Dittel radio squelch

[[email protected]]

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/0B46vXkrD2H1DT0REVmx3aUtPSWc/view?usp=drivesdk

[[email protected]]

There is a good chance you don't have a problem with squelch at all, but you do have a problem with interference from all the other electrical devices in your panel. Your radio is doing exactly what it is designed to do.........present a weak signal for you to hear! If you turn down the internal squelch, you will also be denying any and all weak signals that everybody else is hearing. What other instruments do you have in your panel and how close are they to your radio? Try turning off the other instruments,one at a time to see if your radio stops breaking squelch.
JJ

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

Sounds reasonable, I guess the next questions are...
-any new devices added?
-any wiring recently moved?
-any devices moved?

I would start with the new stuff, work backward from there.

[Craig Funston]

On Wednesday, September 21, 2016 at 7:46:27 AM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote:
> Sounds reasonable, I guess the next questions are...
> -any new devices added?
> -any wiring recently moved?
> -any devices moved?
>
> I would start with the new stuff, work backward from there.

I ran into problems with an inexpensive DC/DC converter (12v to 5v for USB). Lots of the electronics we use generate noise. The cheap converter broke squelch so badly the radio wasn't usable. Solved the issue by getting a different converter unit.

Good luck,
7Q

[SoaringXCellence]

I also was getting a lot of breaking of the squelch with a cheap 12V USB converter. I later used a Dell adapter like the one that came with the Dell Streak and it was very RF quiet.

MB

[Sig_ZA]

Since I installed my Flarm Red Box I also get a lot of interference. I adjusted the squelch pot a bit. You should be able to Google a manual. I tried various ferrite chockes, but they didn't help.

[Martin Gregorie[_5_]]

On Wed, 21 Sep 2016 23:51:07 -0700, Sig_ZA wrote:

> Since I installed my Flarm Red Box I also get a lot of interference. I
> adjusted the squelch pot a bit. You should be able to Google a manual. I
> tried various ferrite chockes, but they didn't help.

I've used a very cheap 12v->5v converter (a fleaBay plastic cigar lighter
5v source) to power a variety of PDAs without upsetting either an ATR 500
or my current Dittel KRT2 radio.

However, I did remove the switch-mode electronics from the plastic shell
and installed it in a small metal box with ferrites on all the leads to
and from it. These small switch-mode voltage converters do tend to
generate RF hash, so need to be installed in metal or metallised plastic
enclosures. Besides, doing this and using good connectors is much more
reliable than using a Maplins/Radio Shack (RIP) cigar lighter socket and
either holding the converter in with wing tape or simply hoping it won't
leap out some day.


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

[andrew mcquigg]

On Wednesday, September 21, 2016 at 1:40:52 AM UTC-4, 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/0B46vXkrD2H1DT0REVmx3aUtPSWc/view?usp=drivesdk

[andrew mcquigg]

On Wednesday, September 21, 2016 at 1:40:52 AM UTC-4, 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/0B46vXkrD2H1DT0REVmx3aUtPSWc/view?usp=drivesdk

[andrew mcquigg]

On Wednesday, September 21, 2016 at 1:40:52 AM UTC-4, 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/0B46vXkrD2H1DT0REVmx3aUtPSWc/view?usp=drivesdk

I have had this problem and there is a pot that will adjust the squelch
issue that you are having.Your picture covers up this pot by those yellow
straps.I believe I can find a diagram that Karl sent to me years ago.If so
I will notify you.

[ZP]

I'm having the same problem with mine without any converters in the circuit and am interested in trying the squelch adjustment. Thanks for the help.

