Gary, A good reminder for me as I plan to walk my beverages today checking for problems. I'll take along my F connector wrench and make sure all are tight.
73, On Mon, Nov 18, 2013 at 2:00 AM, Gary Smith <[email protected]> wrote: > Gentleman, and I say that honestly... :) > > I have a resolution to the issue and along with it my thanks for > those who offered really solid ideas to track down. & more to the > opportunity to learn, I have much apparently to learn about my 259B > which is more than just a pretty face. > > However, the cause of the majority of my problems were the F > connectors being somewhat loose in the RX array. They were all > connected to the coax properly, it was the connections to the many > different chassis' involved; It's beyond me how so many of them were > not tight and I have more than my share of OCD and leaving so many > loose makes me wonder if I did close them tightly in the early winter > last year but not tightly enough and perhaps with cooling/heating > they loosened some more. > > Yeah, that seems like a stretch but whatever it is, there has to be a > reason they were all loose when I always crank down on outdoor > connectors to keep water out. That looseness was the cause of most of > my issues. I wonder if a diode/rectifier effect might have taken > place and was creating a signal due to the proximity of Amtrak with > it's catenary suspended 15KV power supply. I'm not enough of an > engineer to figure that one out but regardless, tightening solidly > all the F connectors and cleaning the grounds to each antenna in the > array made all the difference. > > Thanks again to everyone who offered helpful suggestions, it's all a > learning experience to pass on to the next guy. Or hopefully YL. > > 73, > > Gary > KA1J > > > I just downloaded the manual on PDF and read the "advanced" > > section > > > dealing with distance to fault. Sorry to say I must not be as > > sharp > > > as I used to be and I can't tell from what I've read if the RG6U > > > needs a termination for this distance to fault test or if the coax > > is > > > unterminated. Since it's the weekend I can't call MFJ but > > perhaps > > > someone knows this answer & can let me know so I can have at it > > > tomorrow. > > > > They probably would not know the answer to that. > > > > The distance-to-fault algorythm uses the repeating of minimum > > reactance at > > minimum impedance as frequency is changed to calculate distance to > > fault. > > The further the distance to the lump, the closer-spaced the ripples > > become. > > If you pick the closest-spaced dips you will get the most distant > > "bump". If > > you misterminate the cable, obviously you would see that > > mistermination > > distance as a fault distance. It is best to terminate the far end > > with a > > 75-ohm resistor. (I always keep 75-ohm F terminators and a few > > barrel > > connectors in my "field bag" for testing cables.) > > > > This would also be true if you used a rig or anything else and > > looked at > > SWR. You would really have to terminate the far end in 75-ohms, or > > whatever > > the cable is, to not "fool yourself". Otherwise, as you moved along > > the > > cable or as you changed frequency, you could see "lumps" where there > > really > > are no "lumps". > > > > You don't want to check a system that is misterminated at the far > > end from > > the cable's surge impedance, unless you really have a good grasp on > > how > > these things work or you are using a TDR. I can work around it, but > > it is a > > lot more painful for me than just using a correct termination. :-) > > > > > > > Apparently I'll need to find the velocity factor of this > > particular > > > RG6U and then can do the math they describe. I just need to know > > if I > > > test this on an open coax or with a 75 ohm carbon resistor at > > the > > > distal end of this 75 ohm coax (or 50 ohm on RG-8). And, does it > > > matter if I use either of the SO239 or the BNC ? > > > > The MFJ269 allows you to enter velocity factor, but it is simple to > > hand > > calculate it with the 259. If you are off 10% in the Vf, it isn't a > > big > > problem on shorter cable runs. Use the resistor. The BNC is only for > > the > > frequency counter mode. > > > > You said you have birdies. What is the nature of the birdies? Are > > they > > signals that mix, like BC stations beating together, or is it wide > > buzzy > > junk from power supplies and stuff??? You might not have a bad > > connection. > > It might be in the antenna system or receiving electronics > > hardware. > > > > 73 Tom > > > > > > > > > --- > This email is free from viruses and malware because avast! Antivirus > protection is active. > http://www.avast.com > > _________________ > Topband Reflector > -- Ken - K4XL BoatAnchor Manual Archive BAMA - http://bama.edebris.com "Show me a politician who is poor, and I'll show you a poor politician." - Carlos Hank González _________________ Topband Reflector
