• To anyone looking to acquire commercial radio programming software:

    Please do not make requests for copies of radio programming software which is sold (or was sold) by the manufacturer for any monetary value. All requests will be deleted and a forum infraction issued. Making a request such as this is attempting to engage in software piracy and this forum cannot be involved or associated with this activity. The same goes for any private transaction via Private Message. Even if you attempt to engage in this activity in PM's we will still enforce the forum rules. Your PM's are not private and the administration has the right to read them if there's a hint to criminal activity.

    If you are having trouble legally obtaining software please state so. We do not want any hurt feelings when your vague post is mistaken for a free request. It is YOUR responsibility to properly word your request.

    To obtain Motorola software see the Sticky in the Motorola forum.

    The various other vendors often permit their dealers to sell the software online (i.e., Kenwood). Please use Google or some other search engine to find a dealer that sells the software. Typically each series or individual radio requires its own software package. Often the Kenwood software is less than $100 so don't be a cheapskate; just purchase it.

    For M/A Com/Harris/GE, etc: there are two software packages that program all current and past radios. One package is for conventional programming and the other for trunked programming. The trunked package is in upwards of $2,500. The conventional package is more reasonable though is still several hundred dollars. The benefit is you do not need multiple versions for each radio (unlike Motorola).

    This is a large and very visible forum. We cannot jeopardize the ability to provide the RadioReference services by allowing this activity to occur. Please respect this.

crosstalk in digital

Status
Not open for further replies.

jen02

Member
Joined
Jul 24, 2015
Messages
11
we currently having a problem with crosstalk and most of the users complain about it.

actually i dont have an idea if the portables has the problem if it really switch automatically in different channel or if it the system. We invite some technical that could help us and they said that the receive and transmit is reverse and the other two duplexer has low power than the other two. Before we invite other people but they didnt tell us this thing maybe because they supplied us the duplexer. And now they recommend us to reverse the frequency and replace the duplexer. Im just wondering if this is really the cause of the problem or if the recommendation is really the solution to the problem?

the setup is there's 4 repeater in the same place with duplexer with one antenna each.

sample frequency

tx rx
434.025 429.025
427.35 422.35
436.025 431.025
439.55 431.025

439.5 432.5


Thanks
 

N1GTL

Member
Database Admin
Joined
Jun 14, 2005
Messages
970
Location
CT
I'm kind of confused as to what your asking. What do you mean "crosstalk"?

If you've had a radio shop in, I would hope they tested the output power of each repeater and measured the signal required to key it up (sensitivity). Once those things are verified, measure those same things with the duplexer connected. If the repeaters and duplexers are the same make and model, the output power should be the same. If not, the duplexers may not be tuned correctly. Measure the SWR between the duplexer and the transmitter using dummy load in place of an antenna. If the duplexer is perfect, there should be nothing reflected. Move to the feed line and antennas.

Also, I am not sure where you are but those would be some oddball frequencies here. The first 3 are 5 mhz splits which are normal. The next two you list are 8mhz and 7 mhz splits?
 

jen02

Member
Joined
Jul 24, 2015
Messages
11
i mean they hear other channel but the selector is in their own group or channel..

they measured it but not with dummy load, they used the existing cables and antennas when measuring the swr and power. The output power of the two repeater is 25 watts while its swr is 1.5 and the other two is 10 watts and the swr is 2.1.

So if in case that the repeater side has the problem does that mean that it can cause that kind of problem?
 
Last edited:

jen02

Member
Joined
Jul 24, 2015
Messages
11
i mean they hear other channel but the selector is in their own group or channel..

they measured it but not with dummy load, they used the existing cables and antennas when measuring the swr and power. The output power of the two repeater is 25 watts while its swr is 1.5 and the other two is 10 watts and the swr is 2.1.

So if in case that the repeater side has the problem does that mean that it can cause that kind of problem?
 

jen02

Member
Joined
Jul 24, 2015
Messages
11
the separation distance of each antenna is not that big maybe 3 to 5 feet apart, the tower is not that high so spacing is a problem
 

TampaTyron

Beep Boop, Beep Boop
Premium Subscriber
Joined
Feb 1, 2010
Messages
1,091
Location
Phoenix, AZ
Are your color codes and talkgroups on different numbers? Like in the analog days, we used different PL tones to cover up poor rf engineering...... sounds lime you have a mess on your hands. What part of the world are you in? TT
 

jen02

Member
Joined
Jul 24, 2015
Messages
11
yes they are, each repeater has different color codes as well as group id. In portables, channel color code is selected according to the repeaters color code as well as the time/repeaters slot. Im not an engineer so i cant tell really tell everything i just based on what i saw , and i said we hire consultant to help us and i just like to verify if that's really the problem.
 

buddrousa

Member
Premium Subscriber
Joined
Jan 5, 2003
Messages
11,221
Location
Retired 40 Year Firefighter NW Tenn
the separation distance of each antenna is not that big maybe 3 to 5 feet apart, the tower is not that high so spacing is a problem

Then the bad news is you are going to have problems until you get the proper antenna spacing or move the other repeaters to other sites. The other thing you can do is buy a RX TX combiner set it up proper and put all the repeaters on the same antenna. I will also point out look at the cell towers near you they cover a 360 path at one height then about 40 to 60 foot down the tower is another group of antennas this is so they do not receive interference from the set of antennas above.
 
