hello again. i recently purchased a cobra 148 that i know nothing about. plugged it in and had to adjust the frequency a bit but otherwise seems to work fine. keys 4 and swings to 12 ish. radio was clipped but based on reports from others isnt as loud as my stock 148 which was also clipped. using it as a base with a silver eagle mic. with the dynamic turned all the way up the stock is much louder. i have no clue what has been done to it beyond what i already stated. any thoughts on what i should check. i have a meter inline with the radio. cant afford to get it to a tech. i have no other test equipment
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cobra 148 gtl
- Thread starter zebbman
- Start date
You adjusted the radio to frequency yourself with no test equipment?
Are the radios front mic or side mic? The side mic 148s are way better.
The stock "what" is louder? Read your post and you'll see it is hard to follow.
I wouldn't want get any more than that out of a 1969 transistor anyway.
So long as the modulation is clear; what's not to like?
So long as the modulation is clear; what's not to like?
not the question i asked. lets make it simple. beyond coils what do i need to turn up or down for max rf.. also receive..im wondering if anyone can just possibly answer without statements or questions. not trying to be a jerk but if you dont know why even post
Wasn't trying to jerk anybody...
However, if you want to improve the receive in the radio - you can put a Sanyo 2SC2999e transistor in the first IF amp stage (Q-14 or TR-14). Put the stock transistor taken out of TR-14/Q-14 and put it in the TR-19/Q-19 position - to improve SSB receive. Use only the Sanyo transistor for TR-14/Q-14 for optimal results. The transistor is a real upgrade to the audio receive quality. No re-tuning is necessary either...
You can also add four 1N6263 Shottky diodes in the detector stages too. The diodes will allow more signal in. Replace D1,D2, D21 & D22 with the Shottky diodes for the full treatment. Substitutes are ECG583, NTE583, and SK9975. Same part; different vendors.
Output can be improved with MOSFETS.
However, if you want to improve the receive in the radio - you can put a Sanyo 2SC2999e transistor in the first IF amp stage (Q-14 or TR-14). Put the stock transistor taken out of TR-14/Q-14 and put it in the TR-19/Q-19 position - to improve SSB receive. Use only the Sanyo transistor for TR-14/Q-14 for optimal results. The transistor is a real upgrade to the audio receive quality. No re-tuning is necessary either...
You can also add four 1N6263 Shottky diodes in the detector stages too. The diodes will allow more signal in. Replace D1,D2, D21 & D22 with the Shottky diodes for the full treatment. Substitutes are ECG583, NTE583, and SK9975. Same part; different vendors.
Output can be improved with MOSFETS.
B
BOOTY MONSTER
Guest
if the radio is functioning properly and you have a good mic on it as well as a good antenna setup the best way to get more tx out of it is by adding a ab biased amp and running it cleanly . robb did a good job explaining how to improve the rx end .
That's some good info there.
I am assuming this only applies to the older side mic 148's?
I remember doing some similar mods along with an upgraded voltage regulator to my RCI 2950 years ago, and it was def an improvement.
I'd open them both up side by side on the bench and look for anything that stands out as being different inside the 2 units. Doesn't really make sense that one would be louder than the other if they both had same mods and power output characteristics as well.... Someone may have done a mod unknowingly wrong on the 2nd 148.
a 148 stock no way junk low modulation power mods help the 148 gtl out i have to side mic and full of mods over 30 watts swing 100+ modulation with 2sc1969 final and 2sc2166 driver npc mod and stock mic all you need and 2 pill would wide 148gtl mr,hobo cb shop weatfelds of ks
Thanks
No; that info will work as well on new Cobras too. Other brands and models of radios as well; the parts location are different though. As far as the Sanyo 2SC2999e transistor goes - just be sure it is the transistor that has an "e" designation on the end of the part number. They have the highest gain. Its an important distinction - BTW.
Some people have questioned upgrading parts. 'Why do you need to change the original parts out of the radio'? The reason is clear. The mfr doesn't buy the best parts for radios when they put them together. They cut corners where they can to achieve reasonable results and save every dime they can. This keeps their unit price as low as possible and in turn makes their product more competitive in the marketplace. Doesn't mean that it cannot be improved upon and it isn't necessary to do either. Makes a difference on the receive though.
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