We have 146.04/.64 repeater on a nearby mountain top. It worked great for
years with a range of 100 miles or more. Since the phone company and a pager
company installed their high power transmitters near the site of the
repeater (within 100 yards) the repeater is virtually useless. After much
head scratching I believe that the difference in frequency of the pager
transmitter of 600 khz is the problem but have no idea how to solve the
problem without going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The transmitter and receiver
on the repeater are both Motorola Micor and were modified with to the
repeater frequencies by FCC 1st class licensed hams using Motorola parts.
This is not an equipment problem. We are running a set of Wacom cavities
which were bought new and are correctly tuned and the antenna is a
Phelps-Dodge Stationmaster. When the intermod occurs it is dependant on BOTH
pagers transmitting at the same time. If only one pager is transmitting
there is no problem. This may at first sound unusual but the pagers are in
the 150 mhz band and they are exactly 600 kc apart. These transmitter are
both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers) is mixing with the
output of the repeater 146.64 and producing the 146.04 signal, the repeater
input frequency. We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the repeater drops. The
intermod cannot hold up the machine once the tone is removed. This may be
happening in the antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this conclusion.

We are not the only 2 meter repeater that has fallen victim of this problem
and in every case we have found two pager transmitters situated 600 kc apart
near the repeater. Most of the other machines have been taken off the air,
others just put up with it. No one has been able to solve the problem and
many technicians have studied it.

Moving the repeater far enough away is not an option since the peak of the
mountain is so small. Also we are using an existing tower which we would not
have access to at other locations. The searches I have done on Google has
turned up the stock answer of helical resonators which would apply to 2
meter radios but not repeaters. If you are familiar with the Micor equipment
you know that the receiver has excellent helical resonators built in.

Tonight I have considered the possibility of splitting the receiver and the
transmitter of the repeater and linking the rx signal by a 220 mhz link. I
am hoping that by reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas. This split would be
only about 100 yards but could that be sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any input (pun
intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.

The inter mod could be originating in your receiver or in one of the
paging transmitters. Part of it could even be originating in your own
transmitter.
The first thing I would try is a couple of notch cavities in your
antenna line tuned to one or both of the paging transmitter
frequencies.

First tune both to the same paging transmitter frequency. Then try the
other one. Then try one on each paging frequency.

If they make no difference then it is a good bet that the inter mod is
originating in some other transmitter. Your repeater signal may be
mixing in their transmitter. The only way to cure that is a notch
cavity in their antenna line tuned to your transmitter frequency.

A pass cavity or two in your receiver line may help. But you will be
able to get much more rejection with a notch than a pass.

If you don't have a notch cavity but do have a pass cavity you can use
the pass cavity as a notch by placing a T in the antenna line and
connecting only one loop of the pass cavity. That will function as a
notch.

73
Gary K4FMX



On Mon, 20 Dec 2004 20:48:54 -0500, "Photoman"
wrote:

We have 146.04/.64 repeater on a nearby mountain top. It worked great for
years with a range of 100 miles or more. Since the phone company and a pager
company installed their high power transmitters near the site of the
repeater (within 100 yards) the repeater is virtually useless. After much
head scratching I believe that the difference in frequency of the pager
transmitter of 600 khz is the problem but have no idea how to solve the
problem without going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The transmitter and receiver
on the repeater are both Motorola Micor and were modified with to the
repeater frequencies by FCC 1st class licensed hams using Motorola parts.
This is not an equipment problem. We are running a set of Wacom cavities
which were bought new and are correctly tuned and the antenna is a
Phelps-Dodge Stationmaster. When the intermod occurs it is dependant on BOTH
pagers transmitting at the same time. If only one pager is transmitting
there is no problem. This may at first sound unusual but the pagers are in
the 150 mhz band and they are exactly 600 kc apart. These transmitter are
both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers) is mixing with the
output of the repeater 146.64 and producing the 146.04 signal, the repeater
input frequency. We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the repeater drops. The
intermod cannot hold up the machine once the tone is removed. This may be
happening in the antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this conclusion.

We are not the only 2 meter repeater that has fallen victim of this problem
and in every case we have found two pager transmitters situated 600 kc apart
near the repeater. Most of the other machines have been taken off the air,
others just put up with it. No one has been able to solve the problem and
many technicians have studied it.

