Re: some simulcast questions
Before you do anything else, define what "better coverage" means.
Do the field units have trouble hearing the repeater output?
Do the field units have trouble being heard by the repeater?
Or do both situations apply?
Are the field units having problems with mobile radios, portable radios, or both?
The existing coverage needs to be mapped and should be compared to a predicted coverage map based on the current equipment (radio/feedline/antenna). You need to know the area that the system "should" cover.
On-line coverage prediction systems exist and can give a rough idea of system coverage. Talk-out(TX to field) and Talk-in(field to RX) should be considered for both mobiles and portables, they are not the same.
The existing equipment, both fixed end and in the field, needs to be checked to see if everything is meeting spec.
Next determine the desired area of coverage and show that on a map along with the current coverage.
Then start asking more questions:
Is it necessary to have the system act as a single repeater over the entire coverage area or can it be split up into smaller regions?
Is the current repeater location at the best available location to cover the area in question?
Is there interference of any sort on the existing frequencies in use?
If the problem is talk-out, can the system be licensed to use a different antenna or higher TX power output?
If the problem is talk-in, consider multiple receiver sites with or without receiver voting.
Since this is a public safety system, I would strongly suggest engaging the services of a professional. Designing something like this by the seat of your pants is just asking for trouble.
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On 9/9/2018 6:25 PM, Jed Barton jed@... [Repeater-Builder] wrote: Hey guys,
OK, so here we go. I've been given a challenge, to help an fd get
better coverage. We've gotta take this 1 step at a time. So right
now they are on vhf.
They have a single site repeater. We're thinking simulcast right now.
The repeater is a quantar. So, keeping the current repeater in its
current home, let's ay we add 1 more to the mix, doing a simulcast,
what would we need?
This is my 1st simulcast adventure, and i actually wanna learn more
about it to help them out.
Thanks,
Jed
------------------------------------
Posted by: Jed Barton <jed@...>
------------------------------------
------------------------------------
Yahoo Groups Links
|
Re: some simulcast questions
I know we are talking about the technical aspects of this here. Since
this is in the public service band and not amateur, you may run into
some work with licenses. I haven't been there, but just something to
think about with this before you get too carried away.
A bit of information that may help, is it the transmit or receive that
is the weak part of the repeater? Guessing it seems to be the repeater
hearing the field units.
Mick - W7CAT
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----- Original Message -----
From: "Jed Barton jed@... [Repeater-Builder]"
To: Repeater-Builder@...
Sent: Sunday, September 09, 2018 05:06:41 PM
Subject: Re: [Repeater-Builder] some simulcast questions
> exactly. So, my gut is telling me, make the quantar go away. It's
> rather old and they don't even make them any more. For voters, i was
> thinking the jps voters. As for a repeater, not sure what to go with.
> Any ideas?
>
> On 9/9/18, Joe k1ike_mail@... [Repeater-Builder]
> wrote:
> > To start with:
> >
> > For transmit, both sites would need a high stability oscillator,
> > possibly GPS disciplined.
> >
> > Identical equipment at both sites would make things easier.
> >
> > For receive, both transmit sites need to broadcast the same audio at a
> > specific time. If you are going to receive at both sites you would
need
> > a way to vote or chose which site audio to use at a particular
point in
> > time.
> >
> > You would need a link between both sites, preferably an RF link.
> > Internet linking can be done but makes timing extremely difficult and
> > expensive. This link would carry the receive audio between the sites.
> >
> > I assume that these are going to be conventional FM analog repeaters.
> > Overlap areas need to be planned and managed by audio delays. There
> > will be areas that will have audio that is far from perfect.
> >
> > Joe
> >
> >
> > On 9/9/2018 6:25 PM, Jed Barton jed@...
[Repeater-Builder] wrote:
> >> Hey guys,
> >>
> >> OK, so here we go. I've been given a challenge, to help an fd get
> >> better coverage. We've gotta take this 1 step at a time. So right
> >> now they are on vhf.
> >> They have a single site repeater. We're thinking simulcast right now.
> >> The repeater is a quantar. So, keeping the current repeater in its
> >> current home, let's ay we add 1 more to the mix, doing a simulcast,
> >> what would we need?
