Re: [Repeater-Builder] Decibel dipole array sweeps
n...@no6b.com wrote: At 3/22/2009 11:32, you wrote: The document can be found here: http://www.broadsci.com/Antenna Sweeps r1.pdf I get a The file is damaged could not be repaired error. And I get a 404 Page not found error. Paul
Re: [Repeater-Builder] Re: LMR-400 and Belden 9914 DuoBond
Thanks Mark and Mike! The great news is there is a tremendous amount of good information at the repeater-builder site. The less-great news is I'm an idiot and can't always find what I'm looking for. ;-) I appreciate the help finding this stuff. Paul N1BUG Mike Morris WA6ILQ wrote: The word wrap broke his link. Try this: http://www.repeater-builder.com/antenna/recommended-coax-and-connectors-for-iden.pdf http://www.repeater-builder.com/antenna/andrew-braid-over-foil-imd.pdf http://www.repeater-builder.com/rbtip/double-shielded-coax.html The arrows (upper case comma and period) on either side of a link prevents the broken links if the program that you are using to read your mail follows the rules contained in RFC1738 (the spec that defines what is and is not a URL). Mike WA6ILQ At 08:49 PM 03/20/09, you wrote: Paul, The one you are looking for is: http://www.repeater-builder.com/antenna/recommended-coax-and-connectors-for- iden.pdf Others for reference are: http://www.repeater-builder.com/antenna/andrew-braid-over-foil-imd.pdf http://www.repeater-builder.com/rbtip/double-shielded-coax.html 73, Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Paul N1BUG Joe wrote: There is a Motorola letter that warns about the problems of braid-over-foil coax. You can find it on the repeater Builders site. I just tried looking and searching for it on the Repeater Builder site and came up empty. If it's there could someone point me to it please? I would VERY much like to see it before Monday, for reasons I won't go into right now... I did find something on the subject by Andrew but since they make Heliax that likely won't help my case. Paul N1BUG Yahoo! Groups Links Yahoo! Groups Links
Re: [Repeater-Builder] Re: LMR-400 and Belden 9914 DuoBond
Joe wrote: There is a Motorola letter that warns about the problems of braid-over-foil coax. You can find it on the repeater Builders site. I just tried looking and searching for it on the Repeater Builder site and came up empty. If it's there could someone point me to it please? I would VERY much like to see it before Monday, for reasons I won't go into right now... I did find something on the subject by Andrew but since they make Heliax that likely won't help my case. Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:repeater-builder-dig...@yahoogroups.com mailto:repeater-builder-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: repeater-builder-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Re: Quieting duplex noise from a tower
Aircraft handhelds are AM in the 120MHz region. Some handheld scanners do aircraft AM just fine. Ah! Somehow that hadn't occurred to me. The president of our club is a pilot and has one. I guess there are no weak, constant signals in the aircraft band (?) but maybe it's not necessary. I will try climbing the tower with it and see if it does anything when I move or vibrate guy wires and other hardware with the repeater transmitter on of course. It's possible the aircraft handheld will just be desensed by 2 meter RF and unable to hear the noise (?) but it will be interesting to see what happens. Paul N1BUG
Re: [Repeater-Builder] Re: Quieting duplex noise from a tower
Yeah, I was going to suggest a simplified version of what you're talking about - climb the tower with a little AM transistor radio tuned to a weak station, key the transmitter on and off, and see if you can find a noise hot spot or anything that when moved or vibrated causes the noise level to increase. However, I haven't tried this using VHF excitation, but I've used the same technique to find all kinds of other broadband noise sources. The local power company uses an AM receiver operating in the VHF range (I think I was told it was around 110 MHz) to locate bad/arcing insulators, fuses, etc. on primary lines. Thanks Jeff. I will try that, and also inducing vibration in the tower structure(s) by wrapping it with something as soon as I can. Maybe I will get lucky and find something. If I don't find any specific problem areas, I'm leaning strongly toward trying Phillystran guys when I can come up with the $$$ to do it. I appreciate the input from everyone on this problem. Paul N1BUG
[Repeater-Builder] Quieting duplex noise from a tower
OK guys... I thought I could figure this out on my own, but I was wrong. I could use some wisdom from the group! I have been chasing a stubborn case of duplex noise for a long time without success. The 2 meter repeater will run clean all day at 100 watts (or any lower power level) into a quality RF load placed on the antenna port of the duplexer. It will run clean all day with the same load placed at the antenna end of the feedline. With the antenna connected it will SOMETIMES run clean. At other times we get the crackling and popping of duplex noise. And at times we get increased noise floor (I can see it on the receiver limiter current but it has no specific sound, it's just like the normal receiver noise floor came up 20 to 30 dB!) None of this happens when it is run into the RF load. It is only when running into the antenna, and then only sometimes. The steady high noise floor, when present, happens only when my transmitter is up. It happens even if no other transmitters on the hill are up. It will occasionally go for days or even weeks without a glitch, then be essentially unusable for hours or days. The crackling does seem to be worse in windy weather. The steady noise does not seem to be better or worse in any kind of weather, but occurs completely at random as far as I can tell. Three different antennas (all DB or Sinclair, two of them NEW) have been tried with no significant change. The feedline (Andrew LDF5-50A) has been swapped out once with no change. I think that leaves the tower or other nearby metal structures as the prime suspects. The tower is 100 feet of Rohn 25G guyed with 3/16 EHS. I have tried more than once to bond the sections of tower with straps across the leg joints, and similarly where guys attach to the tower and/or turnbuckles etc. at ground level. These efforts did not help and seemed to actually make matters worse. By the way, the guy ends use Big Grips, not clamps. Was that a mistake for a repeater tower? I am looking for advice. If anyone has solved noise problems in a similar tower, I would very much like to know specifically what materials you used and how you installed them that worked for you! I do have another newly erected 100 foot tower close by. It could be part of the problem. However, I was having this problem long before that tower went up so I'm still pointing fingers at my own stuff. A 440 repeater on the same tower does not have any problems. Neither repeater seems to be affected by the other's transmitter. It is only the 2 meter repeater killing itself. Both my tower structure and the new adjacent tower structure are hot with RF from my 2 meter transmitter, as evidenced by horrible noise when something like a screwdriver shaft is lightly rubbed against the towers or guys. I do not find any other metal structures in the vicinity that react that way. There is NO loose hardware in my system. I've been over it time and time again. There is NO visible rust anywhere. Any suggestions before I pull the rest of my rapidly thinning hair out? Here's one for ya... this problem first reared it ugly head right after I put up the tower. For years prior to that I had run the antenna on a rusty metal mast with loose fitting joints without ever a hint of trouble!!! Paul N1BUG 147.105 and 444.950
Re: [Repeater-Builder] Quieting duplex noise from a tower
Thanks Chuck. What would you consider nearby? There is one fiberglass antenna on a tower 60 feet away. It was new when it went up 2 years ago, but my problem existed before that tower/antenna went up. Aside from that the nearest other fiberglass antenna (or antenna of any kind) is 250 feet away. Paul Chuck Kelsey wrote: Suspect any other nearby fiberglass antenna in your search. Chuck WB2EDV
Re: [Repeater-Builder] Quieting duplex noise from a tower