Moving the repeater far enough away is not an option since the peak of the
mountain is so small. Also we are using an existing tower which we would not
have access to at other locations. The searches I have done on Google has
turned up the stock answer of helical resonators which would apply to 2
meter radios but not repeaters. If you are familiar with the Micor equipment
you know that the receiver has excellent helical resonators built in.

Tonight I have considered the possibility of splitting the receiver and the
transmitter of the repeater and linking the rx signal by a 220 mhz link. I
am hoping that by reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas. This split would be
only about 100 yards but could that be sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any input (pun
intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.

The inter mod could be originating in your receiver or in one of the
paging transmitters. Part of it could even be originating in your own
transmitter.
The first thing I would try is a couple of notch cavities in your
antenna line tuned to one or both of the paging transmitter
frequencies.

First tune both to the same paging transmitter frequency. Then try the
other one. Then try one on each paging frequency.

If they make no difference then it is a good bet that the inter mod is
originating in some other transmitter. Your repeater signal may be
mixing in their transmitter. The only way to cure that is a notch
cavity in their antenna line tuned to your transmitter frequency.

A pass cavity or two in your receiver line may help. But you will be
able to get much more rejection with a notch than a pass.

If you don't have a notch cavity but do have a pass cavity you can use
the pass cavity as a notch by placing a T in the antenna line and
connecting only one loop of the pass cavity. That will function as a
notch.

73
Gary K4FMX



On Mon, 20 Dec 2004 20:48:54 -0500, "Photoman"
wrote:

We have 146.04/.64 repeater on a nearby mountain top. It worked great for
years with a range of 100 miles or more. Since the phone company and a pager
company installed their high power transmitters near the site of the
repeater (within 100 yards) the repeater is virtually useless. After much
head scratching I believe that the difference in frequency of the pager
transmitter of 600 khz is the problem but have no idea how to solve the
problem without going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The transmitter and receiver
on the repeater are both Motorola Micor and were modified with to the
repeater frequencies by FCC 1st class licensed hams using Motorola parts.
This is not an equipment problem. We are running a set of Wacom cavities
which were bought new and are correctly tuned and the antenna is a
Phelps-Dodge Stationmaster. When the intermod occurs it is dependant on BOTH
pagers transmitting at the same time. If only one pager is transmitting
there is no problem. This may at first sound unusual but the pagers are in
the 150 mhz band and they are exactly 600 kc apart. These transmitter are
both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers) is mixing with the
output of the repeater 146.64 and producing the 146.04 signal, the repeater
input frequency. We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the repeater drops. The
intermod cannot hold up the machine once the tone is removed. This may be
happening in the antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this conclusion.

We are not the only 2 meter repeater that has fallen victim of this problem
and in every case we have found two pager transmitters situated 600 kc apart
near the repeater. Most of the other machines have been taken off the air,
others just put up with it. No one has been able to solve the problem and
many technicians have studied it.

Moving the repeater far enough away is not an option since the peak of the
mountain is so small. Also we are using an existing tower which we would not
have access to at other locations. The searches I have done on Google has
turned up the stock answer of helical resonators which would apply to 2
meter radios but not repeaters. If you are familiar with the Micor equipment
you know that the receiver has excellent helical resonators built in.

Tonight I have considered the possibility of splitting the receiver and the
transmitter of the repeater and linking the rx signal by a 220 mhz link. I
am hoping that by reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas. This split would be
only about 100 yards but could that be sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any input (pun
intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.

Photoman wrote:
We have 146.04/.64 repeater on a nearby mountain top. It worked great for
years with a range of 100 miles or more. Since the phone company and a pager
company installed their high power transmitters near the site of the
repeater (within 100 yards) the repeater is virtually useless. After much
head scratching I believe that the difference in frequency of the pager
transmitter of 600 khz is the problem but have no idea how to solve the
problem without going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The transmitter and receiver
on the repeater are both Motorola Micor and were modified with to the
repeater frequencies by FCC 1st class licensed hams using Motorola parts.
This is not an equipment problem. We are running a set of Wacom cavities
which were bought new and are correctly tuned and the antenna is a
Phelps-Dodge Stationmaster. When the intermod occurs it is dependant on BOTH
pagers transmitting at the same time. If only one pager is transmitting
there is no problem. This may at first sound unusual but the pagers are in
the 150 mhz band and they are exactly 600 kc apart. These transmitter are
both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers) is mixing with the
output of the repeater 146.64 and producing the 146.04 signal, the repeater
input frequency. We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the repeater drops. The
intermod cannot hold up the machine once the tone is removed. This may be
happening in the antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this conclusion.

