RE: [Repeater-Builder] Coax shielding

[Eric Lemmon]

Ian,

Since RG-223 is double-shielded cable and is similar in construction to RG-400, 
it will be fine- provided you are using the connectors specifically made for 
RG-223 which has a larger OD than RG-400.  Please don't even think about using 
LMR-400, 9913F, or any foil/braid cable because of their tendency to generate 
noise.

73, Eric Lemmon WB6FLY
 

-Original Message-
From: Repeater-Builder@yahoogroups.com 
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of kerincom 
Sent: Sunday, June 27, 2010 8:28 AM
To: mail=repeater-buil...@yahoogroups.com
Subject: RE: [Repeater-Builder] Coax shielding

  

Jumpers between the TX ,rx and diplexer are rg223u .I thought of using rg223u 
for the link radio to its antenna because it is only aprox 2-3meters long but I 
felt I should try lmr400 because of the 100% shielding and the link radio is 
just a standard radio that works in either rx or TX mode and not in duplex mode 
 
 
 
 
  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au <http://www.kerinvalecomaudio.com.au/> 
 
---Original Message---
 
From: Eric Lemmon <mailto:wb6...@verizon.net> 
Date: 6/28/2010 1:24:37 AM
To: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder@yahoogroups.com> 
Subject: RE: [Repeater-Builder] Coax shielding
 
  

Ian,

RG-213 coax can definitely contribute to desense, as can cheap connectors and 
adapters. I suggest making up new jumpers using double-shielded coax such as 
RG-400 or RG-214, and fit these jumpers with high-quality, crimp-on connectors 
of the correct type on each end so that no adapters or barrels are needed. 
Don't use LMR400 or similar foil-and-braid cable, as that will add entirely new 
problems to the mix. If changing the jumpers still leaves some desense, then 
try increasing the spacing between the link and main antennas- lowering the 
link antenna should be the first step.

73, Eric Lemmon WB6FLY


-Original Message-
From: Repeater-Builder@yahoogroups.com 
<mailto:Repeater-Builder%40yahoogroups.com>  
[mailto:Repeater-Builder@yahoogroups.com 
<mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of kerincom 
Sent: Sunday, June 27, 2010 7:51 AM
To: mail=repeater-buil...@yahoogroups.com 
<mailto:mail%3DRepeater-Builder%40yahoogroups.com> 
Subject: [Repeater-Builder] Coax shielding

Hi guys .I am just wanted to confirm a question on coax shielding .
With 2-10 watts transmitting through rg213u could rf be escaping that could 
cause desensitization to other radios .The repeater I have setup uses 9 meters 
of heliax from the main diplexer to ant and rg213u from the link radio to its 
antenna .
I am finding I am getting problems with the link transmission interfering with 
the repeater rx The link antenna is a yagi 3 meters above the ground and the 
main repeater antenna is 6 meters above it .I am currently trying band pass 
cavity on the receiver rx or band pass/band reject diplexer with some success 
but I am wondering if the rf escaping from the cable is causing problems inside 
the repeater shed even at a low wattage .I am definitely changing the rg213u to 
either rg223u or lmr400 as it is only on the link radio and shouldn't have any 
effect on the repeater's operation .Has anyone else had the same sort of 
problem where the rf energy leaks out of the cable in the shed and causes 
problems to the repeater and they had to upgrade the link cable to 100% 
coverage cable


  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au <http://www.kerinvalecomaudio.com.au 
<http://www.kerinvalecomaudio.com.au> > 



 

Re: [Repeater-Builder] Coax shielding

[Doug Bade]

While your logic is good on this, a Pass/Reject would help THAT 
transmitter be more friendly to other receivers... and protect from raw 
RF overload from other near-but-not-on-frequency transmitters... but the 
noise geration issue ( part 2 of my general site comments) needs to be 
plugged up on the tx that is causing itso filters need to be on the 
link TX itself... especially if you want to keep the link frequency 
agile.. the proposed notch filters would allow the link to be moved if 
you needed, as long as you stay at least 1 mhz away from  the notched 
478 frequency... Now.. if there are ever more receivers on site, those 
cases will need to be addressed with better filtering or antenna 
spacing  :-)
Doug


