Re: [Repeater-Builder] UHF Micor (mobile) spur - conclusion
BTW: Which sticks are you in? I'm in EC Indiana, with an SA that I could loan. A kind offer, thanks. Different sticks though... I'm in central Maine, geographically speaking (that's northern Maine to most of the world :-) Paul Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] UHF Micor (mobile) spur
Title: RE: [Repeater-Builder] UHF Micor (mobile) spur Paul, A spur is ususally produced by multiplier circuitry in the transmitter. I would retune the exciter and pay special attention to the position of the slugs prior to retuning. Second you might just have a defective exciter board. Most exciters filter the multiplication stages so that spurious responses and conversion gain loss are minimised if you an get another exciter you can compare the two! neil Ve2boa-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com]On Behalf Of Paul Kelley Sent: Thursday, June 30, 2005 3:07 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Micor (mobile) spur Aarggh! I've pulled out most of my hair on this one! To revisit something I asked about several months ago... I'm still having a problem with my UHF Micor mobile converted to repeater. It is a T34RTA3000AA with power set at 20 watts. It is on 444.000 (T), 449.000 (R) and is producing a spur at 444.910. The spur is clean, stable, and has good modulation, sounds identical to the main carrier. I have retuned the exciter filter per the book several times. No change. I swapped the KXN1024A channel element for one on a different frequency (443.750T/448.750R) and still had a spur 910 kHz above my carrier freq. Finally I tested both channel elements in a stock (unmodified) Micor and STILL have a spur 910 kHz above the carrier frequency! I lack equipment to accurately measure the spur power level, but this spur is some 80 or so dB below the carrier level, perhaps a bit more. The manual specifies spurious and harmonics below 85 dB so this MAY be within spec. but why would it always spur 910 kHz above carrier freq.? This is an unacceptable level as it can be heard up to 5 miles from the repeater on line of sight paths (and this is causing a problem for some people). What am I missing? Is this normal behavior for a UHF Micor? I have juggled some numbers around and can't see why this would always be 910 kHz above the carrier freq. Thought I had a bad Micor until I found identical results in the second one... Any ideas? Should I forget about asking why and just throw cavities on the thing until I knock the spur down enough? Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/ YAHOO! GROUPS LINKS Visit your group "Repeater-Builder" on the web. To unsubscribe from this group, send an email to:[EMAIL PROTECTED] Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
[Repeater-Builder] UHF Micor (mobile) spur - conclusion
Joe was right. I feel like an idiot! But this experience served as a very effective reminder... I doubt I'll be making this mistake again any time soon. :-) Service monitors and spectrum analyzers don't live out here in the sticks. So when I had reports of a spur I dragged out my receivers to use as test equipment. I made sure I had several diverse receivers (instead of relying on one) but failed to check the IF schemes to be sure they were really diverse. It turns out all of them use a 455 kHz second IF with low side injection. I did find one receiver with a 450 kHz IF... and the spur magically moved 10 kHz. Oops! So it turns out to be the best kind of problem: someone else's. I'm not sure what we're going to do now... at least one person will be adversely affected unless I change repeater frequencies (AGAIN - long story) or he gets a different radio. At least now I can get these Micors off my test bench! There's other stuff in the queue waiting for bench time. Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur - conclusion
So it turns out to be the best kind of problem: someone else's. I'm not sure what we're going to do now... at least one person will be adversely affected unless I change repeater frequencies (AGAIN - long story) or he gets a different radio. At least now I can get these Micors off my test bench! There's other stuff in the queue waiting for bench time. I can't see any reason for you to change frequencies. This is a weakness of his radio. A directional antenna at his site would probably help. Another thing you could try, is a notch filter, but I don't know if you'll be able to get one that narrow. When he's shopping for radios, that would be something to remember. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur - conclusion
Service monitors and spectrum analyzers don't live out here in the sticks. BTW: Which sticks are you in? I'm in EC Indiana, with an SA that I could loan. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
So, no one here has ever run into this before? Really??! I found and tested a third radio... same problem. To restate what the problem is: Micor mobile UHF T34... when running in the ham band transmit low / receive high they are spurring 910 kHz above the transmit freq. I don't know what would happen if the frequencies were reversed. 443.750T 448.750R spur at 444.660 444.000T 449.000R spur at 444.910 It's not a power supply problem. The spur is generated low level, not in the PA (it's somewhere before or at the exciter mixer, Q305). It's not the offset oscillator. No amount of tuning or de-tuning various stages has any affect on the spur. Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
