Just throwing a question out there (Cobra 21 vs Cobra 25)

[guitar_199]

Just looking at the SAMS CB Photofacts and I see that the Cobra 21 and 25 are in the same volume.

So if the same SAMS copy covers both radios.... how do you know what the differences are? Surely a 21 is not identical to a 25 or everybody would have saved money and gotten a 21. I did see that, in the area of the channel switch there was an annotation that the 21 and 25 used different channel switch boards. There HAVE to be other differences!!!!??? At least I would think so.

I'd be interested to see any comments that anyone might throw out there!

Bob

 

[Lkaskel]

So I have a Cobra 25 LTD Classic side mic (old school) and I am looking at some pics of the 21. The 25 has a few things that the 21's do not such as a NB, RF Gain and CH9 switch and I am not seeing a 21 with them. The 21's have a variety of things like a Loc/Dist switch, Dimmer knob, and even a CB/PA switch depending on the version.

 

[loosecannon]

i used to run a 21GTL for a while and the main difference is that the 25LTD has a noise blanker circuit.

I actually added that circuit to my 21GTL as the board has the holes and silkscreens just not the parts.

the other differences are the RF gain and dimmer switch on the 25.

both models have the ANL on all the time.
LC

 

[brandon7861]

21 used bipolar mixers, 25 used fets. There are other circuit differences too, depending on what schematics are being compared. I see in the sams index that it covers the GTL, LTD and LTD classic, no mention of the plain 21 or the plain 25 that didn't have audio ICs.

Edit the 21GTL and XLR used fets, but the LTD and the plain 21 used BJT mixers

 

[loosecannon]

Brandon if only it were that simple lol.

the first series was crystal controlled and used bipolars for the mixers and push pull pairs for the audio amps.

these are the 21, 25, and 29.

after that came the XLR series that all used the UPD858 PLL, had FET mixers, and were all about the same with more bells and whistles on the more expensive model.

these are the 21XLR, and the 29XLR. unless im mistaken, Cobra never put out a 25XLR.

the next series was the GTL series, using the TC9106 PLL on the 21GTL and the 25GTL (only real difference is the 25GTL had a noise blanker and an RF gain).
they both used FET mixers as well.

Im not sure on the 29GTL which PLL was used in it as im not in my shop, but i think it might have been the first radio to use the UPD2816 chip.

After that we have the LTD series including the 21LTD, the 25LTD, and the 29LTD.
both the 21 and 25 still used the TC9106 PLL and the 29LTD used the UPD2816.
all still used FET mixers.

the real confusion comes in when they release the "classic" series, using the LC7132 PLL and bipolar mixers.

I have both the 21GTL and the 25GTL and i can say that their noise blankers are some of the best ive ever used.

LC

 

[brandon7861]

Brandon if only it were that simple lol.

I didn't say that was the only difference, I only had time for a quick glance at the schems