Wednesday, September 21, 2016

Taking a Break!

Are you tired of seeing me post about my rigs?

9/28/2016 ~ Some recent updates

I have often said that most of my rigs are experimenter's platforms and the Junk Box Rig stands as an example of that approach. Everyday I look at possibilities for improvement --some changes are in the negative column but many are in the positive direction. Usually I employ the concept of TFMS when "peaking and tweaking" a rig. Oh almost forgot TFMS is an old timer term for Tune For Maximum Smoke. Well in this case when I had the rig outfitted to run 700 Watts out (Yes, Virginia, that is not QRP) I found that I got a report of splatter. One of those Flex Guys saw me pop up on his 60 inch color display and he reported I was very broad and splattering over onto other frequencies.
 
He was absolutely right! If you are running QRP at one watt --there may be splatter that is hardly noticed but magnify that 700 times and you will notice that your signal is broad and spilling over the normal bandwidth. A simple adjustment of the microphone gain can cure that problem. So out comes the scope and I was indeed flat topping and lowering the gain didn't actually impact the PEP output but did immeasurably improve the signal quality and cleaned up the spectral purity. For reference purpose a 1 watt signal is 30 dBm and a 700 watt signal is  58.5 dBm. So you will hear that very large elephant in the room!

Once I reduced the microphone gain, the Flex guy was  happy and so now I was happy too! WE have a responsibility as hams to put out the cleanest signal possible! I am now ever vigilant to not let that happen again. The positive side was that my PNP audio amp was no wimp and I had a gentle reminder about flat topping and splatter.
 
Rummaging through the junk box I found a 2SC2166 on a board and swapped out the 2SC2075.  Now 5 watts out is an easy goal. I also made a change on the driver board where normally the EMRFD circuit has a 2N3904 driving a 2N3866 but in my circuit I have a 2N2222 driving a BD139. In the emitter lead of the 2N3904 (my 2N2222) there is a 22 Ohm resistor to ground. I replaced that resistor with a 200 Ohm pot. The center wiper is connected to ground and the top lead is connected to the 2N2222. This enables me to adjust the stage gain. When I drive the 100 watt intermediate amp ahead of the SB200, I have it set so the Junk Box Rig outputs 1 watt as that is about the max level input to the intermediate amp. In the TFMS QRP mode (without any amplifiers) I can adjust that pot for 5 watts output from the 2SC2166.
 
On 9/27/2016 I made a 400 mile hop to San Francisco from my QTH near Los Angeles running 1 watt out on 40 Meters. Not a lot of signal strength but readable. But I must confess that 40M QSO's to the mid-west are much better running 700 watts!
 
Recap: Beefier RF Transistor, Watch for Flat Topping, Variable RF Output, QRP QSO's.
 
73's
Pete N6QW

9/21/2016 Revised Microphone Amplifier and plot. (See Comments)

Revised Schematic to limit the frequency response.

Output Plot of the revised shematic

Here is a chance to tell me what is on your bench and if you have attempted to build any of my projects.

73's
Pete N6QW

27 comments:

  1. In reply to the title, that is why I come here!! Now for some of my opinion, with attitude suppressed, my best effort anyway...

    You build so many radios, and each new one is the "best". Which on is nearest to your heart, which on is always hooked up to the amp, which one has 1 feature/performance that outshines the rest, is it the ultimate collection of the ultimate stages? While we are waiting for some reason why it's the best, it just seems the latest. And the next one will be the best also. But bring them on anyway...

    Still debugging the encoder...

    Ed KC8SBV

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    1. Thanks for your posting Ed -- that should get things rolling.

      I have two boxes of radios (rigs as I like to call them): A very, very large box contains all of the radios that worked only once, that never worked and sorta worked and the second smaller box contains the ones that actually work more than one time. Whenever a radio works more than once I am very joyful!

      Perhaps the most complicated radio I have ever built is my solid state version of the Collins KWM-2 which I call a KWM-4. The most clever one I built is the 20 Meter shirt pocket transceiver that is 2X2X4 inches. They all have some neat individual features but standing tall are the ones with the Si5351 PLL Clock Generator for the LO and BFO and the TFT color displays. Those tend to look apart from some of the more common approaches with LC oscillators and mechanical dials -- might I add a lot more stable and frequency agile.

      As homebrewer's today we have a wide range of inexpensive technology that can be embedded into our projects --what a great time to be a ham!