Great questions, Jeff. Thanks! Answers below... Have you looked at the transmitter output with a spectrum analyzer during the occasions when you have desense to see if it's getting sloppy? No. I wanted to but I'm very isolated up here and do not have access to one. Have you tried other transmitters and/or amplifiers? Several PAs have been tried. Solid state and tube, GE and Motorola. No change with any of them. There is very little change in desense when I vary the power level unless I drop the power very low, like less than a watt. Then it goes away like somebody threw a switch. The exciter has not been swapped out for a different type. However I have tried 4 of the same type exciter (PLL variety Mastr II), no change. Another thing I tried was essentially a homebrew Z match between the PA and duplexer, no change. Do you have Polyphasers or anything other than coax between the duplexer and the antenna? I know I should have them, but I don't. Have you tested with the transmitter off? Yes, many, many times. It never happens with the transmitter off. I'm very confident about that. Are you using a preamp? If so, what do you have ahead of it for filtering, and/or have you tested without the preamp? Yes I use a preamp. DB4062 duplexer and two DB4002B 11 pass cavities, pass cavity loops set for 1 dB insertion loss each cavity. I tried tightening it up to 3 dB per cavity, no help there. The problem is still there without the preamp. Have you tried an antenna installed at a different height on the tower than the current antenna to see if anything changes? Yes, and it does change but does not go away. If I take the antenna off the tower and put it 20 to 30 feet away from the tower, the problem is drastically reduced but not completely gone. I can't quantify changes with absolute numbers... only generalizations... since the problem is intermittent and varies greatly even when I'm not changing anything. Do you have ground kits on the feedline going up the tower, and if so, are they properly attached/bonded, particularly avoiding any dissimilar metal contact? Another thing I should have but don't. Big Grips (usucally called preforms) are generally OK, many a tower much bigger than a 25G uses them. They need to be properly protected to avoid coming un-twisted due to ice sliding down the guy wire. Pull-out strength, if installed properly, is as good as conventional mechanical clamps. Preforms, right. I was wondering about the integrity of RF contact between the preform and the EHS wire since the preforms are coated with whatever that stuff is on the inside. To help determine if you have a mechanical problem that is being manifested as noise when excited by the high RF field of the transmitter, try rapping on the tower at the base and at the guy anchors with something (like a crescent wrench). The goal isn't to shake the tower, but instead to induce a significant mechanical vibration. See if the noise increases (either audibily or visibly on the spectrum analyzer) with the vibration, and dampens out as the vibration decays. I missed that test! I have tried shaking the tower, which seems to have no consistent affect. I will try inducing vibration by rapping it with a wrench. What else is nearby? Buildings, utility lines, etc.? A couple small wood buildings, including my own. Mine was the only one there when this problem started. I have been over my internal wiring and every piece of metal under my control, no suspected items found. There is a 13.2 kV rural distribution power line and phone line running past the site about 70 feet from my tower, plus power drops to my building and another nearby. My antenna was closer to the utility lines when it was on the mast and was not having problems. If the antenna was top-mounted on the rusty mast, but is now side-mounted on the new tower, that could explain a lot of the difference. The top-mounted antenna will couple much less energy to the supporting structure than would a side-mounted antenna. Good point. I have tried top and side mounting on the tower. Top mounting helps, but not nearly enough. Paul
Re: [Repeater-Builder] Quieting duplex noise from a tower
Have you tried putting one or more pass cavities on the transmitter? It's more of a longshot, but if there's something strong coming back down your feedline it could be getting to your PA resulting in intermod. The problem would come and go with the strong signal obviously, and only when your Tx was keyed. I have tried putting one of the 11 pass cavities on the transmitter. No change. There is a fairly low traffic APRS digipeater (144.39) on a tower 250 feet away but my noise problem does not come in packet-length bursts. It was also down for a while and I still had the problem. The only other VHF transmitter is 158.x on the tower that is only 60 feet away. However I have never yet found that transmitter to be up when my problem was occurring. It sees VERY little use. The only other sources of RF are cell towers several hundred feet away. Yeah, they're coated with that semi-clear plasticy stuff usually. I wouldn't consider that to be a high risk factor, but hard to say. How close is the nearest guy wire attachment point on the tower to your antenna? Close, just a couple feet below the antenna at the present time. In general, moving the antenna closer to a set of guys does seem to make the problem worse. If I could somehow get to a point where I believe it's the guys, I would seriously consider replacing them with Phillystran, leaving a few feet of EHS at the anchor end. Is your antenna currently side-mounted or top-mounted? If side-mounted, at what height? Half and half at the moment, actually... the 20 foot stick is mounted on side arms at the 90 foot level of a 100 foot tower. Moving it to top mount does seem to decrease the desense by some 5 to 10 dB (hard to quantify due to variability) but I still have 20 to 30+ dB desense at times. When side mounted, spacing from the tower also makes some difference (wider spacing = less desense) but again not enough to be truly helpful. What kind of mounting brackets/clamps for the antenna? Sinclair heavy galvanized mounting clamps on the antenna, side support arms are heavy galvanized angle stock. Galvanized U bolts to tower legs. Other mounting arrangements have been tried, including the use of insulating material for side arms. Some change (less desense with the insulated mount) but still not enough to be really helpful. What else is on the tower? The only things on the tower are my 147.105 and 444.950 antennas. I tried completely removing the 440 antenna and feedline from the tower, but nothing changed. How are the feedlines attached to the tower? They are both LDF5-50A up the inside of the tower (that was fun), attached by many heavy duty nylon cable ties. Does the noise get any better or worse when it's raining out? There *seems* to be some tendency toward the noise being worse during the first hour or so of a rain or snow event. But it is not always so. The noise is sometimes there when it is raining, but not always. It sometimes there when it is dry, but not always. How are the guy wires attached to the tower (looped around a leg, with or without thimbles, torque triangle/arms, etc.)? The preforms are looped around a leg and through the Z braces of the tower. No thimbles at that end, there are some where the guys attach to the turnbuckles. I'm guessing not, but is the tower lit? It is not. When you changed out antennas and heliax, I presume you replaced any topside jumpers as well? Topside jumper and the jumper between duplexer and feedline were replaced. Where is your equipment with respect to the tower (i.e. how close to the base)? About 30 feet away. And how well-shielded is the equipment (enclosed metal cabinet hopefully), and are you taking the usual precautions as far as cabling into, and within, the cabinet to keep RF out? Hmm. The cabinet (rack) is not completely enclosed. Each piece of equipment is in a shielded enclosure. There are feedthrough capacitors and chokes/beads on every non-RF lead entry point to a piece of equipment. However, the 13.6V interconnecting cables and 117VAC power cords are not shielded. They do have the filtering wherever they enter equipment. Paul
Re: [Repeater-Builder] Re: Quieting duplex noise from a tower
Hi Randy, I remember working you on 2 meters. That is very interesting. I tried bonding all the joints. If anything it actually seemed to make things worse!? I have been seriously thinking about Phillystran. It's a big expense not knowing for sure where the problem lies, but the only way to find out may be to try it and see! Paul wb8art wrote: Hello Paul, Worked you a few times many moons ago. I would agree with Jeff with tapping and slightly causing movement with the repeater up with a weak signal. I have before experiened both an antenna (stationmaster) with internal broken joint which caused severe noise and desense but also dependent on movement in the structure. Also have seen with a 100ft. guyed 3/36 town like yours having the same issue. I tried grounding bonding all joints on guys to tower and between tower sections to no avail. Also tried isolating the preforms from tower and bottom supports with no change. I decided that the 3/16 stranded was the generation source. We changed the guys to Phillystran and never had another issue.
