40m QCX+ low power question #problem #qcx40 #toroid #40m #alignment


Larry VE7EA
 

12.3 W out at 13V. Wow. Most are lucky to get 5W out at that voltage. How exactly are you measuring RF power out? I suspect your measuring device is not reading correctly, or you are measuring RF power out with the wrong type of device..


Ronald Taylor
 

An indicated 12.3 watts on a 40 meter QCX is an invalid indication since this is a 5 watt radio and has never been shown to deliver more than 6 or 7 watts maximum. Something is wrong with your meter or your measuring technique or you calculations if you are calculating from measured voltages. 

If you are asking what RF voltage should be on the BNC connector, with a 50 ohm dummy load there you should see something around 40 volts peak to peak there when running at 12 volts. That would be 4 watts. If you are measuring peak power there as with the detector on the QRPLabs dummy load, then you would see about 20 volts peak for the same power. 

Since you indicated in this thread that this is the only remaining issue does it mean you resolved the low receive volume issue in the other thread? 

Ron

On Thu, Jun 23, 2022 at 19:13 kf7rcm via groups.io <kf7rcm=yahoo.com@groups.io> wrote:
Got it finished off and the only problem is I get an indicated 12.3w on 13v. If I turn my power supply all the way up (16.5v), I get an indicated 13.2w. I've done everything short of rewinding L1,2 and 3. I am willing to settle for the 12.3 at this point and hook up the amplifier once I am finished with that.
Question is, has anyone rewound L1,2 and 3 in an act of desperation? And if so, did it do any good?
Bonus question: anyone know what the voltage should be at the BNC?


kf7rcm@yahoo.com
 

Yep, kinda blew it on that last post. Wrote it fast with a headache. I have since deleted it and reposted a corrected version. Audio solution was carefully checking and resoldering a couple places. I will probably be taking the post down soon. I don't have an oscilloscope but will have access to one soon. 
I'm not getting anything like 40v, more like 20v. 
Corrected numbers: @ 13.3v= 2.35w indicated, 16v=3.37.


Ronald Taylor
 

Ok. Well every 40 meter QCX/+/Mini I’ve worked on has easily hit the design power with the specified number of turns and just a little squeezing and spreading to make it work. Usually L3 is spread all the way out and L2 is compressed most of the way in. You shouldn’t have to rewind them unless you don’t have the correct number of turns. Spread the windings on L4 as well. 

Good luck …. Ron

On Thu, Jun 23, 2022 at 19:58 kf7rcm via groups.io <kf7rcm=yahoo.com@groups.io> wrote:
Yep, kinda blew it on that last post. Wrote it fast with a headache. I have since deleted it and reposted a corrected version. Audio solution was carefully checking and resoldering a couple places. I will probably be taking the post down soon. I don't have an oscilloscope but will have access to one soon. 
I'm not getting anything like 40v, more like 20v. 
Corrected numbers: @ 13.3v= 2.35w indicated, 16v=3.37.


Colin Christie <colincolin30@...>
 

Hi All,
 when I did my adjustment for the 40m version PA , I got at first 700 millwatts , very disappointed........move windings on L3 first......2.5 watts  L1 and L2  got  4.3 watts at 11 volts.
I am happy 


73 Colin vk2jcc

On Fri, 24 Jun 2022 at 13:21, Ronald Taylor <wa7gil@...> wrote:
Ok. Well every 40 meter QCX/+/Mini I’ve worked on has easily hit the design power with the specified number of turns and just a little squeezing and spreading to make it work. Usually L3 is spread all the way out and L2 is compressed most of the way in. You shouldn’t have to rewind them unless you don’t have the correct number of turns. Spread the windings on L4 as well. 

Good luck …. Ron

On Thu, Jun 23, 2022 at 19:58 kf7rcm via groups.io <kf7rcm=yahoo.com@groups.io> wrote:
Yep, kinda blew it on that last post. Wrote it fast with a headache. I have since deleted it and reposted a corrected version. Audio solution was carefully checking and resoldering a couple places. I will probably be taking the post down soon. I don't have an oscilloscope but will have access to one soon. 
I'm not getting anything like 40v, more like 20v. 
Corrected numbers: @ 13.3v= 2.35w indicated, 16v=3.37.