How many have done cobra final upgrade here , does it work

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SinStp
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How many have done cobra final upgrade here , does it work

Post by SinStp » Friday 22nd Aug 2008, 17:36

Just curious if it is woth it. Loks like alot of guys have had problems. Mine is new, couple months old anyway. Would rather not mess it up

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Post by timrim » Saturday 23rd Aug 2008, 5:12

If you are talking about the MOSFET upgrade, it works very well.

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Post by SinStp » Saturday 23rd Aug 2008, 12:31

Yes , the mosfet upgrade. just looks like a lot of guys have had problems. Im sure it has alot to do with the quality of the parts and the installer. Is any body running a fan to help with the extra heat ? Or is there not enough to worry about

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cobra finals

Post by WARLORD136 » Monday 25th Aug 2008, 8:57

i'm not sure of the mosfets, i'm old school. i have used a 2sc1969, in these radios and they work well. there are some left out there, but beware! some people have made a stamp with the mitsubishi logo and are stamping cb-20's with this label. the 69's do a very good job, as with any part, it's only as good as the person who installs & tunes it. i don't run internal speakers, so if i encounter an overheat problem, i install a 1x1 inch 12 volt fan in the spot where the speaker was. good luck.
WARLORD 136 <> some people are affraid of the dark---some are affraid to leave it<>

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Post by Dodgem250 » Tuesday 16th Sep 2008, 10:32

The radios, like the cobra 29, is NOT DESIGNED TO HANDLE A MOSFET FINAL. Good lord guys, when are you all gonna get over the fact that it doesn't work?

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Post by timrim » Tuesday 16th Sep 2008, 12:05

If it's done properly it does indeed work! I have done hundreds of them in Cobra radios, every model 25 and 29 from the XLR version to present time.

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Post by Dodgem250 » Tuesday 16th Sep 2008, 12:56

How about you send me one of your radios to test on MY meters. I have my meters recalibrated every 4 months by their makers, regardless if I feel they need it or not. Care to take that challenge? This would not be the first... or tenth time I've made this offer to someone in the past 30 years, so... let's do it, no one has yet.

And please don't tell me your meter reads differently than mine, that would make your meters' reading false.

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Post by timrim » Tuesday 16th Sep 2008, 20:01

It has absolutely nothing to do with what brand or model meter you are using, or even if you calibrate your meters every day on a lab standard. Proper installation of a MOSFET will increase your power output.

Bottom line is this: If you install a MOSFET and do not see a big improvement in wattage output, you are doing something wrong, possibly one or more the reasons below:

1-. Using inferior quality parts... Know your source!
2-. Not properly retuning radio after installation
3.- Not changing coupling caps when required
4.- Not using the proper companion bias chip
5.- Not retuning your radio on a 50 ohm (non inductive) dummy load

The above 5 reasons are a few of the most common reason for failing to get good power output after installation of the MOSFET.

If you continue to experience problems with power output, In the long run it may be better to have an experienced technician install and tune it for you, that way you can be sure it will be done right.

TIP: Always have a schematic of any radio that you wish to put MOSFET(s) in.

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Post by Dodgem250 » Tuesday 16th Sep 2008, 21:50

Well, the main issue here is, MosFets are NOT designed for use in standard CB radios, the list of excuses why it didn't work can go on and on until the next ice age comes around, but, as long as the tech got paid for what he did, oh well right, I hear that a lot, and I see a lot of cobra units on ebay, with blown MosFet upgrades, it doesn't have to work... as long as it's in there, right?

I buy 2078, 2166, 1969 finals by the bags full, they are hard to find, but, when you find them, USE THEM !

Anyway, the meter has everything to do with it, that's the dividing line between honest tech repairs and lies, I see a lot of lies, especially the one where some repair guru said, "Yep, she's doing about 48 watts right now".


Well, I know where the calibration screws are in my meters and in 2 seconds I can make a radio with a stock 2078 do 75 watts, it all depends on if the tech wants to stay in business or not, I've been doing this for 30 years, so...

