Re: QUANTAR VHF Audio Interface...
Kevin,
I do agree with you?that this group can be about going outside of what is normally done with repeaters and improving on them - so in that respect maybe my comment was a bit off the mark.??
I will disagree with your inference that Quantar has "substandard frequency response".? Which standard are you comparing it to?? I would suggest that Quantar and other repeaters of similar performance ARE the industry standard.? I believe what the goal of this post was - and what you prefer - would be considered a "superior frequency response" while Quantar would match or exceed "Standard frequency response".? I understand the goal here - the question is what has to be given up to achieve it and is it worth it.? I worked in pro audio (install/recording/touring) for many years so I also appreciate quality audio - but it also has to be practical and not cause other technical and functional issues in the process.
If I get some time this week, since I have the test equipment to do it, I might setup a Quantar on the bench and do some tests to see what the actual frequency response is through the internal repeat audio path - and then change some of the settings to see how they impact it.? I will use Pink Noise as a baseline, below the deviation limiter threshold -? then I can play some high-quality/wide range voice through to see the actual impact on the intelligibility and quality.? I will probably use my HP 8924C and Ivie IE-30A/IE-20P to perform the testing.? The HP 8924C has the ability to turn off the pre-emphasis/de-emphasis and both low and high-pass filters so it is ideal for the task and will likely?outperform any available transceiver in regards to modulating a "flat" response.? I am curious how the Quantar will perform.
Thanks, Daniel Woodie, CETsr KC8ZUM
M: +1.513.478.9844
H: +1.513.231.1101 ? ? ? ? ? ? ? ? ?  
On Tue, Oct 25, 2022 at 11:07 PM Kevin Custer < kuggie@...> wrote:
On 10/25/2022 10:36 PM, Dan Woodie
wrote:
-------------------BIG snip
----------------------------
I feel there are far more important things to be spending
money and time on than trying to create a Hi-Fi repeater
------------------------BIG snip ---------------------
Daniel Woodie, CETsr
KC8ZUM
But that's one of the reasons this group
exists - not most of the other things you wrote about.? Keep that
in mind when replying to this group.? We're about highly technical
stuff here.
And - just because some of the radios that users use are junk -
doesn't mean we should be building repeaters that have substandard
frequency response.?
I can also hear the difference between a properly built repeater
and a stock "300Hz - 3kHz" one.? You want to hear a thing of
beauty - listen to one of the WN3A built machines.? Observation of
wider audio frequency response and properly built and set
processing will change your opinion.
Kevin W3KKC
|
Re: QUANTAR VHF Audio Interface...
On 10/25/2022 10:36 PM, Dan Woodie
wrote:
-------------------BIG snip
----------------------------
I feel there are far more important things to be spending
money and time on than trying to create a Hi-Fi repeater
------------------------BIG snip ---------------------
Daniel Woodie, CETsr
KC8ZUM
But that's one of the reasons this group
exists - not most of the other things you wrote about.? Keep that
in mind when replying to this group.? We're about highly technical
stuff here.
And - just because some of the radios that users use are junk -
doesn't mean we should be building repeaters that have substandard
frequency response.?
I can also hear the difference between a properly built repeater
and a stock "300Hz - 3kHz" one.? You want to hear a thing of
beauty - listen to one of the WN3A built machines.? Observation of
wider audio frequency response and properly built and set
processing will change your opinion.
Kevin W3KKC
|
Re: QUANTAR VHF Audio Interface...
Just a note from the gallery here -? but to me it seems that some are confusing frequency deviation and frequency response in this thread.? Both are important for their own reasons, both are measured in Hz/kHz, and both impact audio quality but they are most definitely not the same thing and an increase in frequency response does not (necessarily) mean an increase in frequency deviation (though there will often be some difference since additional audio energy is added to the signal).
