Crazy Radio Issue, Help Needed.
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There are some reports of GPS receivers causing interference with radios, it is all to do with harmonics of the GPS IF getting into VHF radio receivers. This could be either in-band or if strong enough an image frequency. Is there a GPS on this airplane?
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I`m betting on the two COMM boxes.
Like - put COMM 1 and 2 both on the same Freq. Do you still have the same prob?
Or, Is your COMM one and 2 on the same . . . . box, can you seperate them, what I mean is: is there just one switch for the system - why am I asking. . . ? I am trying to seperate COMM 1 from COMM 2.
So if you can ride with one COMM "OFF" then fine, if not then just put both on the same freq. What am I getting at? I am thinking COMM 1 is interfering with COMM 2 and/or vice versa. Why? Because it happens on other aircraft.
Good Luck.
(By the way: We used to get the rythum of the beacon, come through the headsets - it was quite soothing actually)
The have not wired something to the VOR huh. . ?
Bonding. . . ?
vertical / horizontal field . . .of the antenna(e) ? i.e., sticking up vertical out of the ground must be received by equally vertical aeriel on a/c - same for horizontal - but you know that right. . .?
hard iron / soft iron. . . .?
. . .its a right booger this one innit. . .
A wire, missing from the aft of the aircraft to the . . . . roof/top of the aeroplane. . .strung outside the aircraft like a washing line. . . ?
Quadrantal Error keeps looming up in my memory. . . but that refers to NDB reception on Medium Wave. . . .the signal hitting the aircraft at the port quarter was vectored (from) the 6 o`clock position (the tail) giving the impression that the NDB (on Medium Wave) was behind the aircraft - quadrantal error. Could the opposite be true. . ?
HT lead burnt and . . . HT lead . . . signal to power. . . .Has anything with a charge through it like a lead or a cable crossed or passed over or near a lead or box or entity which contains a signal . . . (a stupid and obvious question. . . but with inherent potential). . . potential. . .
windscreen heating element. . .*air con* . .
. . .if you have an NDB on the a/c have they wired something to the NDB?
that`ll be fifty cents, please.
Also the above is FREE so if you don`t like it - then bin it . . .
(may contain nuts)
(do not try this at home)
(always make sure a parent is with you)
(the management accepts no responsibility)
(I know nothing)
(YOU asked!!)
(Mind that Prop!!!)
(Mind that Prop!!!!)
(don`t sue - am poor)
Like - put COMM 1 and 2 both on the same Freq. Do you still have the same prob?
Or, Is your COMM one and 2 on the same . . . . box, can you seperate them, what I mean is: is there just one switch for the system - why am I asking. . . ? I am trying to seperate COMM 1 from COMM 2.
So if you can ride with one COMM "OFF" then fine, if not then just put both on the same freq. What am I getting at? I am thinking COMM 1 is interfering with COMM 2 and/or vice versa. Why? Because it happens on other aircraft.
Good Luck.
(By the way: We used to get the rythum of the beacon, come through the headsets - it was quite soothing actually)
The have not wired something to the VOR huh. . ?
Bonding. . . ?
vertical / horizontal field . . .of the antenna(e) ? i.e., sticking up vertical out of the ground must be received by equally vertical aeriel on a/c - same for horizontal - but you know that right. . .?
hard iron / soft iron. . . .?
. . .its a right booger this one innit. . .
A wire, missing from the aft of the aircraft to the . . . . roof/top of the aeroplane. . .strung outside the aircraft like a washing line. . . ?
Quadrantal Error keeps looming up in my memory. . . but that refers to NDB reception on Medium Wave. . . .the signal hitting the aircraft at the port quarter was vectored (from) the 6 o`clock position (the tail) giving the impression that the NDB (on Medium Wave) was behind the aircraft - quadrantal error. Could the opposite be true. . ?
HT lead burnt and . . . HT lead . . . signal to power. . . .Has anything with a charge through it like a lead or a cable crossed or passed over or near a lead or box or entity which contains a signal . . . (a stupid and obvious question. . . but with inherent potential). . . potential. . .
windscreen heating element. . .*air con* . .
