Steve, Jeff, Nate, Ya'll are on the right track. I did some additional tests. It not the 147.765 subscriber it's the 147.93 subscriber that is throwing the stinky stuff into the fan. Keying the 33 repeater does not cause the 165 repeater to come up. However, when both repeaters are on the air 33 will keep 165 keyed & the 33 audio can be heard on the 165 repeater. As soon as the 33 subscriber unkeys the interfering signal on 165 goes away.
I a ham not infected with ctcss phobia, therefore 33 (which I built) has RX & TX tone. This lets me TX on 33's input & not key the repeater. The 165 repeater is not interfered with. Also lowering the power of the 147.930 TX clears the problem. 174.33, 147.93 & 147.165 have to be on the air to cause the problem in the 147.765 RX. I assume it is in the 147.765 RX, I don't have access to look at RX audio on the 147.165 repeater. Is it valid to add 600 kHz to the intermod calculator? I get an interesting fifth order when I do. 147.9300 MHz - 147.3300 MHz - 147.1650 MHz - 0.6000 MHz - 0.6000 MHz = 147.7650 MHz Right on the 147.165 input. As I said before, the owner may have added a preamp to 147.165 a day or two ago. This problem just came to light last night. These two repeaters have been on the air for years. I was wrong about the spacing, they are 4 miles apart. The 33 repeater equipment was getting tired & I replaced it with a Mastr II station repeater two weeks ago. I can't say for sure if the problem started with new 33 equipment or the preamp on 165. It looks to me like the cure is to notch 147.930 at the 147.756 receiver. Anyone have any thoughts. Fred N4GER -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Nate Duehr Sent: Saturday, February 03, 2007 1:35 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Intermod On 2/3/07, Jeff DePolo <[EMAIL PROTECTED]> wrote: > > I think I see how Steve's logic is leaning, and I agree - I don't see any > logical mix here until you include a user's transmission on one of the > repeater's inputs. Fred - do you hear ALL 147.33 transmitter activity > coming in on the 147.765 input, or just when there is actually a user keyed > up on 147.93? If the latter, that's a big clue... > > --- Jeff Yep, that's going to be the key... been there done that... Ye olde 600 KHz split on VHF problem. It creates perfect mixes with users and the repeaters themselves that fall right smack on the input of the next repeater along the band. A close-in high-powered user to a VHF repeater can mix with it with bad results for the next in line machine. Requiring CTCSS on a different tone than the original machine and users will cover up the problem, but not fix it, of course... not a permanent fix, but sometimes necessary. If Jeff's observation is correct, and you only hear input activity... try to find a ham who's rig causes the issue consistently (and you'll probably find that HT users don't, also -- they're usually just too weak to create a strong-enough mix). Then you can have that person lower their power and see if the problem signal on the repeater's input seems to drop out quickly or get much weaker, since you're looking for a mix that would drop off rapidly as one of the transmitter's power levels was lowered. If that's not it... have a 600 KHz AM station in your town? There's always the possibility of other mixes as well... Jeff's test is the kicker to start with -- do you hear the full TX tail of the other repeater or just user input? Does it do it on ALL transmissions or just certain users? Anyone involved in the situation live real close to either repeater, who you know has high gain antennas and runs lots of power? Nate WY0X Yahoo! Groups Links