kerincom wrote:
>  
>
> That's what I thought as I am currently using a 6ld450s notch diplexer 
> and should change it to a band pass/band reject diplexer .I tried a 
> experiment on site where I added 1 cavity inline with the receiver 
> 478.675 and it seemed to improve the problem  .so that was going to be 
> the next step but I thought I might see what the thoughts were on the 
> coax leaking
>  
>  
>  
>  
>  
> Thank You,
> Ian Wells,
> Kerinvale Comaudio,
> 3A Murchison Street,Biloela.4715
> Ph 0749922449 or 0409159932 or 0749922574
> www.kerinvalecomaudio.com.au <http://www.kerinvalecomaudio.com.au/>
>  
> /---Original Message---/
>  
> /*From:*/ Doug Bade <mailto:k...@thebades.net>
> /*Date:*/ 6/28/2010 1:44:27 AM
> /*To:*/ Repeater-Builder@yahoogroups.com 
> <mailto:Repeater-Builder@yahoogroups.com>
> /*Subject:*/ Re: [Repeater-Builder] Coax shielding
>  
>  
>
> Ian;
> It would seem that at uhf ~30mhz away cable leakage in the shed
> would seem to be less likely than antenna to antenna interference. In
> general it is the white noise generated by a transmitter on other
> frequencies that is most likely to cause desense to a co located rx.
>
> Assuming you have double shielded or better on the repeater, the leakage
> in the shed from the single shielded link radio would not seem to
> radiate enough to be an issue. If the radio side of the main duplexer is
> also rg213, well that is another matter :-)
> If you are using a notch only duplexer for the main duplexer, it would
> not protect you from another transmitter besides it's own.. Typical
> mobile type size duplexers at UHF are really only designed to protect
> the rx from it's local tx, any other can slip right in..
>
> I would try a notch filter ( or half a notch duplexer ) on the link tx
> to suppress the station rx frequency from it's output.. that noise is
> probably the culprit..
>
> As said by others, good double shielded cables and /or 100 % corrugated
> types are suggested in sites with multiple transmitters to deal with..
> but most on site desense I have dealt with from other transmitters comes
> from one of 2 things.. raw power front end overload of the rx when the
> antennas can see each other... or white noise generated on broad
> frequencies from an unfiltered transmitter. I am suggesting a notch
> cavity on the 517 transmitter output that notches 478.675 in this case..
> 3 slugs ( one side) on a mobile duplexer will suppress that noise ~65db,
> and provide no significant insertion loss to the link tx..And double
> shielded cables like RG142 for radio to filter connections is perfectly
> adequate up to 520 mhz and beyond... with isolation to -120dbm at a
> minimum..
>
> Doug
> KD8B
>
> kerincom wrote:
> >
> >
> > Uhf the link is 517mhz and the repeater TX/rx pair is 473.475 and
> > 478.675mhz on one repeater and it is in a weak area with the main
> > site so it has to transmitt aprox 10 watts
> >
> >
> >
> >
> > kerincom wrote:
> > >
> > >
> > > Hi guys .I am just wanted to confirm a question on coax shielding .
> > > With 2-10 watts transmitting through rg213u could rf be escaping that
> > > could cause desensitization to other radios .The repeater I have
> > > setup uses 9 meters of heliax from the main diplexer to ant and
> > > rg213u from the link radio to its antenna .
> > > I am finding I am getting problems with the link
> > > transmission interfering with the repeater rx The link antenna is a
> > > yagi 3 meters above the ground and the main repeater antenna is 6
> > > meters above it .I am currently trying band pass cavity on the
> > > receiver rx or band pass/band reject diplexer with some success but I
> > > am wondering if the rf escaping from the cable is causing problems
> > > inside the repeater shed even at a low wattage .I am definitely
> > > changing the rg213u to either rg223u or lmr400 as it is only on the
> > > link radio and shouldn't have any effect on the repeater's operation
> > > .Has anyone else had the same sort of problem where the rf energy
> > > leaks out of the cable in the shed and causes problems to the repeater
> > > and they had to upgrade the link cable to 100% coverage cable
> >
> >
> >
> >
> >
> >
>
>  
>
>   
>
> 

Re: [Repeater-Builder] Coax shielding

[kerincom]

Ok thanks .I will upgrade the diplexer and see how that goes I might have to
change all my repeaters the same . 
 
 
 
 
  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au
 
---Original Message---
 
From: Doug Bade
Date: 6/28/2010 2:08:45 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Coax shielding
 
  
In theory most xtal radios are quieter than synthesized ones, but a 
filter would seem to be the better thing to do as it really stops the 
problem...even a bandpass can or 2 on the link radio would be acceptable 
if a notch is not available.. I just offered a notch duplexer option as 
they can be bought sub 150.00 usd... and probably a lot less off ebay..

