Replace C110

[rob...@thefrenchfamily.org]

C110, a 0.1 uF blocking capacitor between the antenna terminal and the LPF switching network, appears to have gone bad on my RS-HFIQ.  I say this because, with the antenna disconnected and the circuit unpowered, I can measure continuity across the capacitor (about 4.5k ohms)... I do not see any way for that to be happening in the circuit, unless the capacitor has failed.

The capacitor is specified as follows in the BOM:

CAP CER 0.1UF 100V X7R 0603

I have the following available:

50V 0.1uF X7R 0805

I realize I probably won't be able to shoehorn an 0805 into the footprint of a 0603.  I am curious however, what the real requirements for this part are, if I can find something in the junk box.  Does it actually need to be a 100V capacitor, or can it be a 50V?  I'd like to avoid shipping/handling of $7 or so from Mouser, to get a $0.1 part.

Thanks,

-Rob KC4UPR

[jcve...@gmail.com]

Hi Rob,

The manufacturer that built the boards offers free passives if we specified the specific components that they stock. I guess it costs less to give away the parts for free than to change reels of components for every job. Since they were free I went with the highers voltage rating available so the board would be as robust as possible. The DC blocking voltage at that point in the circuit is only a few volts but at 5W output the RF voltage is close to 20Vp. I'd say that a 50V cap would be fine in that application.

73,

Jim WA2EUJ

[jcve...@gmail.com]

Hi Rob,

Send me an email with you address and I'll put a few in the mail.

73,

Jim WA2EUJ(at)ARRL(dot)NET