> >> This is my 1st simulcast adventure, and i actually wanna learn more
> >> about it to help them out.
> >>
> >> Thanks,
> >> Jed
> >
>
--
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Be sure to check out all the latest at our web site
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Re: some simulcast questions
Joe KC2IRV has done some great work with the Micronode RTCMs in a voted simulcasted setup. Take a look at his YouTube channel (KC2IRV)?
?
Hey guys,
OK, so here we go. I've been given a challenge, to help an fd get
better coverage. We've gotta take this 1 step at a time. So right
now they are on vhf.
They have a single site repeater. We're thinking simulcast right now.
The repeater is a quantar. So, keeping the current repeater in its
current home, let's ay we add 1 more to the mix, doing a simulcast,
what would we need?
This is my 1st simulcast adventure, and i actually wanna learn more
about it to help them out.
Thanks,
Jed
|
Re: some simulcast questions
Many years past, some Schaumberg IL Motorola Engineers made a
field recording of a simulcast paging system in various states of
alignment.
The demonstrated audio included two transmitters in a well aligned
simulcast system. One transmitter was then moved off frequency
to a number of different places, the distortion became audible.
The transmitters were reset to the same frequency, next the audio
delay values were modified, no longer synchronized... a different type
of distortion became audible.
Audio frequency equalization and (group) delay is considered an
important part of a simulcast system. These parameters were varied
with the example system, a third and forth type of distortion became
audible.
Stability is another important consideration... an interesting helicopter blade
beat note occurs when two transmitter frequencies are moving in relation to
each other.
In a modern Simulcast System, management of all the above
requirements is mostly done in specialized (PC) software, over
regular intervals. In older times, simulcast management required
much more operator/owner think power/time.
In each of the above described distortion examples, the resultant
audio was totally different from any other source. Even worse
when two or more parameters were not correct.
With the advent of Ebay, GPS Technology and system upgrades, a lot
of very useful hardware can be found. Over to Ebay, search CONVEX
C20 AUDIO EQUALIZER and see what was once a whole lot of
money being offered for $25 each, Having some of these cards
around can be very useful in a budget minded simulcast system
having decent quality commercial hardware in play.
Then it's on you to make it work well.... based of course on
reasonable expectations.
cheers
Dr House
|
Re: some simulcast questions
Hey guys,
They have a single site repeater. We're thinking simulcast
right now. The repeater is a quantar. So, keeping the current
repeater in its current home, let's ay we add 1 more to the
mix, doing a simulcast, what would we need? The first thing is to write a specifications sheet, meaning a signal strength overlaid map that shows the existing coverage area and the difference or changes made by adding one or more additional transmitters. All this determines the hardware options that drive the resultant as-built system. This is my 1st simulcast adventure, and i actually wanna
learn more about it to help them out. Thanks, Jed You would start with a logical game plan first. Simulcast Systems don't always have to be really complicated and they don't have to have all the same brand and model equipment. That's what the learning curve is about... Another big deal is the financial side of the equation... if you're a Public Safety system where money seems to be spent like drunken sailors in port, the path taken is a whole lot different compared to a couple of smart thinking private two-way radio people... also a reasonable Amateur (Ham) System. There are many types of Simulcast Systems... so a proper game plan at the start saves time, money and hair color or quantity there of. Just tossing out a "you need this or that" is probably not the optimal first path. Cheers, Clairol Natural Instincts s.
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Re: some simulcast questions
Jed,
You should keep all the transmitters the same. In simulcast the main concerns will be in the overlap areas. The issues are more phase related than frequency offsets and audio deviation differences, although both of those are important as well. Most all simulcast systems are locked to a very stable time base to keep frequencies the same. The systems that I work with are GPS disciplined and the exciters are DSP based.
In the overlap areas ( area where the user can hear both or many transmitters ) phase distortion can make the area unusable. This is why it is very important in a simulcast system to carefully design the RF coverage. More power and high gain antennas mounted high are not always the best solution for simulcast. Simulcast concerns are very different between analog and digital systems.
On analog it helps to use the same service monitor to set the frequencies and deviations, but if you are using a high stability time base at the transmitters then this is not so important.
