Quoting Patrick McGrane [email protected]:

Greetings from pat n2oeq

I have been looking forward to the launch of P3E which I thought was going to be this year. I am concerned about the germans use of the SDR technology over william Liejanier's transponder design. I am of the belief that signal processing presents a loss in the path, please correct me if I'm wrong. Williams Hamsat transponder is excellant and made me very interested in P3E. Besides making the voice unnatural, are other modes allowed through the SDR transponder? Does the Helaps system compensate for the loss? I'm of the Keep it simple discipline as once its up there nothing can be done to fix it.

If amsat-dl is monitoring , please update your website and provide a direct Paypal donation utility.

Thanks to amsat-na for the donation to P3E recently. 73, pat

The amsat-dl article "Launches Speak Louder Than Words", published in May 2006 http://www.amsat-dl.org//index.php?option=com_content&task=view&id=6... noted that Nov. 2008 was the first relatively secure date. I believe more recent sources have suggested that the bird will be ready in Spring or Summer of this year. Perhaps there is some hope that a more recent launch opportunity will arise.

From my reading, and I'm not an expert, SDX technology is predicted to be

indistinguishable from a linear xponder to the ground station: I have read no account of entailed losses. What it *does* aim to provide is a newly flexible and configurable bent pipe. One obvious application is to limit the amount of output power in a given portion of the passband, thereby reducing the impact of alligator stations. The audio files posted on this list indicate no unnatural artifacts to my ear, and such transponders are routinely built to operate with varying modulation schemes.

As this technology matures, one could imagine groundstations developing 'applets' for the SDX. For instance, imagine an bit of SDX code that listens on a certain very small passband and responds to any CW signal with a report that indicates that signal's average power in dBm or dB above noise, or what have you. This would be an invaluable tool for calibrating a station! What if the report were sent three times, each signal 10 dB lower than the previous (something like the IARU beacons); then you'd have some hard numbers on how your Field Day station was performing on both uplink and downlink.

My point is that SDX allows us to dream of these things, and potentially to implement them even after the bird is up. Yes, it entails a risk. We're fortunate to be able to mitigate this risk: SuitSatII will fly with SDX on-board so that we can test this technology. To my mind, the satellite service/hobby is a branch of the hobby that continues to fulfill the experimental origins of amateur radio. We need to do so prudently, given the cost of launching the hardware into space, but I think the SDX concept fits nicely within that curve.

73, Bruce VE9QRP

At 11:28 PM 3/23/2007, Patrick McGrane wrote:

Greetings from pat n2oeq

I have been looking forward to the launch of P3E which I thought was going to be this year. I am concerned about the germans use of the SDR technology over william Liejanier's transponder design. I am of the belief that signal processing presents a loss in the path, please correct me if I'm wrong.

Why would it be a loss? SDR represents an opportunity to improve the passband characteristics, and increase the dynamic range of the transponder, as well as make other tweaks. Depending on the design, there is also the potential to upload new passband characteristics and tweak the transponder while it's in space (sort of the equivalent to hitching a ride on a rocket and making a few tweaks :) ).

Williams Hamsat transponder is excellant and made me very interested in P3E. Besides making the voice unnatural, are other modes allowed through the SDR transponder?

Why would a SDR make voice unnatural? All the SDR is doing is replacing the traditional analog filters with digital ones, which gives much steeper skirts. The DSP also offers the opportunity to deal with alligators and maybe even dynamically share the transponder power equally between all stations.

Does the Helaps system compensate for the loss?

HELAPS is a high efficiency linear PA. Needed, regardless of whether the transponder is analog or digital.

I'm of the Keep it simple discipline as once its up there nothing can be done to fix it.

On the other hand, what the system offers is the potential to dynamically configure the passband. Got non ham QRM sucking power from part of the passband? Just notch it out, for example.

While it is good to have old style analog transponders available as a standby, we do need to look to the future and embrace new technology. What is the point of spending millions and occupying our bands to put up another satellite with 1970's RF technology, when there are experiments we can fly using the latest technology? I have nothing against a tried and true analog transponder as a backup (if space and weight constraints permit, that's prudent), but I do like to see new technology used as well.

73 de VK3JED http://vkradio.com

Very similar SDR technology has been used in amateur HF transceivers for years with no complaints. SDR can be used to compensate for losses in the analog circuitry.

73,

John KD6OZH

----- Original Message ----- From: "Patrick McGrane" [email protected] To: [email protected] Sent: Friday, March 23, 2007 12:28 UTC Subject: [amsat-bb] P3E transponder and launch

Greetings from pat n2oeq

I have been looking forward to the launch of P3E which I thought was going to be this year. I am concerned about the germans use of the SDR technology over william Liejanier's transponder design. I am of the belief that signal processing presents a loss in the path, please correct me if I'm wrong. Williams Hamsat transponder is excellant and made me very interested in P3E. Besides making the voice unnatural, are other modes allowed through the SDR transponder? Does the Helaps system compensate for the loss? I'm of the Keep it simple discipline as once its up there nothing can be done to fix it.

If amsat-dl is monitoring , please update your website and provide a direct Paypal donation utility.

