Tuesday, January 26, 2016

Simpleceiver ~ Part 27

Some light at the end of the Tunnel!

 
My XYL has been steadily improving and hopefully we expect her release from the nursing facility in about a week or two. That means I can get back to heating up the iron and continuing with this project. I have not had any comments regarding those who forged ahead and started work on the transmitter stage and so that either means there is a complete loss of interest or the project is dead. I sure hope not as I think given what I have observed from the receiver performance this project could rival some of the currently popular homebrew radios.
 
The basic transmitter board had 4 elements including the microphone amplifier, the carrier oscillator, the SBL-1 and the IF Amp/Filter block. The output is of course at 12.096 MHz which is the filter frequency and just so we all are on the same page the Zout is 50 Ohms. The block which will follow the basic transmitter board is the frequency translation board which performs some very specific functions. The 12.096 MHz SSB signal must be mixed with the local oscillator so that one of the resultant frequencies is on the band of choice. From our earlier discussions the mixing process results in sum and difference frequencies and a second effect is depending whether the Local Oscillator is above or below the filter frequency there may be a sideband inversion. We certainly do not want the case where we have the receiver on LSB and the transmitter is on USB.
 
The Simpleceiver receiver used an LO at 5.0 MHz so that the one of the resultant frequencies is in the 7 MHz range. Here it is the IF- the LO result we want (12.096 - 5.096 = 7.0). But there also is a component where you have 12.096 + 5.096 = 17.192 MHz which must be filtered from the output. So following our frequency translation we must have another Band Pass Filter centered on 7.150 MHz so that only the subtractive mix is in the output.  Given that we will also be using an SBL-1 for the frequency translation there will be a need for several amplifier stages to boost that signal to something directly usable on 40 Meters. A J310 based Dual Gate MOSFET would serve this purpose nicely for the 1st stage of amplification. Thus we can actually use the Simpleceiver RF amplifier stage as a circuit block following the Band Pass Filter. Again we stated that many of the circuit blocks built for the receiver could be simply reused for the transmitter and so this is what we will do.
 
I hope in the next week to post an amplified block diagram of the transmitter circuits that will include the follow on boards to the basic transmitter.
 
 
73's
Pete N6QW

6 comments:

  1. The interest in the project is not dead. We're busy taking care of other stuff in your absence. You and Bill have managed to get me off the fence and start working on my license. Once I get my license I'll be returning to these blog posts to build my rendition of the Simpleceiver.

    This leads me to something else I have procrastinated on for far too long. I owe a big "Thank You" to you and Bill. I have gained an understanding about how receivers work from following the blogs and podcasts than I had from school. (In school I was focused on power, power supplies, and audio and under 20 kHz. signals.)

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    1. Hi David,
      Many thanks for your email. Hopefully heating up the iron is very close in time. Glad Bill and I have been a help to you. Good luck on obtaining a license.

      73's
      Pete N6QW

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  2. Hi Pete
    No interest is not dead. We have all just been holding our breath right along with you and the xyl.
    Besides I'm still trying to 'tame" the transmitters in the LBS and ZIA rigs.
    Jim
    Wa7htg

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    1. Hi Jim,

      Good news --the XYL will be released from the nursing home this weekend. So give me about another week and I will be able to "heat up the iron".

      Thanks for your concern.

      73's
      Pete N6QW

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  3. I'm still hanging in there as well, Pete! I've been slowly collecting every bit of SI5351 code I can get my hands on from any and all sources available. Going to see if I can save a few bytes here and there and make a generic library based on all of it, where all a person has to do is #define stuff for a particular setup, such as #define SI5351; #define TFT, and so forth. Hope I can squeeze it all into one sketch. Wish me luck!

    Also, I have been slowly collecting the parts for building a lot of the LBS modules. Unfortunately, just had two relatives die in the past 2 days, so now I'm going to be
    set back a bit. Should be back on track by next week.

    73,

    Randy AB5NI

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  4. Hi Randy,

    Condolences on the passing of your relatives. At times life does get in the way of our beloved hobby.

    Great idea about the Si5351 code --that indeed would be a benefit to the overall ham community. Good Luck.

    Pete

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