Today's Message Index:
----------------------
1. 09:11 AM - cheapo 24 -> 12V dc-dc converters (Colyn Case)
2. 10:02 AM - Re: cheapo 24 -> 12V dc-dc converters (Rob Turk)
3. 10:34 AM - coax switches for sharing an antenna (Colyn Case)
4. 10:36 AM - Re: cheapo 24 -> 12V dc-dc converters (user9253)
5. 11:34 AM - Re: coax switches for sharing an antenna (Dick Tasker)
6. 02:40 PM - Re: cheapo 24 -> 12V dc-dc converters (Colyn Case)
7. 03:19 PM - Re: Z101 has been released under Rev A (Robert L. Nuckolls, III) (David Carter)
8. 03:44 PM - Re: Schottky diode voltage drop. (Colyn Case)
9. 04:00 PM - Re: coax switches for sharing an antenna (user9253)
10. 04:17 PM - Re: Z101 has been released under Rev A (Robert L. Nuckolls, III) (user9253)
11. 07:45 PM - Re: coax switches for sharing an antenna (Colyn Case)
12. 07:50 PM - Re: coax switches for sharing an antenna (Colyn Case)
13. 09:05 PM - Re: Re: coax switches for sharing an antenna (Sebastien)
14. 09:06 PM - Re: coax switches for sharing an antenna (Colyn Case)
15. 09:51 PM - Re: Re: coax switches for sharing an antenna (Sebastien)
Message 1
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| Subject: | cheapo 24 -> 12V dc-dc converters |
I have a 28V aircraft with a few critical items that run on 12V. I previously
used a Vicor VI-M11-ES but it became damaged and that model is no longer available.
What Vicor has available are mini-packs which require building up your own circuit
board and heat sinks. cost is $400 and several days of work for me.
So I found this thing on the net. data sheet attached. for $22. Includes heatsink,
leads etc. The worst thing I could find about it is .140V ripple.
but that beats the Vicor spec.
Any reason I shouldn't just use this thing?
--------
Colyn Case
colyncase@earthlink.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496547#496547
Attachments:
http://forums.matronics.com//files/daygreen_24v_to_12v_20a_240w_448.pdf
Message 2
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| Subject: | Re: cheapo 24 -> 12V dc-dc converters |
One thing to watch out for is that this is a switching power supply. You
can tell because it claims "High efficiency up to 95%". A linear
converter would convert half of the energy into heat. Although switching
regulators are everywhere these days, some are RF noisy, so you may hear
noise on your radio.
Rob
On 5/28/2020 6:07 PM, Colyn Case wrote:
>
> I have a 28V aircraft with a few critical items that run on 12V. I previously
used a Vicor VI-M11-ES but it became damaged and that model is no longer available.
>
> What Vicor has available are mini-packs which require building up your own circuit
board and heat sinks. cost is $400 and several days of work for me.
>
> So I found this thing on the net. data sheet attached. for $22. Includes
heatsink, leads etc. The worst thing I could find about it is .140V ripple.
but that beats the Vicor spec.
>
> Any reason I shouldn't just use this thing?
>
> --------
> Colyn Case
> colyncase@earthlink.net
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=496547#496547
>
>
> Attachments:
>
> http://forums.matronics.com//files/daygreen_24v_to_12v_20a_240w_448.pdf
>
>
Message 3
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| Subject: | coax switches for sharing an antenna |
I'm adding a second transponder to my carbon airplane and am out of places to mount
a second antenna. I would only be using one transponder at a time so I
am thinking of using a coax switch to select which transponder gets the antenna.
I'm not sure if these are built for my application, namely a transceiver
vs. a transmitter. Here's an example of one I am considering. Anything I
need to look out for here?
...and what does "latching" mean?
https://www.mouser.com/datasheet/2/404/CCR-33S_CR-33S_LATCHING-1228654.pdf
--------
Colyn Case
colyncase@earthlink.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496549#496549
Message 4
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| Subject: | Re: cheapo 24 -> 12V dc-dc converters |
You might also consider a converter with 13.8 volt output which is closer to an
aircraft
electrical system voltage with the alternator operating.
https://www.daygreen.com/collections/24v-to-12v-13-8v/products/24v-to-13-8v-20a-276w-dc-dc-step-down-converter-voltage-regulator
The AC ripple from an alternator is probably worse than a converter.
eBay has one for $17.50, free shipping from CA eBay item number:332791865341
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496550#496550
Message 5
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| Subject: | Re: coax switches for sharing an antenna |
My $0.02.
