Re: [Repeater-Builder] Re: Band Pass Duplexer Tuning

[Nate Duehr]

On 2/22/07, fxbuilder <[EMAIL PROTECTED]> wrote:
> I didn't have a load on the 3rd port when I tuned it.  I only have 1
> dummy load.  I can add an antenna to the 3rd port though I know that
> would less than ideal but better than nothing I suppose.  I have found
> some schematics for the pads and will be working on that this weekend.
> On a side note anyone know what the sensitivity should be on my uhf
> Mitrek when it is tuned correctly?  A low level but noisy signal seems
> to break squelch at .5mv (assuming I'm reading my old tube Navy
> generator correctly) and full quiet seems to be around 5mv.  Is this
> close to what it should be? It just doesn't seem to have "great ears".
>  Could be the nearby hills are just heavily blocking the antenna.
> Finding a good location that doesn't cost my first born is tough in
> this area.
> Craig

I'm not a "Motorola guy", so I have no idea what the factory spec of
the Mitrek receiver sensitivity is... but...

For repeater service using older radios, it's pretty common to need a
pre-amp to get maximum receiver performance.  But your original posts
were that you were tuning a small flat-pack style duplexer for this
project -- it may simply not have enough rejection.

Are you doing the sensitivity tests with the transmitter on or off?
You could be fighting good old fashioned desense.

A couple of the articles here in the RB site might be useful:

http://www.repeater-builder.com/antenna/deaf.html

(The link to Remec/Wacom in that article goes to someone else now...
since Wacom was acquired... and the link goes to a redirect that leads
to a company in Lynchburg who does other types of filters, looks
like...)

http://www.repeater-builder.com/rbtip/preamps.html

( I disagree with a statement in this article... "If you have the
ability you can probably construct a preamp that will more closely
suit your needs than can be found commercially."  -- Chip Angle at
AngleLinear gets rave reviews from many repeater owner/operators, and
a lot of us use Advanced Receiver Research's pre-amps without undue
headaches... which are both commercial products.  They both suit a lot
of people's needs!  GRIN... )

I'm also not quite sure about this statement talking about using the
pre-amp after the duplexer and before the receiver... :

"Again, since we are not making up for a great deal of loss, we do not
need a great deal of gain.  This example works great in UHF systems
but likely shouldn't be tried on 2 meters."

Off the top of my head, I can think of more than five VHF systems here
locally that do this with fine results...?  Different clubs, different
techs.  Some have bandpass filtering, some don't...   Kevin might
explain what he was thinking there...?

But anyway... check for desense before anything ... if you have that
going on, making the receiver hear better will only make it worse.
(GRIN)

Nate WY0X

[Repeater-Builder] Re: Band Pass Duplexer Tuning

[fxbuilder]

I didn't have a load on the 3rd port when I tuned it.  I only have 1
dummy load.  I can add an antenna to the 3rd port though I know that
would less than ideal but better than nothing I suppose.  I have found
some schematics for the pads and will be working on that this weekend.
On a side note anyone know what the sensitivity should be on my uhf
Mitrek when it is tuned correctly?  A low level but noisy signal seems
to break squelch at .5mv (assuming I'm reading my old tube Navy
generator correctly) and full quiet seems to be around 5mv.  Is this
close to what it should be? It just doesn't seem to have "great ears".
 Could be the nearby hills are just heavily blocking the antenna.
Finding a good location that doesn't cost my first born is tough in
this area.
Craig