We are not the only 2 meter repeater that has fallen victim of this problem
and in every case we have found two pager transmitters situated 600 kc apart
near the repeater. Most of the other machines have been taken off the air,
others just put up with it. No one has been able to solve the problem and
many technicians have studied it.

Moving the repeater far enough away is not an option since the peak of the
mountain is so small. Also we are using an existing tower which we would not
have access to at other locations. The searches I have done on Google has
turned up the stock answer of helical resonators which would apply to 2
meter radios but not repeaters. If you are familiar with the Micor equipment
you know that the receiver has excellent helical resonators built in.

Tonight I have considered the possibility of splitting the receiver and the
transmitter of the repeater and linking the rx signal by a 220 mhz link. I
am hoping that by reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas. This split would be
only about 100 yards but could that be sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any input (pun
intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.



It might be helpful to disclose the frequencies of the transmitters
and the IF frequencies in your system.

I have a problem that a new towing company transmitter is 16.9MHz above
my output frequency on 440. Guess what the IF frequency of my remote
base might be. It's so strong that I get intermod with the remote
base antenna disconnected.
mike

--
Return address is VALID.
Wanted, Slot 1 Motherboard
500MHz Tek DSOscilloscope TDS540 Make Offer
http://nm7u.tripod.com/homepage/te.html
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
http://www.geocities.com/SiliconValley/Monitor/4710/

Photoman wrote:
We have 146.04/.64 repeater on a nearby mountain top. It worked great for
years with a range of 100 miles or more. Since the phone company and a pager
company installed their high power transmitters near the site of the
repeater (within 100 yards) the repeater is virtually useless. After much
head scratching I believe that the difference in frequency of the pager
transmitter of 600 khz is the problem but have no idea how to solve the
problem without going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The transmitter and receiver
on the repeater are both Motorola Micor and were modified with to the
repeater frequencies by FCC 1st class licensed hams using Motorola parts.
This is not an equipment problem. We are running a set of Wacom cavities
which were bought new and are correctly tuned and the antenna is a
Phelps-Dodge Stationmaster. When the intermod occurs it is dependant on BOTH
pagers transmitting at the same time. If only one pager is transmitting
there is no problem. This may at first sound unusual but the pagers are in
the 150 mhz band and they are exactly 600 kc apart. These transmitter are
both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers) is mixing with the
output of the repeater 146.64 and producing the 146.04 signal, the repeater
input frequency. We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the repeater drops. The
intermod cannot hold up the machine once the tone is removed. This may be
happening in the antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this conclusion.

We are not the only 2 meter repeater that has fallen victim of this problem
and in every case we have found two pager transmitters situated 600 kc apart
near the repeater. Most of the other machines have been taken off the air,
others just put up with it. No one has been able to solve the problem and
many technicians have studied it.

Moving the repeater far enough away is not an option since the peak of the
mountain is so small. Also we are using an existing tower which we would not
have access to at other locations. The searches I have done on Google has
turned up the stock answer of helical resonators which would apply to 2
meter radios but not repeaters. If you are familiar with the Micor equipment
you know that the receiver has excellent helical resonators built in.

Tonight I have considered the possibility of splitting the receiver and the
transmitter of the repeater and linking the rx signal by a 220 mhz link. I
am hoping that by reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas. This split would be
only about 100 yards but could that be sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any input (pun
intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.



It might be helpful to disclose the frequencies of the transmitters
and the IF frequencies in your system.