[[email protected]]

I have found the Cambridge GPS is always the first suspect, with the SN-10 close behind + cheap voltage converters, but almost everything will add some noise. Try turning on your radio with no squelch applied, then listen as the other electrical devices are turned on. The hiss will slowly build until it becomes a roar. Turning down the internal squelch is placing a band-aid over the problem. Did you hear the guys 60 miles away, climbing under Cu's?.......... I did!
:>) JJ

[Karl Striedieck[_2_]]

There is a pot that adjusts the squelch. I have it marked on my FSG-50. If you are interested contact me karls at uplink.net

KS

[Karl Striedieck[_2_]]

With the bottom pan off (4 screws) and looking down at the bottom innerds with the front toward you the pot to adjust is 3 and 3/4 inches back from the front face of the radio. It is on the extreme right, has red sealing paint on it and is just in front of a big rectangular something that is labeled "A3411P" on my radio.

Email me if you want a pic karls at uplink dot net.

KS

[Karl Striedieck[_2_]]

PS Turn counterclockwise for more squelch (less noise).

KS

[Sig_ZA]

On Monday, 26 September 2016 17:45:30 UTC+2, Karl Striedieck wrote:
> PS Turn counterclockwise for more squelch (less noise).
>
> KS

What I did was to drill a small hole in the cover, above the squelch pot. That way when making small adjustments. The cover need not be removed.

[[email protected]]

Just found yet another electronic device that will break squelch on your radio..............your smart phone!
The buyer of my D-2, sat down to see how he fit. The radio broke squelch..........when he turned off his smart phone, the radio went silent again.
JJ

[Bruce Hoult]

On Tuesday, October 4, 2016 at 8:03:36 AM UTC+13, wrote:
> Just found yet another electronic device that will break squelch on your radio..............your smart phone!
> The buyer of my D-2, sat down to see how he fit. The radio broke squelch..........when he turned off his smart phone, the radio went silent again.
> JJ

What kind of cell coverage did you have there at the time?

[[email protected]]

3 bars most of the time.

[Bruce Hoult]

On Tuesday, October 4, 2016 at 9:38:27 AM UTC+13, wrote:
> 3 bars most of the time.

Yes, but GSM, 3G, LTE?

[[email protected]]

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

[JS]

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

[ZP]

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.

[2G]

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/0B46vXkrD2H1DT0REVmx3aUtPSWc/view?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

[Bruce Hoult]

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 Marotta]

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

[BruceGreeff]

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

[Vaughn Simon[_2_]]

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.

[Martin Gregorie[_5_]]

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 future: just look
at the way that mobile phones snarf up any frequencies they can get.


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

[Dan Marotta]

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 future: just look
> at the way that mobile phones snarf up any frequencies they can get.
>
>

--
Dan, 5J

[Vaughn Simon[_2_]]

On 10/5/2016 10:20 AM, Martin Gregorie wrote:

> 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.

True enough.
>
> 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 future: just look
> at the way that mobile phones snarf up any frequencies they can get.
>
>
Actually, the Marine VHF channels use FM. Also, FM can be very narrow
band these days.

Vaughn

[Martin Gregorie[_5_]]

On Wed, 05 Oct 2016 17:01:46 -0400, Vaughn Simon wrote:

> Actually, the Marine VHF channels use FM. Also, FM can be very narrow
> band these days.
>
IIRC they were AM back in the mid 60s (I remember setting up a boat's
transceiver back then, based on a ZC1. This was a NZ Army radio of WW2
vintage and certainly AM modulation - it was commonly used as a base
station for units using the US Army's WS48 backpack sets (battery driven
AM).

When did the Marine band switch to FM and why?


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

[Vaughn Simon[_2_]]

On 10/5/2016 6:26 PM, Martin Gregorie wrote:
> IIRC they were AM back in the mid 60s

Yes, but they weren't VHF then. They were in the 2 megacycle band and
required huge antennas for best range. Straight out of high school, my
first full-time job was working on those monsters.

[2G]

On Wednesday, October 5, 2016 at 6:05:22 PM UTC-7, Vaughn Simon wrote:
> On 10/5/2016 6:26 PM, Martin Gregorie wrote:
> > IIRC they were AM back in the mid 60s
>
> Yes, but they weren't VHF then. They were in the 2 megacycle band and
> required huge antennas for best range. Straight out of high school, my
> first full-time job was working on those monsters.

