RE: [Repeater-Builder] Wacom WP-639 Duplexer question
At 9/8/2010 18:24, you wrote: At 06:18 PM 9/8/2010, Richard Kelly wrote: We will be trying other things such as adding a second ground rod outside the shack instead of the single one we use now. We will also try isolating the amp some more and replacing the coax feed line with hard line. --That is a complete waste of time as that is not the problem. Your duplexer simply cannot provide enough isolation for the power level you're trying to run. More grounding and replacing coax with hardline (unless your coax isn't doubleshield to start with) will buy you nothing. Replacing copper-braided coax with RG-214 or hardline is hardly a waste of time. The duplexer isolation may not be quite enough, but that can be easily remedied by adding an extra pass cavity to the TX. Just another 10 to 15 dB of TX noise suppression is likely all you need. RG-8, RG-213 or LMR-400 antenna feed, OTOH, will make any duplexer moot due to all the desense it will generate, sooner or later. Bob NO6B
Re: [Repeater-Builder] Re: Circular polarization for VHF repeaters?
At 9/5/2010 08:23, you wrote: In my experience, cross-polarized antenna systems (those with simultaneous in-phase vertical and horizontal components) Isn't that just diagonal polarization? You can't have multiple linear polarization orientations; that's the whole point of circular polarization. Bob NO6B
Re: [Repeater-Builder] UHF Circulator
At 9/3/2010 18:56, you wrote: I'm looking for a UHF circulator to buy (or borrow). I have a mix that involves our transmitter but I'm not sure it's in our transmitter. We have a Micor repeater with the built in circulator but some feel an outboard two port is required for our nasty hill. It would be good if I could test one and not spend money on something that won't help. Aside from the the borrow request what do others think about this. Is more circulator than the stock Micor necessary? How far away are the other mix products? If more than a couple of MHz or so you could try a pass cavity after the Micor circulator instead of a 2nd circulator. -- Tim :wq A vi command? That old text editor will never go away! Bob NO6B
RE: [Repeater-Builder] Micor Pin Gunk
At 9/4/2010 11:13, you wrote: Tom, Motorola does not now, and never has, recommended DeOxit or any other contact enhancer gunk besides Stabilant 22. Up until just a few years ago, Motorola specified Stabilant 22A, under part number 1180369E78, which is a mixture of pure Stabilant 22 and isopropyl alcohol. Today, Motorola sells a kit under part number 1180384V93 which comprises a 5 ml bottle of pure Stabilant 22, an empty 15 ml bottle, and some tiny swabs. The 1180384V93 kit is sold by Motorola Parts for about $47, but is sufficient to last for years. This looks like the same stuff: http://www.micro-tools.com/store/P-22/Stabilant-22-5ml-Kit-Makes-30ml-Of-22a.aspx The description of how Stabilant 22 works reads very similar to the Caig Labs DeOxIt products. A performance comparison between the 2 products would be interesting. Bob NO6B
Re: [Repeater-Builder] Re: wouxun
At 8/31/2010 07:12, you wrote: Also saw a posting on e-ham that indicated only -30 dBc on harmonic spurious for the UHF side (I assume that's 2nd harmonic). I have an early KG-UVD1P (short DTMF burst) and an KG-UVD2D and can confirm this is not the case on neither radio, I measured -60dBc which makes them legal here. Good to know that the harmonic spurious is the same on VHF UHF - thanks. Since you have both, can you shed some light on the differences between the KG-UVD1P KG-UVD2D? Bob NO6B
RE: [Repeater-Builder] Re: Wouxun Radio
I see from the manual that the TX RX CTCSS frequency settings are separate. I'm wondering if this HT can really run split tone (encode decode separate CTCSS freqs.). Simply having separate settings is by no means an indication that it can, since my Kenwood TM-G707 has separate settings but the RX CTCSS tone only affects what tone is used for BOTH encode decode when in CTCSS squelch mode (as opposed to encode only). Anyone here actually have one that they could try? Also saw a posting on e-ham that indicated only -30 dBc on harmonic spurious for the UHF side (I assume that's 2nd harmonic). Bob NO6B
Re: [Repeater-Builder] Coax length
At 8/4/2010 14:37, you wrote: Doug Hutchison specialq@ntlworld.com wrote: Does the length of coax connecting cable between repeater and filters matter? Doug As long as the filters are working correctly, the cable length from the duplexers to the radios tx and rx does not matter. Having said that, remember that the shortest length of double shielded coax or HELIAX cable that will reach without kinks or physcial loads (binds) on the connectors should be used. This has nothing to do with impedeance matching, but rather cross talk thru cable leakage. Double-shielded cables aren't going to leak enough to be a concern. You do want to keep the length short to minimize loss. BTW, I once measured the isolation between a pair of ordinary RG-58 cables on a VNA from 50 to 500 MHz. Unless the cables were twisted together, I didn't see any coupling between them down to at least -90 dB. When they were twisted together, I think there was ONE frequency around 500 MHz where there was -65 dB coupling. On this same note (and knowing I'm going to stur up a hornets nest) I strongly advise against using the LMR type cables for ANY full duplex system. Any double sheilded cable which uses dissimular metals in the 2 (or more) shields will eventually cause rf noise . No argument here. Bob NO6B
RE: [Repeater-Builder] Narrowbanding
At 8/2/2010 06:37, you wrote: Florida Repeater Coordinator proposes narrowbanding: http://www.florida-repeaters.org/FRC%202meter%20narrowband%20p olicy%20released%207-18-10.pdf Apparently Carson's Rule works different in Florida than it does everywhere else. Well put, Jeff. IMO 10 kHz is about the limit for any kind of voice emission, it has to be digital in order to be anything less than 12.5 kHz. We have a small D-Star sub-band on 2 meters here in SoCal that's spaced @ 10 kHz it seems to be working. I applaud the FRC's initiative in wanting to do something to increase spectrum efficiency, but 7.5 kHz is simply going too far. Heck, some parts of the country can't even make 15 kHz work, have gone to 20 kHz spacing throughout the entire 2 meter band. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier
At 8/1/2010 01:15, you wrote: But there are other solutions: if you want a brute-force window filter they're out there too. I have a few 5 MHz wide 1 dB loss UHF filters sitting on the shelf here that I acquired at the Dayton Ft. Tuthill hamfests. ~$40 each. Seems like a good deal... but the 5MHz band-width is only (for me) usable in some system applications. Some of those applications where the 5MHz band-width would be excessive but the expected Simrex band-width would not be... Then we're back to the pass cavity solution. Just saying there are other inexpensive, well-engineered options out there. Again, the loss is low enough that in most cases a leading preamp simply isn't needed. Leading or Post Preamp? Leading meaning pre-preamp. Kind of makes it look like helicals are a sin doesn't it... Ever wonder why the MVP/MastrII Micors are so deaf compared to more modern RXs? Nope... I haven't measured the loss of the UHF helical assembly, but the VHFHB front-end helicals have ~6 dB of loss. In all those radios, their own helicals effectively are all the post-preamp filtering you'll ever need. No it isn't... if you sweep the front end of Micor you'll find it's actually fairly wide. I seem to remember sweeping some GE Receivers and their front ends were relatively wide on the order of at least a few MHz. From Memory I seem to remember the Micor being at least 4MHz wide. The VHF HB MVP front-end helical assembly has a 3 dB BW of 1.8 MHz. At 40 dB down the BW is 5.7 MHz. Granted the selectivity curves of the Simrex preselector curves are narrower, but keep in mind that they are in fact misleading, since most of that selectivity is AFTER the preamp stage. Add to that the fact that the mixer in the GE radios has very high dynamic range (remember, the stock GEs don't have a gain stage ahead of the mixer), you likely end up INCREASING the GE's susceptibility to IMD by using one. The GLB preselector preamp has 4 helical stages of unknown (unknown to me) coupling. Depends on the Pre-selector Model and age of the box ... I have GLB units here with two pre-device stages and three post-device stages. And I have versions with a more traditional helical design and others with more of a lumped parts layout. A 2-Meter version I have lots of pictures of has 1 stage of pre-selection and four trailing stages. The active device is an MRF-901. OK. MRF-901 NF @ 2M is ~1 dB, so maybe 2-3 dB NF for the unit. And that jives with my informal recorded notes for the 224 MHz GLB Pre-selector with a dual gate Mosfet. Not bad for VHFHB, but having only 1 little resonator in front of the active device doesn't offer it much OOB protection. Better put a (gasp) PASS CAVITY in front of it! ;) To quote someone who recently wrote: As you so often like to state, it all depends on the application - in many cases it simply isn't necessary. Agreed: in the above example the Simrex preselector isn't necessary: simply omit it use just a pass cavity. However, In more than a few real world situations you might really need the filter pre-selection a lot more than the most optimum NF. A practical trade of pre-selection for a slightly higher noise figure can and does sometimes make the difference in a usable radio system. OK fine. But again, we DON'T KNOW the noise figure for the device. It's not mandatory to know the NF for every situation, only helpful for those specific situations where making a logical assumption is not allowed. Kind of like saying you don't need to know how much output power your TX is running, so long as your users can hear it. Fun to play with? Yes. Can solve some IMD/overload problems? Certainly. But not a tool for any seriously engineered RF system. Bob NO6B Really depends a lot on whose money you're spending. I've seen a lot of seriously engineered RF systems that don't work very well out there in the real world. ...and in almost every case I've seen this, it's due to the engineering failing to take into account all of the real-world parameters. If your models are flawed, everything falls apart. Bob NO6B
Re: [Repeater-Builder] Re: Digest Number 7357
At 7/29/2010 22:30, you wrote: I never saw the highly modified HT-200 of Dick's but I have heard stories of the infamous Drinkie-Talkie (as I heard it referred by) from Neil WA6KLA several times over the years. I remember that Dick's 2m repeater was great to use and listen to in the Mid 70's on my trips into the LA area. Were you a member of his system? From what I remember it was a VERY private system: more than just CTCSS, DCS or DTMF to access it. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier
At 7/30/2010 08:31, you wrote: Re: Simrex - GLB Pre-Selector Pre-Amplifier Yes, but the NF is unpublished unknown. I therefore assume it's poor, maybe 3 dB? Once again, the NF depends on what device arrives in your specific Simrex (aka GLB) Pre-Selector. It wouldn't hurt or be impossible to ask. Nothing new here - same goes for different versions of preamps, i.e. ARR bipolar vs. GaAsFET. A Chip Angle GaAsFET @ UHF has 0.5 dB NF. Put a 1/4 wave pass cavity with 0.5 dB loops in front of it you have a narrow 1 dB NF front-end. I'll take 1 dB NF over 3 dB NF any day. You're actually comparing two different boxes. Nope - comparing GLB vs. GaAsFET/pass cavity combo. I have measured all the original GLB Pre-selectors and their performance values are very realistic (no surprises). Care to publish your results here? I guess it comes back to price too, a 1/4 wave can plus pre-amp will cost more money... GaAsFET preamp is ~$130. I don't think I've ever paid more than $50 for a pass cavity, so the total is ~$100 less than the GLB unit. Reads like you're comparing a new Preamp with a used cavity against the price of a new Simrex (GLB) Pre-selector. That's not really fair... Perfectly fair. Used pass cavities in good condition are plentiful. Can't remember the last time I saw a used GLB or equivalent unit for sale, so I'm simply comparing what's readily available. One of the really nice (and mostly overlooked) items about the Simrex (GLB) unit construction (and operation) is the Post (active) Amplifier Filtering (tuned circuits). For more than one real reason they can be one of the most under reported bacon saver in your fry pan. A single pass cavity usually has enough out-of-band rejection to be totally adequate on its own - no post-preamp filtering needed. Then again, the fact that post-device filtering is used in the GLB makes me worry about the actual selectivity ahead of that device. If there's only 1 or 2 resonators ahead of it, that's not much protection. A 1/4 wave bottle will provide much more rejection ahead of that first amp, and with less loss hence lower NF. IMO the Simrex amplified preselector is a space-saving compromise, nothing more. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier
At 7/31/2010 06:58, you wrote: Hello Bob, I agree that the GLB is a space saving device, but don't you think that the multistage helical coil stages in the preselector with beat a single cavity in skirts and out-of-band rejection? No. There is a compromise in that although the out of band (OOB) rejection looks really good, there is a caveat in that the active device in the preselector is NOT behind that selectivity curve. As Skipp points out, the filtering is distributed before after the preamp. Since we have no idea what that distribution is, the actual dynamic range of the preselector as a function of frequency is unknown. It does provide a lot of OOB rejection to the RX to connect it to, but you have to hope that the active device in the preselector isn't getting clobbered. Add to that the unknown NF, which is going to set your system NF, I conclude there are just too many unknowns in this beast to recommend it. Sure it works for many, but it's by chance, not by engineering. Bob NO6B
Re: [Repeater-Builder] Repeater trans mit levels at the receiver?