"I" would fix the noise potential rather than swap the tx for another 
model.. but I have different options available to me than maybe you 
do... If the site were at a "remote" location for me.. I try to make it 
bulletproof so I do not have to deal with it.. :-)

Doug

kerincom wrote:
> 
>
> Would it be better to change the link radio to crystal instead of 
> programmed .It is currently a tait t2010 
> 
> 
> 
> 
>  
> Thank You,
> Ian Wells,
> Kerinvale Comaudio,
> 3A Murchison Street,Biloela.4715
> Ph 0749922449 or 0409159932 or 0749922574
> www.kerinvalecomaudio.com.au <http://www.kerinvalecomaudio.com.au/>
> 
> /---Original Message---/
> 
> /*From:*/ Doug Bade <mailto:k...@thebades.net>
> /*Date:*/ 6/28/2010 1:44:27 AM
> /*To:*/ Repeater-Builder@yahoogroups.com 
> <mailto:Repeater-Builder@yahoogroups.com>
> /*Subject:*/ Re: [Repeater-Builder] Coax shielding
> 
> 
>
> Ian;
> It would seem that at uhf ~30mhz away cable leakage in the shed
> would seem to be less likely than antenna to antenna interference. In
> general it is the white noise generated by a transmitter on other
> frequencies that is most likely to cause desense to a co located rx.
>
> Assuming you have double shielded or better on the repeater, the leakage
> in the shed from the single shielded link radio would not seem to
> radiate enough to be an issue. If the radio side of the main duplexer is
> also rg213, well that is another matter :-)
> If you are using a notch only duplexer for the main duplexer, it would
> not protect you from another transmitter besides it's own.. Typical
> mobile type size duplexers at UHF are really only designed to protect
> the rx from it's local tx, any other can slip right in..
>
> I would try a notch filter ( or half a notch duplexer ) on the link tx
> to suppress the station rx frequency from it's output.. that noise is
> probably the culprit..
>
> As said by others, good double shielded cables and /or 100 % corrugated
> types are suggested in sites with multiple transmitters to deal with..
> but most on site desense I have dealt with from other transmitters comes
> from one of 2 things.. raw power front end overload of the rx when the
> antennas can see each other... or white noise generated on broad
> frequencies from an unfiltered transmitter. I am suggesting a notch
> cavity on the 517 transmitter output that notches 478.675 in this case..
> 3 slugs ( one side) on a mobile duplexer will suppress that noise ~65db,
> and provide no significant insertion loss to the link tx..And double
> shielded cables like RG142 for radio to filter connections is perfectly
> adequate up to 520 mhz and beyond... with isolation to -120dbm at a
> minimum..
>
> Doug
> KD8B
>
> kerincom wrote:
> >
> >
> > Uhf the link is 517mhz and the repeater TX/rx pair is 473.475 and
> > 478.675mhz on one repeater and it is in a weak area with the main
> > site so it has to transmitt aprox 10 watts
> >
> >
> >
> >
> > kerincom wrote:
> > >
> > >
> > > Hi guys .I am just wanted to confirm a question on coax shielding .
> > > With 2-10 watts transmitting through rg213u could rf be escaping that
> > > could cause desensitization to other radios .The repeater I have
> > > setup uses 9 meters of heliax from the main diplexer to ant and
> > > rg213u from the link radio to its antenna .
> > > I am finding I am getting problems with the link
> > > transmission interfering with the repeater rx The link antenna is a
> > > yagi 3 meters above the ground and the main repeater antenna is 6
> > > meters above it .I am currently trying band pass cavity on the
> > > receiver rx or band pass/band reject diplexer with some success but I
> > > am wondering if the rf escaping from the cable is causing problems
> > > inside the repeater shed even at a low wattage .I am definitely
> > > changing the rg213u to either rg223u or lmr400 as it is only on the
> > > link radio and shouldn't have any effect on the repeater's operation
> > > .Has anyone else had the same sort of problem where the rf energy
> > > leaks out of the cable in the shed and causes problems to the repeater
> > > and they had to upgrade the link cable to 100% coverage cable
> >
> >
> >
> >
> >
> >
>
> 
>
> 
>
> 



 

Re: [Repeater-Builder] Coax shielding

[Doug Bade]

In theory most xtal radios are quieter than synthesized ones, but a 
filter would seem to be the better thing to do as it really stops the 
problem...even a bandpass can or 2 on the link radio would be acceptable 
if a notch is not available.. I just offered a notch duplexer option as 
they can be bought sub 150.00 usd... and probably a lot less off ebay..

