Hi,
A proposal for the CW beacon is to transmit in 5 or 10 dB attenuation steps in order for someone to evaluate his receiving SNR. Maybe one of the two will be used this way.
proposal for beacon Hi
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... it's 1 S-unit.
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We did this with 5 MHz beacons 20 years ago. Set of tones each 6dB lower than the last. You counted how many you heard.
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Sounds good to me, I put this on the Agenda for our next internal QO-100 team meeting.. (in 3 weeks, will report here)
73s Peter
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Last year there was already a discussion regarding the CW beacon:
Yes, it is really helpful that after the conversion to FSK a quasi-constant signal level is available.
This made e.g. the alignment and optimization of a receiving antenna much easier.
A second receiving channel a few kHz below the (or above the upper) beacon (requires only a few GNU radio blocks) even allows real SNR measurements.
The proposed level stepping would unfortunately cancel out these advantages.
On the other hand, for the combination of an ancient transceiver and a converter, the proposal could certainly be useful.
So, as a compromise, please keep the lower CW-beacon unchanged and extend the upper one with the level stepping, if really necessary.
73 de Roland
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Or maybe 3dB steps ?
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Or maybe 3dB steps ?
You are in my mind !!! If it is accepted as a solution it must be tested also practically. The result will double counting steps. Also it has to be determined the time of each step.
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We did this with 5 MHz beacons 20 years ago. Set of tones each 6dB lower than the last.
Also Swiss amateurs had done that for the “new” 60 m band.
http://www.hb9aw.ch/bake-5000khz/
It’s OK for propagation studies for the Sort Wave bands but is useless for most of QO-100 satellite users.
We need more sophisticated applications and advance communication techniques to gain experience from the new bird.
73 Alex KM39gc
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It’s OK for propagation studies for the Sort Wave bands but is useless for most of QO-100 satellite users.
No, I do not agree with your statement. It's useful to optimize your receive chain from Dish+LNB to RX. In full duplex mode you also can optimize your uplink chain.
It's much easier to connect a high power amplifier and operating QRO, but this shouldn't be our goal to experiment.
73
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It's useful to optimize your receive chain from Dish+LNB to RX. In full duplex mode you also can optimize your uplink chain.
If you have to depend to your ears to optimize your reception chain, you are some ages behind. These days SDR is a must not only for the technical minded but for all operators (most of us have real Spectrum analyzers and VNAs).
Can you please tell me how can you improve the TX chain by monitoring the Beacon drop back 6 DB steps? How can you measure your Tx bandwith, IMD, 3rd order products etr? By ears!!!
73s Alex
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We can calculate pretty much exactly what the SNR should be. I don't think we are going to discover anything new here so it's more around helping new users determine how well their equipment is working. In full duplex you optimise your uplink by looking at it's spectrum and making sure it's clean. Regrettably there are many people who were sold black box solutions who frankly have not a clue about how satellites should be operated and because they are incapable of monitoring their own uplink because they decide to use an HF radio as driver they transmit excessive power, splatter all over the place and call off frequency. If the same station is also deaf, they don't see their splatter, but everyone else does. Such is life.
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I can compare my own signal with the beacon signal. OK, TX chain is not quite true but I have good ears.
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ZRO test...
During AMSAT-OSCAR-13 times, AMSAT offered the so-called "ZRO Memorial Technical Achievement Award Program" or just "ZRO Test". This activity was a test of operating skill and equipment performance.
During a typical ZRO run, a control station will send numeric code groups using CW at 10 words-per-minute. At the beginning of the run, uplink power from the control station is set to match the general beacon downlink strength. This is level "zero". The control operator will send and repeat a random five-digit number, then lower his uplink power by 3 dB (half power) and repeat the procedure with a new random number (level "1"). This will continue to a level 30 dB below the beacon (level "A").
A participating listener monitors the downlink signals till he can no longer copy the numbers. Those who can hear the beacon will qualify for the basic award by copying the code group heard at level "zero". The challenge is to improve home-station performance to a point where the lower-level downlink signals can be copied (levels 6 through A). To date, only one station (Darrel Emerson AA7FV) has successfully copied level "A".
https://www.cv.nrao.edu/~demerson/cs/zrodata.htm
The Weak-Signal Capability of the Human Ear
I'm not sure if such an ZRO test still makes sense as described above, but at least lowering the CW Beacon in 3dB Steps starting at Beacon level could be very useful for users to check the performance of their receiving systems as suggested by several users above.
We discussed this general idea in our AMSAT-DL QO-100 Team meeting today, but we still need to agree on some requirements/specification before implementation on the CW Beacon could even start...
Suggestions, Input is welcome...
73s Peter
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Hi, Peter,
I had already written it. A constant beacon level is extremely helpful, not only for the alignment of (portable) RX antennas. With a few GNURadio blocks you can easily measure >real< SNR values, wich quickly helps to improve all components of the receive chain.
Please keep at least the lower CW-beacon stable, if you really want to realize these gimmicks.
73 Roland
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I don't think its a gimmick, its a technical help to optimize the receiving part of the rig. We have 3 beacons with a stable signal yet, one we can use for such a "gimmick". Whether the lower or the upper CW beacon we can decide later.
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Hello all Sat-Oldtimers,
in cleaning up my shack, I found this paper.
Wouldn't it be nice, to create something similar for QO-100 ?
73, Martin DL9SAD
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Yes, it would be nice and fun, though in times of SDRs, spectrum displays and waterfall diagrams, there probably won't be a technical need for it.
For those not knowing what the ZRO test was: A station started to transmit in CW with beacon level equaling to ZRO level 0. Then the power level was reduced in steps of 3 dB increasing the achieved ZRO level by 1. So a ZRO level of 7 means 21 dB received signal range via the transponder.
