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50 watt Cobra 29 review from FGBest

Moleculo

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,200
1,686
283
Well folks, I went over and saw it for myself. On Saturday night, I went over to FGBestCommunications in Ontario, CA.



When he started, Frank asked me if I wanted to see one of the 5 new Cobra 29's he had for sale on the shelf that were already done up. I decided to look at that later, but instead had him pull one out of the box that was still sealed up from the factory. I watched him work on it for a bit while he changed the final, the driver, and a bunch of other stuff. (They can post the details if they're so inclined). At the end, he did a full TX & RX alignment and put it on his Bird 43P. He got a full 48 watts out of it. Justin came over, said "gimme that" and proceeded to change a few more things and ended up with 51 watts on the Bird 43P.



It's a little hard to see, but here's a video clip that shows it doing 51 watts on a Bird 43P. He's got a 50 watt slug in there; note the needle pegged all the way to the right.



Then he put it on his HP analyzer (which still has the calibration sticker on the back) and it showed 53 watts. Here's a clip of that The numbers in the middle on the left are peak watts.



I also took a shot of it reading AVG power. This is on a Bird 4410.
avgpower.jpg


You can't see the slug in the pic, but if I remember right, the meter shows 21 watts AVG.



Lastly, here's a vid clip of the Cobra 29 performing a spectral analysis, demonstrating that they didn't just turn it into a splatter box.



Keep in mind that all this was done without yanking the limiter or volting the final. I was impressed.....Now I WANT one! <img src=http://www.ezboard.com/intl/aenglish/images/emoticons/smile.gif ALT=":)">



Moleculo


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=moleculocdx363>MoleculoCDX363</A> at: 5/4/04 3:12 pm
 

Justin,





Whats Retail Price on one of these radios from you guys currently?






</p>
 
Oh yeah...I forgot to include that part: I did ask them what they sell 'em for. If I remember right, it was $160 + shipping. They've got echo boards and their own designed talkback board they can add on, too for a little extra. Their phone number is on their website.



Moleculo


</p>
 
They showed it to me 2 ways: 1 way keying 8 watts. Then they mod'ed it to drop the carrier to 2 watts. They still got 53 watts on the HP with a 2 watt carrier.


</p>
 
Showed it in the pic up above...21 Watts. I know, I know...I listed it as AVG not RMS. Not to get sidetracked here, but technically RMS is a measurment of VOLTS not POWER. Watts is a measurement of Power. A measurement of voltage using the Root Mean Square method when converted to a wattage measurement is properly expressed as Average Power.



Back to our regularly schedule program.....


</p>
 
please explain how the meter is showing 21 watts?



on each of the 2 scales the pointer rests at (rounded up) .32 on the top scale and a 1.0 on the bottom scale. when both figures are multiplied by a power of 10 (as is indicated by the switch multiplier setting) we come up with 3.2 watts on the top scale and 10 watts on the bottom scale. how do we arrive at a figure of 21 watts?



RMS: Literally "root mean square." A DC voltage that will produce the same heating effect (power output in Watts) as the AC voltage. For a sine wave, the RMS value is equal to 0.707 times the peak value of an AC voltage. Example: divide Peak-to-Peak by 2 (or in half) and multiple by 0.707 = RMS voltage.



according to the definition given above, @ 53 watts Peak-to-Peak (or PEP) the associated RMS value would be approximately 18.7335 watts. neither of the two scales pictured on the 4410 above provide an indication anywhere near this value. so what gives?



" you will find that RMS is what drives a amp not PEP...."

the difference between rms and pep is clearly stated above and is merely a "relationship" of quantitative mathematics. (A DC voltage that will produce the same heating effect (power output in Watts) as the AC voltage) make your measurements using the value that allows you to most clearly interpret the results.



since 53 watts pep is the same as 18.7 watts rms the amp is driven the same regardless. all other things being equal, the amp can't tell the difference and obviously neither can you.


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 5/6/04 11:59 am
 
he apparently hasn't stopped copying and pasting long enough to ask a few questions like: what happens when Pin exceeds 1 watt and what happens when VCC exceeds 12 volts. these radios also do not represent a class AB amplifier application either.



don't bother with the 2312, the spec for AB application with 1 watt Pin and 12 VCC is only a half of a watt higher than the 1969. your failure to understand what they are actually capable of hinges on your lack of understanding with regard to the 3 parameters mentioned above. also, if you'll actually read the document you'll see that the output figures are given for minimum and typical output levels....the maximum output level is blank and for a few very good reasons. learn to read.







in the meantime i'll spell it out for you........