"I" would fix the noise potential rather than swap the tx for another 
model.. but I have different options available to me than maybe you 
do... If the site were at a "remote" location for me.. I try to make it 
bulletproof so I do not have to deal with it.. :-)

Doug

kerincom wrote:
>  
>
> Would it be better to change the link radio to crystal instead of 
> programmed .It is currently a tait t2010 
>  
>  
>  
>  
>  
> Thank You,
> Ian Wells,
> Kerinvale Comaudio,
> 3A Murchison Street,Biloela.4715
> Ph 0749922449 or 0409159932 or 0749922574
> www.kerinvalecomaudio.com.au <http://www.kerinvalecomaudio.com.au/>
>  
> /---Original Message---/
>  
> /*From:*/ Doug Bade <mailto:k...@thebades.net>
> /*Date:*/ 6/28/2010 1:44:27 AM
> /*To:*/ Repeater-Builder@yahoogroups.com 
> <mailto:Repeater-Builder@yahoogroups.com>
> /*Subject:*/ Re: [Repeater-Builder] Coax shielding
>  
>  
>
> Ian;
> It would seem that at uhf ~30mhz away cable leakage in the shed
> would seem to be less likely than antenna to antenna interference. In
> general it is the white noise generated by a transmitter on other
> frequencies that is most likely to cause desense to a co located rx.
>
> Assuming you have double shielded or better on the repeater, the leakage
> in the shed from the single shielded link radio would not seem to
> radiate enough to be an issue. If the radio side of the main duplexer is
> also rg213, well that is another matter :-)
> If you are using a notch only duplexer for the main duplexer, it would
> not protect you from another transmitter besides it's own.. Typical
> mobile type size duplexers at UHF are really only designed to protect
> the rx from it's local tx, any other can slip right in..
>
> I would try a notch filter ( or half a notch duplexer ) on the link tx
> to suppress the station rx frequency from it's output.. that noise is
> probably the culprit..
>
> As said by others, good double shielded cables and /or 100 % corrugated
> types are suggested in sites with multiple transmitters to deal with..
> but most on site desense I have dealt with from other transmitters comes
> from one of 2 things.. raw power front end overload of the rx when the
> antennas can see each other... or white noise generated on broad
> frequencies from an unfiltered transmitter. I am suggesting a notch
> cavity on the 517 transmitter output that notches 478.675 in this case..
> 3 slugs ( one side) on a mobile duplexer will suppress that noise ~65db,
> and provide no significant insertion loss to the link tx..And double
> shielded cables like RG142 for radio to filter connections is perfectly
> adequate up to 520 mhz and beyond... with isolation to -120dbm at a
> minimum..
>
> Doug
> KD8B
>
> kerincom wrote:
> >
> >
> > Uhf the link is 517mhz and the repeater TX/rx pair is 473.475 and
> > 478.675mhz on one repeater and it is in a weak area with the main
> > site so it has to transmitt aprox 10 watts
> >
> >
> >
> >
> > kerincom wrote:
> > >
> > >
> > > Hi guys .I am just wanted to confirm a question on coax shielding .
> > > With 2-10 watts transmitting through rg213u could rf be escaping that
> > > could cause desensitization to other radios .The repeater I have
> > > setup uses 9 meters of heliax from the main diplexer to ant and
> > > rg213u from the link radio to its antenna .
> > > I am finding I am getting problems with the link
> > > transmission interfering with the repeater rx The link antenna is a
> > > yagi 3 meters above the ground and the main repeater antenna is 6
> > > meters above it .I am currently trying band pass cavity on the
> > > receiver rx or band pass/band reject diplexer with some success but I
> > > am wondering if the rf escaping from the cable is causing problems
> > > inside the repeater shed even at a low wattage .I am definitely
> > > changing the rg213u to either rg223u or lmr400 as it is only on the
> > > link radio and shouldn't have any effect on the repeater's operation
> > > .Has anyone else had the same sort of problem where the rf energy
> > > leaks out of the cable in the shed and causes problems to the repeater
> > > and they had to upgrade the link cable to 100% coverage cable
> >
> >
> >
> >
> >
> >
>
>  
>
>   
>
> 

Re: [Repeater-Builder] Coax shielding

[kerincom]

That's what I thought as I am currently using a 6ld450s notch diplexer and
should change it to a band pass/band reject diplexer .I tried a experiment
on site where I added 1 cavity inline with the receiver 478.675 and it
seemed to improve the problem  .so that was going to be the next step but I
thought I might see what the thoughts were on the coax leaking 
 
 
 
 
  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au
 
---Original Message---
 
From: Doug Bade
Date: 6/28/2010 1:44:27 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Coax shielding
 
  
Ian;
It would seem that at uhf ~30mhz away cable leakage in the shed 
would seem to be less likely than antenna to antenna interference. In 
general it is the white noise generated by a transmitter on other 
frequencies that is most likely to cause desense to a co located rx.