As far as frequency response goes the Quantar 25-pair connector contains wideband RX and TX connections that are suitable for most applications for Data and unfiltered voice.? Personally I find that the best performance for voice is to use the internal controller for all audio routing.? If you must connect an external controller for control and voice announcements don't use it as the repeat audio path.? The voice announcements?can be recorded?from the receiver and transmitted from the wireline/flat audio in and given lower priority than the internal repeat function - so they will be overridden when there is an active QSO - and the internal CW ID can keep things legal.? I see no purpose in trying to make a "Hi-Fi" repeater when half of the users are using Baofengs and 99.9% of the other radios are using speakers and mics that won't benefit anyway - or it can often make it sound worse with the wide range.? The range below 300 Hz is filtered on pretty much all transceivers on receive or you would hear PL tones consistently - and above 3K you are just going to get more pronounced noise for which the pre-emphasis/de-emphasis is unlikely to help.? Having the frequency response set too wide can also impact deviation controls since proximity effect and similar things related to the additional ranges can become an issue when they were not previously.? A frequency response of 300-3000 KHz will produce optimal speech intelligibility for communications in the majority of situations.? If needed, the Quantar also allows you to disable Pre-Emphasis, De-Emphasis, and Hi-Pass filters from WinRSS which, "in essence, provides a flat audio path through the station" per the WinRSS help file.
As far as frequency deviation goes, that directly impacts the audio dynamic range.? While it can be beneficial in some instances to use an expander or compander function to bring up low-level signals, the down-side of this is the significant increase in noise and decrease in dynamic range (the difference in magnitude from the lowest-level sound to the highest-level sound).? Decreasing dynamic range can severely impact both voice intelligibility and perceived audio quality.? When using the internal controller for audio routing you can utilize the "Analog Repeater Boost" function to increase the level of stations, but keep in mind that this will effectively decrease your overall audio dynamic range by about 20% as it will push louder stations into the deviation limiter.? Below is what the RSS Manual has to say about this function: Toggle between ENABLED and DISABLED by pressing the Up/Down Arrow keys.
When ENABLED (default state), an incoming 40% rated system deviation
signal will be boosted to 60% rated system deviation for re-transmission.
For example, in a 5KHz maximum deviation channel, a signal coming in at
2 KHz deviation will be transmitted at 3 KHz deviation.
When DISABLED, the transmitted signal will be at the same deviation as
the incoming signal.
Default setting is DISABLED. ?A more aggressive Audio Dynamic Range control in the Quantar is called "Hear Clear".? It is an aggressive compander which, in my experience, makes the audio sound absolutely terrible and far less intelligible.
I run all of my Quantars with pre-emphasis and de-emphasis disabled (since I have no need for audio inputs/outputs at the site, and therefore no need for de-emphasized inputs/outputs), with repeater boost turned off, hear clear turned off, and with the deviation limit set at 98% (to ensure I stay within 5 KHz Deviation).? All of my repeaters sound excellent to me and many have complemented the audio compared to the many other repeaters in the area.? If someone has low audio coming into the repeater then it is on them to resolve their issue and the other users are generally quick to report the issue to those users.? If they are too hot the deviation limiter will take care of keeping me in compliance even though they may get clipped a bit,?often also resulting in reports to those stations of their poor audio quality.
I feel there are far more important things to be spending money and time on than trying to create a Hi-Fi repeater - like bringing new Hams into the hobby - and teaching some of them to be the next generation of technicians to maintain this equipment,?but to each their own.? I believe in the KISS principle most of the time - why take an excellent, highly Engineered repeater such as a Quantar and try to reinvent the wheel with it when it does exceedingly well as-is.? Quantars have so many options as-is with all of the inputs/outputs/wildcards, etc that you can do pretty much anything you could ever want with this platform without adding piles of external controllers, processors, filters, etc.
