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uBITX working, question about power, PTT pop, LOUD headphone output
#ubitx
开云体育Same here. Oh well, a little software tweak here and there... Still, the basic performance is nice and clean. My first superhet simple radio. Like the KK7B R2, I like the overall sound without AGC, though some hard limiting would be good to protect one's ears from sudden loud signals with the gain up! John K0JD On 12/20/2017 23:06, Kelly Jack wrote:
Correction. PTT does nothing but the encoder button only exits the menu. The change to CW tone does not take. |
开云体育On looking at the schematic... I think the solution might be simpler: use a high-value resistor to keep the DC level of the capacitor at the output of Q70 at ground. I saw this referred to a while back in an audio mixer circuit as "zero point switching" to avoid pops. Let me see what I can kludge in without messing up the beauty of the board :-) John K0JD On 12/20/2017 20:31, Kelly Jack wrote:
Hi all |
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Gordon Gibby
开云体育?John -- there are two capacitors in series at that point in the receiver --- are you talking about using a resistor to keep the center point at ground?? ?
I'm interested to see if this will work, because when the driving transistor is suddenly eneregized, I think you're STILL going to see a spike AC signal propagate through the two capacitors unless you roll off the high frequency response significantly.?
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Gordon
From: [email protected] <[email protected]> on behalf of John Seboldt K0JD <k0jd-l@...>
Sent: Thursday, December 21, 2017 12:21 PM To: [email protected] Subject: Re: [BITX20] uBITX working, question about power, PTT pop, LOUD headphone output #ubitx ?
On looking at the schematic... I think the solution might be simpler: use a high-value resistor to keep the DC level of the capacitor at the output of Q70 at ground. I saw this referred to a while back in an audio mixer circuit as "zero point switching" to avoid pops. Let me see what I can kludge in without messing up the beauty of the board :-) John K0JD On 12/20/2017 20:31, Kelly Jack wrote:
Hi all |
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But Q70 gets powered up on RX, and Q6 gets powered up on TX.
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That power switching is really disruptive. Might leave them both powered up, then the DC bias resistor should work fine, if you somehow kill the microphone But given what we got, I'm leaning toward the FET clamp on rx audio. Reducing the size of C52 on Q70 might help get the pop over with quickly. In addition to the audio pop in the phones on rx, the uBitx may have the Bitx40's? carrier burst on tx.? ? ??/g/BITX20/message/33707 Allard has been fixing some of this with delays in firmware. If we can get by without a special interrupt library in the code, the sketch will be much easier to understand, add features to, and port to other processors.? So I'd prefer to fix the rx pop and tx burst with hardware hacks. Jerry, KE7ER On Thu, Dec 21, 2017 at 09:21 am, John Seboldt K0JD wrote:
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开云体育If you put this on the M1 side of the circuit, I think the sidetone problem will be solved. Quickly pull output of Q70 to ground before the relay switches away the input to the final audio stage. Will work on this. On 12/20/2017 20:31, Kelly Jack wrote:
Hi all |
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I tried the resistor to ground between the two caps - it didnt work for me.
Two back to back diodes across the speaker terminals reduced the pop quite a bit but its still there. Another option is to take the sidetone off the raduino by bending the headrr pin out, duplicate the lpf for the sidetone offboard and put the muting circuit between the volume control and the board as per the original. Not elegant but preserves the board. Would also allow for extra pot to control sidetone vol independently which is too loud for me on my rig. I see there is a tone vol library which may work in software. A few things to work on. The carrier burst is there also as seen on my other rigs bandscope but not as large as the bitx40. Im not going to worry about it for the moment. Regards Simon VK3ELH? |
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The tone is generated by a counter timer inside the ATMega328p on the Nano.
