Ridgeway Microwave Round Table
Posted: Sun Feb 02, 2025 10:39 am
Hello everyone,
Joan (2E0HIZ) and I, attended the inaugural Ridgeway Microwave Round Table at Chilton Village Hall yesterday as did about 80 others. It was an excellent event with lots of familiar BATC faces and others interested in amateur TV as well as microwaves, with a couple of good talks, bits and pieces to buy (also freebies) and lots of 'show and tell'.
I took along a portable system to demonstrate reception of the QO-100 wide-band beacon on a smaller antenna and there were a number of people who were interested, so I thought that it may be useful to detail the demo. setup:
Antenna Offset parabola 71cm (across face) [believed to be a Triax TDS80]
LNB Octagon, LO 9750MHz, dual output (converted for locking but not used)
Receiver Minituner MkII
Display Portsdown 4, running built-in Longmynd Rx software
Antenna alignment used the Portsdown 4 Band Viewer with a SDRPlay RSPDx, initially capturing the QO100 narrow-band beacon, then switching to the large display 'MER meter' for fine pointing using the wide-band beacon. Using this method alignment took less than 5 minutes, although it is useful to have the elevation roughly set in advance. To receive both the narrow-band and wide-band transponders, you must have the capability to select the LNB volts for the correct downlink polarisation (eg 14V vertical for narrow-band/18V horizontal for wide-band).
With the 71cm antenna, the wideband beacon MER with no other carriers present was about 7.8dB (margin over threshold of about 3.1dB). Going to a 90cm should improve the MER further by a dB or more, depending on the dish.
If anyone is having difficulty with reception, I strongly suggest trying a different LNB type.
73
Jen G4HIZ
Joan (2E0HIZ) and I, attended the inaugural Ridgeway Microwave Round Table at Chilton Village Hall yesterday as did about 80 others. It was an excellent event with lots of familiar BATC faces and others interested in amateur TV as well as microwaves, with a couple of good talks, bits and pieces to buy (also freebies) and lots of 'show and tell'.
I took along a portable system to demonstrate reception of the QO-100 wide-band beacon on a smaller antenna and there were a number of people who were interested, so I thought that it may be useful to detail the demo. setup:
Antenna Offset parabola 71cm (across face) [believed to be a Triax TDS80]
LNB Octagon, LO 9750MHz, dual output (converted for locking but not used)
Receiver Minituner MkII
Display Portsdown 4, running built-in Longmynd Rx software
Antenna alignment used the Portsdown 4 Band Viewer with a SDRPlay RSPDx, initially capturing the QO100 narrow-band beacon, then switching to the large display 'MER meter' for fine pointing using the wide-band beacon. Using this method alignment took less than 5 minutes, although it is useful to have the elevation roughly set in advance. To receive both the narrow-band and wide-band transponders, you must have the capability to select the LNB volts for the correct downlink polarisation (eg 14V vertical for narrow-band/18V horizontal for wide-band).
With the 71cm antenna, the wideband beacon MER with no other carriers present was about 7.8dB (margin over threshold of about 3.1dB). Going to a 90cm should improve the MER further by a dB or more, depending on the dish.
If anyone is having difficulty with reception, I strongly suggest trying a different LNB type.
73
Jen G4HIZ
