Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Small Wonders SW+20 help  (Read 5279 times)
N6PG
Member

Posts: 55




Ignore
« on: May 12, 2014, 02:38:54 PM »

Any experts out there? I can only get 1.4 watts out with the power setting pot full clockwise and turns on L1 bunched up close together. I had the idea I was going to up the power to 3 watts, but I'm tempted to just leave well enough alone at 1.4 watts...
Thanks and 73,
Scott N6PG
Logged
K8AXW
Member

Posts: 3860




Ignore
« Reply #1 on: May 12, 2014, 03:43:47 PM »

Sumthin ain't rat! 

You need to go through the transmitter part and see if you have an incorrect component, or one out of specs, installed.  You should be able to get the 4w out. 

If you want 1.4w that's fine but in this case you're getting it because you have a problem, not because you just want it.

Fix the problem and then screw the power down if you wish.

Logged
W1JKA
Member

Posts: 1716




Ignore
« Reply #2 on: May 13, 2014, 02:38:52 AM »

From a non expert: Max. output on the SWL 20+ series is 2- 2.5 watts at 13.8 volts (I get 1.5-1.7 w with a 12v battery). First thing to check is your PS output  voltage and second, get your magnifying glass out and check for hair thin solder bridges along with the standard cold joint check. Otherwise do the individual circuit/component test point checks per construction manual. All my previous QRP kits I've had to check at least 3 times and often more just to clean up solder bridges. BTW your way ahead of the normal kit builder's curve, at least you got it to power up and got some output.
« Last Edit: May 13, 2014, 02:46:57 AM by W1JKA » Logged
N6PG
Member

Posts: 55




Ignore
« Reply #3 on: May 13, 2014, 04:10:57 AM »

From a non expert: Max. output on the SWL 20+ series is 2- 2.5 watts at 13.8 volts (I get 1.5-1.7 w with a 12v battery). First thing to check is your PS output  voltage and second, get your magnifying glass out and check for hair thin solder bridges along with the standard cold joint check. Otherwise do the individual circuit/component test point checks per construction manual. All my previous QRP kits I've had to check at least 3 times and often more just to clean up solder bridges. BTW your way ahead of the normal kit builder's curve, at least you got it to power up and got some output.

Thank you! 12v ps! That's probably it. I'll still go through it and and check components and the solder.
Regards,
Scott N6PG
Logged
W1JKA
Member

Posts: 1716




Ignore
« Reply #4 on: May 13, 2014, 05:05:00 AM »

Re: N6PG

I also forgot another common cause of low output on these rigs, if you haven't already done so,  re melt/solder or other wise check the 2 end leads of your L1 coil where they go through the pc board. Some times the insulation layer doesn't get completely scraped off the wire at initial installation. This from experience.
Logged
WB0FDJ
Member

Posts: 144




Ignore
« Reply #5 on: May 13, 2014, 10:14:55 AM »

FWIW: from the SW+20 manual, as written by it's designer:

"The component values in the PA stage were designed for maximum efficiency at 1.5W out. The SW+ will deliver considerably more, but please be aware of the following:
• The higher the output power, the more heat is being generated by the PA, and this translates into ‘driftier’ performance in the local oscillator.
• There’s a possibility of instability in the driver (Q4/Q5) stage with R24 set to maximum. IF THE SIDETONE SOUNDS RASPY OR V ANISHES ENTIREL Y , reduce the R24 setting. If your SWR meter reading is acting inconsistent, that also points to an instability."

Doc WB0FDJ
Logged
N6PG
Member

Posts: 55




Ignore
« Reply #6 on: May 13, 2014, 05:27:38 PM »

FWIW: from the SW+20 manual, as written by it's designer:

"The component values in the PA stage were designed for maximum efficiency at 1.5W out. The SW+ will deliver considerably more, but please be aware of the following:
• The higher the output power, the more heat is being generated by the PA, and this translates into ‘driftier’ performance in the local oscillator.
• There’s a possibility of instability in the driver (Q4/Q5) stage with R24 set to maximum. IF THE SIDETONE SOUNDS RASPY OR V ANISHES ENTIREL Y , reduce the R24 setting. If your SWR meter reading is acting inconsistent, that also points to an instability."