Most (but not all) external controllers with audio delays tend to decrease both frequency response and dynamic range due to limitations in the delay circuitry.? This is one of the primary reasons I always avoid using an external controller for the repeater audio path, in addition to coloration (changes in frequency response) that can be caused by impedance mismatches and other parts of the audio circuits of the external controllers.? The internal Quantar repeat audio path is designed such that the signal (within the 300-3000 Hz pass-band) at the Gozinta matches the signal at the Gozouta (technical terms) so long as the audio settings are left at default.? Since the Quantar has a built-in community tone panel you can use a non-repeated PL/DPL for control tones, completely eliminating the need for an audio delay while still delivering the control codes to your controller - which can control the Quantar via contact closures on the 25-Pair connector. Daniel Woodie, CETsr KC8ZUM
M: +1.513.478.9844
H: +1.513.231.1101 ? ? ? ? ? ? ? ? ?
Yes, Burt, I also agree with that concept because it is better in those circumstances of low initial audio and to me it also makes sense to increase intelligibility when you are receiving noise on the repeater.? It does usually reduce the highs from them being selectively clipped, so the question is how do you boost the highs back when the clipping is done on pre-emphasized audio as defined by the same voltage at the clipper when the input frequency is swept from lowest to highest frequency at the same input deviation? By adding high frequency boost after the clipper, and then more low pass filtering?
To my thinking, the advantage from no repeater compression or clipping is when you want to repeat a repeat times X in analog so as to not keeping adding background noise or distortion each time. Guess that is one big advantage of digital repeaters?
John
On 10/25/2022 4:47 PM Burt K6OQK < biwa@...> wrote:
John,
I personally do not believe in the 5 kHz in and 5 kHz out thinking.? A part of the problem is that stations with low deviation will come through with low deviation and those with high deviation can hit the transmitter's limiter too hard.? Some believe that it's the responsibility of those stations to correct their deviation, and learn to use correct mic technique. My experience in that area has proven to be: Good Luck!
Please understand, I don't mean to be talking at you, but just intellectualizing with you...
To my way of thinking, a repeater is not a piece of test equipment to be used as a deviation tester.? It's a contraption to improve / enable communications.? Proper processing also protects the transmitter and adjacent channel spectrum in a less destructive way.? Anything I can do to make it simple, reliable, and pleasant, is a plus.? That's why I have always used appropriate audio processing on my repeaters.? I've gotten arguments from the unwashed telling me that it brings up the noise on the incoming signal. Well, yes, that's true, but you're going to have to turn up the volume at the user's end if you want to hear those stations anyway.? When you do that you are not only bringing up the noise heard by the repeater, but also any noise between and the repeater.? Having to turn the volume up and down while listening to a repeater gets tiring after a while.
For what it's worth,
Burt, K6OQK
|
Re: Vxr-7000, change serial number in CE27 software
Was there supposed to be an image in your reply? I just see a blank box.
73 and aloha, Eric KH6CQ
On Tuesday, October 25, 2022 at 04:17:39 PM HST, Jack Mcelyea/n4jem via groups.io <n4jem@...> wrote:
Can be changed it you have dealer software Have a blessed day/n4jem ![]()
On Tuesday, October 25, 2022, 9:32 PM, Jamie WW3S <ww3s@...> wrote: We have multiple vxr-7000 repeaters in use, and I kludged one up. I suspect I did a download, rather than an upload, and installed a config file, including the serial number from a second repeater. Is it possible to reset the serial number so it matches the tag on the unit?
|
Re: Vxr-7000, change serial number in CE27 software
Can be changed it you have dealer software Have a blessed day/n4jem 
On Tuesday, October 25, 2022, 9:32 PM, Jamie WW3S <ww3s@...> wrote: We have multiple vxr-7000 repeaters in use, and I kludged one up. I suspect I did a download, rather than an upload, and installed a config file, including the serial number from a second repeater. Is it possible to reset the serial number so it matches the tag on the unit?
|
Re: QUANTAR VHF Audio Interface...
---------- Original Message ----------
From: John <jhaserick84@...>
Date: 10/25/2022 8:38 PM
Subject: Re: [repeater-builder] QUANTAR VHF Audio Interface...