But, I do enjoy reading some of the hilarious posts on these forums, and I love the guys who read this stuff and then try it... It gives me something to repair later on.

Thanks,
Dodgem
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Post by timrim » Tuesday 16th Sep 2008, 22:48

MosFets are NOT designed for use in standard CB radios
Yes, they are! The design engineers at Ranger and Galaxy are both using them, and I am not talking just the 10 meter radios either, The Galaxy DX929 DX939 DX949 DX959 DX979 use them. Texas Ranger uses them in all their CB models. I don't have the heart to tell the engineers at Galaxy and Ranger that MOSFETS are not designed to work in their radios because you said so. Should they recall all of the ones that made it to market?

I come here because there are a lot of nice, knowledgeable people that really enjoy helping other people, I don't laugh at people, they come here in search of help, and if I am able to help them, I am more than happy to do so. I expect nothing in return.

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Post by Dodgem250 » Wednesday 17th Sep 2008, 8:54

The Galaxy DX929 DX939 DX949 DX959 DX979 use them. Texas Ranger uses them in all their CB models.

You just said it yourself. I guess I just made my point, since you went directly to export boards, and not the non-export Cobra / Uniden boards, and this is the reason why I stated the fact that the MosFets are not designed for standard CB radios.

Thank you, it's been fun, and this is why I only come to these boards on rare occassions. I let others come to them and then... they come to me. LOL!

BUMP-BUMP !
Dodgem

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Post by timrim » Wednesday 17th Sep 2008, 11:23

Ummm, which of the above radios ARE export radios and NOT standard CB's?

Answer: None of them! They are all standard CB Radios! :lol:


Please think before you stick your foot in your mouth.
I stand by every word that I said!
Please don't bother to reply, I will no longer feed the trolls here.

Getting back on topic, If anyone installed the MOSFET(s) and are having trouble, I will offer whatever help that I can.

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Post by ramblingman » Wednesday 17th Sep 2008, 12:08

He is probably a ham-head..You know they all know
more that any of us guys that use and repair cb..They think
just because they take and pass that simple ass little test..
They know it all..I could pass that simple little ham test
with both eyes shut..But i dont care to talk to those
big ego know it alls..He needs to get a life..And if he cant
offer anything positive here,To stay the hell out.

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Post by Dodgem250 » Wednesday 17th Sep 2008, 13:08

Well, first of all, I don't know that much about HAM radio, and don't really care to. Secondly, I'm sorry if I have blown someones cover, but, what the heck, I know what I know and that's a lot compared to what some people want others to think.

I also have plenty of a life, and I have plenty of useful information to offer and plenty of positive things to say regarding the CB radio hobby, just have to have some others who know the facts and not what they dreamed up or false theories the read somewhere else, or some scheme to make money off of other peoples lack of knowledge.

But, let's be honest, we all know for a fact that Galaxy and Ranger units are built on Export unit board designs, not "standard" (ie: Cobra 29) boards, what we'll call actual CB radio and not Export CB Radio, which IS a export unit, it just lacks a lot of the Export features, so, it can be considered a "standard" cb radio, but, it just ain't so, it's an Export design, regardless. I can most certainly agree with the statements that the MosFet final will work in the above mentioned radios, the above mentioned boards are DESIGNED TO ACCEPT SUCH AN UPGRADE, is this such a hard concept to grasp? The Cobra 29, for example, is not. This is why everybody blows up their radios trying to do what the last guy said he did.
So, I always say< ship me the radio and let me see it for myself, no one has ever accepted the challenge. I'm not going to steal your precious radio, I am easy to find and easy to track down, I have more public contact information than any radio repair guy you'll ever know, why? 'cause I know.

That's enough for me, think about it, I got work to do here, see ya bye!

Thanks,
Dodgem

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And now to answer sinstp's question...

