Re: [dstar_digital] Re: Inside Chassis coax - lossy
Ernie, I see your reasoning for 144.9-145. However, would not a repeater put at 145.300 say have an input on 144.900, possible the output of another repeater. I think I am not following the plan for which this change is being done. I thought all repeaters were going to the new split of 400, but maybe only for 144.9-145.1 and 400 kHz makes sense. If all repeaters did then in all 3 MHz of 2 meters all of the freq combinations could be used. Guess the few on 146.52 would not be happy although this one could be singled out as not allowed. I think better to put national simplex on 145.52. With all the rigs sold in last 20 years this would not be a problem. I remember in Indianapolis, IN, in the late 70s 146.94 had been used for simplex for years and few wanted it given up for a repeater. Think this has changed. The same could be done today. Going to 400 or 500 kHz the existing repeaters could change only with their input moving. 500 kHz would allow full use and keep some outputs off some inputs. It does look like a good change for getting more pairs for DStar, much better than calling it digital and using 145.5-145.8 which some started to do. The FCC stopped this. 73, ron, n9ee/r From: Ernest Kapphahn [EMAIL PROTECTED] Date: 2008/06/30 Mon AM 10:01:32 EDT To: dstar_digital@yahoogroups.com Subject: [dstar_digital] Re: Inside Chassis coax - lossy Ron; The digital band plan being tested currently puts the D-Star outputs between 144.9 and 145.1 and the inputs 400 kHz down. This keeps everything in the spectrum designated by the FCC for repeater use. Since alternate input channels are inputs for analog repeaters, only 9 new channels resulted. At 500 kHz spacing, we would have lost the 144.9 to 145 channels as their inputs would have been outside the repeater allocation. The 9 channels should accommodate 15 or 16 systems in Northern Calif. by judicious channel co-ordination. We have 6 systems on this plan currently. It is necessary to use a 6 can duplexer to make the 400 kHz split play. The results of some testing using a reference antenna are in the tech log at www.w6dhs.org . Ernie W6KAP --- In dstar_digital@yahoogroups.com, Ron Wright [EMAIL PROTECTED] wrote: Ernie, I've noticed talk of 400 kHz splits on 2 meters. Wonder why not 500 kHz. Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: [dstar_digital] Re: Inside Chassis coax - lossy
Lee: I think most repeater operators would be appalled to see what gets through their BP/BR duplexers. While they're called that, most are not good bandpass filters. Also, at many sites the repeater receiver is capable of dealing with the signals it sees, as long as the owner hasn't put some 22 dB preamp on it. As always, what you use depends on the application, and the notion of quality is relative. Chuck - N8DNX [ED - A Wacom 678 UHF duplexer does a good job of passing VHF paging signals right on thru - hence a band pass cavity - 2 loop job - before any preamp, and a MONO band antenna] -Original Message- From: ve7fet [EMAIL PROTECTED] Sent: Friday, June 27, 2008 5:56 PM To: dstar_digital@yahoogroups.com Subject: [dstar_digital] Re: Inside Chassis coax - lossy Hah, lets not go down that rat hole again. ;) I wasn't referring to the power handling capability of the mobile duplexers, as I was more trying to make the point of how broad their pass is. With an easily overloaded RX (think a mobile masquerading as a repeater receiver... ala D-STAR and others), in a typical high RF repeater site, a mobile duplexer is inviting trouble. I have a bunch of old Harris radios, with said mobile duplexers built in, and they work great in our high-speed packet backbone, with links using between 5 and 30W. BUT, they also have a manually tuned pre-selector on the front end to keep all the junk out. Cheers! Lee
Re: [dstar_digital] Re: Inside Chassis coax - lossy
Lee, Very well said. So many look at the duplexer as allowing a tx and rx on same feedline, but a good one also provides for some front end and tx noise filtering. I think the repeaters from ICOM, Kenwood, Yeasu and other DC to light programmable repeaters rely on this filtering. I do like and use the mobile duplexers, but one needs to know what they provide and what they do not. 73, ron, n9ee/r Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: Re: [dstar_digital] Re: Inside Chassis coax - lossy
