Proper engineering also requires a Low Pass filter when installing an isolator, this will restrict any incoming frequencies above your operating frequency...although this is not the reason for the low pass filter...it is there to protect you from radiating any mixes at higher frequencies.
Gregg R. Lengling, W9DHI, Retired Administrator http://www.milwaukeehdtv.org K2/100 S#3075 KX1 S# 57 Politics is the art of appearing candid and completely open, while concealing as much as possible. -States: The Bene Gesserit View -----Original Message----- From: Richard Sharp, KQ4KX [mailto:[EMAIL PROTECTED] Sent: Wednesday, May 05, 2004 9:35 AM To: [email protected] Subject: RE: [Repeater-Builder] 2m repeater IMD issue Well, I considered that too. However, after further study of isolators (and discussing my situation with a manufacturer of isolators) I discovered that a VHF isolator will not stop signals in the 800MHz range from passing through it. An isolator should work great if I was dealing with several VHF transmitters at the same level on the tower. I'm wondering if the IMD is being generated somewhere on the tower, antenna(s), etc.? A bandpass cavity on the tx drops the 800MHz signal levels (as seen at the tx port) from -40dBm to -75dBm. I would think levels of -75dBm "shouldn't" be a problem for the 2m tx? The harmonic filter in the tx should drop the -75 to nearly nothing - right? That's why I'm thinking perhaps the IMD is being generated somewhere else. Although, it does only occur when the 2m tx is on. tnx Richard > -----Original Message----- > From: Charles Miller > > Richard, > > You said that the IMD is only there when YOUR TX in on. If this > is the case > you may need an Isolator for your TX. I had a site that was getting eat > alive with IMD at 150 MHz only when the TX was on. Found out that the IMD > was being generated in the transmitter. Put an isolator on the > thing and no > more IMD. > > Just a thought 8-) > > Charles Miller > > ----- Original Message ----- > > [snip] > > I can see carriers appear and disappear on the rx side when the > tx is on. > [snip] > > Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