Don't do it !
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Post by SinStp » Thursday 18th Sep 2008, 14:09

Correction , I didnt blow up my radio. It nows swings low 40's , thanks to timrimm , and I appreciate the hell out of guys like timrim and ramblingman helping me out and a big part of this hobby is tinkering around with these radios. I would rather blow up a $75.00 radio tweaking it and having fun with it than taking it to an arrogant douchebag like you . Guys like you are the reason why people dont take thier radios to know-it-all techs . These guys help people out and ask nothing in return and you and your ego show up talking out your rump. Why would you even post here ? Do you need attention ?

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Post by speedracer6g » Sunday 21st Sep 2008, 8:11

Hi guys thought i would chime in on this discussion. heres my 5 cents worth of information. Bipolars have a lower gain than mosfets that is not new news to anybody. That is a plus compaired to bipolars. I will use either one but my favorite is the mosfet because you do get more power out of it compared to mosfets due to the higher gian. Put one on a b&k transistor analyzer and look for yourself. I have a Bird 43p meter and that is industry standard and i get more wattage out of the radios here in the shop with it and bird meters dont lie not for $600 that is for sure. when i worked for motorolla that is what we used and pretty much what anybody else uses too. so what meter is this guy using a Dosy ha ha. you can calibrate them all day and they are not linear anyways. I also want to konw that if mosfets are junk how come all the new radio from ranger are using them. Oh thats right all those engineers are idiots i forgot. Im out

Mike
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RF tech.
not a garage tech. :lol:

I am captian screwdriver and i love bipolars so much i want to marry them ha ha :lol: sorry i had to add that.

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Post by Dodgem250 » Sunday 21st Sep 2008, 11:31

speedracer6g wrote:Hi guys thought i would chime in on this discussion. heres my 5 cents worth of information. Bipolars have a lower gain than mosfets that is not new news to anybody. That is a plus compaired to bipolars. I will use either one but my favorite is the mosfet because you do get more power out of it compared to mosfets due to the higher gian. Put one on a b&k transistor analyzer and look for yourself. I have a Bird 43p meter and that is industry standard and i get more wattage out of the radios here in the shop with it and bird meters dont lie not for $600 that is for sure. when i worked for motorolla that is what we used and pretty much what anybody else uses too. so what meter is this guy using a Dosy ha ha. you can calibrate them all day and they are not linear anyways. I also want to konw that if mosfets are junk how come all the new radio from ranger are using them. Oh thats right all those engineers are idiots i forgot. Im out

Mike
FCC General radio telephone license holder.
RF tech.
not a garage tech. :lol:

I am captian screwdriver and i love bipolars so much i want to marry them ha ha :lol: sorry i had to add that.

This is all really great information, and I do appreciate the honest, experienced-level input, I'm glad to see that there is someone else with some educated experience posting here. Why aren't Cobra and Uniden using the MosFet transistors in their new radios? It appears that Galaxy, Connex, Ranger, Magnum, etc. are using them right out of the box.

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Post by rockhavenradio » Monday 22nd Sep 2008, 13:27

So, Dodgem250, what are the reasons a mosfet final in a cobra 29 won't work?

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Post by speedracer6g » Tuesday 23rd Sep 2008, 12:46

The only reason i can see that cobra and uniden havent is due to the fact that they can afford to make the changes or that the cost is higher to go that route. I guess that cost probably the issue there. Ranger took advantage of the mosfets because there boards were actually realy easy to make the changes to accept them add some parts here take away a part or two there add mosfets and 5.6v zeners and there you go. Not a real big cost difference there plus the bipolar transistor were getting expensive and rare. Also if anyone out there has bought IRF520N mosfets in bulk you can see how cheap they are to buy. The only negative thing about mosfets that i can say is that they are less forgiving at high swr antenna setups but usually above 1.5/1 ratios. That is just a rule of thumb that i like to stick with. I like to stay as close to a 1/1 ratio or 0% reflected on any antenna setup for any radio. Anything abouve 10% reflected power is too much as far a i am concerned. Oh and from my expereince there are capacitive differences in the IRF520 mosfets I always order the IRF520N mosfets for the ranger radios the V version will give you poor results. If you look at the specs the irf530n has an input capacitance of 330pf and the 520V has 560pf so you can see why there would be a difference in performance.

