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A lot of people tend to forget that EVERY transmitter has sideband noise. Regardless of the actual transmitted mode, there will be noise on either side of the carrier. In an FM signal, this noise extends into the squelch range of receivers on adjacent channels. When Texas was considering 15 k vs 20k splits in the 80s, I did testing with Micor receivers on the bench and proved that 20 kilohertz was far superior to 15 spacing. The squelch was not affected at 20 kilohertz even with strong signals but at 15 it would cause issues big time along with desense of the desired channel.
Testing with a Spectrum repeater that was local to me, I could get 15 kHz off with a dead carrier w/no modulation, several miles away with a 30 watt mobile and squelch the receiver up on noisy signals. The receiver in the repeater was an SCR200 which used the typical Motorola MC3357 IF chip and had 15 kilohertz filters in it! Same tests at 20 caused no ill effects. Not everybody runs high-end RF gear on a repeater. My testing was part of the reason why Texas went 20 kilohertz back in the 1980s. And I'm damn glad we did.
I even had Louisiana vote twice to go 20 kilohertz when I served on the board of directors of the Louisiana council. But unfortunately some die-hard idiots in New Orleans refused to move and the frequency coordinator gave up trying to change the state. Right now it's a mix of 20 and 15 across Louisiana. Maybe one day they'll join the 21st century.. But we're talking Louisiana here .... Almost as bad as Mississippi ?
I'm still waiting for a decent national band plan on 6m. The current plan is based on 50+ year-old radio technology! Really? When the ARRL took a poll back in the '90s, the results showed that majority wanted to stay the 1MHz split or go to the -1.7 WWARA plan... But the representatives from California and SCRRBA shoved that stupid 500 kilohertz outdated plan down the VRAC's throat.. I had a heated phone conversation with the West Gulf director about it and he was upset about it as well. But he said it was a political move and nobody wanted to argue against it. Well, that's BS! It's time 6M FM got into the 21st century as well.. I bet a lot of you don't even realize why 52.525 is such an oddball channel! If you do then you've been around as long as I have? ?
Chris WB5ITT?
What might follow to your comments, Neil, is that as far as additional transmitter bandwith added by the PL component I think it is not really the additional say +- 0.7KHz, but more like just the PL frequency say +_0.15 KHz. To back that up, once a fellow ham and I did a crude over the air test using a Micor PM modulated transmitter with and without PL. We were about 40 miles apart and he was hearing us with about 50 % noise and his squelch was set such that for every 10 times I said a loud "five", his receiver would squelch out on my voice peak 3 out of 10 times. That did not vary with or without PL. Ever since then I set peak dev on the initiatiing mobile, base or portable to 4.8 KHz assuming perfect deviation symmetry with less than 100cps frequency drift, and then disregard the 0.7 KHz PL deviation where the service monitor would read +_5.5 KHz (unless it was set up for only sensing 300-3000cps. With these settings maximum range is achieved, with just a slight occasional increase in distortion over +-3KHz dev on voice? peaks(how a lot of receivers seem to be rated when measuring audio distortion).
John W1GPO
What next?
In Burt's discussion, Bob Dengler, N06B, said:? Also, the audio has to have a flat response (aside from the usual 6 dB/octave pre-emphasis).? ?Any extra slope that favors the high frequencies or hard clipping will shift the PSD to the high end, greatly increasing the occupied bandwidth.
Bob didn't elaborate and no one picked up discussion of PSD but that is a great next topic.
PSD (Power Spectral Density) is the power density per unit bandwidth.? In TIA documents, PSD is referred to as SPD (Spectral Power Density.? ?SPD gives an idea about how the power of the signal is distributed over frequency.
A transmitter's SPD can be characterized by a power density measurement of its emissions over a specified frequency span using a spectrum analyzer?which presents a graphic display comprised of a number of discrete data points, each data point representing the amount of power measured in a ¡°frequency bin¡±
The TIA has published numerous documents to assist frequency coordinators, engineers, and coverage specialists in understanding how various modulation formats perform.?
These documents contain emission designators and graphs that show the SPD waveform for each modulation format to illustrate actual bandwidth requirements.