I am trying to just give some pointers. I can move to a different email if you want more in depth explanations.
The systems that I design, build and maintain consists of up to 250 high power transmitters located in the same state all simulcast.
73,
Ken, N4KCD
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Re: some simulcast questions
If they are analog and transmit PL, and have overlapping coverage, you¡¯ll hear a buzz in those areas unless the PL on both signals is in-phase at the receiver. That¡¯s the extent of my simulcast experience.
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On Sep 9, 2018, at 3:25 PM, Jed Barton jed@... [Repeater-Builder] <Repeater-Builder@...> wrote:
Hey guys,
OK, so here we go. I've been given a challenge, to help an fd get
better coverage. We've gotta take this 1 step at a time. So right
now they are on vhf.
They have a single site repeater. We're thinking simulcast right now.
The repeater is a quantar. So, keeping the current repeater in its
current home, let's ay we add 1 more to the mix, doing a simulcast,
what would we need?
This is my 1st simulcast adventure, and i actually wanna learn more
about it to help them out.
Thanks,
Jed
------------------------------------
Posted by: Jed Barton <jed@...>
------------------------------------
------------------------------------
Yahoo Groups Links
|
Re: some simulcast questions
Is it an issue where the repeater is not able to hear the remote users? If so use a voting system. All receivers should be the same make and model so that their audio characteristics are the same.? RF link preferred but You can use a non public IP network if desired. It will cost you more monthly but you can get QOS to not drop any audio packets. You will also have to have good vocoders as well.?
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On Sep 9, 2018, at 5:25 PM, Jed Barton jed@... [Repeater-Builder] < Repeater-Builder@...> wrote:
?
Hey guys,
OK, so here we go. I've been given a challenge, to help an fd get
better coverage. We've gotta take this 1 step at a time. So right
now they are on vhf.
They have a single site repeater. We're thinking simulcast right now.
The repeater is a quantar. So, keeping the current repeater in its
current home, let's ay we add 1 more to the mix, doing a simulcast,
what would we need?
This is my 1st simulcast adventure, and i actually wanna learn more
about it to help them out.
Thanks,
Jed
|
Re: some simulcast questions
exactly. So, my gut is telling me, make the quantar go away. It's rather old and they don't even make them any more. For voters, i was thinking the jps voters. As for a repeater, not sure what to go with. Any ideas? On 9/9/18, Joe k1ike_mail@... [Repeater-Builder] <Repeater-Builder@...> wrote: To start with:
For transmit, both sites would need a high stability oscillator,
possibly GPS disciplined.
Identical equipment at both sites would make things easier.
For receive, both transmit sites need to broadcast the same audio at a
specific time. If you are going to receive at both sites you would need
a way to vote or chose which site audio to use at a particular point in
time.
You would need a link between both sites, preferably an RF link.
Internet linking can be done but makes timing extremely difficult and
expensive. This link would carry the receive audio between the sites.
I assume that these are going to be conventional FM analog repeaters.
Overlap areas need to be planned and managed by audio delays. There
will be areas that will have audio that is far from perfect.
Joe
On 9/9/2018 6:25 PM, Jed Barton jed@... [Repeater-Builder] wrote:
Hey guys,
OK, so here we go. I've been given a challenge, to help an fd get
better coverage. We've gotta take this 1 step at a time. So right
now they are on vhf.
They have a single site repeater. We're thinking simulcast right now.
The repeater is a quantar. So, keeping the current repeater in its
current home, let's ay we add 1 more to the mix, doing a simulcast,
what would we need?
This is my 1st simulcast adventure, and i actually wanna learn more
about it to help them out.
Thanks,
Jed
|
Re: some simulcast questions
The easiest approach might be for the far repeater to receive the near repeater then retransmit the message.
Set the retransmit delay on each repeater different so that they will not all be transmitting at the same time.
To get true simulcast the repeater transmit oscillators have to be phase synchronized IIRC.
if the problem is that the field units cannot get back to the repeater, but, can hear it, you might want to try satellite receivers.
I have never done this so this is just theory.
73
Glenn
WB4UIV
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On 9/9/2018 6:25 PM, Jed Barton jed@... [Repeater-Builder] wrote: Hey guys,
OK, so here we go. I've been given a challenge, to help an fd get
better coverage. We've gotta take this 1 step at a time. So right
now they are on vhf.
