Hi all,

I have updated the AGC schematic to help an easier insertion into the audio stage. I have added C115 and Volume1 potentiometer.

73

Gian, I7SWX

A scope could be a good investment if you are really serious about getting into electronics. ?The moderately good DS1102E is $360 on Amazon, though could go quite a bit cheaper if you go to something tethered to a desktop computer for display and control. ?Perhaps folks here have recommendations. ?I'd probably wait till I'm sure my interest holds before springing for one. ? Maybe you can talk some club member to show up at a meeting with their scope, you bring the Bitx40 with dummy load and schematic for a quick intro to what a scope can show you. ?But if we can someday get a few simple tools and procedures together, a scope should not normally be necessary for this sort of thing. ?

As mentioned before I also do not know of nor have I ever heard of a TXRX that had built in diagnostic tools such as you suggest. I suspect it is not a matter of cost so much as real estate and coding and accessories to connect to the 'tools'; probes, jumpers, etc. This in turn greatly complicates the 'boxing' of the radio adding the cost of connectors and jacke etc.? Anyone who is at all serious about experimenting with the BITXxx or other projects has or will need to start getting the basic instruments to look at circuits independently of and in addition to the BITX. Those not interested in more than operating the radio will not be bothered with more than needing a soldering iron and wire cutters/strippers. Adding the circuits you suggest to the main board serves only to complicate further the traces and layout for the beginner.

My opinion for what its worth.

PJH, N7PXY

I am going to keep working at it until I am sure it is working as good as it can. And do as many hacks as the hardware will stand. And learn all about it in the process. Actually work for a contact, and achieve it. This is what I like most about amateur radio. When I bought a MFJ-9240 cw transceiver I got board with it because there is no work involved with a boxed radio. I know I am getting behind with operating skills. But if I can bring a dead boxed radio radio back to life, I'll have a nice zombie station. And still have the money to spend on something that can't be made, or repaired. And I got the patience to do it.

Now, how helpful would an oscilloscope be at this point with the Bitx 40? I haven't needed it yet. I have only been into electronics 2+ years, and amateur radio 1+ year. And I will be checking into those easy to make tools Jerry has been talking about.

For those who wonder about the power supply. Power is what I started with, and I have plenty of beefy options, linear and switching regulators, and fuses. What I am using now is from a lcd monitor. A switching power adapter at 12.6V 4A that doesn't dip under load. And no line noise at these frequencies.?

Yea, I can't recommend this product for any other beginner. Just hams who already have working radios and like to tinker.

When I tried plugging a mini-USB programming cable into my new Raduino board, the plug would only go part way in. On inspection of the Raduino socket, I saw that there are two small strips of metal on the connector that ride along the top of the plug when it is inserted. On my unit, one of them had been caught by the edge of the mini-USB plug and was bent down inside the socket; this was preventing it from seating properly. After using a sewing needle point to pry the metal clip up, the plug now seats fully with a proper click. By the way I am using the short blue USB programming cable that came with one of the Arduino Nano clones from China, fits perfectly.

73, AL

Comparing two of my groups (this one and the Omnia SDR) I see that I DO have an upload button for the Omnia SDR group, but NOT for BITX20.

Something strange is afoot.?

--Neil W2NDG

radiokitguide.com

At $59, this will be going out to a lot of new hams worldwide. ?Like it or not. ?Some in rural areas without much of a support network or money for additional materials. ?The majority will just open the box and wire it up to be on the air. ? But others won't. ?We at least need better debug instructions. Much of the trouble seems to be in the final. ?Perhaps it's good enough to just post DC voltages around the three transistors there, as Raj did a couple months ago, ?Then what, they speak into the mike and measure the RF power out on their Bird wattmeter? ?That assumes an awful lot of stuff is suddenly working, and is not very concise. ?There should be a recommended way to inject a known signal into the final and measure the results. ?One way to generate a known signal level into the final might be to unbalance the modulator with a DC voltage and move the BFO down to where it's centered in the filter passband, as I have been recommending for CW transmisssion. ?(Ideally, the Si5351 is also used for the BFO.) ? That still assumes half the rig is working, though with an RF probe you could work your way from BFO to the IRF510. ?For example, varying the BFO frequency and inspecting the signal going into the diode ring mixer with the RF probe on transmit would verify that the crystal filter is working, and show the center frequency.