Life was easier when everything was 16K0F3E.? With the proliferation of formats including Securenet, EDACS, P25, DMR, Tetra, etc.? frequency coordinators face new challenges.
Amateurs have also faced the proliferation of modulation formats with folks experimenting with many of the commercial / public safety formats as well as new amateur digital formats such as D-Star and Fusion.
D-Star came first and presented new opportunities for frequency coordinators along with technical confusion - especially since Icom claimed d-Star signals fit in 6 kHz of spectrum.? They published numerous documents containing this claim.
Some hams initially accepted the claim.? In the left side of the attached image are some snips from Icom documents.? On the right is a graphic from the Illinois Repeater association that
clearly shows the acceptance of the claim that the entire D-Star modulation fits into 6 kHz of spectrum.
Astute hams soon investigated and realized the claim was a misrepresentation.??
Hopefully, as we continue the bandwidth discussion it will become clear how to assess the actual bandwidth requirements of various formats - especially in the context of band planning.
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At 11/12/2022 06:59 AM, you wrote: A lot of people tend to forget that EVERY transmitter has sideband noise. Regardless of the actual transmitted mode, there will be noise on either side of the carrier. Quite true, though for a well-designed oscillator this doesn't factor into adjacent-channel issues unless the adjacent RX is very close to the TX. Phase noise is more of an issue when considering required TX-RX isolation for duplex operation. In an FM signal, this noise extends into the squelch range of receivers on adjacent channels. Yes it can, but this noise has no more effect on adjacent RXs than any other broadband noise, be it natural or human-made. When Texas was considering 15 k vs 20k splits in the 80s, I did testing with Micor receivers on the bench and proved that 20 kilohertz was far superior to 15 spacing. The squelch was not affected at 20 kilohertz even with strong signals but at 15 it would cause issues big time along with desense of the desired channel. This is likely not due to phase noise, but rather due to leakage of the strong 15 kHz offset carrier through the IF filters heterodyning with the weak on-channel signal. The Micor only has 8 poles of IF filtering, so it's going to be far from a brick wall filter. Since the noise amps in most squelch circuits have a lot of gain at 15 kHz, it doesn't take much of a heterodyne with a weak signal to boost the total "noise" above the squelch threshold. Testing with a Spectrum repeater that was local to me, I could get 15 kHz off with a dead carrier w/no modulation, several miles away with a 30 watt mobile and squelch the receiver up on noisy signals. The receiver in the repeater was an SCR200 which used the typical Motorola MC3357 IF chip and had 15 kilohertz filters in it! Same tests at 20 caused no ill effects. Never worked with a Spectrum, but had a Hamtronics receiver with narrow IF filters & retrofitted Micor squelch board with the same problem: strong adjacent channel signals would not interfere with weak on-channel signals, but they would tend to tighten the squelch. Easiest solution was to disable the noise squelch, putting the controller in "mode 2" access (PL only). A bit of a squelch tail but with a good decoder like a G.E. Versatone & some audio delay, the squelch tail can still be eliminated. Not everybody runs high-end RF gear on a repeater. My testing was part of the reason why Texas went 20 kilohertz back in the 1980s. And I'm damn glad we did. If you don't need the spectrum for more repeaters, by all means. Here in SoCal 20 kHz would never have worked, & TBH I think it's wrong to let inferior equipment or poorly designed squelch circuits be the driver for bandplans. IMHO part of what ham radio is about is being able to do things a bit better than what the commercial folks can do. The recent discussion on repeat audio BW vs. channel spacing is a perfect example, & I'm really encouraged by Burt Weiner's success with his 147.240 repeater. By careful control of modulating parameters he was able to field a great sounding system without tearing up his adjacent channel neighbors. I even had Louisiana vote twice to go 20 kilohertz when I served on the board of directors of the Louisiana council. But unfortunately some die-hard idiots in New Orleans refused to move and the frequency coordinator gave up trying to change the state. Right now it's a mix of 20 and 15 across Louisiana. Maybe one day they'll join the 21st century.. But we're talking Louisiana here .... Almost as bad as Mississippi ???? Well, if those "die-hards" weren't offered replacement spectrum that was as good (clear) as where they are now, I can understand their reluctance. 20 kHz spacing does come with a price: less channels. I'm still waiting for a decent national band plan on 6m. The current plan is based on 50+ year-old radio technology! Really? When the ARRL took a poll back in the '90s, the results showed that majority wanted to stay the 1MHz split or go to the -1.7 WWARA plan... But the representatives from California and SCRRBA shoved that stupid 500 kilohertz outdated plan down the VRAC's throat.. I had a heated phone conversation with the West Gulf director about it and he was upset about it as well. But he said it was a political move and nobody wanted to argue against it. Well, that's BS! It's time 6M FM got into the 21st century as well.. I bet a lot of you don't even realize why 52.525 is such an oddball channel! If you do then you've been around as long as I have? ???? Yeah we'd be much better off with a wider split on 6. I only found one 6 meter repeater in SLC: it had a 1 MHz split & so much desense that it was unusable. Bob NO6B
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I'm curious about the reasons for selecting 52.525 MHz for the 6m simplex frequency.