I have a problem that a new towing company transmitter is 16.9MHz above
my output frequency on 440. Guess what the IF frequency of my remote
base might be. It's so strong that I get intermod with the remote
base antenna disconnected.
mike

--
Return address is VALID.
Wanted, Slot 1 Motherboard
500MHz Tek DSOscilloscope TDS540 Make Offer
http://nm7u.tripod.com/homepage/te.html
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
http://www.geocities.com/SiliconValley/Monitor/4710/

If the problem was generated in your transmitter from mixing with the
paging transmitters it will usually only occur when your repeater
transmitter is on. It sounds like the interference signal is being
generated elsewhere. You should first determine if the problem is in
your installation or from the pagers. I would use a spectrum analyzer or
service monitor at the receive port of your repeater tuned to your
receive frequency to see what it looks like and measure the level. It
may look like a comb generator every time the pagers fire up! You can
then try another antenna into the analyzer to see if the interference
persists or use a directional antenna to see if it’s emanating from the
pager site or yours. Since you mention other repeaters in your area are
suffering from the same problem I would suspect at least one of the
paging transmitters does not have an isolator, which is required at all
sites I have ever dealt with. If you can pick up the interfering signal
on a separate antenna with test equipment and it points to the paging
site, you can demand the pager owners address the problem with isolators
or what ever it takes to minimize the interference.

Photoman wrote:
We have 146.04/.64 repeater on a nearby mountain top. It worked great for
years with a range of 100 miles or more. Since the phone company and a pager
company installed their high power transmitters near the site of the
repeater (within 100 yards) the repeater is virtually useless. After much
head scratching I believe that the difference in frequency of the pager
transmitter of 600 khz is the problem but have no idea how to solve the
problem without going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The transmitter and receiver
on the repeater are both Motorola Micor and were modified with to the
repeater frequencies by FCC 1st class licensed hams using Motorola parts.
This is not an equipment problem. We are running a set of Wacom cavities
which were bought new and are correctly tuned and the antenna is a
Phelps-Dodge Stationmaster. When the intermod occurs it is dependant on BOTH
pagers transmitting at the same time. If only one pager is transmitting
there is no problem. This may at first sound unusual but the pagers are in
the 150 mhz band and they are exactly 600 kc apart. These transmitter are
both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers) is mixing with the
output of the repeater 146.64 and producing the 146.04 signal, the repeater
input frequency. We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the repeater drops. The
intermod cannot hold up the machine once the tone is removed. This may be
happening in the antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this conclusion.

We are not the only 2 meter repeater that has fallen victim of this problem
and in every case we have found two pager transmitters situated 600 kc apart
near the repeater. Most of the other machines have been taken off the air,
others just put up with it. No one has been able to solve the problem and
many technicians have studied it.

Moving the repeater far enough away is not an option since the peak of the
mountain is so small. Also we are using an existing tower which we would not
have access to at other locations. The searches I have done on Google has
turned up the stock answer of helical resonators which would apply to 2
meter radios but not repeaters. If you are familiar with the Micor equipment
you know that the receiver has excellent helical resonators built in.

Tonight I have considered the possibility of splitting the receiver and the
transmitter of the repeater and linking the rx signal by a 220 mhz link. I
am hoping that by reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas. This split would be
only about 100 yards but could that be sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any input (pun
intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.

If the problem was generated in your transmitter from mixing with the
paging transmitters it will usually only occur when your repeater
transmitter is on. It sounds like the interference signal is being
generated elsewhere. You should first determine if the problem is in
your installation or from the pagers. I would use a spectrum analyzer or
service monitor at the receive port of your repeater tuned to your
receive frequency to see what it looks like and measure the level. It
may look like a comb generator every time the pagers fire up! You can
then try another antenna into the analyzer to see if the interference
persists or use a directional antenna to see if it’s emanating from the
pager site or yours. Since you mention other repeaters in your area are
suffering from the same problem I would suspect at least one of the
paging transmitters does not have an isolator, which is required at all
sites I have ever dealt with. If you can pick up the interfering signal
on a separate antenna with test equipment and it points to the paging
site, you can demand the pager owners address the problem with isolators
or what ever it takes to minimize the interference.

