1446 in a cobra 29?

[skirtchaser]

I knew somebody would have some knowledge on this thing. I'm seriously not trying to do this, but my friend is obsessed with it. I'll take the pics over to vegas when I go through there tomorrow, I'm sure he'll appreciate them.
Thats an interesting looking input coil in pic#2, where the hell did it come from ? The board looks like a galaxy in these pics, perhaps a 33? That must be interesting using a dual final to drive the single pill.

 

[Butcher318]

Dude give it a rest, if Freecell has lots of misguided truck drivers that want this mod done then good for him for doing it up nice and neat for his customers. For 90% of the rest of the market it's just not popular so why should a guy like DTB spend a bunch of time with it so he can sell two a year.

Tell your friend to get some velcro, a jumper, and a Kl-203 or KL-200. It will cost him less money, work better, do more watts, and when he decides to sell it he can take it back apart and get most of his money back.

Freecell, DTB, and SS8541 are all sharp techs. Since 2 out of the three don't generally do that mod that should give you a clue.

 

[BOOTY MONSTER]

who said they were "missguided truckdrivers' ? some people dont want a couple of boxes and the assocated jumpers and power lines to feed them , and draw attention to them . im sure the work of either of the 3 guys mentioned do cleaner and more durable work than KL . just because someone wants something that your average tech has no idea how to do and even seasoned quality techs are scratching their heads about doesnt mean it can't work , and work well if done by the right person . i do think a velcroed kl amp is better than a stinger board , neither of them will work as well or as long as jacks work .
most beer drinkers dont like champagne anyhow .

 

[skirtchaser]

Mr. Butcher, greetings. I appreciate you taking the time to drop in and contribute.
As far as resting, when they pay me to do that, I'll get real good at it too. But it is highly overrated, I figure I'll be mellow when I'm dead.
You know, the funny thing about Kelly is he is not an operator, not even a little, he's a industrial electrician, and he really has no use for the "CB" thing, he's just into working on them as a hobby, and he's into this project. Now I appreciate what you're saying (except for the KL part, what made you suggest those, Ill never know) but that's not the point to him, it's the project. It's about a different way to enjoy the hobby. Now I can see that thats not where you come from and thats fine too, to each their own.
As far a who does these and who doesn't, I guess it's about customer service. I respect sharp shooter immensely, I started this whole thing out on the Panther board, and I have seen him provide excellent advice to a lot of people for quite a few years now, and having heard his setups around the country, I know what he can do. I'm not all that familiar with DTB but I'm sure he runs his shop as he sees fit, although it seems (and I could be wrong, if so I apologise) he focuses more on a storefront/retail operation. No disrespect implied or intended. Freecell is a Ham and has a fairly well rounded background in engineering and theory. He spends more time removing other shops atrocities, and restoring radios (preferring to allow for the engineers ability that created the circuit) then investing the time necessary to tune the unit to what it should do if not for the shoddy tuning that comes from assembly line. Typically blowing away the performance that the previous shaved ape achieved with all his circus act and snake oil. Usually "Modding" is not his thing, but if his customers want something, and it can be done reliably and effectively then he gets it done for them (I personally have never seen him sell an echo board or a noize toy so that should say something. And that sir is called CUSTOMER SERVICE. That's the Jack I know, and that sir, should tell you something worth knowing.
Respectfully
711

 

[Switch Kit]

most beer drinkers dont like champagne anyhow . Well , if your freak'in drunk and that's all that's there ! I doubt they would really give a flying duck ! at least I wouldn't anyway. You ever feel like you are I should be bowing to the RF God's ? ....Go freak'in figure.
My God already !! SAVE THE TRUCK DRIVERS !! and pocket that savior cash that goes with it. Those freak'in Itailians and there God damned KL amplifiers and boards !! they should all be tied to freak'in ant hills bare ass naked in about 120 degree sun cooking heat !! Just face it fella's .....It's against Einstines theroies of realitivity to even attempt to have any fun......you guys out there modding this and modding that should all be boiled in hot over used nasty smelling cooking oil !! How dare you all not go to the chosen few of RF goodie two shoes !! Shame on you's !!