At 7/31/2010 09:31, you wrote: Joe - the picture was inside the e-mail. Bob - it is an SO-239 Tee, and it is into a dummy load. (checked on 2 different ones). Longshot, but try replacing the T, preferably with a silver-plated one. I know I've had old PL259/SO239 elbows generate desense when I tried using them on the duplexer output of my 2 meter portapeater. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier
At 7/31/2010 07:04, you wrote: Bob, Some of us are geographically disadvantaged when it comes to availability of equipment. Here in rural Australia, anything secondhand for Amateur Repeater construction is rare, shipping of anything is expensive. From what I read on the group, the U.S. Is overloaded with surplus equipment, sometimes at bargain prices. For me to buy and ship that cheap 1/4 wave can and pre-amp would be more expensive than buying a new Simrex Pre-Selector :-) I don't believe that. But if you want NEW coaxial resonator filters: http://anglelinear.com/filters/coax_filters.html' These are actually a bit smaller than your typical cavity resonator, they're very low loss. Apparently Chip decided to tradeoff a bit of Q to keep the loss low. But with 2 resonators you end up with a very low system NF selectivity only a bit less than the GLB (which is misleading, as I explained in my previous post because some of that selectivity is after the preamp, so it's still partially susceptible to OOB overload). If you factor in the ham discounts, the total for the dual coaxial resonator/preamp combo is a bit more than the Simrex preselector. But we KNOW the NF will be ~1.1 dB, we KNOW that ALL of the preselection will be ahead of the preamp, so with that info we can properly design a RX system. The Simrex units are made in the US, so you still have to pay to have it shipped down unduh. IF the Simrex-GLB product did not perform..the word would spread faster than the Black Plague and no one would buy them Not saying it doesn't work, but I am saying as an RF engineer that it's impossible with the data in hand to properly apply it's use in a repeater system. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier
At 7/31/2010 10:02, you wrote: Re: Simrex - GLB Pre-Selector Verus You're actually comparing two different boxes. n...@... wrote: Nope - comparing GLB vs. GaAsFET/pass cavity combo Still not the equivalent box... you're still missing the post active-device stages. I don't need them. But I suppose one could add a 2nd pass cavity AFTER the preamp. I've never had to do that in ~30 years of repeater building. I have measured all the original GLB Pre-selectors and their performance values are very realistic (no surprises). Care to publish your results here? Never thought about it much... those who were honestly interested in the subject the last time we rehashed the GLB active device topic here on the RB Group Emailed me direct and we exchanged various notes, diagrams and information. Much of what I have is based on the Pre-selector with the dual-gate mosfet, which I believe is similar to the BF-998 device. Why don't you tell us what you found? I've asked more than once for some reason you're reluctant to publish your results. I can't help but be even more suspicious of the GLB. Lacking the hard data, I'm going to do a little guesswork here: a typical GaAsFET preamp has 17 dB of gain @ 440 MHz. The Simrex preselector has a spec'd overall gain of 8 dB. All other things being equal, the combined loss of the resonators in the preselector would then be 9 dB. Kevin says the distribution is 2 stages before 2 after. If all the stages are equivalent, then the pre-active device loss is 4.5 dB. Assume 0.5 dB NF of the actual GaAsFET device, I come up with 5 dB NF. Am I close? GaAsFET preamp is ~$130. I don't think I've ever paid more than $50 for a pass cavity, so the total is ~$100 less than the GLB unit. Reads like you're comparing a new Preamp with a used cavity against the price of a new Simrex (GLB) Pre-selector. That's not really fair... Perfectly fair. Used pass cavities in good condition are plentiful. Can't remember the last time I saw a used GLB or equivalent unit for sale, so I'm simply comparing what's readily available. Yeah, but the numbers are off. To properly compare the two you'd need to use more than one pass-cavity. At least one additional cavity (min) following the active device and to really be honest, more than one trailing BP Cavity. See above, Kevin's post. In many cases, the trailing cavity isn't needed. A single pass cavity usually has enough out-of-band rejection to be totally adequate on its own - no post-preamp filtering needed. The post-preamp filtering can and does contribute in the management (not necessarily the prevention) of high signal levels issues. ..only for RXs that need it. I guess I'm a bit biased because I use real RXs (GEs), so the only protection needed is for the preamp going in front of it. Then again, the fact that post-device filtering is used in the GLB makes me worry about the actual selectivity ahead of that device. If there's only 1 or 2 resonators ahead of it, that's not much protection. A 1/4 wave bottle will provide much more rejection ahead of that first amp, and with less loss hence lower NF. There are 2 resonators in front of the Active Device. The higher Q of a 1/4 wave cavity is obviously better. The honest to thyself person should determine the NF difference, which is probably not a huge amount. Once again, I'm still waiting for the NF numbers. IMO the Simrex amplified preselector is a space-saving compromise, nothing more. Bob NO6B Sure, it's a compromise that works well for what they are. I'd probably (and do) park a Simrex or GLB Pre-selectors in front of less than bullet-proof receivers. Something else to consider: if your less than bullet-proof RX has good sensitivity, a preamp isn't even needed - just throw a pass cavity in front of it. Simple cheap, you'll probably still end up with better sensitivity than if you used the Simrex preselector. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier
At 7/31/2010 11:28, you wrote: Re: Simrex - GLB Pre-Selector Pre-Amplifier Kevin Custer kug...@... wrote: While the skirts and OBR of the GLB might beat a single cavity, many times it isn't necessary - The better skirts are mucho desired. As you so often like to state, it all depends on the application - in many cases it simply isn't necessary. But there are other solutions: if you want a brute-force window filter they're out there too. I have a few 5 MHz wide 1 dB loss UHF filters sitting on the shelf here that I acquired at the Dayton Ft. Tuthill hamfests. ~$40 each. Again, the loss is low enough that in most cases a leading preamp simply isn't needed. The problem is, like any receiver that has several helicals in cascade before the first active stage, the loss that precedes the active stage has a majority role in the overall NF of the system that follows. It matters little what the quality of the active stage is, because the loss has already determined (for the most part) the system Noise Figure. Kind of makes it look like helicals are a sin doesn't it... Ever wonder why the MVP/MastrII Micors are so deaf compared to more modern RXs? I haven't measured the loss of the UHF helical assembly, but the VHFHB front-end helicals have ~6 dB of loss. In all those radios, their own helicals effectively are all the post-preamp filtering you'll ever need. The GLB preselector preamp has 4 helical stages of unknown (unknown to me) coupling. Depends on the Pre-selector Model and age of the box ... I have GLB units here with two pre-device stages and three post-device stages. And I have versions with a more traditional helical design and others with more of a lumped parts layout. A 2-Meter version I have lots of pictures of has 1 stage of pre-selection and four trailing stages. The active device is an MRF-901. OK. MRF-901 NF @ 2M is ~1 dB, so maybe 2-3 dB NF for the unit. Not bad for VHFHB, but having only 1 little resonator in front of the active device doesn't offer it much OOB protection. Better put a (gasp) PASS CAVITY in front of it! ;) Every dB of loss ahead of the first active stage ADDS to the system NF - period. This loss can NEVER be recovered no matter how good the preamp is that follows. Kevin Yep. However, In more than a few real world situations you might really need the filter pre-selection a lot more than the most optimum NF. A practical trade of pre-selection for a slightly higher noise figure can and does sometimes make the difference in a usable radio system. OK fine. But again, we DON'T KNOW the noise figure for the device. Furthermore, since the filtering distribution varies with the model, it's very difficult to predict the dynamic range characteristics of the unit. Fun to play with? Yes. Can solve some IMD/overload problems? Certainly. But not a tool for any seriously engineered RF system. Bob NO6B
Re: [Repeater-Builder] Fw: TKR750 -Preamp
At 7/29/2010 11:34, you wrote: Another very good choice for this application is the GLB Preselector / Preamp from Simrex Corp. I have several of these deployed on 144 / 220 / 440 Amateur repeaters and they all perform very well. They can be tuned to maximize gain or selectivity per your requirements and their support is outstanding. ...but what is the noise figure? I'm going to ask this every time someone says they perform very well. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier
At 7/29/2010 14:59, you wrote: Re: Simrex - GLB Pre-Selector Pre-Amplifier The Simrex (aka GLB) units are actually amplified pre-selector assemblies, not just plain wide-band Receive Pre-Amplifiers. There's a reason why these units offer/spec 8dB Gain versus the others un-protected preamps. The less obvious gain when compared to traditional GasFet and BiPolar RF Preamplifiers is due to the internal integrated pre and post filtering. What does it all mean... If you have some types of IMD grunge problems when trying a regular GasFet/BiPolar Preamplifier, chances are your results using the Simrex/GLB pre-selector might be better. The pre and post filtering inside the Pre-Selector is a big deal. Yes, but the NF is unpublished unknown. I therefore assume it's poor, maybe 3 dB? A Chip Angle GaAsFET @ UHF has 0.5 dB NF. Put a 1/4 wave pass cavity with 0.5 dB loops in front of it you have a narrow 1 dB NF front-end. I'll take 1 dB NF over 3 dB NF any day. The Simrex unit makes a nice solution if you don't have the physical space for a 1/4 wave bottle. Then again, I know someone who just ordered an even smaller MtronPTI front-end crystal filter to solve a front-end overload problem from a TX over 1 MHz away from his RX. Not the best solution (higher loss, can't be retuned if he ever has to change freq.), but I guess it works for him. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier
At 7/29/2010 16:52, you wrote: Yes, but the NF is unpublished unknown. I therefore assume it's poor, maybe 3 dB? A Chip Angle GaAsFET @ UHF has 0.5 dB NF. Put a 1/4 wave pass cavity with 0.5 dB loops in front of it you have a narrow 1 dB NF front-end. I'll take 1 dB NF over 3 dB NF any day. The Simrex unit makes a nice solution if you don't have the physical space for a 1/4 wave bottle. Then again, I know someone who just ordered an even smaller MtronPTI front-end crystal filter to solve a front-end overload problem from a TX over 1 MHz away from his RX. Not the best solution (higher loss, can't be retuned if he ever has to change freq.), but I guess it works for him. Bob NO6B If you picked the UHF Simrex unit with less gain, more selectivity than the standard model, then the noise factor should be better? I doubt it. But without any real NF numbers, it's all guesswork. I guess it comes back to price too, a 1/4 wave can plus pre-amp will cost more money... GaAsFET preamp is ~$130. I don't think I've ever paid more than $50 for a pass cavity, so the total is ~$100 less than the GLB unit. Bob NO6B
Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector - Preamp
At 7/29/2010 19:04, you wrote: The Noise Figure is not always the most important specification. s. OK, I have an RFPA for sale that performs very well. And that's all I'm going to say about it. ;) Without a NF spec, it's impossible for an RF system designer to determine if the device is suitable for a particular application. Selectivity isn't everything either. Bob NO6B
Re: [Repeater-Builder] Re: Repeater receiver testing
At 7/27/2010 10:29 AM, you wrote:  Get a Mac. Much more efficient and crash free.. At the last coordinators' meeting I attended there was one laptop crash... Yup, it was a Mac ;) Bob NO6B
Re: [Repeater-Builder] Re: Repeater receiver testing
At 7/27/2010 10:15 AM, you wrote: case you haven't figured that out)). By the way, the GE PLL exciter has 22 dB less phase noise at 600 kHz from its primary carrier than does its multiplier counterpart, you can bet it's way more than that at 6 MHz. That 22 dB is an interesting figure: the amount of increased phase noise contribution as a result of multiplication is 20*log(N), where N is the multiplication factor. The multiplied-crystal G.E VHFHB exciter's multiplication factor is 12, which gives 20*log(12)=21.58 dB! My theoretical guess as to what would happen @ 6 MHz out is that the difference in phase noise between the 2 exciters would greatly diminish due to the Q of the tuned stages in the multiplied exciter kicking in. Bob NO6B
Re: [Repeater-Builder] Re: Repeater receiver testing
At 7/25/2010 15:54, you wrote: Hi Jeff yes I know -55db is I think around 399 microvolts which will flatten any receiver, I sure hope not; there are many signals coming down my antenna that are that strong. In fact, my 440 repeater 13 miles away is at about that level at my antenna connector. Bob NO6B
Re: [Repeater-Builder] Re: Duplxer, tuned cavity question.
At 7/20/2010 07:51, you wrote: OK, too much interperatation based on a lack of information. For 2 antennas you need vertical seperation (best) or horizantal seperation (very large), or 2 bandpass filters, one for each transceiver. Easiest solution, if you have the vertical real estate, use at least 25-30 ft seperation (preferably 40-50ft) between the antennas. I prefer to use top of lower antenna to bottom of top antenna as the measurement of distance. Charts often say center of antenna radiation. Horizontal seperation would require 300' for the same amount of isolation. Next best is a lesser amount of vertical seperation, coupled with bandpass cavities. Another option is a combination of pass cavities directional antennas. I once successfully ran a 2 meter 600 kHz split repeater with nothing more than 1 pass cavity, an omni TX Yagi RX antenna about 50 ft. apart horizontally. The TX RX used tubes, required weekly tuning precise aiming of the Yagi's null into the omni to keep the desense away. But it worked. If your target stations on either packet frequency are all in one direction, a directional antenna may lessen your filtering needs. Bob NO6B
Re: [Repeater-Builder] Controller recommendations
At 7/19/2010 09:30, you wrote: On 7/19/2010 10:02 AM, Joe wrote: S-Com can be a love/hate relationship. The older models did not have an RS-232 interface, so you needed to keep track of everything religiously on paper. BUT, they seemed to last forever. I have a few of them and they have never glitched..never. The newer S-Com controller has all the bells and whistles, including the computer interface. 73, Joe, K1ike heh-RS-232 on a ham controller was a pretty rare bird no matter what...only a few had it...til abt 7-8 years ago or so... ...so will be be another 7-8 years before we see a USB interface on all controllers? Bob NO6B
Re: [Repeater-Builder] Re: Controller recommendations
At 7/17/2010 19:04, you wrote: At 7/17/2010 14:04, you wrote: I have no interest here...but why just say it can be reprogrammed without explaining how. Thought the hobby was about communicationsometimes I wonder! What explanation? Sorry - at first read I thought this was a complaint about providing an explanation when none was requested. The only 4th column digits the RLC-1 uses are for the 1st digit of all default command names, which is C, for programming macros. For the former, simply change the command names for all 42 commands to something that doesn't use the 4th column. This can be done via the serial port or by using a radio that does have 16 button DTMF capability. Unfortunately I don't see a way around needing a 16 button pad to program macros, so strictly speaking my statement saying the RLC-1 not needing the 4th column is incorrect. But since the RLC-1 only has 7 macros it's not something you'd do very often. I haven't sent a 4th column digit to my RLC-1 in over 10 years. Bob NO6B
RE: [Repeater-Builder] Controller recommendations
At 7/16/2010 20:03, you wrote: ff-800 really hard to go to something else. Even when the something else was better. ...and the manufacturer is local ;) I personally don't like the FF-800, but as the original poster said he last used the ACC RC-96, the FF Systems unit might actually be the best choice because IIRC it tries to mimic the ACC programming paradigm. Bob NO6B
Re: [Repeater-Builder] Re: Controller recommendations
At 7/16/2010 23:41, you wrote: Steve, Based on your request about using your 12 button DTMF mic, I would recommend the Arcom RC-210. I have a few of the Arcom RC-210's, a couple Link-Com RLC-1's and a couple of the ICS Linker IIa controllers in our system. They all work great and the programming is about as different between the units as possible. The Arcom programs great with both the RCP Software and DTMF. The Link-Com RLC-1 can be programmed via a serial connection but is pretty clunky. It programs very easy with DTMF but does require the use of the A, B, C, and D tones. Not true - the RLC-1 can be reprogrammed to use only 12 digits. I have one in my system control it with a 12-button DTMF mic. Bob NO6B
Re: [Repeater-Builder] Re: Controller recommendations
At 7/17/2010 14:04, you wrote: I have no interest here...but why just say it can be reprogrammed without explaining how. Thought the hobby was about communicationsometimes I wonder! What explanation? Bob NO6B D On 17/07/2010 20:38:14, n...@no6b.com wrote: At 7/16/2010 23:41, you wrote: Steve, Based on your request about using your 12 button DTMF mic, I would recommend the Arcom RC-210. I have a few of the Arcom RC- 210's, a couple Link-Com RLC-1's and a couple of the ICS Linker IIa controllers in our system. They all work great and the programming is about as different between the units as possible. The Arcom programs great with both the RCP Software and DTMF. The Link-Com RLC-1 can be programmed via a serial connection but is pretty clunky. It programs very easy with DTMF but does require the use of the A, B, C, and D tones. Not true - the RLC-1 can be reprogrammed to use only 12 digits. I have one in my system control it with a 12-button DTMF mic. Bob NO6B
Re: [Repeater-Builder] Controller recommendations
At 7/16/2010 10:30, you wrote: I have RLC's and RC-210's both are very good controllers .. the Arcom RC-210 is very will supported and if you want a good controller I would go that route .. not to say the RLC's are not good I went back to my 2A and love it .. the RLC does the 220 repeater Rick I highly recommend LinkComm SCom. SCom has the best new product in the 7330 is cheaper, but LinkComm has several multiport controllers to choose from. Both are far more versatile than other controllers. Bob NO6B
Re: [Repeater-Builder] Transmitter Combiner
At 7/15/2010 13:53, you wrote: Maybe a pair of those 6 cavity mobile duplexers with the 5 MHz split can be configured as 6 notch sections each to reject the opposite frequency. and then combine them with a T to the antenna. Even though they're notch duplexers, each side has a very weak pass response, just enough so that you can't use the low pass side as a high pass. As a result, trying to use one as a 6-section notch filter by putting all the notches on the same frequency using the TX RX ports as input output won't work, as it would have several dB of loss @ 5 MHz offset, even more @ ~1.2 MHz. Another alternative to a full size 2 meter duplexer would be a dual isolator following by a pass cavity on each TX, then T the cans together using the correct phase-critical lengths of coax. Might be cheaper if you happen to have an inexpensive source for 4 VHF isolators. Bob NO6B
Re: [Repeater-Builder] FTS-12 tone deck
At 7/14/2010 07:18 AM, you wrote: WTB. I'm trying to get a Yaesu FT-33R HT on the air for repeater use and I need an FTS-12 Tone deck for it. Will consider an inoperative or parts rig with a good tone deck. FTT-4 Touch Tone pad would be a plus. E-mail to n8...@arrl.net. Pricey @ $79 but nonetheless a solution: http://www.piexx.com/index.php?main_page=product_infocPath=6products_id=31 Bob NO6B
Re: [Repeater-Builder] Tinkering with Repeater Controller firmware - source code
At 7/12/2010 20:56, you wrote: Jeff Lavoie - KB1SPH/WQEX694 kb1...@... wrote: Ok, I can get you the date code tomorrow if you find some spare time to check. It's too bad I couldn't get a copy of the original code and maybe modify it myself. I like to tinker around with existing programming a bit, but I wouldn't know where to begin if I were to start from scratch. Jeff, KB1SPH / WQEX694 I have to look at whet ever the processor is to comment on modifying the code. I'm reversing out the source code for one of the ACC Repeater Controllers and it's not for the casual person to attempt. At 443 pages of disassembled source code I'd say you really have to want to do something like this. And I'm doing it for fun... Was the original code done in an assembler (my guess, given the vintage)? Have you asked Link Comm if by chance they have any source code? Bob NO6B
Re: [Repeater-Builder] What have I got?
