Cobra 18 WX ST II

[Onthecoast]

I know that everyone dogs on this radio, but I just wanted to pass along for anyone out there who has one or was thinking about picking one up on the cheap, they can actually tune up decently. After tinkering with it I found that you can go down to 1 watt DK if you wanted to and up to about 6. It peaked out surprisingly. I was consistently getting 18 watts PEP and pegged the meter quite a few times on the 20W setting. If you wanted to run it up there you should be able to run 4.5 to 5 DK and swing to about 18-20 or turn the DK down to 1 watt if you like. Not a world beater but certainly not bad. Much better than my brand new Bearcat 980 which will max out at 6 watts DK and swing to only about 9.

 

[psycho]

No matter what you say the radio will do, it's still a Cobra soundcrapper. 18 watts peak sounds EXTREMELY optimistic.

 

[jessejamesdallas]

Much better than my brand new Bearcat 980 which will max out at 6 watts DK and swing to only about 9.

Yeah...but try and get SSB on that Cobra 18!

 

[Robb]

I've aligned three of these radios - and own one - and never saw 18 watts PEP out of it. IIRC they use a 2078 final transistor and not a 1969. If you do get that much power out of it; that final just wont last long - IMO. It is also too easy to turn this into a 'bleedover box' just to see more watts. By spreading/disabling the 54mhz trap coils to milk ever last watt out of it isn't honest on-frequency watts either. I just wouldn't do that that to any radio I work on - no chance. Better to set it to 1 watt dead key and put a very small amp behind it and keep the modulation @90% for better results. Otherwise, it will just sound and work like a splatter box too. Unless that is your goal.

My limited experience with the sound tracker feature is mixed. So is my opinion. Works very well on some radios (Cobra 25 & 29) and sounds horrible on others (Cobra 148GTL). Works OK on the 18 I have. The sound tracker is actually audio compression in receive AND transmit - which can give you a better AVG power output than a radio that doesn't have compression. So long as you don't set the modulation too high, it can be a plus if using a decent mic . . .

 

[Onthecoast]

Yeah...but try and get SSB on that Cobra 18!

Oh yeah. I'm not saying they are apples to apples by any means. I was surprised at how well it tuned up considering its "one of the worst CB radios ever made"

 

[Onthecoast]

I've aligned three of these radios - and own one - and never saw 18 watts PEP out of it. IIRC they use a 2078 final transistor and not a 1969. If you do get that much power out of it; that final just wont last long - IMO. It is also too easy to turn this into a 'bleedover box' just to see more watts. By spreading/disabling the 54mhz trap coils to milk ever last watt out of it isn't honest on-frequency watts either. I just wouldn't do that that to any radio I work on - no chance. Better to set it to 1 watt dead key and put a very small amp behind it and keep the modulation @90% for better results. Otherwise, it will just sound and work like a splatter box too. Unless that is your goal.

My limited experience with the sound tracker feature is mixed. So is my opinion. Works very well on some radios (Cobra 25 & 29) and sounds horrible on others (Cobra 148GTL). Works OK on the 18 I have. The sound tracker is actually audio compression in receive AND transmit - which can give you a better AVG power output than a radio that doesn't have compression. So long as you don't set the modulation too high, it can be a plus if using a decent mic . . .

I didn't spread the coil at all. I only turned the two pots that control the DK and the modulation. I haven't used it much yet. In fact for the past 4 years it has been sitting in a box in the attic so I decided to tinker with it.

 

[jessejamesdallas]

I didn't spread the coil at all. I only turned the two pots that control the DK and the modulation. I haven't used it much yet. In fact for the past 4 years it has been sitting in a box in the attic so I decided to tinker with it.

You picked a good radio to "tinker" with if nothing else....It would be hard to make a Cobra 18 any worse than it is from the factory!

Only other Cobra radio I have ever had, that I would consider a worse radio than the 18, is the Cobra 20 plus built around the late 80's...

And what do ya know...Someone on eBay must think these radios are Collector Items! I almost fell out of my chair when I ran across this ad on ebay!
http://rover.ebay.com/rover/1/711-5...0001&campid=5336136228&icep_item=300776787134

 

[Onthecoast]

You picked a good radio to "tinker" with if nothing else....It would be hard to make a Cobra 18 any worse than it is from the factory!

Well that was kind of what I was thinking as well. I'm looking for a new radio anyway and since this one has been paid for at least 10 years, I don't have much to lose. This is going to be my box for tinkering and experimenting. I am going to put a PCN-60 stinger board in it just so I can get the learning experience out of it.

 

[Robb]

I didn't spread the coil at all. I only turned the two pots that control the DK and the modulation. I haven't used it much yet. In fact for the past 4 years it has been sitting in a box in the attic so I decided to tinker with it.

Just be aware that if the adjusted modulation goes over 100% and if you push the final past its design capacity/watts; then transmitting a distorted signal is not a possibility. It is a likelihood.

You can also adjust the TX paired coil L7 for max output. Legal and proper to do. Checking the modulation % when adjusting the modulation VR is best accomplished by looking at the transmitted waveform with a scope. Don't be ashamed if you get no more than 12-14 watts PEP with a true peak reading meter. The end result is squeaky clean and a radio that you won't be ashamed of. Not a bad radio as some would tell you - IMO . . .

http://www.cbtricks.com/radios/cobra/18wx_st_ii/graphics/cobra_18wx_st_ii_alignment.pdf

 

[psycho]

You picked a good radio to "tinker" with if nothing else....It would be hard to make a Cobra 18 any worse than it is from the factory!

Only other Cobra radio I have ever had, that I would consider a worse radio than the 18, is the Cobra 20 plus built around the late 80's...

And what do ya know...Someone on eBay must think these radios are Collector Items! I almost fell out of my chair when I ran across this ad on ebay!
RARE 1988 COBRA 40 CHANNEL CITIZENS BAND 2-WAY MOBILE RADIO MODEL 20 PLUS | eBay

$295 or best offer. Anything mint from the 1980s is well worth more than 3 times what they sold for new. :laugh:

 

[Onthecoast]

At the risk of getting the BS flag thrown, I will go ahead and say it. I "tuned" this thing on the bench using an unregulated 12v battery that was only putting out 12.6v charged. By the time I got done messing with all the radios, it was registering around 11.8. When I hooked the Cobra up in my truck, the SWR meter was showing a DK of 5, swinging to 25. I probably need to turn it down some, I also won't mention what the wattage got up to when the voltage was in the low 14v range. Not saying it would last at that power level, but evidently some of them do tune up well.

 

[psycho]

At the risk of getting the BS flag thrown, I will go ahead and say it. I "tuned" this thing on the bench using an unregulated 12v battery that was only putting out 12.6v charged. By the time I got done messing with all the radios, it was registering around 11.8. When I hooked the Cobra up in my truck, the SWR meter was showing a DK of 5, swinging to 25. I probably need to turn it down some, I also won't mention what the wattage got up to when the voltage was in the low 14v range. Not saying it would last at that power level, but evidently some of them do tune up well.

5 swing 25 out of a Cobra 18? BS flag has been thrown!

 

[Onthecoast]

LOL! Well I figured that might be the response. I'll get a video up this weekend. The swr/power meter seems to be very accurate as well as it has tested dead on rated power in my other radios. Wait until you see what it does when the car is under load and the alternator is putting out full power back into the battery.