[amsat-bb] Re: Devices in Icom preamps AG-25 AG-35

i8cvs domenico.i8cvs at tin.it
Thu Mar 18 17:28:00 PDT 2010

Hi George, KA3HSW

The 3SK121Y is a Dual Gate MOS-FET in package SOT 143R
and it can be directly replaced by the very inexpencive BF998R
with same package

See the cross reference here:


The Noise Figure of the BF998R is 1 dB at 800 MHz

See the data sheet here:


I hope this helps.

73" de

i8CVS Domenico

----- Original Message -----
From: "George Henry" <ka3hsw at att.net>
To: <amsat-bb at amsat.org>; "Mark L. Hammond" <marklhammond at gmail.com>
Sent: Thursday, March 18, 2010 4:54 AM
Subject: [amsat-bb] Re: Devices in Icom preamps AG-25 AG-35

> For the AG-35, it's a 2SK121Y.  Not sure about the AG-25.
> As others have mentioned, because of the proximity of the relay, one of
> easiest ways to replace it is to cut the leads on the old device, then
> & trim the leads on the new device to "straddle" the old leads & solder
> away.  Way easier than removing the relay...
> George, KA3HSW
> ----- Original Message -----
> From: "Mark L. Hammond" <marklhammond at gmail.com>
> To: <amsat-bb at amsat.org>
> Sent: Wednesday, March 17, 2010 5:29 PM
> Subject: [amsat-bb] Devices in Icom preamps AG-25 AG-35
> > Hello all,
> >
> > We either had two bad preamps to begin with, or they became casualties
> > during transport to K4T, but regardless--the Icom preamps we took appear
> > to have bad GAsFET devices in them.
> >
> > Can anybody tell me what is the device in each unit (AG-25 and AG-35)?
> > And are they something a skilled ham can reasonably replace?
> >
> > Specific suggestions for a parts source will be appreciated, too.
> >
> > 73,
> >
> > Mark L. Hammond  [N8MH]
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