At 6/19/2010 08:44, you wrote: Not really an expert on that unit! General rule of thumb: when you have an existing exciter, the power amp (final) input is usually around 1/4 W (250mW) or higher. Most GE junk is 1/2 watt in. you cant go wrong with trying 250mw. The G.E. exciters I've measured show around 200 mW out. I once put a UHF exciter tuned to 450 MHz on an HP437 power meter got 183 mW. This seems to be more than enough to drive their RFPAs. Bob NO6B
Re: [Repeater-Builder] Re: GE MASTR Professional Equipment
At 6/13/2010 09:05 AM, you wrote: To All: I am going to get completely away from MASTR Pro equipment. If anybody wants anything, contact me off net and I'll see if I have it. Cost very cheep plus shipping. Anything not gone in three weeks is going to the trash. Fred W5VAY That's a shame Fred later down the road you might realize the GE Master Pro Receiver is one heck of a decent unit and still quite usable. Ditto, for the most part. The IF/detector/squelch is a bit quirky (mine always quiet better on one side of center freq., open squelch easier on the opposite, noisier side), and the IF is a bit wider not easily narrowbandable like the MVP/Exec II/Mastr II series - a problem when using the VHFHB RXs @ 15 kHz channel spacing on 2 meters. But the inherent shielding filtering you get with the case makes them really convenient to use in certain situations. Also never heard of any tin whisker problems with those RXs, maybe because there's no tin in the helical housing? Bob NO6B
Re: [Repeater-Builder] active low COR
At 6/3/2010 07:16, you wrote: Hi Scott, Many controllers have pullup resistors on their COR inputs so that they can be driven from open collector or relay contact COR outputs. With that arrangement, if the controller is configured for active high and the COR line is disconnected, the controller will think the receiver is active. The best arrangement is the one that works for you. There aren't any standards -- except perhaps in industrial control, where there are fewer active low circuits due to the possibility of activating a circuit due to a pinched wire. I use active high on the COS active low on the CTCSS. That way any failure that occurs equally to both lines will not key the TX. Bob NO6B
Re: [Repeater-Builder] 220 duplexers
At 5/27/2010 14:16, you wrote: Scott LOL! I'm gonna check my glasses prescription. FWIW, I had a similar issue with a split antenna rptr many years ago and resolved it by swapping antennas. The complaining stick was on the xmtr side. When it was just dealing with signal levels, it was as quiet as a church mouse. It was a temporary fix and I doubted it would last very long but surprisingly it outlasted the repeater itself. We've had similar problems at 2 sites with separate TX RX antennas. One would start generating noise after a lightning strike, so we swapped them, putting the struck antenna on RX. Been working fine since. Bob NO6B
Re: [Repeater-Builder] White Noise on Micor TX
At 5/22/2010 21:10, you wrote: I have a small amount white noise on the TX of a Micor repeater. It is most noticeable in the hang time but it's not coming from the controller. It's still there with the controller completely removed and pressing PTT on the station control card. It's more noticeable on some radios, perhaps radios with higher audio frequency response. Anyone ever run into this before? Tim WD6AWP I never heard of this problem on a Moto radio, but the G.E.s will do this if the CG (PL) input on the TX is left unloaded. Somehow a bit of the RX's discriminator output leaks into the phase modulator. Apparently it has a very high impedance, as any load on it eliminates the problem. You might loading the PL input on the Micor see if it has the same effect. Is this a VHF or UHF radio, is it currently on the air? (I can probably hear it from here) Bob NO6B
Re: [Repeater-Builder] Lost 10 volts in a Master II UHF Repeater
At 5/22/2010 07:28, you wrote: On Sat, 22 May 2010, Chuck Kelsey wrote: And sometimes scare the crap out of you! And they stink. They make a cool purple smoke with lots of sparks when they flame out! IIRC they contain an element you're not supposed to breathe because it only causes cancer in the state of California. I thought they were perfectly safe because there's no prop. 65 warning label on the radio ;) Bob NO6B
Re: [Repeater-Builder] How much gain or how much loss on the PD220-3A
At 5/21/2010 12:16, you wrote: Yup-that was me! I got that info from my dad actually back in the 70's, not long after he left New-Tronics. Here's the link to the article on RB: http://www.repeater-builder.com/antenna/retuning-a-stationmaster.html I did this mod. to a UHF StationMaster a few years ago. Worked very well though the actual gain is a couple of dB off from a GP9, as you'd expect since it's about 5 ft. shorter than a GP9. Bob NO6B
Re: [Repeater-Builder] Duplexer notch blurred - why?
At 5/19/2010 15:29, you wrote: Hi In the attached picture you see the notch of the 70cm duplexer I built according to W4NFR's description in QEX, those who can't receive attachments find it here: http://conturafm.mine.nu/_fh/438.95_notch.bmphttp://conturafm.mine.nu/_fh/438.95_notch.bmp The measurement has been made with both cavities of one branch connected with a true quarter wavelength jumper of RG58 because I had no double-shielded cable available. Can anybody tell me why the notch is this blurred and what can be done about it? The isolation would be a bit better if the notch was a clear sharp line, isn't it? I'd try a different length jumper between the cans see what happens. As others have pointed out, you could use a little more signal in the vicinity of the notch. On my tracking gen. I narrow the sweep down to only the notch region so I can boost the generator power without overloading the spectrum analyzer. Bob NO6B
Re: [Repeater-Builder] PIC stuff at Hamvention?
At 5/17/2010 18:22, you wrote: On Mon, May 17, 2010 at 09:16:32PM -0400, MCH wrote: Either that, or it was disinformation (although it's easy enough to verify - I just didn't want to pick up the TT4 and look at it since it was connected and operating). One of his products even has PIC in the name. I can confirm that the TT4 uses an ATMega... built version is SMT (but I've never handled one), the TT4 kit I built and am using is in DIP-40. I don't think a PIC would handle encoding/decoding, and KISS support along with the tracking code and the like. I wouldn't be so sure. Like PICs, the ATmega644P is an 8-bit device. Max. clock speed is 20 MHz. Some high end PICs can run @ 40 MHz. The TT3+ used a mid-range PIC (16F series), which probably wouldn't be up to the task of decoding, at the assembly level the mid high range PICs aren't code-compatible, so porting code from the mid-range probably wouldn't be any easier between the high-end PICs the Atmel. Bob NO6B
Re: [Repeater-Builder] PIC stuff at Hamvention?
At 5/16/2010 02:57 AM, you wrote: Actually, Byonics is using the AT Mega (sp?). I specifically asked. At least, that's what the TT4 is using. They must have switched processors, as my TT3+ uses a PIC. Bob NO6B
Re: [Repeater-Builder] PIC stuff at Hamvention?
