RE: [Repeater-Builder] Re: Linking and interference problem

[John Godfrey]

Joe, Thanks for asking..
 
Question #1 link antenna is on top. 8 element yagi vertical pointed 210 SW
 
Question #2 No. They are on different legs and each is on the other side of
the tower, almost directly opposite each other.
 
Question #3 No preamp.
 
Question #4 1/2 inch Andrews Heliax (not superflex) on both UHF units 150FT
on one 140Ft on the other. 3ft jumpers 9914 belden on each radio. same on
the Yagi's. N type connectors. Wish we could afford 7/8, but we take what
the club can afford and work with that. Our club has appox 50 members,
sometimes more or less depending on when they pay there dues. Hi HI. I know
you didn't ask, but just in case you needed to know, 7/8 is not an option
for us right now.
 
Agreed that even just a few extra db rejection would do the trick. It
wouldn't take a lot I don't think based on the squelch test, but a few db I
would be highly thankful for, and I just don't have the knowledge to know
how to get there from here. (-:

73 de  John Godfrey
KE5NZY BARC Pres.



-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Joe Burkleo
Sent: Saturday, May 02, 2009 12:04 AM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Re: Linking and interference problem





John,
I like the others on here believe that your frequency and antenna spacing is
too close to work with out filters and/or additional isolation.

I do have a couple questions about your UHF antennas and their placement on
the tower.

1. What type of antenna are you using for your link and is it the top or
bottom antenna?

2. Are both UHF antennas on the same tower leg and spaced out the same
distance so they are pretty much directly underneath or above each other?

3. Do you have a preamp on the link receiver, if so what brand?

4. What are you using for feedline and cables inside the building for the
UHF repeater and link radio?

I am trying to come up with some other ideas that will buy you a few extra
DB of rejection here and there. A little here and there and pretty soon you
have another 10-20 db of isolation you did not have before.

Joe - WA7JAW

--- In Repeater-Builder@ 
yahoogroups.com, "John Godfrey"  wrote:
>
> I was hoping you can help our club with a repeater link problem. What we
> have are all GE master 2 stuff. Here is what we have going on. we have
> had for years a 147.270 + repeater that works great.
> 
> Last year we added a link into a central state repeater system using a
link radio on
> one of our ports. It transmits on 442.025 and receives on 443.2. For six
> months we have used the link fine without problems. Last week we
> installed on another port a uhf repeater to be used as a hub for the
> north central part of our state to also link to us and the central state
> system. The UHF Repeater receives on 449.750 and transmits on 444.750.
> We can link the 270 to either the link to central state or the UHF
> repeater hub with no problems, but when we link the 270 to both or just
> link the UHF repeater to the link radio, once the UHF repeater is keyed
> up, the input on the link radio is hearing it so we have an awful squeal
> and intermod back into the 270.
> 
> There is also a pager at the location that I can hear when this happens
but not any other time. Again they work fine as long as both UHF machines
are not in use at the same time. When the 270 is linked into Central state,
even if the UHF repeater is not linked in, if you key the UHF repeater you
here the squeal on the 270. I can see how as the link input goes out over
the 270 when they are linked. I am not sure why I can also here it on the
UHF repeater when I unkey it, even if it isn't linked in. Other than the
last part of that it would make since to ne that I have the two 440 antennas
to close. We have them about 10 feet apart, but the one can't go higher and
the other can't go lower and still serve the purpose needed.
> 
> I am thinking I need some kind of filter, that I can put on the link
radio,
> that will protect it from the transmit of the UHF repeater. In other
> words the 444.750 is coming in my receive on the 443.2. Changing freq is
> not an option due to several reasons. If I had a filter of some sort,
> that would either allow say 442-443.5 to pass and attenuate everything
> else that would be great. Or something that would pass 442-443.5 and
> attenuate everything above 443.5, then that would work. Guys, what am I
> looking for and where might I find it. Must I build something that is
> this custom, or can I buy it. If I must build it, where should I start.
> If I can buy it,, where from and what would they call it.
> 
> If my thoughts are off base, please help me to know what other questions I
> need to answer to solve such a problem as this. I thought maybe the
> pager was just interfering, but why would the 270 work fine when linked
> to the link radio, or linked to the UHF repeater, and the only 

