Video on QO-100

I had a lot of problems decoding the video beacon from the satellite. Decoding was intermittent and variable. I tried a number of solutions and concluded that the Channel Master 90cm dish had lost gain, possibly due to degradation of the fibreglass surface or the underlaying mesh.

I decided to buy a new dish. The Triax TD110 was available at a good price from a big dealership (Eurosat East) in nearby Ipswich. I also looked at the non-penetrating roof mount (sometimes called a pallet mount) that is just over 4 foot square and held down by 4 x 1 foot paving slabs.

Having got the dish on the mount I found it a bit flimsy compared to my CM on its 3inch ground mounted pole. Adjustment was a bit hit and miss as tightening bolts was enough to move the dish far enough to point away from the satellite position.

Eventually this was sorted by ensuring all bolts were adequately tightened, the truly awful elevation arrangement well lubricated and the mount held down firmly by more paving slabs.

After this was done the dish and mount became much more acceptable. I guess a professional installer would have already known and attended to all this. 

What has proved disappointing is that signal levels are about on a par with the CM, suggesting this dish was not seriously degraded after all! Oh well, it’s only money......

With the help of G4BAO and G8BHC it became possible to receive the video beacon and also at least one RBW signal.

What became clear is that I really had not taken enough care to align the dish well enough and with G4BAO’s experience the dish was successfully aligned. Expect to take a few hours to get this right.

However, not being happy with someone else showing me how it should be done and thinking I could do better.......I re-aligned the dish using the narrowband beacon as my reference level source.  This was better (sorry John and Martin....).

Another problem then became apparent and confirmed by G8AGN.

My Octagon OTSLO 25MHz is externally locked to a high quality OCXO. This works extremely well on the narrowband transponder.

When using this LNB,  video decoding was still a bit ‘iffy’. Substituting a similar OTSLO that had not been externally locked and running with a 27MHz crystal instead of 25MHz, video decoding was a lot better. Even with an Inverto DRO LNB, weaker RB amateur transponded signals were decoded better.

I decided to explore the level of 25MHz required to lock the original LNB. I found that the +1.5dBm was JUST sufficient to obtain lock and that at 6dBm it was far more solid. Not only that but the video now started to decode far more reliably. I did have to change the MMIC in the 25MHz  source for a higher gain one in order to get more output, but then had to attenuate the too-high 25MHz down to +6dBm to feed the RG58 going to the LNB.

With this change I was able to see and decode a lot of amateur video signals, at various symbol rates and levels, using the locked LNB and the SSB, CW and beacons on the narrowband transponder were being received extremely well on the 1.1m dish.

Barry, G8AGN, confirmed that he got better decodes with his non-externally locked LNB. I don’t know how much further he got with his.

My video beacon decode shows a steady MER of 6 whilst the amateur signals average a MER of 4.

Enough for now.

Sam

Update on yesterday’s blog

I finished the case but on test found that the SMPSU was providing far too much noise on the 25MHz reference output, so I have decided to change out the SMPSU for a linear one rather than try to filter the big one. That will mean a external PSU again, but will free some room in the case for some extra parts, to be decided.

I also found a problem with the LNB PSU to RSPPro2 (crimped) power connector lead into the bias tee. I’ve never seen this PowerPole intermittent problem previously, but will ensure I look for it next time!

A further update

I found that the original SMPSU, that fitted into the rear of this case, was completely RF quiet and spike free. In preference to using an external linear PSU I have grafted this SMPSU back into the case and am using it to power the reference OCXO/multiplier reference. Since  this PSU  is  rated at 50W (with small fan) I am going to try and use it to power the transverter as well, even though the overall 12V rating is marginal. As long as the OCXO is warmed up the total current draw is just about manageable. As the 5v/8A output is not being used, and neither is the slightly lower current rated SB 12v output, then the main 12V output should be comfortable at or slightly beyond that 12v output rating.  We’ll see what happen!

Sam

My Es-Hail update

Having now had several QSOs on the satellite narrowband transponder with parts of the system scattered around my shack and cable everywhere, I decided I really  ought  to rationalise the system in light of what I’d learnt.

The 5MHz OCXO based reference works well, so that is being retained. More on that in another blog.

Instead of combining the transverter and 25W PA in one large, weatherproof, Storno CQM case, initial tests have shown that with the antenna I am  currently using 1W is enought to exceed the level of the beacons, so the transverter goes in an internal 1U rack case with the 5>25MHz reference and a substantial 12V PSU.

A considerable number of bulkhead connectors on the rear of the 1U case bring in the 10MHz reference for the transverter (SGLabs), all the RF interconnectors for the transverter, including IF and RF input and output & PTT from the IF. Other connectors route the LNB IF coax through an internal link and back out, for later expansion facilities.

Also the 25MHz output to the LNB appears on yet another SMA connector.

The PSU is left on all the time, to power the 25MHz reference, whilst a substantial toggle switch is used to switch power on and off to the transverter and external 25W PA (via another switch to enable the PA, when required). See next day update on this PSU.

The LNB IF is routed to the operating desk where the 12v/18V polarisation switch PSU is located, together with a three way splitter for the Minitiouner, RSP2 Pro and the 738>144MHz downconverter.

I have done away with the separates (K3 and 144MHz transverter for receive IF and FT817 for transmit).

Whilst I wait for the IC9700 to arrive (it may have been delayed, from rumours about FCC acceptance problems around the recent US government financial shut down) I acquired a rather nice FT847 satellite transceiver at a very good price. This radio does full duplex satellite (it has separate IFs for transmit and receive) with normal or reverse tracking. This means just tune to the wanted downlink signal and as long as it is set up properly, the transmit is right on frequency. Nice!  It makes life so much easier. The IC9700 has the same facility.

I’ll cover the DATV side in another blog.

I started by using a HS 17.5dBi  flat plate antenna with the barefoot transverter and about 3dB of feeder loss. In other words, about 17-18dBW EIRP. My SSB signal was about 6dB SNR in 2.5kHz. This is a solutely marginal for comfortable SSB copy. I later discovered my transverter output was a bit lower than I thought.

However, I am going to provide the 25W PA as a switchable option in case it’s needed and to use with a few other antennas I want to try.

After the flat plate antenna QSOs I connected the transverter over about 1dB feeder loss to my 2.3m diameter EME dish with septum polariser 13cm feed for circular polarisation. I had to turn the power right down to stay below the satellite beacons!

Photo of the reverence/transverter case to follow.

Also the 25W PA on its separate heatsink.

Sam