With this explanation I would agree. It does sound like something on the tower. I thought, It could, not likely, be in one of the 800 transmitters. I have seen this before, and it was very strange signal. Broadband, covered most of the 130-170 MHz range, and had little birdies every 15-30 KHz ranging from -110dBm to -90dBm.
Good Luck, and I would start looking at the tower... Charles Miller ----- Original Message ----- From: "Richard Sharp, KQ4KX" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, May 05, 2004 9:35 AM 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/