Yes, Burt, I also agree with that concept because it is better in those circumstances of low initial audio and to me it also makes sense to increase intelligibility when you are receiving noise on the repeater.? It does usually reduce the highs from them being selectively clipped, so the question is how do you boost the highs back when the clipping is done on pre-emphasized audio where flat audio is defined by the same voltage at the clipper when the input frequency is swept from lowest to highest frequency at the same input deviation? By adding high frequency boost after the clipper, and then more low pass filtering? Possibly easier and better to just eliminate the pre-emphasis components before the clipper, and add comparable pre-emphasis after the clipper so a little audio compression without reducing highs and still the same low pass roll-off. There must be a way to configure Kevin's clipper /filter to achieve this result.
To my thinking, the advantage from having no repeater compression or clipping is when you want to repeat a repeat times X in analog so as to not keeping adding background noise or distortion each time, at least on the link radios if a quiet link path. Guess that is one big advantage of digital repeaters?
John
On 10/25/2022 4:47 PM Burt K6OQK <biwa@...> wrote:
John,
I personally do not believe in the 5 kHz in and 5 kHz out thinking.? A part of the problem is that stations with low deviation will come through with low deviation and those with high deviation can hit the transmitter's limiter too hard.? Some believe that it's the responsibility of those stations to correct their deviation, and learn to use correct mic technique. My experience in that area has proven to be: Good Luck!
Please understand, I don't mean to be talking at you, but just intellectualizing with you...
To my way of thinking, a repeater is not a piece of test equipment to be used as a deviation tester.? It's a contraption to improve / enable communications.? Proper processing also protects the transmitter and adjacent channel spectrum in a less destructive way.? Anything I can do to make it simple, reliable, and pleasant, is a plus.? That's why I have always used appropriate audio processing on my repeaters.? I've gotten arguments from the unwashed telling me that it brings up the noise on the incoming signal. Well, yes, that's true, but you're going to have to turn up the volume at the user's end if you want to hear those stations anyway.? When you do that you are not only bringing up the noise heard by the repeater, but also any noise between and the repeater.? Having to turn the volume up and down while listening to a repeater gets tiring after a while.
For what it's worth,
Burt, K6OQK
|
Vxr-7000, change serial number in CE27 software
We have multiple vxr-7000 repeaters in use, and I kludged one up. I suspect I did a download, rather than an upload, and installed a config file, including the serial number from a second repeater. Is it possible to reset the serial number so it matches the tag on the unit?
|
Re: Sinclair R-302C duplexer info
When I got started the high notch was out of tune. I went back and put it back to original frequencies and got -69 and -65db notches. On the new frequencies it is -62db you are probably right about changing cable lengths. Looks like Sinclair used elbows to stretch the low side. I probably need to look for some TNC elbows that are reasonably priced or see if -62dB is good enough.
Ben Stapp KB5ZO
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Re: QUANTAR VHF Audio Interface...
Yes, Burt, I also agree with that concept because it is better in those circumstances of low initial audio and to me it also makes sense to increase intelligibility when you are receiving noise on the repeater.? It does usually reduce the highs from them being selectively clipped, so the question is how do you boost the highs back when the clipping is done on pre-emphasized audio as defined by the same voltage at the clipper when the input frequency is swept from lowest to highest frequency at the same input deviation? By adding high frequency boost after the clipper, and then more low pass filtering?
To my thinking, the advantage from no repeater compression or clipping is when you want to repeat a repeat times X in analog so as to not keeping adding background noise or distortion each time. Guess that is one big advantage of digital repeaters?
John
On 10/25/2022 4:47 PM Burt K6OQK <biwa@...> wrote:
John,
I personally do not believe in the 5 kHz in and 5 kHz out thinking.? A part of the problem is that stations with low deviation will come through with low deviation and those with high deviation can hit the transmitter's limiter too hard.? Some believe that it's the responsibility of those stations to correct their deviation, and learn to use correct mic technique. My experience in that area has proven to be: Good Luck!