Re: [Repeater-Builder] Quieting duplex noise from a tower
Also, I'll ask the dreaded question... You are not using any foil/braid coax (LMR-400, 9913, etc.) for any jumpers are you? Nope, won't allow the stuff near my repeaters! grin LDF5-50A runs up the tower, RG-214 mil spec double silver shield for all jumpers. Paul
Re: [Repeater-Builder] Quieting duplex noise from a tower
What type of power supply is in your system? Do you have a back up battery? If so what type of charger is on it? Any other repeater systems in close proximity? There is a backup battery which is float charged from the 13.8V DC power supply. Presently the supply on duty is a homebrew beast of a linear supply (no switchers). I have tried Astron supplies in place of that, no changes noted. There is one public safety repeater, transmit 158.x on a tower 60 feet away. It was not there when my problem started, nor have I ever found their repeater to be in use when my problem is occurring. Actually I'm hard pressed to find that repeater in use, period. Paul
Re: [Repeater-Builder] OT DTV
Yup. Woefully inaccurate (too optimistic) for my location too, but after zooming all the way in I am impressed with their terrain data. :-) Chuck Kelsey wrote: I just checked this against my location and the results were woefully inaccurate. Chuck WB2EDV http://www.fcc.gov/mb/engineering/maps/
Re: [Repeater-Builder] 900 MHz WISP on repeater tower?
Kevin Custer wrote: Ethernet cabling should be of the shielded type and bonded at one end to earth. If they are putting up a 900 MHz access point, will it be sectorized? If yes, how many sectors (how many transmitters)? What frequencies and bandwidths on 900 (20 MHz) (10 MHz) (5 MHz) ? How is the input bandwidth being delivered? Fiber, DSL, wireless link on another band (2.4 GHz) (5.3 GHz) (5.8 GHz)? What kind of antenna system... 3 - 120 degree sectors, 1 - omni? What kind of equipment (Alveron) (Motorola) (home-made) (don't laugh, I build my own) Answering the above will give me an idea of what you can expect. Thanks Kevin, that gives me some questions to ask them! I do know the input bandwidth would be via 5.8 GHz wireless link and they would be using Motorola Canopy equipment. I will ask about the rest... I failed to mention I have reason to expect they will be putting equipment in the immediate vicinity of my repeaters one way or another... either on my tower or on an adjacent tower. Paul
[Repeater-Builder] Re: 900 MHz WISP on repeater tower?
Thanks to everyone for the input on this. It's appreciated. Now I have a better idea what I should be asking them. As I noted in a response to Kevin, they're probably going to end up either on my tower (where I might have some control) or on a tower 50 feet away (where I have zero control). Paul N1BUG
[Repeater-Builder] 900 MHz WISP on repeater tower?
I could use a little help here. I have a repeater tower with 2 meter and 440 repeater on it. I have been contacted by a wireless internet service provider about putting some 900 MHz stuff on my tower. The deal they are offering is attractive but I'm wondering if there would be interference issues between their stuff and my repeaters. I'm going to be setting up a meeting to discuss technical aspects of the proposed system, but I have no experience or knowledge in this area and am not sure what questions I should be asking them. Any suggestions or advice? Thanks! Paul N1BUG
Re: [Repeater-Builder] DTV ch 2 vs 6m
Thanks everyone for the comments on this topic. I will report back later and let you all know how DTV 02 and 6m get along. Paul N1BUG
Re: [Repeater-Builder] OT: digital TV channels
Buddy Case wrote: It is my understanding there will not be any channels between 2 thru 6 anymore. The govt proposes to auction these frequencies. Checking the list on www.nab.org http://www.nab.org shows no stations below ch 7. Buddy KS4QA I only wish it were so. If you are referring to: http://www.nab.org/AM/ASPCode/DTVStations/DTVStations.asp you need to look more closely. It shows at least one station currently broadcasting DTV on each of the VHF low 2 thru 6 channels. After transition, some stations currently broadcasting digital on temporary UHF or VHF high assignments will move to the VHF low channels. That is what is happening in my area. WLBZ, now broadcasting analog on ch 2 and digital on ch 25, will switch its digital transmission to ch 2 after transition. It is my understanding the original plan was to completely free up ch 2-6, but the FCC changed its mind and will allow some stations to remain on those channels. Paul
Re: [Repeater-Builder] DTV ch 2 vs 6m
That's what I'm afraid of. It's already nearly impossible to do anything on 6m around here without problems with ch 2 analog. Once they go digital on ch 2 I'm expecting even more issues. But I guess time will tell... Paul MCH wrote: If it's like any other digital transmitters, more. Joe M. Paul N1BUG wrote: I think this is on topic for the list since it could affect some 6 meter repeater owners. After transition I will have a local channel broadcasting DTV on their low VHF channel 2 assignment. I'm curious... does anyone know whether DTV will be more (or less) susceptible to interference from ham radio transmissions than analog TV? Thanks 73, Paul N1BUG Yahoo! Groups Links Yahoo! Groups Links
[Repeater-Builder] DTV ch 2 vs 6m
I think this is on topic for the list since it could affect some 6 meter repeater owners. After transition I will have a local channel broadcasting DTV on their low VHF channel 2 assignment. I'm curious... does anyone know whether DTV will be more (or less) susceptible to interference from ham radio transmissions than analog TV? Thanks 73, Paul N1BUG
Re: [Repeater-Builder] OT- Digital TV converter box issues
I TRY not to respond to OT posts, but boy am I fed up with DTV! I could get all the high power analog stations in my market snow-free with a small rooftop antenna. No go with DTV so I've been incrementally upgrading. I now have a very large antenna residing at 70 feet on one of my towers. Now I can get SOME of the digital signals. I'm going to try a mast mounted amplifier as soon as I'm able to climb again (currently recovering from surgery). I've already tried several TVs with ATSC tuners and converter boxes. There is some variation, but none of them can get all the digital signals that theoretically should be available to me. According to the FCC and other resources, I should be getting all of the high power DTV stations. I have talked to engineers at two of the stations I'm having trouble getting. They both said more than likely I'm getting a too high bit error rate due to signal multipath with all the hills around here. They said it is proving to be an issue for some viewers, and suggested I try VERY large directional antennas and experiment with antenna bearings, but admitted I'd probably need several antennas, one for each DTV station I'm not yet getting. Aarrgh! But of course many DTV's and converter boxes can only add channels by auto search; there's no provision for adding channels manually. That pretty much rules out switching between multiple antennas, unless I got the timing just right while the TV was performing its channel search. I could combine several antennas, but then I'd probably have the high BER due to signal reflections again. Grrr! Oh, and some of the stations that were/are broadcasting analog on VHF now have temporary UHF DTV assignments (higher power than their analog VHF). Next month they will be switching digital broadcasts to their old VHF channel assignments. This will probably change what I'm able to get and not get yet again... this time in the middle of a Maine winter. Grrr! Thanks FCC, or whoever is to blame for this bit of idiocy. I will admit when it works, picture and sound quality is fantastic with DTV. Being able to get free OTA HDTV is nice too. Paul