. . .if you have an NDB on the a/c have they wired something to the NDB?
that`ll be fifty cents, please.
Also the above is FREE so if you don`t like it - then bin it . . .
(may contain nuts)
(do not try this at home)
(always make sure a parent is with you)
(the management accepts no responsibility)
(I know nothing)
(YOU asked!!)
(Mind that Prop!!!)
(Mind that Prop!!!!)
(don`t sue - am poor)
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The noise is an efficient "jammer", and there is one common thing about RF jammers, they work best when placed between the receiver antenna and the direction of interest. Hangflyer has clearly demonstrated that the "blocking" is ahead, i.e. forward of the antenna, which leads me to suspect that the "spark" transmitter is somewhere on the engine block.
1: Relative "badness" of interference is the same at 200 meters (hangflywer stated direct line of sight to base station antennna) or at a significant distance, 20km would result in 40db Rx level difference.
Hard to see how a fixed level source would always have same impact.
2: Interference present -only- when tuned to an active transmitter.
3: The extreme dirictional sensitivity, even assuming bad shadowing the RX level would only change 6Db or so as the aircraft turned.
4: The strong correlation with RPM - not there at all then fully on just 100 rpm higher.
Yes DERG feel free to answer a direct question or stop complaining about those who dont.
----
BTW On the natue of the noise: Hangflyer is it all all the same as what a distant "on the edge" of recpetion signal sounds like?
Possible the "white noise" without the chop?
Above with interference not active of course.
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Hangflyer
The bandwidth being taken up by this thread, which is also full of "noise", is environmentally unfriendly.
Wonder if you have offset it with carbon credits?
The bandwidth being taken up by this thread, which is also full of "noise", is environmentally unfriendly.
Wonder if you have offset it with carbon credits?
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Short intermission to watch a vid - this one has views of engine and instruments.
And I simply can't resist adding this one.
mm43
Sorry about the additional bandwidth!
Last edited by mike-wsm; 27th Feb 2011 at 07:33. Reason: vb center /center
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Relative "badness" of interference is the same at 200 meters (hangflywer stated direct line of sight to base station antennna) or at a significant distance, 20km would result in 40db Rx level difference.
Are we looking at some form of cross modulation, which includes a noise component?
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Quote:
You are implying, as I read it, that at 20km from the base transmitter, the signal is still readable and the apparent noise has reduced relatively by -40dB?
Are we looking at some form of cross modulation, which includes a noise component?
Basically yes, although the 200m is a fact the 20Km is an estimate I dont think hangflyer gave an exact number for max range.
The point is that the signal to (unwanted) noise ratio is staying the same over an impressive range of Rx signal levels.
As I postulated in prior posts I suspect some sort of signal cancelation (or possibly even boosting) effect, either from the prop (unbonded over a critical speed) or some other metalic element vibrating between bonded/unbonded. The ADF antenna is currently one prime suspect.
With just the right dimensions this would cause a significant and rapid Rx level fluctuation that could cause the AGC circuits to wig out.
Importantly this would also account for the extreme directionality of the "noise" since it would only happen if the element (approximatly) in line between the antenna and base station.
Relative "badness" of interference is the same at 200 meters (hangflywer stated direct line of sight to base station antennna) or at a significant distance, 20km would result in 40db Rx level difference.
Are we looking at some form of cross modulation, which includes a noise component?
The point is that the signal to (unwanted) noise ratio is staying the same over an impressive range of Rx signal levels.
As I postulated in prior posts I suspect some sort of signal cancelation (or possibly even boosting) effect, either from the prop (unbonded over a critical speed) or some other metalic element vibrating between bonded/unbonded. The ADF antenna is currently one prime suspect.
With just the right dimensions this would cause a significant and rapid Rx level fluctuation that could cause the AGC circuits to wig out.
Importantly this would also account for the extreme directionality of the "noise" since it would only happen if the element (approximatly) in line between the antenna and base station.
