LO Filter...

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
g0mjw
Posts: 2330
Joined: Sat Sep 20, 2014 9:15 am

Re: LO Filter...

Post by g0mjw » Thu Jan 04, 2018 8:00 am

Actually, the link was to a current limiting PSU. Not about using too many volts.

It's very helpful in preventing damage when making circuits. The maximum current can be set to a value, if it is exceeded, the PSU shuts down. It won't prevent all damage but a good number of times it will. I always use some form of bench PSU with current limiting when testing.

Mike

G3UKV
Posts: 19
Joined: Fri May 12, 2017 6:19 pm

Re: LO Filter...

Post by G3UKV » Thu Jan 04, 2018 9:16 pm

Hello All
Having same trouble as Mike - the RF output switch IC ADG904 is out of stock at Digikey (ADG904BRUZ-ND) and Farnell (2074875). Suppliers now saying JULY for delivery - yuck!
Anyone got a spare please? (will refund costs, of course).
Similar trouble with 0805 Caps - 25uF at 25V for LO filter PCB. Didn't notice the Farnell part nr. (1907510) N/A until May when I placed the order for two. Obviously similar component available elsewhere, but subject to small order charge etc. Anyone spare a couple, please ? (costs paid).

MN-tech
Posts: 59
Joined: Thu Aug 30, 2012 6:01 pm

Re: LO Filter...

Post by MN-tech » Thu Jan 04, 2018 10:38 pm

The ADG904BRUZ connects a 50 ohm resistor to the unconnected switch terminals. The ADG904BRUZ-R connects them to ground.
On the output switch board these terminals connect to the pre-driver inputs so a short to ground should be OK unless your pre-amp becomes unstable under this condition.
That is not the case for the LO filter.

g0uhy
Posts: 81
Joined: Fri Aug 05, 2011 3:09 pm

Re: LO Filter...

Post by g0uhy » Thu Jan 04, 2018 10:55 pm

Hi,

I've got a couple of the required chips spare but unfortunately not the 22uF caps.PM me and I'll see what I can do to help.

73

Malcolm G0UHY

g8gtz
Posts: 1733
Joined: Wed Apr 07, 2010 6:26 pm

Re: LO Filter...

Post by g8gtz » Fri Jan 05, 2018 9:22 am

I've also got a couple of spare ADG904BRUZ-R which is OK for the RF switch if anyone needs them.

Noel - G8GTZ

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