They appear to be custom rigs. Housed in an aluminum enclosure (the same as the ID-1, less the powder coating) I have photographs of the RP4000V, RP2D, RP2V, RP2C. The same basic configuration is used. No TX components in the Rx Units. Custom boards for the application, though all quite similar. Doesn’t look at all like my ID-800, or my friends 2820. They appear to be like modified ID-1s, even the UHF unit. Perhaps after field day I can put some of these images up on the net. -Greg Zenger, N2GZ From: dstar_digital@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Saturday, June 28, 2008 10:58 AM To: dstar_digital@yahoogroups.com Subject: Re: Re: [dstar_digital] Re: Inside Chassis coax - lossy Nate, and all, Nate we knew you were coming from a hecked day. You usually don't go this way and know you've used mobile duplexers. The cabling is, as you said, the problem. Do you or anyone know what rigs ICOM uses in the repeater. Looks like a pair of mobiles put in a box, big box. Wonder what mobiles. Appears they have been modified for rcv and xmt (fan removed on I think the receiver heat sink). I understand there is a different controller/CPU that puts out data and rigs are controlled with raw data with no rcvr DStar demod. I wonder what are the specs of these rigs. I bet they are one of the mod'd ICOM mobiles. 73, ron, n9ee/r Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. [Non-text portions of this message have been removed]
Re: Re: [dstar_digital] Re: Inside Chassis coax - lossy
Mobile duplexers work very well. Repeaters have been built for years with the mobile duplexers inside the repeater enclosure with very good performance. If replacing the cables and moving outside I would think the cables were the problem and not where the duplexer was. Since you replaced the cables this is probably the solution and not the moving the duplexer outside. This tells me the repeater had poor cables to start with. 73, ron, n9ee/r From: Nate Duehr [EMAIL PROTECTED] Date: 2008/06/27 Fri AM 01:59:59 EDT To: dstar_digital@yahoogroups.com Subject: Re: [dstar_digital] Re: Inside Chassis coax - lossy On Jun 26, 2008, at 1:15 PM, Mike wrote: Also the UK 70cms module came with a ready pre-tuned duplexer that was mounted inside the case, as soon as we moved it outside of the case and fed it direct with decent coax the difference was unbelievable in sensitivity.
Re: [dstar_digital] Re: Inside Chassis coax - lossy
Lee: Sorry, but just because I'm feeling contrary today I have to ask. Didn't we just have a discussion about how you don't need to run much power for a repeater? Most of the mobile duplexers are fine for 25-50 Watts. I have one repeater that runs 15 W out with about 7 at the antenna and it covers out to some 60 miles for mobiles. It's a real repeater--I think. Chuck - N8DNX ve7fet wrote: That's a pretty broad statement that needs a qualifier... they work well in the proper application. Most UHF mobile duplexers, are just simple notch types that will offer you some isolation from your own transmitter, but not from anything or anyone else. Even then, you only get about 65dB of isolation... so you better be using low power. They work well for portable repeaters and duplex subscriber units... real repeaters use real duplexers. Lee
Re: [dstar_digital] Re: Inside Chassis coax - lossy
Charles Scott wrote: Not exactly the kind of comments I'd expect from you. I didn't notice which band it was for this unit, but from 440 up the little mobile duplexers can be pretty small and work well for low-power applications. Also, why are you worried about shielding? I believe the radios in the repeater chassis have their own shielding, and what leakage would you expect from one of the small mobile duplexers? Considering the possible problems that have been reported with the jumpers inside the case, it may have been an improvement! Sorry, was in a horribly bad mood last night. Big escalated issue at work. Still going on, but now we're down to Nate will work all weekend to make sure the problem is fixed. instead of conference calls with angry C-Level execs. (I wouldn't mind so much if I hadn't audited these configurations and then someone copied the wrong one to all of the production systems instead. Sigh. 40,000 phone lines worth of teleconferencing equipment misbehaving all over the country is not a good way to spend three days, in case anyone's thinking about a career in telecom technical support. It's also a great way to miss participating in Field Day, for the most part. Sigh. Oh well, I'll get a bunch of OT, and maybe that'll pay for an ID-1. GRIN! There's always a silver lining, right? Heh heh.) I shouldn't have hit send on that one. But since we're here, I'll be nicer... and explain better... Don't know what you have against the smaller mobile duplexers, but I've used them in a number of applications and they work just fine--good rejection (for these power levels), not much more loss that a full sized duplexer, and certainly no leakage. They just don't handle much power. Real shielding using grounding strips, etc... between sections is what a real repeater (GE) has. Or individual RF shielded boxes for each section if they're on the same board (Moto). These mobile in a box repeaters are problematic at high RF (commercial) sites. They're okay but it sure would be nice if Icom would spend an additional $100 on sheet metal work to block the two sides from each other. As far as the mobile duplexer... I guess they're okay, I just don't build with them. 1/4 wave on UHF just isn't that physically big, and fits fine in most cabinets. VHF, is a pain, and most mobile duplexers