At 5/15/2010 18:20, you wrote: Sorry for the slightly OT post, but has anyone seen any PIC stuff at the Hamvention? Looking for PICs, PIC manuals, PIC-based kits, Etc. What do you want to do with PICs? The actual PICs can be had from Mouser or DigiKey. I bought a programmer from Futurlec for ~$60. I never saw any PIC-specific vendors at Dayton, though Byonics (APRS trackers) is usually there as well as ICS (repeater controllers), their products are PIC-based. Bob NO6B
RE: [Repeater-Builder] Unidentified Micor Part
At 5/11/2010 21:07, you wrote: For those who wonder how the TFD61x2 filter can impair the transmit signal at 2m, look at the attached plots. The TFD6102 filter is electrically identical to the TFD6112, and the TFD6101 filter is electrically identical to the TFD6111. Although there will be some variation between individual filters, it is quite obvious that a commercial-band filter severely attenuates a signal at 2m. So was this filter Motorola's way of dealing with the undesired harmonic subharmonic products from the exciter? Wondering why they felt they needed a BPF, not just a LPF. Bob NO6B
Re: [Repeater-Builder] Dayton to Evansville, IN
At 5/11/2010 11:15, you wrote: Leaving for Dayton tomorrow morning (weather forecast has improved a bit, looks like both Saturday and Sunday will be decent). After Dayton I'm headed to Evansville, IN. Any repeater-builders out there with machines between Dayton and Evansville (via Cincinnati and Louisville - I-75, I-71, I-64)? Got a new truck in March and still haven't had time to put the stack in, so will just have 2m and 440 this trip. I won't be there, so everybody have fun keep your vehicles locked. As far as repeaters go, my area favorite is the WB8VSU 442.300 (+) 123.0 Miamisburg system. Has IRLP (node 4235) I've been told it now makes it down to Cincinnati. Bob NO6B
Re: [Repeater-Builder] Re: CTCSS Encoder/Decoder
At 5/7/2010 04:21, you wrote: We have been experimenting with building CTCSS Units using the 567 Tone Chip and good components, i.e. Caps, multi turn pots etc. The stability is not good in my opinion. For encoding, there's a million PIC-based solutions on the net. I designed my own, using a different PIC (12HV615) to reduce extra components to minimal: it has a built-in voltage stabilizer (no 78L05 needed, just a resisitor), and using bitstream D/A so no external D/A network neccessary. By bitstream D/A do you mean PWM? If so, how fast do you clock it how many serial bits do you use to create each sample? For decoder, check out http://www.mcarcoh.org/ke8rv/photo-sd.html, specific the comments about his controller. I exchanged mail with the designer and his design is facinating, though not publically available, which is understandable. It's really mind-boggling what can be done with PICs. I see Don's using the analog input of a fairly low-end PIC, but I'd think you could use a digital input if the output of the LPF was limited via a very high gain amp. stage, a la ComSpec. Did he implement an IIR filter in the 12F675? Bob NO6B
RE: [Repeater-Builder] CTCSS Encoder/Decoder
At 5/6/2010 08:22, you wrote: At 07:55 AM 5/6/2010, Stanley Stanukinos wrote: I must be missing something, there are several MFG of encoders/decoders still around. You are correct on the stability issue. You will find it much less frustrating to just buy off the shelf or get the one for your radio than trying to build one that is stable. Oh there is the cost of the new ones so that has to be figured in. We have CML Micro MX-828s in stock if the OP is interested in purchasing one or two (or 3 or 4 g). Contact me offlist about them. And yes, NE567's (or their derivatives) were never designed for use as a CTCSS decoder as they cannot possibly maintain the frequency stability (nor have the narrow bandwidth) required for that use. Actually, the chip itself is inherently just stable enough - ~+/- 1%. Just have to use stable timing components. They also can be made as narrow as you want by selection of the loop filter capacitor value. The problem is the decode time @ 1% BW, which can be as long as 2 seconds @ 100 Hz according to the datasheet. Bob NO6B
Re: [Repeater-Builder] Re: CTCSS Encoder/Decoder
At 5/6/2010 19:09, you wrote: Skipp, I suspect that you were the exception rather than the rule, then. To me there are better ways to do it than a 567. I remember playing with various 567 circuits back in the 70's. Never could get reliable performance. Used them for paging frequencies. Gave up and started using commercial encoders and decoders and never looked back. Maybe you can give the guy some guidance to get some stability and choke down the bandwidth so that adjacent tones don't false the thing. The problem is if you reduce the BW to +/- half a standard tone freq., the detection time becomes unacceptably long. I tried using them for both DTMF CTCSS detection a long time ago. Compared to commercial CTCSS decoders, they were more prone to falsing and/or talkoff. Eventually I found a cheap, reliable solution: take a ComSpec SS-32 encoder add the decode circuitry (the SS-32 the TS-32 use the same divider/encoder IC). I still have that decoder it still works just as good as an actual TS-32. Though my 567s seemed to work OK as DTMF decoders, a lot of other people had problems getting them to reliably decode, probably due to the timing capacitor changing value with temperature. Bob NO6B
Re: [Repeater-Builder] Strange Signal on 158.275(ish)
At 4/28/2010 15:19, you wrote: Can anybody identify the signal in the attached file? It appears on 158.275 +/- 5 KHz or so. I set my receiver to AM mode for this recording. It does appear in FM and NFM, but not as clearly. Note that the PRF is not fixed... it does vary over time. It is audible over a fairly large (10 - 12 miles that I've checked so far) area. No idea what it is, but listen closely around the 9-10 second mark. Almost sounds like a faint noisy echo, or perhaps a distant responding station, which would be a form of ALE. Bob NO6B
Re: [Repeater-Builder] Re: IFR 1000s
At 4/24/2010 20:20, you wrote: Jim, Try this guy, Kurt Gruber. kurtgru...@yahoo.com That should be kurtgra...@yahoo.com. Bob NO6B
Re: [Repeater-Builder] Frequency Listing Sites
At 4/23/2010 09:09, you wrote: Hi Folks - Right now I am looking at http://www.freqofnature.comhttp://www.freqofnature.com and wanted to pick your brains on that site. Is it good, trustworthy? Reliable? Any HAM repeaters in that range that I can listen in to as well? For SoCal ham repeaters try http://rptrlist.w6jpl.ampr.org. Bob NO6B
Re: [Repeater-Builder] Sinclair C-Series cable lengths
At 4/19/2010 10:24, you wrote: I have 2 C-Series bandpass cavities, with individual I.L. set at 1.0 db each. When I couple them together and measure, I get a total I.L. of 2.9 db. I should see something like 2.1 or 2.2. I have measured the coupling cable and see .1 db, so the cable is good. Anyone have an idea why the loss is so high when coupled? Did you actually measure the individual loss of each can, or are you just going by the indicators on the loops? Try changing the length of cable between the cans. I think an electrical 1/4 wave multiple (1/4, 3/4, 5/4, etc.) is what you want. Bob NO6B
Re: [Repeater-Builder] Sinclair C-Series cable lengths
At 4/19/2010 17:24, you wrote: These are measured values using a Service Monitor. I have two charts that show the cable lengths, but the values are not the same. They differ by 1 for the same frequency. Would that produce the effect I'm seeing? Depends on what frequency band we're talking about. 1 is not enough @ 2 meters to make a significant change. Try changing the length by about a foot for 2 meters, or 4 @ 440. Bob NO6B
[Repeater-Builder] Wanted: G.E. VHF HB UHS preamp
Bought one several years ago from Kevin @ the Repeater-Builder booth in Dayton. Works very well (~0.13 µV for 12 dB SINAD on the MVP it's in), but now I need another one. Got another one, Kevin? If not, does anyone else? BTW, I did the antenna-load sensitivity substitution test last night on 2 MVPs, one with one without the preamp. The MVP with no preamp showed ~5 dB SINAD degradation between the antenna load. With that much noise coming down the antenna, reducing the noise figure of the RX doesn't help much, maybe a dB or two. But once you throw in the duplexer loss, which in this case is 2.1 dB, the antenna noise is reduced to only 3 dB over the load. Now the preamp improves actual sensitivity by 3 dB, which is just enough to make it worthwhile to use IMO. In addition, this will be for a portapeater that will be deployed in a rural area so the antenna noise will probably be lower. Bob NO6B
Re: [Repeater-Builder] Cooling Fans, which brand?
At 4/12/2010 22:43, you wrote: Hello to group, Anyone have a brand they recomend for a no noise, reliable fan. I didnt know whether to go with brushless,ball bearing,AC, or DC etc. Also should the power leads be sheilded and have a separate supply if DC.. Any filters recomended also.. I prefer AC fans because they generate less noise. I do have some 12 V CPU fans on the backs of a couple of MVPs in service, but have had problems with low levels of fan noise on some of them. If you have a choice, AC fans are easier to work with IMO. Bob NO6B
Re: [Repeater-Builder] 220 link equipment
At 4/12/2010 08:34 AM, you wrote: At 08:16 AM 04/12/10, you wrote: I'm making plans to link my 2-meter repeater to a 220 mhz hub repeater. What type of transceiver, radios, etc is best for a 220 link ? Thanks ! One big question is what's your duty cycle going to be? Another is what is your potential desense going to be? Back before we lost 220-222 one system in an area that used in-high and out-low on UHF was going to use a couple of low end channels as inbound link frequencies until he did the math... There was no way he could make a 250w system near 441.750 live with a receiver near 220.800. Why not? If the TX were 220.80 I could possibly see an unresolvable 2nd harmonic issue, but subharmonics from the 441.750 TX can always be suppressed. A long time ago we had such a problem with 1/2 the TX freq. of a UHF MVP equal to the input freq. of a 220 repeater at the same site. Had to pull the exciter out of the MVP put it in an RF-tight box, but there were no problems after that. Bob NO6B
Re: [Repeater-Builder] Xtals for Mastr ExecII
At 4/11/2010 12:01, you wrote: Well it looks like I need a new tx xtal for my UHF ExecII repeater. The current xtal has suddenly jumped about 50KHz high on UHF What are the current prefered vendors? I know about International, any other reliable ones? Did this happen while in service, if so have you opened up the radio yet? I recently had a VHF MVP's TX suddenly jump up 35 kHz. Turned out the xtal module connector was dirty. At the same time the RX died; that was due to a dirty connector on the IF/detector board, resulting in intermittent 10 V RX OSC voltage. Connectors are becoming quite the weak link in this radio series. Thank goodness for DeOxIt. Bob NO6B
RE: [Repeater-Builder] 2 Meter Bandpass Filter
At 4/5/2010 19:33, you wrote: So the answer is YES the Decibel VHF 6 Repeater cavity filter 148-174 DB4001-1 Will tune right to 144.315 and not lose the Specs it would Have at 148 ? I have one around here somewhere that I'm sure I've tuned down to 144.39, so I'd be very surprised if it didn't. And dos the Length of the Coax going to the Micor /Mobile have to be cut at a Certain Length No. Bob NO6B
Re: [Repeater-Builder] Re: D-Star Was: Molotora Gontor