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Antennas when problem first described:
After higher-gain antenna installed in place of original:
No photo yet of new antenna mounted on underside, but it reportedly works a charm. Location? Proper base bonding? New coax?
After higher-gain antenna installed in place of original:
No photo yet of new antenna mounted on underside, but it reportedly works a charm. Location? Proper base bonding? New coax?
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The point is that the signal to (unwanted) noise ratio is staying the same over an impressive range of Rx signal levels.
Need to "chew the bone" over this.
Going back to when I was told that there is no advance/retard mechanism in the magnetos.
Web trawl tells me that Bendix 20/200 series are used on this engine.
They have impulse couplings. Which should drop out at 250rpm.
Two things.
1. Are the coupling pivots fitted with snap rings as they should now be? An AD relates.
2. Any chance that the start switch is malfunctioning and staying live?
Before I get my hat and coat, I can't help but focus on the fact that when the mags were replaced, the rpm at which noise occurs rose by a couple of hundred rpm.
Web trawl tells me that Bendix 20/200 series are used on this engine.
They have impulse couplings. Which should drop out at 250rpm.
Two things.
1. Are the coupling pivots fitted with snap rings as they should now be? An AD relates.
2. Any chance that the start switch is malfunctioning and staying live?
Before I get my hat and coat, I can't help but focus on the fact that when the mags were replaced, the rpm at which noise occurs rose by a couple of hundred rpm.
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Thanks Machaca for the pics.
Location, location ... and an intermodulation product related to the ADF seems now to "have" been the problem.
boguing;
That could explain when the noise cuts in. The snubbing capacitor becomes ineffective above a certain RPM due to the low impedance of the battery hanging across it. But hang on! If a starter is used, it must be a fairly high impedance "impulse" type, otherwise you could kill the permanent magnet.
Location, location ... and an intermodulation product related to the ADF seems now to "have" been the problem.
boguing;
Any chance that the start switch is malfunctioning and staying live?
Last edited by mm43; 26th Feb 2011 at 22:29. Reason: spelling!
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Boguing:
Yes, that does stand out. The new ignition bits can optimize engine operation and shift the harmonics to a different range, too.
I can't help but focus on the fact that when the mags were replaced, the rpm at which noise occurs rose by a couple of hundred rpm.
Yes, that does stand out. The new ignition bits can optimize engine operation and shift the harmonics to a different range, too.
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Antenna pics show a wire from rear of cabin to top of fin.
How does this interact with coms antennas?
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hangflyer -- a few questions if you don't mind:
1. Has the problem been present ever since you took possession of the aircraft?
2. Has previous owner of aircraft confirmed/denied this problem?
3. When was the IC-A210 installed?
4. The SoftComm?
5. Does the noise sound like the white, pink or brown noise at simplynoise.com ?
2. Has previous owner of aircraft confirmed/denied this problem?
3. When was the IC-A210 installed?
4. The SoftComm?
5. Does the noise sound like the white, pink or brown noise at simplynoise.com ?
Last edited by Machaca; 26th Feb 2011 at 23:20.
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Hangflyer I sent you a couple of PMs a few days ago.Nor sure it's of any use.
So do we have a mixture of the noise 'x' with another rf source 'y' that puts the resultant beat freq bang into the vhf comms band x + y , x-y etc Harmonics of resultant ? Mind boggles.
Is 'y' an oscillator in the receiver that only operates with received signal?
A spectrum analyser where we could see on a screen the rf frequencies and relative strengths would be useful as would being able to listen to the noise.
Many many years of experience working on the thread now.Not being able to actually experience it and listen is working blindfolded and is frustrating.
So do we have a mixture of the noise 'x' with another rf source 'y' that puts the resultant beat freq bang into the vhf comms band x + y , x-y etc Harmonics of resultant ? Mind boggles.
Is 'y' an oscillator in the receiver that only operates with received signal?
A spectrum analyser where we could see on a screen the rf frequencies and relative strengths would be useful as would being able to listen to the noise.
Many many years of experience working on the thread now.Not being able to actually experience it and listen is working blindfolded and is frustrating.
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Mig I believe they have already disabled just about everything to try isolating the noise to a piece of avio/elec equipment.