Looks like it would do the job. It does have a limitation of 100W capability at
the frequency band of interest. I am not sure what that rating is based on but
a modern ADSB transponder will put out
250W peak. If the limitation is based on continuous power output then I wouldn't
worry as a transponder is relatively low duty cycle. If it is based on internal
breakdown voltage or something
related to instantaneous power it could be a problem. Possibly you could contact
the manufacturer to find out more.
Latching means that you only have to energize the switch power momentarily and
the switch stays in that position until you energize the other switch input to
change to the other output.
Dick Tasker
Colyn Case wrote:
>
> I'm adding a second transponder to my carbon airplane and am out of places to
mount a second antenna. I would only be using one transponder at a time so
I am thinking of using a coax switch to select which transponder gets the antenna.
I'm not sure if these are built for my application, namely a transceiver
vs. a transmitter. Here's an example of one I am considering. Anything
I need to look out for here?
>
> ...and what does "latching" mean?
>
> https://www.mouser.com/datasheet/2/404/CCR-33S_CR-33S_LATCHING-1228654.pdf
>
> --------
> Colyn Case
> colyncase@earthlink.net
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=496549#496549
>
>
Message 6
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| Subject: | Re: cheapo 24 -> 12V dc-dc converters |
Joe, thanks for the link.
In this case I actually do want 12V but interesting to get another data point on
day-green.
--------
Colyn Case
colyncase@earthlink.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496554#496554
Message 7
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| Subject: | re: Z101 has been released under Rev A (Robert L. Nuckolls, |
III)
Quick question on this diagram: Near the upper left, there is a feed
coming off of the battery bus that is labeled for a 30A fused feed to
"BOBUS". Is that correct? I see two feeds coming into to the brownout / CD
bus: 1 from the diode bridge that feeds the engine bus, and one (switched)
directly from the battery side of the battery contactor.
Thanks!
---
David Carter
david@carter.net
Message 8
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| Subject: | Re: Schottky diode voltage drop. |
if you are interested in minimizing Vf it's worthwhile looking at the Vf curves
on the device you want to use. Here's one from the IXYS DSS2x81-0045B. A few
trends: Lower Vf is associated with lower current and with higher operating
temp. This particular device has two diodes in the package so you can cut
your current in half by using the two diodes in parallel.
--------
Colyn Case
colyncase@earthlink.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496558#496558
Attachments:
http://forums.matronics.com//files/dss2x810045b_vf_curve_680.pdf
Message 9
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| Subject: | Re: coax switches for sharing an antenna |
A switch will fail someday. Or a transponder will inadvertently be turned on
without an antenna connected. A transponder could be damaged. I suggest
that a second antenna be installed even if the location does not comply with
the manufactures suggested spacing. It will not hurt to locate a transponder
antenna closer to a com antenna than recommended because they operate at
considerably different frequencies.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496559#496559
Message 10
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| Subject: | Re: Z101 has been released under Rev A (Robert L. Nuckolls, |
III)
In the latest revision of Z101, the 30 amp fuse has been replaced with a
fusible link. Both the engine bus and the Brownout/Clearance Delivery bus
can get power from either the up stream or down stream side of the master
contactor. Your observations are correct.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496560#496560
Message 11
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| Subject: | Re: coax switches for sharing an antenna |
It's complicated. to be that close to the com antenna I would have to be physically
mounted in the metal that forms its ground plane.
Does the transponder blow up if its side of the switch is open?
--------
Colyn Case
colyncase@earthlink.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496563#496563
Message 12
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| Subject: | Re: coax switches for sharing an antenna |
nvm. i see there's a risk there...
--------
Colyn Case
colyncase@earthlink.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496564#496564
Message 13
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| Subject: | Re: coax switches for sharing an antenna |
I think most transponders have a supression line that is used to make sure
only one can transmit at a time. No switching required.
On Thu, May 28, 2020, 19:52 Colyn Case <colyncase@earthlink.net> wrote:
> colyncase@earthlink.net>
>
> It's complicated. to be that close to the com antenna I would have to be
> physically mounted in the metal that forms its ground plane.
>
> Does the transponder blow up if its side of the switch is open?
>
> --------
> Colyn Case
> colyncase@earthlink.net
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=496563#496563
>
>
Message 14
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| Subject: | Re: coax switches for sharing an antenna |
Wait. Does a transponder ever transmit without receiving anything?
--------
Colyn Case
colyncase@earthlink.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496565#496565
Message 15
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| Subject: | Re: coax switches for sharing an antenna |
Squawk Ident?
On Thu, May 28, 2020, 21:10 Colyn Case <colyncase@earthlink.net> wrote:
> colyncase@earthlink.net>
>
> Wait. Does a transponder ever transmit without receiving anything?
>
> --------
> Colyn Case
> colyncase@earthlink.net
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=496565#496565
>
>
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