Paul, Have you tried using a different instrument to view this spur? Some spectrum analyzers and service monitors create an artifact of the viewed signal, due to some unintentional internal mixing. When three different radios exhibit the same oddball symptom, I'd suspect my test equipment or possibly the hookup arrangement. 73, Eric Lemmon WB6FLY Paul Kelley wrote: So, no one here has ever run into this before? Really??! I found and tested a third radio... same problem. To restate what the problem is: Micor mobile UHF T34... when running in the ham band transmit low / receive high they are spurring 910 kHz above the transmit freq. I don't know what would happen if the frequencies were reversed. 443.750T 448.750R spur at 444.660 444.000T 449.000R spur at 444.910 It's not a power supply problem. The spur is generated low level, not in the PA (it's somewhere before or at the exciter mixer, Q305). It's not the offset oscillator. No amount of tuning or de-tuning various stages has any effect on the spur. Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
Paul 910 Kc is twice the 455 Kc IF. Possibly there is a clue here. Motorola had problems with spurs in the Metrum VHF ham transceiver. It also used one crystal for both transmit and receive. I guess that this is a good data point as to why mobiles should not be used as repeaters. The repeater and base station is a complete redesign and uses separate crystals for transmit and receive. Probably they saw the problem and made the intelligent decision to keep the spurs at ground level in the mobiles and use a clean transmitter for base stations and repeaters. This is an observation from someone that made a decision a long time ago that mobiles were not designed for repeater service. Hope you can solve the spur problem. Probably related to the transmitter/receiver offset and will probably require a redesign to get rid of the spur. 73 Glenn WB4UIV At 10:39 AM 07/02/05, you wrote: So, no one here has ever run into this before? Really??! I found and tested a third radio... same problem. To restate what the problem is: Micor mobile UHF T34... when running in the ham band transmit low / receive high they are spurring 910 kHz above the transmit freq. I don't know what would happen if the frequencies were reversed. 443.750T 448.750R spur at 444.660 444.000T 449.000R spur at 444.910 It's not a power supply problem. The spur is generated low level, not in the PA (it's somewhere before or at the exciter mixer, Q305). It's not the offset oscillator. No amount of tuning or de-tuning various stages has any affect on the spur. Paul N1BUG Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
At 10:39 AM 7/2/2005 -0400, you wrote: So, no one here has ever run into this before? Really??! To restate what the problem is: Micor mobile UHF T34... when running in the ham band transmit low / receive high they are spurring 910 kHz above the transmit freq. I don't know what would happen if the frequencies were reversed. ---My first reaction is to ask..how are you driving the xmtr, audio wise? Did you bypass the limiter/filtering? Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html We offer complete Kenwood TKR repeater packages! AH6LE/R - IRLP Node 3000 http://www.irlp.net Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
Eric, Thanks for the reminder never to trust a single instrument too much. This spur is verifiable though. It can be heard on the air when the Micors are running into an antenna, up to at least 5 miles away if it is a true line of sight path and there is some antenna gain at both ends. And this has been verified with more than one receiver/antenna/location. Paul On Saturday 02 July 2005 10:54 am, Eric Lemmon wrote: Paul, Have you tried using a different instrument to view this spur? Some spectrum analyzers and service monitors create an artifact of the viewed signal, due to some unintentional internal mixing. When three different radios exhibit the same oddball symptom, I'd suspect my test equipment or possibly the hookup arrangement. 73, Eric Lemmon WB6FLY Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
Thanks Glenn. When I first noticed the 910 kHz relationship, 455 IF was the first thing that popped into my mind... until I realized the Micor doesn't have a 455 kHz IF. Darn, another good theory ruined... Since I have 3 similar radios exhibiting exactly the same problem I am thinking this may be an inherent design vs. application problem. Motorola never intended these radios to transmit below the receive frequency, nor were they intended for use below 450 MHz. But if it is, I was hoping others would step forward and verify that. Surely I couldn't be the first to discover it. If I could verify it's the nature of the beast, at least I would know I'm not going to cure it. Paul On Saturday 02 July 2005 10:59 am, Glenn Little WB4UIV wrote: Paul 910 Kc is twice the 455 Kc IF. Possibly there is a clue here. Motorola