: skipp025
To: Repeater-Builder@yahoogroups.com
Sent: Sunday, June 29, 2008 10:24 PM
Subject: [Repeater-Builder] Re: Frequency Change do I retune duplexer?
[EMAIL PROTECTED] wrote:
I'm going to disagree here. Gary said he's only moving
12.5 kHz, I've never seen any coaxial
You've never taken a real close-in detailed look at the
notch of a high quality UHF cavity..?
Maybe a dB or two at most.
I actually meant to write High Q UHF Cavity Duplexer Network. I
can clearly see more than a dB or two difference but maybe my
glasses are blurred again.
I claim
Hi Paul,
I go the other way where multiple Duplexer High-Q Series Cavities
have a deep sharp reject notch and a 12.5 KHz shift from F-center
results in a quite noticeable performance change.
cheers,
s.
Paul Plack [EMAIL PROTECTED] wrote:
The answer also needs to account for the fact
At 6/29/2008 22:57, you wrote:
This is why it is best to put about 1-2 db 50 ohm pad between the duplexer
and the receiver, to help keep the receive side at 50 ohm.
And degrade my system sensitivity by that same amount? No thanks. The
duplexer simply has to be able to deal with the mismatch
-
From: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of JOHN MACKEY
Sent: Monday, June 30, 2008 1:58 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Re: Frequency Change do I
retune duplexer?
This is why it is best to put about 1-2 db 50 ohm
Steve S. Bosshard (NU5D) [EMAIL PROTECTED] wrote:
I beg to differ on this one, most respectfully, but we are
talking about the difference between running the transmitter
at 2.5 Khz deviation vs 5.0 Khz, ie, 12.5 Khz occupied band
width, vs, 25 khz occupied band width - does this mean a
No Skipp, deviation was not mentioned, but the frequency change is on
the same magnitude as increasing transmitter deviation - a 12.5 khz
shift in frequency. 73, Steve NU5D
skipp025 wrote:
Steve S. Bosshard (NU5D) [EMAIL PROTECTED] wrote:
I beg to differ on this one, most respectfully, but
This is why it is best to put about 1-2 db 50 ohm pad
between the duplexer
and the receiver, to help keep the receive side at 50 ohm.
And degrade my system sensitivity by that same amount? No thanks.
Maybe I misunderstood - I thought he was suggesting using pads while tuning,
not during
The pad is only used during testing to isolate mismatch between the
signal generator and spectrum analyzer and the device under test - not
to be left in permanently. At WACOM it was standard practice to use a
10 dB pad between the test equipment and the device under test. This is
because it
: Repeater-Builder@yahoogroups.com [mailto:Repeater-
[EMAIL PROTECTED] On Behalf Of skipp025
Sent: Monday, June 30, 2008 1:49 AM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Re: Frequency Change do I retune duplexer?
Hi Paul,
I go the other way where multiple Duplexer High-Q
Steve S. Bosshard (NU5D) [EMAIL PROTECTED] wrote:
No Skipp, deviation was not mentioned, but the frequency change is on
the same magnitude as increasing transmitter deviation - a 12.5 khz
shift in frequency. 73, Steve NU5D
OK, if you think they are the same... fine with me.
cheers,
s.
At 6/30/2008 08:48, you wrote:
This is why it is best to put about 1-2 db 50 ohm pad
between the duplexer
and the receiver, to help keep the receive side at 50 ohm.
And degrade my system sensitivity by that same amount? No thanks.
Maybe I misunderstood - I thought he was suggesting
At 6/30/2008 08:53, you wrote:
The pad is only used during testing to isolate mismatch between the
signal generator and spectrum analyzer and the device under test - not
to be left in permanently. At WACOM it was standard practice to use a
10 dB pad between the test equipment and the device under
need to be re-tuned? Depends on who you are, where the
equipment is, what type of duplexers you have and how they
are set up.
I can make a strong case for both yea or nay.
One of the larger players in the choice to to re-adjust is
the Q of the duplexer cavities. Some of the really high-Q
At 6/28/2008 23:30, you wrote:
need to be re-tuned? Depends on who you are, where the
equipment is, what type of duplexers you have and how they
are set up.
I can make a strong case for both yea or nay.
One of the larger players in the choice to to re-adjust is
the Q of the duplexer cavities.
[EMAIL PROTECTED] wrote:
I'm going to disagree here. Gary said he's only moving
12.5 kHz, I've never seen any coaxial resonator in common
use (that means VHFLB cavities being used @ UHF don't count)
that has enough Q that 12.5 kHz is going to make a
significant difference.
You've
At 6/29/2008 21:24, you wrote:
[EMAIL PROTECTED] wrote:
I'm going to disagree here. Gary said he's only moving
12.5 kHz, I've never seen any coaxial resonator in common
use (that means VHFLB cavities being used @ UHF don't count)
that has enough Q that 12.5 kHz is going to make a
This is why it is best to put about 1-2 db 50 ohm pad between the duplexer
and the receiver, to help keep the receive side at 50 ohm.
-- Original Message --
Received: Sun, 29 Jun 2008 10:35:15 PM PDT
From: [EMAIL PROTECTED]
SNIP
Maybe a dB or two at most. I claim that once you take
I have a TX/RX Vari-Notch duplexer. Would the same thing apply to no
re-tuning?
--- In Repeater-Builder@yahoogroups.com, Steve Bosshard (NU5D)
[EMAIL PROTECTED] wrote:
Most band pass / band reject will be plenty wide - I measured over
200
Khz on a Wacom 678 that I use with 3 UHF close
TX/RX will be very close to that as it is the nature of
ganging 2 pass /reject cans on each side of a duplexer... 2 cans on
each side actually widens things out as compared to one, but 2 are
deeper passes and reject notches than one three cans gets
wider/deeper yet... 4 cans
frequency from the
center tune.
The more bandpass cans you use in series, the narrower the bandpass.
73 - Jim W5ZIT
--- On Fri, 6/27/08, Doug Bade [EMAIL PROTECTED] wrote:
From: Doug Bade [EMAIL PROTECTED]
Subject: Re: [Repeater-Builder] Re: Frequency Change do I retune duplexer?
To: Repeater-Builder
It has always been my experience that adding two or more
cans in series always narrows the bandpass, not widen it.
Depending on your perspective you can series stager tuned
over-coupled band pass cavities to make a wider band-pass.
As in the case of a common receive pre-selector window
of the two at the same x frequency
from the center tune.
The more bandpass cans you use in series, the narrower the bandpass.
73 - Jim W5ZIT
--- On Fri, 6/27/08, Doug Bade [EMAIL PROTECTED] wrote:
From: Doug Bade [EMAIL PROTECTED]
Subject: Re: [Repeater-Builder] Re: Frequency Change do I retune
That is true for band pass filters but in the case of a
duplexer the filters are usually notch type (or pass/notch).
In some but not all cases. I have a few shelves full of
band-pass only mode duplexers and they have their very
useful applications.
So the more notch type cans there are
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