They have a single site repeater. We're thinking simulcast right now.
The repeater is a quantar. So, keeping the current repeater in its
current home, let's ay we add 1 more to the mix, doing a simulcast,
what would we need?
This is my 1st simulcast adventure, and i actually wanna learn more
about it to help them out.
Thanks,
Jed
------------------------------------
Posted by: Jed Barton <jed@...>
------------------------------------
------------------------------------
Yahoo Groups Links
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
|
Re: some simulcast questions
To start with:
For transmit, both sites would need a high stability oscillator, possibly GPS disciplined.
Identical equipment at both sites would make things easier.
For receive, both transmit sites need to broadcast the same audio at a specific time. If you are going to receive at both sites you would need a way to vote or chose which site audio to use at a particular point in time.
You would need a link between both sites, preferably an RF link. Internet linking can be done but makes timing extremely difficult and expensive. This link would carry the receive audio between the sites.
I assume that these are going to be conventional FM analog repeaters. Overlap areas need to be planned and managed by audio delays. There will be areas that will have audio that is far from perfect.
Joe
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Show quoted text
On 9/9/2018 6:25 PM, Jed Barton jed@... [Repeater-Builder] wrote: Hey guys,
OK, so here we go. I've been given a challenge, to help an fd get
better coverage. We've gotta take this 1 step at a time. So right
now they are on vhf.
They have a single site repeater. We're thinking simulcast right now.
The repeater is a quantar. So, keeping the current repeater in its
current home, let's ay we add 1 more to the mix, doing a simulcast,
what would we need?
This is my 1st simulcast adventure, and i actually wanna learn more
about it to help them out.
Thanks,
Jed
|
Hey guys,
OK, so here we go. I've been given a challenge, to help an fd get
better coverage. We've gotta take this 1 step at a time. So right
now they are on vhf.
They have a single site repeater. We're thinking simulcast right now.
The repeater is a quantar. So, keeping the current repeater in its
current home, let's ay we add 1 more to the mix, doing a simulcast,
what would we need?
This is my 1st simulcast adventure, and i actually wanna learn more
about it to help them out.
Thanks,
Jed
|
Re: A Poor Man's Tracking Generator
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?
Yes, that would be fine. If you do, please use my main email address, which is wa6jbd(at)verizon(dot)net.
I don't always pay close attention to this one.
Mel - WA6JBD
--------------------------------------------
On Mon, 9/3/18, Pierre Martel petem001@... [Repeater-Builder] <Repeater-Builder@...> wrote:
Subject: Re: [Repeater-Builder] A Poor Man's Tracking Generator
To: Repeater-Builder@...
Date: Monday, September 3, 2018, 7:25 AM
thats pretty interresting. will read a bit
more on this.
Can I contact
you if I have a specific question that would not fit in the
list?
Le?lun. 3
sept. 2018 ¨¤?02:34, Mel Swanberg wa6jbd@...
[Repeater-Builder] <Repeater-Builder@...>
I guess a lot of the solution depends on what's
on hand, and what one's skill and motivational levels
are. For me, I had exclusive access to an HP VNA for many
years. I was even allowed to keep the thing at home,
otherwise it would wind up on a pallet outside on the
Purchasing Departments loading dock awaiting auction. But at
some point, it had to be returned, leaving a gaping hole in
the test rack, and an even larger hole in my 10 GHz sweep
capabilities.
I found myself highly motivated to figure something out.
In an evening, just to prove to myself it could be done, I
cobbled together a tracking generator for the HP8566B that
incorporated the instruments 1st LO output, a fixed transfer
oscillator, a mixer, and a filter. Using the SA's B-A
math function, I was even able to normalize the trace. The
salient point here is, if you need a tracking generator, and
already have a spectrum analyzer, start by looking at the
SA's 1st LO. That's the one that's sweeping
across the set span on the display. It's usually ported
out to the front or rear panels. Read the manual, understand
what the frequency arrangements are in the instrument, and
figure out what it takes to mix the 1st LO up to the
SA's input frequency. It doesn't have to cover the
entire range of the instrument, just the particular bands
you're interested in sweeping.