--- In Repeater-Builder@yahoogroups.com, "Gary Schafer"
<[EMAIL PROTECTED]> wrote:
>
> 
> 
> Like Ken said; all 3 ports need to be terminated in 50 ohms when
tuning. A
> signal generator is usually fairly close to 50 ohms, a receiver may
or may
> not be, usually not. The unused port at the time needs a 50 ohm load. 
> The best way is to use a 6 db pad on gen and rec sides while tuning.
> 
> But what may be the worst problem is you may be trying to use it too far
> from the design frequency. You have no way to tune the loops on
those units.
> Also be sure you haven't reversed the tx and rx frequencies as the
loops are
> tuned internally to pass a frequency only on one side of the notch.
> 
> 73
> Gary  K4FMX
> 
> > -Original Message-
> > From: Repeater-Builder@yahoogroups.com [mailto:Repeater-
> > [EMAIL PROTECTED] On Behalf Of fxbuilder
> > Sent: Tuesday, February 20, 2007 9:49 AM
> > To: Repeater-Builder@yahoogroups.com
> > Subject: [Repeater-Builder] Re: Band Pass Duplexer Tuning
> > 
> > Ok... So I've tuned this duplexer as a notch device.  Put a 2 watt
> > handheld into a dummy load and watt meter (not in that order mind you)
> > and it seems to reject the corresponding frequencies.  My question now
> > is... Why did my swr jump from 1:1.3 to 1:3.  Do I need to re-tweek
> > it?  Also I'm noticing a huge power loss when measured before and
> > after the duplexer. Talking 30 watts down to below 10 watts. Any
> > suggestions. Perhaps it is time to check the cables etc?  Thanks for
> > all the help in the past.
> > Craig
> > 
> > 
> > 
> > 
> > 
> > --- In Repeater-Builder@yahoogroups.com, "Gary Schafer"
> >  wrote:
> > >
> > > Lots of the small mobile duplexers (notch type) have fixed
> > capacitors inside
> > > and you can only adjust the cavity tuning, which tunes the notch.
> > >
> > > This type duplexer is limited in how far from the design frequency
> > you can
> > > tune it as the capacitors are fixed. The cavities will tune but
the loss
> > > goes.
> > >
> > > 73
> > > Gary  K4FMX
> > >
> > > > -Original Message-
> > > > From: Repeater-Builder@yahoogroups.com [mailto:Repeater-
> > > > [EMAIL PROTECTED] On Behalf Of fxbuilder
> > > > Sent: Friday, February 16, 2007 5:09 PM
> > > > To: Repeater-Builder@yahoogroups.com
> > > > Subject: [Repeater-Builder] Re: Band Pass Duplexer Tuning
> > > >
> > > > I emailed the place I bought it from and that is what I was told.
> > > > Band Pass. No caps on it for notch tuning as on celwave.  Am I
missing
> > > > something here?
> > > > Craig
> > > >
> > > >
> > > >
> > > >
> > > > --- In Repeater-Builder@yahoogroups.com, Ken Arck  wrote:
> > > > >
> > > > > At 01:53 PM 2/16/2007, you wrote:
> > > > >
> > > > > >There is a great article on this site about tuning a notch
> > duplexer by
> > > > > >Kevin. Can similar methods be used for tuning a mobile 6
can band
> > > > > >pass duplexer? Is there an article that I missed that explains
> > it as
> > > > > >easily? I need to re-tune and could use the help. I think I
> > know how
> > > > > >but thought I'd check.
> > > > >
> > > > > <Is there such a thing???
> > > > >
> > > > > Ken
> > > > >
> > > >
> >
--
> > > > 
> > > > > President and CTO - Arcom Communications
> > > > > Makers of the world famous RC210 Repeater Controller and
> > accessories.
> > > > > http://www.arcomcontrollers.com/
> > > > > Authorized Dealers for Kenwood and Telewave and
> > > > > we offer complete repeater packages!
> > > > > AH6LE/R - IRLP Node 3000
> > > > > http://www.irlp.net
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > Yahoo! Groups Links
> > > >
> > > >
> > > >
> > >
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > Yahoo! Groups Links
> > 
> > 
> >
>

RE: [Repeater-Builder] Re: Band Pass Duplexer Tuning

[Gary Schafer]

Like Ken said; all 3 ports need to be terminated in 50 ohms when tuning. A
signal generator is usually fairly close to 50 ohms, a receiver may or may
not be, usually not. The unused port at the time needs a 50 ohm load. 
The best way is to use a 6 db pad on gen and rec sides while tuning.

