Re: [Repeater-Builder] Re: tone panel deal of the moment
I'm not sure I understand what the problem shipping overseas is. I've done a fair amount of eBay trading myself, and it's never been more than paying the postage for whatever the destination is, and a single page form declaring what the item is, and it's value. And many times, I haven't even been required to fill out a declaration form. I do virtually all my shipping via the internet, with pick up from my front porch. Are there some countries that trigger a more difficult process? I've shipped to Australia, New Zealand, South Africa, South America, Israel, and all over Europe including some of the former Soviet block countries and it's been no problem at all. In buying stuff, I'm receiving items from Hong Kong and Israel faster than I get it from across the state. Mel - WA6JBD Hi Marcus, If you became friends with some of the US Based people on the group... over time building a rapport, some of us do on occasion offer to help. The problem is... many of times I've helped someone outside the US Deal with Ebay Shipments it's like a large water dam bursts and they flood me with excessive shipping work ... There are companies that can help deal with outside US Shipping. ... and there are some countries that seem to go out of their way to make shipping packages a real pain in the pazzoo. The global market place isn't always so easy to deal with. cheers, s.
Re: [Repeater-Builder] Just curious... Microwave frequencies
A properly designed microwave path is designed around a reliability specification, such as 99.%, which translates to about 30 seconds of outage per year. Frequency, weather, terrain, and equipment parameters are all taken into account. I've designed many microwave links that meet or exceed that specification. It's really a matter of getting what you pay for, and working for a customer that takes it seriously enough to spend the money required. Properly designed, a microwave link can exceed the reliability of just about any other transmission medium. Mel - WA6JBD So in a nutshell, microwave is a band of precision and pinpoint accuracy? Common sense that people shouldnt use wood for anything outside that demands long-term stability. Not only do the elements cause warping, but also prone to termites, etc. Wow! Thanks for all the good input! John Hymes La Rue Communications 10 S. Aurora Street Stockton, CA 95202 http://tinyurl.com/2dtngmn
Re: [Repeater-Builder] Identify Please
I probably could, but I never know what to charge for stuff like that. Mel - WA6JBD Mel - Looks like you could have a side job re-working these things for hams. Chuck WB2EDV
RE: [Repeater-Builder] Identify Please
A lot of us amateur microwavers retune circulators with external magnets. With a handful of otherwise useless circulators, one could tear one apart, recover the magnets, and apply them to the outside of the case of the unit to be tuned. A network analyzer helps, so you can watch what's happening in both directions, but that's not a requirement. You can tune them up or down quite a bit, depending on the orientation of the external magnets. Once you find a combination that works, the external magnets get glued to the circulator case with epoxy. Mel - WA6JBD Don't get your hopes too high, because most dual isolators can only be tuned 3% or so away from the frequency they were manufactured to operate at.
RE: [Repeater-Builder] Identify Please
Hi Eric, The steel cases are not an impediment to the magnetic field, at least not enough to make retuning impossible. Microwave type circulators are built in a similar fashion, just smaller, and the technique is well known among those of us who play in the microwave region. Just to give an idea of the magnitude of change that's possible, 1.8 GHz circulators can be moved up to 2304, and I have moved 11.7 GHz circulators down to 10368 MHz. I haven't specifically attempted to move 870 MHz circulators up to 928, but I see no reason why this couldn't at least be attempted if someone was so inclined. If someone wants to attempt it, you can either dissect an unwanted circulator, or maybe better yet, use some of those extremely powerful rare earth magnets. I buy 'em by the handful at the county fairs for cheap, just to have them around for such purpose. The network analyzer makes it seem stupidly simple, but a SA/TG would work nearly as well. Just remember to check it both ways before you apply the glue. Mel - WA6JBD Mel, I have heard that done, and if it works, great. However, the remanufacturing of typical VHF and UHF circulators almost always involves machining or replacement of the ferrite components. Since the Celwave circulators that started this thread have steel cases, I wonder how an external magnet can affect the internal magnetic field. I certainly agree that a network analyzer is best suited for circulator tuning. 73, Eric Lemmon WB6FLY
Re: [Repeater-Builder] Re: Connect Controller to EM Interface
Most 4WEM muxes have at least two signaling configurations, usually described as Type 1 and Type 5. More elaborate cards may also have Type's 2-4. They describe various combinations of battery or ground on M, to idle or activate, and battery, open, or ground on the E lead when idle or active. What you want to look for is the configuration for type 5 signalling. This is battery on the M lead (-24 or -48) that gets pulled to ground to send M lead. The E lead floats open until active, then pulls to ground when active. That combination is the easiest to deal with, but still requires care on the M lead. An opto isolator is the made-to-order solution. Mel - WA6JBD
Re: [Repeater-Builder] HP 8924C
The 60 watt option is a nice to have but not at all necessary. Mine is the
standard 3 watt version, so I use a 150 watt 40 DB attenuator (eBay). The nice
thing about the 8924C is that you can can compensate for the external
attenuator in both transmit and receive modes, so that the measurements read
correctly, without operator intervention.
