HobbyPCB.com

Built by Hobbyist for Hobbyist!
It is currently Wed Aug 21, 2019 1:21 pm

All times are UTC - 5 hours




Post new topic Reply to topic  [ 20 posts ]  Go to page Previous  1, 2
Author Message
PostPosted: Wed Aug 07, 2013 6:24 am 
Offline

Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
Hi Joel,

Thanks for the pictures, looks like a nice build.

When you power up the board only apply 12V (actually 13.8V) to the 12V pin. Leave the 5V unconnected. If you measure the voltage at this pin you will see 0V until the PTT line is grounded then you well see 5.1 to 5.2 volts.

To set the bias, place a ammeter in line with that 12 Volt supply, turn VR201 fully CCW (it's a 25 turn pot so lots of turns are needed). When you power up the 12V supply you should see 0 mA.

Ground the PTT line, the relay should energize and the current will increase by the current required for the relay and the current flowing in the bias supply.

Note the amount of current that's flowing, turn VR201 CW until the current increases by 400 mA.

Unground the PTT line and the relay should de-energize and the current will return to 0mA. The amp is ready to go.

If you only plan to use the amp for CW you can use a lower current and achieve better efficiency but for SSB, PSK and other linear modes you need at least 400 mA of idle current to maintain linearity.

Don't forget the heatsink, there's alot of idle current/power and the MOSFET will heat up quickly.

73's
Jim WA2EUJ


Top
 Profile  
 
PostPosted: Fri Aug 09, 2013 6:54 pm 
Offline

Joined: Mon Jul 15, 2013 12:23 pm
Posts: 74
All finished except for the smoke test, I will let everybody know how it turns out.

[img][IMG]http://i222.photobucket.com/albums/dd4/caulktel/photo2_zps2feed1f6.jpg[/img][/img]


Joel
KB6QVI


Top
 Profile  
 
PostPosted: Sat Aug 10, 2013 9:35 am 
Offline

Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
Looks very professional, at least the mod is under the PCB.

Jim.


Top
 Profile  
 
PostPosted: Sat Aug 10, 2013 5:27 pm 
Offline

Joined: Mon Jul 15, 2013 12:23 pm
Posts: 74
Thanks Jim,

It passed the smoke test! I have the bias current set at 400MA above the idle relay current of 26MA for a total of 426MA. With 700MW of drive I get about 4.5 watts out. Should I remove the attenuation network to get the 10 watts out? I chose 1 DB attenuation for .6 watts drive level thinking that would be close to what I would actually be driving it with. The output waveform looks real clean at 4.5 watts, but I would really like more power out than that. Any ideas?

Joel
KB6QVI


Top
 Profile  
 
PostPosted: Sun Aug 11, 2013 12:23 am 
Offline

Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
You should be able to get closer to 10W so try eliminating the input attenuator, increasing the bias and try to see of the output filter is attenuating the signal. Since, as far as I know, you are the first to build one of the new drivers you can send it here and I'll check it out and see what's up.

73's
Jim WA2EUJ


Top
 Profile  
 
PostPosted: Sun Aug 11, 2013 1:42 pm 
Offline

Joined: Mon Jul 15, 2013 12:23 pm
Posts: 74
I'll try your suggestions Jim and get back to you. Thanks.

Joel
KB6QVI


Top
 Profile  
 
PostPosted: Mon Aug 12, 2013 11:17 am 
Offline

Joined: Mon Jul 15, 2013 12:23 pm
Posts: 74
Jim,
I removed the attenuation network and the RF output came up a little, about 300MW for a total of 4.7 Watts. I increased the bias a little with no change in output. I also bypassed the LPF with no noticeable change in output, so I'm out of ideas. Would you like me to send it to you? Let me know.

Joel
KB6QVI


Top
 Profile  
 
PostPosted: Tue Aug 13, 2013 6:07 am 
Offline

Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
Hi Joel,

I just built one for the workbench to test HR50's and it put's out a solid 10W on all bands. I'll be happy to take a look at yours. Send me an email WA2EUJ@arrl.net and I'll give you shipping instructions.

Jim


Top
 Profile  
 
PostPosted: Thu Aug 29, 2013 7:15 pm 
Offline

Joined: Mon Jul 15, 2013 12:23 pm
Posts: 74
Everything is working great, a solid ten watts out on 40 meters with about 600MW drive. I don't know what it takes to heat this amp up, last night i got into a rag chew with another Ham for about 45 minutes and it never got warm enough to even notice. All in all, I'm very happy with the amp, thanks Jim. Here is the final pictures of it in the cabinet: [img][IMG]http://i222.photobucket.com/albums/dd4/caulktel/image-1_zpsc69bbb10.jpeg[/img][/img]

Joel
KB6QVI

P.S. I will try to get a review up on EHam, but I'm not very good at that sort of thing.


Top
 Profile  
 
PostPosted: Fri Aug 30, 2013 6:55 am 
Offline

Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
Hi Joel,

Thanks for being the beta test for the new 10W amp. Look like a nice compact unit that you have there and there's probably lot's of hams running QRPp equipment that would really like to have something similar. You should consider writing a QST article. I think you get $100 per page, you'd starve if it was your life's work but it'll pay for you amplifier!

73's
Jim WA2EUJ


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 20 posts ]  Go to page Previous  1, 2

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group