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Tone volume could be controlled by setting the duty cycle of the outgoing square wave. Harmonic content will vary drastically, but the RC low pass filter on the uBitx should mostly cure that. On Thu, Dec 21, 2017 at 04:25 pm, Kelly Jack wrote: I see there is a tone vol library which may work in software. |
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Hi all,
I've been working on a pop mute solution which also deals with the loud CW sidetone issue that some of the earlier units may have experienced. Firstly some credit, this comes straight from the Hans Summers QRP Labs QCX transceiver which has a TX mute circuit that mutes the receive just before the last audio stages. Interestingly the sidetone is injected before the mute but because their is enough leakage for the sidetone to get through. So I had heard that some of the early uBitx units had 1K for R250 which made for a very loud sidetone. R250K was 220K on my uBitx so when I put the mute circuit in, the sidetone was barely audible with a dummy load connected. So I swapped out the 220K for a 1K and sidetone volume is at a comfortable hearing level. The pop on the transition from receive to transmit is completely gone and on the transition from transmit to receive there is a small low frequency thump with headphones on.? With the speaker the thump was not noticeable. An added benefit for me was that due to the lack of pop on the receive to transmit transition, the timing on my CW keying was not thrown out, something which occurred a bit when I was keying with the pop present. The circuit has four parts; 2n7000 mosfet, 120K resistor, 220n cap (I started out with 100n and increased to 200n) and 1n4148 diode. Drain to wiper of vol pot, source to ground (I soldered it point to point on the pot terminals). The other three components all connect to the gate and the other ends as follows: Cap from gate to ground (again on the pot terminals), resistor to the T/R line (via a wire, I used a DuPont cable and put the female end on the protruding pin of the nano that controls the T/R line). Diode goes in parallel with the resistor with cathode at the mosfet end. 73 Simon VK3ELH |
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Hi Jim,
I also got the kit from India the other day. I have built it in an ex mobile vhf rig aluminium alloy case. I am not satistied with the transceiver due to the drawbacks you mentioned. I like to operate CW but hand keying is impossible due to sending errors which I get whenever I try to pound brass. Polished also the contacts and tried different keys, too. Nothing helps. Haven't tried SSB because I bought this rig for portable CW operation. Tonight I even updated the fimware. Got some new items to the menu but CW is still miserable in spite of the update. How about "hard" keying of the transmitter? Carrier on all the time and using a PNP transistor as a switch. No hazzle with processor loops or similar. 73 Kai OH3WE Lahti, Finland. |
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The problem with CW on the stock uBitx is not enough pins into the Raduino to do?
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everything we want it to do.? The uBitx uses a single pin for hand key, paddle dot, and paddle dash, those all drive that one pin through a resistor network, the Nano reads an analog voltage and decides which is happening.? Contact resistance can quickly get in the way of this scheme. Here's the code, down in ubitx_keyer.ino? from?? ################################### //reads the analog keyer pin and reports the paddle
byte getPaddle(){
? int paddle = analogRead(ANALOG_KEYER);
?
? if (paddle > 800)? ? ? ? ?// above 4v is up
? ? return 0;
?
? if (paddle > 600)? ? // 4-3v is dot
? ? return PADDLE_DASH;
? else if (paddle > 300)? ? //1-2v is dash
? ? return PADDLE_DOT;
? else if (paddle > 50)
? ? return PADDLE_BOTH;? ? ?//both are between 1 and 2v
? else
? ? return PADDLE_STRAIGHT; //less than 1v is the straight key
}
###########################
Here's three possible solutions: There has been new firmware developed that frees up digital pins by moving from the parallel LCD display to an i2c version of the LCD, so can use separate digital lines for paddle and handkey. Perhaps someone else here can recommend a specific firmware version that works well for CW use. Use a single digital pin, the firmware treating it as a hand key, could be driven from an electronic keyer. But I believe the pin will have to be moved, as A6 is analog only. Or use the stock firmware, but drive the single analog line with a small circuit board using 2n7000 FET's, taking in separate digital lines from your paddle or hand key.? ? ?/g/BITX20/topic/7709984#37057 ?/g/BITX20/topic/7791181 Jerry On Thu, Feb 22, 2018 at 11:55 am, Kai Nilakari wrote: I like to operate CW but hand keying is impossible due to sending errors which I get whenever I try to pound brass. |
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There may also be algorithm issues with the keyer in the stock firmware.
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Updated firmware from Jim Sheldon or Ian Lee as posted to this group could help. Or use an external electronic keyer. On Thu, Feb 22, 2018 at 12:47 pm, Nik VK4PLN wrote: Change the CW key to using D0 and D1. You will need to add header pins and modify code... |
Nick VK4PP
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