All I can think of is channel 2 TV and the vestigial sideband filters at the TV transmitters...but that is just a "wild guess".
Eric? WB6TIX
At 11/12/2022 06:59 AM, you wrote:
>A lot of people tend to forget that EVERY transmitter has sideband noise. Regardless of the actual transmitted mode, there will be noise on either side of the carrier.
Quite true, though for a well-designed oscillator this doesn't factor into adjacent-channel issues unless the adjacent RX is very close to the TX.? Phase noise is more of an issue when considering required TX-RX isolation for duplex operation.
> In an FM signal, this noise extends into the squelch range of receivers on adjacent channels.
Yes it can, but this noise has no more effect on adjacent RXs than any other broadband noise, be it natural or human-made.
> When Texas was considering 15 k vs 20k splits in the 80s, I did testing with Micor receivers on the bench and proved that 20 kilohertz was far superior to 15 spacing. The squelch was not affected at 20 kilohertz even with strong signals but at 15 it would cause issues big time along with desense of the desired channel.
This is likely not due to phase noise, but rather due to leakage of the strong 15 kHz offset carrier through the IF filters heterodyning with the weak on-channel signal.? The Micor only has 8 poles of IF filtering, so it's going to be far from a brick wall filter.? Since the noise amps in most squelch circuits have a lot of gain at 15 kHz, it doesn't take much of a heterodyne with a weak signal to boost the total "noise" above the squelch threshold.
>Testing with a Spectrum repeater that was local to me, I could get 15 kHz off with a dead carrier w/no modulation, several miles away with a 30 watt mobile and squelch the receiver up on noisy signals. The receiver in the repeater was an SCR200 which used the typical Motorola MC3357 IF chip and had 15 kilohertz filters in it! Same tests at 20 caused no ill effects.
Never worked with a Spectrum, but had a Hamtronics receiver with narrow IF filters & retrofitted Micor squelch board with the same problem: strong adjacent channel signals would not interfere with weak on-channel signals, but they would tend to tighten the squelch.? Easiest solution was to disable the noise squelch, putting the controller in "mode 2" access (PL only).? A bit of a squelch tail but with a good decoder like a G.E. Versatone & some audio delay, the squelch tail can still be eliminated.
> Not everybody runs high-end RF gear on a repeater. My testing was part of the reason why Texas went 20 kilohertz back in the 1980s. And I'm damn glad we did.
If you don't need the spectrum for more repeaters, by all means.? Here in SoCal 20 kHz would never have worked, & TBH I think it's wrong to let inferior equipment or poorly designed squelch circuits be the driver for bandplans.? IMHO part of what ham radio is about is being able to do things a bit better than what the commercial folks can do.? The recent discussion on repeat audio BW vs. channel spacing is a perfect example, & I'm really encouraged by Burt Weiner's success with his 147.240 repeater.? By careful control of modulating parameters he was able to field a great sounding system without tearing up his adjacent channel neighbors.
>I even had Louisiana vote twice to go 20 kilohertz when I served on the board of directors of the Louisiana council. But unfortunately some die-hard idiots in New Orleans refused to move and the frequency coordinator gave up trying to change the state. Right now it's a mix of 20 and 15 across Louisiana. Maybe one day they'll join the 21st century.. But we're talking Louisiana here .... Almost as bad as Mississippi ????