But what may be the worst problem is you may be trying to use it too far
from the design frequency. You have no way to tune the loops on those units.
Also be sure you haven't reversed the tx and rx frequencies as the loops are
tuned internally to pass a frequency only on one side of the notch.

73
Gary  K4FMX

> -Original Message-
> From: Repeater-Builder@yahoogroups.com [mailto:Repeater-
> [EMAIL PROTECTED] On Behalf Of fxbuilder
> Sent: Tuesday, February 20, 2007 9:49 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Re: Band Pass Duplexer Tuning
> 
> Ok... So I've tuned this duplexer as a notch device.  Put a 2 watt
> handheld into a dummy load and watt meter (not in that order mind you)
> and it seems to reject the corresponding frequencies.  My question now
> is... Why did my swr jump from 1:1.3 to 1:3.  Do I need to re-tweek
> it?  Also I'm noticing a huge power loss when measured before and
> after the duplexer. Talking 30 watts down to below 10 watts. Any
> suggestions. Perhaps it is time to check the cables etc?  Thanks for
> all the help in the past.
> Craig
> 
> 
> 
> 
> 
> --- In Repeater-Builder@yahoogroups.com, "Gary Schafer"
> <[EMAIL PROTECTED]> wrote:
> >
> > Lots of the small mobile duplexers (notch type) have fixed
> capacitors inside
> > and you can only adjust the cavity tuning, which tunes the notch.
> >
> > This type duplexer is limited in how far from the design frequency
> you can
> > tune it as the capacitors are fixed. The cavities will tune but the loss
> > goes.
> >
> > 73
> > Gary  K4FMX
> >
> > > -Original Message-
> > > From: Repeater-Builder@yahoogroups.com [mailto:Repeater-
> > > [EMAIL PROTECTED] On Behalf Of fxbuilder
> > > Sent: Friday, February 16, 2007 5:09 PM
> > > To: Repeater-Builder@yahoogroups.com
> > > Subject: [Repeater-Builder] Re: Band Pass Duplexer Tuning
> > >
> > > I emailed the place I bought it from and that is what I was told.
> > > Band Pass. No caps on it for notch tuning as on celwave.  Am I missing
> > > something here?
> > > Craig
> > >
> > >
> > >
> > >
> > > --- In Repeater-Builder@yahoogroups.com, Ken Arck  wrote:
> > > >
> > > > At 01:53 PM 2/16/2007, you wrote:
> > > >
> > > > >There is a great article on this site about tuning a notch
> duplexer by
> > > > >Kevin. Can similar methods be used for tuning a mobile 6 can band
> > > > >pass duplexer? Is there an article that I missed that explains
> it as
> > > > >easily? I need to re-tune and could use the help. I think I
> know how
> > > > >but thought I'd check.
> > > >
> > > > <Is there such a thing???
> > > >
> > > > Ken
> > > >
> > >
> --
> > > 
> > > > President and CTO - Arcom Communications
> > > > Makers of the world famous RC210 Repeater Controller and
> accessories.
> > > > http://www.arcomcontrollers.com/
> > > > Authorized Dealers for Kenwood and Telewave and
> > > > we offer complete repeater packages!
> > > > AH6LE/R - IRLP Node 3000
> > > > http://www.irlp.net
> > > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> >
> 
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 

Re: [Repeater-Builder] Re: Band Pass Duplexer Tuning

[Ken Arck]

At 06:49 AM 2/20/2007, you wrote:

>Ok... So I've tuned this duplexer as a notch device. Put a 2 watt
>handheld into a dummy load and watt meter (not in that order mind you)
>and it seems to reject the corresponding frequencies. My question now
>is... Why did my swr jump from 1:1.3 to 1:3. Do I need to re-tweek
>it? Also I'm noticing a huge power loss when measured before and
>after the duplexer. Talking 30 watts down to below 10 watts. Any
>suggestions. Perhaps it is time to check the cables etc? Thanks for
>all the help in the past.