Thanks to amsat-na for the donation to P3E recently. 73, pat

---

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

At 10:46 AM 3/24/2007, John Champa wrote:

Guys,

The reports I have seen is that the SDX sounded BETTER than the traditional analog transponder. Bob, N4HY, can confirm that fact?

I wouldn't be surprised at this one at all.

Anything other than SDX would be a step-backward for AMSAT.

That's my viewpoint as well.

73 de VK3JED http://vkradio.com

Thanks to everyone for the comments, concerns, and thoughtful remarks.

SDX is no magic bullet. It cannot perform any better than the analog hardware around it and our careful work on doing the mixed signal work and even more careful work to make sure it survives the rigors of traveling through Van Allan radiation belts four times a day!

That said, it provides us with several things. The DESIGN of the SDX will allow us to use a high dynamic range receiver in comparison to those we have flown before and to actually realize the potential presented to us by this receiver.

If we have this high dynamic range receiver, we can use a much lower noise floor and wider dynamic range transmitter to provide cleaner signals. This will be evidenced, if we do it right, by us no longer hearing the noise floor of the transponder. Next, if we have sufficient DSP horse power, we will be able to mitigate PAVE PAWS pulses by doing pulse detection and subtraction. THIS IS A LINEAR OPERATION. It will be much nicer than clipping. If the pulses get so large that we are clipping then all bets are off but with an 80 dB dynamic range receiver, this will be much less likely to happen. Stephensen has done a detailed analysis of this and this is available on Eaglepedia.

Next we are designing in the ability to provide the most capable HELAPS we have ever done. HELAPS is high efficiency linear amplification by parametric synthesis. Technical papers by Karl are on both the AMSAT and AMSAT-DL web sites. It is envelope elimination and restoration amplification. It allows us to use very high efficiency nonlinear amplifiers in the transmit chain and then have the "envelope" of the hard limited signals from the transponder imposed on the signal just before it hits the antenna by modulating the voltage on the last or last few stages. If we do the final transistors and the driver, we can get VERY high efficiency compared to what we have achieved in the past WITHOUT all of the poor IMD we lived with to get the efficiency. SDX is THE enabler in this.

SDX provides us with the ability to easily find all alligators and impose our will on them. There will simply be no benefit to running an EIRP that is larger than we decide to allow because YOUR INDIVIDUAL signal will be suppressed!

Juan Rivera, WA6HTP, and his team are building the fancy receiver which has been designed by KD6OZH and peer reviewed to death by others. Parts are being purchased NOW and the goal is to have four soon. We are building at least one to fit the P3E box shape.

Marc Franco, N2UO, has designed, using modern parts that are very difficult to get without connections, a serious 2 meter final stage. It will provide the highest efficiency 2 meter transmitter we have ever flown for HELAPS.

Steve Hendricksen, a TCNJ engineering student, design a S band amplifier in a senior engineering project directed study for Marc, Al Katz (K2UYH), and I. He submitted this for competition in an amplifier efficiency contest. He received an honorable mention and came in very high in the rankings. However, his amplifier was the only one well in excess of the minimum power, at 2.4 GHz rather than 1.0 GHz (the contest minimum).

As always there is the balance between "new with great promise but untried" and "the old, standard but somewhat outdated". We can have this argument all year and it will never be easily resolved.

AMSAT-UK has agreed to provide SDX software working with P3E and Eagle teams. They have agreed to copy the AO-13 RF if none of these fancier elements shows up and works. AMSAT-DL is planning for these contingencies.

So we have arranged for a small trial: Suisat-2 will carry a low power SDX with a few of these capabilities. We are planning a very large AMSAT engineering activity for this coming summer which you will hear more about in the coming weeks.

I could go on but what I want to promise is this: I have been extremely busy both professionally, personally, and with AMSAT things and I have not done an Engineering Notebook in a while. I will do a detailed paper on this for the next journal and it will be in my engineering notebook. Following publication I will put the document with more backing material on Eaglepeda as well and give it to AMSAT-DL for both our sites.

Bob N4H

Tony Langdon wrote:

At 10:46 AM 3/24/2007, John Champa wrote:

...

Guys,

The reports I have seen is that the SDX sounded BETTER than the traditional analog transponder. Bob, N4HY, can confirm that fact?

I wouldn't be surprised at this one at all.

...

Anything other than SDX would be a step-backward for AMSAT.

That's my viewpoint as well.

73 de VK3JED http://vkradio.com

DO IT TODAY. We need the money for the launch campaign, and completion of building!

Bob

Peter Guelzow wrote:

Patrick McGrane wrote:

...

If amsat-dl is monitoring , please update your website and provide a direct Paypal donation utility.

Hi Patrick,

if you follow the instructions on https://www.p3e-satellite.org//index.pl?step=dabeisein;image=p3express.jpg than you have the option to pay using PayPal... Due to handling charges, direct credit card would be still the preferred option..

Thanks for your donation!

73s Peter, DB2OS

BTW: Don't worry about the SDX.. it's the only way how we can have LEILA/STELLA on P3-E and I expect this to be a big advantage...

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