 

[AudioShockwav]

Here is My take on this issue......
There are drivers that are limited to a Stock looking radio, this Mod can be done, and if thought out properly, can work well. Freecell and a few others seem to take the time, and do it properly. Even Uniden has gone to the MRF455 in the latest high end models, so it can be done.
In "most "cases, it is easier to just add a small outboard amp, but there are times when this mod has value.


73
Jeff

 

[freecell]

only the attempt to characterize company drivers restricted from using external amplifiers in their trucks as somehow being "led astray" is misguided. or maybe it's the fact that i have a solution that bothers you most and in that you somehow justify your use of the term.

the first + or - 10db. is not only the largest increase in terms of watts per dollar, it's also the most economical. most also don't require any more coverage than the standard 40 channels.

while richards main thrust is lmr, maybe there are no company drivers with similar needs in the pa area and while i find that difficult to believe, i can only speculate.

 

[Switch Kit]

Was talking to a couple of drivers last night on the radio , I first heard them and was very impressed with there telephone quailty audio that they both had .....wasn't overly load just very clean and understood , I keyed up and broke in and told them that they were both sounding very nice and what kind of radios were they talking on ? One was on a Cobra 19DX2 (just a little back pocket radio from Walmart for 38.00 ) the other was on a Uniden 510 (about the same as the other) they both drove for Von's marketing. They said the trucks came with built in antenna's on the mirrors. The one guy had his 19 for a couple of months and the other guy said he had his 510 for about a year and both radios had been out of the box on there stock mic's . They both said that they had gotten complaments on there radios quaility audio in the past from others. They both said they had thought about getting them tuned up , put with all the props they had gotten over the time they decided to leave well enough alone. I guess the RF God's haven't gotten a hold of these two guys yet ....huh ? They both said the radios worked great for what they needed on there local jobs. Yeap .......there I was on a swing kitted echo touched radio into 400 watts talking to these guys on back pocket peanut whistles maybe doing 4 whole watts . I should have been imbaressed ........alls I could honestly say to both of those drivers was to don't touch a thing on there radios that they both had top notch audio and to save there money from having anyone stick there money hungry hands into them. Is there a moral to this story ? Maybe ,maybe not , but I enjoyed telling it.

 

[Butcher318]

Freecell, it sounds like you are one of the few that actually will be straight with a driver and still give him quality work for his money. What does it cost for this 1446 mod if a driver brings his radio in? Just curious. In recent years there have been alot of newer radio's released that have more power. This gives drivers that cannot run an amplifier more options.

Freecell it does not bother me at all, in fact, I hope your the real deal and not another 50 watt Cobra 29 con. Thats why I said misguided drivers, for every shop that does it right there are 50 that screw these drivers over with "the same mod". Only they use duct tape, electrical tape, leave solder balls all over, and the radio is an overmodulated POS when the guy gets it. If everything is as you say my hats off to you.

 

[skirtchaser]

 

[skirtchaser]

Thank you my brother, you know who you are, very detailed layout and easy to understand setup.I seriously appreciate your understanding of what the forum is all about and I appreciate your effort in sharing information. Thanks again and I will respect your request.
73's
711

 

[Master Chief]

Someone needs to put a leash on this guy!

 

[bushwacker]

I've done this in a couple of cobra 29 type chassis... your biggest problem is the radios design itself and heat dissapation . I haven't checked out the links that were supplied by other members.... but the mod can be done.

Personally, the way I've found that works great for heat dissapation is to mount the pill right on the heatsink for the driver and final... right in front of R114 there is a nice flat spot. Thats where I mount the transistor. BUT.... what makes this way work is to get some air flowing over that piece of heatsink. I've done this by cutting a small hole in the chassis right behind the heatsink where the pill is mounted.... just to the side of the so239..... I make the hole just big enough for a very small fan to be mounted here.
The other thing is you need a place for air to get out... what I've done is put some spacers between the internal speaker and the cover.... so air can escape through the speaker holes.
Its just the way I do it... you can just mount it on the metal chassis at the rear of the radio. With my way I've been able to key a 50 watt carrier (for testing) for a very long period of time with good steady heat dissapation.

