Hello Jeff,
Never did the tests personally but I know from others work where I
used to work that putting 2 RF signals through an isolator of
significant power will produce measurable intermods and with the
powers of a typical transmitter, definitely a problem.
There were problems with just the co
At 10/24/2007 19:46, you wrote:
>145.25 can be a real pain. We have a repeater on that frequency. It is CATV
>channel E. We always have leaks from the cable rendering the repeater
>useless in some areas until a call is made to the CATV plant. They go out
>and tighten the screws on an amplifier (le
> Again, the circulator will produce intermod when external strong
> signals enter the antenna port when used as a switch for the duplexer
> and there is transmitter power also going through it. 50 Watts or
> 47dBm to -116dBm receiver sensitivity is 163dBm dynamic range. The
> device is not linear
145.25 can be a real pain. We have a repeater on that frequency. It is CATV
channel E. We always have leaks from the cable rendering the repeater
useless in some areas until a call is made to the CATV plant. They go out
and tighten the screws on an amplifier (left loose by the last tech working
I was referring to using the circulator in place of the T connector in
a duplexer that was being discussed in earlier threads.
An isolator is a circulator with a load on one of the ports.
Again, the circulator will produce intermod when external strong
signals enter the antenna port when used as
Ron Wright wrote:
> Also if packet on VHF and repeater on UHF a simple crossband coupler
> and dual-band antenna will simplify things.
>
> 73, ron, n9ee/r
Yes-greatly!
--
Jim Barbour
WD8CHL
_
From: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of Ken Arck
Sent: Wednesday, October 24, 2007 12:04 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Re: duplexer isolation and reciever noise
budget
At 09:51 AM 10/24/2007, you wrote:
>OK,
Replace the duplexers antenna tee with a circulator. Tune the
circulator as follows: Port A to B to pass TX frequency, port B to C
to pass RX frequency. Port A to Port C isolation should be in the 20dB
range or better and it still protects the transmitter and helps with
mixing. RF from the antenna
At 09:51 AM 10/24/2007, you wrote:
>OK, I have to comment,
>
>An isolator/circulator should not be used in a duplexer at the
>antenna connector when there are other strong signals floating
>around the air that can get into the isolator.
<---Uh...a couple of things here:
1) Did I miss somet
the cans on one side if possible, but it is
> looking more and more like it will not be, so I'm willing to give up
some
> space in the power electronics bay to make space for more cans.
>
>
>
> _
>
> From: Repeater-Builder@yahoogroups.com
> [mailto:[EMAIL PROTE
, ron, n9ee/r
>From: Jim <[EMAIL PROTECTED]>
>Date: 2007/10/24 Wed AM 09:17:56 CDT
>To: Repeater-Builder@yahoogroups.com
>Subject: Re: [Repeater-Builder] Re: duplexer isolation and reciever noise
>budget
>
>
>>> OK - Here are my requirem
>> OK - Here are my requirements for the transmit chain. minimal
>> physical space and minimal insertion loss :-) (ok - too
>> bloody obvious) Tuning simplicity is also a factor. I'm
>> combining 3 transmitters at 144.39, 145.05 +/- 0.04 and 145.25
>> Can you list out some of the other options
On Oct 24, 2007, at 12:37 AM, John Barrett wrote:
> Re splitting the simplex: a circulator with the radio hooked to the
> input, the transmit chain on the standard output, and the receive
> chain feeding the load port is what I was thinking – a relay would
> do the job just as well, but would
: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo
Sent: Tuesday, October 23, 2007 6:43 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: RE: RE: [Repeater-Builder] Re: duplexer isolation and reciever
noise budget
> If I do two antennas, the best I can do
> If I do two antennas, the best I can do is about 30db
> isolation (30ft separation, 6db multi-bay folded dipole
> antenna on bottom, 9db 2m/440 base station antenna on top),
If you can get 30 feet of separation, you'll get more than 30 dB of
isolation. More like 50 dB on VHF, 60 dB or more o
der@yahoogroups.com
Subject: RE: RE: RE: [Repeater-Builder] Re: duplexer isolation and reciever
noise budget
> OK - Here are my requirements for the transmit chain. minimal
> physical space and minimal insertion loss :-) (ok - too
> bloody obvious) Tuning simplicity is also a factor.
