Today's Message Index:
----------------------
1. 08:15 AM - Re: [Non-DoD Source] Re: Auto plug conversion (Bitterlich, Mark G CIV NAVAIR, WD)
2. 08:16 AM - Oil/air separator (Ryan Nelson)
3. 09:30 AM - Re: [Non-DoD Source] Re: Auto plug conversion (Roger Kemp)
4. 09:38 AM - Re: [Non-DoD Source] Re: Auto plug conversion (Jan Mevis)
5. 10:28 AM - Original Russian Tailwheel parts? (John B)
Message 1
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| Subject: | Re: Auto plug conversion |
Never thought I would disagree with Jan ...... but :-)
Jan, I agree with your math of course, but it's not commonly applied as a reason
of choice between modulation modes in my opinion. The final answer to your
comment regarding the number of sidebands is of course the bandwidth of the signal,
which you mentioned. Way back in the day when FM radios were using deviation
that was 30 or more KHz wide, I would have agreed with your rationale,
but that has changed tremendously over the years with better discriminator design.
While AM still has (in theory anyway) about a 6 KHz bandwidth, the receivers
are running about 10 KHz on their band pass requirements due in part to
past specifications that required wiggle room due to L.O. instability. Since
then, communication FM signals have lowered deviation to about 12 KHz, and recently
have cut that down over half using deviation of 2.5 KHz giving a total bandwidth
of 5 KHz. Thus current FM communication radios (in this country) have
bandwidth that is LESS than Amplitude Modulation !!
I believe the truth is, A.M. was the original design and F.M. was a "Johnny come
lately" and your reasons were indeed accurate back in the day. Today the
cost to re-equip every aircraft on Planet Earth would be cost and labor prohibitive,
but just for the reason you mention (noise detection) today FM radios would
be a much MUCH better choice as evidenced by the fact that commercial communication
has moved to it TOTALLY and they have even more restrictive bandwidth
requirements than we do.
Mark
-----Original Message-----
From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of Jan Mevis
Sent: Tuesday, March 08, 2016 2:03 AM
Subject: [Non-DoD Source] Re: Yak-List: Auto plug conversion
There's a good reason why AM is still used for VHF communication in aviation: smaller
bandwidth.
With FM modulation you have many more side bands (infinitely many, mathematically:
the signal can be developed with Bessel functions of the first kind).
If you have a modulation index of 2 (that means: the frequency sweep on the FM
signal is twice the angular speed of the modulating signal) then you have at least
three side bands on both sides of the carrier, as a rule of fist.
With AM on VHF you get more noise because the noise sits primarily on the amplitude,
and that's exactly what your AM demodulator is detecting.
J.
From: <owner-yak-list-server@matronics.com> on behalf of Frank Stelwagon <pfstelwagon@earthlink.net>
Subject: Yak-List: Auto plug conversion
One item no one has brought out was the poor decision years ago to stick with AM
radio for aircraft, AM is subject to pulse type interference and these aircraft
are huge generators of that. Also poor radio installation wiring is also
a major problem, follow the directions provided by the manufacture not the cheapest
way. I can't believe some of the trash that I have seen.
Frank
Message 2
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| Subject: | Oil/air separator |
Does anybody run an oil/air separator? If so, what one and where can I get it?
Thanks,
Ryan
218-969-7786
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=453563#453563
Message 3
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| Subject: | Re: Auto plug conversion |
Ah screw it. Turn the damned radio off and go fly. It's a big sky out there. Besides
ADSB is going to be our see and avoid savior.
Eye balls out!
Check 6
Doc
Said tongue in cheek.
Sent from my iPad
> On Mar 8, 2016, at 10:14 AM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich@navy.mil>
wrote:
>
>
> Never thought I would disagree with Jan ...... but :-)
>
> Jan, I agree with your math of course, but it's not commonly applied as a reason
of choice between modulation modes in my opinion. The final answer to your
comment regarding the number of sidebands is of course the bandwidth of the
signal, which you mentioned. Way back in the day when FM radios were using deviation
that was 30 or more KHz wide, I would have agreed with your rationale,
but that has changed tremendously over the years with better discriminator design.
While AM still has (in theory anyway) about a 6 KHz bandwidth, the receivers
are running about 10 KHz on their band pass requirements due in part to
past specifications that required wiggle room due to L.O. instability. Since
then, communication FM signals have lowered deviation to about 12 KHz, and recently
have cut that down over half using deviation of 2.5 KHz giving a total
bandwidth of 5 KHz. Thus current FM communication radios (in this country) have
bandwidth that is LESS than Amplitude Modulation !!
>
> I believe the truth is, A.M. was the original design and F.M. was a "Johnny come
lately" and your reasons were indeed accurate back in the day. Today the
cost to re-equip every aircraft on Planet Earth would be cost and labor prohibitive,
but just for the reason you mention (noise detection) today FM radios
would be a much MUCH better choice as evidenced by the fact that commercial communication
has moved to it TOTALLY and they have even more restrictive bandwidth
requirements than we do.