It was amazingly easy with the 8566B. Other instruments
might not be quite as easy.
Mel - WA6JBD
--------------------------------------------
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Shorted at DC is not shorted at RF ... this is all about transmission line theory. Why it is called theory is just the context of the language. Figure that gravity is still only a theory, but yet a different context.
|
John, What are you wanting to do at the bottom of the coax? If you are combining 2 transmitters that will require a duplexer as well. If you are connecting 2 transceivers the receivers front ends are going to get knocked about when the other transceiver transmits. 73¡¯²õ Nic VK2KXN / VK5ZAT ?
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From: Repeater-Builder@...
Sent: Monday, 10 September 2018 12:34 AM
To: Repeater-Builder@...
Subject: Re: [Repeater-Builder] Same feedline? ? I'd suggest using a Diplexer, instead of a coax T connector.? That way, you don't have to worry about the problem of what kind of impedance the un-used antenna will have on the in-use antenna.? There are duplexers that will separate HF thru 6 meters, from 2 meters. ? ? Is it possible to feed two folded dipoles, 1 on 2m and the other on 6m, with the same coax and t connector at the top? I see some commercial dual band 2m/70cm ones that do this and it's a similar principal to a fan dipole where only the resonant antenna would let the RF pass. This is for repeaters on the tower so I wanted to tap this groups thoughts.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity. ?
|
Re: Kenwood Mobile Radio Aux PTT - Needs to be enabled???
Yes, there is absolutely programming to turn aux PTT on. Usually under "extended function" or something similar.
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On 9/9/2018 2:55 PM, Skyler F electricity440@... [Repeater-Builder] wrote: I'm working on a project with a
900MHz repeater, 2 meter remote base, and 70cm remote base.
Kenwood TK-941 , Kenwood TK-880 and Kenwood TK-7180. I am using the
accessory connector ( 15 pin Molex) installed on these radios.
So the radios that I got for the project almost all do not have a
functioning auxiliary PTT. I see 4.8-5V on the PTT line, but when I ground
it, nothing happens. I traced the wire to the pin on the microprocesser
chip, and the AUX PTT input is for sure grounded and going to 5V when I
short the pin on the Accessory connector.
NONE of these radios have functional auxiliary PTT, and ALL of the radios
have functioning MIC PTT. Does anybody know if there is a software setting
to enable / disable this aux PTT on the models listed above?
The ONLY radio that works, is the TK-941 that is supposed to be a receiver
for the 900MHz repeater. This one does not have a DEAD PTT, and since the
microprocessor chip is in the control head, swapping out the control heads,
and reprogramming the codeplug solved my problem with the TK-941, but I
still have 2 other radios with bad PTT inputs...
If not, I am sort of putting bets that someone before I messed with these
radios hooked 13V up to the PTT input line and blew out the pin on the
microprocesser chip. I see some clamping diodes for input spike protection
on the service manual, but I'm sure a high current supply could have blown
right through these clamping diodes.
Anybody had this problem with Kenwood Mobile radios?? Is this a software
switch or likely a hardware failure?? I know on the 941 it must have been a
hardware failure with the success of replacing control head, but not sure
on the other radios?
Thanks!
Skyler
|
What impedance does a SHORTED folded dipole @2m present to 6m (or 6 to 2 for that matter) Interesting.... 73 Dean
?
John,
I'd suggest using a Diplexer, instead of a coax T connector.? That way, you don't have to worry about the problem of what kind of impedance the un-used antenna will have on the in-use antenna.? There are duplexers that will separate HF thru 6 meters, from 2 meters.
73, Gary? W3DTN
?
Is it possible to feed two folded dipoles, 1 on 2m and the other on 6m, with the same coax and t connector at the top? I see some commercial dual band 2m/70cm ones that do this and it's a similar principal to a fan dipole where only the resonant antenna would let the RF pass. This is for repeaters on the tower so I wanted to tap this groups thoughts.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
|
Kenwood Mobile Radio Aux PTT - Needs to be enabled???
I'm working on a project with a?
900MHz repeater, 2 meter remote base, and 70cm remote base.?
