Mark, N8MH noted:
The 437.024 transmitter antenna configuration on AO-16 is Left Hand Circular polarity (LHCP). The receiving antenna on the bird is a 1/4 wave vertical whip.
This whip operates against the body of the spacecraft as a "ground plane"; however the spacecraft body is a cube 22 cm on a side (you can see a picture at http://128.54.16.15/amsat-new/satellites/satInfo.php?satID=11&retURL=/sa... http://128.54.16.15/amsat-new/satellites/satInfo.php?satID=11&retURL=/satellites/status.php). This is about half of the quarter-wavelength you'd like to see for a proper ground reference, so the actual pattern undoubtedly has some weird nulls.
The fading is quite dramatic, which means the bird is spinning/tumbling, or some combination. We could never hear this before on AO-16 when it was transmitting its normal PSK signal, since we didn't hear the effect of fading on the uplink in this mode. Now we hear it, loud and clear!
It does take an uplink signal that is pretty close to on frequency (145.820). Adjusting for Doppler is helpful thing on the uplink.
The receiver has a 15 kHz wide crystal filter with sharp skirts. So if your NBFM xmtr is set with a ±5 kHz deviation, you may well find your signal hitting the filter "walls". You may get better performance if you crank the deviation back a bit.
73, Tom
On Jan 23, 2008, at 11:14 PM, Tom Clark, K3IO wrote:
The receiver has a 15 kHz wide crystal filter with sharp skirts. So if your NBFM xmtr is set with a ±5 kHz deviation, you may well find your signal hitting the filter "walls". You may get better performance if you crank the deviation back a bit.
Lots of folks who haven't worked on FM repeaters (or repeater coordination) don't realize that a 5 KHz deviation signal actually occupies 16 KHz, Tom. This is a great reminder, and knowing there's a sharp-skirted 15 KHz filter is great info for folks trying.
(Sadly, lots of repeater users don't know the difference between "deviation" and "modulation" these days, either -- but that's a whole different rant...)
This would also mean that if you're way off on correcting for doppler on the uplink you could ram into the skirts of the filter too... on modern rigs, go into those menus and set that FM step for as small a number as it'll go, and play around folks... you might find that fine tuning things a bit the correct direction for the doppler on the uplink might help a bit too.
A little lower deviation and a little more tuning and fiddling as needed with the uplink frequency, and voila!
Anyway this leads me to a thought, Tom -- for those who have modern FM rigs that have so-called "narrowband" mode (usually max 2.5 KHz deviation) would the satellite's FM receiver be fairly linear when fed with low deviation levels? I know it hurts on S/N ratio on the DSB downlink, but would 2.5 KHz deviation yield 50% modulation of the DSB transmitter, or is the FM receiver's audio output non-linear to some extent (like most are) and 2.5 KHz deviation would really be down to something like 30-40% modulated on the downlink?
It'd keep people from hitting the filter skirts as much, but if it yields really low modulation levels of the DSB transmitter, it'd probably hurt more than it would help. What do you think from what you know of the ol' girl's FM receiver audio setup? Any thoughts? Worth experimenting with the feature if folks rigs have that setting?
Neat stuff seeing the reports of those playing with the bird since she came back to life, both the control stations folks who did their magic, and now the end-users. Cool to read along!
-- Nate Duehr, WY0X [email protected]
The other thing you can do to lower your deviation is to lower your mike gain, or just not talk so loud.
Greg KO6TH
----------------------------------------
From: [email protected] To: [email protected] Date: Sat, 26 Jan 2008 03:06:20 -0700 CC: [email protected] Subject: [amsat-bb] AO-16 & FM receiver thoughts (was: AO-16 report from Copenhagen)
On Jan 23, 2008, at 11:14 PM, Tom Clark, K3IO wrote:
The receiver has a 15 kHz wide crystal filter with sharp skirts. So if your NBFM xmtr is set with a ±5 kHz deviation, you may well find your signal hitting the filter "walls". You may get better performance if you crank the deviation back a bit.
Lots of folks who haven't worked on FM repeaters (or repeater coordination) don't realize that a 5 KHz deviation signal actually occupies 16 KHz, Tom. This is a great reminder, and knowing there's a sharp-skirted 15 KHz filter is great info for folks trying.
(Sadly, lots of repeater users don't know the difference between "deviation" and "modulation" these days, either -- but that's a whole different rant...)
