Thursday, February 09, 2012

Now output

Everyone who commented to my last post about the lack of output from the Kits and Parts RF amp felt that the problem had to be the QRPer's curse - the toroid inductor. Normally I don't have a problem with toroids, but when they are so small that your thumb obscures the whole core while you are holding it, never mind winding it, they are not the easiest of components to work with.

So I gritted my teeth, tried to forget the hour I'd spent yesterday wrestling the thing into position, and yanked it out. One of the wires broke off in the hole leaving nothing to grab on to. I was unable to clear the small plated-through holes in any case. What I was able to do was melt the solder enough to push some bare wire through, creating "pins" that I could solder to. I twisted together the two wires that are connected so I had three ends to solder to the three pins I created. The toroid now stands up on the board a bit but it was easier soldering to the pins than trying to get four thin wires to go through four holes simultaneously. To my joy, on applying power and RF the power meter showed output.

I'm getting about 150mW if the amp is supplied with the recommended 8V, and just about 200mW from a 9V supply. That's only about 10dB of gain, a bit less than expected but probably enough given that the Propeller does not generate the purest of signals. The WSPR beacon has already been spotted a few times in Germany. But the 2N5109 runs a bit hot to the touch so I'll have to QRT until the heatsink I ordered arrives. In the meantime I still have the LCD UI board to assemble and play with.

8 comments:

Sue said...

Well done Julian. Glad you got success with the project. Great blog and always full of interesting stuff.

73s

Peter g3OJV

Anonymous said...

Glad to see that you got your amplifier sorted.

Upon re-reading my previous comment I noticed that I said 'bipolar' when in fact I meant bifilar - and I did it twice!

I checked wsprnet.org to see if I had copied your WSPR beacon - I had not. Lately I have just been setting up WSPR to receive and frequency hop. The other day noted an report decode where I had copied an Australian WSPR beacon on 160 meter - twice, ten minutes apart. Interesting stuff this.

cheers, Graham ve3gtc

Julian Moss said...

It wasn't on for very long, Graham. Someone warned me to fit a heatsink to the transistor and I didn't want to pay UK prices so I'm waiting for some to come from Hong Kong. Not that I'll probably ever use more than one!

Julian Moss said...

Thanks for the comments, Peter. It must be 20 years since I was last in your shop. I seem to recall that you are mostly interested in QRP now and operate bicycle mobile from Hockley Woods. If I'm feeling more fit in the summer I might get a battery assisted adult trike and do some bicycle mobile myself. Pedal power is all I'll be allowed to use on the roads as it's unlikely I'll ever get my driving licence back due to what I've got.

mrbillmac said...

It's always nice when a device decides to work!
What exactly was the problem? Bad soldering on the toroid?

Bill N5AB

Richard G3CWI said...

Julian, I would be happy to build the UI board for you if that would be helpful. Regards Richard G3CWI.

Julian Moss said...

Thank you, Richard. I have just completed it. I haven't tested it yet, but there were no toroids for me to mess up!

Julian Moss said...

... except that I just did. I soldered an 8x2 box header to the main board and an 8x2 open male header to the LCD board. Then I wondered what the four 4x1 female headers were four. This is the problem, I just don't think.

Now to try and get the open header off the LCD board. Sigh...