Today's Message Index:
----------------------
1. 04:25 AM - Re: ELT antenna in Glasair (John Mireley)
2. 05:45 AM - Re: ELT antenna in Glasair (Hopperdhh@aol.com)
3. 06:25 AM - Re: ELT antenna in Glasair (Doug McNutt)
4. 08:37 AM - Re: ELT antenna in Glasair (Hopperdhh@aol.com)
5. 09:59 AM - Re: ELT antenna in Glasair (Doug McNutt)
6. 10:38 AM - Re: ELT antenna in Glasair (Hopperdhh@aol.com)
7. 12:05 PM - Re: ELT antenna in Glasair (Jim Ziegler)
8. 04:50 PM - Encoder harness (Jim S)
Message 1
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| Subject: | Re: ELT antenna in Glasair |
--> Avionics-List message posted by: John Mireley <mireley@msu.edu>
J. Oberst wrote:
> --> Avionics-List message posted by: "J. Oberst" <joberst@cox-internet.com>
>
> Just have a friend turn it on momentarily, while I'm far away (a mile?) with
> a handheld receiver. I know it works with a close-by receiver.
>
> It would be nice if we could test ELTs like they test our transponders, with
> a receiving antenna that measures the signal strength. But I've never heard
> of that.
>
> Jim.
Proper procedure for testing as stated in AC 43-16a
Note 3: Because the ELT radiates on the emergency frequency, the Federal
Communications Commission allows these tests only to be conducted within
the first 5 minutes after any hour and is limited to 3 sweeps of the
transmitter audio modulation.
Message 2
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| Subject: | Re: ELT antenna in Glasair |
--> Avionics-List message posted by: Hopperdhh@aol.com
Perhaps you could test on 121.45 and 121.55 to stay off the emergency
frequency. That way the transmitter could be a hand held com radio. This way
you
wouldn't have to limit the testing times, etc.
Dan K9WEK
RV-7A (almost done)
In a message dated 3/19/04 7:26:36 AM US Eastern Standard Time,
mireley@msu.edu writes:
>
> --> Avionics-List message posted by: John Mireley <mireley@msu.edu>
>
> J. Oberst wrote:
> >--> Avionics-List message posted by: "J. Oberst" <joberst@cox-internet.com>
> >
> >Just have a friend turn it on momentarily, while I'm far away (a mile?)
> with
> >a handheld receiver. I know it works with a close-by receiver.
> >
> >It would be nice if we could test ELTs like they test our transponders,
> with
> >a receiving antenna that measures the signal strength. But I've never
> heard
> >of that.
> >
> >Jim.
>
>
> Proper procedure for testing as stated in AC 43-16a
>
> Note 3: Because the ELT radiates on the emergency frequency, the Federal
> Communications Commission allows these tests only to be conducted within
> the first 5 minutes after any hour and is limited to 3 sweeps of the
> transmitter audio modulation.
>
>
>
Message 3
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| Subject: | Re: ELT antenna in Glasair |
--> Avionics-List message posted by: Doug McNutt <douglist@macnauchtan.com>
At 08:45 -0500 3/19/04, Hopperdhh@aol.com wrote:
>Perhaps you could test on 121.45 and 121.55 to stay off the emergency
>frequency. That way the transmitter could be a hand held com radio.
Yeah but. . . . Remember that the emergency frequency is really 243 MHz. Half
of that at 121.5 is only added so it can be heard by folks using VHF-only receivers.
--
--> The best programming tool is a soldering iron <--
Message 4
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| Subject: | Re: ELT antenna in Glasair |
--> Avionics-List message posted by: Hopperdhh@aol.com
Doug,
I not sure I get you point. There are really two emergency frequencies,
121.5 for VHF and 243 for UHF. Yes, they are harmonically related. But I think
that the receiver in the tower actually receives 121.5 for civilian aircraft.
If your antenna is effective on 121.5 that's good enough. My ELT does say
121.5 and 243, but the antenna is a 1/4 wave vertical cut for 121.5. It would be
a poor antenna at 243 since it is 1/2 wave at that frequency, and therefore
has very high impedance. That means that it would be a poor match for the 50
ohm feedline even if the transmitter has a strong 2nd harmonic at 243.
Dan
In a message dated 3/19/04 9:26:32 AM US Eastern Standard Time,
douglist@macnauchtan.com writes:
>
> --> Avionics-List message posted by: Doug McNutt <douglist@macnauchtan.com>
>
> At 08:45 -0500 3/19/04, Hopperdhh@aol.com wrote:
> >Perhaps you could test on 121.45 and 121.55 to stay off the emergency
> >frequency. That way the transmitter could be a hand held com radio.