RE: [Repeater-Builder] Re: Linking and interference problem

[John Godfrey]

Joe, the UHF link radio which is the only one receiving the interference, is
a GE Master II mobile. The rest are GE Master II stuff as well, but they are
what I guess you are calling the station configuration, because we have them
rack mounted and the door opens up like a hinge and the components and
boards accessible that way. I am just the helper on this project as you can
tell, and my knowledge is very weak on this issue. 
 
At the moment the problem has been minimized to a large degree based on
setting the squelch as tight as it will go, and the receive signal still
breaks the squelch and the interference can't. However when the receive
signal drops, you can still hear the sound for like 50ms on the squelch
tale. The person who does our repeater work KD5HPK could answer any
questions about the equipment much better than I could, but his request to
me was to try to find a narrow notch filter for the frequencies as per the
original email. I added the dialog in the original email, so you guys could
help me determine the best approach. I know it seemed like a lot of
rambling. 
 
I have no way to know what all is on the site as it has maybe 15 antennas on
the tower that I don't even know who they belong to. It is a commercial
tower site with many systems and even different buildings that we don't have
access to. We have identified however that we only get the feedback when
both our UHF units are active and no other time. We also can link either on
into the 2 meter repeater with no problems. We have duplexers on both
repeaters of course and not the link radio as it isn't full duplex. 
 
The reason we are tied to those frequencies is that we are linked to several
other repeaters and in one direction the UHF Main hub is 75 miles away and
they can't change there frequencies because several are linked into it. In
the other direction folks link into our UHF repeater from 50 miles away and
that freq is set due to the fact that those guys have all their equipment
configured for that frequency. 
 
So to make the long story short we are the link in the middle. Repeater
pairs in our location are not easily changed due to what I have mentioned,
plus there are not a lot of them left to coordinate anyhow. If we can just
keep the transmit of the UHF repeater out of the input on the link radio..
problem solved. We have proven that with the squelch method, and while that
will work for now. We don't like the little dirty squelch tale as it doesn't
sound perfect, and don't we all strive for perfection (-: 
 
I think the right kind of filter would make it perfect, but I am not sure of
that,,, where to find one,, what to call it,, or how to build it.. That to
me seems to be the question.. If I am asking the wrong question.. Please
just overlook my lack of knowledge on the subject. I build a great
amplifier, repeaters are just not my strong suit yet, but I am starting to
learn it.
 

73 de  John Godfrey




-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Joe Burkleo
Sent: Saturday, May 02, 2009 12:07 AM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Re: Linking and interference problem





john,
Forgot to ask in my first reply.

I am assuming that your link radio is also a Mastr II from your original
post.

Is it a mobile or a station configuration?

Thanks,
Joe

--- In Repeater-Builder@ 
yahoogroups.com, "John Godfrey"  wrote:
>
> I was hoping you can help our club with a repeater link problem. What we
> have are all GE master 2 stuff. Here is what we have going on. we have
> had for years a 147.270 + repeater that works great.
> 
> Last year we added a link into a central state repeater system using a
link radio on
> one of our ports. It transmits on 442.025 and receives on 443.2. For six
> months we have used the link fine without problems. Last week we
> installed on another port a uhf repeater to be used as a hub for the
> north central part of our state to also link to us and the central state
> system. The UHF Repeater receives on 449.750 and transmits on 444.750.
> We can link the 270 to either the link to central state or the UHF
> repeater hub with no problems, but when we link the 270 to both or just
> link the UHF repeater to the link radio, once the UHF repeater is keyed
> up, the input on the link radio is hearing it so we have an awful squeal
> and intermod back into the 270.
> 
> There is also a pager at the location that I can hear when this happens
but not any other time. Again they work fine as long as both UHF machines
are not in use at the same time. When the 270 is linked into Central state,
even if the UHF repeater is not linked in, if you key the UHF repeater you
here the squeal on the 270. I can see how as the link input goes out over
the 270 when they are linked. I am not sure why I can also here it on the
UHF repeater when I unkey it, even if it isn't linked in. Other t

[Repeater-Builder] Re: Linking and interference problem

[Joe Burkleo]

john,
Forgot to ask in my first reply.

