Dittel radio squelch

Have no idea what any of that means, but if you get in the cockpit with your smart phone on................you hear hsssssssssssssss! Turn it off and all is quiet again!
JJ

On Monday, October 3, 2016 at 3:16:06 PM UTC-7, wrote:
Have no idea what any of that means, but if you get in the cockpit with your smart phone on................you hear hsssssssssssssss! Turn it off and all is quiet again!
JJ

Nice finding, JJ.
When many of the radios in question were designed 30 to 40 years ago, there was no such thing as a cell phone.
Jim

Well, even 40 years ago the RF environment wasn't constant. Even then you could find radios with variable squelches. A toggle switch with a constant setting is a just plain dumb design.

On Tuesday, September 20, 2016 at 10:40:52 PM UTC-7, wrote:
The squelch on my Dittel FSG 50 has got to the point where it lets a lot of noise through. After a search of the Internet, I have found many allusions to the fact that this can be adjusted with one of the internal pots, but cannot find any reference of which one to actually turn. I've attached a link to a picture of the inside of my radio and I'm hoping that one of the many technical minds on r.a.s can tell me which one I should adjust.
Thanks in advance for the help.

https://drive.google.com/file/d/0B46...w?usp=drivesdk

If the problem is other electronics emitting EMI (electromagnetic interference) you can find it by successively powering down each piece of equipment; when the interference stops you have found the offending device.

EMI can be radiated thru the air or conducted thru wires (typically power leads). Ferrite beads (which are actually cylinders that the wire passes thru) are very effective at suppressing this type of interference. These are the bulky bulges you see so frequently on consumer electronic cords. They work by acting as an inductor, which is a very effective high frequency blocker. I would buy a couple of dozen of these things and put them on every power lead in your glider.

If this doesn't solve the problem then the EMI is being radiated like a radio signal. This can only be blocked by putting the offending device into a metal enclosure where every wire going into it is shielded by ferrite beads or some other filtering device. This can be a very difficult thing to do if the device has a display or control knobs that you have access to. It would probably be easier to find a comparable device that does not have this problem rather than fix it. Generally, modern electronics, especially those designed for use in an aircraft, have undergone stringent FCC EMI testing at a certified laboratory and do not have these problems. This issue shows up on cheap consumer stuff, such as those USB dc-dc converters. Equipment that has passed the required EMI testing WILL have an FCC acceptance label that identifies the manufacturer and device model. If you can't find such a label it HASN'T been certified and is probably illegal for sale in the U.S.

Tom

On Tuesday, October 4, 2016 at 1:45:50 PM UTC+13, JS wrote:
On Monday, October 3, 2016 at 3:16:06 PM UTC-7, wrote:
Have no idea what any of that means, but if you get in the cockpit with your smart phone on................you hear hsssssssssssssss! Turn it off and all is quiet again!
JJ

Nice finding, JJ.
When many of the radios in question were designed 30 to 40 years ago, there was no such thing as a cell phone.

The point of my line of questions was that there is not any one thing called a "cell phone". Mobiles phones have used more than half a dozen different modulation techniques on a number of different frequency bands over the years -- and also at very different power levels.

1st generation GSM signalling is infamous for inducing sounds into nearby audio wiring, but that's also easily fixed with a ferrite choke https://www.youtube.com/watch?v=x5ruAZ4Useg

More recent UMTS and LTE don't do that. However they could still cause interference. Aircraft band is a lot closer to mobile phone frequencies than audio is, so you can't just bung in a massive choke. However you can get specially designed "band pass filters" for any band, including aircraft band.

https://www.youtube.com/watch?v=mtW2iCwTzv8
https://www.youtube.com/watch?v=h24AP_veY6g

I'm not sure why, but all the videos a youtube search found were in Russian.. That doesn't happen to me for other search terms. Anyway, it should still make sense.

I have an idea: Turn the phone off before getting into the cockpit!

What could be simpler?

Dan

On 10/4/2016 3:06 AM, Bruce Hoult wrote:
On Tuesday, October 4, 2016 at 1:45:50 PM UTC+13, JS wrote:
On Monday, October 3, 2016 at 3:16:06 PM UTC-7, wrote:
Have no idea what any of that means, but if you get in the cockpit with your smart phone on................you hear hsssssssssssssss! Turn it off and all is quiet again!
JJ
Nice finding, JJ.
When many of the radios in question were designed 30 to 40 years ago, there was no such thing as a cell phone.
The point of my line of questions was that there is not any one thing called a "cell phone". Mobiles phones have used more than half a dozen different modulation techniques on a number of different frequency bands over the years -- and also at very different power levels.