I've done this mod with 1446's....455's... old trw transistors and 2879's. Personally... I find that the 2979's actually give a better audio quality.

The other BIG isssue about doing this mod is where you jump the new rf amp section in( which is what you are doing by adding in a pill) on a cobra 29. The problem with cobra 29's thats different from other radios that this mod can be more easily done on is where the RX line comes in. On alot of Galaxies and other radios the rx line comes in AFTER the output LC tuning networks. Basically, after the final rf amp there are good places to jump in a new rf amp section after the last rf amp lc circuit BECAUSE the rx line comes in further down the line.
Basically what I'm saying is you have to jump in the new rf amp section at a spot BEFORE the line to the reciever (around C60). If you put in an rf amp after the recieve line input (after L14 or L13)... nothing will get to the reciever... you will have no rx. You also have to make sure that your not messing with the matching network to the reciever.
You may do the mod and have good output power but have VERY poor RX because you have messed up the matching to the reciever.
Thats a very important thing to remember when doing this mod.
Right after capacitor C60 there is a junction... this is the Y network where the input to the reciever and the output of the rf amp section meet.... that WHOLE line after that point to the antenna connection is shared for both input RX and output power. On alot of other radios this junction is futher down the line like after L14, L13 and L12 ( matching/parasitic/harmonic surpression). And thats what makes this mod hard on this radio... the reciever input is AFTER the final rf amp but before the parasitic supression/matching network. Basically the rx comes in from the antenna and through this LC network to the reciever. On other radios rx would come in from the antenna and split off to the reciever before this lc network bypassing it completely. This gives you more places to jump in a new rf amp section easily without effecting the input tuning to the reciever.

Its not just a matter of jumping in a new rf amp section....its a matter of jumping in the new rf amp section WITHOUT messing up and rx to the reciever.

Heres something to try...put a signal into the cobra 29 your friend is working on and check the RX on the meter (tx with a second radio).... then adjust coil L14 on the cobra 29 while doing the same thing (tx on other radio).....check if you loose rx as you adjust coil L14 on the cobra 29.... Coil L14 is right at the Y network for the RX'er and rf amp... a difference in tuning at this point effects the reciever as well as the rf amp. L14 tunes the output of the final rf amp ( to keep it simple) BUT it also adjust the INPUT recieve to the reciever.
Thats why alot of guys that get BIG swing power out of their cobra 29's will also say their radio has crappy recieve.

MY point..... a relay thats keyed by the swiched voltage at TR16 (around 8 volts.. it can activate a relay) makes things easier. Using a relay insted of jumping in an rf amp is the easiest way for someone doing this for the first time. You will get good rf power out and have no effect on the reciever.

There are reasons why this mod isn't done on cobra 29's and it all has to do with where the line to the reciever splits off ( Y network).
If he wants to put a pill in his radio cool....build up an new rf amp section and jump it in WITH A RELAY..... its easier.

More output power is uselss if you are sacrificing recieve sensitivity to get it. And thats the trick with this mod or any other high power mod to cobra 29's... increase the ouput power but don't decrease the rx going to the reciever.

Lots of things to consider and look at......
Good luck.

 

[bushwacker]

OK Then, I guess we all admit that Freecell is the supreme 'hefe, I can't believe that no one is interested in sharing the 411 on this mod, or perhaps........NAHHHH!!!!

.

Any sharp tek worth his own salt can figure it out from this picture.

There's a tuned input circuit and a 1 turn output coil.

These are pictures of the Justin/Frank Mod

The pictures supplied are of a pill mod but NOT in a cobra 29. In the radio pictured there is an easy place to add in a new rf amp section. In a cobra 29 its different because of where the rx line splits off... its not as easy to add in the new rf amp section without it affecting the reciever in a cobra 29.
Its no problem to build a simple input output tuning network for the pill and get it matched good enough.... but having a convient spot to add this ciruit in without it effecting the reciever is what makes it "more do able" on one radio than the other.
Its all about where the line to the reciever splits off.

 

[Number15]

Why bother, tell your friend just get a one pill amp?? just my opionon.