won't handle our 600 KHz typical (now California is doing 400 KHz) splits very well. Sorry, Nate, just don't see a real problem with this on the surface as long as it was physically well done. Understand. It's just MUCH easier to over-do-it a bit on the duplexer and cabling, etc. Plus... all these reports that cruddy cabling may have been used internally really chaps me badly for a box that costs $2000 or more U.S. -- these things should be brick you-know-what-houses for that price. How much margin in Costs of Goods Sold (COGS) is there, in packaging two $500 mobiles in a metal box? A lot. Not including RD, there's probably at least $1000 profit in these boxes. (Because the mobiles don't cost Icom $500/ea to put in there, anyway.) I very much looking forward to seeing the rumored other repeaters that people are working on. Keeping one of these things alive on a high-mountain site complete with trips to investigate problems is a $100 round-trip issue every time it happens at today's fuel costs. While this might argue that it's a good idea to replace these cables, etc... now... when it's cheap... it bugs me to no end that Icom isn't just upgrading them in later versions of the repeater. Adding proper TX to RX shielding (a metal wall between the two rigs with fingerstock on top, as a bare minimum?) etc, is too easy to ignore. It's a bolt-in fix that can't cost more than $15/repeater, including development costs to pay an engineer to draw it on a CAD program. Others will eventually fill the void Icom has in their repeater engineering skill-set... I was just grumpy that someone stuffed a mobile duplexer inside too... in a box that already has reported leakage, and other problems. Think RF can't get through that 4 hole where the fan is, for example? That's not shielded. The repeater RF packaging is a joke. It'll get better. Either Icom will step up, or someone will knock them off the perch, but it'll get better... I'll hold out hope for that, anyway. Nate WY0X
Re: RE: [dstar_digital] Re: Inside Chassis coax - lossy
This loss is about .11 db/ft, little more than RG58. If one used RG223 (double shielded RG58) the loss would be about the same. Going to RG214 loss would be .05 db/ft, an improvement. All this is at 400 MHz. At 400 MHz the .11db loss would be .63 watts from 25 watts. I don't think much improvement would be realized if replaced. Also not sure all the other specs of the cable; double shielded, silver solder, etc? This would also be factors I would consider. I do like the idea of removing the cable and replacing a single cable from each rig long enough to get to the duplexer, but to simply replace the 10 cable with another would not be of much concern as loss goes. If desense problem then this is another issue. 73, ron, n9ee/r
Re: [dstar_digital] Re: Inside Chassis coax - lossy
I agree On Thu, Jun 26, 2008 at 11:14 AM, Daron Wilson [EMAIL PROTECTED] wrote: We don't worry about such stuff in commercial applications. it is part of the link budget. .15 db on a splice in our work it is closer to being treated as 0.01 db...does not have a effect on operation. (unless you have a bad cable assembly, then in which case it is under warranty send it back) It is a small amount indeed. In a closed system where you have a link budget, it is relatively easy to compensate for loss and have a budget. You can increase amplifier gain, shorten coax runs, decrease coax loss, etc. In an open system such as a repeater, we don't have the luxury of being able to control what happens after the antenna. So, the more you can squeeze out of the system, the more usable it is (generally). While .15 is not much, many of us are interested in making the system as sensitive as we can within reason. So if you pick up a few little things at .15 and .25 or so, pretty soon you have a small gain. I would be more concerned about desense between the TX and RX with that coax than I might be about the small loss. 73 Please TRIM your replies or set your email program not to include the original message in reply unless needed for clarity. ThanksYahoo! Groups Links -- Thanks in Advance Bob Brown In-Building RF Design, Sprint-Nextel Custom Radio Communications Ltd. 816-561-4100 816-561-4148 Fax [EMAIL PROTECTED] NOTICE OF CONFIDENTIALITY: This material is intended for the use of the individual to whom it is addressed and may contain information that is privileged, proprietary, confidential, and exempt from disclosure. If you are not the intended recipient, you are notified that dissemination, distribution or copying of the communication is strictly prohibited. If you have received this communication in error, please contact the sender immediately via e-mail and destroy this message accordingly. -- The wireless telegraph is not difficult to understand. The ordinary telegraph is like a very long cat. You pull the tail in New York, and it meows in Los Angeles. The wireless is the same, only without the cat. Albert Einstein [Non-text portions of this message have been removed]