Well, if those "die-hards" weren't offered replacement spectrum that was as good (clear) as where they are now, I can understand their reluctance.? 20 kHz spacing does come with a price: less channels.
>I'm still waiting for a decent national band plan on 6m. The current plan is based on 50+ year-old radio technology! Really? When the ARRL took a poll back in the '90s, the results showed that majority wanted to stay the 1MHz split or go to the -1.7 WWARA plan... But the representatives from California and SCRRBA shoved that stupid 500 kilohertz outdated plan down the VRAC's throat.. I had a heated phone conversation with the West Gulf director about it and he was upset about it as well. But he said it was a political move and nobody wanted to argue against it. Well, that's BS! It's time 6M FM got into the 21st century as well.. I bet a lot of you don't even realize why 52.525 is such an oddball channel! If you do then you've been around as long as I have?? ????
Yeah we'd be much better off with a wider split on 6.? I only found one 6 meter repeater in SLC: it had a 1 MHz split & so much desense that it was unusable.
Bob NO6B
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Here is my proposal for Texas in 1997 to go to the 1.7MHz split which was shot down due to politics (imagine that) ...it explains the history and why 525 is the oddball
On Sat, Nov 12, 2022, 7:38 PM Eric < vzwengr@...> wrote: I'm curious about the reasons for selecting 52.525 MHz for the 6m simplex frequency.
All I can think of is channel 2 TV and the vestigial sideband filters at the TV transmitters...but that is just a "wild guess".
Eric? WB6TIX
At 11/12/2022 06:59 AM, you wrote:
>A lot of people tend to forget that EVERY transmitter has sideband noise. Regardless of the actual transmitted mode, there will be noise on either side of the carrier.
Quite true, though for a well-designed oscillator this doesn't factor into adjacent-channel issues unless the adjacent RX is very close to the TX.? Phase noise is more of an issue when considering required TX-RX isolation for duplex operation.
> In an FM signal, this noise extends into the squelch range of receivers on adjacent channels.
Yes it can, but this noise has no more effect on adjacent RXs than any other broadband noise, be it natural or human-made.
> When Texas was considering 15 k vs 20k splits in the 80s, I did testing with Micor receivers on the bench and proved that 20 kilohertz was far superior to 15 spacing. The squelch was not affected at 20 kilohertz even with strong signals but at 15 it would cause issues big time along with desense of the desired channel.
This is likely not due to phase noise, but rather due to leakage of the strong 15 kHz offset carrier through the IF filters heterodyning with the weak on-channel signal.? The Micor only has 8 poles of IF filtering, so it's going to be far from a brick wall filter.? Since the noise amps in most squelch circuits have a lot of gain at 15 kHz, it doesn't take much of a heterodyne with a weak signal to boost the total "noise" above the squelch threshold.
>Testing with a Spectrum repeater that was local to me, I could get 15 kHz off with a dead carrier w/no modulation, several miles away with a 30 watt mobile and squelch the receiver up on noisy signals. The receiver in the repeater was an SCR200 which used the typical Motorola MC3357 IF chip and had 15 kilohertz filters in it! Same tests at 20 caused no ill effects.
Never worked with a Spectrum, but had a Hamtronics receiver with narrow IF filters & retrofitted Micor squelch board with the same problem: strong adjacent channel signals would not interfere with weak on-channel signals, but they would tend to tighten the squelch.? Easiest solution was to disable the noise squelch, putting the controller in "mode 2" access (PL only).? A bit of a squelch tail but with a good decoder like a G.E. Versatone & some audio delay, the squelch tail can still be eliminated.
> Not everybody runs high-end RF gear on a repeater. My testing was part of the reason why Texas went 20 kilohertz back in the 1980s. And I'm damn glad we did.