Assuming you have double shielded or better on the repeater, the leakage 
in the shed from the single shielded link radio would not seem to 
radiate enough to be an issue. If the radio side of the main duplexer is 
also rg213, well that is another matter :-)
If you are using a notch only duplexer for the main duplexer, it would 
not protect you from another transmitter besides it's own.. Typical 
mobile type size duplexers at UHF are really only designed to protect 
the rx from it's local tx, any other can slip right in..

I would try a notch filter ( or half a notch duplexer ) on the link tx 
to suppress the station rx frequency from it's output.. that noise is 
probably the culprit..

As said by others, good double shielded cables and /or 100 % corrugated 
types are suggested in sites with multiple transmitters to deal with.. 
but most on site desense I have dealt with from other transmitters comes 
from one of 2 things.. raw power front end overload of the rx when the 
antennas can see each other... or white noise generated on broad 
frequencies from an unfiltered transmitter. I am suggesting a notch 
cavity on the 517 transmitter output that notches 478.675 in this case.. 
3 slugs ( one side) on a mobile duplexer will suppress that noise ~65db, 
and provide no significant insertion loss to the link tx..And double 
shielded cables like RG142 for radio to filter connections is perfectly 
adequate up to 520 mhz and beyond... with isolation to -120dbm at a 
minimum..

Doug
KD8B

kerincom wrote:
> 
>
> Uhf the link is 517mhz and the repeater TX/rx pair is 473.475 and 
> 478.675mhz on one repeater and it is in a weak area with the main 
> site so it has to transmitt aprox 10 watts 
> 
> 
>
>
> kerincom wrote:
> >
> >
> > Hi guys .I am just wanted to confirm a question on coax shielding .
> > With 2-10 watts transmitting through rg213u could rf be escaping that
> > could cause desensitization to other radios .The repeater I have
> > setup uses 9 meters of heliax from the main diplexer to ant and
> > rg213u from the link radio to its antenna .
> > I am finding I am getting problems with the link
> > transmission interfering with the repeater rx The link antenna is a
> > yagi 3 meters above the ground and the main repeater antenna is 6
> > meters above it .I am currently trying band pass cavity on the
> > receiver rx or band pass/band reject diplexer with some success but I
> > am wondering if the rf escaping from the cable is causing problems
> > inside the repeater shed even at a low wattage .I am definitely
> > changing the rg213u to either rg223u or lmr400 as it is only on the
> > link radio and shouldn't have any effect on the repeater's operation
> > .Has anyone else had the same sort of problem where the rf energy
> > leaks out of the cable in the shed and causes problems to the repeater
> > and they had to upgrade the link cable to 100% coverage cable
>
> 
>
> 
>
> 



 

Re: [Repeater-Builder] Coax shielding

[kerincom]

Would it be better to change the link radio to crystal instead of programmed
.It is currently a tait t2010 
 
 
 
 
  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au
 
---Original Message---
 
From: Doug Bade
Date: 6/28/2010 1:44:27 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Coax shielding
 
  
Ian;
It would seem that at uhf ~30mhz away cable leakage in the shed 
would seem to be less likely than antenna to antenna interference. In 
general it is the white noise generated by a transmitter on other 
frequencies that is most likely to cause desense to a co located rx.

Assuming you have double shielded or better on the repeater, the leakage 
in the shed from the single shielded link radio would not seem to 
radiate enough to be an issue. If the radio side of the main duplexer is 
also rg213, well that is another matter :-)
If you are using a notch only duplexer for the main duplexer, it would 
not protect you from another transmitter besides it's own.. Typical 
mobile type size duplexers at UHF are really only designed to protect 
the rx from it's local tx, any other can slip right in..

I would try a notch filter ( or half a notch duplexer ) on the link tx 
to suppress the station rx frequency from it's output.. that noise is 
probably the culprit..

As said by others, good double shielded cables and /or 100 % corrugated 
types are suggested in sites with multiple transmitters to deal with.. 
but most on site desense I have dealt with from other transmitters comes 
from one of 2 things.. raw power front end overload of the rx when the 
antennas can see each other... or white noise generated on broad 
frequencies from an unfiltered transmitter. I am suggesting a notch 
cavity on the 517 transmitter output that notches 478.675 in this case.. 
3 slugs ( one side) on a mobile duplexer will suppress that noise ~65db, 
and provide no significant insertion loss to the link tx..And double 
shielded cables like RG142 for radio to filter connections is perfectly 
adequate up to 520 mhz and beyond... with isolation to -120dbm at a 
minimum..

