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Cw - another quirk

 

Not sure if anyone else has noticed anything similar, but here is an interesting observation.

I have a cheap mfj travel paddle I was using to test the qsk and keyer functions. I'm using an end fed half wave, fed through a 4:1 balun, about 30ft of coax? tuner in the shack. Not ideal for qrp. I noticed that often when using the keyer, the speed reduces by one step each time I hit the key, going from 20 wpm, down to one. Interestingly, if I use my good paddle, the problem does not seem to occur. I have already checked that d3 and d4 are not shorted, as this could cause the problem...but if so, it would occur all the time, with the good key as well. Anyone else see anything like this?

Also, regarding My earlier comments regarding using an audio tone to generate cw...on my rig anyway,when tuning a strong signal, you do hear a fairly noticeable tone on the wrong side of zero beat, so I guess the filter would not be good enough to avoid an upper sidebar cw signal.
 

On Sun, Oct 1, 2017 at 02:29 pm, Brent Seres wrote:
I noticed that often when using the keyer, the speed reduces by one step each time I hit the key, going from 20 wpm, down to one. Interestingly, if I use my good paddle, the problem does not seem to occur. I have already checked that d3 and d4 are not shorted, as this could cause the problem...but if so, it would occur all the time, with the good key as well. Anyone else see anything like this?
Yes I had this problem too sometimes, it was caused by RF due to poor SWR.
Make sure your SWR is OK and that everything is grounded properly.
Perhaps your cheap paddle (its cable) is not shielded or grounded properly?
If nothing helps you could try to install some decoupling caps and/or shokes.

73 Allard PE1NWL
 

Yes, I suspected that might be the case. I think I'll put bypass capacitors on both the keying lines and the function switch and spot switch. It probably doesn't help that I am using a plastic enclosure instead of metal, although the board is mounted on a metal plate. I guess I should check the grounding on everything.

Thanks for all your help
Brent
 

Don't do what I did. I thought it would be good to put a capacitor across the function? button? to keep any potential stray RF across off the line. I grabbed a .02mfd from the junk box...figured it would work. Unfortunately, I forgot that during power up, as the capacitor charges, it will hold the line low, and the Raduino reverts to default settings.

Otherwise the rig works great! Just tuning around d and testing, I've made 2 cw contacts, and also had a nice ssb qso with another ve3 station located about 150 km west of me. Reports of s6 with good audio. Not bad for a marginal antenna system!
 

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The internal pull-up on the Raduino is about 10k ohms. If you have a ~100pF to 1000pF cap, that will still shunt RF (if my “1/2Pi math is right, 160kHz for 100pF, or 16kHz for 1000pF) and will charge quick enough (6uS for 100pF, 62uS for 1000pF) to not cause problems on start up.?

On Oct 2, 2017, at 1:15 PM, Brent Seres <brentseres1@...> wrote:

Don't do what I did. I thought it would be good to put a capacitor across the function? button? to keep any potential stray RF across off the line. I grabbed a .02mfd from the junk box...figured it would work. Unfortunately, I forgot that during power up, as the capacitor charges, it will hold the line low, and the Raduino reverts to default settings.

Otherwise the rig works great! Just tuning around d and testing, I've made 2 cw contacts, and also had a nice ssb qso with another ve3 station located about 150 km west of me. Reports of s6 with good audio. Not bad for a marginal antenna system!

 

I think Raduino internal pullups are more like 37k: ? /g/BITX20/message/32999


On Sun, Oct 15, 2017 at 11:44 am, Smitty, KR6ZY wrote:
The internal pull-up on the Raduino is about 10k ohms.
 

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Could be. I remember my number being VERY rough. x3.7 on any of those numbers is unlikely to change much. Worst case not bypassing below 560kHz, or 230uS. Both of those should still be ok, though somewhat less so. So maybe a 330pF or 470pF cap would be better. :-)

-Mark

On Oct 15, 2017, at 11:47 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

I think Raduino internal pullups are more like 37k: ? /g/BITX20/message/32999

On Sun, Oct 15, 2017 at 11:44 am, Smitty, KR6ZY wrote:
The internal pull-up on the Raduino is about 10k ohms.
Jack Purdum
 

For the Arduino docs:

A pin may also be configured as an?INPUT?with?pinMode(), and subsequently made?HIGH?with?digitalWrite(). This will enable the internal 20K pullup resistors, which will?pull up?the input pin to a?HIGH?reading unless it is pulled?LOW?by external circuitry. This is how?INPUT_PULLUP?works and is described below in more detail.