      73's
      Pete N6QW

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  2. Hi Pete,
    I for one really enjoy your blogs, I have built a LBS II which performed well and I have upgraded the audio to the NE5324 + LM380 and also the voltage regulator to 8 volts instead of 6 volts, so now its really hot. It is hard to believe the performance of so few transistors.....WOW.
    I have yet to box it up but I am still testing.
    As usual I am having some problems with the transmitter PA stability, which may possibly be the IF frequency.
    One thing I would like to see is an S meter.
    I also like JA2NKD's version of the TFT display. but it is for the AD9850.
    and I now prefer the SI5351.

    Anyway
    Don't stop. love what you do, Best regards...........Peter (GW4ZUA)

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    1. Hi Peter,
      Many thanks for your posting. JH8SST in an earlier posting provided an S Meter circuit he used with the Simpleceiver. That could be adapted to provide a gain reduction to the Rx RF amp stage. Or you could use an audio derived circuit which I have done and that could provide you a wiggling S meter, send me a direct email to n6qwham@gmail.com and I will share that with you.
      73's
      Pete N6QW

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  3. No, don't stop. I've got a sort of JABOM-Simpleceiver project going now using [a BOM] that I built as proof-of-concept things from the work of W1FB & W7ZOI. The cascode RF amp & product detector, NE5534/LM380 audio, and Si5351 stuff are all N6QW. You're in elite company, so keep showing off ... Paul AD0HQ

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  4. Definitely not. Like you, I enjoy homebrewing, so any advice, tips etc are welcome. Please keep it cming. I'm currently in the US and 10 x IRF510s turned up 30 minutes ago. Looking forward to getting home and melting some more solder!

    Charlie
    ZL2CTM

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    1. Hi Charlie,

      Many thanks for our posting. While you are at it scoop up some BD139's --they cost about 45 cents in US Dollars. I am impressed with their performance.

      73's
      Pete N6QW

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  5. Working on several projects at this time. Among them is a surface mount BITX, and a spectrum analyzer. Also did the layout for the I.F. strip for the very small transceiver I mentioned in an earlier e-mail. Have kind of been sidetracked with playing around with a new #D printer I picked up. Only thing I pulled out of the box of older projects is the SI5351 VFO board I did over a year ago, and going to use on the BITX project. Waiting to see what you pull out of your junk box next.
    DuWayne
    KV4QB

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  6. Hi DuWayne,

    Always nice to hear from you. 3D Printer --lucky you. There was a real find in my junk box -- really exciting --just need some time to whip some boards together.

    73's
    Pete N6QW

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  7. Hi Pete. Yes we ARE out here reading, watching, and learning from you. Your projects are always inspiring. But life happens so quickly I can't keep up with you.
    I have built the LBS and still working on my 20m ZIA (mostly) rig. Helping a friend of mine in Ore with his LBS too. Plans are in the works for a (mostly) general coverage Simpleceiver. What else is on the bench? The Arduino based antenna switch in last months QST. Might be part of a remote rig set up for when I'm traveling.
    So, yes, you are making a difference out here. I find myself checking your blog couple time a day to see what you come up with next. Keep up the good work.
    Jim
    wa7hrg

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  8. PS. I built the PNP mic amp just for kicks. It goes in the box of modules for later
    Jim

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    1. Hi Jim,

      Thanks for your two posts. Good show on the LBS rigs. Thanks also for checking the blog -- I try to keep it current but don't always succeed.

      BTW I have done some additional refinements on the pnp microphone amp. I now seem to get great comments on the audio -so I should get hot and share the latest schematic. The changes have additionally shaped the audio so it is more aligned with the filter pass band. I have also run about 20 different pnp transistors through the amp (have a socket on the board) and the design is such that just about any pnp audio transistor works!

      73's
      Pete N6QW

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  9. Hi Pete,

    After several years of entertaining myself elsewhere I've returned to dabbling in amateur radio, in part, because of reading your blog. I continue to check and am always pleased to find something new posted.

    I just yesterday finished building an NE5534/LM380 audio module. It's simply too useful to not have kicking around on the bench. I'm also in the middle of building, ugly style, a BITX40, which receives but is lacking a power amp, and a VU2ESE spectrum analyzer which is lacking an enclosure. (Pictures here: mikesflightdeck.com)

    So, please keep on posting, and we'll keep on reading.

    Thanks,
    Mike, N5GTF

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  10. Hi Mike,

    Thanks for your posting and for sharing what is on your bench. Glad to hear that you had a good build on the NE5534/LM380 audio amp. Kudos also on the BITX40 and Spectrum Analyzer builds. I am finding that at night 40M is good for coast to coast contacts and so once you get the BITX40 complete I am sure you will join the fray.

    There is just so much to build but not enough time. Sadly.

    73's
    Pete N6QW

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  11. Hi Pete,
    I keeps tabs on your blog, checking it every few days. Your projects are an inspiration and mostly I wish I could be as productive as you are in the limited time that I have.