At 4/5/2010 06:24, you wrote: I think it would be difficult to justify sole source on a piece of equipment that is part of a low volume market, such as amateur radio. Actually, it would be quite easy. Icom is the only source of D-Star equipment, so you only have to state that the unique features of the D-Star protocol are required by your EmComm entity. Bob NO6B
Re: [Repeater-Builder] 2 Meter Bandpass Filter
At 4/5/2010 11:38, you wrote: Hello hope Everyone had a Nice Easter I am Setting up a Motorola Micor Mobile on 144.315 and Will be using a Advanced Research Preamp and thought it would be a Good idea to put a Band pass on it , I came across this But can it be tuned down to 144.315 Without losing anything And dos Length of cable from this to the Radio have to be a certain length . This will be a link not a Repeater. Decibel VHF 6 Repeater cavity filter 148-174 DB4001-1 Or would something like this http://tinyurl.com/yd3b2fahttp://tinyurl.com/yd3b2fa The cavity filter, definitely. The Cross Country Wireless filter, though interesting, is way too wide for this application as it doesn't even have good rejection @ 150-160 MHz. Bob NO6B
Re: [Repeater-Builder] D-Star Was: Molotora Gontor
At 4/3/2010 15:35, you wrote: I would strongly remind them that they are purchasing a system that has only ONE and only ONE supplier/source. This may not fit some of the bid requirements that some government agencies require. Joe A well-written sole source justification memo takes care of that. Bob NO6B
Re: [Repeater-Builder] D-Star Was: Molotora Gontor
At 4/2/2010 09:49, you wrote: There's also a substantial base of users who like D-STAR because there isn't a scanner that can decode it. Funny you should mention that. A pair of bootleggers using D-STAR showed up on the input to a friend's 2 meter analog repeater. After a couple of months he decided to buy a D-STAR HT so he could listen in eventually make contact. As soon as they heard another voice they were gone haven't been back. Bob NO6B
Re: [Repeater-Builder] Helix / Connectors
At 3/31/2010 05:20, you wrote: I'll take copper any day. As Jeff said, one site visit to fix a bad aluminum cable connector on the top of the tower and you've lost all that you saved plus more. Jope Aluminum hardline was once banned at one mountaintop site I rent from. Bob NO6B
Re: [Repeater-Builder] Squelch crash on a MSR2000
At 3/24/2010 01:39, you wrote: At 06:10 PM 03/23/10, you wrote: At 3/23/2010 03:05, you wrote: Are you aware of the old GE and RCA technique that was given the derogatory name of chicken burst ?? It's how everybody avoided a patent infringement lawsuit from Moto Legal in the 60s and 70s. I never heard a G.E. radio do that (drop tone before dropping TX). You never listened to a Mastr-Pro or a Prog? Can't speak for the Prog, as I never had one with CTCSS. But I don't recall hearing a Mastr Pro drop tone before TX; I assumed they simply didn't bother implementing any form of STE. Dropping tone is a crappy way of doing STE, since you have to hold the TX on for at least a 3/4 of a second to make sure all the decoders have stopped decoding. Bob NO6B
Re: [Repeater-Builder] Re: GAW/Motorola Test equipment
At 3/23/2010 15:07, you wrote: Just about the time Detwiller came out with that service monitor (SM-512) based on a Bearcat BC-210xlt, AIE sent us a flyer introducing a similar product under the Measurements name. From what I remember, it was a rectangular box like a CE-50 and based on a mobile scanner using LED bar graph displays instead of meters. Batesburg, Va. Wasn't it? Never heard anything about them after that. Sounds like my FM-110. AIE is still around but no longer in the service monitor business. Bob NO6B
Re: [Repeater-Builder] Squelch crash on a MSR2000
At 3/23/2010 03:05, you wrote: Are you aware of the old GE and RCA technique that was given the derogatory name of chicken burst ?? It's how everybody avoided a patent infringement lawsuit from Moto Legal in the 60s and 70s. I never heard a G.E. radio do that (drop tone before dropping TX). I have both MVP (Versatone, which respond to G.E. reverse burst) Mastr Pro RXs (don't respond to reverse burst) uplink RXs in my system, so I added a delay to my Mastr II uplink TX in order to get reverse burst followed by about half a second of unmodulated carrier before TX drop. Bob NO6B
Re: [Repeater-Builder] Welcome to Dayton (Partial Hamvention Primer)
At 3/21/2010 09:47, you wrote: 12. If you are in the left lane, and only going 70 in a 55 zone ... you are considered a road hazard and will receive flashing lights and blaring horns from other drivers.. Not sure which Dayton you're referring to, but I found drivers in the eastern half of the country to be quite abiding of speed limits. And I've also found the local law enforcement to be quite efficient in enforcing said limits. Bob NO6B
Re: [Repeater-Builder] OT: If you are a Windows XP or 2000 user you might find this interesting...
At 3/13/2010 11:54, you wrote: The hard drive manufacturers are changing the native drive sector size... industry wide. Since XP and 2000 are frozen (no more major updates) they are going to take a performance hit. See http://www.dailytech.com/HDD+Makers+Adopt+Improved+Storage+Format+Windows+XP+Users+Beware/article17869.htm If the performance degradation ends up being significant, don't be surprised to see 3rd party native support for the 4k block size appear, similar to the non-Microsoft USB drivers for NT 4.0. Bob NO6B
Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
At 3/10/2010 02:42, you wrote: On Mar 9, 2010, at 8:37 PM, n...@no6b.com wrote: t most certainly does. Try random length cables from the cavities to the T instead of 1/4 wavelength (like one local did several years ago) watch your sensitivity drop by over 20 dB if you're unlucky (as he was). That mistake literally killed off a local radio club, as few of the members were able to use the repeater following the addition of the T wrong cables. Thanks both Bob and Skipp for explaining that one odd-ball configuration that would crush the receivers with random cable lengths that just happen to hit the right sweet spot to do this. I suspect, that if someone saw a 20 dB loss while installing this setup, they'd at least STOP and start asking questions -- maybe they wouldn't get it that they'd hit this perfect storm combination -- maybe they'd think they had some kind of receiver failure when it suddenly was really deaf -- but I also doubt that *most* people would hit the problem. Would you agree with that assessment? (Skipp's comment that if there's a train wreck to be found, he'll be there... I know that feeling.) In this case, the owner wrote the poor sensitivity off to site noise. The club was based a good 30 miles from the repeater, but before it was transferred it worked just fine in the target area. After the system was modified/deafened, an article was written in the club newsletter explaining how the repeater was too far away from the club's user base for HTs to work there. Funny how after the repeater was sold off to yet another trustee, it suddenly began to receive well again. That's when I found out what was done that made it so deaf in the interim. Bob NO6B
Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
At 3/10/2010 11:16, you wrote: Actually, Gary, you are 180 degrees out. On a pass cavity, off frequency signals see a very high impedence path, an open not a short. If your version were true you could never use pass cans as a duplexer since both sets of cans together would show a short to EVERYTHING. I wish I had the VNA data from the pass cavities I measured several years ago when I built a 2-port UHF combiner using them, but they were measured while the pen plotter was connected to the VNA before I wrote a program to convert the Citifile output from the VNA to Excel spreadsheets, so the data was only saved on paper I have no idea where I would've stuffed the plots. But my best recollection is that at the reference plane of the cavities (front surface of the female N or SO-239 connector, they looked fairly close to an open, but not quite - maybe 10 to 15 degrees off of an open, on the inductive side. Bob NO6B
Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
At 3/9/2010 16:29, you wrote: Here's the idea. This is a remote RX site. The idea is to run something like a beefed up X500 dualbander at tower top, then 7/8 hardline 100 feet down to the receivers. Both receivers will have one or two bandpass cavities inline before the T. Would a duplexer be necessary in this case. Or could it be done with proper cable lengths and a T? Doesn't even need the special cable lengths It most certainly does. Try random length cables from the cavities to the T instead of 1/4 wavelength (like one local did several years ago) watch your sensitivity drop by over 20 dB if you're unlucky (as he was). That mistake literally killed off a local radio club, as few of the members were able to use the repeater following the addition of the T wrong cables. but there is a reason for doing everything and here comes questions 101. Will the receivers stay on one frequency as in a repeater receiver or do you need to move around each band a bit? If he's got bandpass cavities in front of the RXs already, they're very likely not frequency-agile. How much other RF is around? ... does the site have a lot of transmitters and are any of the high power monsters as in the case of paging or broadcast? If you don't have a lot of adjacent frequency operation going on there are two other options to consider. One is the Diamond or Comet type of band splitter, which actually would take the place of your T and be much better. That would be my choice, but if he's already got the cans, a pair of 1/4 wavelength cables will be much cheaper. I'd stay away from using a broadband isolated power divider (splitter), as you'll lose 3 dB in the split. The frequency-splitting options lose virtually no signal. Bob NO6B
Re: [Repeater-Builder] Dual receivers on one antenna for RX only site
At 3/9/2010 20:12, you wrote: OK, question... If you put a cable which is 1/4-wavelength at VHF between the T and the UHF cavity, it's 3/4-wavelength at UHF. Since any odd multiple of a quarter wavelength will invert the impedance, what will this really accomplish on the UHF cavity side? Doesn't matter at UHF, since the cavity looks like (hopefully something close to) 50 + j0 ohms @ UHF, so the cable length has no effect (other than plain ol' cable loss) @ UHF. At VHF, the short at the UHF cavity connector (I'll take Gary's word that it looks like a short off-resonance, though to be sure you'd want to put the can on a VNA to get the actual phase angle at the connector) needs to be transformed to an open at the T so it has no effect VHF. The short-to-open transformation @ VHF is accomplished with a 1/4 wavelength of coax @ VHF. The dual-band diplexers are usually high-pass/low-pass arrangements, and lose something like 0.2 dB while providing 40 dB or more isolation. Assuming you get a real one, and not something made with PIM-prne materials, would this not be a safer bet? It's true you wouldn't need to mess with cable lengths if a cross-band diplexer were used, but OTOH it would be another piece of hardware in the system that really isn't necessary, since the cavities are already there. Plus if you're really worried about PIM, you'd probably have to move up to something like a cross-band coupler from TX-RX, which IIRC runs over $300. Bob NO6B
Re: [Repeater-Builder] Someone still loves a Motrac - Low Band Even...