1st generation GSM signalling is infamous for inducing sounds into nearby audio wiring, but that's also easily fixed with a ferrite choke https://www.youtube.com/watch?v=x5ruAZ4Useg

More recent UMTS and LTE don't do that. However they could still cause interference. Aircraft band is a lot closer to mobile phone frequencies than audio is, so you can't just bung in a massive choke. However you can get specially designed "band pass filters" for any band, including aircraft band.

https://www.youtube.com/watch?v=mtW2iCwTzv8
https://www.youtube.com/watch?v=h24AP_veY6g

I'm not sure why, but all the videos a youtube search found were in Russian. That doesn't happen to me for other search terms. Anyway, it should still make sense.

--
Dan, 5J

Many new smartphones are transmitting in the 850-900mhz range. (Some are
even lower in 450,older ones are 2100, 1900, 1700...)

If you look in the spectrum allocation - depending on where you are - it
may be close enough for cross talk I expect on an older receiver.

On 2016-10-04 02:45, JS wrote:
On Monday, October 3, 2016 at 3:16:06 PM UTC-7, wrote:
Have no idea what any of that means, but if you get in the cockpit with your smart phone on................you hear hsssssssssssssss! Turn it off and all is quiet again!
JJ

Nice finding, JJ.
When many of the radios in question were designed 30 to 40 years ago, there was no such thing as a cell phone.
Jim


--
Bruce Greeff
T59D #1771

On 10/5/2016 7:16 AM, BruceGreeff wrote:
Many new smartphones are transmitting in the 850-900mhz range. (Some are
even lower in 450,older ones are 2100, 1900, 1700...)

If you look in the spectrum allocation - depending on where you are - it
may be close enough for cross talk I expect on an older receiver.

The cause of the noise is unlikely to be the phone's transmitter. It is
more likely the wide-spectrum noise generated by the phone's digital
innards.

Except for the moribund old AM broadcast band, the only common use of AM
(amplitude modulation, AKA "ancient modulation") radio that I can think
of is aviation radios. The main reason that AM has been so unpopular
for the last half-century or so is because it is very difficult to build
an AM receiver that is immune to static and noise.

On Wed, 05 Oct 2016 08:48:44 -0400, Vaughn Simon wrote:

On 10/5/2016 7:16 AM, BruceGreeff wrote:
Many new smartphones are transmitting in the 850-900mhz range. (Some
are even lower in 450,older ones are 2100, 1900, 1700...)

If you look in the spectrum allocation - depending on where you are -
it may be close enough for cross talk I expect on an older receiver.

The cause of the noise is unlikely to be the phone's transmitter. It is
more likely the wide-spectrum noise generated by the phone's digital
innards.

Except for the moribund old AM broadcast band, the only common use of AM
(amplitude modulation, AKA "ancient modulation") radio that I can think
of is aviation radios. The main reason that AM has been so unpopular
for the last half-century or so is because it is very difficult to build
an AM receiver that is immune to static and noise.

Short wave AM broadcasting, is still there, since its in the band that's
strongly reflected by the ionosphere, so has beyond the horizon range
Many government stations still use AM these band, e.g. Voice of America.

The Marine VHF band (156-162.025 MHz) used for much the same purposes as
the Air Band, i.e. ship to shore, ship to ship, port operations...

I suspect these are likely to remain AM for a very long time since they
can work well on much narrower channels than FM and are certainly
unlikely to get more band allocation in the forseeable futu just look
at the way that mobile phones snarf up any frequencies they can get.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Ah... The old days of driving across the southern US and listing to WLS
890 AM Rock N' Roll out of Chicago. This only worked at night, of course...

Memories,
Dan



On 10/5/2016 8:20 AM, Martin Gregorie wrote:
On Wed, 05 Oct 2016 08:48:44 -0400, Vaughn Simon wrote:

On 10/5/2016 7:16 AM, BruceGreeff wrote:
Many new smartphones are transmitting in the 850-900mhz range. (Some
are even lower in 450,older ones are 2100, 1900, 1700...)

If you look in the spectrum allocation - depending on where you are -
it may be close enough for cross talk I expect on an older receiver.
The cause of the noise is unlikely to be the phone's transmitter. It is
more likely the wide-spectrum noise generated by the phone's digital
innards.

Except for the moribund old AM broadcast band, the only common use of AM
(amplitude modulation, AKA "ancient modulation") radio that I can think
of is aviation radios. The main reason that AM has been so unpopular
for the last half-century or so is because it is very difficult to build
an AM receiver that is immune to static and noise.
Short wave AM broadcasting, is still there, since its in the band that's
strongly reflected by the ionosphere, so has beyond the horizon range
Many government stations still use AM these band, e.g. Voice of America.

The Marine VHF band (156-162.025 MHz) used for much the same purposes as
the Air Band, i.e. ship to shore, ship to ship, port operations...

I suspect these are likely to remain AM for a very long time since they
can work well on much narrower channels than FM and are certainly
unlikely to get more band allocation in the forseeable futu just look
at the way that mobile phones snarf up any frequencies they can get.



--
Dan, 5J