Alternately, a digital pin shorted to ground at power up on the Nano tells it to turn on the Si5351 B channel with a 7.2mhz signal, goes out through two series resistors to ground to attenuate the 7.2mhz to about 0.1v pk-pk for injection into the base of Q13. ?That's my RF signal generator, and it would cost about 4 cents for those two resistors. ? If I were to kit those resistors up with a nano, si5351, display, pcboard, a few other parts, autoinsertion, mailing, dealing with folks saying it doesn't work or didn't arrive, my price would be something like $50. ?Much better to simply put those two resistors down on the main board for an additional 4 cents. ?A schottky diode, cap, and a resistor or two would bring that up to about 10 cents, and provides the RF probe to dig through the final with. ?If it's on the main board, then everyone has it, and we can have a common set of instructions for how to go about debug, and can get measurements that should agree. ?With some work, this could be a real educational tool for the new ham rather than a frustrating puzzle.

The problem with the diode RF probe is it doesn't have much dynamic range. ?However, given how gain is distributed throughout the Bitx40 RF stages, we may not need much dynamic range. ?Especially if instead of 2 resistors, we have a string of 3 or 4 at the Si5351's B output, providing RF signals at various levels. ?Might consider having the AD8310 available as a $10 option, which would also give us a very very nice RF probe, a calibrated S meter, and sweeperino like capabilities.

The STM32 processor boards mentioned elsewhere are interesting. ?For about an extra dollar over the Nano, you should have enough power to send and receive some of the digital modes. ?The ADC resolution goes up to 12 bits. ?Counter-timers can directly count at 30mhz+ for a very nice freq counter. ?More communication channels for perhipherals. ?And enough flash that this debug stuff could get quite sophisticated without getting in the way.

Creeping featurism run amock. ?I'm ok with the Nano, and instructions for dead-bugging a diode RF probe. ?It's all Ashhar's call. ?

Jerry, KE7ER

?On Sat, Feb 4, 2017 at 10:56 pm, Todd K7TFC wrote:

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You probably won't like this but that code just isn't worth it, it's all about display.? You would be better deciding what you want and write your own or hack the display code about.??? Heck, use the Raduino code but rewrite for tft display,

Trouble is display coding for a tft display is not trivial compared to an lcd, even at 20x4 line lcd, that's easy !

Use Jacks rotary speedup for just one band use along with a simpler uncluttered tft display.? I know the filter stuff etc looks nice but it's not relevant to a BitX.

I can send you some code already done for tft's for you to look at and hack.? I use a 'basic' style of coding which is easy to read and follow.

One tip I find helps whenever you get code to look at, is to first segment the functions with the single comment and hashes (pounds). i.e.?? //#######################

That way you get a clear idea of program flow.

Better stop now as I suppose this isn't relevant to BitX group.
--
Rob G4NQX

Jack,

No, whenever I use an 8 bit display I automatically use a Mega for the pins.? I've done all sorts of tricks before to use Nano or Uno even,? but it's not worth the hassle as they are cheap enough.

Apart from my portable rigs I rarely try to shoehorn or miniaturise projects.? If I use smd for something they automatically become smaller anyway and in fact I like smd work.

The signal generator project uses a Mega, a 3.5inch 8 bit mcufriend display, a 4x3 keypad for direct frequency entry to suit either of the modules, si5351 or ad9850(1)

An ad8703 log amp as power out measurement. Future work is to add switched lpf's to cater for ham bands. (I've already done this on another project) Amp and output leveller for the ad9850. Then switched attenuators.

Features as now are,? single frequency - frequency sweep between ranges - power out measurement - select either rf board - frequency limits to suit.

I can send you the sketch if you want a look.

--
Rob G4NQX

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