I am assuming that your link radio is also a Mastr II from your original post.

Is it a mobile or a station configuration?

Thanks,
Joe

--- In Repeater-Builder@yahoogroups.com, "John Godfrey"  wrote:
>
> I was hoping you can help our club with a repeater link problem. What we
> have are all GE master 2 stuff. Here is what we have going on. we have
> had for years a 147.270 + repeater that works great.
> 
> Last year we added a link into a central state repeater system using a link 
> radio on
> one of our ports. It transmits on 442.025 and receives on 443.2. For six
> months we have used the link fine without problems. Last week we
> installed on another port a uhf repeater to be used as a hub for the
> north central part of our state to also link to us and the central state
> system. The UHF Repeater receives on 449.750 and transmits on 444.750.
> We can link the 270 to either the link to central state or the UHF
> repeater hub with no problems, but when we link the 270 to both or just
> link the UHF repeater to the link radio, once the UHF repeater is keyed
> up, the input on the link radio is hearing it so we have an awful squeal
> and intermod back into the 270.
> 
> There is also a pager at the location that I can hear when this happens but 
> not any other time. Again they work fine as long as both UHF machines are not 
> in use at the same time. When the 270 is linked into Central state, even if 
> the UHF repeater is not linked in, if you key the UHF repeater you here the 
> squeal on the 270. I can see how as the link input goes out over the 270 when 
> they are linked. I am not sure why I can also here it on the UHF repeater 
> when I unkey it, even if it isn't linked in. Other than the last part of that 
> it would make since to ne that I have the two 440 antennas to close. We have 
> them about 10 feet apart, but the one can't go higher and  the other can't go 
> lower and still serve the purpose needed.
> 
> I am thinking I need some kind of filter, that I can put on the link radio,
> that will protect it from the transmit of the UHF repeater. In other
> words the 444.750 is coming in my receive on the 443.2. Changing freq is
> not an option due to several reasons. If I had a filter of some sort,
> that would either allow say 442-443.5 to pass and attenuate everything
> else that would be great. Or something that would pass 442-443.5 and
> attenuate everything above 443.5, then that would work. Guys, what am I
> looking for and where might I find it. Must I build something that is
> this custom, or can I buy it. If I must build it, where should I start.
> If I can buy it,, where from and what would they call it.
> 
> If my thoughts are off base, please help me to know what other questions I
> need to answer to solve such a problem as this. I thought maybe the
> pager was just interfering, but why would the 270 work fine when linked
> to the link radio, or linked to the UHF repeater, and the only time we
> have the problem is when the 270 is linked to the link radio and the UHF
> repeater is keyed up, regardless of whether the UHF repeater is linked
> in or not.
> 
> I know my question is long, but m hope was to explain the
> problem with enough detail that you might have an answer for me.
> 
> Your help would be greatly appreciated by our Club.
> 73 de  John Godfrey
> KE5NZY BARC Pres.
> DISTRICT B ADEC
> ASTEN NM
>

[Repeater-Builder] Re: Linking and interference problem

[Joe Burkleo]

John,
I like the others on here believe that your frequency and antenna spacing is 
too close to work with out filters and/or additional isolation.

I do have a couple questions about your UHF antennas and their placement on the 
tower.

1. What type of antenna are you using for your link and is it the top or bottom 
antenna?

2. Are both UHF antennas on the same tower leg and spaced out the same distance 
so they are pretty much directly underneath or above each other?

3. Do you have a preamp on the link receiver, if so what brand?

4. What are you using for feedline and cables inside the building for the UHF 
repeater and link radio?

I am trying to come up with some other ideas that will buy you a few extra DB 
of rejection here and there. A little here and there and pretty soon you have 
another 10-20 db of isolation you did not have before.

