RE: RE: [Repeater-Builder] Harmoinic products
Next time you are at the site plug 150.6 into a handheld and see if you hear it. That number is the result of 904 / 6 and it the transmitter is leaky enough you just might be able to t-hunt it. Or make up a 900mhz beam and plug it into a handheld scanner that you wrap in foil that is grounded to the antenna BNC shroud. Poke some holes in the speaker grille so you can hear it and off you go... Mike WA6ILq At 06:03 PM 07/19/08, you wrote: >The only fly in the ointment is moving the >RX. We donât know WHERE this noise is coming >from... so if he moves, he may move CLOSER to >rather than further away from the source... > >I think a 904 notch on the RX may be a workable solution. > >Thanks, Ron. > >Mark - N9WYS > >-Original Message- >From: Repeater-Builder@yahoogroups.com On Behalf Of Ron Wright > >Mark, > >At say 140 MHz 1.4 MHz is a long way, but at 900 >it is 1/6th the distance. RF works in >percentages. So the wide TX is really very close to your receive. > >The TX being 100 kHz wide might mean it is >digital and this can be very wide with lots of >signal MHz, but down 80 db, from its center >freq. However, still this low level being so close could cause you problems. > >If a problem of overload then a cavity on your >receiver would help and might solve your >problem. It would give you protection from the >stron 904 tx power. Also a cavity with a notch >at the 904 TX freq might help doing the same. > >However, if this is from the 904 wideband noise >then this means its wide band noise is on your >receiver frequency. The solution is a notch >cavity on the 904 TX itself which you might not >have the previdledge of doing. They might not >let you touch their equipment. In this case the >solution would be distance and seperation you >from him. Also moving the rcv freq as far as you can might solve this problem. > >Too bad you could not turn off the 904 tx for >short period of time to see if this is the >problem, but since very close in freq I would >suspect it. However, they may be perfectly >legal, just physics of radio. I've known of >users at a site go around and just start >unplugging others systems to see if they caused >a problem. Some of these people are not longer allowed on the site. > >73, ron, n9ee/r > > > > > > >Yahoo! Groups Links > > >
RE: RE: [Repeater-Builder] Harmoinic products
The only fly in the ointment is moving the RX. We don’t know WHERE this noise is coming from... so if he moves, he may move CLOSER to rather than further away from the source... I think a 904 notch on the RX may be a workable solution. Thanks, Ron. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Ron Wright Mark, At say 140 MHz 1.4 MHz is a long way, but at 900 it is 1/6th the distance. RF works in percentages. So the wide TX is really very close to your receive. The TX being 100 kHz wide might mean it is digital and this can be very wide with lots of signal MHz, but down 80 db, from its center freq. However, still this low level being so close could cause you problems. If a problem of overload then a cavity on your receiver would help and might solve your problem. It would give you protection from the stron 904 tx power. Also a cavity with a notch at the 904 TX freq might help doing the same. However, if this is from the 904 wideband noise then this means its wide band noise is on your receiver frequency. The solution is a notch cavity on the 904 TX itself which you might not have the previdledge of doing. They might not let you touch their equipment. In this case the solution would be distance and seperation you from him. Also moving the rcv freq as far as you can might solve this problem. Too bad you could not turn off the 904 tx for short period of time to see if this is the problem, but since very close in freq I would suspect it. However, they may be perfectly legal, just physics of radio. I've known of users at a site go around and just start unplugging others systems to see if they caused a problem. Some of these people are not longer allowed on the site. 73, ron, n9ee/r
RE: [Repeater-Builder] Harmoinic products
Hi Ron, and thanks for the reply. First off, the 904 signal is always there - and about 100kHz wide... A >>WIDE<< signal. Second, his machine is on 927.600/902.600. As you can see, the signal is 2 MHz up and still clobbering his receiver. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Ron Wright Mark, Usually desense is not harmonic or intermod related. It is caused by wide band noise from a transmitter. For harmonic it is just 2,3,4, etc times a frequency. For intermod it is nF1 +/- mF2 = your receive freq. In either case the problem will be there only when the offending txs are keyed up. Is the 904 tx keyed all the time? If not then you can determine if coming from it. Listen when it is unkeyed for the problem. If it is keyed all the time then I would put your friends tx on a dummy load with the remaining parts of the repeater, duplexer & antenna & receiver, connected. This can aid in determining if your tx is part of the problem. What are the freqs of your friends repeater? 