Hi Guys, Just wanted to add a few facts to this disscussion. I have had 165 up for 16 years. Never had a problem with a .93 transmitter getting in until now. As far as I can tell it's happened once and only once. Hank had been talking to a distant station and still had his power up when it happened. No one else is getting in and that was the only time he was heard.
A few things about 165. First I run about 90 watts from a Micor. No desense to speak of. Never said there was either...don't know where that came from. Running a MasterII receiver with the hot front end. Have been for years and no external preamp has been added...don't have one and nothing has changed here. I do run a small filter in the RX line but run split antennas. Receive is at 330' fed by 7/8 hard line...transmitter is 110' fed with 1/2 inch hardline. The GE RX is very tight and does a great job. I live within a few hundred feet of 165. I've tried to duplicate the problem here with 45 watts into a gain antenna. My transmitter doesn't bring up 165 when transmitting on .93. Not even a peep. Anyway after this many years and just one instance like this at this point it really isn't a problem...if it becomes one then we can talk about making mods. Until then lets just enjoy what we have and have fun with ham radio! Ben > > > > 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@ <mailto:Repeater-Builder%40yahoogroups.com> > yahoogroups.com > [mailto:Repeater-Builder@ <mailto:Repeater-Builder%40yahoogroups.com> > yahoogroups.com] On Behalf Of Nate Duehr > Sent: Saturday, February 03, 2007 1:35 PM > To: Repeater-Builder@ <mailto:Repeater-Builder%40yahoogroups.com> > yahoogroups.com > Subject: Re: [Repeater-Builder] Intermod > > On 2/3/07, Jeff DePolo <[EMAIL PROTECTED] <mailto:jeff%40depolo.net> net> 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 >