If you don't need the spectrum for more repeaters, by all means.? Here in SoCal 20 kHz would never have worked, & TBH I think it's wrong to let inferior equipment or poorly designed squelch circuits be the driver for bandplans.? IMHO part of what ham radio is about is being able to do things a bit better than what the commercial folks can do.? The recent discussion on repeat audio BW vs. channel spacing is a perfect example, & I'm really encouraged by Burt Weiner's success with his 147.240 repeater.? By careful control of modulating parameters he was able to field a great sounding system without tearing up his adjacent channel neighbors.
>I even had Louisiana vote twice to go 20 kilohertz when I served on the board of directors of the Louisiana council. But unfortunately some die-hard idiots in New Orleans refused to move and the frequency coordinator gave up trying to change the state. Right now it's a mix of 20 and 15 across Louisiana. Maybe one day they'll join the 21st century.. But we're talking Louisiana here .... Almost as bad as Mississippi ????
Well, if those "die-hards" weren't offered replacement spectrum that was as good (clear) as where they are now, I can understand their reluctance.? 20 kHz spacing does come with a price: less channels.
>I'm still waiting for a decent national band plan on 6m. The current plan is based on 50+ year-old radio technology! Really? When the ARRL took a poll back in the '90s, the results showed that majority wanted to stay the 1MHz split or go to the -1.7 WWARA plan... But the representatives from California and SCRRBA shoved that stupid 500 kilohertz outdated plan down the VRAC's throat.. I had a heated phone conversation with the West Gulf director about it and he was upset about it as well. But he said it was a political move and nobody wanted to argue against it. Well, that's BS! It's time 6M FM got into the 21st century as well.. I bet a lot of you don't even realize why 52.525 is such an oddball channel! If you do then you've been around as long as I have?? ????
Yeah we'd be much better off with a wider split on 6.? I only found one 6 meter repeater in SLC: it had a 1 MHz split & so much desense that it was unusable.
Bob NO6B
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Yeah we'd be much better off with a wider split on 6. I only found one 6
meter repeater in SLC: it had a 1 MHz split & so much desense that
it was unusable.
Bob NO6B
I run one of the 6 Meter repeaters in SLC on 53.150 with a 1 MHz split and it does not have any desense. It has been on the air for over 2 decades now.?
Where did you get your data?
John, K7JL
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At 11/12/2022 07:55 PM, you wrote: Yeah we'd be much better off with a wider split on 6. I only found one 6 meter repeater in SLC: it had a 1 MHz split & so much desense that it was unusable.
Bob NO6B
I run one of the 6 Meter repeaters in SLC on 53.150 with a 1 MHz split and it does not have any desense. It has been on the air for over 2 decades now.
Where did you get your data? My own radio (TH-9800), & observing that while I could kerchunk the repeater all over the place, that's all I could do. It had to be full scale & then some & I had to use 50 watts to get through while the TX was on. Was able to use (I think) 448.150 to duplex. My rough estimate was 20 to 30 dB of desense. Bob NO6B
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I've operated a 6-meter repeater for a couple decades. The thing I've learned is that noise generated near the receiver will desense it a lot.
6-meters now has a LOT of noise sources that were not there in the 80's. With my repeater, its receiver is essentially noise free in a very rural area. Going mobile is an entirely different thing.
I can be full quieting into the repeater and drive into an area with a lot of noise and it will wipe out the mobile's receive - yet I'm still full quieting into the repeater. And I'll add that I cannot (usually) hear any noise, yet it desenses the receiver. This typically happens in a populated area/business district. Noise blanker does absolutely no good as the noise in continuous.
Repeater is running at 100 watts, my mobile is about 50 watts. One of the reasons my county moved away from low band fire radios - mobile receive became very spotty in populated areas.
Chuck
WB2EDV
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On 11/13/2022 12:00 AM, Bob Dengler via groups.io wrote: At 11/12/2022 07:55 PM, you wrote:
Yeah we'd be much better off with a wider split on 6. I only found one 6 meter repeater in SLC: it had a 1 MHz split & so much desense that it was unusable.
Bob NO6B
I run one of the 6 Meter repeaters in SLC on 53.150 with a 1 MHz split and it does not have any desense. It has been on the air for over 2 decades now.
Where did you get your data? My own radio (TH-9800), & observing that while I could kerchunk the repeater all over the place, that's all I could do. It had to be full scale & then some & I had to use 50 watts to get through while the TX was on. Was able to use (I think) 448.150 to duplex. My rough estimate was 20 to 30 dB of desense.