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, OK, that makes sense re the 004/005 markings. And OK on the knobs. That really messed with me at first. I thought they were glued or something. It was only when I tried heating one to see if the glue would soften that I found out it was solder! I didn't have any trouble with the top of the inner tube catching on the finger stock when I put them back in, but it was a real close fit getting them in without that happening. On each cavity there were, as I recall, two or three fingers that were sprung inward a little more than the others, possibly having to do with the ends of the two coil springs putting extra pressure on them. Those were the ones I had to watch closely. As long as it hasn't compromised the solder bond of the finger stock in some way, I'm not sure the worn copper plating will do much harm. Of course if the copper plate between the finger stock solder and the inside of the fixed inner tube has deteriorated in any way (which you can't possibly determine by looking), then that would be a serious issue. My guess is it's probably OK. I would just clean them up as best I could and try it. If you can't find someone who knows where the 004 and 005 loops go, I would try an experiment. I would put both 004 on one side of the duplexer, both 005 on the other side. I would then tune it up for high pass on the 004 side (low on the 005) and make a note of the performance measurements (notch depth, insertion loss, VSWR or return loss - measure all parameters on both low and high pass sides of course). Then I would retune it so the 004 side was low pass (and 005 side high pass) and measure the performance again. If there was any difference, I'd go with the configuration that produced the better numbers. If you try this, I would be interested in what you find out. Having said all that, it's also possible the loops were intended to go the way you found them... one 004 and one 005 on each side. That wouldn't be my first guess, but it's possible. It might have something to do with making the impedances look a little nicer or some such... Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I just noticed that what I wrote here was backwards... the 004s had the strap all the way around and the 005s had the wire extension. If I figure out what goes where, I'll let you know. Did you have trouble with the top of the inner loop catching on the fingerstock and tweaking it a bit? I bent a couple of mine, but it tweaked back into place okay. Mike WM4B
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes… looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white ‘stuff’ growing in there… have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed… a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is… which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike Besemer (WM4B) wrote: I have a strange feeling that it’s arching around the fingerstock. The inner tuning tubes showed definite signs of wear, but I THOUGHT the fingerstock was making good contact. Is there any ‘approved’ conductive lubricant for that area? Your problem sounds a lot like the trouble I was having with my DB4062 (the 6 cavity version of the 4060). I would get it tuned and think all was well, only to have major desense the next day. It nearly drove me nuts! What happens desense-wise if you tap lightly on the big tuning knobs while the transmitter is running? Do the cans make a nice scraping sound when you turn the knobs during tune up? Mine had the moving part of the center conductor and the finger stock coated with some kind of lubricant, which had partially dried up and was interfering with contact. Check the coil springs around the finger stock to make sure they are applying adequate pressure and are not stretched out. I also recommend you check and clean EVERY metal to metal mating surface, including where the box containing the coupling loop bolts to the cavity top. I wrote up something (incomplete) on my restoration project, which can be found here: http://www.repeater.n1bug.com/duplexerrefurb.html I think Mike Morris was going to put this on the repeater-builder site, but I don't see it there yet or I'd have given that link instead. (Mike Morris: I can supply a version of this minus the DHTML menu etc. if you want it) Almost one year since the restoration now and all's well... 73, Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, I can hear the fingerstock scraping against the inner tube... not a BAD scraping... just what sounds like good metal-to-metal contact. That is normal. The reason I asked is mine had stopped making that noise. It was almost completely silent when I rotated the knobs. That was one of the major things that led me to conclude something was really wrong inside. I knew silence when being tuned wasn't normal for those cans. After being refurbished it is back to making a healthy scraping sound. I was also thinking about cleaning the mating surfaces on the top... just need to get the gumption to do it. I'm getting tired of having my butt kicked! I know that feeling! I cleaned *every* mating surface while I had them apart, corrected some manufacturing sloppiness, and made a minor modification (which, I'm sure, was totally unnecessary, but I wasn't leaving any stone unturned). Good luck! 73, Paul N1BUG
Re: [Repeater-Builder] RE: DB4060 Duplexer Cables
Mike Besemer (WM4B) wrote: And as a follow up to my first question, as I understand it… there should be no problem with swapping the TX and RX cans (and retuning them), correct? That's correct for the DB4060 since the cans, coupling loops and notch capacitors are all the same. But it's not true for all cavities/duplexers. Some are designed to have the notch on one side of the pass only, where a specific can is either high pass or low pass but not the other. Actually even then it's more a matter of the coupling loops and/or notch tuning parts being different, not the actual cans themselves. I can't help with the cable length question. When I had my DB4062 (6 can version) apart I marked the cables. BUT, looking at them I thought they were all the same length. I didn't attempt to measure them since I was afraid straightening them to do that would put undue strain on them. Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] PLL UHF EXCITER
kb4ptj wrote: HI I WENT TO LBI 30200 AND LBI31209 THIS IS FOR THE EXCITER THAT I HAVE THE TUNE UP FOR I NEED THE PLL UHF 406-470 IF YOU CAN HELP ME WITH THIS I NEED THE TUNEING STEPS FOR PLL GE EXCITER There may be confusion as to what you really want. There is a UHF *FM* MASTR II exciter, but it is *NOT* PLL (it's the VHF FM that is PLL). The part number for your exciter would help clear things up... but try this one, for the UHF FM (non-PLL) exciter and see if it is what you want... http://repeater-builder.com/ge/lbi-library/lbi-31543.pdf If that is the exciter you have, the following LBI is also relevant... http://repeater-builder.com/ge/lbi-library/lbi-31209g.pdf Paul N1BUG
Re: [Repeater-Builder] db 4060 high band
Since you are not seeing a doubling of the notch depth with the two cavities in line, I suspect the cable length is incorrect as Eric pointed out. You also mention the tuning caps seems a little flaky. They shouldn't. It may be that they have been lightning damaged, since that is a known issue with these cavities. Or it may be something else. Some of my notch caps were very flaky (on a DB4062, which is the 6 cavity version of the 4060). Disassembly and thorough cleaning cured the problem. There was gunk interfering with contact between the finger stock and the tuning plunger. I also disassembled all the coupling loop assemblies and cleaned all mating surfaces. The duplexer is working perfectly now, with the caps being very smooth and stable. I am also getting deeper notches than I had before. Paul N1BUG Joel Hall wrote: Hope some of you guys that have some experince with db 4060 duplexer,the pass is fine but the notch is the problem I can see the notch at around 35db on my ifr 1600s per each can but when i combine them together about 50db is the best i can get I have new cables made 1/4 wave long , the tuning caps seem a little flakey may have had been hit with a lightning surge. I have not taken them apart yet so any thoughts? Thanks kj4si
Re: [Repeater-Builder] Build your own
Dave Gomberg wrote: I have long considered building my own 2m repeater out of 2 Icom 2100 or 2200 back to back thru a repeater controller, using a good duplexer and a Comet or Hustler antenna. My comments are not meant to discourage you but I once started out thinking along similar lines and it didn't take long for me to find out why it's not a great idea. Good luck. The receiver is broader than a barn door and I have no doubt the transmitter has higher noise surrounding the carrier than a good GE or Motorola crystal controlled radio. With the ham grade radios you will be far more likely to have desense problems and will likely need a larger, more expensive duplexer to have any hope of cleaning it up. 1. Nobody seems to like the Comet or Hustler antennas. Why? I have no ice here, lots of wind tho. I once wasted a month trying to make a brand new Hustler G6-144B run noise free in duplex service. Every time the wind blew I had loud crackling noise on my repeater. This may have been a problem specific to that individual antenna, since I know some people do use them successfully on repeaters. But it was so aggravating I never again tried using a ham grade antenna in repeater service. 2. Why is a 50w 2m transceiver, derated to 25w and driving a power amp a bad choice? Or is it OK? It might be OK if you put a fan on the heat sink. Most radios of this type will get far too hot even running at half power. Remember the duty cycle of a repeater transmitter is much higher than a user radio. Heat may not be the only issue. Some of the internal components may just be too marginal to handle high duty cycle service. 3. Any suggestions on how to keep the duplexer cavities affordable? Nope. 4. Which repeater controller? Or is that a religious question? Decide what features you want, then look to see which controllers offer what you want. Once you narrow it down to ones that meet your needs, you can decide based on price and user satisfaction (ask owners of those models how they like them). Anything else I should be wary of? As has already been mentioned, no foil/braid coax cables, and forget the single braided shield types too. You really want solid copper shield heliax, or at least mil spec RG-214 (double silver shield) if you don't want noise problems on your repeater. 73, Paul N1BUG