had problems with spurs in the Metrum VHF ham transceiver. It also used one crystal for both transmit and receive. I guess that this is a good data point as to why mobiles should not be used as repeaters. The repeater and base station is a complete redesign and uses separate crystals for transmit and receive. Probably they saw the problem and made the intelligent decision to keep the spurs at ground level in the mobiles and use a clean transmitter for base stations and repeaters. This is an observation from someone that made a decision a long time ago that mobiles were not designed for repeater service. Hope you can solve the spur problem. Probably related to the transmitter/receiver offset and will probably require a redesign to get rid of the spur. 73 Glenn WB4UIV Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
On Saturday 02 July 2005 11:57 am, Ken Arck wrote: ---My first reaction is to ask..how are you driving the xmtr, audio wise? Did you bypass the limiter/filtering? Thanks Ken. The spur is there even without audio. But no, I'm not bypassing anything... controller audio is fed to the microphone input. (Also, I found the same spur on an unmodified Micor with control head / microphone) Paul Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] UHF Micor (mobile) spur
Are you sure it isn't something caused by your service monitor? Have you tried a different one, or is there anything else common to all three radios? Richard, N7TGB -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of Paul Kelley Sent: Saturday, July 02, 2005 7:39 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] UHF Micor (mobile) spur So, no one here has ever run into this before? Really??! I found and tested a third radio... same problem. To restate what the problem is: Micor mobile UHF T34... when running in the ham band transmit low / receive high they are spurring 910 kHz above the transmit freq. I don't know what would happen if the frequencies were reversed. 443.750T 448.750R spur at 444.660 444.000T 449.000R spur at 444.910 It's not a power supply problem. The spur is generated low level, not in the PA (it's somewhere before or at the exciter mixer, Q305). It's not the offset oscillator. No amount of tuning or de-tuning various stages has any affect on the spur. Paul N1BUG Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
At 11:33 AM 7/2/2005, Paul Kelley wrote: Thanks Glenn. When I first noticed the 910 kHz relationship, 455 IF was the first thing that popped into my mind... until I realized the Micor doesn't have a 455 kHz IF. Darn, another good theory ruined... Since I have 3 similar radios exhibiting exactly the same problem I am thinking this may be an inherent design vs. application problem. Motorola never intended these radios to transmit below the receive frequency, nor were they intended for use below 450 MHz. But if it is, I was hoping others would step forward and verify that. Surely I couldn't be the first to discover it. If I could verify it's the nature of the beast, at least I would know I'm not going to cure it. Have you tried readjusting the PLL?? I saw something similar-ish in a Kenwood transmitter, that output nicely on 146.73 and on 120.1 Granted that's a lot farther than your problem, but it turned out that the PLL adjustment had drifted significantly in the first 6 months of use, and it was unlocking. The radio didn't detect this and shut down like it should, it just sat there hopping between frequencies. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
--- Glenn Little WB4UIV [EMAIL PROTECTED] wrote: Paul 910 Kc is twice the 455 Kc IF. Possibly there is a clue here. Motorola had problems with spurs in the Metrum VHF ham transceiver. It also used one crystal for both transmit and receive. I guess that this is a good data point as to why mobiles should not be used as repeaters. The repeater and base station is a complete redesign and uses separate crystals for transmit and receive. Probably they saw the problem and made the intelligent decision to keep the spurs at ground level in the mobiles and use a clean transmitter for base stations and repeaters. I have used lots of Micor mobiles as repeaters and never seen this problem. How far down is the spur from the TX carrier? The Micor does not use a 455KHz IF. It is a single conversion RX with IF at 11.7MHz. My thought is that the 910KHz is too co-incidental. Look at the RX that you are using to see if it has a 455 KHz IF, if it does, it's probably not a spur, but an image of the 455 IF. Follow me for a moment. If you have a standard 10.7/455 IF system in the radio you are using to see this spur, you will have an oscillator at 10.245 (the same would occur with any high IF, be it 21.4 or 31.2, etc; the oscillator will be 455KHz removed from the high IF. 10.7 is only used as an example). This means that a signal coming through the 10.7 (or whatever) filter that is 910KHz lower will also be demodulated at the 455KHz IF (10.245-.455= 9.79). The only attenuation will be whatever the high IF filter has at that freq, maybe around 60-80 dB or so. Now, if you are listening on your radio at 444.910, an incoming signal on this freq will produce a 10.7 MHz signal, which is what is desired. But a signal coming into the RX at 444.00 (your RPT TX) will produce an output on 9.79MHz, which will also be heard by your 455 demod, although at a much lower level. Joe Yahoo! Sports Rekindle the Rivalries. Sign up for Fantasy Football http://football.fantasysports.yahoo.com Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