At 3/5/2010 15:32, you wrote: re: Someone still loves a Motrac - Low Band Even... Made me smile to think someone bid on the radio. It's already xtal'd up working on a popular ham freq., so that makes it worth something. Bob NO6B
Re: [Repeater-Builder] Re: Fw: FCC RO Involving the Amateur 70cm Band
At 3/4/2010 13:45, you wrote: It suffices to say there are lots of good answers, and none of them are the 440 band. And, there is obviously existing spectrum for these devices, so their waiver should have never been granted. As far as the eBay auction, there ARE legal users of these devices - US! (hams) I can see it now - Live from Dayton... the Hamvention Robot. For the price of a Recon Scout, I could've bought 2 10 kW AM broadcast transmitters at last year's Dayton. Or was it a 3 kW transmitter for $10k? Bob NO6B
RE: [Repeater-Builder] Re: Fw: FCC RO Involving the Amateur 70cm Band
At 3/4/2010 13:45, you wrote: Doesn't matter; the legal world is ruled by precedents. This sets an unhealthy one. And NTIA/Military has spoken up on the matter -- did you see the section in the order where the device would not be operated within so many miles of several AFBs, which are known to house PAVE-PAWS installations? Finally, someone actually read the RO! Actually, I believe it said no training exercises within 30 km of the AFBs. In actual scene use it can be used anywhere. Now, see the channel assignments for the analog video? Since the video carrier is 1.25 MHz above the bottom of each channel, we can predict where most of the energy is going to fall: 437.25, 443.25 431.25, in descending order of occupancy. If your input isn't near one of those frequencies, you're probably never going to hear from one. The real problem will be us interfering with the Scout RX. Bob NO6B
Re: [Repeater-Builder] Re: Hamtronics versus Commercial (Kenwood) Repeater Selection
At 3/3/2010 14:19, you wrote: skipp025 wrote: The more famous surplus commercial radio 224 MHz conversions replace the PA with a Hybrid RF Amplifier Module... wonder if they also include SWR Protection? In the case of the GE MASTR II, power control is done with a simple pot, and all SWR protection, leveling, etc. is bypassed/eliminated - at least with this interface board. Maybe someone has hacked the MASTR II PA to allow for the incorporation of its protection in a 220 conversion - but I have never saw it if it has been done. Kevin Custer Most RF power modules sold today are spec'd to withstand 20:1 VSWR. That's a lot of reflected power, probably more than what you'd ever see if your repeater antenna opened or shorted due to the feedline duplexer losses. Bob NO6B
Re: [Repeater-Builder] RBI-1 Problem
At 3/3/2010 13:08, you wrote: My RBI-1 was working. Now what ever command you ask it to doit jumps the frequency of the radio 15kc. Reset does not help. trying to even change the power setting only causes the RBI kenwood receiver to go up 15kc. Every command sent just compounds the display frequency by 15kc. When a reset is done it goes through its dance and looks ok there. Has anyone ever experienced this problem and know what the cure is??? Maybe a long shot, but check the modular connector that plugs into the RBI-1. Mine was bad, causing the radio to do weird things in general; a replacement from DHE fixed it. Try pushing the cable into the connector while controlling see if anything different happens. AFAIK there is no way that the data stream from the repeater controller could be corrupted in such a way so as to cause the problem you're having, so the problem is likely either in the RBI-1, radio cable, or radio. Bob NO6B
Re: [Repeater-Builder] Micor Stock Power Supplies
At 2/27/2010 09:56 AM, you wrote: I have been following the 9.6 Volt Micor Voltage information. One post indicated that if one were to replace the Stock MICOR Supply with a switcher and add the 9.6 Volt circuit, the monthly electric bill to run the repeater could be significantly reduced. Is this due to the fact that the switcher, in the standby mode, draws much less current and therefore cost less to operate or is it this combined with efficiently when the repeater is in operation. I have stock MICOR and MASTR II Supplies and would like your expertise on the merits of replacing them with one large switcher or a couple switchers. As always thanks in advance for your input and sharing your experiences with us. A local multi-band repeater system is having IMD problems, requested a CTCSS change to resolve one of them. After describing the sound of the low-level (~-70 dBc) spurs I'm seeing a few hundred kHz either side of the 440 output of the system, the owner told me that the IMD hitting his other inputs sounded the same. I asked if he was using a switching supply to power the system he said yes. I recommended that he replace it with a linear supply; I suspect that will solve all of his IMD problems. Will let you know... Bob NO6B
Re: [Repeater-Builder] Re: Can the 4th harmonic of 1250 AM keep UHF repeaters locked up?
At 2/23/2010 17:16, you wrote: Mark et al, Yes, this repeater is using the Motorola T1500 series bandpass cavities (two each for rx and tx). I've tried running rx and tx both duplex and seperate (borrowing a nearby antenna with permission). I can hear the interference underneath my signal when I'm about 2 miles away and monitoring my signal. When its strong enough, the PL encode of the repeater keeps it locked up until the modulation from the AM station overtakes the PL being looped (voice peak). Then the repeater drops since I have a tone panel in between and not continuous PL outbound. I have tried changing the receive frequency about 75Khz lower and the interference is not present (so a 4.925Mhz split), so that serves to prove to me that this indeed a mix. I can try adding an attenuator the next time I'm out at the site. The antenna is about 300 feet up and fed with 7/8 heliax, to a Polyphaser and then superflex to the duplexer. I've also tried without the Poly, but have the same result. I have some nice Mini-Circuit pads that should work in the receive side after the duplexer, but think the receiver is simply overloaded. The cause of your interference problem is not RX overload. It is as others have suggested: a mix occurring somewhere in the near field of the antenna. Pads may eventually mask the real source of the problem, once you've added enough to drop the signal below your RX's noise floor, but you'll end up with a deaf repeater. How far away were the separate TX RX antennas when you tried that? I'd think if they were far enough apart that you would lose the mix. OTOH if a tower joint is the source of the mix (likely since a lot of length is required to couple in the AM BC station), it might be all over the tower. A similar problem was partially cured here by spraying some conductive paint into all the tower joints. Each time it was done the interference would disappear for a few months, then return. Bob NO6B
Re: [Repeater-Builder] Bend an ICOM a little further
At 2/17/2010 16:33, you wrote: Also I should mention that the receiver should be set by looking at the LO frequency on either a service monitor or a frequency counter of known precision, Tuning it until it sounds best is not the way to go. The LO frequency for the MASTR-II VHF will be either + or - 11.2 MHz from the receive frequency depending on the whether high side injection was specified when ordering the crystal. My procedure for setting the RX freq.: 1. Tune LO chain (on MVPs Exec IIs the 1st mult. stage will pull the oscillator freq. a little, so have to do this before netting the xtal). 2. Set LO freq. per above. 3. Tune front-end. 4. Move sig. gen. freq. +/- to see if RX is centered. 5. If RX is not centered, tune IF for best SINAD. 6. Repeat step 4. If RX is still not centered, move LO freq. to center IF. Bob NO6B
[Repeater-Builder] WTB: 220 MHz pass cavity
A while back I posted a WTB for the above. A few people responded but unfortunately the e-mail chain on the one good prospect seems to have gotten lost. So once again I'm looking for a used 220 MHz pass cavity (not pass-notch, not window filter a la DCI). Thanks. Bob NO6B
[Repeater-Builder] WTB: 440 Yagi antenna
I'm looking for a used 5 to 11 element 440 Yagi. Need to have it by 2/18. Haven't found anything reasonable on eBay, eHam or at the local swap meets. Please reply direct to no6b at no6b dot com. Thanks. Bob NO6B
Re: [Repeater-Builder] TM-g707 power
At 2/6/2010 15:36, you wrote: I searched the files but did not see what I needed. Is there a pot/mod in the g707a to turn the med-power level up to 20-25watts or turn the hi-power setting down to 20-25 watts Have found nothing on the internet searching for mods fer this rig. Not sure just how warm the rig gets using it as a remote base. The fan helps I know, but 50 watts on hi-power is pretty much fer continous duty at times. Not sure about your last sentence regarding duty cycle, but if you want continuous duty I'd think you'd need an external cooling fan even at 25 watts. I use one as a remote base never bothered with a cooling fan or changing the built-in power settings. As a remote base the duty cycle is never more than 50% (same as when the radio is used locally). I also have the ability to remotely change the power level so if traffic on the repeater did cause it to transmit more than half the time I could turn it down to low power. Bob NO6B
RE: [Repeater-Builder] RFS TDE-7780A
At 2/6/2010 20:08, you wrote: Oh, forgot to mention. If you turn your unit upside-down, you should see rubber plugs near the fed ends of each resonator. You can fine-tweak the taps through these holes. It's pretty easy to break a wire, so I wouldn't recommend you go in there and start twistin' and tweakin' with any significant amount of force. Adjusting the distance of the tap wire (center conductor) from the resonator will have a small, but measurable, effect on insertion loss and return loss. 3MB JPEG of a disassembled PD633: http://www.broadsci.com/foo/IMG_6010.jpg Never completely disassembled one, so nice to see what's inside - thanks for posting the nice pic. 3MB JPEG showing what happens when you mis-tune or over-power one of these duplexers (capacitive loading slug and teflon insulator fried) - they are NOT very forgiving: http://www.broadsci.com/foo/IMG_6031.jpg Let me guess: this was removed from the resonator nearest to the TX port. I did this to one years ago, though the damage was not as dramatic. We were increasing the power beyond 50 watts saw something happen at about 80 watts, so we shut down took it out of service immediately. The teflon insulator had arced through the longer thin section looked a lot like the one in your picture, maybe not quite as much charring visible. Fortunately the tuning slug was not damaged. I ended up cleaning out the insulator the best I could swapping it with the one in the TX resonator closest to the antenna port. Most mobile duplexers are rated for 50 watts max. TX power. That rating is quite accurate. Bob NO6B
Re: [Repeater-Builder] Re: GLB
At 2/1/2010 14:25, you wrote: I built my own clown of the GLD ID board back in the 80's. It is still working. In my application, changing the state of the remote base selects a different ID with appropriate tail msg on the ID. I also have different speeds imbedded within the ID by ratioing the slower CW to that of the fastest. I can send someone the schematic if interested. My board is wire wrapped. :) Sounds like a good job for a PIC. K1EL already has a CW ID PIC (K-ID) for only $6. Unfortunately it lacks the timing needed for repeater IDing the output is square wave. I used one in one of my portapeaters along with Skipp's favorite IC (555 timer) a BPF to clean up the square wave. But a PIC should be able to handle the ID interval timing, a PIC with more outputs could generate an approximated sine wave. The mid- high-range PICs have built-in serial ports that would make user programming of the callsign, interval, tone freq., etc. easy. Bob NO6B
RE: [Repeater-Builder] Re: current state of our lightening struck repeater.