Re: [Repeater-Builder] db products 4060
I have a DB-4062, which is the 6 cavity version of the 4060. It was old when placed in service in 1997 but worked OK. Over the years it just slowly deteriorated until it became essentially unusable. Finally I took the thing apart to investigate, and was able to restore it to excellent function. Rather than typing up a lot of details, let me refer you to something I wrote about this a while back. http://repeater.n1bug.com/duplexerrefurb.html 73, Paul N1BUG Aaron Sloan wrote: Hello gang, I am wondering what the opinion is of the decibel products db4060 duplexers for 2m service. We have a set that are nearing 30yrs old and looking for a replacement. The current model never really preformed as well as the specs. Is this an experience shared by anyone else? Thanks, Aaron ka0zoz
Re: [Repeater-Builder] db products 4060
Dave Gomberg wrote: http://repeater.n1bug.com/duplexerrefurb.html Great write up, Paul, can you say something about how many hours you put in on it??? Uh, sure too many! Heh. Seriously, I didn't really keep track but must have been around 15 to 20 hours. Getting some of the parts clean enough to suit me was agonizingly slow. 73, Paul
Re: [Repeater-Builder] Power Supply from a PC. Slightly OT
The May 2002 QST article is available as a members only PDF. Just go to arrl.org and search for St Louis Switcher. Paul N1BUG kf0m wrote: May 2002 QST had the computer power supply conversion article QST switching power supply product reviews are July 2006, January 2000, and Sept 2000 John Lock kf0m at arrl.net
Re: [Repeater-Builder] DB4055 Duplexer
Nate, Thanks for bringing that to my attention! That is weird. The info I have in the document came from a Decibel Products catalog. We now have three freq ranges for the DB4076, all from manufacturer documents. Hm. Since official info conflicts, I guess all I can (or should?) do is add a note about the situation and list the various frequency ranges we have. I will add what specs that document provides on the 4075 while I'm at it. I'll add a note about the Z and W suffix which I wasn't aware of either. Sounds like you had a fun project there! 73, Paul Paul, Confused here... your document at that specs page shows the DB-4076 as being a high UHF duplexer (485-505 MHz) while right here on RB, the duplexer's manual says it's much wider (404-512) on the top of the manual, and then that same manual says it's a completely different range (450-512) in the description text in the document. Weird. http://www.repeater-builder.com/db/db-4076-tuning.pdf I'd just say it's a typo in the title of the manual... but... A friend and I just tuned a 4075 with an added can -- making it into a 4076 (the square/brown painted variety that were often found in GE MASTR II cabinets with a GE part number on them) -- to the 446 range tonight. Nate Duehr, WY0X [EMAIL PROTECTED]
Re: [Repeater-Builder] Freak Propigation
Jim Brown wrote: Is the big mountain behind it reflecting the signal over the pass to the south west? It's certainly possible. Big mountains make great VHF reflectors. I can often work stations to the north or east of my location on 2m FM simplex or SSB with stronger signals if we both point antennas at Mt Katahdin (which is generally north of all stations involved) than if we have beams pointed at each other... especially if the station is in a valley. This is true even when the reflected path off the mountain may be much longer than the direct path between stations. Also don't forget about knife edge diffraction of VHF signals over a mountain. I don't have a lot of personal experience here, but in theory I believe this works best if the mountain or ridge has a sharp rocky peak. 73, Paul N1BUG
Re: [Repeater-Builder] DB4055 Duplexer
Thanks Ron, I will include these specs in the next revision of the Guide to Duplexer Specifications on the RB site. http://www.repeater-builder.com/rbtip/duplexerspecs.html I'm always keeping an eye out for data that isn't in there yet. I've added several since the current posted version so it's probably about time to send in an update. 73, Paul N1BUG Ron Wright wrote: Eric, The DB4055 is 5 cavity band reject duplexer from Decibel Products. Its notch is 75 to 80 db at 5 MHz. Min freq separation is 5 MHz making it useless for 2 meters Ham repeater. TX noise suppression at RX freq 70 db RX isolation at TX freq 70 db. Max power is 150 W continuous and insertion loss is 0.7 db. The versions ar A=150-162 and B 160-174. Would be good for something like MARS or other commercial repeater. 73, ron, n9ee/r
Re: [Repeater-Builder] Re: Antenna Tower
You added www which wasn't in the original link. Try this (it's your first try with www removed) http://good-times.webshots.com/album/562985533mLTuoH 73, Paul Dexter McIntyre W4DEX wrote: I've tried several ways to put the link together with no success. These don't work for me: http://www.good-times.webshots.com/album/562985533mLTuoH http://www.goodtimes.webshots.com/album/562985533mLTuoH Is the picture still available? I've seen some 40+ year old towers that are still in very good condition. But I agree most that age aren't worth much if anything. Dex Rich [EMAIL PROTECTED] wrote: Antenna Tower steal 95 Ft tapered. Built in 1960, Central Pennsylvania. Must remove from the site owner wants a donation for it. Photo's available at http://good- times.webshots.com/album/562985533mLTuoH Contact Rich [EMAIL PROTECTED]
Re: [Repeater-Builder] Off Topic (but with on topic questions): NTIA propaganda
While it was told that ALL VHF television would move to UHF, I don't believe that is going to be reality. I could be wrong, however My local channel 12 is moving to channel 9 with the digital transition... 73, Paul N1BUG
Re: [Repeater-Builder] Re: Duplexers (budget test equipment)
Oops. I forgot to mention double shielded cable for ALL interconnects is an absolute MUST, at least with my duplexer - it has notches in excess of 120 dB deep after refurbishing. It doesn't take much leakage cause problems when you're dealing with notches like that. Paul N1BUG Paul N1BUG wrote: Jim Brown wrote: I have found that the main problem in using a talkie as the receiver for tuning the notch in a duplexer is the possible leakage of RF between the signal source directly into the talkie. Most talkies are not shielded at all, and any leakage will cause you to tune a combination of the signal through the duplexer and the direct signal leaking into the talkie. Yes, I had that problem as well. When I built my last 2 meter repeater (a semi-homebrew using custom re-packaged GE modules, mostly) I crystalled the receiver for both the repeater receive and transmit frequencies with a service switch to select the second frequency. I also built a simple op amp DC amplifier sampling second limiter voltage at a metering point in the receiver and use it to drive a signal strength meter on the repeater front panel. Of course my custom chassis is very well shielded. The receiver is peaked for the repeater input frequency, so it isn't as sensitive on the other frequency; but it is good enough to see the depth of my duplexer notches. I use an old (cheap!) Boonton 202E generator as a signal source, and put 3 dB pads on the duplexer ports (and a 50 ohm termination on whatever port is not used at any specific point in the tune up process). The Boonton is surprisingly stable once it has warmed up for a couple of hours. I've had good luck with this simple setup. But adding the signal strength meter to many commercial repeaters (or worse yet mobiles converted to repeater) could be more of a challenge. Paul N1BUG
Re: [Repeater-Builder] Re: Micor conversion question
15 pf and 12 pf in series would give you 6.7 pf, but if you have the space you could put them in parallel and have 27 pf. I'm sure that's what you meant to say. No guarantees on the specific item you're working with but usually putting a couple of caps in parallel to arrive at a needed value works just fine. I'd try that if it were me. Paul fxbuilder wrote: Thanks for the info. I found 39pf, and the 12pf, but the 27pf is illusive. I do have 33pf and 15pf. I'll assume I can try one as the replacement for the 27pf or can I put a 15 and a 12 in series?. Appreciate the help. Craig
Re: [Repeater-Builder] DB4062 woes...