Joe - WA7JAW


--- In Repeater-Builder@yahoogroups.com, "John Godfrey"  wrote:
>
> I was hoping you can help our club with a repeater link problem. What we
> have are all GE master 2 stuff. Here is what we have going on. we have
> had for years a 147.270 + repeater that works great.
> 
> Last year we added a link into a central state repeater system using a link 
> radio on
> one of our ports. It transmits on 442.025 and receives on 443.2. For six
> months we have used the link fine without problems. Last week we
> installed on another port a uhf repeater to be used as a hub for the
> north central part of our state to also link to us and the central state
> system. The UHF Repeater receives on 449.750 and transmits on 444.750.
> We can link the 270 to either the link to central state or the UHF
> repeater hub with no problems, but when we link the 270 to both or just
> link the UHF repeater to the link radio, once the UHF repeater is keyed
> up, the input on the link radio is hearing it so we have an awful squeal
> and intermod back into the 270.
> 
> There is also a pager at the location that I can hear when this happens but 
> not any other time. Again they work fine as long as both UHF machines are not 
> in use at the same time. When the 270 is linked into Central state, even if 
> the UHF repeater is not linked in, if you key the UHF repeater you here the 
> squeal on the 270. I can see how as the link input goes out over the 270 when 
> they are linked. I am not sure why I can also here it on the UHF repeater 
> when I unkey it, even if it isn't linked in. Other than the last part of that 
> it would make since to ne that I have the two 440 antennas to close. We have 
> them about 10 feet apart, but the one can't go higher and  the other can't go 
> lower and still serve the purpose needed.
> 
> I am thinking I need some kind of filter, that I can put on the link radio,
> that will protect it from the transmit of the UHF repeater. In other
> words the 444.750 is coming in my receive on the 443.2. Changing freq is
> not an option due to several reasons. If I had a filter of some sort,
> that would either allow say 442-443.5 to pass and attenuate everything
> else that would be great. Or something that would pass 442-443.5 and
> attenuate everything above 443.5, then that would work. Guys, what am I
> looking for and where might I find it. Must I build something that is
> this custom, or can I buy it. If I must build it, where should I start.
> If I can buy it,, where from and what would they call it.
> 
> If my thoughts are off base, please help me to know what other questions I
> need to answer to solve such a problem as this. I thought maybe the
> pager was just interfering, but why would the 270 work fine when linked
> to the link radio, or linked to the UHF repeater, and the only time we
> have the problem is when the 270 is linked to the link radio and the UHF
> repeater is keyed up, regardless of whether the UHF repeater is linked
> in or not.
> 
> I know my question is long, but m hope was to explain the
> problem with enough detail that you might have an answer for me.
> 
> Your help would be greatly appreciated by our Club.
> 73 de  John Godfrey
> KE5NZY BARC Pres.
> DISTRICT B ADEC
> ASTEN NM
>

[Repeater-Builder] Software for Motorola TRICK - ENLN4056A controller

[mm1bjp]

Hi, I am trying to covert a motorola repeater onto the 70cms amatuer band, and 
have successfully reprogrammed the GM350's.

Could somebody give me some help as to what software and hardware is required 
to program the ENLN4056A TRICK controller?  Is it the same programming lead as 
programming the 350's ?  I have some programming software, but not sure what 
filename I am looking for for the TRICK.

73's
Allan
MM1BJP

Re: [Repeater-Builder] Computer noise in 2M Repeater

[William Becks]

Bill,

Thanks for responding with the information about the shield kits being supplied 
by the manufacturer.   With this info I will be able to contact them for a 
price and availability check for our site.  I first encountered RFI caused by 
the early Flashguard units back in the mid 90's.  My company had a site with a 
UHF TDMA rural radio (BETRS) system that suffered high BERT at night.  At the 
time, Flashguard offered a suppression kit to retrofit the strobe housing, but 
that proved to be virtually ineffective.   As a temporary fix, we had gave up 
channel capacity switching from 16-PSK to 4-PSK modulation.   Eventually, we 
just got rid of the strobe and went with an incandescent beacon lamp system on 
the tower. 