Bob NO6B
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Depends on the noise blanker... My 30+ years of low band FM experience found that some noise blankers work better than others.. The lowband Motorola Micor "extender" had a bad habit of breaking into oscillation and actually killing the main channel.... yet a GE Master 2 kept on clicking. I ran into this several times on my low band base stations at Gulf States Utilities.. in fact we picked up a number of Micor low band receiver decks that came from CHP, with the noise blanker tune to 51.0 megahertz which is exactly what I was doing. They acted the same way.
Oddly enough, the Midland Syntech 2 series outdid other brands. Unfortunately most amateur gear does not have NBs that works in the FM mode. I complained to Yaesu at Dallas HamCom a couple of years ago and they answered oh it works! I looked at them with one eyebrow raised and said really? Have you checked that? Their response was Well maybe it doesn't.. But then you don't need it on FM! I shook my head and told them my experience on low band commercial VHF and then asked if you don't need it, why does your commercial line have it on low band? I got a blank stare back on that one...
6m along with 10m to a lesser extent needs a noise blanker on any mode.. which is why most people on 6 m FM only run commercial gear... My Midland Syntech 2's can out hear a Motorola Syntor 9000x... Using legacy gear on a repeater, such as a GE Master 2 or similar, along with a duplexer, means you can't use the built-in noise blanker as it requires a separate frequency away from the receive channel and the duplexer won't allow that to pass. The IF based NB's that are used in radios such as the GE Deltas, Midlands, etc will work in a duplex mode. Personally I prefer split side on 6m anyway even though it's hard to find two tower sites sometimes ....But it may be cheaper than a duplexer on low band lol.
Chris WB5ITT?
On Sun, Nov 13, 2022, 8:03 AM Chuck Kelsey < wb2edv@...> wrote: I've operated a 6-meter repeater for a couple decades. The thing I've
learned is that noise generated near the receiver will desense it a lot.
6-meters now has a LOT of noise sources that were not there in the 80's.
With my repeater, its receiver is essentially noise free in a very rural
area. Going mobile is an entirely different thing.
I can be full quieting into the repeater and drive into an area with a
lot of noise and it will wipe out the mobile's receive - yet I'm still
full quieting into the repeater. And I'll add that I cannot (usually)
hear any noise, yet it desenses the receiver. This typically happens in
a populated area/business district. Noise blanker does absolutely no
good as the noise in continuous.
Repeater is running at 100 watts, my mobile is about 50 watts. One of
the reasons my county moved away from low band fire radios - mobile
receive became very spotty in populated areas.
Chuck
WB2EDV
On 11/13/2022 12:00 AM, Bob Dengler via wrote:
> At 11/12/2022 07:55 PM, you wrote:
>> Yeah we'd be much better off with a wider split on 6. I only found one 6 meter repeater in SLC: it had a 1 MHz split & so much desense that it was unusable.
>>
>> Bob NO6B
>>
>>
>> I run one of the 6 Meter repeaters in SLC on 53.150 with a 1 MHz split and it does not have any desense. It has been on the air for over 2 decades now.
>>
>> Where did you get your data?
> My own radio (TH-9800), & observing that while I could kerchunk the repeater all over the place, that's all I could do.? It had to be full scale & then some & I had to use 50 watts to get through while the TX was on.? Was able to use (I think) 448.150 to duplex.? My rough estimate was 20 to 30 dB of desense.
>
> Bob NO6B
>
>
>
>
>
>
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The Delta I used as mobile for a while had a noise blanker that did not help at all. The noise I'm talking about is continuous - coming from POS terminals, routers, DSL, LED sign boards and lighting, etc. Before these things came along, noise blankers worked great on in things like ignition and other random buzzes, clicks, bursts.
Chuck
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On 11/13/2022 9:24 AM, Chris Boone wrote: ?The IF based NB's that are used in radios such as the GE Deltas, Midlands, etc will work in a duplex mode.