    As far as on my bench, I'm stil working a lot with the Arduino and Si5351. Most of my efforts have been directed at building up my test equipment. I recently completed a GPS locked signal generator. I didn'y have any "Juliano Blue", so I used "Ed's Red" instead. Next projects are an antenna tuner and a step attenuator. I really want to experiment with your dual fet mixer designs.

    Thanks Pete! Keep it coming!
    73,
    Ed N3EML

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    1. Hi Ed,

      Ed's Red is good! May have to find some pastel red color and that will cover the next round of projects. Sounds like you have some neat toys on the bench. Stay in touch.

      73's
      Pete N6QW

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  12. Like the others, I enjoy following your blog and all of your projects, and appreciate you taking the time to share them! I know that I'm far from the only one who's been inspired to take up the iron after reading about one or another of your works-in-progress.

    It's always good to take a break and recharge the batteries - I've been doing the same thing for a couple of weeks, and now I'm looking forward to getting back to work on "The Planker" and a few other things I've got going.

    FB on the BD139. I have a feeling that might become the next "go-to" device!

    73!

    Steve N8NM

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  13. Like the others, I enjoy following your blog and all of your projects, and appreciate you taking the time to share them! I know that I'm far from the only one who's been inspired to take up the iron after reading about one or another of your works-in-progress.

    It's always good to take a break and recharge the batteries - I've been doing the same thing for a couple of weeks, and now I'm looking forward to getting back to work on "The Planker" and a few other things I've got going.

    FB on the BD139. I have a feeling that might become the next "go-to" device!

    73!

    Steve N8NM

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  14. Hi Steve,

    Thanks for your post. There are just so many projects but not enough time. I am really impressed with the BD139 --about $0.50 a piece and a lot of goodness.

    73's
    Pete N6QW

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  15. Hi Pete,

    As always, I think your information and radios are great. They keep us all inspired to keep building. Quick question on the mic amp above. I noticed you used a 2n4403, do you know how it would perform with a 2N3906? I have a ton of those in SMT and it would make a very compact amp. I guess I should break out my computer and analyze it myself. Anyway, thanks again for sharing all of your knowledge and designs. Please keep on melting solder!!!!

    73's

    Dean AC9JQ

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  16. Hi Dean,

    It will work FB with a 2N3906 and it is hard to tell any difference (if any) as I actually switched the simulation to the 2N3906. Keep in mind the 2N3906 in surface mount is good for 200 MW of dissipation and has an Ft of 300 MHz. For an audio application like this you need maybe an Ft of 1 MHz and if it has 50 MW of dissipation we are good. In fact I put a socket on the mic amp board and have a bag of really old PNP transistors (very likely a lot of germanium units) and I just cycled them through the circuit. Virtually all of them worked except for the two dead ones that didn't work too well.

    If you are looking for an application for those surface mount 2N3906's then do an internet search on the NE592. This interesting device has been used as a linear driver for a pair of leaded 2N3906s used in a push pull RF amp stage that puts out 1.5 watts on 20 Meters. I would easily bet that your surface mount 2N3906's because they have a 200 MW dissipation versus the leaded at 625 MW could easily deliver 0.5 watts of RF to drive an 2SC2166 to 5 watts out.

    Oh Oh!!! Hope I haven't let a cat out of the bag for an upcoming project which is now in the "noodling" stage.

    73's
    Pete N6QW

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    1. The NE592 looks like a really interesting device. Possibly many applications for it!?

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    2. Hi Dean;

      Simply said --"Stay Tuned!"

      73's
      Pete N6QW

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  17. Hi Pete,
    I enjoy reading your blog so keep it up!
    Right now I am studying your pre/audio amplifier from your Simpleceiver project.
    I am going to try out your design in a new rig I am building.
    I also enjoy listening to you and Bill talk about what's on your workbench in the SolderSmoke podcast. Hope you are having a fine Left Coast morning!

    Al, N8WQ

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  18. Hi Al,

    Thank you so much for your posting. That audio amp is currently in five of my transceiver projects and so I guess you could say it has become my standard building block.

    If all goes well Bill and I will be doing SS190 tomorrow (9/24) and hopefully we will continue to keep the podcast listeners amused as we explain how we frequently smoke parts, solder our fingers together and lose sleep over why a circuit won't work. Thanks for being a podcast listener and putting up with our banter.

    Let us know how your project progresses.

    73's
    Pete N6QW

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    1. Looking forward to it! Anyone who's ever built anything can relate to those experiences, but we only seem to talk about the stuff that ends up in the smaller of the two boxes.

      73 - Steve N8NM

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