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KL203 Amp

rabbiporkchop said:
I was speculating on the percentage of modulation and threw that number out there. not scientific by any means
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No worries, I thought you made a direct statement about 95% of "Techs" out there, but then you described a dirty swing kit, in your own way... (I read it like a scientific declaration)
The way you worded the statement, it seemed like you judged others by some measure, but now I see the measure in the image you've shared.
I agree "them dudes" don't understand over-modulation, but they sure know the watt meter!
I see now what you meant, 73.
-LeapFrog
 
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LeapFrog said:
No worries, I thought you made a direct statement about 95% of "Techs" out there, but then you described a dirty swing kit, in your own way... (I read it like a scientific declaration)
The way you worded the statement, it seemed like you judged others by some measure, but now I see the measure in the image you've shared.)
I agree "them dudes" don't understand over-modulation, but they sure know the watt meter!
I see now what you meant, 73.
-LeapFrog
Click to expand...
I've purchased lots of used radios from drivers over the years that were lucky to hear somebody a couple miles away.
 
I had some issues with mine cooking all the Mosfets a week ago. Took it apart, replaced the unidentifiable Mosfets (sanded off id numbers) with 13N10s, and replaced the relay with a Avicom unit. I'm now getting 200w+ on SSB and about 175w on AM. Being driven with a 4w carrier and 9-10w swing. The heat sink stays at room temperature after operation for 5 minutes averaging (3) 10 second transmissions a minute.

Total cost for parts from Mouser was about $6.
 
Jim Dickey said:
I had some issues with mine cooking all the Mosfets a week ago. Took it apart, replaced the unidentifiable Mosfets (sanded off id numbers) with 13N10s, and replaced the relay with a Avicom unit. I'm now getting 200w+ on SSB and about 175w on AM. Being driven with a 4w carrier and 9-10w swing. The heat sink stays at room temperature after operation for 5 minutes averaging (3) 10 second transmissions a minute.

Total cost for parts from Mouser was about $6.
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Sounds nice but I would still add a fan. You have bigger finals now and your driving it harder then it was intended to be driven. Not too mention the whole rest of the amp is still small and set up to support smaller finals. The more you talk on it I think you will find it heats up fast.
 
9C1Driver said:
Sounds nice but I would still add a fan. You have bigger finals now and your driving it harder then it was intended to be driven. Not too mention the whole rest of the amp is still small and set up to support smaller finals. The more you talk on it I think you will find it heats up fast.
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I had a gate voltage of about 2.2vdc, which I believe is a fair margin less than the recommended max of 4vdc. I guess we'll see if it goes into BBQ mode again.....
 
dieseldriver said:
10 miles with a 980SSB driving a KL203? You're doing something wrong. I can reach out at least that far on AM with a barefoot PC 122 in a Freightliner Cascadia. I did 26 miles with a barefoot Stryker 955, same truck.

With over 100 watts, if I wasn't reaching out 30+, I'd be pretty ticked off.
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deiseldriver what kind of antenna setup you got on the cascadia?
 
Jim Dickey said:
I had some issues with mine cooking all the Mosfets a week ago. Took it apart, replaced the unidentifiable Mosfets (sanded off id numbers) with 13N10s, and replaced the relay with a Avicom unit. I'm now getting 200w+ on SSB and about 175w on AM. Being driven with a 4w carrier and 9-10w swing. The heat sink stays at room temperature after operation for 5 minutes averaging (3) 10 second transmissions a minute.
Click to expand...

That's nice. How much of that 200+W on SSB and 175W on AM is actually being transmitted on the channel you're on and how much of it is being transmitted as intermod/harmonics? A power meter won't tell you that and I'm guessing that it is unlikely you've stuck it on a spectrum analyser.
 
wpl said:
Ok thanks for the pic...Trying to get some ideas on my cascadia.with a connex 3300 hp, Francis mounted passenger side top mirror bolts over door, seems it's not working...about a mile tx and rx...thinking a ground problem.
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100% a complete lack of any RF ground. DC ground you can measure with a multimeter isn't the same as a RF ground.

Just as an experiment try this:

Get some RG213 braid about 6 inches long, flatten it, solder on some ring terminals on either end like the picture below.
d2e13581-3cc9-94c0-e92b-8056fb9c5657.jpg


Get a couple of serrated washers and some self tapping bolts/screws and try to replicate below but between the door and the truck cab. Put the serrated washers on the paint side of the solder tab so it cuts through the paint to make contact. That'll mean you don't have to sand it and the zinc rustproofing will seal around it to prevent corrosion. See if that improves things. You'll know if it is doing anything because you should see the SWR change on your antenna, i.e if going from the lowest SWR changing up chanels you should see it reach a certain point on a lower channel.

main.php
 
sonoma said:
these little amps are nice but over driving them is a no no. my buddy runs one of these with a 2950 but he has to turn the power down to low or it quits right away. had to replace his finals a couple years ago because he forgot to turn the radio down to low and talked on it.
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Wow that is way too much radio for that little amp. Even with the RF power turned down all the way on 2950 it should still be at least 4-5 watts unless a golden screwdriver has been inside of it.

A bone stock Cobra 29 will overdrive it. Like you already pointed out you forget one time and "pop".

For safety sake, I would not run anything smaller than a 2 transistor bjt amp behind a 2950. That is too close for comfort in my book but I am sure the cheap cost is what is attractive. When I was in High School the Deer Hunter 100 was popular and was $99 sometimes as low as $79 if you did a group buy. I think they normally had 1 MRF455 or 2SD1446.No one put one behind a 2950 though.

It is never good to have to turn down to make it work or the proverbial suicide switch.

I never got why people would by a powerful radio then stick a tiny amp behind it. It is always better to design a system from beginning to end with everything designed to work together.

Lester does a lot of those radio's where they have an 8 fet or 4 bjt amp built into the radio with a suicide switch so they can turn that amp off and run a smaller amp? Why?
 

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