<---What did you do with the 3rd port during your tuning procedure? 
When you tune a duplexer, did you MUST present a 50 ohm load on ALL 3 
ports. This typically means using 3 (or 6) dB pads on all ports during tuning.

Since yours is showing excessive loss and bad VSWR, my bet is you 
left the 3rd port unterminated and didn't use pads on at least the 
Port to which the radio was connected.

Ken
--
President and CTO - Arcom Communications
Makers of the world famous RC210 Repeater Controller and accessories.
http://www.arcomcontrollers.com/
Authorized Dealers for Kenwood and Telewave and
we offer complete repeater packages!
AH6LE/R - IRLP Node 3000
http://www.irlp.net

[Repeater-Builder] Re: Band Pass Duplexer Tuning

[fxbuilder]

Ok... So I've tuned this duplexer as a notch device.  Put a 2 watt
handheld into a dummy load and watt meter (not in that order mind you)
and it seems to reject the corresponding frequencies.  My question now
is... Why did my swr jump from 1:1.3 to 1:3.  Do I need to re-tweek
it?  Also I'm noticing a huge power loss when measured before and
after the duplexer. Talking 30 watts down to below 10 watts. Any
suggestions. Perhaps it is time to check the cables etc?  Thanks for
all the help in the past.
Craig





--- In Repeater-Builder@yahoogroups.com, "Gary Schafer"
<[EMAIL PROTECTED]> wrote:
>
> Lots of the small mobile duplexers (notch type) have fixed
capacitors inside
> and you can only adjust the cavity tuning, which tunes the notch.
> 
> This type duplexer is limited in how far from the design frequency
you can
> tune it as the capacitors are fixed. The cavities will tune but the loss
> goes.
> 
> 73
> Gary  K4FMX
> 
> > -Original Message-
> > From: Repeater-Builder@yahoogroups.com [mailto:Repeater-
> > [EMAIL PROTECTED] On Behalf Of fxbuilder
> > Sent: Friday, February 16, 2007 5:09 PM
> > To: Repeater-Builder@yahoogroups.com
> > Subject: [Repeater-Builder] Re: Band Pass Duplexer Tuning
> > 
> > I emailed the place I bought it from and that is what I was told.
> > Band Pass. No caps on it for notch tuning as on celwave.  Am I missing
> > something here?
> > Craig
> > 
> > 
> > 
> > 
> > --- In Repeater-Builder@yahoogroups.com, Ken Arck  wrote:
> > >
> > > At 01:53 PM 2/16/2007, you wrote:
> > >
> > > >There is a great article on this site about tuning a notch
duplexer by
> > > >Kevin. Can similar methods be used for tuning a mobile 6 can band
> > > >pass duplexer? Is there an article that I missed that explains
it as
> > > >easily? I need to re-tune and could use the help. I think I
know how
> > > >but thought I'd check.
> > >
> > > <Is there such a thing???
> > >
> > > Ken
> > >
> >
--
> > 
> > > President and CTO - Arcom Communications
> > > Makers of the world famous RC210 Repeater Controller and
accessories.
> > > http://www.arcomcontrollers.com/
> > > Authorized Dealers for Kenwood and Telewave and
> > > we offer complete repeater packages!
> > > AH6LE/R - IRLP Node 3000
> > > http://www.irlp.net
> > >
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > Yahoo! Groups Links
> > 
> > 
> >
>

RE: [Repeater-Builder] Re: Band Pass Duplexer Tuning

[Gary Schafer]

Lots of the small mobile duplexers (notch type) have fixed capacitors inside
and you can only adjust the cavity tuning, which tunes the notch.

This type duplexer is limited in how far from the design frequency you can
tune it as the capacitors are fixed. The cavities will tune but the loss
goes.

