My 2 cents worth. Many years ago I had a 200' run of LDF5-50 installed by a "professional" on a 900'tower (rptr at 700' antenna at 900') about a week later we noticed that the T&R performance dropped considerably. Personal inspection revealed that water or condensate (about a teaspoon full) had drained down the cable insde the hollow center conductor and had seeped around the inside of the bottom connector. The solution was to completely remove the connector and center pin, drain the cable and let it thoroughly dry then reinstall the connector. I never had another problem with it after that. I suggest you take a look at yours.
Years later I ordered 2 runs of LDF4-50 w/ connectors installed from DB and after receiving them checked them for continuitybefore installation. One cable showed a direct short between center conductor and ground. I removed both connectors and found one connector had been improperly installed at DB. Apparently the portion that has the spring fingers on it had been allowed to turn in the tightening process and it had grabbed the copper shield, shredded it and bent it inward to where it made contact with the center conductor. Needless to say ,but I then removed all the other connectors to verify their condition and reinstalled all of them properly. A third case similar to the one above (shredded shield ) but no physical contact (no continuity) showed a 1:1 SWR on Xmit but caused the RF to desense the rcvr. to the point where the perfomance of the rptr. was drastically reduced from what it should have been. Similar to what you are describing. While you might not see a direct short or even an indication of high reflected power when you test the system, if you have any contamination, moisture, or metallic debris in side the connector it can cause you the grief you are describing. Hope this helps some. -- Doug N3DAB/WPRX486/WPJL709 ---- Cort Buffington <[EMAIL PROTECTED]> wrote: ============= Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/ connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: > Cort, > > I need to understand if I have all the information correct from your > post. > > One 440 machine. One duplexer. Two antennas connected to two feedlines > which can either be terminated to the duplexer as you so desire? > Only one > feedline to one antenna, not coupled or combined in any way? One > hardline / > antenna works good (DB420) and one hardline / antenna (Telewave > ANT450F10) > works bad? > > The first step is to verify the Telewave wattmeter. I'd get a hold > of a > Bird 43 or equivalent and verify your readings. That's the easiest > thing to > do. > > If your forward / reverse numbers are accurate then I'd suspect the > Telewave > system or it's hardline, unless proven otherwise. You need to rule out > either the antenna or the hardline by substitution, and one at a time. > Possible issues could be bad connectors either at the antenna base or > duplexer termination. > > How long ago was the antenna system put up? Was there some heavy > rain in > the area that water could have been introduced into the connector / > hardline > if they weren't properly water-proofed? > > Unless someone contradicts me here, I'm having a hard time believing > that > the vertical alignment of the Telewave is critical. In re-reading > your post > over a couple of times I'm wondering when you checked the alignment > and then > implemented a little down-tilt you may have done something wrong to > cause > the hardline / antenna system to react that way. > > Keep us posted and good luck with finding out the problem. > > Don, KD9PT > > ----- Original Message ----- > From: "Cort Buffington" <[EMAIL PROTECTED]> > To: <Repeater-Builder@yahoogroups.com> > Sent: Thursday, October 16, 2008 8:16 PM > Subject: [Repeater-Builder] UHF Repeater Antenna Discussion > > > Folks, > > > > My repeater partner and I have recently placed our new 440 > machine. We > > have realized some odd issues. We bought a new Telewave ANT450F10 to > > put on top of the 100' tower, fed with a new piece of Andrew 5/8" > > heliax. We also side-mounted an old DB420 with the top a few feet > down > > from the top of the tower with about 85' of old 7/8" Andrew heliax. > > So, we put smokin' new gear on top, and smokin old below it. The > DB420 > > is spaced correctly from the tower and is set up with each half 90 > > degrees rotated. > > > > The tower is on relatively high pasture land (for NE Kansas anyway) > > with a nice clear view all around. I'll not say we're on a hill, but > > on relatively high ground. We are attempting to cover two towns > > approximately 25 miles apart. We are 1/3 of the way from town 1 to > > town 2 and about 3 miles N of the highway that pretty much is a > > straight shot connecting them. > > > > The Telewave setup on top performs poorly. The DB420 on the side is > > working great. By this difference, I mean signals that are getting > in > > full quieting on the DB420 are very noisy on the Telewave. Transmit > > differences mirror receive. S9 reception on the DB420, switch to the > > Telewave and it's S1-S3. We experience this phenomenon in all > > directions. > > > > Wattmeter (yes, it is a "real one" -- Telewave 44) says that things > > look good as far as loading both antennas -- DB420 is 1.43:1, F10 is > > 1.39:1. We are about to climb and take readings at the top to make > > sure there is no feed problem with the Telewave 'F10, and I admit > that > > has not been done yet. We did have a discussion with Telewave, who > > advised that vertical alignment of the F10 (as they refer to it) is > > critical. We have checked alignment and even implemented a little > down- > > tilt in the most important direction (just a few degrees). We see > not > > real appreciable difference. > > > > For you repeater elmers out there: If we don't find a problem with > the > > feedline on the Telewave antenna, does this make any sense? Telewave > > also HIGHLY recommended that the F10 isn't a good fit for this > > installation due to its extremely narrow vertical beamwidth, and > > recommended that a 4-bay dipole of theirs would be MUCH better > because > > of the ability to tune the pattern to our desired coverage area and > > the increased vertical beamwidth. I always thought I wanted NARROW > > vertical beamwidth to keep the RF on the horizon. I would have > thought > > that 100' up on relatively high ground (this is Kansas, after all) > > wouldn't have a real problem shooting over the top 10 - 30 miles > away. > > > > In any event I seek advice and wisdom, and yes, we are planning to > > check the coax for loss at the earliest convenience. I would like to > > take advantage of the top slot on the tower for improved performance > > rather than stay on the lower spot, and will try another antenna if > > necessary. I'm just having a hard time imagining that the F10 has > > appreciably narrower vertical beam as a 9.something dBd antenna than > > the F10 as a 10dBd antenna, etc. etc. And it also seems counter > > intuitive that a taller vertical beamwidth and less gain on the > > horizon in this application would be better. I trust the experience > > and knowledge of Telewave, but I also trust the wisdom from this > list, > > which has saved me many times. > > > > Your thoughts gentlemen? > > > > -- > > Cort Buffington > > H: +1-785-838-3034 > > M: +1-785-865-7206 > > > > > > > > > > > > ------------------------------------ > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
