 different meters all the same my galaxy 99 will dk at 8 and swing to 20 i would just like to use this 29 for my mobile but its not pushin this 600hd like my other radio i know its capable of it but cant get radio up in power


What finals does the Palomar 600 have and in what configuration. I hope it's a straight 4 pill but I know they made a Palomar/Gray/Boomer that was a 1x4 with all 1446 finals.
 

wavrider

W9WDX Amateur Radio Club Member
Jun 2, 2009
3,393
1,246
173
No, thats not correct at all. The Cobra 148 and Uniden Grant xl radio are very much low drive radio's. When properly tuned they peak on AM at 12-16 watts and 15-18 watts PEP on SSB.

OP states his peaks 5 watts 50% less than it should if properly tuned.

So a good peak and tweak is not the correct thing to have done? Or if indeed the radio only does 5 watts then it needs repaired then peaked and tweaked.

OP is mentioning the Cobra 29 not the 148 :pop:
 
Last edited:

pimphand442

Member
Jun 11, 2011
72
0
16
35
Well i have too i have a palomar 600 hd and i have a boomer deluxe 600 hd and the palomar 600 hd is a straight 4 pill 2879's

and the boomer 600 deluxe hd is a 1x4 and has 5 sd1446's
 

psycho

Running a special on our rooms!
Aug 25, 2006
3,435
1,294
173
Floriduh
i have several amp transistors and was wondering is there anyway to install mrf455 or s2c2290 inside the radio just want to have sumthing to drive my palomar hd 600.....

i had a cobra 148 and it dk at 8 watts and swing to 13 and with amp on it was dk at 100watts and swing to 500watts avg.

I got a cobra 29 ltd classic and it dk at 2.5 watts and swings to 5 maxx my swr is a 1:2 with both radios and ive put a 1969 final in it and a 2166 driver and changed a cap or two and still same 2.5dk and 5 watts maxx

with amp on it dk at 30 watts and swings to a 100 wats avg maxx any help would be appriciated thanks.



Why don't you have someone who knows what they are doing tune the radio.
As far as putting a MRF455 into a Cobra 148, that is just too silly for words.
 

9C1Driver

Sr. Member
Aug 13, 2008
3,584
1,468
173
I have to agree. If you want to play around with mods for the hobby of it that's fine. Get a 20 dollar Cobra 25, go to cbtricks.com and have at it. If you have some equipment and can solder you can have some fun.

If you want a radio that performs and sounds good send your radio to a good tech and then leave the covers on it and have fun talking. Your one radio that only swings 5 watts needs serious help. Likewise a Cobra 148 that dead keys 8 watts and swings 13 is not set up right either.
 

slowpoke315

Member
Nov 20, 2014
3
0
11
43
I know this thread is old but I'm doing anyway. Putting anything into a cobra/uniden more than 20w avg power with transmit and will probably do about 50% efc that's bad. Next most transformer modulated radio's can not keep up with such a drain on the audio transformer it self. Next these type of radio's sample the rx to keepthe radio on freq, this would would kind of wideband the radio while it lasted. Next the heatsink for the final is also for the driver not good, asany transistor gets hotter than their design allows they degrade would work while it lasted but not for long. The only way to add any such final is on a stinger board, which can taken from any small amp and mounted on a flat peice of aluminum. So in short do not try to put anything in a cobra/uniden 29,25,78,68 that does not come in 220 case you can try a 247 case but I have done it, the driver won't last nor the transformer, or the audio ic something will fail.
 

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