73
Gary  K4FMX

> -Original Message-
> From: Repeater-Builder@yahoogroups.com [mailto:Repeater-
> [EMAIL PROTECTED] On Behalf Of fxbuilder
> Sent: Friday, February 16, 2007 5:09 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Re: Band Pass Duplexer Tuning
> 
> I emailed the place I bought it from and that is what I was told.
> Band Pass. No caps on it for notch tuning as on celwave.  Am I missing
> something here?
> Craig
> 
> 
> 
> 
> --- In Repeater-Builder@yahoogroups.com, Ken Arck <[EMAIL PROTECTED]> wrote:
> >
> > At 01:53 PM 2/16/2007, you wrote:
> >
> > >There is a great article on this site about tuning a notch duplexer by
> > >Kevin. Can similar methods be used for tuning a mobile 6 can band
> > >pass duplexer? Is there an article that I missed that explains it as
> > >easily? I need to re-tune and could use the help. I think I know how
> > >but thought I'd check.
> >
> > <Is there such a thing???
> >
> > Ken
> >
> --
> 
> > President and CTO - Arcom Communications
> > Makers of the world famous RC210 Repeater Controller and accessories.
> > http://www.arcomcontrollers.com/
> > Authorized Dealers for Kenwood and Telewave and
> > we offer complete repeater packages!
> > AH6LE/R - IRLP Node 3000
> > http://www.irlp.net
> >
> 
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 

Re: [Repeater-Builder] Re: Band Pass Duplexer Tuning

[Ken Arck]

At 02:09 PM 2/16/2007, you wrote:

>I emailed the place I bought it from and that is what I was told.
>Band Pass. No caps on it for notch tuning as on celwave. Am I missing
>something here?

<---As Skipp pointed out, most the so-called "mobile duplexers" are 
notch only. You have a make and model #?

Ken
--
President and CTO - Arcom Communications
Makers of the world famous RC210 Repeater Controller and accessories.
http://www.arcomcontrollers.com/
Authorized Dealers for Kenwood and Telewave and
we offer complete repeater packages!
AH6LE/R - IRLP Node 3000
http://www.irlp.net

Re: [Repeater-Builder] Re: Band Pass Duplexer Tuning

[Ken Arck]

At 02:14 PM 2/16/2007, you wrote:


Yes, this is a flat pack. The place I bought it from told me it was a
band pass. Thanks Scott, I'll try your method.
Craig


Repeater-Builder@yahoogroups.com, 
"Scott" <[EMAIL PROTECTED]> wrote:

>
> If you are talking about a "flat pak" duplexer, they are easy.
>
> Hook a receiver (or scope) to the "high" side and set the monitor
> frequency to the "low" frequency. Inject the "high" freqency into the
> antenna port. Tune for the deepest null.
>
> Then hook the monitor to the "low" side set for the "high" frequency
> and inject the high frequency, and again, tune for the deepest null.
> You will have to keep readjusting your signal generator. It helps to
> inject the 1000Hz tone if you are doing it "by ear".
>
> Scott NA4IT
>
> --- In 
Repeater-Builder@yahoogroups.com, 
"fxbuilder" 

> wrote:
> >
> > There is a great article on this site about tuning a notch duplexer by
> > Kevin. Can similar methods be used for tuning a mobile 6 can band
> > pass duplexer? Is there an article that I missed that explains it as
> > easily? I need to re-tune and could use the help. I think I know how
> > but thought I'd check.
> > Craig
> >
>




--
President and CTO - Arcom Communications
Makers of the world famous RC210 Repeater Controller and accessories.
http://www.arcomcontrollers.com/
Authorized Dealers for Kenwood and Telewave and
we offer complete repeater packages!
AH6LE/R - IRLP Node 3000
http://www.irlp.net

[Repeater-Builder] Re: Band Pass Duplexer Tuning

[fxbuilder]

