Glider Electronics Experiment #1 - electrical crosstalk demonstrated

[Richard Lancaster[_2_]]

Hi all,

I got a bit bored and started filming some glider electronics experiments. I am attempting to pitch them to be interesting and understandable even if you don't know much about electronics.

First up:
Glider Electronics Experiment #1 - electrical crosstalk demonstrated

Available here:
https://RJPLancaster.net/

Best regards,

Richard

[[email protected]]

Very nice and well presented topic. Thanks.

On Friday, May 1, 2020 at 12:17:03 PM UTC-5, Richard Lancaster wrote:
> Hi all,
>
> I got a bit bored and started filming some glider electronics experiments. I am attempting to pitch them to be interesting and understandable even if you don't know much about electronics.
>
> First up:
> Glider Electronics Experiment #1 - electrical crosstalk demonstrated
>
> Available here:
> https://RJPLancaster.net/
>
> Best regards,
>
> Richard

[Nick Kennedy[_3_]]

Dang!
Learned something there, let me tell you.
I'm going to check my wiring after that demo.
I keep picking up Linda Rohnstat on my radio, is this why?
Nick
T

[2G]

On Friday, May 1, 2020 at 10:17:03 AM UTC-7, Richard Lancaster wrote:
> Hi all,
>
> I got a bit bored and started filming some glider electronics experiments. I am attempting to pitch them to be interesting and understandable even if you don't know much about electronics.
>
> First up:
> Glider Electronics Experiment #1 - electrical crosstalk demonstrated
>
> Available here:
> https://RJPLancaster.net/
>
> Best regards,
>
> Richard

Well done, Richard. Electrical interference is a tough subject even for electrical engineers, such as myself. You presentation is an intuitive approach, which is much more understandable than, say, equivalent circuits. Keep it up.

Tom

[Richard Lancaster[_2_]]

Thanks all for the positive comments.

Got asked on the UK glider forum for a description of what the video was about. So in case anyone is debating whether to sink their time into it, here's a quick abstract:

"Electrical crosstalk is a type of interference where the signals carried in
one set of wires "talk across" into another set of wires. This video sets
up a simple glider electrical harness, talks about how crosstalk might
occur in it, demonstrates it occurring and illustrates the magnitude of the
consequences to the pilot."

Best regards,

Richard

[Richard Livingston]

Nice demo of cross talk. Last year I fixed a problem in our glider where the microphone wires were not completely shielded, as in your demo, and were picking up signal from the radio speaker wires, also not completely shielded. The result was intermittently the radio would squeal during transmit due to feedback from the speaker back into the microphone. It was intermittent due to the wires shifting slightly every time the canopy opened/closed. Shielding both the speaker and microphone wires fixed the problem.

Rich L.

[Craig Reinholt]

On Friday, May 1, 2020 at 10:17:03 AM UTC-7, Richard Lancaster wrote:
> Hi all,
>
> I got a bit bored and started filming some glider electronics experiments. I am attempting to pitch them to be interesting and understandable even if you don't know much about electronics.
>
> First up:
> Glider Electronics Experiment #1 - electrical crosstalk demonstrated
>
> Available here:
> https://RJPLancaster.net/
>
> Best regards,
>
> Richard

Well done. I'm looking forward for your next installment. Thank you!
Craig

[Richard Pfiffner[_2_]]

On Saturday, May 2, 2020 at 2:22:55 AM UTC-7, Richard Lancaster wrote:
> Thanks all for the positive comments.
>
> Got asked on the UK glider forum for a description of what the video was about. So in case anyone is debating whether to sink their time into it, here's a quick abstract:
>
> "Electrical crosstalk is a type of interference where the signals carried in
> one set of wires "talk across" into another set of wires. This video sets
> up a simple glider electrical harness, talks about how crosstalk might
> occur in it, demonstrates it occurring and illustrates the magnitude of the
> consequences to the pilot."
>
> Best regards,
>
> Richard

Great YouTube when is the next one on shielding.

Richard
www.craggyaero.com

[Richard Lancaster[_2_]]

On Saturday, 2 May 2020 16:20:40 UTC+1, Richard Pfiffner wrote:
> Great YouTube when is the next one on shielding.

Am attempting to film the next one tomorrow (Sunday), then hopefully edited by the end of the week.

Richard

[Richard Lancaster[_2_]]

On Saturday, 2 May 2020 14:41:54 UTC+1, Richard Livingston wrote:
> It was intermittent due to the wires shifting slightly
> every time the canopy opened/closed. Shielding both the
> speaker and microphone wires fixed the problem.

Setting up these experiments I was intriged by how much small relative movements in the cables when they are bundled together, even at a single point in the cable run, can change the crosstalk. Will try to show that and the effect of distance in the next video if I can pull off a clean demo.