Photoman wrote:
We have 146.04/.64 repeater on a nearby mountain top. It worked great for
years with a range of 100 miles or more. Since the phone company and a pager
company installed their high power transmitters near the site of the
repeater (within 100 yards) the repeater is virtually useless. After much
head scratching I believe that the difference in frequency of the pager
transmitter of 600 khz is the problem but have no idea how to solve the
problem without going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The transmitter and receiver
on the repeater are both Motorola Micor and were modified with to the
repeater frequencies by FCC 1st class licensed hams using Motorola parts.
This is not an equipment problem. We are running a set of Wacom cavities
which were bought new and are correctly tuned and the antenna is a
Phelps-Dodge Stationmaster. When the intermod occurs it is dependant on BOTH
pagers transmitting at the same time. If only one pager is transmitting
there is no problem. This may at first sound unusual but the pagers are in
the 150 mhz band and they are exactly 600 kc apart. These transmitter are
both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers) is mixing with the
output of the repeater 146.64 and producing the 146.04 signal, the repeater
input frequency. We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the repeater drops. The
intermod cannot hold up the machine once the tone is removed. This may be
happening in the antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this conclusion.

We are not the only 2 meter repeater that has fallen victim of this problem
and in every case we have found two pager transmitters situated 600 kc apart
near the repeater. Most of the other machines have been taken off the air,
others just put up with it. No one has been able to solve the problem and
many technicians have studied it.

Moving the repeater far enough away is not an option since the peak of the
mountain is so small. Also we are using an existing tower which we would not
have access to at other locations. The searches I have done on Google has
turned up the stock answer of helical resonators which would apply to 2
meter radios but not repeaters. If you are familiar with the Micor equipment
you know that the receiver has excellent helical resonators built in.

Tonight I have considered the possibility of splitting the receiver and the
transmitter of the repeater and linking the rx signal by a 220 mhz link. I
am hoping that by reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas. This split would be
only about 100 yards but could that be sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any input (pun
intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.

You failed to indicated if the interference is
present when your own repeater transmitter is off.
First order of business is to eliminate the
non-offending variables. If the interference
is present with the repeater transmitter off,
then it is possible that high-level mixing
is taking place in the final amp of the paging
transmitter or another RF source in close proximity
to your repeater. If you find this is the case,
it can likely be resolved by installing a ferrite
circulator in the line of the offending transmitter.
This will keep the mixing frequency from traveling
down the feedline and entering the final amp
and mixing with another frequency to produce
the "rogue" frequency that is causing the trouble.

Hope this helps.

Good luck.


"Photoman" wrote in
:

We have 146.04/.64 repeater on a nearby mountain top. It
worked great for years with a range of 100 miles or more.
Since the phone company and a pager company installed their
high power transmitters near the site of the repeater
(within 100 yards) the repeater is virtually useless. After
much head scratching I believe that the difference in
frequency of the pager transmitter of 600 khz is the
problem but have no idea how to solve the problem without
going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The
transmitter and receiver on the repeater are both Motorola
Micor and were modified with to the repeater frequencies by
FCC 1st class licensed hams using Motorola parts. This is
not an equipment problem. We are running a set of Wacom
cavities which were bought new and are correctly tuned and
the antenna is a Phelps-Dodge Stationmaster. When the
intermod occurs it is dependant on BOTH pagers transmitting
at the same time. If only one pager is transmitting there
is no problem. This may at first sound unusual but the
pagers are in the 150 mhz band and they are exactly 600 kc
apart. These transmitter are both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers)
is mixing with the output of the repeater 146.64 and
producing the 146.04 signal, the repeater input frequency.
We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the
repeater drops. The intermod cannot hold up the machine
once the tone is removed. This may be happening in the
antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this
conclusion.

We are not the only 2 meter repeater that has fallen victim
of this problem and in every case we have found two pager
transmitters situated 600 kc apart near the repeater. Most
of the other machines have been taken off the air, others
just put up with it. No one has been able to solve the
problem and many technicians have studied it.

Moving the repeater far enough away is not an option since
the peak of the mountain is so small. Also we are using an
existing tower which we would not have access to at other
locations. The searches I have done on Google has turned up
the stock answer of helical resonators which would apply to
2 meter radios but not repeaters. If you are familiar with
the Micor equipment you know that the receiver has
excellent helical resonators built in.

Tonight I have considered the possibility of splitting the
receiver and the transmitter of the repeater and linking
the rx signal by a 220 mhz link. I am hoping that by
reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas.
This split would be only about 100 yards but could that be
sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any
input (pun intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.