>
> Mark
>
>
> -----Original Message-----
> From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of Jan Mevis
> Sent: Tuesday, March 08, 2016 2:03 AM
> To: yak-list@matronics.com
> Subject: [Non-DoD Source] Re: Yak-List: Auto plug conversion
>
> There's a good reason why AM is still used for VHF communication in aviation:
smaller bandwidth.
>
> With FM modulation you have many more side bands (infinitely many, mathematically:
the signal can be developed with Bessel functions of the first kind).
>
> If you have a modulation index of 2 (that means: the frequency sweep on the FM
signal is twice the angular speed of the modulating signal) then you have at
least three side bands on both sides of the carrier, as a rule of fist.
>
> With AM on VHF you get more noise because the noise sits primarily on the amplitude,
and that's exactly what your AM demodulator is detecting.
>
> J.
>
> From: <owner-yak-list-server@matronics.com> on behalf of Frank Stelwagon <pfstelwagon@earthlink.net>
> Date: Tuesday 8 March 2016 at 01:15
> To: "yak-list@matronics.com" <yak-list@matronics.com>
> Subject: Yak-List: Auto plug conversion
>
>
> One item no one has brought out was the poor decision years ago to stick with
AM radio for aircraft, AM is subject to pulse type interference and these aircraft
are huge generators of that. Also poor radio installation wiring is also
a major problem, follow the directions provided by the manufacture not the
cheapest way. I can't believe some of the trash that I have seen.
>
> Frank
>
>
>
>
>
Message 4
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| Subject: | Re: Auto plug conversion |
Thanks for the corrections Mark!
I reasoned from the mathematical physicists point of view (which I am).
Time to study some real radio techniques!
Jan
On 08/03/16 17:14, "Bitterlich, Mark G CIV NAVAIR, WD"
<owner-yak-list-server@matronics.com on behalf of
mark.bitterlich@navy.mil> wrote:
><mark.bitterlich@navy.mil>
>
>Never thought I would disagree with Jan ...... but :-)
>
>Jan, I agree with your math of course, but it's not commonly applied as
>a reason of choice between modulation modes in my opinion. The final
>answer to your comment regarding the number of sidebands is of course the
>bandwidth of the signal, which you mentioned. Way back in the day when
>FM radios were using deviation that was 30 or more KHz wide, I would have
>agreed with your rationale, but that has changed tremendously over the
>years with better discriminator design. While AM still has (in theory
>anyway) about a 6 KHz bandwidth, the receivers are running about 10 KHz
>on their band pass requirements due in part to past specifications that
>required wiggle room due to L.O. instability. Since then, communication
>FM signals have lowered deviation to about 12 KHz, and recently have cut
>that down over half using deviation of 2.5 KHz giving a total bandwidth
>of 5 KHz. Thus current FM communication radios (in this country) have
>bandwidth that is LESS than Amplitude Modulation !!
>
>I believe the truth is, A.M. was the original design and F.M. was a
>"Johnny come lately" and your reasons were indeed accurate back in the
>day. Today the cost to re-equip every aircraft on Planet Earth would be
>cost and labor prohibitive, but just for the reason you mention (noise
>detection) today FM radios would be a much MUCH better choice as
>evidenced by the fact that commercial communication has moved to it
>TOTALLY and they have even more restrictive bandwidth requirements than
>we do.
>
>Mark
>
>
>-----Original Message-----
>From: owner-yak-list-server@matronics.com
>[mailto:owner-yak-list-server@matronics.com] On Behalf Of Jan Mevis
>Sent: Tuesday, March 08, 2016 2:03 AM
>To: yak-list@matronics.com
>Subject: [Non-DoD Source] Re: Yak-List: Auto plug conversion
>
>There's a good reason why AM is still used for VHF communication in
>aviation: smaller bandwidth.
>
>With FM modulation you have many more side bands (infinitely many,
>mathematically: the signal can be developed with Bessel functions of the
>first kind).
>
>If you have a modulation index of 2 (that means: the frequency sweep on
>the FM signal is twice the angular speed of the modulating signal) then
>you have at least three side bands on both sides of the carrier, as a
>rule of fist.
>
>With AM on VHF you get more noise because the noise sits primarily on the
>amplitude, and that's exactly what your AM demodulator is detecting.
>
>J.
>
>From: <owner-yak-list-server@matronics.com> on behalf of Frank Stelwagon
><pfstelwagon@earthlink.net>
>Date: Tuesday 8 March 2016 at 01:15
>To: "yak-list@matronics.com" <yak-list@matronics.com>
>Subject: Yak-List: Auto plug conversion
>
>
>One item no one has brought out was the poor decision years ago to stick
>with AM radio for aircraft, AM is subject to pulse type interference and
>these aircraft are huge generators of that. Also poor radio installation
>wiring is also a major problem, follow the directions provided by the
>manufacture not the cheapest way. I can't believe some of the trash that
>I have seen.
>
>Frank
>
>
Message 5
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| Subject: | Original Russian Tailwheel parts? |
Fellow listers:
Does anyone have a source for an axle bolt for the original Russian
tailwheel on a Yak 55? It is a 19 mm diameter bolt, with a special head.
John B
Phoenix, AZ
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