I'm not sure what other options there are besides the 1.9 GHz adapter, which
you obviously won't be needing. They default to CDMA digital modes, but it's
easy enough to get it to power up in analog modes.
Mel - WA6JBD
#yiv524921269 p {margin:0;}
Looking for advise on a HP 8924C
What Options needed for normal 2 way work.
Who knows who is selling these reputations etc
Any help will be appreciated.
Thanks in advance
Ralph, W7HSG
Re: [Repeater-Builder] Re: Rolling Pipe Sound
I recently located a very similar problem on a T-band public safety system, only in this case, it was two transmitters in a 28 channel 800 MHz trunker that were exactly 3 MHz apart that added that critical component to the mix. The end result was that every t-band repeater at that site would add it's own transmitter to the mix component, and would cause a feedback howl that could best be described as a rolling pipe. Adding to the confusion in finding it, it would hit the various t-band channels in what seemed like a random fashion. It wasn't until later that I realized what was happening is, the combination of activity on any particular T-band receiver would cause it's associated transmitter to activate (obviously!), and if the two 800 MHz transmitters in question were active at that time, the howling noise would start up. If the other repeaters were quiet, they would STAY quiet. Cross coding the PL's between your own transmitter and receiver can help mask the symptom, because your own transmitter may end up providing the PL (or DPL, as the case may be) needed to open the receiver. Depending on where the mix is actually taking place, you may or may not be able to locate it and actually fix it. In that case, masking it becomes the necessary solution. In my case, the mix is pervasive throughout the site - including miles of rusty chain link fence. Removing the Angle Linear preamp eliminated the symptom, but only because, since the mix product is a pretty low level, it's making the receivers sensitive enough to hear what's always there. Mel - WA6JBD --- On Mon, 12/7/09, larynl2 lar...@hotmail.com wrote: From: larynl2 lar...@hotmail.com Subject: [Repeater-Builder] Re: Rolling Pipe Sound To: Repeater-Builder@yahoogroups.com Date: Monday, December 7, 2009, 7:49 PM Do you have two FM stations in your area that are separated by 600 kc.? That will definitely do exactly what you describe. We had it on our repeater. I caught in one of your posts that your transmitter needs to be on for the problem to appear, so that's intermod causing your interference, not just a random carrier coming from a router or whatever device. The problem here was caused by an FM station on 89.9 about a mile away, and another one on 89.3 roughly six miles away, plus our transmitter on 147.06. A+B-C=D 147.06 + 89.9 - 89.3 = 147.66. The thing to watch for with FM broadcast intermod is the wide bandwidth of the intermod product. There was no interference until BOTH stations were quiet -- no modulation. Obviously, the instances of both being quiet simultaneously are quite random in length and occurrence, depending on the program material of each. I tracked the location of the mixing with the aid of a spectrum analyzer, which turned out to be safety cables threaded through the turnbuckles. Laryn K8TVZ Yahoo! Groups Links repeater-builder-fullfeatu...@yahoogroups.com
Re: [Repeater-Builder] Re: pre-amp placement
You might need to add a several DB attenuator between the pre amp and the receiver to keep from over driving the front end. Not if you use a good receiver, or not use a preamp with too much gain. Bob NO6B What defines too much gain can vary wildly. One trick I learned in building transverters for the microwave bands, and one I now apply to VHF/UHF preamps is to check the overall noise figure of the system as a whole. You'd be surprised at what just a few db too much gain can do, and it doesn't necessarily show up with a quick sensitivity check. A preamp can be placed in front of a receiver and, yeah, now