[Repeater-Builder] Re: Exec II input problem
Hi Jim, I am using a Wavetek 3001. I also have a MVP here with the same helical filter and it doesn't exhibit this. Hence fairly convinced that something is going on with the Exec's filter. It seems like the signal is getting better because were loosing the loss of the filter stage. Update now is that I have resoldered the base of the first coil and ant connections and it has got a lot better. I don't see the change near as much, but moving the cable around still does impact the signal.. The RX freq is 448.625 and sensitivity seems to be .72uV for 20db of quieting versus spec of .5uV. So still fighting it. Randy --- In Repeater-Builder@yahoogroups.com, Jim Brown w5...@... wrote: What are you using for a signal generator? Some generators leak a lot of signal and might have more than .35 uV of signal radiated on the outside of the coax. When you break the shield path, this higher signal level might get to the radio. Another post mentioned that the RCA connector uses a short pin. I use a BNC to RCA connector with the center pin cut back to match the radio internal connectors to avoid problems in this area. 734 - Jim W5ZIT --- On Thu, 5/28/09, wb8art wb8...@... wrote: From: wb8art wb8...@... Subject: [Repeater-Builder] Exec II input problem To: Repeater-Builder@yahoogroups.com Date: Thursday, May 28, 2009, 4:02 PM Wonder if anyone has had this problem and know what the problem is. I am working on a GE Exec II repeater (converted mobile) which has no Comb no. I any case the issue is that if I move around the cable feeding it with a generator I was seeing a change in the recieve. I went directly to the RCA jack, and then found that just making connection with the center pin, I have about 10 to 20db stronger recieved signal than when I push it all the way in making the ground connection. This is a mobile and the RF deck is no. is 19D417075G14 rev A covered by LBI30032E. This shows a option of either non floating ground or floating ground input. This one is a non floating ground one. Might have been changed but I have know knowledge of its history. The RCA jack center pin connects directly with a wire thru a hole to the first helical and I have looked and can see no connection issues and measures a short with an ohm meter. I even reheated the solder joints and no change. Anythoughts would be appreciated. Randy
Re: [Repeater-Builder] Re: Exec II input problem
Did you check the front end for tin whiskers like someone else posted? They can easily destroy sensitivity. Chuck WB2EDV - Original Message - From: wb8art wb8...@netzero.net To: Repeater-Builder@yahoogroups.com Sent: Saturday, May 30, 2009 9:28 AM Subject: [Repeater-Builder] Re: Exec II input problem Hi Jim, I am using a Wavetek 3001. I also have a MVP here with the same helical filter and it doesn't exhibit this. Hence fairly convinced that something is going on with the Exec's filter. It seems like the signal is getting better because were loosing the loss of the filter stage. Update now is that I have resoldered the base of the first coil and ant connections and it has got a lot better. I don't see the change near as much, but moving the cable around still does impact the signal.. The RX freq is 448.625 and sensitivity seems to be .72uV for 20db of quieting versus spec of .5uV. So still fighting it. Randy
[Repeater-Builder] Re: Exec II input problem
Yes I have and I know they can be hard to see. But don't think thats it but will be tearing it a apart again and clean and resolder as that did seem to make progress with the issue. At first with the problem I could get the sensistivity up to .35 better than spec with pulling out the RCA jack to only the center pin connected now that doesn't help much so why I think it was bypassing the loss of the filter stage and the fact that possible resoldering the coil base improved the issue concurs with my thought. Randy --- In Repeater-Builder@yahoogroups.com, Chuck Kelsey wb2...@... wrote: Did you check the front end for tin whiskers like someone else posted? They can easily destroy sensitivity. Chuck WB2EDV - Original Message - From: wb8art wb8...@... To: Repeater-Builder@yahoogroups.com Sent: Saturday, May 30, 2009 9:28 AM Subject: [Repeater-Builder] Re: Exec II input problem Hi Jim, I am using a Wavetek 3001. I also have a MVP here with the same helical filter and it doesn't exhibit this. Hence fairly convinced that something is going on with the Exec's filter. It seems like the signal is getting better because were loosing the loss of the filter stage. Update now is that I have resoldered the base of the first coil and ant connections and it has got a lot better. I don't see the change near as much, but moving the cable around still does impact the signal.. The RX freq is 448.625 and sensitivity seems to be .72uV for 20db of quieting versus spec of .5uV. So still fighting it. Randy
Re: [Repeater-Builder] Re: Exec II input problem
Sometimes the conductivity of the tuning screws to the casting becomes questionable. There is a conductive grease that a lot of GE shops used to eliminate that issue. Chuck - Original Message - From: wb8art wb8...@netzero.net To: Repeater-Builder@yahoogroups.com Sent: Saturday, May 30, 2009 11:06 AM Subject: [Repeater-Builder] Re: Exec II input problem Yes I have and I know they can be hard to see. But don't think thats it but will be tearing it a apart again and clean and resolder as that did seem to make progress with the issue. At first with the problem I could get the sensistivity up to .35 better than spec with pulling out the RCA jack to only the center pin connected now that doesn't help much so why I think it was bypassing the loss of the filter stage and the fact that possible resoldering the coil base improved the issue concurs with my thought. Randy
Re: [Repeater-Builder] Re: Exec II input problem [1 Attachment]
At 5/30/2009 08:06, you wrote: Yes I have and I know they can be hard to see. But don't think thats it but will be tearing it a apart again and clean and resolder as that did seem to make progress with the issue. At first with the problem I could get the sensistivity up to .35 better than spec with pulling out the RCA jack to only the center pin connected now that doesn't help much so why I think it was bypassing the loss of the filter stage and the fact that possible resoldering the coil base improved the issue concurs with my thought. Randy For those who've never actually seen tin whiskers, I took a pic of the helical resonator cover plate of the last MVP I had to service for this problem. Bob NO6B
Re: [Repeater-Builder] Re: Exec II input problem
There is another good photo of MastrII whiskers at: http://www.repeater-builder.com/ge/mastrIIcasting.html 73, Joe, K1ike n...@no6b.com wrote: For those who've never actually seen tin whiskers, I took a pic of the helical resonator cover plate of the last MVP I had to service for this problem. Bob NO6B
