Posts by pe1chl

Fitting ferrite beads?

I heard DB2OS saying the same thing when he was making contacts at A71A.

He actually is 10dB above the noise here so it could be a lot lower...

The transponder is made by the manufacturer of the satellite, MELCO.

(Mitsubishi)

It is based on their standard transponders but with changes because of the different type of usage.

There are block diagrams in the presentations that were given by DB2OS during AMSAT-UK satellite colloquium and others, you can find them on Youtube in the AMSAT-UK channel: https://www.youtube.com/channel/UCmRRaBsigHc-hdEGL_6Zglg

The antennas are horn antennas (without dish) I think. Exact details are a bit difficult to get "because of NDA"

Why does it have to be FM? And why can't you talk back on the NB transponder?

Wouldn't it be sufficient to agree on an SSB talkback frequency on the NB transponder?

Quote from DN1HRZ

Why all the others need dishes ?

I did not try this yet (will try later today) but I was kind of expecting it because of the very strong signal via the dish.

However, I guess for optimal receive performance you need a small dish, maybe 30cm, at least.

Also remember that the usage is now quite low. When the entire transponder is populated like a HF band the power available to a single QSO decreases.

(even worse when the transponder goes into AGC due to that)

Easiest would be to set AZ and EL to optimally receive Astra2, then tune to the amateur transponder frequency and turn the dish slowly towards the west until you see the stations on the transponder (or at least the beacons) and optimize on those. The EL probably doesn't have to change for this small dish.

It is easy to find if your dish is optimally aligned once the bolts have been tightened by gently forcing the edges east-west and up-down and see if the signal improves when moved from the neutral position. If so, loosen the bolts and re-align.

When you have no access to the receive signal strength when you are handling the dish it is all a lot more difficult, so at least try to arrange that. 2nd best would be to have someone watching the receiver and issuing directions by shouting or using some handheld radios/phones, but this is a lot trickier than watching the signal strength while adjusting it yourself.

Quote from I0LYL

naturally every situation must be analyzed in the specific conditions. In any case, these two economic instruments allow you to make a very accurate aim in a few minutes. The analog instrument is very sensitive while the Sat Finder tells me if I'm aiming for the right satellite. The best solution compared to professional tools.

Yes the analog indications are the best. In the old days when SAT TV was still analogue FM it was so easy to point to the satellite, now with those digital receivers that show a meaningless "quality" and "AGC" value that always lags by a few seconds it is much more difficult.

However, the point is that you in Italy are lucky because you can receive the primary missions of those satellites, but in Northern Europe that is not possible or not so easy (there are a couple of BADR transponders that cover more to the North).

And for someone in say Brazil or Thailand even that is not possible.

So the location of the station really is important. In worst case only pointing to the amateur signals is possible. However, that is now possible because the beacons are on. Before Feb 14, one had to use other methods.

Ah, an FT-790R

I have one of those (and an FT-290R) in the "junkbox". Used it on OSCAR-10 and -13 (with home-made amp). There even exists a video (very bad quality) of our fieldday in 1985 where it was used

Now I am using an FT-817ND as part of the station for QO-100.

No, I have borrowed this antenna from a friend and he already warned me that it was behaving a bit funny. He has bent the dipole a bit to get good SWR.

It was only intended for first try, I will likely make a dualband feed later.

It looks like the BATC WebSDR has AGC enabled.

That is normally not a good thing for a WebSDR, it is better to have fixed gain.

But in practice it should not be a real problem, except that you cannot make observations about stations being too strong and cause the satellite to go into AGC.

Update: first uplink test made with 2W from LZ5HP transverter (not verified; according to others it could be 1W as well) via 10m of cable (-2.3dB) into SHF-1340 yagi (40el) which still needs optimization of pointing.

Result is: QSO possible but weaker than average station, should find some 5-6dB I think.

When visiting websdr.org, the parent site of the PA3FWM WebSDR receivers, the BATC WebSDR now appears at the top of the list, which is sorted to average number of listening stations.

Every time I have looked there, PA3FWM's own WebSDR (which uses different software and covers the entire HF bands) has always appeared at position #1. Now it is #2...

So it looks like P4A is quite popular

Quote from DL5RDI

For reception of BADR 4 BSS Beam in northern europe a big dish (>2m) is necessary.

Even in south east DL 120cm is recommended - with my 85cm I am at the edge - some weaker transponders are "unstable" at "bad weather".

73 de Johannes

It really depends on the actual location which he does not seem to want to reveal (hmmm...)

Here in JO22MC (center of Netherlands) the transponder 15 (11996) is received with about 7.5 dB S/N on a 80cm dish.

But of course in Scandinavia it will be much weaker.

Depending on the actual location there are different satellites that could be used as guidelines for first pointing efforts, e.g. Astra2 at 28.2 or Astra3 at 23.5 but without any more detailed location info it is difficult to recommend anything.

Quote from DL1QC

CW is fine for an old cw-enthusiast.

But a steady CW-Carrier for around 5 - 10 seconds for measuring between the rounds would be fine.

Well, I meant morsecode sent as FSK so still easily receivable for a CW enthousiast (with proper filtering and tuning) but within a somewhat larger passband (SSB) it would have constant amplitude.

But indeed, a ling tone between the text in the loop would be fine as well!

Quote from DB8TF

What is now with the TX Power Level?

When i transmit a CW Signal it is About 10dB above the PSK telemetry.

Is that to much Uplink power ?

vy73 DB8TF

Display More

Yes, according to the recommendation given before.

Now that there are only a couple of stations active (or none at all) of course the power budget calculation that assumes 50 parallel QSOs is not really valid and required power could be lower.

You should take back tx power especially for CW.

I think the lower beacon would better transmit FSK instead of CW so it is easier to compare to the amplitude (same as terrestrial UHF/SHF beacons usually do)

Quote from DD4YR

Can someone measure the exact beacon frequencies?

My equipment shows the beacon freqcuency 55 kHz higher as expected ....

The downlink frequencies you see should be 10489.550 and 10489.800

(as published before)

There is a picture on page 2 of this topic. Those splitters are readily available from satellite-TV equipment stores and webshops.

But this is not at all critical. I made my own bias-tee from some junkbox parts.

The LNB has such a high gain that anything you do to the IF signal (like lossy cable or splitters) really doesn't matter, you already need to turn down the gain of the RTL sticks by 20-30 dB to avoid overdriving them...

I'm guessing the beacons are from the Bochum backup site and not from Qatar.

(also because of the callsign DL50AMSAT)

Or else they are doing very long workdays there...

Ok that is important because then you cannot use the transmitters of the primary mission of the satellite as guide when pointing the antenna.

In the early days there were engineering beacons that you could use but they have switched over to the narrow beams that are only receivable in the arab region.

Same for the DVB transmissions. Those cannot be received in Northern Europe with small dishes.

So you need to tune to the amateur transponder frequency and use that for fine pointing.

You are right, just calculating the AZ and EL and then pointing there is not going to work. It can be used as a first guess but then you need to just move around that position and optimize the signal.

Many transmissions yesterday and even more today were just too strong....

Those stations will need to reduce their power to fit the level set by the beacons.

(that is one of the purposes of those beacon signals)