the receiver is more sensitive. But if it's a .5 DB NF preamp, and you're not careful, your system noise figure can end up going from, say, 6 db for the barefoot receiver, to 4 db with the preamp - an improvement to be sure, but not nearly as good as the preamp may be capable of. If that preamp is driving the receiver front end even just a little bit into compression, you've lost a lot of potential. Even with a good receiver. Carefully balancing preamp gain with attenuation on the output can be extremely useful. Not everyone has a noise figure meter, though, and measuring NF on an FM receiver is a pain in the neck. A sinadder can be used to the same effect, even if the actual noise figure isn't known. It can be interesting to observe insertion of a few db of pad between the preamp and a receiver, and watch the sinad sensitivity of a receiver improve by a few tenths of a microvolt.
Re: [Repeater-Builder] Re: Motorola Spectra 900's
Well, maybe I've actually managed to do something different... I've been adding a 1 pf chip cap (0603) between the oval shaped pad in the filter, and the edge of the filter sectiont. One cap for each section. This lowers the frequency down below 900, and then I use a dremmel with a sharp bit to walk the filter back up in frequency. This is all done while watching a sweep of the filter on a network analyzer. I've not really attempted to narrow the BW of the filter at all, just shift it down some. As to the VCO, that's where the conductive ink comes into play. Just dab some in through the slotted window, no need to remove the cover. The microstrip resonator needs to be about a 1/4 longer. The conductive ink pens work just fine for that. I have a web page up on converting the 406-433 spectras to 440 that has some useful pictures on how I go about retuning the filters. Just add the 1 pf cap to the process, and it's otherwise the same. http://mysite.verizon.net/res8teuc/Range1spectra/Range1Spectraver1.1.htm Maybe that, and my comments above, will prove helpful until I can put up a similar article on the moving the 800 and 900 Spectras down. My next project? See if I can get a VHF Spectra to receive on 220. Mel - WA6JBD Well, you have me curious also, maybe I took the dark path for tuning the front end filters. I had to resort to silver paint (not cheap), a grinder, and a little blood and guts to tune those puppies. What's your story.. . bill w4oo
Re: [Repeater-Builder] Motorola Spectra 900's
Hi Bill, I'm quite curious as to what you ran into when you attempted this. I have one working, and as far as the number of steps taken to make it operable on 902, it was pretty simple. The only thing I left out in my short list was bringing COR out. Did I miss something, or did I just get lucky? As to it's suitability for high RF environments, probably no more or no less than any other mobile grade receiver. I wouldn't put one on a hilltop without good external filtering - especially in the 900 band. They're not an MSF, but then, that's not the point. They're cheap, they're readily available, and they can be made to work, probably better than a Maxtrac. I've also converted 800 radios to receive on the input side of the 800 band (806-828) with the exact same procedure - hack software, tune VCO lower, retune filter. There seems to be enough interest to warrant writing this up, so I'll get going on that. Mel - WA6JBD Been there done that seven years ago...it is a liiittle more than the three items listed that need to be done For the NUC RX idea, I have been thinking about doing a rx for that purpose, however, my concern is, will all that work have pay dirt... If some one can show the 902 rx front end is truly usable in high rf environment, I will work with them to...git-er-done... I currently have two 900 spectras in a sales catalog bag with wide duplexer and controller to operate on any one of the eighty channels 902-903 and 927-928. All that's needed is twelve volts and antenna. . Bill w4oo jawjabill-- bellsouth- net