Hi John, If you can get in touch with him I would interested to know more about what he did, especially if he cleaned the silver plated part (the plunger). Mine isn't all that dirty but I would like to clean them if I can do it safely. Also if he replaced the compound that the plunger is coated with, I would like to know what he used. I'm not sure what the stuff is, or why it is there - scratch prevention/lubrication, as and aid to electrical conductivity, anti-oxidation? In some of my cavities the stuff has started to dry out, so it ought to be cleaned off and replaced. Cavities I've worked on in the past didn't use any paste on the moving parts. 73, Paul N1BUG kf0m wrote: Hey Paul, another ham in my area had our DB4062 apart earlier this year for a similar problem lots of rx noise when I wiggled on two of the tuning knobs in the rx chain. He reported it to be discolored inside on the threads and rod but no pits and he cleaned them up. I will try to reach him and see if he remembers anything about the construction inside. John Lock kf0m at arrl.net -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of Paul N1BUG Sent: Wednesday, October 24, 2007 11:20 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] DB4062 woes... Well I finally got the courage to tear apart my duplexer. The spring and finger stock appear to be in excellent condition with good contact pressure. However... If you look at this picture: http://www.n1bug.com/cavity.jpg You can see the end of the tuning plunger. The tuning rod is soldered to this end plate. Silver solder I'd guess. What you can't see in this picture is that at the top of the plunger there is a similar metal plate... the rod runs through a hole in that plate, but is NOT soldered to it, and there is considerable play. This is where the audible vibration comes from when I lightly tap the tuning knob. My first thought was since this is up inside the center part of the cavity there wouldn't be any RF voltage/current at that spot. BUT... this cavity is extremely sensitive to vibration, producing severe desense with the slightest tap on or near it. I can find NO other sign of anything that might cause it. Could this loose metal to metal contact where the tuning rod enters the top of the plunger cause this problem? If so, why would it not have this problem when new, but develop it after many years? Seems there must have always been a bit of play there... no? I used this successfully for several years, then it became progressively more sensitive to vibration and started having intermittent periods of severe noise desense... but a tap or two here and there on the duplexer will either greatly aggravate it or temporarily cure it. If that could be the problem, the challenge is getting at it to fix it. The plastic knobs apparently have a metal insert and are securely SOLDERED onto the rod, so getting them off without burning them up is not trivial (at least not for me). If I unsolder the rod from the plate at the bottom of the plunger I would be able to pull the plunger part out the bottom, leaving the rod in place... but then there's no way to solder or otherwise secure the rod to the top end of the plunger to fix the problem. The only solution I can think of is to cut the rod just below the knob, and screw the whole thing out the bottom... solder the rod to the plunger top end plate, screw it back into the cavity and put a new knob on it. Any thoughts, please Paul N1BUG Yahoo! Groups Links Yahoo! Groups Links
[Repeater-Builder] Thanks re DB4062 project
Thanks to all who responded to my request for help/info on this duplexer restoration project. I returned it to service yesterday. I'm now seeing better measured performance than ever before, and I am unable to make it go noisy by lightly tapping it as I could previously. I have a good feeling about this, but because its problems were somewhat intermittent before I hesitate to say it is fully cured at this point. I see no evidence to suggest it isn't... I just want to see it stay this way for a while before I proclaim success. If there is interest I can post a lengthy report on what was done and the results, or maybe even write up an article about it. 73, Paul N1BUG
[Repeater-Builder] DB4062 woes...
Well I finally got the courage to tear apart my duplexer. The spring and finger stock appear to be in excellent condition with good contact pressure. However... If you look at this picture: http://www.n1bug.com/cavity.jpg You can see the end of the tuning plunger. The tuning rod is soldered to this end plate. Silver solder I'd guess. What you can't see in this picture is that at the top of the plunger there is a similar metal plate... the rod runs through a hole in that plate, but is NOT soldered to it, and there is considerable play. This is where the audible vibration comes from when I lightly tap the tuning knob. My first thought was since this is up inside the center part of the cavity there wouldn't be any RF voltage/current at that spot. BUT... this cavity is extremely sensitive to vibration, producing severe desense with the slightest tap on or near it. I can find NO other sign of anything that might cause it. Could this loose metal to metal contact where the tuning rod enters the top of the plunger cause this problem? If so, why would it not have this problem when new, but develop it after many years? Seems there must have always been a bit of play there... no? I used this successfully for several years, then it became progressively more sensitive to vibration and started having intermittent periods of severe noise desense... but a tap or two here and there on the duplexer will either greatly aggravate it or temporarily cure it. If that could be the problem, the challenge is getting at it to fix it. The plastic knobs apparently have a metal insert and are securely SOLDERED onto the rod, so getting them off without burning them up is not trivial (at least not for me). If I unsolder the rod from the plate at the bottom of the plunger I would be able to pull the plunger part out the bottom, leaving the rod in place... but then there's no way to solder or otherwise secure the rod to the top end of the plunger to fix the problem. The only solution I can think of is to cut the rod just below the knob, and screw the whole thing out the bottom... solder the rod to the plunger top end plate, screw it back into the cavity and put a new knob on it. Any thoughts, please Paul N1BUG
Re: [Repeater-Builder] DB4062 woes...
Thanks Scott, I really appreciate the reply! I find it extremely strange the knobs are soldered on also. You're probably right, although these knobs sure look identical to the ones in all the old Decibel Products catalogs, etc. But these knobs have NO holes for set screws or anything of the sort. At the repeater site I thought they were glued on. It was only after getting it home and in better light I realized they have a hefty brass insert and it's soldered to the rod. Strange, indeed. Thanks for the info about the grommet. Are there some with very thin walls? The hole the rod passes through appears to be only a few thousandths of an inch larger than the rod. I'd guesstimate maybe .020 clearance. I will see if I can unsolder a knob without incinerating it. I would like to keep the rods full length if I can, but there is enough length to tune my frequency even if I hacksaw through the rod below the knob/solder... drastic, but it has become pretty much unusable the way it is. 73, Paul Scott Zimmerman wrote: Paul, I have seen similar construction in cans. All of the ones I have seen have a small plastic grommet insert in the hole in the top of the plunger. It's a plastic insert like would be in a hole where wire passes through it. They are available at Lowe's and other hardware stores. I also find it EXTREMELY strange that the tuning knob is SOLDERED to the tuning rod. I guarantee this is NOT factory. There should be 2 set screws on the knob. Once they are loosened, the knob should spin right off. If I were to make a guess, someone has been playing around with this can(s). As I see it, you have 2 options: Fix it right - Unsolder the knob, take the plunger out, clean up the threads, re-insert the grommet and reassemble using a new knob if necessary. The other option is to unsolder the plunger using a torch, replace the grommet in the top, clean the solder from the hole in the plunger and the rod, and solder the plunger back on the rod. Alignment is not critical since you can simply change the tuning to compensate for any misalignment. I had done a similar procedure to a set of Wacom cans that the silver plating on the plunger had gotten wore off. (how I don't know) I unsoldered the plunger, cut about 1/4 off the rod and soldered it back fast. While I had the cans apart, I used some silver plating compound used for plating circuit boards on the plunger to re-plate them. I used LOTS of no-ox on them when I reassembled to try to keep them from being damaged again. After I was done, the cans tuned great and are working fine. The only thing noticeable is that the tuning rods are a bit further into the can when compared side-by-side with an un-modified set. Good luck, Scott Scott Zimmerman Amateur Radio Call N3XCC 612 Barnett Rd Boswell, PA 15531
Re: [Repeater-Builder] DB4062 woes...