Please understand, I don't mean to be talking at you, but just intellectualizing with you...
To my way of thinking, a repeater is not a piece of test equipment to be used as a deviation tester.? It's a contraption to improve / enable communications.? Proper processing also protects the transmitter and adjacent channel spectrum in a less destructive way.? Anything I can do to make it simple, reliable, and pleasant, is a plus.? That's why I have always used appropriate audio processing on my repeaters.? I've gotten arguments from the unwashed telling me that it brings up the noise on the incoming signal. Well, yes, that's true, but you're going to have to turn up the volume at the user's end if you want to hear those stations anyway.? When you do that you are not only bringing up the noise heard by the repeater, but also any noise between and the repeater.? Having to turn the volume up and down while listening to a repeater gets tiring after a while.
For what it's worth,
Burt, K6OQK
|
Re: QUANTAR VHF Audio Interface...
Mt Wilson's rep lasts a long time!
At 01:53 PM 10/25/2022, you wrote:
toggle quoted message
Show quoted text
jb,
I want to assure you that WA6TDD was not that way when I ran it.?
Once it started to turn in that direction I tried my best to clean it
up.? When that failed I got rid of it.? I will not be a part of
that kind of operation.? Please do not associate me with the .435
operation.
Burt, K6OQK
On Tue, Oct 25, 2022 at 01:32 PM, jb wrote:
- Then I looked up K6OQK and saw 147.435 in Los Angeles.? I think
that one is world famous for sending the FCC packing, and pushing the
envelope well past the 7 dirty words.? Maybe when Burt was involved
it wasn't that way, but it became the attractive nuisance of the amateur
community.? stories like that prevented me from even toying with the
idea of putting up a ham repeater.? I have dabbled with remotes, but
keep it real low key.? I have enough trouble with commercial 2way to
keep me busy.
------------------------------------------------------------------------------
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Makers of repeater controllers and accessories
Phone: (503) 678 6182
Authorized Dealers for Kenwood and Telewave.
We offer complete turn-key repeater packages!
"We don't just make 'em. We use 'em!"
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Re: QUANTAR VHF Audio Interface...
jb,
I want to assure you that WA6TDD was not that way when I ran it.? Once it started to turn in that direction I tried my best to clean it up.? When that failed I took it off the air and others picked it up.? I will not be a part of that kind of operation.? Please do not associate me with the .435 operation.
Burt, K6OQK
toggle quoted message
Show quoted text
On Tue, Oct 25, 2022 at 01:32 PM, jb wrote:
Then I looked up K6OQK and saw 147.435 in Los Angeles.? I think that one is world famous for sending the FCC packing, and pushing the envelope well past the 7 dirty words.? Maybe when Burt was involved it wasn't that way, but it became the attractive nuisance of the amateur community.? stories like that prevented me from even toying with the idea of putting up a ham repeater.? I have dabbled with remotes, but keep it real low key.? I have enough trouble with commercial 2way to keep me busy.
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Re: QUANTAR VHF Audio Interface...
? My point is, where is the energy above 3Khz comming from?? Unless it is background music or road noise.? ? Sibilance. The hand mics with many Yaesu VHF/UHF mobiles, and their newer HT¡¯s, have quite a bit above 3K, I¡¯m going to say up to about 4.6 or 4.7. ? I love the sound of repeaters that let some of that through, although not too much¡ not as much as you hear on simplex. But similar¡ ?
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Re: QUANTAR VHF Audio Interface...
John,
I personally do not believe in the 5 kHz in and 5 kHz out thinking.? A part of the problem is that stations with low deviation will come through with low deviation and those with high deviation can hit the transmitter's limiter too hard.? Some believe that it's the responsibility of those stations to correct their deviation, and learn to use correct mic technique. My experience in that area has proven to be: Good Luck!
Please understand, I don't mean to be talking at you, but just intellectualizing with you...
