Topband: Receiver protection using PIN Diode technology

[George Dubovsky]

If anyone is interested in playing with some HF-rated PINs, I have a
quantity of Microwave Associates MA-47266 available. They are 1.5 watt,
axial leaded parts (about the size of a 1/4 watt resistor), with a minority
carrier lifetime of 3.5 uS - rated for service down to 1 MHz. You can find
a datasheet on the Richardson Electronics website. Like Carl, I tried them
in the front end and filter switching positions of my IC-765 years ago, and
did measure a small TOI improvement (using lab grade equipment at work),
but the Icom already had a better front end than the Kenwoods.

73,

geo - n4ua

On Wed, Feb 1, 2012 at 11:51 AM, ZR <zr at jeremy.mv.com> wrote:

> See what the lastest rigs are using to switch front end bandpass filters.
>
> In the 80's my job involved using PIN's in RF modems as low as 5MHz.
> Considering their measured performance I modified my TS-940's using those
> MACOM devices and they worked well to below 160m and really stepped up the
> IP3 as I brought my rigs into work on weekends to run tests.
>  Last time I looked a few years ago they were no longer available;
> everything is SMD these days.
>
> Ulrich Rhode was a customer of my sideline Radiokit business and called
> often so we discussed this and he tried them in his TS-440 and then
> proceeded to prod Kenwood to make changes in their current rigs back then.
> Now everyone does it. He also discussed this in his articles in CommQuart
> and/or QEX.
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "Greg - ZL3IX" <zl3ix at inet.net.nz>
> To: <topband at contesting.com>
> Sent: Wednesday, February 01, 2012 11:24 AM
> Subject: Re: Topband: Receiver protection using PIN Diode technology
>
>
> > Hi Pete,
> >
> > The lower limit on the operation of a PIN diode, is not arbitrary, it's
> > set by the carrier lifetime of the diode.  The carrier lifetime has to
> > be longer than the half cycle time at the frequency of operation,
> > otherwise the diode stops acting like a PIN, and looks more like a
> > regular diode.  If that happens, you will thus lose the high IP3
> > characteristics.
> >
> > There are a few PIN diodes available with really long carrier lifetimes,
> > but they are not very common.  It may be easier for you to use a
> > different mechanism for Rx protection, such as reverse biased Schottky
> > diodes.  You need to set the reverse biasing as a compromise between
> > IP3, and providing adequate protection for the Rx.
> >
> > 73, Greg, ZL3IX
> >
> > On 2012-02-02 02:16 a.m., Pete Smith N4ZR wrote:
> >> Quite by accident, in leafing through K9AY's new magazine I ran into a
> >> reference to a surface-mount PIN diode
> >> <http://www.skyworksinc.com/Product.aspx?ProductID=857>  designed
> >> specifically for receiver protection.  It begins to block signals at +10
> >> dBM, and works by quite a different mechanism than conventional diode
> >> limiters, resulting in pretty high IP3. The specified lower frequency
> >> limit is 10 MHz, but I wonder if that is arbitrary
> >>
> >> Has anyone tried this approach to receiver protection on Topband?
> >>
> > _______________________________________________
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