73, ron, n9ee/r >From: Mark > >OK, it’s been a while since I’ve had to compute this, so if my question seems >a bit “trivial” or elementary in nature I apologize in advance. Yes, my math >is rusty. ;-) > >Having said that, I’m trying to assist another ham with a desense problem he >is experiencing on his 900 MHz ham-band repeater. He is experiencing about >10dB of receiver desense because of a signal centered at 904 MHz. He tells me >this is verified with a Spectrum Analyzer and it is about 100 kHz wide... I >take him at his word. The site he is at has no other 900 MHz at all, but it >is a commercial site with other “stuff”, including various government and >commercial frequencies, in use. > >What I am trying to do is see if we can figure out whether this might be a >spur, or maybe some harmonic, that is being generated as the result of a mix >of other products there. > >Can anyone provide me with the math necessary to try to determine whether this >is a harmonic, using very rudimentary figures? (For example, I want to be able >to use basic freqs like 150 MHz, 450 MHz, etc, to at least get us in the ball >park.) Once we get close, then we can fine-tune the freq combinations to see >if it is a mix product. Or if anyone has any ideas, I’m certainly open to >suggestions. > >Thanks, >Mark – N9WYS > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. Yahoo! Groups Links No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.5.1/1560 - Release Date: 7/18/2008 6:47 AM
Re: [Repeater-Builder] Harmoinic products
Mark, Usually desense is not harmonic or intermod related. It is caused by wide band noise from a transmitter. For harmonic it is just 2,3,4, etc times a frequency. For intermod it is nF1 +/- mF2 = your receive freq. In either case the problem will be there only when the offending txs are keyed up. Is the 904 tx keyed all the time? If not then you can determine if coming from it. Listen when it is unkeyed for the problem. If it is keyed all the time then I would put your friends tx on a dummy load with the remaining parts of the repeater, duplexer & antenna & receiver, connected. This can aid in determining if your tx is part of the problem. What are the freqs of your friends repeater? 73, ron, n9ee/r >From: Mark <[EMAIL PROTECTED]> >Date: 2008/07/17 Thu PM 03:11:13 EDT >To: Repeater-Builder@yahoogroups.com, [EMAIL PROTECTED] >Subject: [Repeater-Builder] Harmoinic products > > >OK, it’s been a while since I’ve had to computethis, so if my question seems a >bit “trivial” or elementary innature I apologize in advance. Yes, my math is >rusty. ;-) > >Having said that, I’m trying to assist another hamwith a desense problem he is >experiencing on his 900 MHz ham-band repeater. He is experiencing about 10dB >of receiver desense because of a signal centeredat 904 MHz. He tells me this >is verified with a Spectrum Analyzer and itis about 100 kHz wide… I take him >at his word. The site he isat has no other 900 MHz at all, but it is a >commercial site with other “stuff”,including various government and commercial >frequencies, in use. > >What I am trying to do is see if we can figure out whetherthis might be a >spur, or some maybe harmonic, that is being generated as theresult of a mix of >other products there. > >Can anyone provide me with the math necessary to try todetermine whether this >is a harmonic, using very rudimentary figures? (For example, I want to be able >to use basic freqs like 150 MHz, 450 MHz, etc,to at least get us in the ball >park.) Once we get close, then we canfine-tune the freq combinations to see >if it is a mix product. Or ifanyone has any ideas, I’m certainly open to >suggestions. > >Thanks, >Mark – N9WYS > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
[Repeater-Builder] Harmoinic products
OK, it's been a while since I've had to compute this, so if my question seems a bit "trivial" or elementary in nature I apologize in advance. Yes, my math is rusty. ;-) Having said that, I'm trying to assist another ham with a desense problem he is experiencing on his 900 MHz ham-band repeater. He is experiencing about 10dB of receiver desense because of a signal centered at 904 MHz. He tells me this is verified with a Spectrum Analyzer and it is about 100 kHz wide. I take him at his word. The site he is at has no other 900 MHz at all, but it is a commercial site with other "stuff", including various government and commercial frequencies, in use. What I am trying to do is see if we can figure out whether this might be a spur, or some maybe harmonic, that is being generated as the result of a mix of other products there. Can anyone provide me with the math necessary to try to determine whether this is a harmonic, using very rudimentary figures? (For example, I want to be able to use basic freqs like 150 MHz, 450 MHz, etc, to at least get us in the ball park.) Once we get close, then we can fine-tune the freq combinations to see if it is a mix product. Or if anyone has any ideas, I'm certainly open to suggestions. Thanks, Mark - N9WYS