You failed to indicated if the interference is
present when your own repeater transmitter is off.
First order of business is to eliminate the
non-offending variables. If the interference
is present with the repeater transmitter off,
then it is possible that high-level mixing
is taking place in the final amp of the paging
transmitter or another RF source in close proximity
to your repeater. If you find this is the case,
it can likely be resolved by installing a ferrite
circulator in the line of the offending transmitter.
This will keep the mixing frequency from traveling
down the feedline and entering the final amp
and mixing with another frequency to produce
the "rogue" frequency that is causing the trouble.

Hope this helps.

Good luck.


"Photoman" wrote in
:

We have 146.04/.64 repeater on a nearby mountain top. It
worked great for years with a range of 100 miles or more.
Since the phone company and a pager company installed their
high power transmitters near the site of the repeater
(within 100 yards) the repeater is virtually useless. After
much head scratching I believe that the difference in
frequency of the pager transmitter of 600 khz is the
problem but have no idea how to solve the problem without
going to an odd split. The repeater coordinator for this
area of Virginia won't even consider that as an option.

The equipment that we are using is excellent. The
transmitter and receiver on the repeater are both Motorola
Micor and were modified with to the repeater frequencies by
FCC 1st class licensed hams using Motorola parts. This is
not an equipment problem. We are running a set of Wacom
cavities which were bought new and are correctly tuned and
the antenna is a Phelps-Dodge Stationmaster. When the
intermod occurs it is dependant on BOTH pagers transmitting
at the same time. If only one pager is transmitting there
is no problem. This may at first sound unusual but the
pagers are in the 150 mhz band and they are exactly 600 kc
apart. These transmitter are both 250 watts or more output.

My theory is that the 600 kc (difference of the 2 pagers)
is mixing with the output of the repeater 146.64 and
producing the 146.04 signal, the repeater input frequency.
We are using sub-audible tone for repeater access and as
soon as a station working the repeater drops carrier the
repeater drops. The intermod cannot hold up the machine
once the tone is removed. This may be happening in the
antenna or hardline connectors prior to the cavities. Every
test I have run, and there have been many, supports this
conclusion.

We are not the only 2 meter repeater that has fallen victim
of this problem and in every case we have found two pager
transmitters situated 600 kc apart near the repeater. Most
of the other machines have been taken off the air, others
just put up with it. No one has been able to solve the
problem and many technicians have studied it.

Moving the repeater far enough away is not an option since
the peak of the mountain is so small. Also we are using an
existing tower which we would not have access to at other
locations. The searches I have done on Google has turned up
the stock answer of helical resonators which would apply to
2 meter radios but not repeaters. If you are familiar with
the Micor equipment you know that the receiver has
excellent helical resonators built in.

Tonight I have considered the possibility of splitting the
receiver and the transmitter of the repeater and linking
the rx signal by a 220 mhz link. I am hoping that by
reducing the level of the 146.64 signal by 50-60 db would
alleviate the problem. Maybe not, but I'm out of ideas.
This split would be only about 100 yards but could that be
sufficient to relieve the problem?

Have any of you ever had this problem and solved it? Any
input (pun intended) on this matter would be appreciated.

Ken Sturgill, KC4IH
Marion VA
please reply to )
REMOVE THE "S" FROM netS in email address to respond.

In article ,
Dave wrote:

You failed to indicated if the interference is
present when your own repeater transmitter is off.
First order of business is to eliminate the
non-offending variables. If the interference
is present with the repeater transmitter off,
then it is possible that high-level mixing
is taking place in the final amp of the paging
transmitter or another RF source in close proximity
to your repeater. If you find this is the case,
it can likely be resolved by installing a ferrite
circulator in the line of the offending transmitter.
This will keep the mixing frequency from traveling
down the feedline and entering the final amp
and mixing with another frequency to produce
the "rogue" frequency that is causing the trouble.

Hope this helps.

Good luck.

And this would required to be done by the FCC, when it was reported to
them. The licensee is REQUIRED to make sure that his Transmitter is
NOT emitting interfering emmissions, and he will certainly fix it as
soon as he is notified of his problem.


Bruce in alaska who used to be an FCC Field Agent.....
--
add a 2 before @