All of this discussion of interference by out-of-band transmitters is way off topic; our aircraft radios have very good tunable bandpass RF filters that only pass thru the very specific VHF band we are listening to and reject all other bands. Otherwise we would be hearing transmissions from all sorts of transmitters, including other aircraft radios transmitting on an adjacent frequency. The place where the interference can pass thru into the receiver are not the antenna leads: it is the power leads where the RF filtering is less robust.

Tom

[Bruce Hoult]

On Thursday, October 6, 2016 at 3:38:05 PM UTC+13, 2G wrote:
> On Wednesday, October 5, 2016 at 6:05:22 PM UTC-7, Vaughn Simon wrote:
> > On 10/5/2016 6:26 PM, Martin Gregorie wrote:
> > > IIRC they were AM back in the mid 60s
> >
> > Yes, but they weren't VHF then. They were in the 2 megacycle band and
> > required huge antennas for best range. Straight out of high school, my
> > first full-time job was working on those monsters.
>
> All of this discussion of interference by out-of-band transmitters is way off topic; our aircraft radios have very good tunable bandpass RF filters that only pass thru the very specific VHF band we are listening to and reject all other bands. Otherwise we would be hearing transmissions from all sorts of transmitters, including other aircraft radios transmitting on an adjacent frequency. The place where the interference can pass thru into the receiver are not the antenna leads: it is the power leads where the RF filtering is less robust.

You can put as aggressive a choke as you want on the power leads :-)

[Dan Marotta]

Megacycles - what a blast from the past! It was '68 or '69 and I was a
ground radio repair tech in the USAF when they switched from cycles to
Hertz. How traumatic...

On 10/5/2016 7:05 PM, Vaughn Simon wrote:
> On 10/5/2016 6:26 PM, Martin Gregorie wrote:
>> IIRC they were AM back in the mid 60s
>
> Yes, but they weren't VHF then. They were in the 2 megacycle band and
> required huge antennas for best range. Straight out of high school,
> my first full-time job was working on those monsters.

--
Dan, 5J

[Dan Marotta]

Noise is, by nature, made up of a wide range of frequencies, some of
which are amplitude modulated and at the same frequency as the radio is
tuned to (think lightening buzz in your AM radio). All of the filters
in the world will not keep them out of your speaker. They must be
attacked at the source, i.e., that cheap DC to DC converter (like I just
removed from my glider).

My perfectly working Becker radio started breaking squelch on all
frequencies immediately after installing the converter and went back to
its well-behaved self after removing power from the converter.

If you have not installed something new, or moved some wires, or changed
anything electronic in your glider, try turning your mobile phone off.
Besides, you'll enjoy the isolation that comes with it.

Good flying!

Dan

On 10/6/2016 3:45 AM, Bruce Hoult wrote:
> On Thursday, October 6, 2016 at 3:38:05 PM UTC+13, 2G wrote:
>> On Wednesday, October 5, 2016 at 6:05:22 PM UTC-7, Vaughn Simon wrote:
>>> On 10/5/2016 6:26 PM, Martin Gregorie wrote:
>>>> IIRC they were AM back in the mid 60s
>>> Yes, but they weren't VHF then. They were in the 2 megacycle band and
>>> required huge antennas for best range. Straight out of high school, my
>>> first full-time job was working on those monsters.
>> All of this discussion of interference by out-of-band transmitters is way off topic; our aircraft radios have very good tunable bandpass RF filters that only pass thru the very specific VHF band we are listening to and reject all other bands. Otherwise we would be hearing transmissions from all sorts of transmitters, including other aircraft radios transmitting on an adjacent frequency. The place where the interference can pass thru into the receiver are not the antenna leads: it is the power leads where the RF filtering is less robust.
> You can put as aggressive a choke as you want on the power leads :-)

--
Dan, 5J

[Bruce Hoult]

