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 <[email protected]> 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" <[email protected]> > To: <[email protected]> > 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? > >> > > _______________________________________________ > > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > > > > ----- > > No virus found in this message. > > Checked by AVG - www.avg.com > > Version: 10.0.1416 / Virus Database: 2109/4779 - Release Date: 02/01/12 > > > > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
