I have a 30 dB 250 W pad that I use with radios that put out over 50 Watts. My HP8921 will handle that without problem. It'd work with the 2.5W case. I don't remove it for sensitivity checks as I can compensate for it in the 8921. Most service monitors modern enough to have been designed for cell phones (those with >>10 W inputs) can do this. It's not always obvious how to do it, but they can. The IFR1900CSA I had could as well.
A relay is going to have to be awfully fast to do what you want to. At worst, use a 20 dB pad as a fuse and move the decimal point in your head when checking sensitivity. On 1/5/2010 4:30 PM, James wrote: > > > Hello to the group. Knowing most of you have service monitors for the > Repeater Builder Hobby, I wanted to pose the following question. What > method do you use to protect the input of your service monitor from > excessive RF Power input? I am referring to the input/output jack that > is limited to 2.5 watts on MANY service monitors. I know I can use an > attenuator, but that gets removed for sensitivity checks and may not > get put back on. One suggestion is a RF Relay that would trip on say > one watt and put the power to a dummy load. The problem is I have used > one of the cheap circuits in the past and toasted transistors in a > Pre-amp, before the relay reacted as the book said it should. However > I know there are circuits in say the Mirage Amp that also has a > Pre-Amp that is removed from the antenna during transmit, that works > well. What are you doing to protect your monitor? Appreciate your > thoughts. > > 73 JIM KA2AJH > > -- mailto:[email protected] Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