> OK - Here are my requirements for the transmit chain. minimal
> physical space and minimal insertion loss :-) (ok - too
> bloody obvious) Tuning simplicity is also a factor. I'm
> combining 3 transmitters at 144.39, 145.05 +/- 0.04 and 145.25
Before we get to what hardware to use, we still ne
onto my trailer ??
_
From: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo
Sent: Monday, October 22, 2007 9:41 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: RE: RE: [Repeater-Builder] Re: duplexer isolation and reciever
noise budget
> Commer
-9460
[EMAIL PROTECTED]
-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of John Barrett
Sent: Monday, October 22, 2007 7:47 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: RE: RE: [Repeater-Builder] Re: duplexer isolation and reciever
noise b
: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of John Barrett
Sent: Monday, October 22, 2007 7:47 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: RE: RE: [Repeater-Builder] Re: duplexer isolation and reciever
noise budget
An isolator wont cause intermod, but it may
On Oct 22, 2007, at 7:19 PM, Ron Wright wrote:
> I am not sure why an isolator would cause intermod.
The fact that they create harmonics unless filtering is done
"downstream" of the output port going toward the antenna, means that
the opportunities for external mixing are increased greatly b
At 07:41 PM 10/22/07, you wrote:
> > I'm proposing a novel application of the circulator (an
> > isolator without the dummy load on one port)..
>
>Yes, I know what you're trying to do, and it's nothing new. UHF Micor
>mobiles have an isolator in the antenna network that routes received RF
>throug
> An isolator wont cause intermod, but it may cause harmonics.
How so? What phenomenon occurs in a ferrite circulator that creates
harmonics but won't generate IMD?
> Commercial installations usually use either a harmonic filter
> and 3db hybrid coupler, or a special type of band pass cavity
> I am not sure why an isolator would cause intermod. Usually
> there are not active or non-linear components in them
An isolator IS a non-linear device.
> and
> they are often used to prevent intermod by preventing outside
> signals from coming in thru the feedline into the transmitter.
As
lder@yahoogroups.com
Subject: Re: RE: RE: [Repeater-Builder] Re: duplexer isolation and reciever
noise budget
I am not sure why an isolator would cause intermod. Usually there are not
active or non-linear components in them and they are often used to prevent
intermod by preventing outside signals f
peater-Builder] Re: duplexer isolation and reciever noise
>budget
>
>> This isn't guessing - its called RESEARCH
>
>When I said guessing, I was talking about quantifying the performance of
>your radios rather than guessing how much isolation you need. In
> This isn't guessing - its called RESEARCH
When I said guessing, I was talking about quantifying the performance of
your radios rather than guessing how much isolation you need. In other
words, make measurements to actually determine how much noise supression and
carrier attenuation you need usi
g - its called RESEARCH
_
From: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo
Sent: Monday, October 22, 2007 3:11 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: RE: [Repeater-Builder] Re: duplexer isolation and reciever
noise budget
> Trans
> Transmit and receive paths will be separate with 30db of
> isolation (either split antennas, or a 30db isolation
> circulator just before the feed to the antenna)
I posted a followup to one of your previous messages regarding using
isolators as a makeshift way of getting more Tx to Rx isolatio
Time to reopen this subject just a little !!
I'm currently looking at Icom V-8000 radios for the simplex and repeater
radios (0.15uV sensitivity (-123dbm) and 75db spurious/image rejection)
The most any transmitter in the system will ever be running is 50 watts
(+47dbm)
Transmit and rec
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Re: duplexer isolation and reciever noise budget
Before I give you an answer I'd want to know where the repeater
is going to be placed. Operation in the 146 and higher portion of
the band is going to be a heck of a lot easier th
Before I give you an answer I'd want to know where the repeater
is going to be placed. Operation in the 146 and higher portion of
the band is going to be a heck of a lot easier than a repeater
in the 145 segment.
both aprs and winlink radios on the same antenna are going to require
some serio
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