Jack, W8TEE

From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: [email protected]
Sent: Sunday, October 15, 2017 2:50 PM
Subject: Re: [BITX20] Cw - another quirk

I think Raduino internal pullups are more like 37k: ? /g/BITX20/message/32999

On Sun, Oct 15, 2017 at 11:44 am, Smitty, KR6ZY wrote:
The internal pull-up on the Raduino is about 10k ohms.
 

I've got a lot more faith in the Atmel hardware doc's.
However.

Arduino is now used across a bunch of different processors, I was just looking at
the datasheet for the processor used on the Raduino.
Things like internal pullup resistors can vary considerably even for supposedly
identical parts coming off the same fab line, not something they need to control very tightly.

Could be we are all correct.



On Sun, Oct 15, 2017 at 11:56 am, Jack Purdum wrote:
For the Arduino docs:
?
 

Smitty, et al:

I wouldn't put caps on pins. What's the Nano's clock speed? MHz? therfore response time / granularity? microSeconds?
T=CR and given pullup R=37k,? ... alright you mathematicians, what value C approaches that response time?
At? MHz clock speed, even stray capactitance could be having drastic effect, hence the (documented and basic) directive: Keep leads as short as possible!?Look at Allard's functional description of operation of his Capacitive-Touch keying mod.

D'oh! :)

73 de ZL2DEX
Jack Purdum
 

the standard clock speed is 16Mhz

Jack, W8TEE












From: Dexter N Muir <dexy@...>
To: [email protected]
Sent: Sunday, October 15, 2017 3:23 PM
Subject: Re: [BITX20] Cw - another quirk

Smitty, et al:
I wouldn't put caps on pins. What's the Nano's clock speed? MHz? therfore response time / granularity? microSeconds?
T=CR and given pullup R=37k,? ... alright you mathematicians, what value C approaches that response time?
At? MHz clock speed, even stray capactitance could be having drastic effect, hence the (documented and basic) directive: Keep leads as short as possible!?Look at Allard's functional description of operation of his Capacitive-Touch keying mod.
D'oh! :)

73 de ZL2DEX
 

In another topic, someone suggested putting opto isolators on the keying and control lines, I assume mounting these right near the raduino inputs. I realize this wouldn't work for Allard's touch keying scheme, but what is the group think otherwise?

Brent
VE3CUS
 

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A cap on a GPIO pin will cause a rising/falling edge curve instead of a sharp change. It just means it’ll register the button press, or encoder wheel rotation, 2PiRC seconds later. 2Pi * 20k * 1000pF is a ~125uS delay in the register of the edge, which is only relevant to signals oscillating in the kHz range. You are unlikely to be turning the encoder wheel, or cycling buttons, that quickly, or even within a couple orders of magnitude of that rate.?

-Mark

On Oct 15, 2017, at 1:24 PM, Brent Seres <brentseres1@...> wrote:

In another topic, someone suggested putting opto isolators on the keying and control lines, I assume mounting these right near the raduino inputs. I realize this wouldn't work for Allard's touch keying scheme, but what is the group think otherwise?

Brent
VE3CUS

 

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For the BitX, if you’re just connecting a paddle, I wouldn’t bother. You’re just shorting a high impedance GPIO pin to ground, very safe to do.

If you’re connecting it to any other device with its own power supply, then you’re looking at possible ground loops. An optoisolator here would be very good.?

-Mark

On Oct 15, 2017, at 1:24 PM, Brent Seres <brentseres1@...> wrote:

In another topic, someone suggested putting opto isolators on the keying and control lines, I assume mounting these right near the raduino inputs. I realize this wouldn't work for Allard's touch keying scheme, but what is the group think otherwise?

Brent
VE3CUS

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