Doug
KD8B

kerincom wrote:
> 
>
> Uhf the link is 517mhz and the repeater TX/rx pair is 473.475 and 
> 478.675mhz on one repeater and it is in a weak area with the main 
> site so it has to transmitt aprox 10 watts 
> 
> 
>
>
> kerincom wrote:
> >
> >
> > Hi guys .I am just wanted to confirm a question on coax shielding .
> > With 2-10 watts transmitting through rg213u could rf be escaping that
> > could cause desensitization to other radios .The repeater I have
> > setup uses 9 meters of heliax from the main diplexer to ant and
> > rg213u from the link radio to its antenna .
> > I am finding I am getting problems with the link
> > transmission interfering with the repeater rx The link antenna is a
> > yagi 3 meters above the ground and the main repeater antenna is 6
> > meters above it .I am currently trying band pass cavity on the
> > receiver rx or band pass/band reject diplexer with some success but I
> > am wondering if the rf escaping from the cable is causing problems
> > inside the repeater shed even at a low wattage .I am definitely
> > changing the rg213u to either rg223u or lmr400 as it is only on the
> > link radio and shouldn't have any effect on the repeater's operation
> > .Has anyone else had the same sort of problem where the rf energy
> > leaks out of the cable in the shed and causes problems to the repeater
> > and they had to upgrade the link cable to 100% coverage cable
>
> 
>
> 
>
> 



 

Re: [Repeater-Builder] Coax shielding

[Doug Bade]

Ian;
It would seem that at uhf ~30mhz away cable leakage in the shed 
would seem to be less likely than antenna to antenna interference. In 
general it is the white noise generated by a transmitter on other 
frequencies that is most likely to cause desense to a co located rx.

Assuming you have double shielded or better on the repeater, the leakage 
in the shed from the single shielded link radio would not seem to 
radiate enough to be an issue. If the radio side of the main duplexer is 
also rg213, well that is another matter :-)
If you are using a notch only duplexer for the main duplexer, it would 
not protect you from another transmitter besides it's own.. Typical 
mobile type size duplexers at UHF are really only designed to protect 
the rx from it's local tx, any other can slip right in..

I would try a notch filter  ( or half a notch duplexer ) on the link tx  
to suppress the station rx frequency from it's output.. that noise is 
probably the culprit..

As said by others, good double shielded cables and /or 100 % corrugated 
types are suggested in sites with multiple transmitters to deal with.. 
but most on site desense I have dealt with from other transmitters comes 
from one of 2 things.. raw power front end overload of the rx when the 
antennas can see each other... or white noise generated on broad 
frequencies from an unfiltered transmitter. I am suggesting a notch 
cavity on the 517 transmitter output that notches 478.675 in this case.. 
3 slugs ( one side) on a mobile duplexer will suppress that noise ~65db, 
and provide no significant insertion loss to the link tx..And double 
shielded cables like RG142 for radio to filter connections is perfectly 
adequate up to 520 mhz and beyond... with isolation to -120dbm at a 
minimum..

Doug
KD8B


kerincom wrote:
>  
>
> Uhf the link is 517mhz and the repeater TX/rx pair is 473.475 and 
> 478.675mhz on one repeater and it is in a weak area  with the main 
> site so it has to transmitt aprox 10 watts 
>  
>  
>
>
> kerincom wrote:
> >
> >
> > Hi guys .I am just wanted to confirm a question on coax shielding .
> > With 2-10 watts transmitting through rg213u could rf be escaping that
> > could cause desensitization to other radios .The repeater I have
> > setup uses 9 meters of heliax from the main diplexer to ant and
> > rg213u from the link radio to its antenna .
> > I am finding I am getting problems with the link
> > transmission interfering with the repeater rx The link antenna is a
> > yagi 3 meters above the ground and the main repeater antenna is 6
> > meters above it .I am currently trying band pass cavity on the
> > receiver rx or band pass/band reject diplexer with some success but I
> > am wondering if the rf escaping from the cable is causing problems
> > inside the repeater shed even at a low wattage .I am definitely
> > changing the rg213u to either rg223u or lmr400 as it is only on the
> > link radio and shouldn't have any effect on the repeater's operation
> > .Has anyone else had the same sort of problem where the rf energy
> > leaks out of the cable in the shed and causes problems to the repeater
> > and they had to upgrade the link cable to 100% coverage cable
>
>  
>
>   
>
> 

RE: [Repeater-Builder] Coax shielding

[kerincom]

Jumpers between the TX ,rx and diplexer are rg223u .I thought of using
rg223u for the link radio to its antenna because it is only aprox 2-3meters
long but I felt I should try lmr400 because of the 100% shielding and the
link radio is just a standard radio that works in either rx or TX mode and
not in duplex mode 
 
 
 
 
  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au
 
---Original Message---
 
From: Eric Lemmon
Date: 6/28/2010 1:24:37 AM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Coax shielding
 
  
Ian,

RG-213 coax can definitely contribute to desense, as can cheap connectors
and adapters. I suggest making up new jumpers using double-shielded coax
such as RG-400 or RG-214, and fit these jumpers with high-quality, crimp-on
connectors of the correct type on each end so that no adapters or barrels
are needed. Don't use LMR400 or similar foil-and-braid cable, as that will
add entirely new problems to the mix. If changing the jumpers still leaves
some desense, then try increasing the spacing between the link and main
antennas- lowering the link antenna should be the first step.