Yes, this is a flat pack.  The place I bought it from told me it was a
band pass.  Thanks Scott, I'll try your method.
Craig




--- In Repeater-Builder@yahoogroups.com, "Scott" <[EMAIL PROTECTED]> wrote:
>
> If you are talking about a "flat pak" duplexer, they are easy. 
> 
> Hook a receiver (or scope) to the "high" side and set the monitor
> frequency to the "low" frequency. Inject the "high" freqency into the
> antenna port. Tune for the deepest null. 
> 
> Then hook the monitor to the "low" side set for the "high" frequency
> and inject the high frequency, and again, tune for the deepest null.
> You will have to keep readjusting your signal generator. It helps to
> inject the 1000Hz tone if you are doing it "by ear".
> 
> Scott NA4IT
> 
> --- In Repeater-Builder@yahoogroups.com, "fxbuilder" 
> wrote:
> >
> > There is a great article on this site about tuning a notch duplexer by
> > Kevin.  Can similar methods be used for tuning a mobile 6 can band
> > pass duplexer?  Is there an article that I missed that explains it as
> > easily?  I need to re-tune and could use the help.  I think I know how
> > but thought I'd check.
> > Craig
> >
>

[Repeater-Builder] Re: Band Pass Duplexer Tuning

[Scott]

If you are talking about a "flat pak" duplexer, they are easy. 

Hook a receiver (or scope) to the "high" side and set the monitor
frequency to the "low" frequency. Inject the "high" freqency into the
antenna port. Tune for the deepest null. 

Then hook the monitor to the "low" side set for the "high" frequency
and inject the high frequency, and again, tune for the deepest null.
You will have to keep readjusting your signal generator. It helps to
inject the 1000Hz tone if you are doing it "by ear".

Scott NA4IT

--- In Repeater-Builder@yahoogroups.com, "fxbuilder" <[EMAIL PROTECTED]>
wrote:
>
> There is a great article on this site about tuning a notch duplexer by
> Kevin.  Can similar methods be used for tuning a mobile 6 can band
> pass duplexer?  Is there an article that I missed that explains it as
> easily?  I need to re-tune and could use the help.  I think I know how
> but thought I'd check.
> Craig
>

[Repeater-Builder] Re: Band Pass Duplexer Tuning

[fxbuilder]

I emailed the place I bought it from and that is what I was told. 
Band Pass. No caps on it for notch tuning as on celwave.  Am I missing
something here?
Craig




--- In Repeater-Builder@yahoogroups.com, Ken Arck <[EMAIL PROTECTED]> wrote:
>
> At 01:53 PM 2/16/2007, you wrote:
> 
> >There is a great article on this site about tuning a notch duplexer by
> >Kevin. Can similar methods be used for tuning a mobile 6 can band
> >pass duplexer? Is there an article that I missed that explains it as
> >easily? I need to re-tune and could use the help. I think I know how
> >but thought I'd check.
> 
>  
> Ken
>
--
> President and CTO - Arcom Communications
> Makers of the world famous RC210 Repeater Controller and accessories.
> http://www.arcomcontrollers.com/
> Authorized Dealers for Kenwood and Telewave and
> we offer complete repeater packages!
> AH6LE/R - IRLP Node 3000
> http://www.irlp.net
>

[Repeater-Builder] Re: Band Pass Duplexer Tuning

[skipp025]

Yes there is... but it's really big even for UHF. Phelps Dodge Made 
one and I've seen a number of odd ball units around with Harris labels 
on them. Normally the "smaller" mobile duplexer are notch-pass (aka
notch-notch).  But everything is possible... and probably tried at 
least once. 

cheers, 
skipp 


>  > There is a great article on this site about tuning a 
> > notch duplexer by Kevin. Can similar methods be used 
> > for tuning a mobile 6 can band pass duplexer? Is there 
> > an article that I missed that explains it as easily? I 
> > need to re-tune and could use the help. I think I know 
> > how but thought I'd check.