Posts by PA3FYM

Here are two recordings I just made:

11205H engineering beacon BW 500 Hz 20 dB SNR and tune steps of 10 Hz

11205H engineering beacon BW 500 Hz 6 dB SNR and tune steps of 10 Hz

A 'S1' signal (6 dB above the noise) is still good audible here.

DD4YR said: "As Remco already suspected, the frequency stability for SSB operation is hardly sufficient, for digital operation not at all. When watching the beacon of Es'Hail in CW, the frequency is constantly drifting, moreover the sound is "jammering" in the loudspeaker. A quartz heater improves the frequency drift, but the jammering remains ....."

Correct.

I did these experiments about a year ago using a GPS locked signal generator on 10489.7 MHz listening to my 70cm transceiver. My primary design goal was 0.1 ppb (1Hz) stability (NOT accuracy) on 10 GHz.

Listening to the tone on your receiver and dialing around/across the carrier is very 'educational' ; -)

The carrier my be 'accurate' in time but may be a punishment to listen to because of 'jammering'. The carrier may be stable, but may be a punishment to listen to because of a 'hiss' or noisy sound in SSB/CW.

Second VERY important issue is phase noise. I selected a VCXO (not having an NCO inside!) with very low phase noise, filter the output with a crystal filter to even further reduce the phase noise and locked it to a clean 10 MHz GPSDO. Of course the limit is the phase noise of the PLL LNB itself.

Third (also very) important issue is noise on the power supplies. Here, all relevant circuits are powered through 'denoisers' (capacitance multipliers, being an emitter follower with a (large) capacitor from base to ground).
One friend of mine got that far that he removed the 78L05 in his LNB (!)

When I listen to the EB's 'in CW' with 500 Hz BW filter the tone sounds 'like a bird' with my headphones. I also checked it with the weaker parts of the EB's and the response is nominal.

While writing this, I think about a following experiment:

1. Inject a (GPS locked) carrier in my 70cm receiver and measure the audio response as function of signal strength (noise, distortion etc.)

2. Repeat the same with the whole 10 GHz / LNB chain included.

Vielleicht ein Alternativ sind die Starcom LNB's (z.B. SR-3602).Die haben sicher 25 MHz PLL Takt und irgendwo habe ich gelesen dass 24 MHz Takt kein Problem war. 23.5897 is naeher zu 25 statt 27 MHz ; -)

Anyway, here the 11205 beacon shows a different spectral impact this morning compared to the last period. It now has two peaks +- 15 kHz (extra) on both sides of the main carrier.

By accident this evening I noticed a 'peculiar' profile for the 11205 MHz Es'hail-2 beacon.

Is this the 'time mark' ?

I repeated the same experiment with my implementation of locking the LNB to a 10 MHz GPSDO.

Couldn't find an easy way to reduce the waterfall speed sufficiently, so increased the FFT resolution to slow things down.

I am not disappointed. In the 100 Hz resolution screenshot some 'linear' jitter is visible, although also 'binary' drift (ca. 2 Hz) is present. I suspect the (warm!) RTL-SDR dongle since it's not disciplined and susceptible to environmental aspects.

E.g. when I approach the laptop where the dongle is inserted, some drift appears.

The 27 MHz LNB signal comes from an Abracon ASVV VCXO and is locked with an ADF4001 with PFD 1 MHz. As far as I could ascertain these VCXO's are not numerically controlled.

Anyway, it's fine for now. When I want to do narrow band digital modes (WSPR, JT9, FT8) further investigation is desirable.

@Pedro: nothing on 10701 H or V 24E here . . .

Hi Pedro,

Perhaps the Astra 2C (23.7° E) beacons may be useful for you, since you've a large dish.

First 10951.5 , then 11197. If both beacons appear then tune to 11205H and tweak the dish..

I had this one, and it was b00ming ...

Quote from DB2OS

There are no on-board beacon generators on the WB and NB.

The beacons and LEILA will be ground based and up-linked from the Es'hailSat SCC in Qatar. Our groundstation equipment will be installed and activated after the IOT phase is finished.

The process seems still in IOT-mode so . . .with which equipment / how are these (uplink) signals generated ?

Charlie Fox Mike here ; -)

I8LYL former I0LYL : I confirm, the signal is much stronger here now than my previous RX.

Arrived home just in time to record the WB transponder tests.

dg0opk : I congratulated Daniel with his beautiful captures : -)

However, I've a question (and please let the answer not be 'NDA' ...) :

Are these tests performed with an 2.4 GHz uplink (... from Doha) ?
(from what I understood there are no 'in situ' signal generators inside the NB and WB transponder allocation . . (?)

At this time of writing the beacon switches on and off (with varying signal strenghts). I have it here at 10489.675 (+/- RTL-TCXO deviations).

I reckon I also see the transponder noise. When I listen 1 Mhz higher or lower the noise floor here significantly decreases.

In the meanwhile, just for fun I made a 'poor mans' DJ7GP feed.

Will try to measure it tomorrow.

Quote from DJ7GP kleiner Peter

Hi folks,

here's a picture of the pre-production sample of my Duoband feed. Production starts in January.

Peter, DJ7GP

Hi Peter,

Looks very nice!

It looks like it's made from aluminium?

Hi Andreas,

You are right, it has no use to wait hours before a lock is obtained.

Thanks for the IK0OTG link, haven't seen that one before.

DL5MGD : I also experimented with a Ublox, but it was a 7M module. As PFD frequency I used several values, also 1 MHz and fed that to an ADF4351 PLL. On the frequency counter here everything looks nice, but when I listened in SSB to a carrier from a signal generator (and ADF4351 as LO for an RX-converter) there was still jitter audible, despite I used an integer value for the output reference frequency.

This was confirmed when I saw the signal on the oscilloscope.

You use the M8N, and I haven't digged into the datasheet yet, but does this module generate a frequency without jitter and/or did you 'dejitterize' that signal by using the OCXO in GPDSO mode?

Further, it would be nice if there is a version with 1PPS (1Hz) because that is what most GPS receivers are 'learned to produce' ; -)

Also beware that short helices over illuminate 'standard satellite offset dishes'.

A rule of thumb is that you need one turn per 0.1 'f/D'-unit.

Standard BC-offset dishes have f/D's around 0.7, so you need 6 - 7 turns to get the right main lobe.

Blue RHCP vs red LHCP (of course in front of a dish the helix
has to be LHCP but in the NEC-model it's RHCP).

vu3tyg : My 'beacon of salvation' is ArabSat 5A 30.5E 10706.009(7)H MHz to determine if 'everything works' as planned/expected. Since Dec 12 I can receive a faint trace of the Es'hail-2 10706-beacon. Before this time mark both beacons (10706 and 11205) came in good.

Since you are at +77.6° longitude you need a considerable amount of skew, try 45°. My observations (at ~5° longitude) are, when turning my dish to 30.5E in V-mode @10706 MHz I receive the ArabSat 5A beacon solid. Turning the LNB 90° (relative to the 'skewed' V-position) (a) second carrier(s) appear, as depicted in the picture below.

If you turn your dish (from your perspective) somewhat westwards and you switch to V-pol and see a carrier emerge it should be Es'hail-2 (provided that the 'assumed' MENA beam intrusively penetrates into your region ;- )