MIKE

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Post by Dodgem250 » Tuesday 23rd Sep 2008, 13:21

rockhavenradio wrote:So, Dodgem250, what are the reasons a mosfet final in a cobra 29 won't work?
OK... OK... OK... I was wrong.

( insert a fresh pot of coffee for this, 'cause here I go... )

So, maybe I should man up and correct myself for you younger fellers out here.

I should have said, "Yes, it will work, No it won't last".

But, hey, I install these gadgets about every day here in the shop, but, what the hell do I know, right? I'm just some guy who started doing this stuff 30 years ago as a kid, who was taught / trained by three schooled CB repair technicians who were in their prime in the hobby's prime and well after that too, and I have been doing it ever since and I have been in more radios than some of you guys have weeks in your years, but, I guess I'm just the ego-know-it-all-wanna-be cb radio repair doctor with a golden screwdriver who doesn't know much about nothing, no wait a minute now, that would be some of the guys who read this stuff.

Now, if you want to get back on subject, before you start throwing out your pitiful little sarcastic comments, which I know you "Big Dogs" are just gonna have to bite on... It's in your nature... Why does Cobra and Uniden NOT use this stuff in their radios from the factory? Either the Japanese can't do it, or Cobra & Uniden already know, it's not system of parts, that their radios will handle without a complete PCB overhaul. Now, you can run to ebay and buy a radio with NEW HIGH POWER 2030 FINAL UPGRADE (that's been around for the past 5 years), and just smack that donkey in the ass until the thing goes POOF!, but, what the hell, the guy who sold it to you already got his money, and I get mine by fixing the stupid mess for you.

PS: the only reason I keep coming back here is for the pure enjoyment of reading what some youngster is gonna post next. See, I just set here in this repair shop and fix CB's all day and put in whatever the hell I get paid to put in, been doing for 3 decades, how about you guys? No, I don't know it all, but, if I wrote books about what I do know, I could probably give those folks at Britannica a run for their money.

And yes, I still use the term DUDE... dudes!

How much does that extra 5-8 watts of hardly noticeable increase cost you anyway? I'll tell you... Parts plus $10.00 /HR Labor (if you're lucky), so, give me a shout, I got a bags full of 2078's, 2166's, 1969's and some really pretty shiny, new 2030's, how many do you need? Hell, I've been collecting these things for years and years... did someone say they were hard to find? Oh look here's a new bag full of whatever you guys need.

Point here is fella's - My customers keep coming back...

I guess they like to hear me say, "I told you so".

And then they come back and say... Do it again, that was fun.

And on their 3rd trip in the door, I just install a new 1969 for free.

But, anyway, deer season has started here and I'll see you guys in the Spring

BUMP-BUMP!
Dodgem

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Post by speedracer6g » Tuesday 23rd Sep 2008, 23:58

In all sincerity i give the you respect dogem. I learned from the old rf techs that had been doing rf work for 30+ years like yourself and i am sure you can work on an old tram or golden eagle like nobodies business. I dont hate the 1969 finals i use them too. I agree alot of people out there want mosfets and you do get a llitle higher failure rate. But from what i have seen this is due to a prexisting problem with the antenna. I also see alot of mods out there that dont set you bias voltage. I think the real problem is how the mod is done. I also would not use the 2030 mosfet I would stick to the 520. I know for a fact that the 1969 units are no longer made. If you can still find them there is a good chance they are fake. Not saying there still isnt any out there because there is just not too many and not for long. So lets burry the hatchet here and say the 1969 units are more stable for now until everybody gets on the same page with the mosfet upgrades. I personally use a cobra 25ltd everyday and it has a irf530 in it and i havnt had any trouble with it. I will admit when i was experimenting with the bias voltage i poped one but that was because it was set too high. I would be interested to see how you install your mosfets just to compare nots here. I am not here to say who is wrong or right just interested in how you do them compared to my shop. Your welcome to email me personally. From one rf tech to another you dont stay in business forever doing crappy work so cheers on that. And drop me a email. bye the way is in bow season already.

mike

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Post by James Unit 198 » Friday 26th Sep 2008, 1:27

speedracer6g,
How do you analyzer a Mosfet and come up with the fact they having a higher gian than a RF driver or final bipolar.