To my way of thinking, a repeater is not a piece of test equipment to be used as a deviation tester.? It's a contraption to improve / enable communications.? Proper processing also protects the transmitter and adjacent channel spectrum in a less destructive way.? Anything I can do to make it simple, reliable, and pleasant, is a plus.? That's why I have always used appropriate audio processing on my repeaters.? I've gotten arguments from the unwashed telling me that it brings up the noise on the incoming signal. Well, yes, that's true, but you're going to have to turn up the volume at the user's end if you want to hear those stations anyway.? When you do that you are not only bringing up the noise heard by the repeater, but also any noise between and the repeater.? Having to turn the volume up and down while listening to a repeater gets tiring after a while.
For what it's worth,
Burt, K6OQK
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Re: QUANTAR VHF Audio Interface...
My point is, where is the energy above 3Khz comming from?? Unless it is background music or road noise.? The audio
spectrum from the human voice isn't there.? The idea of getting AM broadcast to 6kc was to help music reproduction.?
If the voice audio is well equalized for inteligibility, it's not a bad thing to have 50hz- 6khz but you won't likely hear anything
above 3000 and if anyone wants to do any bass boosting it will get old fast.? And there is no reason to pass the PL either.
If someone really WANTS 6kc audio, it will have to be addressed throughout the chain, and keep an eye on the spectrum
analyzer.
?
Then I looked up K6OQK and saw 147.435 in Los Angeles.? I think that one is world famous for sending the FCC packing,
and pushing the envelope well past the 7 dirty words.? Maybe when Burt was involved it wasn't that way, but it became the
attractive nuisance of the amateur community.? stories like that prevented me from even toying with the idea of putting up
a ham repeater.? I have dabbled with remotes, but keep it real low key.? I have enough trouble with commercial 2way to keep
me busy.
toggle quoted message
Show quoted text
On Tue, Oct 25, 2022 at 11:12 AM, Bob Dengler wrote:
At 10/24/2022 06:59 PM, you wrote:
When I first saw the question, I scratched my head and went on to other things. It looked wierd. Then I remembered why.
If you are actually going to feed audio up to 6 khz. to the modulator, where does it actually go after that???
Even if you reduce the deviation and the pre-emphasis to keep the bandwidth down to a normal FM channel, anyone trying
to recieve it will have to modify the reciever so it won't squelch itself out trying to recieve.
Literally hundreds of 440 repeaters in this area have audio responses approaching 6 kHz, & no one has had to modify their RXs to hear them.
Sounds confusing, but the typical 16kF3 reciever needs to have a 20khz bandwidth in the IF to allow for drift and to prevent
the reciever from squelching out. The back-end was made to roll off above 3khz to the speech amp and the squelch amp will
be listening for noise above that to keep the squelch closed.
Much above, actually. The last squelch circuit I looked at actually responded best to noise around 10-20 kHz, so 6 kHz won't really affect it much
If this is for a link radio on the 2m ham band, how were you planning to keep the bandwidth to a normal ham channel? If this is
for a ham voice repeater, everyone will have to modify their radios to use it.
Nope - see above. Granted on 2 meters with 15 kHz channel spacing some modifications to the standard are needed. I find that by keeping the deviation down to, say 4.2 kHz peak, the occupied BW is sufficiently controlled without losing S/N. 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 NO6B
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Re: Repeater Horror Stories
On a 'news gathering link' service I assisted running, basically a 150KHz wide FM repeater we found a pirate station trying to use it.
We had remote control of the settings and when not using it changed the output 25KHz CTCSS tone to something like 250HZ and 100KHz dev.
And on another ocassion a different station was trying to use the frequency. We rigged a system near their 'studio' receiving their transmissions, linked on a different band to the area we believed their band II transmitter was located and adding a lot of 50Hz (actually tapped off TX mains transformer) and rebroadcasting on original frequency. We thought the pirate station sounded really cool.
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Re: QUANTAR VHF Audio Interface...
Flat audio really means no de-emphasis in the RCVR being coupled to the TX with no pre-emphasis.?