Last edited:

902

Member
Joined
Nov 7, 2003
Messages
2,620
Location
Downsouthsomewhere
Jen02,

I have experience in identifying and mitigating mixing products - which is what this sounds like to me. Before I (or any of our other folks who've worked on this kind of thing) can drill into the issue, I need more information:

Where are you? US or Canada?
Is this an amateur radio, public safety, or industrial system?
What data protocol are you using? Have you tried using different NAC or color code values for each system?
What types of repeaters are you using? - What is their power level and receiver sensitivity?
Are you using IMD suppression panels (circulator) between your transmitter and duplexer?
Are you using a harmonic filter directly after the circulator?
Does your site include rusty, corroded, or oxidized hardware?
What kind of duplexers are you using (make and model, please - or are you combining your transmitters and using a receiver multicoupler)?
Your separation - is that vertical or horizontal (or a combination of)?
What kind of coaxial cable are you using from the duplexers to the antennas?
What kind of coaxial cable are you using from the repeaters to the duplexers?
What kind of antennas are you using (and proximity to tower, if applicable)?

I know these are a lot of questions, but all of this information is relevant to the issue and possible solution.
 

phillmobile

Member
Joined
Oct 12, 2009
Messages
253
Location
bridlington, uk

mikewazowski

Forums Manager/Global DB Admin
Staff member
Forums Manager
Joined
Jun 26, 2001
Messages
13,459
Location
Oot and Aboot
I will also point out look at the cell towers near you they cover a 360 path at one height then about 40 to 60 foot down the tower is another group of antennas this is so they do not receive interference from the set of antennas above.

Sorry but this is not the case.

The only time we locate antennas further down the tower is to focus on an area closer in to the tower.

Since the OP is running different colour codes on each repeater, antenna spacing is more than likely not the issue.
 

jen02

Member
Joined
Jul 24, 2015
Messages
11
Jen02,

I have experience in identifying and mitigating mixing products - which is what this sounds like to me. Before I (or any of our other folks who've worked on this kind of thing) can drill into the issue, I need more information:

Where are you? US or Canada?
Is this an amateur radio, public safety, or industrial system?
What data protocol are you using? Have you tried using different NAC or color code values for each system?
What types of repeaters are you using? - What is their power level and receiver sensitivity?
Are you using IMD suppression panels (circulator) between your transmitter and duplexer?
Are you using a harmonic filter directly after the circulator?
Does your site include rusty, corroded, or oxidized hardware?
What kind of duplexers are you using (make and model, please - or are you combining your transmitters and using a receiver multicoupler)?
Your separation - is that vertical or horizontal (or a combination of)?
What kind of coaxial cable are you using from the duplexers to the antennas?
What kind of coaxial cable are you using from the repeaters to the duplexers?
What kind of antennas are you using (and proximity to tower, if applicable)?

I know these are a lot of questions, but all of this information is relevant to the issue and possible solution.


Location: Southeast Asia
Oil Refinery
We used color code and its different in each repeater
Repeater:Mototrbo R8200
I only a saw a duplexer in each repeater, i didnt take note of the model but it has four cyclinder tube i dont know the name
Antenna Separation: Horizontal
Cable used from duplexer to antenna : Heliax cable
Cable used repeater to duplexer: mixed the other repeater has rg-8 cable and the other has thin coaxial cable
 

902

Member
Joined
Nov 7, 2003
Messages
2,620
Location
Downsouthsomewhere
Location: Southeast Asia
Oil Refinery
We used color code and its different in each repeater
Repeater:Mototrbo R8200
I only a saw a duplexer in each repeater, i didnt take note of the model but it has four cyclinder tube i dont know the name
Antenna Separation: Horizontal
Cable used from duplexer to antenna : Heliax cable
Cable used repeater to duplexer: mixed the other repeater has rg-8 cable and the other has thin coaxial cable
Thank you. My knowledge of DMR is limited. I'm only a casual user of it on amateur radio, and that is infrequently.

With respect to the RF stuff, I would replace the RG-8 cable with RG-214 and use silver plated connectors, rather than nickel plating.

The smaller cables, if they are 1/4" FSJ or RG-142/RG-400 are fine. If they are LMR-240 or RG-8X or even LMR-400 (NOT the same as RG-400!), I would replace those, as the gaps between the foil and the woven braid of the shield may produce arcing that would impact duplex service.

I would run each of the frequencies in a mixing product analysis program, such as ComSitePro (which is no longer supported and has been cut loose by Black and Veatch) to see if the arithmetic products of the transmitters (accounting for more deviation in harmonics and for receiver passbands) to see whether they end up on a receiver frequency. You may need to install isolation devices between your transmitter ports and duplexers or literally move your antennas to achieve greater physical separation.

Finally, I would look to vertically separate the antennas. Vertical separation provides much higher isolation than horizontal separation, and the same amount of isolation can be achieved in tens of feet in vertical, whereas horizontal would require hundreds of feet. Here is an article on that separation: Isolation between the repeater receiver and RF sources

Good luck!
 
Status
Not open for further replies.
Top