when Pin increases, power output INCREASES

when VCC increases, power output INCREASES

when operating Class C, power output INCREASES

www.firecommunications.co...lass.shtml

when devices are FIRST RUN, power output INCREASES



hence the term minimum........the absolute least amount of power produced by the device with the Pin and VCC quoted.



or typical...................................the average amount of power produced by the device when Pin and VCC are as quoted.



maximum..................................the maximum amount of power

produced by the device when Pin and VCC are higher than

those quoted (minimum and typical) with preference given to "first run" devices, those that meet/exceed manufacturer specifications. prime parts suppliers order lots in 10's of thousands of pieces at a time and test them in the appropriate "jigs" to determine parameters such as hfe, gain, beta and record these parameters to assure mutual compatibility when matched in pairs, quad sets, etc.. all devices failing to meet the specifications are designated as "seconds" and sold to the wholesale and distributor outlets while they keep the "first run" devices to sell to their own customers. first run devices are the top of the line.



as a matter of fact and personal experience, the only time i've ever seen only 10 - 14 watts out of any of these the lot was hurriedly and foolishly purchased from a wholesaler who didn't stock "first run" devices and bought only "seconds" to sell to their customers!



anyone wish to add anything, feel free to do so. i may have missed something.


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 5/6/04 4:50 pm
 
Freecell. There's no direct formula for converting Average Power or RMS volts to PEP watts or vice-versa. I'm not sure where you got that info from. You can calculate PEP from Peak to Peak Voltage by taking (1/2 Peak to Peak voltage x .707) squared / resistance of the load.



Maybe I'm getting hung up on terms, but your example isn't technically accurate (unless I'm missing something). As you can see by the formula above (which is on the General class test, btw) 53 watts is not a peak to peak voltage value as you used it in your formula. It's a PEP WATTAGE value calculated from measuring peak to peak voltage. Anyway, we should probably make another thread out of that discussion <img src=http://www.ezboard.com/intl/aenglish/images/emoticons/laugh.gif ALT=":lol">



On that Bird 4410, there's a multiplication slug in there that you can't see. Unfortunately, I forgot to write down the details on what was in there. I was also going off the top of my head at 21 watts AVG, because I forgot to write that down, too <img src=http://www.ezboard.com/intl/aenglish/images/emoticons/frown.gif ALT=":("> . I do remember it was over 20 watts. Maybe Justin can chime in here if he can remember.



Moleculo


</p>
 
re-read the definition given previously. let me get back to you on that. Justin will not be available until after 9:00 pm CA time.




</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 5/6/04 9:18 pm
 
<blockquote>Quote:<hr>There's no direct formula for converting Average Power or RMS volts to PEP watts or vice-versa<hr></blockquote>



I went back and read what I wrote and realized I said that wrong:



I should have said that there's no direct formula for converting Average Power to PEP for a voice waveform. For FM, CW, RTTY, etc., PEP and average power are always the same. You CAN convert RMS voltage to a PEP watts figure. However if I'm not mistaken, the Bird meters (not the Peak models) measure CW power which is another term for AVG power. See if we can add to the confusion a little more...



We still need Justin to give us the accurate AVG power reading.





Moleculo


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=moleculocdx363>MoleculoCDX363</A> at: 5/6/04 8:58 pm
 
it would seem that the term rms when used immediately preceding the word power is actually an oxymoron....i believe the correct term is "average power." thanks for bringing this to my attention in an earlier post.



in the meantime, i'll stick to a quick and dirty fromula that i use to extract average power levels from given pep measurements, namely this:



pep / 2.6 = average power........i often substitute 2.5 so i don't have to work with long decimal figures, repeating or otherwise. now i know why the 18.7 watt figure based on my previously mistaken line of thinking didn't seem to jive. i promise i will discontinue the use of the term rms in my future postings except when referring to voltage. less confusion.



so there you go....53 watts pep = approximately 20.3846153846153846153846153846154 watts of average power........you won't mind if i use the 2.5 value to come up with 21.2 watts instead. ask me some other time how i arrived at that figure....a whole 'nother story.



you are correct in your final analysis, or we both are. i'd still like to hear more about the slug in the 4410 when you find out. yes, the bird meters measure cw/avg power unless outfitted with the 4300-400 Peak Power Measurement Modification Kit.



here's a little something you can read and ponder in the meantime.



www.firecommunications.com/ammodpep.htm






</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 5/6/04 9:45 pm
 
I wish I had one to play with, but I don't. I just watched them do up a new one for sale. I think I'm gonna pick up one soon or try to find a deal on one and have them set it up to try for longer period use.



Moleculo


</p>
 

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