Kenwood TK-941 , Kenwood TK-880 and Kenwood TK-7180. I am using the accessory connector ( 15 pin Molex) installed on these radios.?
So the radios that I got for the project almost all do not have a functioning auxiliary PTT. I see 4.8-5V on the PTT line, but when I ground it, nothing happens. I traced the wire to the pin on the microprocesser chip, and the AUX PTT input is for sure grounded and going to 5V when I short the pin on the Accessory connector.?
NONE of these radios have functional auxiliary PTT, and ALL of the radios have functioning MIC PTT. Does anybody know if there is a software setting to enable / disable this aux PTT on the models listed above?
The ONLY radio that works, is the TK-941 that is supposed to be a receiver for the 900MHz repeater. This one does not have a DEAD PTT, and since the microprocessor chip is in the control head, swapping out the control heads, and reprogramming the codeplug solved my problem with the TK-941, but I still have 2 other radios with bad PTT inputs...
If not, I am sort of putting bets that someone before I messed with these radios hooked 13V up to the PTT input line and blew out the pin on the microprocesser chip. I see some clamping diodes for input spike protection on the service manual, but I'm sure a high current supply could have blown right through these clamping diodes.?
Anybody had this problem with Kenwood Mobile radios?? Is this a software switch or likely a hardware failure?? I know on the 941 it must have been a hardware failure with the success of replacing control head, but not sure on the other radios?
Thanks! Skyler
|
G.E. MIII 450-470 conversion question
Guys,
I have a 450-470 MASTR III base/repeater that I'm trying to program in the 440 amateur band, and it won't program below 450.025.? This is an older MIII without the racing stripes, System Module is a 19D902590G3.? The SM PC board is a 19D903771G1 Rev. E.
I'm sure there is a way to do it, but personally, I don't have any experience with 450-470 MIII's.? I tried programming the "image" frequency, and that didn't work.
So can anybody tell me what the secret is?
By the way, a couple of weeks ago I posted an inquiry about converting a 380-400 MHz MIII to the 420-450 band.? Didn't get any conversion suggestions, so I've been working on a conversion project, and have had pretty good luck.? Once I finish that project, I'll write it up for Repeater-Builder.
Thanks es 73, Gary? W3DTN
|
Since the question was asking about feeding antennas on the tower rather than separating signals at the bottom of the feedline, the use of a diplexer would require that the diplexer and it's connections be installed inside a suitable weatherproof enclosure on the tower. Also not all diplexers are created equal; I would avoid any diplexer with coaxial leads and stay with a connector only type. Also consider the total amount of RF signals that will be passing through the diplexer and don't forget to leave some headroom for reflected power.
This case would actually require the use of two diplexers; one in a suitable enclosure on the tower and the other at the equipment end of the feedline.
Using a coaxial T connector simplifies weatherproofing however the use of the folded dipole antennas would most likely require critical lengths of coax cable between the T and the antennas. These critical lengths might also need to be something other than 50 ohm coax.
The fan dipole is not a good comparison since in the case of the fan dipole the wire making up each side of the dipole is either resonant or non-resonant and the antenna is an open circuit at DC and is resonant only over a relatively small bandwidth. The folded dipole antenna is a DC short circuit that has a wide bandwidth over which it can be resonant.
VNA and Smith charts anyone?
Milt
N3LTQ
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On 9/9/2018 10:34 AM, Gary HENDRICKSON w3dtn@... [Repeater-Builder] wrote: John,
I'd suggest using a Diplexer, instead of a coax T connector.? That way, you don't have to worry about the problem of what kind of impedance the un-used antenna will have on the in-use antenna.? There are duplexers that will separate HF thru 6 meters, from 2 meters.
73, Gary? W3DTN
On Saturday, September 8, 2018 4:19 PM, "John Rudolph john@... [Repeater-Builder]" <Repeater-Builder@...> wrote:
Is it possible to feed two folded dipoles, 1 on 2m and the other on 6m, with the same coax and t connector at the top? I see some commercial dual band 2m/70cm ones that do this and it's a similar principal to a fan dipole where only the resonant antenna would let the RF pass. This is for repeaters on the tower so I wanted to tap this groups thoughts.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
|
Pierre Martel
Nic McLean