>
> Yeah but. . . . Remember that the emergency frequency is really 243 MHz.
> Half of that at 121.5 is only added so it can be heard by folks using
> VHF-only receivers.
>
> --
> --> The best programming tool is a soldering iron <--
>
>
>
Message 5
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| Subject: | Re: ELT antenna in Glasair |
--> Avionics-List message posted by: Doug McNutt <douglist@macnauchtan.com>
At 11:37 -0500 3/19/04, Hopperdhh@aol.com wrote:
>I not sure I get you point. There are really two emergency frequencies,
>121.5 for VHF and 243 for UHF. Yes, they are harmonically related. But I think
>that the receiver in the tower actually receives 121.5 for civilian aircraft.
>If your antenna is effective on 121.5 that's good enough.
It's the receivers in the satellites that count and they were at 243 the last time
I was actually involved - and I admit that was two decades ago. Military aircraft
monitor guard at 243 which is in their usual voice band. Does anyone know
what civilian search crews use for direction finding?
A proper ELT antenna will be tuned for 243 with some attempt to make it work at
121.5 too. Mine, which came from Dorne and Margolin, is quite a bit shorter than
a 1/4 wave comm antenna. I calculate 31 cm (a foot) for 1/4 wave at 243 MHz
in free space.
--
--> As a citizen of the USA if you see a federal outlay expressed in $billion then
multiply it by 4 to get your share in dollars. <--
Message 6
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| Subject: | Re: ELT antenna in Glasair |
--> Avionics-List message posted by: Hopperdhh@aol.com
The antenna that came with my Ameri-King AK-450 measures about 23 3/4 inches
which is very close to 1/4 wave at 121.5 MHz. The length (in feet) of a 1/4
wavelength vertical antenna according to the ARRL Antenna Handbook is 234/freq
in MHz. 234*12/121.5=23.111 inches. I checked the SWR with it mounted to an
aluminum plate and it was best at 121.5. I didn't check it at 243 MHz, but I
will when I get time.
Dan K9WEK
In a message dated 3/19/04 12:59:43 PM US Eastern Standard Time,
douglist@macnauchtan.com writes:
>
> --> Avionics-List message posted by: Doug McNutt <douglist@macnauchtan.com>
>
> At 11:37 -0500 3/19/04, Hopperdhh@aol.com wrote:
> >I not sure I get you point. There are really two emergency frequencies,
> >121.5 for VHF and 243 for UHF. Yes, they are harmonically related. But I
> think
> >that the receiver in the tower actually receives 121.5 for civilian
> aircraft.
> >If your antenna is effective on 121.5 that's good enough.
>
> It's the receivers in the satellites that count and they were at 243 the
> last time I was actually involved - and I admit that was two decades ago.
> Military aircraft monitor guard at 243 which is in their usual voice band. Does
> anyone know what civilian search crews use for direction finding?
>
> A proper ELT antenna will be tuned for 243 with some attempt to make it work
> at 121.5 too. Mine, which came from Dorne and Margolin, is quite a bit
> shorter than a 1/4 wave comm antenna. I calculate 31 cm (a foot) for 1/4 wave
at
> 243 MHz in free space.
>
>
Message 7
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| Subject: | Re: ELT antenna in Glasair |
--> Avionics-List message posted by: Jim Ziegler <jcz@espllc.com>
>
> It's the receivers in the satellites that count and they were at 243 the last
time I was actually involved - and I admit that was two decades ago. Military
aircraft monitor guard at 243 which is in their usual voice band. Does anyone
know what civilian search crews use for direction finding?
>
The CAP uses 121.5.....
--
Jim Ziegler <jcz@espllc.com> jczatesp
Message 8
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--> Avionics-List message posted by: Jim S <gjs55@yahoo.com>
Hi all - first time posting. I am installing a Sandia SAE5-35 encoder, a KT-79
transponder and a KLN-94 GPS. The only system that will interface serialized (RS232)
data to the KLN-94, is proprietary with the Shadin Airdata systems, very
expensive and without an HSI, almost useless - already did this homework. So,
I must use the gray code to both the KT-79 & KLN-94. Sandia has confirmed their
units (mode c) output signal is strong enough to drive at least 3 individual
inputs. The question - from a professional point of view, should I parallel
the harness off the encoder (solder cups big enough for double 22 gauge wires)
to each unit or 'daisy chain' from one to the next? Either should work - just
looking for opinions on what might be best (and why). Thanks.
Jim
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