Doc WB0FDJ

Yes. Thank you. I was going to do a mod that supposedly fixed that instability at increased power levels. Ultimately, I decided 1.5 watts is fine, but I want to make sure I didn't miss something... Since I can't even get 1.5 watts. I'm hoping it's the PS, but I can't put 13.8 v to it until I get home.
73,
Scott N6PG
Logged
WB0FDJ
Member

Posts: 144




Ignore
« Reply #7 on: May 13, 2014, 09:53:29 PM »

Scott

I didn't mention: I have two SW+ rigs, on 20 and 40 M. I just had them out for the "spring tuneup". I can squeeze more than 2 W out of either of them but followed the suggestion to back off a little so I'm seeing about 1.8 W-2.0 at 13.8 V. On my 12 volt battery pack, which is how I run mine nearly all of the time, I see 1.5 W more or less. I've (like many others) have made a lot of contacts at those power levels. Interestingly this is the same PO I see from my old HW-8!

Doc WB0FDJ
Logged
N6PG
Member

Posts: 55




Ignore
« Reply #8 on: May 16, 2014, 03:26:59 PM »

Thank you for all of the advice!  I got home and put 13.8 v on it and the output was still low.  I have it in a tight enclosure, so I really had to decide if I wanted to unsolder a bunch of connections to get the board out.  I finally decided that I couldn't stand something not being right.  In the plans Dave Benson had identified the voltage to look for in several points.  I found the input to the PA was low and tracing it back from there I was able to find that the transformer I wound didn't have enough windings on the primary!!! 

This kit has been great for me.  I've had a lot of fun, and it's the first time I've every been able to troubleshoot a transmitter!  The supporting documents with this kit are great, and I totally understand what a loss it is that Dave isn't making these kits anymore. 

So... It's working!  I dialed it back to 1.5 watts.  Now on to the NorCal50A...
Scott N6PG
Logged
K8AXW
Member

Posts: 3860




Ignore
« Reply #9 on: May 16, 2014, 05:58:09 PM »

Scott:  GREAT!!  But, what was the power output after you rewound the transformer and dialed it back to 1.5w ?
Logged
N6PG
Member

Posts: 55




Ignore
« Reply #10 on: May 17, 2014, 07:34:22 AM »

Scott:  GREAT!!  But, what was the power output after you rewound the transformer and dialed it back to 1.5w ?

I didn't check the potential max power possible. I used a 12v battery, and not 13.8v, when working on it on the bench.  I somehow read the 8" as 8 turns... When it should have been 10 turns. I ordered a small heat-sink for the PA transistor, so I might increase power a bit if it doesn't become unstable.
Logged
K8AXW
Member

Posts: 3860




Ignore
« Reply #11 on: May 17, 2014, 08:12:09 AM »

Copy that.  I was curious as to the "new power output" with the rewound transformer.  I find it interesting to know what difference 2 turns meant. 

I also thought after re-installing the transformer and keying the rig, you noticed the increase in power and what it was......before you dialed it down to 1.5w.




Logged
N6PG
Member

Posts: 55




Ignore
« Reply #12 on: May 17, 2014, 10:09:44 AM »

Copy that.  I was curious as to the "new power output" with the rewound transformer.  I find it interesting to know what difference 2 turns meant. 

I also thought after re-installing the transformer and keying the rig, you noticed the increase in power and what it was......before you dialed it down to 1.5w.

I backed off the potentiometer before reapplying power after I added the 2 turns.  The watt meter I have gives a voltage, and I need to convert that to get the watts, so it's a bit cumbersome and not so quick to just note the power.  This lit the fire!  I haven't even built the NorCal40A and I'm looking at the K-1!!





Logged
K8AXW
Member

Posts: 3860




Ignore
« Reply #13 on: May 17, 2014, 06:10:01 PM »

Quote
This lit the fire!  I haven't even built the NorCal40A and I'm looking at the K-1!!

I can understand and appreciate that!!  I'll never forget the first Heathkit that I built nor will I forget the DSW-20-II.  I've never seen such performance from such a little box!

Take your time and relish every solder joint; every component you install. 
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!