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
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