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Eureka!!! (maybe)
Once upon a time, when Design Engineers had permanent jobs and worked in Research Laboratories, our Research Director used to say we had all our best ideas when shaving. And he was right, it was after all the hard work of the previous day and a good night's sleep that a new idea would surface and we would bound into work shouting 'Eureka' and applying for patents.
Nowadays I take advantage of retirement to let my beard grow, so I don't have that shaving experience, but on Sunday mornings I soak in a piping hot bath and that has about the same effect. Today, for example, I was having that long hot soak and dreaming of exquisitely beautiful and sublimely aerobatic Fuji 200s painting elegant patterns in the sky.
One of the Fujis had an ADF aerial from cabin to vert stab and had its coms antennas fuselage topside beneath it. And I saw the radio waves approach that area and vanish.
At this point I have to explain that electromagnetic radiation consists of two perpendicular components which must travel together. One is electric and in this case is vertical, and the other is magnetic and is horizontal.
When the field approaches the tail of the aircraft, the loop consisting of metal fuselage and metal ADF aerial constitutes a shorted turn and prevents any magnetic field from existing in a direction perpendicular to the loop. This kills the loop as a path for the signal so there is no electric field for the coms aerial to pick up. The effect is only strong enough to kill the signal when it somes from directly ahead or astern.
The shorted turn does not have to be a continuous dc path, it only has to be a path at vhf frequencies, so a very small amount of capacitive coupling at each end will be sufficient to make it a short.
My suggestion is to fly (or taxi) with ADF aerial physically removed and check the coms using the remaining topside coms antenna. It shouldn't cost a lot to try and hf can either mail me a pickled wallaby or else have me consigned to the funny farm for demented Engineers.
When our Director told us his the ideas-when-shaving theory, we asked to be paid a shaving allowance, whereupon he went very quiet and then changed the subject.
Nowadays I take advantage of retirement to let my beard grow, so I don't have that shaving experience, but on Sunday mornings I soak in a piping hot bath and that has about the same effect. Today, for example, I was having that long hot soak and dreaming of exquisitely beautiful and sublimely aerobatic Fuji 200s painting elegant patterns in the sky.
One of the Fujis had an ADF aerial from cabin to vert stab and had its coms antennas fuselage topside beneath it. And I saw the radio waves approach that area and vanish.
At this point I have to explain that electromagnetic radiation consists of two perpendicular components which must travel together. One is electric and in this case is vertical, and the other is magnetic and is horizontal.
When the field approaches the tail of the aircraft, the loop consisting of metal fuselage and metal ADF aerial constitutes a shorted turn and prevents any magnetic field from existing in a direction perpendicular to the loop. This kills the loop as a path for the signal so there is no electric field for the coms aerial to pick up. The effect is only strong enough to kill the signal when it somes from directly ahead or astern.
The shorted turn does not have to be a continuous dc path, it only has to be a path at vhf frequencies, so a very small amount of capacitive coupling at each end will be sufficient to make it a short.
My suggestion is to fly (or taxi) with ADF aerial physically removed and check the coms using the remaining topside coms antenna. It shouldn't cost a lot to try and hf can either mail me a pickled wallaby or else have me consigned to the funny farm for demented Engineers.
When our Director told us his the ideas-when-shaving theory, we asked to be paid a shaving allowance, whereupon he went very quiet and then changed the subject.
Last edited by mike-wsm; 27th Feb 2011 at 15:28. Reason: typos and clarity
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Paddybee
Have scanned this thread and thought that maybe what you have is a Radio Symptom as opposed to a Radio Problem- ie the symptom manifests as a radio issue but the condition is totally unrelated. The various cases where the aircraft was used all day and issue was present, only to disappear when taken for ground testing makes me think: "What if this is caused by presence or absence of front seat pax, or caused by another factor in the flight profile that is concomittant to the RPM and not actually the RPM at all? AOA or trim at that weight/speed condition?" It appears that all the logical steps have been taken (for a radio problem) already. Good luck if this starts a new chain of thought.