At 1/20/2010 21:40, you wrote: I thought I d better update the list on what was found. First off, the entire repeater was taken in to the shop for exhaustive testing. The can s were taken apart, inspected and cleaned. All that was visibly found was a little carbon. The two service monitors showed they were working ok. But, when placed back into service at the site, the transmit side leaked into the receiver side. It presented a crackling noise, like saran wrap being crushed. I don t know if the technicians tested the repeater at full power, ( 110 watts) during testing, but I think so. We did solve part of the problem. A fifth can was put into line, on the transmit side and by golly, it did the trick. The repeater is sounding better than before the strike. This actually points to an antenna system problem. I know in an earlier post that you said you checked the antenna system it was good. However, unless you took a different repeater/duplexer to the site connected it to your antenna there was no desense, you don't know that it's good. The VSWR can check out fine, but it can still be totally unusable for duplex service as a result of lightning damage. I have at least 3 such antenna systems that fit that description. The pass cavity you added is removing more phase noise from the TX. Less phase noise available to convert to your input by the nonlinearity in your antenna system means less desense. I also used this method to cure a desense problem in an antenna system that couldn't be accessed at the time. Bob NO6B
RE: [Repeater-Builder] Re: Split Site Via Coax Cables Wire?
At 1/17/2010 01:13 PM, you wrote: Greg, Trying to combine both vertical and horizontal separation will not help; the horizontal will completely swamp the vertical. As soon as you move the transmit antenna out from directly under the receive antenna, the isolation decreases dramatically. Even a few feet of horizontal displacement will have a major influence. For example, CommShop recommends 86 dB isolation for your system with a 20 watt transmitter and a 0.25 uV receiver. That isolation can be achieved with about 190 feet of vertical separation, one antenna directly above and in line with the other, or about 16,200 feet of horizontal separation. There's a 2 meter repeater about 3000' from my home running ~25 watts. I just checked to see if there's any measurable desense caused by that repeater to my FT-8500 radio 600 kHz away. I do see ~ 1 dB - barely noticeable. The desense is in the form of front-end compression, so any decent RX like a Mastr II or Micor wouldn't be bothered at all. Adding a modest amount of pass cavity filtering to the TX RX can dramatically reduce the amount of antenna separation needed. My very first repeater used 2 antennas separated 50' horizontally with a single pass cavity on the TX. The transceiver was all tube the RX antenna was a beam nulled into the TX antenna. I had to retune the TX about once every 2 weeks keep the sharp null of the Yagi on the TX antenna, but when this was done there was no desense. Bob NO6B
Re: [Repeater-Builder] RE: follow up on lightening strike last spring
At 1/16/2010 15:12, you wrote: I know its been a long time since I first posed the question on what might be causing the noise we were experiencing after being hit by lightening. After many trips to the Technical shop for testing, we replaced the repeater ( was a vertex 5000, now a Icom ur2000) and are in process of checking out controllers. The duplexers were my big worry. And yes, it would seem that concern wasn't unfounded. We started experiencing a degradation on the receive side of the repeater and then, a leakage from the cans. We had the duplexers checked out with two different service monitors and found nothing! The technician who works on duplexers took ours apart and found only a little bit of carbon, but that was it. they checked out ok. We put them back into service and the noise was there making communications impossible. We are now going to replace them with a 6 configuration instead of the four we have been using. My question to the list is, besides the noise factor and crackling noise, is there any other methode of discovering if the can's are bad or not? Yes, I did and have been losing sleep over this one. We don't get much lightning out here in SoCal (now having said that we're due for a week of very nasty weather, so maybe time to catch up?), but of the few incidents I'm aware of, the lightning damaged either the antenna or feedline in such a way that the antenna system continued to perform well w.r.t. VSWR gain, but considerable noise was generated whenever the antenna system was driven with RF. My advise is to try a different antenna/feedline at the site see if your desense goes away. Bob NO6B
Re: [Repeater-Builder] Motorola T1504A Duplexer Lock Nut
At 1/10/2010 06:34, you wrote: Hi, Does any one in the groups have on of these in their junk box that they don't need? I'm missing a couple of those myself for the pass version of those cavities. I would be interested if there's a standard/plentiful source. Bob NO6B
RE: [Repeater-Builder] Repeater Rebuild Project Input
At 1/9/2010 20:49, you wrote: The GP9 I used on the repeaters was on a hill that was about 900 feet elevation. The problems didn't seem to make any difference regardless if the user was 2 miles out or 10 miles out. Then either you had lots of foliage absorption (lots of trees in Oregon), which affects 440 more than 2 meters, or you just got a bad antenna. The fact that you changed sites along with antennas may have changed the absorption issue. I have 4 GP9s in service then all work very well on 440. The one I have on the 5200' mountain significantly outperforms a DB-420, which is now my backup TX antenna. Bob NO6B
RE: [Repeater-Builder] Motorola T1504A Duplexer Lock Nut
At 1/10/2010 08:28, you wrote: Try here: http://www.mcmaster.com/#hex-locknuts/=5bcw46 Click on Flex-top Expanding Lock Nuts McMaster-Carr - of course! Thanks Jeff. I do have one here with the lock nut: it's a 1/2-20 thread. The best McMaster match to the original (same width height) is 94830A550: $7.47 each. Bob NO6B
RE: [Repeater-Builder] Motorola T1504A Duplexer Lock Nut
At 1/10/2010 08:55, you wrote: Ouch. Maybe a regular nylon lock nut would work acceptably well and be a little cheaper? Isn't the outer sleeve (the one that the lock nut threads onto) slotted? If so, will it tighten up enough to keep the shaft from being turned if you just use a regular nut? The outer 1/2-20 threaded sleeve is slotted, but doesn't appear to be tapered. I don't have one handy to try it, but I think a plain 1/2-20 nut would just thread down the sleeve without compressing it, which creates the locking action. Hard to tell if a nylon lock nut would generate enough pressure to provide an adequate lock of the tuning rod; I think not. Sal's idea of using small hose clamps is starting to look good ;) Bob NO6B
RE: [Repeater-Builder] Repeater Rebuild Project Input
At 1/8/2010 23:39, you wrote: I used a Comet GP9 for about 2 years on a 444 Mhz repeater, then connected a 2 meter repeater to it. The 2 meter system performed FAR better than the UHF system. Both repeaters were nearly identical in performance otherwise, the GP9 simply performed much better on 2 meters. The GP9 does have significant nulls below the horizon on 440, so if your repeater was on a mountain you were trying to access it close-in, it would appear to perform much worse than on 2 meters, where the gain is lower. The only GP9 I have on a mountain is used for TX only, so I don't care about the close-in coverage. At 15 miles away the main lobe hits the ground. Bob NO6B
RE: [Repeater-Builder] Repeater Rebuild Project Input
At 1/8/2010 16:22, you wrote: Depending on what coverage you are looking to expect, will help you choose the proper gain antenna. A higher gain antenna is not always a good choice and can cause more problems and poor coverage then you would expect nearby the repeater. Andrew said he wants to maximize the coverage the antenna will only be 20 feet up. Clearly this calls for a higher gain antenna. I recommend the Comet GP9. It has 11 dBi gain on 440 MHz, on the horizon, also works well on 2 meters in the event you want to add a remote base. Bob NO6B
Re: [Repeater-Builder] something altogether different
At 1/6/2010 10:56, you wrote: On Jan 6, 2010, at 9:31 AM, Jeff DePolo wrote: Enough reminiscing, I probably sound like one of those OF's on 80m that talks about their gout, their pension, and what orifice they're having scoped this week, back to real work. This comedian pretty well covers it... and his rotary dial phone comments near the beginning are hilarious... You hated people with zeros in their phone numbers. http://www.youtube.com/watch?v=rOtEQB-9tvk I recently had FiOS service installed, which means my wired phones plug into an ONT installed here. Wondering if the box supported pulse service not owning a rotary phone (I'm not an antique collector), I picked up my touchtone phone hand-pulsed the hook to dial my wife's cell phone. It worked. Bob NO6B
Re: [Repeater-Builder] Re: Mastr II mods and parts
At 1/3/2010 21:54, you wrote: For connection between duplexer and radios I like 1/4 Superflex, but RG400 or RG142 is also great. To a duplex antenna for short runs those same cables could be used, keeping loss figures in mind. Otherwise appropriately sized Heliax or equivalent cables should be used. RG214 is the best choice for hardline-to-antenna jumpers. I also use is for the duplexer-to-radio cables unless I need more flexibility, in which case I use RG223. Bob NO6B
Re: [Repeater-Builder] Mastr II mods and parts
At 1/3/2010 11:11, you wrote: Yes, it was resolved at a lot of commercial sites by not allowing it to be used ;-) For me, the resolution came from a Times Microwave sales rep. who admitted that LMR-400 is not appropriate for duplex use. Having said that, you can get away with using it in situations such as temporary/portable repeater installations provided the connectors are installed properly the feedline is not used near the antenna, where RF can couple to the outer braided shield. In no circumstances would I ever use it at a shared comm. site. Usually after a bit of time, the cable will start to become a source of noise as the two dissimilar metals start to react with each other. There are many documented cases of this problem. Search this group's messages and you'll see this has been discussed over and over. It comes up about every other week. BTW, they don't need to be dissemilar metals. I once confirmed a 100% copper braided RG-213 jumper as a PIM source. I only use silver-plated braided coax beyond the duplexer from now on. Bob NO6B
Re: [Repeater-Builder] Mastr II mods and parts
At 1/3/2010 12:16, you wrote: Yes, I agree. Various plated connectors can also be a problem. Unfortunately most antenna manufacturers don't use silver plated coax in their pigtails and harnesses. This is probably why all Cushcraft 4-pole antennas eventually cause desense to the systems they're connected to. I have one in use for a TX-only link. Someday I'll take it down replace that harness with RG142 or RG214. Bob NO6B
Re: [Repeater-Builder] Cold MVP
At 1/3/2010 04:37 PM, you wrote: Well speaking of cold we have a MVP remote RX which is a duplexed 2 meter rx to 70 cm tx that is in a elevator room on top of a 15 story building and that room is largly at near ambient temperature and now with the cold seems slow to come up. The elements were temp compensated etc and I really don't think that it is coming up off frequency. If anything it seems it there at extremely low power but not confirmed at this point. The site is in a secure site so is hard to get access to for testing. What thoughts does anyone have on this. If you have the power turned down on it (such as for driving an external RFPA), the power level will drop with colder ambient temperature, but will eventually come back up if the TX is kept on for a while. I have 2 on a mountaintop site (0 to 100 °F ambient): one duplex link one repeater. The repeater radio runs at full power I never have any power issues with it. The link is set to around 3-4 watts, when it gets well below freezing it takes a couple of seconds for the TX to make enough power to establish the link. Bob NO6B
