[Amps] PIN diode discussion

Bob D. ajamas.rn at gmail.com
Tue Mar 16 12:27:09 EDT 2021

Duck Duck found a thesis from 1990.

I learned a bit about minority carriers.


The author measures a 1N4007 and describes a method one might try at home.

73,. -bob ah7i

> Message: 2
> Date: Tue, 16 Mar 2021 07:32:43 -0400
> From: "Paul Christensen" <w9ac at arrl.net>
> To: <amps at contesting.com>
> Subject: Re: [Amps] Looking for Alpha 87A expertise
> Message-ID: <004001d71a58$1508c720$3f1a5560$@arrl.net>
> Content-Type: text/plain;       charset="UTF-8"
> >"Anything under 2ms  (2 milliseconds = 2000 microseconds, which is a
> whole bunch of nano seconds) is WAY MORE then enough for most transceivers.
> (Which was the point I was trying to make here)."
> A diode's forward bias transition time is one important parameter but when
> considering PIN diodes for use in the Alpha 87A, the diode's minority
> carrier lifetime may be an even more important parameter.  The purpose of
> the intrinsic region between the P and N wafers is to store a charge long
> enough to keep the diode from rectifying RF during a complete cycle.  For
> us, the worst- case band of operation is 160m (excluding the two LW
> bands).  For 160m, the carrier lifetime computes to approx. 0.5 us.  But,
> typically much more time is required to minimize IMD products.
> When used as an HF T/R switch, Microsemi recommends 1A of DC current to
> fully bias the UM2100 series diodes -- and nearly 1KVDC reverse bias on the
> receive PIN when HF power levels reach 1KW.
> I believe ETO/Alpha originally spec'd the MA4P4006D for the transmit PIN
> which was superseded by the identical UM4006 when Microsemi acquired the
> product line.  I hear rumors that Alpha has been recommending 1N4007 diodes
> as transmit PIN replacements, but I've never seen an equivalent carrier
> lifetime spec that would give me comfort if a replacement is needed in my
> amps.  And, if these work reliably, I would like to know how close they are
> to the ragged-edge of acceptance.  And, are all 1N4007 diodes created the
> same and offer identical performance?  Even diodes from decades ago?
> >BUT if you use an IC7000 or similar, you'll have trouble. But I think
> Alpha compensates for crappy radios that still transmit RF AFTER the PTT
> line is released.
> To my knowledge, the Alpha 89 is the only ETO/Alpha amp that prevents a
> return from T=>R when RF is present.  Possibly the 9500 also protects this
> way but I've never tested it.
> A big deal at the moment is Icom's amp sequencing in the IC-7300, 9700,
> and 705 models.  The amp key line releases approx. 3 ms  BEFORE RF decays
> to zero.  This is a fault on amp break, not amp make.  As such, no amount
> of fiddling with a transceiver's menu helps to prevent hot-switching with
> fast amps.  The Elecraft amps DO have a menu selection to add delay on
> break.
> Icom has known about the problem since the 7300's release in 2016.  Myself
> and others have given up hope that they care enough to do something about
> it.  To that end, I created the new S-QSK Mini device that can be seen on
> my QRZ page.  It's a tiny 1X1 sequencer that's smaller than a book of
> matches.  Precise timing is set by an Adafruit Trinket MO microcontroller
> and it completely compensates for Icom's problem through software.  The
> S-QSK Mini is powered exclusively from a Micro B USB cable.  For those with
> an interest, here's a quick link to my QRZ page:
> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.w9ac.com%2F&data=04%7C01%7Cah7i%40gatech.edu%7Cf6d74293d2414fc85ce508d8e8780117%7C482198bbae7b4b258b7a6d7f32faa083%7C0%7C0%7C637514950381701423%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=MlgwpHpfR9UooZPrwaXLe1gP43%2FSO6%2FTT7N%2FvuCTO6M%3D&reserved=0
> Paul, W9AC
> ------------------------------

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