Bill



- Original Message - 
  From: Bill Smith 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Friday, May 01, 2009 1:37 PM
  Subject: RE: [Repeater-Builder] Computer noise in 2M Repeater





  We contacted Honeywell/Flashguard and they sold us the kits. In our 
situation, we changed to our backup antenna which is 20 feet below the main 
which is less than 2 feet from the strobe head until the shield kit was 
installed. The shield housing mounts to the top plate of the tower with the 
strobe head placed inside. It's hinged to allow service access. The cable 
shield is a plastic covered metal liquid tight conduit with a fitting that 
connects to the shield housing to ground it. Sorry I don't have any cost info.

   

  Bill

   


--

  From: Repeater-Builder@yahoogroups.com 
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of William Becks
  Sent: Tuesday, April 28, 2009 7:34 PM
  To: Repeater-Builder@yahoogroups.com
  Subject: Re: [Repeater-Builder] Computer noise in 2M Repeater

   






  Bill,

   

  Can you please elaborate on the shield housing used?  I have similar noise on 
my VHF ham repeater caused by the same Flashguard 3000 system.  I was able to 
reduce the noise during night operation by reorientation of the antenna at the 
expense of a less than optimum radiation pattern.  The cellular company that 
owns the tower doesn't seem to have any problems with the RFI from the strobe 
lamps, but then they are using panel antennas directed away from the tower and 
strobe lamps. 

   

  Thank you,

   

  Bill, WA8WG

   

- Original Message - 

From: Bill Smith 

To: Repeater-Builder@yahoogroups.com 

Sent: Tuesday, April 28, 2009 4:33 PM

Subject: RE: [Repeater-Builder] Computer noise in 2M Repeater

 

I have experience with several 451 MHz systems getting hammered by noise 
from the strobe. These were Flashguard 3000 units. During the day when the 
strobe tubes triggered once it wasn't noticeable. At night when the tubes were 
retriggered multiple times to lengthen the on time of the flash, it dropped our 
RX sensitivity by over 30 dB. A spectrum analysis showed noticeable RF from 
below 50 MHz, peaking around UHF and dropping off around 900 MHz. In this unit, 
the tubes are about 6 inches long. We installed a shield housing over the 
entire head and 20 feet down the power cable along with installing toroids on 
the power feed inside the head.

 

Bill

KB1MGH

 




Now. the strobe problem you're describing sounds like a potential horrible 
electrical problem at the site.  In my experience an FM rig shouldn't be 
greatly affected by a strobe.  It also shouldn't be causing a problem/reaction 
with the WISP gear (it may be causing damage to it!) so I'd definitely find out 
what is going is going on with the strobe.

 

Good luck!

Jacob Suter

 








  

RE: [Repeater-Builder] Computer noise in 2M Repeater

[Bill Smith]

We contacted Honeywell/Flashguard and they sold us the kits. In our
situation, we changed to our backup antenna which is 20 feet below the main
which is less than 2 feet from the strobe head until the shield kit was
installed. The shield housing mounts to the top plate of the tower with the
strobe head placed inside. It's hinged to allow service access. The cable
shield is a plastic covered metal liquid tight conduit with a fitting that
connects to the shield housing to ground it. Sorry I don't have any cost
info.

 

Bill

 

  _  

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of William Becks
Sent: Tuesday, April 28, 2009 7:34 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Computer noise in 2M Repeater

 






Bill,

 

Can you please elaborate on the shield housing used?  I have similar noise
on my VHF ham repeater caused by the same Flashguard 3000 system.  I was
able to reduce the noise during night operation by reorientation of the
antenna at the expense of a less than optimum radiation pattern.  The
cellular company that owns the tower doesn't seem to have any problems with
the RFI from the strobe lamps, but then they are using panel antennas
directed away from the tower and strobe lamps. 