Hopefully with less processing. Of course on a PM radio vs. a FM modulator means something different.?
A lot of people get the whole Pre and De-emphasis and flat audio wrong because they are plugging
different things together and picking from jumpers one way or another and finding more must be done.
There is truely much to be desired on most under-dash mobiles.? There is a lot of poor quality from
mics, poor mic technique, poor filtering and equalization out there, and crappy tinny little speakers
pointed at the floor.? It is a good idea to work on cleaning up the repeaters audio quality, but for voice
audio, it is better to concentrate on a PL notch in the RCVR and an IF filter that does not ring as with
a dedicated P25 digital station.? Perhaps 3-6 db compression and no more than that, then repeat
audio short of clipping.? The compression must be off when sweeping and comparing the input and
output equalization, but only those who work on improving their own will notice.
I still have some good condition Motrac speakers with AlNiCo magnets, but I bet not many have them anymore.?
I use them over and over again in mobile installations and around the shack for FM radios.? You can't get the
replacement speaker anymore though.? I have wondered how to re-cone them.? I have tried in vain to find
a replacement that even fits, let alone sounds as good.
After the Motrac and Micor, it seems everything after that got more and more compromised.?
Agree about HIFI SSB.? If you actually have a RCVR with a speaker that is HiFi, you find these people bass
boosting trying to make voice energy at 50 hz that it is completely unintelligible and you are left with the
impression of a 600lb hog grunting.? Also, most guys rarely generate much energy above 2400hz and even
women and little children don't either unless they want to shriek.? The only reason to go out to 3000hz is to
avoid ringing, but voice audio will rarely exceed 2800hz unless you are pushing something else besides voice.
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Re: Repeater Horror Stories
At 10/25/2022 06:40 AM, you wrote:
This is very ingenuous... You get my Award for the effort.
I think you mean genius
I think you mean ingenious
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Re: QUANTAR VHF Audio Interface...
At 10/24/2022 06:59 PM, you wrote: When I first saw the question, I scratched my head and went on to other things. It looked wierd. Then I remembered why.
If you are actually going to feed audio up to 6 khz. to the modulator, where does it actually go after that???
Even if you reduce the deviation and the pre-emphasis to keep the bandwidth down to a normal FM channel, anyone trying
to recieve it will have to modify the reciever so it won't squelch itself out trying to recieve. Literally hundreds of 440 repeaters in this area have audio responses approaching 6 kHz, & no one has had to modify their RXs to hear them. Sounds confusing, but the typical 16kF3 reciever needs to have a 20khz bandwidth in the IF to allow for drift and to prevent
the reciever from squelching out. The back-end was made to roll off above 3khz to the speech amp and the squelch amp will
be listening for noise above that to keep the squelch closed. Much above, actually. The last squelch circuit I looked at actually responded best to noise around 10-20 kHz, so 6 kHz won't really affect it much If this is for a link radio on the 2m ham band, how were you planning to keep the bandwidth to a normal ham channel? If this is
for a ham voice repeater, everyone will have to modify their radios to use it. Nope - see above. Granted on 2 meters with 15 kHz channel spacing some modifications to the standard are needed. I find that by keeping the deviation down to, say 4.2 kHz peak, the occupied BW is sufficiently controlled without losing S/N. 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 NO6B
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Re: QUANTAR VHF Audio Interface...
On the GE MASTR PRO, there are a couple of capacitors you need to remove to get the perfectly audio flat.?? This applies to the MASTR imperial as well.? The caps are C-16 and optionally, C-21.??