I have my doubt that you really know the facts about IRF type Mosfets.

James.

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Post by speedracer6g » Saturday 27th Sep 2008, 0:51

:roll: Well I dont know what to say to that I got the equipment here to do it and that is that. Non only do the numbers on my B&k model 530 transistor tester not lie my results dont lie either. I may not be Rick Jackson but I do have more knowledge than your average guy. I have 15 years of experience and a degree in electronix to go along with it if its worth anything. So other than that I dont know what to tell you. The only other thing is that if you are modding your radios based of of ekl papers or stuff on cb tricks half of that stuff has errors on it and wont work properly I have been there done that. If you are basing your comments off of the results of that then yes i would agree that mosfets suck. But the truth of the matter is they dont. Bipolars dont suck either its the same for guys that like tubes they would have said that transistors were crap back in the day too. And i agree if you want to have an awsome linear i think tubes are the way to go. So this conversation on whats better can go on and on.

:wink: have a good day

MIKE

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Post by James Unit 198 » Saturday 27th Sep 2008, 8:39

speedracer6g,
I am not trying to run you down.
I am now intrigued as to how you get DC Current Gain (Hfe or beta) from a Mosfet, as IRF type Mosfet is just high-speed switch and was never designed for RF applications.

Your B&K transistor tester may be you are reading drain current to drain source voltage but this is not the DC Current Gain, and all relevant to the idss current which should be about 2 to 5 ma for a drain current to drain source voltage test.

One think you may or may not know is that if you increase the drain source voltage you increase the output power and the device will run cooler.

I have work in the design of semiconductor for over 27 years for Texas Instruments, Fairchild Semiconductor and currently with Motorola.

James.

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Post by speedracer6g » Saturday 27th Sep 2008, 13:32

Ok then I am not worthy, I get it You have some years on me. Ha Ha :lol:
Then that leaves me wondering a little then what is gm? I know for bipolar transistors it displays Hfe gain. What is gm on my meter I was under the impression that the was the gian of the mosfet. You will have to excuse me i am not an engineer that designs stuff everyday so you do have an advantage on me. I just know that regaurdless of what the complaints are here on mosfets that i get them to work here just fine and i get good clean modulation without any distortion. I said this before but there are alot of botched mods out there that dont work properly. I beleive this is the cause of most of the failures out there. Now I dont have a spectrum analyzer to check for any harmonics as of yet. I am still trying to get hold of an hp service monitor or motorolla r2600 service set. I currently have one of the older sets that motorolla made and it works fine for now but am looking get something with more options like a tracking generator and spectrum analyzer. But getting back to the point i set my bias voltages on any cobra or uniden setup with an IRF520 to about 2.8 to 3.2 volts much more than that and it get a little unstable. I have done many bipolar to mosfet upgrades on the ept3600xx boards with great success. I guess the big question here is if mosfets are so bad then why is ranger using them? Now I am just asking this in all sincerity. I know that i may not be a genius but I know good results when i see them and I dont just use a wattmeter. I just have to point that fact out because you know it takes more than a wattmeter to do radio work. I was a radio tech for a motorolla outfit for 4 years before leaving to go on my own. I worked with some of the older techs there and learned alot from them. I also need to know this why are mosfets not suited for rf? I know from my theory classes that they are more or less high speed switches but isnt that the point with rf? :-k

Just trying to keep this discussion going maybe we can get to the bottom of this or maybe it will just have to be like the old saying "wich cam first the chicken or the egg" or "if a tree falls in the woods and knowbody is there to hear it does it still make noise?" :lol: hey everybody have a good night I am gonna spend some time with the wife and kid

Cheers to all it friday :D

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