Richard

[[email protected]]

On Saturday, May 2, 2020 at 9:41:54 AM UTC-4, Richard Livingston wrote:
> Nice demo of cross talk. Last year I fixed a problem in our glider where the microphone wires were not completely shielded, as in your demo, and were picking up signal from the radio speaker wires, also not completely shielded. The result was intermittently the radio would squeal during transmit due to feedback from the speaker back into the microphone. It was intermittent due to the wires shifting slightly every time the canopy opened/closed. Shielding both the speaker and microphone wires fixed the problem.
>
> Rich L.

Such feedback could only occur if the radio had the (mis)feature of echoing the signal from the mic to the speaker. Kind of lets you know you've got the PTT pressed and it's all working, but not really necessary. With that happening, you may also get acoustic feedback, from the speaker back into the mic, even without crosstalk in the wiring. Maybe that feature can be turned off somewhere in the radio's settings?

[Tim Newport-Peace[_6_]]

At 21:32 02 May 2020, wrote:
>On Saturday, May 2, 2020 at 9:41:54 AM UTC-4, Richard Livingston wrote:
>> Nice demo of cross talk. Last year I fixed a problem in our glider
>where=
> the microphone wires were not completely shielded, as in your demo, and
>we=
>re picking up signal from the radio speaker wires, also not completely
>shie=
>lded. The result was intermittently the radio would squeal during
>transmit=
> due to feedback from the speaker back into the microphone. It was
>intermi=
>ttent due to the wires shifting slightly every time the canopy
>opened/close=
>d. Shielding both the speaker and microphone wires fixed the problem.
>>=20
>> Rich L.
>
>Such feedback could only occur if the radio had the (mis)feature of
>echoing=
> the signal from the mic to the speaker. Kind of lets you know you've
got
>=
>the PTT pressed and it's all working, but not really necessary. With
that
>=
>happening, you may also get acoustic feedback, from the speaker back into
>t=
>he mic, even without crosstalk in the wiring. Maybe that feature can be
>tu=
>rned off somewhere in the radio's settings?
>
Many radios have this foldback feature for use with headsets and intercoms.
But yes, it could cause acoustic feedback. But this does not satisfactorily
account for the above fix.

What would seem more likely is that the poor sheilding has allowed
cross-talk from the antenna cable to the speaker cables which has allowed
the RF to feed back into the radio box where it caused meyhem. The speaker
does not need to be active for this to happen.

The section on supressing cross-talk is going to be interesting because
there are so many possible causes.

Tim.

[Richard Lancaster[_2_]]

On Sunday, 3 May 2020 11:30:04 UTC+1, Tim Newport-Peace wrote:
> The section on supressing cross-talk is going to be interesting because
> there are so many possible causes.

Experiment #2 is just going to look at the effect of cable type on the type of noise seen in experiment #1.

Experiment #3 on-wards, if I manage to keep making them, will look at other types of noise.

Best regards,

Richard

[Charlie M. (UH & 002 owner/pilot)]

Nicely done.

[Richard Livingston]

On Saturday, May 2, 2020 at 4:32:04 PM UTC-5, wrote:
> On Saturday, May 2, 2020 at 9:41:54 AM UTC-4, Richard Livingston wrote:
> > Nice demo of cross talk. Last year I fixed a problem in our glider where the microphone wires were not completely shielded, as in your demo, and were picking up signal from the radio speaker wires, also not completely shielded. The result was intermittently the radio would squeal during transmit due to feedback from the speaker back into the microphone. It was intermittent due to the wires shifting slightly every time the canopy opened/closed. Shielding both the speaker and microphone wires fixed the problem.
> >
> > Rich L.
>
> Such feedback could only occur if the radio had the (mis)feature of echoing the signal from the mic to the speaker. Kind of lets you know you've got the PTT pressed and it's all working, but not really necessary. With that happening, you may also get acoustic feedback, from the speaker back into the mic, even without crosstalk in the wiring. Maybe that feature can be turned off somewhere in the radio's settings?

That's called the "sidetone", and many radios have an adjustment for that. It is also possible (likely even) that the feedback was from the RF back into the microphone wires. Connectors are notoriously leaky, and even coax can leak a little bit. If that RF signal gets into the microphone input it can be rectified by the transistors in the amplifier and produce feedback that will cause a squeal.

Rich L.

[2G]

On Sunday, May 3, 2020 at 5:13:09 AM UTC-7, Richard Lancaster wrote:
> On Sunday, 3 May 2020 11:30:04 UTC+1, Tim Newport-Peace wrote:
> > The section on supressing cross-talk is going to be interesting because
> > there are so many possible causes.
>
> Experiment #2 is just going to look at the effect of cable type on the type of noise seen in experiment #1.
>
> Experiment #3 on-wards, if I manage to keep making them, will look at other types of noise.
>
> Best regards,
>
> Richard

I would suggest one more: the effect of ground distribution, especially single-point commons, on noise.

Tom

[Stephen Szikora]

I blame the noise in my cockpit on my choice of lunch.