Andy
I agree with you, Bob, that most important of anything is a post limiter filter that will roll off as steeply as practical above 3KHz, with a sharp knee so that below say 2800 is not affected. Seems that the problem usually lies in that the usual analog receiver de-emphasis and transmitter pre-emphasis may match overall, but often have a peak audio pass through around the mid point of 1500 cps with roll off below even at pass through below 400 and above 2200 cps. The worst in our somewhat limited experience was the GE Mastr Pro, and the best flattness, the Kenwood TK8180. I suppose in an ideal setup an audio equilizer is inserted to get flat repeater throughput from say 200-3000 cps and you set the dev pot for the same dev in and out at around 2500 cps instead of 1000 cps, otherwise the dev limiter will clip the higher frequencies starting above maybe 2000 cps on full deviation, including squelch noise, thus making the repeater appear to have a lack of highs, not caused by the roll off in the splatter filter, rather selectively clipping at the higher frequencies.
John W1GPO
> On 10/25/2022 12:47 PM Bob Dengler via <no6b=[email protected]> wrote:
>
>?
> At 10/25/2022 05:35 AM, you wrote:
> >I've done flat audio in the pass but always use a RC filter to roll off above 3-4khz...no need to go higher as the energy in that area is QUITE low and not needed..I've made GE MVPs rptrs with flat audio and FM on the exciter where it coupled to an ACC RC850 passed Alinco Digital with no problem...had to back off the radio deviation a little...it would clip thru the rptr at high deviation..
> >
> >I've ran Quantars in flat audio mode using the RSS settings and found great results..but I would never use 5kHz audio b/w...the Carson rule of B/W tells me not to anyway ..it exceeds 16-20K easily.
>
> The above two paragraphs contradict each other: if the spectral energy above 3 kHz is "QUITE low", then that spectrum will not be deviating the TX anywhere near 5 kHz, hence the BW will not be "16-20K".? This is probably why I can tune my TYT TH-9800 15 kHz away from the W6MEP 147.240 repeater & listen to a repeater on 147.225 some 50+ miles away with no interference.? In the end that is all that matters.
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> Bob NO6B
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Re: QUANTAR VHF Audio Interface...
I agree with you, Bob, that most important of anything is a post limiter filter that will roll off as steeply as practical above 3KHz, with a sharp knee so that below say 2800 is not affected. Seems that the problem usually lies in that the usual analog receiver de-emphasis and transmitter pre-emphasis may match overall, but often have a peak audio pass through around the mid point of 1500 cps with roll off below even at pass through below 400 and above 2200 cps. The worst in our somewhat limited experience was the GE Mastr Pro, and the best flattness, the Kenwood TK8180. I suppose in an ideal setup an audio equilizer is inserted to get flat repeater throughput from say 200-3000 cps and you set the dev pot for the same dev in and out at around 2500 cps instead of 1000 cps, otherwise the dev limiter will clip the higher frequencies starting above maybe 2000 cps on full deviation, including squelch noise, thus making the repeater appear to have a lack of highs, not caused by the roll off in the splatter filter, rather selectively clipping at the higher frequencies.
John W1GPO
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On 10/25/2022 12:47 PM Bob Dengler via groups.io <no6b@...> wrote:
At 10/25/2022 05:35 AM, you wrote:
I've done flat audio in the pass but always use a RC filter to roll off above 3-4khz...no need to go higher as the energy in that area is QUITE low and not needed..I've made GE MVPs rptrs with flat audio and FM on the exciter where it coupled to an ACC RC850 passed Alinco Digital with no problem...had to back off the radio deviation a little...it would clip thru the rptr at high deviation..
I've ran Quantars in flat audio mode using the RSS settings and found great results..but I would never use 5kHz audio b/w...the Carson rule of B/W tells me not to anyway ..it exceeds 16-20K easily. The above two paragraphs contradict each other: if the spectral energy above 3 kHz is "QUITE low", then that spectrum will not be deviating the TX anywhere near 5 kHz, hence the BW will not be "16-20K". This is probably why I can tune my TYT TH-9800 15 kHz away from the W6MEP 147.240 repeater & listen to a repeater on 147.225 some 50+ miles away with no interference. In the end that is all that matters.
Bob NO6B
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Kevin Custer
Jack Mcelyea/n4jem
Ken Arck AH6LE
Burt K6OQK