On 03/15/20 13:48, Jeff Johns via AMSAT-BB wrote:
The general public seems to want more FM satellites, but organizations don’t seem to be building them and getting them into orbit fast enough to keep up with demand.
The single-channel, repeater-in-the-sky model was always destined for this sort of abuse (or simple ignorance). I've seen this happen on a local repeater, with a footprint of less than 50 miles. Why wouldn't it be expected on something with a footprint 100-1000 times as large?
Hams clamor for FM satellites because it reduces the cost of user equipment. Beofeng hasn't yet come out with a $30 2m/440 all-mode HT.
Linear satellites would work better for capacity, and better utilize the amount of bandwidth "lifted" to orbit by a launch vehicle. However, AMSAT can't alienate the $30 FM users, so it is a delicate balance.
Adding a linear transponder right alongside the FM card might work, but that incurs additional solar/power requirements which drives up system complexity, cost, testing, etc.
There are many variables, and it is impossible to optimize for them all. That's the engineering trade-off that I imagine AMSAT must face.
Here are a few of my thoughts:
Some enterprising soul should design, using common, off-the-shelf ICs, a simple PCB that is a SSB/CW 2m/440 duplex radio. Make the plans available freely on the WWW, etc. Get a groundswell behind it, and then watch the Asian clone makers swoop in and commercialize it (while also optimizing every last penny spent). Presto, lots of 2m/440 linear operators. Worked for nanoVNA, mikrocontroller's transistortester, etc. Should work for our crowd.
Also, donate early, donate often to AMSAT. Building, testing, and launching satellites isn't cheap, and your donations help put more birds into space.
"Cheap, fast, good. Pick any two."
--- Zach N0ZGO
On 03/15/20 16:48, Zach Metzinger via AMSAT-BB wrote:
The single-channel, repeater-in-the-sky model was always destined for this sort of abuse (or simple ignorance). I've seen this happen on a local repeater, with a footprint of less than 50 miles. Why wouldn't it be expected on something with a footprint 100-1000 times as large?
(*) slight correction -- Earth has a radius of ~3963 miles, so my "100-1000 times" statement was a little superlative. Let's go with 10-100 times. ;-)
--- Zach N0ZGO
Linear birds have more room but are being compromised significantly by poor receiving setups (low sensitivity) and transmitting with too much power, to be sure. (see my other post on this issue).
An additional problem that is causing just as much trouble on the linear birds is *failing to use doppler correction properly*. People come on and slide all over the passband and can't find themselves. Once they do, they cannot maintain a stable frequency relationship with respect to others on the birds.
As a result, they occupy multiple frequencies during the pass, covering up existing qsos that are practicing proper doppler discipline. *Basically, we are going through a period of transition where new operators have no idea what they are doing because they came from a single channel FM environment where doppler was practically non-existent, and making oneself as "full quieting" as possible has been rewarded with "yet another grid". *
The FM birds make 20 meter DX'ing seem like a picnic of social workers, especially on the weekends.
These FM birds encouraged and basically trained people into some horrible operating practices and at the same time failed to educate those same people how much different linear bird operation needs to be.
We need more Elmers. We need to provide feedback. When we observe these poor practices, we need to:
1. Look up their email (QRZ if available does nicely) 2. Write them a helpful note that explains: (in a straightforward, yet polite fashion)
a. What the problem is. b. Why it's problem c. How to cure it d. What the consequences are for the other ops and eventually for themselves if they continue to operate in these objectionable ways.
I do this a few times a week and include a link to an MP4 recording of the offending operation, so they can see and hear what their operating practices are doing t everyone else.
Let's lend a helping hand by making the extra effort to educate our fellow sat ops, so that this wonderful resource of linear birds is not turned into the wasteland that the FM birds have become (on weekends).
Who knows, it might help the FM birds as well.
73, N0AN Hasan
On Sun, Mar 15, 2020, 4:58 PM Zach Metzinger via AMSAT-BB < amsat-bb@amsat.org> wrote:
On 03/15/20 16:48, Zach Metzinger via AMSAT-BB wrote:
The single-channel, repeater-in-the-sky model was always destined for this sort of abuse (or simple ignorance). I've seen this happen on a local repeater, with a footprint of less than 50 miles. Why wouldn't it be expected on something with a footprint 100-1000 times as large?
(*) slight correction -- Earth has a radius of ~3963 miles, so my "100-1000 times" statement was a little superlative. Let's go with 10-100 times. ;-)
--- Zach N0ZGO _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Zach,
I've been contemplating a single band, transmit-only version of the QCX-SSB, developed by Guido PE1NNZ: QCX-SSB: SSB with your QCX transceiver (modification) https://github.com/threeme3/QCX-SSB
This is based on his work on Class-E driven SSB transceiver: Direct SSB generation by frequency modulating a PLL: http://pe1nnz.nl.eu.org/2013/05/direct-ssb-generation-on-pll.html
I saw something similar that was being done with a Teensy board, but that link appears to have broken.
I don't see a reason why this couldn't be adapted to 2m/70cm band operation by replacing the SI5351 PLL with one of the high- frequency versions of an SI570 PLL and a higher-frequency Class-E amplifier. I would keep it simple by having the transmitter filter for either 70cm or 2m. SSB reception could be done with any number of analog or SDR receivers.
I wish I had the time to work on this idea.
73,
Mac Cody / AE5PH
On 3/15/20 4:48 PM, Zach Metzinger via AMSAT-BB wrote:
On 03/15/20 13:48, Jeff Johns via AMSAT-BB wrote:
Here are a few of my thoughts:
Some enterprising soul should design, using common, off-the-shelf ICs, a simple PCB that is a SSB/CW 2m/440 duplex radio. Make the plans available freely on the WWW, etc. Get a groundswell behind it, and then watch the Asian clone makers swoop in and commercialize it (while also optimizing every last penny spent). Presto, lots of 2m/440 linear operators. Worked for nanoVNA, mikrocontroller's transistortester, etc. Should work for our crowd.
--- Zach N0ZGO _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
participants (3)
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Hasan al-Basri -
Mac A. Cody -
Zach Metzinger