This would also mean that if you're way off on correcting for doppler on the uplink you could ram into the skirts of the filter too... on modern rigs, go into those menus and set that FM step for as small a number as it'll go, and play around folks... you might find that fine tuning things a bit the correct direction for the doppler on the uplink might help a bit too.
A little lower deviation and a little more tuning and fiddling as needed with the uplink frequency, and voila!
Anyway this leads me to a thought, Tom -- for those who have modern FM rigs that have so-called "narrowband" mode (usually max 2.5 KHz deviation) would the satellite's FM receiver be fairly linear when fed with low deviation levels? I know it hurts on S/N ratio on the DSB downlink, but would 2.5 KHz deviation yield 50% modulation of the DSB transmitter, or is the FM receiver's audio output non-linear to some extent (like most are) and 2.5 KHz deviation would really be down to something like 30-40% modulated on the downlink?
It'd keep people from hitting the filter skirts as much, but if it yields really low modulation levels of the DSB transmitter, it'd probably hurt more than it would help. What do you think from what you know of the ol' girl's FM receiver audio setup? Any thoughts? Worth experimenting with the feature if folks rigs have that setting?
Neat stuff seeing the reports of those playing with the bird since she came back to life, both the control stations folks who did their magic, and now the end-users. Cool to read along!
-- Nate Duehr, WY0X [email protected]
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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Greg D. wrote:
The other thing you can do to lower your deviation is to lower your mike gain, or just not talk so loud.
Greg KO6TH
Yeah, of course Greg. I was just thinking that punching the Narrow Band button is something "easy to teach".
Nate WY0X
Hi.
Looking for a control interface for my IC910H. CI-V (USB) and CT-17 (COM) is the converters i can find at the store. Can i use both, and since CT-17 cost alot more than CI-V , what will i be missing on the CI-V ?
Thanks
/ Brian OZ1SKY/5P22U
ICOM interfaces are just logic level ie 0 and 5 volts.
Yes they are expensive
Have you considered making your own ?
A max232 chip should work.
Either way, it just a way of getting from USB or SERIAL to TTL
---------------------------------------------------------------------------- Andrew Rich VK4TEC [email protected] mailto:[email protected] http://www.tech-software.net
-----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of Brian Houge Sent: Sunday, 27 January 2008 8:54 AM To: [email protected] Subject: [SPAM] [amsat-bb] IC910H control interface Importance: Low
Hi.
Looking for a control interface for my IC910H. CI-V (USB) and CT-17 (COM) is the converters i can find at the store. Can i use both, and since CT-17 cost alot more than CI-V , what will i be missing on the CI-V ?
Thanks
/ Brian OZ1SKY/5P22U
_______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
The CT-17 is in a nicer looking box, but you have to supply 12v to the CT-17, and every time you buy a new computer you need to worry about having a serial port to talk to the radio.
Except for the nice box, the CI-V is a better solution, self-powered, USB, drivers already built into linux.
jeff
Brian Houge wrote:
Hi.
Looking for a control interface for my IC910H. CI-V (USB) and CT-17 (COM) is the converters i can find at the store. Can i use both, and since CT-17 cost alot more than CI-V , what will i be missing on the CI-V ?
Thanks
/ Brian OZ1SKY/5P22U
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Thanks for the replys on my question.
I think ill go for the CI-V , its easy for travel and laptop use. Looking forward to some freq tracking from the pc etc.
Regards Brian OZ1SKY/5P22U
Yes, good point. We all tend to raise our voices when we aren't being heard, and that's exactly the wrong thing to do in this situation. Not intuitive at all. At least switching transceiver modes is something we can program into our tracking system, or adjust on the radio during a pass.
Greg KO6TH
----------------------------------------
Date: Sat, 26 Jan 2008 14:21:59 -0700 From: [email protected] To: [email protected] CC: [email protected]; [email protected] Subject: Re: [amsat-bb] AO-16 & FM receiver thoughts
Greg D. wrote:
The other thing you can do to lower your deviation is to lower your mike gain, or just not talk so loud.
Greg KO6TH
Yeah, of course Greg. I was just thinking that punching the Narrow Band button is something "easy to teach".
Nate WY0X
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participants (6)
-
Andrew Rich -
Brian Houge -
Greg D. -
Jeff Mock -
Nate Duehr -
Tom Clark, K3IO