On Friday, October 7, 2016 at 3:27:45 AM UTC+13, Dan Marotta wrote:
> Noise is, by nature, made up of a wide range of frequencies, some of
> which are amplitude modulated and at the same frequency as the radio is
> tuned to (think lightening buzz in your AM radio). All of the filters
> in the world will not keep them out of your speaker. They must be
> attacked at the source, i.e., that cheap DC to DC converter (like I just
> removed from my glider).
>
> My perfectly working Becker radio started breaking squelch on all
> frequencies immediately after installing the converter and went back to
> its well-behaved self after removing power from the converter.
>
> If you have not installed something new, or moved some wires, or changed
> anything electronic in your glider, try turning your mobile phone off.
> Besides, you'll enjoy the isolation that comes with it.
>
> Good flying!
>
> Dan
>
> On 10/6/2016 3:45 AM, Bruce Hoult wrote:
> > On Thursday, October 6, 2016 at 3:38:05 PM UTC+13, 2G wrote:
> >> On Wednesday, October 5, 2016 at 6:05:22 PM UTC-7, Vaughn Simon wrote:
> >>> On 10/5/2016 6:26 PM, Martin Gregorie wrote:
> >>>> IIRC they were AM back in the mid 60s
> >>> Yes, but they weren't VHF then. They were in the 2 megacycle band and
> >>> required huge antennas for best range. Straight out of high school, my
> >>> first full-time job was working on those monsters.
> >> All of this discussion of interference by out-of-band transmitters is way off topic; our aircraft radios have very good tunable bandpass RF filters that only pass thru the very specific VHF band we are listening to and reject all other bands. Otherwise we would be hearing transmissions from all sorts of transmitters, including other aircraft radios transmitting on an adjacent frequency. The place where the interference can pass thru into the receiver are not the antenna leads: it is the power leads where the RF filtering is less robust.
> > You can put as aggressive a choke as you want on the power leads :-)

Sure, a nasty chopper DC converter isn't going to do your RF environment a lot of good.

That's a totally different thing from a mobile phone operating on a post-GSM standard.

[[email protected]]

I've had a similar problem from time to time with my FSG-50, every now and then a burst of noise. Eventually I realized it was only happening in the circuit for runway 25 at my home base, at about 2/3 of the way on the downwind leg. It hasn't happened this year so all I can thin of is that there may have been some equipment at the storage and construction yard beneath the downwind that was putting out electromagnetic interference. This happened with the original avionic setup (Peschges VP-4E Nav), when I added a Colibri logger and with my current setup (LX8080 Simple, V5 vario, Powerflarm Core and FLarmview 57) so the rest of the equipment doesn't seem to be a factor.

The radio is pretty sensitive - I've been at 2,000ft. ASL (1,900ft. AGL) on a mountain ridge in Hope and have been able to hear transmissions from people in the circuit at Delta Airpark (both airports are assigned the same frequency) 70Km away!

I tried JJ's progressive start up of the avionics with the radio squelch turned off and was pleasantly surprised to find that the noise didn't increase noticeably as I turned on the other units.

[Martin Gregorie[_5_]]

On Thu, 06 Oct 2016 08:14:34 -0600, Dan Marotta wrote:

> Megacycles - what a blast from the past! It was '68 or '69 and I was a
> ground radio repair tech in the USAF when they switched from cycles to
> Hertz. How traumatic...
>
> On 10/5/2016 7:05 PM, Vaughn Simon wrote:
>> On 10/5/2016 6:26 PM, Martin Gregorie wrote:
>>> IIRC they were AM back in the mid 60s
>>
>> Yes, but they weren't VHF then. They were in the 2 megacycle band and
>> required huge antennas for best range. Straight out of high school, my
>> first full-time job was working on those monsters.

It was a hugely wide-ranging renaming blitz, as it replaced many of the
old descriptive unit names by the name of a relevant, famous and deceased
scientist, e.g. the MKS unit of work, formerly the watt.second
(electrical) or newton.metre (mechanical) became the Joule and the unit
of frequency (the cycle per second became the Hertz.

I suppose it rationalised things by naming virtually *all* units of
measurement apart from distance, mass and time after people, but against
that it meant that it was now necessary to remember the dimensions of a
unit, i.e. that a Joule is a watt.second and that watts are amps times
volts in order to make calculations involving power, time and energy.