73, Eric Lemmon WB6FLY


-Original Message-
From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups
com] On Behalf Of kerincom 
Sent: Sunday, June 27, 2010 7:51 AM
To: mail=repeater-buil...@yahoogroups.com
Subject: [Repeater-Builder] Coax shielding

Hi guys .I am just wanted to confirm a question on coax shielding .
With 2-10 watts transmitting through rg213u could rf be escaping that could
cause desensitization to other radios .The repeater I have setup uses 9
meters of heliax from the main diplexer to ant and rg213u from the link
radio to its antenna .
I am finding I am getting problems with the link transmission interfering
with the repeater rx The link antenna is a yagi 3 meters above the ground
and the main repeater antenna is 6 meters above it .I am currently trying
band pass cavity on the receiver rx or band pass/band reject diplexer with
some success but I am wondering if the rf escaping from the cable is causing
problems inside the repeater shed even at a low wattage .I am definitely
changing the rg213u to either rg223u or lmr400 as it is only on the link
radio and shouldn't have any effect on the repeater's operation .Has anyone
else had the same sort of problem where the rf energy leaks out of the cable
in the shed and causes problems to the repeater and they had to upgrade the
link cable to 100% coverage cable


  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au <http://www.kerinvalecomaudio.com.au> 



 

RE: [Repeater-Builder] Coax shielding

[Eric Lemmon]

Ian,

RG-213 coax can definitely contribute to desense, as can cheap connectors and 
adapters.  I suggest making up new jumpers using double-shielded coax such as 
RG-400 or RG-214, and fit these jumpers with high-quality, crimp-on connectors 
of the correct type on each end so that no adapters or barrels are needed.  
Don't use LMR400 or similar foil-and-braid cable, as that will add entirely new 
problems to the mix.  If changing the jumpers still leaves some desense, then 
try increasing the spacing between the link and main antennas- lowering the 
link antenna should be the first step.

73, Eric Lemmon WB6FLY
 

-Original Message-
From: Repeater-Builder@yahoogroups.com 
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of kerincom 
Sent: Sunday, June 27, 2010 7:51 AM
To: mail=repeater-buil...@yahoogroups.com
Subject: [Repeater-Builder] Coax shielding

  

Hi guys .I am just wanted to confirm a question on coax shielding .
With 2-10 watts transmitting through rg213u  could rf be escaping that could 
cause desensitization  to other radios .The repeater I have setup uses 9 meters 
of heliax from the main diplexer to ant  and rg213u from the link radio to its 
antenna  .
I am finding I am getting problems with the link transmission interfering with 
the  repeater rx The link antenna is a yagi 3 meters above the ground and the 
main repeater antenna is 6 meters above it .I am currently trying band pass 
cavity on the receiver rx or band pass/band reject diplexer with some success 
but I am wondering if the rf escaping from the cable is causing problems inside 
the repeater shed even at a low wattage .I am definitely changing the rg213u to 
either rg223u or lmr400 as it is only on the link radio and shouldn't have any 
effect on the repeater's operation .Has anyone else had the same sort of 
problem where the rf energy leaks out of the cable in the shed and causes 
problems to the repeater and they had to upgrade the link cable to 100% 
coverage cable
 
 
  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au  

Re: [Repeater-Builder] Coax shielding

[kerincom]

Uhf the link is 517mhz and the repeater TX/rx pair is 473.475 and 478.675mhz
on one repeater and it is in a weak area  with the main site so it has to
transmitt aprox 10 watts 
 
 
 
 
  
Thank You,
Ian Wells,
Kerinvale Comaudio,
3A Murchison Street,Biloela.4715
Ph 0749922449 or 0409159932 or 0749922574
www.kerinvalecomaudio.com.au
 
---Original Message---
 
From: Doug Bade
Date: 6/28/2010 12:59:24 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Coax shielding
 