 

Thank you,

 

Bill, WA8WG

 

- Original Message - 

From: Bill Smith   

To: Repeater-Builder@yahoogroups.com 

Sent: Tuesday, April 28, 2009 4:33 PM

Subject: RE: [Repeater-Builder] Computer noise in 2M Repeater

 

I have experience with several 451 MHz systems getting hammered by noise
from the strobe. These were Flashguard 3000 units. During the day when the
strobe tubes triggered once it wasn't noticeable. At night when the tubes
were retriggered multiple times to lengthen the on time of the flash, it
dropped our RX sensitivity by over 30 dB. A spectrum analysis showed
noticeable RF from below 50 MHz, peaking around UHF and dropping off around
900 MHz. In this unit, the tubes are about 6 inches long. We installed a
shield housing over the entire head and 20 feet down the power cable along
with installing toroids on the power feed inside the head.

 

Bill

KB1MGH

 


  _  


Now. the strobe problem you're describing sounds like a potential horrible
electrical problem at the site.  In my experience an FM rig shouldn't be
greatly affected by a strobe.  It also shouldn't be causing a
problem/reaction with the WISP gear (it may be causing damage to it!) so I'd
definitely find out what is going is going on with the strobe.

 

Good luck!

Jacob Suter

 

Re: [Repeater-Builder] Computer noise in 2M Repeater

[wd8chl]

Brian Raker wrote:
> Either that or talk with your tower owner and let them know that this
> tennant may need to run shielded cat5 cable up the tower, as it is
> providing interference with your equipment.
> 

And don't forget that they are unlicensed, and by FEDERAL LAW must NOT 
interfere with licensed services, and they MUST accept any interference 
they receive. The site owner needs to understand that, because that 
equipment WILL interfere with other services on the tower or nearby.
If it's bothering you, it's bothering someone else too!


>>>
>>> Does anyone have any suggestions on how to
>>> eliminate noise generated by a Wireless
>>>
>>> Internet System. The
>>> owner of the tower where our club has our 145.370 MHz repeater
>>>
>>> has rented space to a group who have mounted a wireless Internet "relay" on 
>>> the tower.
>>>
>>> The system is simple, it consist of a Netgear switch, a
>>> Microwave dish and a smallYagi.
>>>
>>> There is approx. 300 feet of Cat 5 wire going up and 300 feet coming down 
>>> the
>>> tower.
>>>
>>> Their antennas are mounted within a few feet
>>> of ours on the top of the 260 ft. tower.
>>>
>>> We unplugged the netgear switch and the noise
>>> cleared, we disconnected our
>>>
>>> antenna and the
>>> noise goes away. The noise rides on
>>> the repeater receiver squelch tail.
>>>
>>> We do use a PL tone
>>> or we wouldn't be able to use our repeater at all
>>>
>>>
>>>
>>> Jim WK5Y

[Repeater-Builder] Re: Linking and interference problem

[Steve]

I just made a very quick read of your description of the problem.
I agree that you very likely are experiencing desense because of the meg and a 
half difference between one of your UHF TX and one Rx.
This is a pretty common problem when more than one system is located at a site. 
A quick look at a generic Tx / Rx isolation graph shows at a meg and a half you 
need about 85 dB of isolation at UHF. (assuming something like 25 watts)
Your antenna spacing (sounds like about 4 wavelengths) might be giving you 22 
dB or so.
You are probably going to need to build a "window filter" which is similar to a 
duplexer.
You might be able to use just a couple of cavities and notch the unwanted Tx 
from your Rx if the cavities you use can notch that close.
You can also get some notching by using critical length cables to maximize 
whatever notch & pass response the cavities already give.
You likely will need the help of someone in your area with a tracking generator 
to help.
And with physically close spaced transmitters like you have, I would be a good 
idea to get transmitter isolators to avoid problems in the future.
Keep in mind the numbers above are a quick rough estimate.
However you really are looking at something around 60 dB of additional 
isolation no matter what calculation you use.