Comments threaded in... On Saturday 02 July 2005 01:19 pm, Joe Montierth wrote: I have used lots of Micor mobiles as repeaters and never seen this problem. Thanks Joe. How far down is the spur from the TX carrier? About 80 dB give or take a bit. My thought is that the 910KHz is too co-incidental. Look at the RX that you are using to see if it has a 455 KHz IF, if it does, it's probably not a spur, but an image of the 455 IF. Uh-oh. This could turn out to be very embarrassing. I am aware of receiver images and have run into issues with that in the past... however, somehow managed to develop selective amnesia while working on the current problem! I just checked all the radios I've been using to monitor this spur in-house and all *do* have a 455 kHz IF. I will have to check the others which may take a day or two. Let me also see if I can find a receiver which does *not* use a 455 kHz IF to check it with. I will let you all know if I have made a really big blunder... Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
I just checked all the radios I've been using to monitor this spur in-house and all *do* have a 455 kHz IF. I will have to check the others which may take a day or two. Let me also see if I can find a receiver which does *not* use a 455 kHz IF to check it with. The second best kind of problem is one that isn't really a problem. The best kind, is someone else's problem :) Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur (more test results)
It sounds like you are on the right track! Keep going!! A few years ago I had a local ham tell me my UHF repeater was producing a spur on his UHF output. He made a fuss that I was not running good gear, or adequite filtering. I assured him that I was fine had checked it out with my equipment. He offered to come to my repeater site with a spectrum analyzer mentioned several times that since he was an engineer (working for Fujitsu) he would like to trouble shoot the problem at my location would help repair. I declined his request. (Apparently he did not realize that I also am an engineer working in FM broadcast) He then requested I turn off my repeater, I refused. He then found out that my repeater transmitter was a GE Mastr Pro suggested I upgrade to a solid state transmitter, claiming that an old tube PA was likely the cause of the problem (I refused) He then made a fuss with the repeater coordination coucil, of which we were BOTH board members. Eventually, it came down to a local ham (WA7ABU) member of the coordination board inspecting BOTH our repeater sites. The inspector found a mix that was occuring in HIS (the complaining party's) location!! (Which was a solid state PA deck!!) Obviously, this has noting to do with the subject but is a fun story. -- Original Message -- Received: Fri, 01 Jul 2005 06:54:32 AM CDT From: Paul Kelley [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] UHF Micor (mobile) spur (more test results) I just spent another night poking around in this thing. Sniffing around the transmitter with a receiver and very small probe antenna I am reasonably certain the spur is present at Q305 (exciter mixer) and all subsequent stages. Using a general coverage receiver the fundamental output of the channel element (19.195833 MHz) seems free of spurs. I realize the third harmonic of the channel element is selected by the filter but I have no receiver covering that range. Similarly, the 16.7 MHz out of the offset oscillator seems OK. There are some very weak (more than -100 dB) spurs above 16.7 but it is absolutely quiet at 15.790 which is what would be required to cause my +910 kHz spur. So I suspect a problem in either the exciter mixer (Q305) or somewhere in the injection multipliers (Q101, 102, 103) on the receiver RF IF board). No amount of tuning or detuning these stages eliminates it. It still seems odd that I have two Micors with an identical spur problem. Any thoughts on what to try next? Paul N1BUG Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur (more test results)
Obviously, this has noting to do with the subject but is a fun story. I've got one that I'm trying to track down.. A local 2M machine, on 146.730, is having a problem we call the horrible noise. I've never heard anything like it, and I've had no success at recording it. It sounds like some sort of a feedback loop, in that I think that I can hear 'reverb like effects in the sound. It happens in wet weather, and there have been a bunch of theories put forward, but nothing makes sense. At one point, it was blamed on a repeater I now own, but we disproved that by taking it off the air entirely, while the horrible noise continued. The latest theory is that it is related to the replacement of some capacitors in the final amp of the kenwood repeater, but I'm skeptical. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