Progress! Scott, or anyone... I got one of the knobs off. Removing them is not such a big deal as I thought. It turns out the brass insert in the knobs is threaded. They are screwed onto the rods AND soldered. Sheesh! The hole in the top metal end plate of the plunger is indeed just a little bigger than the rod... not much more than .010. Photo: http://www.n1bug.com/cavity2.jpg If there originally was an insulated insert I suspect it was a special item for this application (or at least not hardware store variety). But if there wasn't one then I'm left with the original mystery of why it didn't have this noise problem until fairly recently. So what now? I think I could solder the rod to the top of the plunger without dislodging the whole end plate. Is that a bad idea? Better ideas? Alternatively, I think I could just squeeze some .005 PTFE sheet in that gap, but there isn't enough clearance to allow overlapping the ends at all. Also it might not stay put or hold up well with time and vibration. I still can see no other possible source of the noise/desense in this cavity. Paul N1BUG
Re: [Repeater-Builder] DB4062 woes...
Thanks Ian. I've realized my idea of soldering these two pieces together is horrible. The length of invar rod from the top of the cavity to its bottom attachment point may be critical for temperature compensation of the cavity! I can't believe I was proposing to do such a thing! Looks like I need to insulate it somehow. I've been trying for hours to slip a piece of .005 PTFE sheet in that gap but it just won't go. 73, Paul N1BUG IM Ashford wrote: Paul, Excellent photos! The only reason these two pieces of metal have began touching each other is that the invar plunger or the silver tuning sleeve have become bent. This could be due to some rough handling of the unitsprobably when you were absent? Personally, I would drill a series of small holes around this top plate to produce a larger hole,cleaning up with a small round file, giving about 1/8 clearance between the plunger and the sleeve. I agree that any kind of heating would ruin the plating.. If the plunger is now free of the tuning knob then perhaps you could slip some heatshrink tubing into the gap and fix it with a heatgun.. Ian G8PWE - Original Message - *From:* Paul N1BUG mailto:[EMAIL PROTECTED] *To:* Repeater-Builder@yahoogroups.com mailto:Repeater-Builder@yahoogroups.com *Sent:* Wednesday, October 24, 2007 7:36 PM *Subject:* Re: [Repeater-Builder] DB4062 woes... Progress! Scott, or anyone... I got one of the knobs off. Removing them is not such a big deal as I thought. It turns out the brass insert in the knobs is threaded. They are screwed onto the rods AND soldered. Sheesh! The hole in the top metal end plate of the plunger is indeed just a little bigger than the rod... not much more than .010. Photo: http://www.n1bug.com/cavity2.jpg http://www.n1bug.com/cavity2.jpg If there originally was an insulated insert I suspect it was a special item for this application (or at least not hardware store variety). But if there wasn't one then I'm left with the original mystery of why it didn't have this noise problem until fairly recently. So what now? I think I could solder the rod to the top of the plunger without dislodging the whole end plate. Is that a bad idea? Better ideas? Alternatively, I think I could just squeeze some .005 PTFE sheet in that gap, but there isn't enough clearance to allow overlapping the ends at all. Also it might not stay put or hold up well with time and vibration. I still can see no other possible source of the noise/desense in this cavity. Paul N1BUG
Re: [Repeater-Builder] DB4062 woes...
Nate, I appreciate the sanity check. I've been known to overlook things like that and make some fine blunders! The gouges you refer to appear to be tool marks of some sort. What you can't tell from the photo is it looks like they were made BEFORE it was silver plated, so I'm assuming some tooling they used during manufacture. They are not as deep as they appear in the photo. Yup, I've checked the harness and connectors, etc. Yup, it does misbehave off site when hooked to other radio(s). Here's a possible clue I forgot to mention. The passband loss, SWR, and even the notches appear to be quite stable when I tap on it (using test equipment of course). However if tapped with transmit RF present, noise on the receiver is very bad. Two of the six cavities misbehave. The other four seem OK... for now... I hate to chop on these at all! But... Paul N1BUG Nate Duehr wrote: Paul N1BUG wrote: I still can see no other possible source of the noise/desense in this cavity. Just a sanity checking question... You were able to get the cavity to misbehave OFF the site and hooked to completely different interconnect cables and a different radio, right??? You've also carefully checked the input connectors and loops for being loose (center pin falling out, etc...)? Just asking if you've made sure you're chasing the right problem. Anything that could have physically moved when you were even lightly tapping the cans is suspect until the can was proven for sure to exhibit the problem and the connectors were carefully checked, right? Just checking... before you chop on those any further... In the first photo, what were the big gouges in the plate from? Those didn't look real good... but didn't seem to be sticking out off the edges at all. Any thoughts as to how those got there? Nate WY0X
Re: [Repeater-Builder] Re: DB4062 duplexer disassembly
Ralph Mowery wrote: It may not be glue but a form of locktite. If you heat the parts the locktite will usually let loose. OK, thanks. I tried heat but next time I will try a bit more. I've been preoccupied with another repeater issue this week. About 30 years ago we had a Phelps Dodge 6 cavity set that would give the same simptoms . Sent it back and it came back the same way. We opened up one of the cavities and found about a teaspoon of solder dropings in the cavity. A couple years ago I bought a DB4002 pass cavity and noticed it rattled when I picked it up to move it around. It worked fine, but being curious I opened it up. I found what I would guess to be a tablespoon of solder droppings in the bottom. It was interesting. Apparently loose metal laying at the bottom of a cavity doesn't adversely affect its operation, so long as it is operated in an upright position. 73, Paul N1BUG
Re: [Repeater-Builder] Re: DC INJECTOR AND PREAMP
Dan, If you and the group will pardon a somewhat long response, let me offer some thoughts. I think you said you were not particularly radio literate and it appears you aren't really understanding the difficulty with what you propose to do. I will attempt to explain. I am trying to find a DC injector that will power a preamp which can bypass for an output amplifier. As others have said this is technically possible but be prepared to pay for it. This type of system won't be cheap. Hint: I haven't really looked into it but I suspect a building closer to the antenna mast would cost far less. The DC injector isn't the problem, it's the extra hardware you're going to need to split the transmit and receive signals at the preamp (see below). From the GM400 I run to the duplexer at 25 watts. then, from the output of the duplexer to the antenna, I connect a dc injector, then I connect the amplifier for the output power of 150 watts. No. The amplifier has to go between the GM400 (GM300?) and the duplexer. The purpose of the duplexer is to isolate the receiver and transmitter from each other while allowing you to use one run of coax and one antenna. Everything associated with transmitting (such as the amplifier) goes on the transmit port of the duplexer. Everything associated with receiving (such as the preamp) goes on the receive port of the duplexer. At the antenna port you have transmit and receive signals on the coax at the same time - you cannot put any transmit devices (such as amplifier) or receive devices (such as preamp) here without a lot of extra hardware! What you propose to do is put a receive preamp in the part of the system that is carrying both receive and transmit signals. If we were talking about a normal base station, which is either receiving or transmitting (but not both) at any given moment, this would be reasonably easy by providing a switching system to bypass the preamp when the radio transmits. It's not that simple in a repeater which receives and transmits *at the same time*. In a single-antenna repeater system, the only way you can put a preamp near the antenna is to essentially have the equivalent of two more duplexers up there with it! It may be called diplex filtering as someone else here mentioned, but make no mistake it is going to require some expensive hardware. You would essentially have to split the receive and transmit signals, and then recombine them after the preamp. That's basically the function of *two* duplexers (one to split, one to recombine). You're also going to have some losses (both transmit and receive) in this hardware. In one of your posts you mentioned 250' of coax and in the other 350'. Which is it? Your transmit power figures indicate you are expecting 9 dB loss in the cable. That implies fairly poor coax in either case. What type of cable are you using? You say the budget allows for reasonable expenses. I would seriously look into getting a good low loss feedline. The cost of new 1-5/8 or even 7/8 heliax may be prohibitive, but in some areas you might be able to get it on the used or surplus market for less than it would cost to erect a building closer to the antenna. At 350 feet, 7/8 would have about 3 dB loss, a lot better than the 9 dB you seem to expect from your current cable. 