The joys of surplus....

Digital ATV - The latest generation, cutting edge ATV - Please discuss it all here.
Forum rules
This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.

Thank you
Post Reply
radiogareth
Posts: 496
Joined: Wed Jan 06, 2016 9:46 am

The joys of surplus....

Post by radiogareth » Mon Feb 03, 2020 6:00 pm

At the CATS Bazaar in 2018 I bought a pair of 'VHF pager amps'' mainly for the dual mosfet and heatsinks/fans that came with them. CLoser inspection revealed that each one had a CA2832C broadband amplifier module as part of the driver chain. https://www.digchip.com/datasheets/part ... 2C-pdf.php Trying to use the amp 'as-was' for DATV showed something was causing instability, so I removed the significant gain block and used a bit less drive. It worked, but not as well as my cheap Chinese 'VHF amp using a MRF186. However, with the advent of Pluto DATV and of course Lime derived signals, operation on 50/70/144 is relatively simple (no 50 for the Pluto).
About time I reused the handy little gain block. Unconditionally stable the data sheet says, +35dB 1-200 MHz too. I was planning on putting up a tinplate divider between input and output, but it does indeed seem to be stable without one. The 28 volts operating voltage is derived from an eBay XL6009 step-up converter board, available at £5.40 for 4 delivered. Additional filtering at the output was added to keep the nasties out of the amp. The heat sink came from a defunct 5.8GHz drone transmitter along with the little fan, running off a sub regulator at 3.3 volts. Just about keeps things cool as the amp is I suspect heavily biased for linear operation. It certainly produced a clean signal when driven from my MFJ as a test. A couple of SMA sockets, some standoffs and a grommet, along with a nice blue LED and on/off switch complete the gain block. I'll try feeding it with some DATV tomorrow as I check over the VHF contingent of my station.
Gareth
2020-02-03 17.32.24.jpg
2020-02-03 17.32.24.jpg (87.16 KiB) Viewed 473 times
2020-02-03 16.52.12.jpg
2020-02-03 16.52.12.jpg (120.29 KiB) Viewed 473 times

Post Reply

Return to “DATV - Digital ATV”