At 12:07 PM 6/30/05, you wrote: Aarggh! I've pulled out most of my hair on this one! To revisit something I asked about several months ago... I'm still having a problem with my UHF Micor mobile converted to repeater. It is a T34RTA3000AA with power set at 20 watts. It is on 444.000 (T), 449.000 (R) and is producing a spur at 444.910. The spur is clean, stable, and has good modulation, sounds identical to the main carrier. I have retuned the exciter filter per the book several times. No change. One trick that I have used... the far end of the preselector tune broader than the near end. I've found that I get better performance if I do the tuning then turn it around and tune it again. This lets the old far end adjustments become the near end for the second pass through the procedure. I swapped the KXN1024A channel element for one on a different frequency (443.750T/448.750R) and still had a spur 910 kHz above my carrier freq. Finally I tested both channel elements in a stock (unmodified) Micor and STILL have a spur 910 kHz above the carrier frequency! I lack equipment to accurately measure the spur power level, but this spur is some 80 or so dB below the carrier level, perhaps a bit more. The manual specifies spurious and harmonics below 85 dB so this MAY be within spec. but why would it always spur 910 kHz above carrier freq.? This is an unacceptable level as it can be heard up to 5 miles from the repeater on line of sight paths (and this is causing a problem for some people). What am I missing? Is this normal behavior for a UHF Micor? I have juggled some numbers around and can't see why this would always be 910 kHz above the carrier freq. Thought I had a bad Micor until I found identical results in the second one... Any ideas? Should I forget about asking why and just throw cavities on the thing until I knock the spur down enough? Put a test receiver on the spur frequency, and if the test receiver desenses due to the true frequency then add a cavity in line to knock down the true frequency. Then go poking around in the exciter and see if you can isolate it to one stage. I'll bet that you find a multiplier that a slight touch in the adjustment kills the spur. I had a Moto 63MHT Motrac that had an intermittent spur on 147.775 when the radio was on 146.220 ... I put it on an analyzer and found that rocking one of the multiplier slugs just a hair cleaned it right up. On the test set the clean spot was still inside the top part of the peak... i.e. you'd never see a difference between dirty and clean on the test set. Like WB6VYZ used to say a picture tube is worth 20db of clean any day. Only frequently it's more than 20db. Mike WA6ILQ Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
See below ... Mike Morris WA6ILQ wrote: At 12:07 PM 6/30/05, you wrote: Aarggh! I've pulled out most of my hair on this one! To revisit something I asked about several months ago... I'm still having a problem with my UHF Micor mobile converted to repeater. It is a T34RTA3000AA with power set at 20 watts. It is on 444.000 (T), 449.000 (R) and is producing a spur at 444.910. The spur is clean, stable, and has good modulation, sounds identical to the main carrier. I have retuned the exciter filter per the book several times. No change. One trick that I have used... the far end of the preselector tune broader than the near end. I've found that I get better performance if I do the tuning then turn it around and tune it again. This lets the old far end adjustments become the near end for the second pass through the procedure. I swapped the KXN1024A channel element for one on a different frequency (443.750T/448.750R) and still had a spur 910 kHz above my carrier freq. Finally I tested both channel elements in a stock (unmodified) Micor and STILL have a spur 910 kHz above the carrier frequency! I lack equipment to accurately measure the spur power level, but this spur is some 80 or so dB below the carrier level, perhaps a bit more. The manual specifies spurious and harmonics below 85 dB so this MAY be within spec. but why would it always spur 910 kHz above carrier freq.? This is an unacceptable level as it can be heard up to 5 miles from the repeater on line of sight paths (and this is causing a problem for some people). What am I missing? Is this normal behavior for a UHF Micor? I have juggled some numbers around and can't see why this would always be 910 kHz above the carrier freq. Thought I had a bad Micor until I found identical results in the second one... Any ideas? Should I forget about asking why and just throw cavities on the thing until I knock the spur down enough? Put a test receiver on the spur frequency, and if the test receiver desenses due to the true frequency then add a cavity in line to knock down the true frequency. Then go poking around in the exciter and see if you can isolate it to one stage. I'll bet that you find a multiplier that a slight touch in the adjustment kills the spur. I had a Moto 63MHT Motrac that had an intermittent spur on 147.775 when the radio was on 146.220 ... I put it on an analyzer and found that rocking one of the multiplier slugs just a hair cleaned it right up. On the test set the clean spot was still inside the top part of the peak... i.e. you'd never see a difference between dirty and clean on the test set. Could be the transmitter is going into self oscillation when the adjustment is made. Another good reason to bring your transmitters (and receivers) into the frequency range you want to use them on. You have a Motorola T63MHT - factory in 150.8 - 162 MHz? You want to use it at 146.46 MHz? You really need to pad down the exciter board to get there. Ditto the Micor exciter board in the same frequency range. Neil - WA6KLA Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur
On Friday 01 July 2005 04:56 am, Mike Morris WA6ILQ wrote: One trick that I have used... the far end of the preselector tune broader than the near end. I've found that I get better performance if I do the tuning then turn it around and tune it again. This lets the old far end adjustments become the near end for the second pass through the procedure. I have read that somewhere (or quite possibly I remember you having said it before!) I did try this a couple of times. Put a test receiver on the spur frequency, and if the test receiver desenses due to the true frequency then add a cavity in line to knock down the true frequency. Then go poking around in the exciter and see if you can isolate it to one stage. I'll bet that you find a multiplier that a slight touch in the adjustment kills the spur. I have done that. Unfortunately I can tune each stage as far as I want (up to the point - in either direction - that it kills the whole transmitter) and it makes no real change in the spur. Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur (more test results)
I just spent another night poking around in this thing. Sniffing around the transmitter with a receiver and very small probe antenna I am reasonably certain the spur is present at Q305 (exciter mixer) and all subsequent stages. Using a general coverage receiver the fundamental output of the channel element (19.195833 MHz) seems free of spurs. I realize the third harmonic of the channel element is selected by the filter but I have no receiver covering that range. Similarly, the 16.7 MHz out of the offset oscillator seems OK. There are some very weak (more than -100 dB) spurs above 16.7 but it is absolutely quiet at 15.790 which is what would be required to cause my +910 kHz spur. So I suspect a problem in either the exciter mixer (Q305) or somewhere in the injection multipliers (Q101, 102, 103) on the receiver RF IF board). No amount of tuning or detuning these stages eliminates it. It still seems odd that I have two Micors with an identical spur problem. Any thoughts on what to try next? Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur (more test results)
On Friday 01 July 2005 08:43 am, Dave VanHorn wrote: Any possibility that it's coming from the power supply, and not actually the amplifier at all? Do you get it when running from a battery? Good thought. I tried 3 different power supplies and finally a battery. There is definitely something funny going on in the Micors. Paul Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Micor (mobile) spur (more test results)
At 08:03 AM 7/1/2005, Paul Kelley wrote: On Friday 01 July 2005 08:43 am, Dave VanHorn wrote: Any possibility that it's coming from the power supply, and not actually the amplifier at all? Do you get it when running from a battery? Good thought. I tried 3 different power supplies and finally a battery. There is definitely something funny going on in the Micors. Ok, glad to rule that out. . I've seen badly designed or broken switchers with significant HF noise on the output, and even linear supplies can do this. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
[Repeater-Builder] UHF Micor (mobile) spur
Aarggh! I've pulled out most of my hair on this one! To revisit something I asked about several months ago... I'm still having a problem with my UHF Micor mobile converted to repeater. It is a T34RTA3000AA with power set at 20 watts. It is on 444.000 (T), 449.000 (R) and is producing a spur at 444.910. The spur is clean, stable, and has good modulation, sounds identical to the main carrier. I have retuned the exciter filter per the book several times. No change. I swapped the KXN1024A channel element for one on a different frequency (443.750T/448.750R) and still had a spur 910 kHz above my carrier freq. Finally I tested both channel elements in a stock (unmodified) Micor and STILL have a spur 910 kHz above the carrier frequency! I lack equipment to accurately measure the spur power level, but this spur is some 80 or so dB below the carrier level, perhaps a bit more. The manual specifies spurious and harmonics below 85 dB so this MAY be within spec. but why would it always spur 910 kHz above carrier freq.? This is an unacceptable level as it can be heard up to 5 miles from the repeater on line of sight paths (and this is causing a problem for some people). What am I missing? Is this normal behavior for a UHF Micor? I have juggled some numbers around and can't see why this would always be 910 kHz above the carrier freq. Thought I had a bad Micor until I found identical results in the second one... Any ideas? Should I forget about asking why and just throw cavities on the thing until I knock the spur down enough? Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