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

[Bruce Hoult]

On Thursday, October 6, 2016 at 8:41:04 PM UTC+3, wrote:
> I've had a similar problem from time to time with my FSG-50, every now and then a burst of noise. Eventually I realized it was only happening in the circuit for runway 25 at my home base, at about 2/3 of the way on the downwind leg. It hasn't happened this year so all I can thin of is that there may have been some equipment at the storage and construction yard beneath the downwind that was putting out electromagnetic interference.

Sometime in 1990 or 1991 I noticed that when I was speaking on the phone in my new flat in Newlands, Wellington there would sometimes be a "bzzzt" audible every four or five seconds. It seemed to happen more on rainy days.

One day I was gazing out the window while on the phone (the clouds can't have been all that low, or the rain heavy) This is something like the view. I was in the brick house on the left.

https://goo.gl/maps/r5WKiyG2RRA2

I noticed the bzzzt was happening in synchronization with the rotation of the big FO primary radar on Hawkins Hill 13.6 km away!

[Dan Marotta]

It would be interesting to look at the emissions of your phone with a
spectrum analyzer. We're not talking just the telephone signal here,
there are so many other electronic gizmos inside that little box that
could be putting out spurious radiation.

On 10/6/2016 9:21 AM, Bruce Hoult wrote:
> On Friday, October 7, 2016 at 3:27:45 AM UTC+13, Dan Marotta wrote:
>> Noise is, by nature, made up of a wide range of frequencies, some of
>> which are amplitude modulated and at the same frequency as the radio is
>> tuned to (think lightening buzz in your AM radio). All of the filters
>> in the world will not keep them out of your speaker. They must be
>> attacked at the source, i.e., that cheap DC to DC converter (like I just
>> removed from my glider).
>>
>> My perfectly working Becker radio started breaking squelch on all
>> frequencies immediately after installing the converter and went back to
>> its well-behaved self after removing power from the converter.
>>
>> If you have not installed something new, or moved some wires, or changed
>> anything electronic in your glider, try turning your mobile phone off.
>> Besides, you'll enjoy the isolation that comes with it.
>>
>> Good flying!
>>
>> Dan
>>
>> On 10/6/2016 3:45 AM, Bruce Hoult wrote:
>>> On Thursday, October 6, 2016 at 3:38:05 PM UTC+13, 2G wrote:
>>>> On Wednesday, October 5, 2016 at 6:05:22 PM UTC-7, Vaughn Simon wrote:
>>>>> On 10/5/2016 6:26 PM, Martin Gregorie wrote:
>>>>>> IIRC they were AM back in the mid 60s
>>>>> Yes, but they weren't VHF then. They were in the 2 megacycle band and
>>>>> required huge antennas for best range. Straight out of high school, my
>>>>> first full-time job was working on those monsters.
>>>> All of this discussion of interference by out-of-band transmitters is way off topic; our aircraft radios have very good tunable bandpass RF filters that only pass thru the very specific VHF band we are listening to and reject all other bands. Otherwise we would be hearing transmissions from all sorts of transmitters, including other aircraft radios transmitting on an adjacent frequency. The place where the interference can pass thru into the receiver are not the antenna leads: it is the power leads where the RF filtering is less robust.
>>> You can put as aggressive a choke as you want on the power leads :-)
> Sure, a nasty chopper DC converter isn't going to do your RF environment a lot of good.
>
> That's a totally different thing from a mobile phone operating on a post-GSM standard.

--
Dan, 5J

[Bruce Hoult]

On Saturday, October 8, 2016 at 3:46:07 AM UTC+13, Dan Marotta wrote:
> It would be interesting to look at the emissions of your phone with a
> spectrum analyzer. We're not talking just the telephone signal here,
> there are so many other electronic gizmos inside that little box that
> could be putting out spurious radiation.

I have one :-)

http://rf-explorer.com

With the 240-960 MHz and 15-2700 MHz modules.

I've found it very useful for everything from verifying transmit power on glider radios, to checking for unused WIFI channels, to ...