  
At UHF, possibly, at VHF unlikely... you did not specify :-)
How close are the frequencies??? Lots of details left out for us to help.
If the freq's are within a few hundred kiloherts at vhf, antenna 
separation is probably the issue...
More details please??
Doug
KD8B

kerincom wrote:
> 
>
> Hi guys .I am just wanted to confirm a question on coax shielding .
> With 2-10 watts transmitting through rg213u could rf be escaping that 
> could cause desensitization to other radios .The repeater I have 
> setup uses 9 meters of heliax from the main diplexer to ant and 
> rg213u from the link radio to its antenna .
> I am finding I am getting problems with the link 
> transmission interfering with the repeater rx The link antenna is a 
> yagi 3 meters above the ground and the main repeater antenna is 6 
> meters above it .I am currently trying band pass cavity on the 
> receiver rx or band pass/band reject diplexer with some success but I 
> am wondering if the rf escaping from the cable is causing problems 
> inside the repeater shed even at a low wattage .I am definitely 
> changing the rg213u to either rg223u or lmr400 as it is only on the 
> link radio and shouldn't have any effect on the repeater's operation 
> .Has anyone else had the same sort of problem where the rf energy 
> leaks out of the cable in the shed and causes problems to the repeater 
> and they had to upgrade the link cable to 100% coverage cable
> 
> 
>  
> Thank You,
> Ian Wells,
> Kerinvale Comaudio,
> 3A Murchison Street,Biloela.4715
> Ph 0749922449 or 0409159932 or 0749922574
> www.kerinvalecomaudio.com.au <http://www.kerinvalecomaudio.com.au>
> 
>
> 
>
> 



 

RE: [Repeater-Builder] Coax shielding

[Mike Besemer (WM4B)]

I think the coax causing issues is a reasonable assumption… and probably the 
easiest thing to try.  

 

Good luck.

 

73,

 

Mike

WM4B

 

  _  

From: Repeater-Builder@yahoogroups.com 
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of kerincom 
Sent: Sunday, June 27, 2010 10:51 AM
To: mail=repeater-buil...@yahoogroups.com
Subject: [Repeater-Builder] Coax shielding

 

  


Hi guys .I am just wanted to confirm a question on coax shielding .

With 2-10 watts transmitting through rg213u  could rf be escaping that could 
cause desensitization  to other radios .The repeater I have setup uses 9 meters 
of heliax from the main diplexer to ant  and rg213u from the link radio to its 
antenna  .

I am finding I am getting problems with the link transmission interfering with 
the  repeater rx The link antenna is a yagi 3 meters above the ground and the 
main repeater antenna is 6 meters above it .I am currently trying band pass 
cavity on the receiver rx or band pass/band reject diplexer with some success 
but I am wondering if the rf escaping from the cable is causing problems inside 
the repeater shed even at a low wattage .I am definitely changing the rg213u to 
either rg223u or lmr400 as it is only on the link radio and shouldn't have any 
effect on the repeater's operation .Has anyone else had the same sort of 
problem where the rf energy leaks out of the cable in the shed and causes 
problems to the repeater and they had to upgrade the link cable to 100% 
coverage cable

 

 

  

Thank You,

Ian Wells,

Kerinvale Comaudio,

3A Murchison Street,Biloela.4715

Ph 0749922449 or 0409159932 or 0749922574

www.kerinvalecomaud  io.com.au

 



 

 

Re: [Repeater-Builder] Coax shielding

[Doug Bade]

At UHF, possibly, at VHF unlikely... you did not specify :-)
How close are the frequencies??? Lots of details left out for us to help.
If the freq's are within a few hundred kiloherts at vhf, antenna 
separation is probably the issue...
More details please??
Doug
KD8B


kerincom wrote:
>  
>
> Hi guys .I am just wanted to confirm a question on coax shielding .
> With 2-10 watts transmitting through rg213u  could rf be escaping that 
> could cause desensitization  to other radios .The repeater I have 
> setup uses 9 meters of heliax from the main diplexer to ant  and 
> rg213u from the link radio to its antenna  .
> I am finding I am getting problems with the link 
> transmission interfering with the  repeater rx The link antenna is a 
> yagi 3 meters above the ground and the main repeater antenna is 6 
> meters above it .I am currently trying band pass cavity on the 
> receiver rx or band pass/band reject diplexer with some success but I 
> am wondering if the rf escaping from the cable is causing problems 
> inside the repeater shed even at a low wattage .I am definitely 
> changing the rg213u to either rg223u or lmr400 as it is only on the 
> link radio and shouldn't have any effect on the repeater's operation 
> .Has anyone else had the same sort of problem where the rf energy 
> leaks out of the cable in the shed and causes problems to the repeater 
> and they had to upgrade the link cable to 100% coverage cable
>  
>  
>  
> Thank You,
> Ian Wells,
> Kerinvale Comaudio,
> 3A Murchison Street,Biloela.4715
> Ph 0749922449 or 0409159932 or 0749922574
> www.kerinvalecomaudio.com.au 
>  
>
>   
>
>