1-5/8 would come in somewhere around 2 dB for 350 feet. The catch is, reading between the lines I get the feeling you are not well connected to radio people in your area, so you may not be able to find the deals if they are out there. My uneducated guess on the final output power on a 350' run of coax will be about 18.75 watts out. That is correct for 9 dB loss between the amplifier and antenna. However, as I said before the amplifier goes on the transmit port of the duplexer, so you will have the feedline loss plus the duplexer loss. Depending on the duplexer, it probably won't be much... probably around 1 dB give or take a bit. A 20 db preamp connected to a 6db gain antenna would be 1.625db at the repeater. Is that about right? I'm sorry, I don't follow what you mean here, but I'd have to say no, that's not right. Per your additional post about separate transmit and receive antennas, yes that may be an option. I'll let someone with the proper tools work out how far apart they would have to be. You're still going to lose a lot of trasmit power if you use the lossy coax, but the receive can be improved by running two antennas with the preamp up at the receive antenna... provided you can get adequate spacing between antennas. Which antenna goes on top depends on your needs and circumstances. I generally prefer the receive antenna on top, as receive performance is often the limiting factor in repeater installations. Without knowing exactly what coverage you need or whether you need to fully exploit the potential of your repeater site to achieve it, it's hard to say what measures are really
Re: [Repeater-Builder] DB4072-A UHF Duplexer Insertion Loss ?
The spec sheet says 0.8 dB insertion loss for 5 MHz tx/rx separation. Paul Shane Autrey wrote: I have just purchased a set of DB4072-A UHF DB products cans. I need to know what the insertion loss is on these from the manufacturers specs. Can anyone help me? I need this for my repeater co-ordination paperwork.. Thanks ahead of time.. Shane KI4M Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] fading desense
Ian Wells wrote: Would anyone have some sugestions on reducing desense fading in and out on a repeater.some information sugests checking out the antenna system .any sugestions? As has been suggested, try running the repeater only from batteries with all power supplies, charge controllers or the like off or disconnected. If you can be at the repeater site while the problem is occurring, listen to local audio from the repeater receiver while toggling the repeater transmitter off and on several times. Does the desense occur only when your transmitter is on? There are many possibilities either way, but in general... If it happens only with your transmitter on I would have a serious look at your antenna, feedline, mast, tower, duplexer for any problems. Make sure all connections and hardware is tight. It often only takes one loose bolt or guy wire to make trouble. Rusty/corroded hardware can be the culprit too. Try a different antenna if that is easily done. If the desense is still there with your transmitter off, I would suspect interference/noise from some nearby transmitter/device. I've been chasing a very similar problem that I believe I have narrowed down to a bad antenna. I'll find out when I replace it in a few days. Paul Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Re: SRL2352 weatherproofing
Thanks Harold. I'm not sure how the current version harness is done either. Sinclair sent me a diagram for the current model 235-2, but both it and the one that came with my older (1998) version are very poor when it comes to showing any details like that. It looks like (maybe) the current version uses all type N tees instead of the splices with gunk filled plastic shells over them. Mine uses N tees at each bay of dipoles, but has 3 of the splices in the harness. They did say those splices on the one I have are supposed to be weater tight as shipped, but I will see if I can add more protection. I hope I haven't made a bad antenna choice. I'm not too worried about intermod. There will be only one transmitter and one receiver on this antenna, plus 3 other nearby transmitters. I am concerned about longevity and potential desense/crackle from my own transmitter if problems develop in that harness. Paul Harold Farrenkopf wrote: Not sure if that is how the current 235-2 antenna harnesses are weatherproofed. Water in the harness is never good. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
[Repeater-Builder] scanner interference
So how can a scanner interfere with a repeater? I'm probably missing something basic but thought I'd ask anyhow. Given the original description of the problem Mathew has been asked to help solve, I doubt a scanner is the problem - hence I'm changing the Subject header... The local oscillator in scanners can radiate back out the antenna and be heard some distance away. Many scanners receiving in the VHF band have the LO offset below the receive frequency by whatever the IF of the scanner happens to be (10.7 and 10.8 MHz are both common, but there may be others). Years ago when I put up my first repeater I encoutered this problem. The repeater was on 145.110 and the original configuration was carrier squelch. As soon as I turned it on it started kerchunking rhythmically... bleep... bleep... bleep... After a few hours hunting I found a scanner one mile from the repeater site that was causing it. The owner had 155.310 programmed in the scanner and that one had a 10.8 MHz IF. Every time is scanned that frequency it keyed my repeater. 155.310 minus 10.8 equals 144.510, my repeater input frequency! The signal that thing put at the repeater site a mile away was quite strong. When the scanner stopped on 155.310 it put a darn near full quieting signal into my repeater receiver. I'm sure many others have similar experiences. Paul Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] db 4072
I have a spec sheet now, thanks. Any chance I can get a copy of that or some info quoted from it so I can add it to the next revision of: http://www.repeater-builder.com/rbtip/duplexerspecs.html You can contact me direct using the following address. paul_n1bug (AT) verizon (DOT) net Paul Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] G6 144b coil
I dunno... but for what it's worth I will share my experience. 7 years ago I tried a new-out-of-the-box G6 on my 2m repeater and had major trouble with it. I had loud crackling in even a moderate wind. Completely unusable in duplex service. I replaced it with something else, but last year I decided to try a G6 again... bought another new one and had identical problems to the first. Obviously some people use them on duplex systems and don't have problems... but I will not buy another one for use on my repeaters. They hold up well and I'd use them anywhere except on a repeater. Paul [EMAIL PROTECTED] wrote: I was interested in James reply because I had similar experiences with newer Hustler antennas. My club repeater, a friends repeater and my 220 repeater all used Hustler G6 and G7 antennas for years with good success. A couple of years ago, we decided to replace the two Hustler antennas at my friends site when he put the new tower up. The 220 antenna worked Ok, but the 2 meter G7 has been nothing but trouble. A friend in Westerly RI bought a G7 for his 2 meter repeater and also had trouble. Desense seems to be the common problem. Maybe there is something different between the old G6/G7 antennas and the new ones? It's just curious that 3 cases of a similar problem occured. I was careful not to ask James any leading questions about his experiences and he came up with the same conclusion. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