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This happens to me on 6 meters many times when I am near a new style stoplight. The noise shows up on my S-meter indicator as full scale, but no audio and the squelch does not open. It appears that many of the LEDs create broadband noise on both 6 and 2 meters. It is apparent that it is coming from the stoplight because, sometimes when the light turns green, the noise goes away.
Joe
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Show quoted text
On 11/13/2022 9:03 AM, Chuck Kelsey wrote: I can be full quieting into the repeater and drive into an area with a lot of noise and it will wipe out the mobile's receive - yet I'm still full quieting into the repeater. And I'll add that I cannot (usually) hear any noise, yet it desenses the receiver. This typically happens in a populated area/business district.
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Bingo! That's one of the sources. Fire Departments used to complain
that they could not hear dispatch when near a stoplight.
I am forced to keep my 6-M mobile in tone squelch due to all the
noise that can be heard as one drives along. I watch the
S-meter go half scale on noise quite often. It would drive me out of
the car if radio was in carrier squelch.
It's sad that the FCC doesn't care about noise levels any more. But
in reality, they don't care about much of anything these days.
Chuck
WB2EDV
On 11/13/2022 10:24 AM, Joe wrote:
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This
happens to me on 6 meters many times when I am near a new style
stoplight.? The noise shows up on my S-meter indicator as full
scale, but no audio and the squelch does not open.? It appears
that many of the LEDs create broadband noise on both 6 and 2
meters.? It is apparent that it is coming from the stoplight
because, sometimes when the light turns green, the noise goes
away.
Joe
On 11/13/2022 9:03 AM, Chuck Kelsey wrote:
I can be full quieting into the repeater
and drive into an area with a lot of noise and it will wipe out
the mobile's receive - yet I'm still full quieting into the
repeater. And I'll add that I cannot (usually) hear any noise,
yet it desenses the receiver. This typically happens in a
populated area/business district.
|
This happens to me on 6 meters many times when I am near a new style stoplight. The noise shows up on my S-meter indicator as full scale, but no audio and the squelch does not open. It appears that many of the LEDs create broadband noise on both 6 and 2 meters. It is apparent that it is coming from the stoplight because, sometimes when the light turns green, the noise goes away.
Most interesting discussion!
For a couple of years now, I've had a broad-band noise like that show up on 2M in my neighborhood, every evening. Start time varies with sunset, and it goes away about four hours later. Walking around with an HT set to AM and a tape measure yagi hasn't helped me locate it, since it isn't quite strong enough for the HT to register a change. But it wipes out any FM signals S5 or lower on my base set up with a Diamond X510HDM on the roof of the house here. I suppose it could be just about anything. Highly annoying.
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My 2 meter repeater is on 147.015MHz. It's output frequency is close enough to a microprocessors multiple of 1MHz, such as 147.000, that users occasionally have problems hearing the repeater. It appears that some light devices are very efficient at giving off multiple harmonics. I get reports of the repeater transmitter dropping out at times, when in actuality it most likely a mobile user driving by something causing interference. Stoplights seem to be the biggest offender. I've gone by the problem area reported and, sure enough, there is a stoplight causing noise at times (usually red light for some unknown reason causes noise). Sometimes it causes the mobile receiver to blank out, most likely wide band noise.
It's hard to get users to accept this possible explanation.
Joe
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Show quoted text
On 11/13/2022 10:54 AM, Chris Smart wrote: For a couple of years now, I've had a broad-band noise like that show up on 2M in my neighborhood, every evening. Start time varies with sunset, and it goes away about four hours later. Walking around with an HT set to AM and a tape measure yagi hasn't helped me locate it, since it isn't quite strong enough for the HT to register a change. But it wipes out any FM signals S5 or lower on my base set up with a Diamond X510HDM on the roof of the house here. I suppose it could be just about anything. Highly annoying.
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At 11/13/2022 07:48 AM, you wrote: Bingo! That's one of the sources. Fire Departments used to complain that they could not hear dispatch when near a stoplight.
I am forced to keep my 6-M mobile in tone squelch due to all the noise that can be heard as one drives along. I watch the S-meter go half scale on noise quite often. It would drive me out of the car if radio was in carrier squelch. I've found that different radios respond differently to high noise levels: some will blow squelch, requiring you to turn up the squelch to the point that once you get away from the noise source, it takes over 10 dB quieting to open it in the relatively noise free environment. A good example of this is in comparing the Yaesu FT-8900 to the TYT TH-9800 on 6 meters. With the Yaesu I do have to use CTCSS squelch all the time, but the TYT's squelch stays shut when set on threshold unless a stray signal actually quiets the RX. Weird that it's the Chinese knock-off radio that behaves properly, but it's true. I have a Kenwood TK-780 that had this problem so bad I couldn't use it as a mobile radio. I was able to fix it by modifying the noise filter per the attached PDF. Apparently the noise above ~15 kHz is negatively affected by the limiter action in the RX, so putting a limit to the high end response of the noise squelch prevents the changing noise level from affecting it. Bob NO6B
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On 11/13/2022 12:00 AM, Bob Dengler via groups.io wrote: At 11/12/2022 07:55 PM, you wrote:
Yeah we'd be much better off with a wider split on 6. I only found one 6 meter repeater in SLC: it had a 1 MHz split & so much desense that it was unusable.
Bob NO6B
I run one of the 6 Meter repeaters in SLC on 53.150 with a 1 MHz split and it does not have any desense. It has been on the air for over 2 decades now.
Where did you get your data? My own radio (TH-9800), & observing that while I could kerchunk the repeater all over the place, that's all I could do. It had to be full scale & then some & I had to use 50 watts to get through while the TX was on. Was able to use (I think) 448.150 to duplex. My rough estimate was 20 to 30 dB of desense.
Bob NO6B
There's no doubt in my mind there is something wrong with that machine. If it's using a duplexer (most 6M rptrs in Ohio are split site), it's got a problem or not tuned right. But more likely is just that it has tons of broad band noise to contend with. It's not unusual to see 15-30 dB of desense due to noise anymore. It's considered normal on 6M. Also, 50 watts is on the bottom end of usability for 6M FM. Normal mobile power, and what most repeaters here are balanced to work at is 80-100 watts.
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Dont you think 6m plan is not so critical.? Might be in CA, but most of the world 6m repeaters are dead, kinda do what one wants although should follow some standards such as splits.
On 6m much easier to get separation at 1 MHz.? If you got a good set of duplexers then fine, but often on 6m other methods are used liek1-5/8 coax homebrew.
Here in Florida coordinators tried to force 7.5 kHz channels on 2m.? We are now 15 kHz on 146/147, 20 on 144/145.? And also make all go narrow band.? Did not work, most ignored it for good reason.? And never mind most 2m Ham rigs will not do 7.5kHz.? Very newer ones will, but 90% of what is out there will not.? And so much of the repeater gear is not setup for it.
73, ron, n9ee/r
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The wide band noise is why we need duplexer cavities on the transmitter, to notch or filter that noise at the rcv freq.? How much noise determines the duplexer needed.
For a clown messing with one of my repeaters I have tuned off 15 kHz and transmitted and the rcvr sq closed giving the impression the clown was not hitting the repeater.? This was with Micor repeater. At 20 kHz did not work. ? If one knows their gear they can do more.
73, ron, n9ee/r
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On 11/15/2022 12:06 PM, Ron Wright via groups.io wrote: The wide band noise is why we need duplexer cavities on the transmitter, to notch or filter that noise at the rcv freq.? How much noise determines the duplexer needed. Well, the noise I'm talking about is on channel noise. No filter will take that out without taking out the desired signals too. For a clown messing with one of my repeaters I have tuned off 15 kHz and transmitted and the rcvr sq closed giving the impression the clown was not hitting the repeater.? This was with Micor repeater. At 20 kHz did not work. ? If one knows their gear they can do more.
73, ron, n9ee/r
_._,_._,_ I know what you're talking about there, done it. If I was 15 off, I had to whistle really, REALLY loud to have any effect. 10 KHz however was easy-with a normal Micor or Motrac type rx. There used to be a UHF repeater here many years ago that was a Regency Micro-Comm that had not one but two gaas-fet preamps in front of it on a 500 ft tower. I could hit it from 30 miles away with one watt-10 Khz off frequency. Might have even still been copyable into it.
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Chris Boone WB5ITT