On 9/21/2018 12:00 AM, 'Jeff DePolo' jd0@... [Repeater-Builder] wrote:

OK that's too low for my needs. When you run 2 TXs through
it the power rating needs to be higher than the sum of the
input powers due to the higher voltage peaks you get as
opposed to a single TX of the same (summed) power.

Bob NO6B

Bob,

RFS/PD used to make a compact notch-only UHF duplexer; I can't think of the
model number off the top of my head. They were constructed similiar to the
ubiqutous PD/RFS 633 series duplexers, but the resonators were about 50%
larger in height and width, or maybe about 2x the cross-section area. They
were rated for 100 watts. I think I have a few (somewhere). I can look for
one and see how it behaves splitting 440 Tx/Rx vs 420 if it will do you any
good.

--- Jeff WN3A

I have two such units originally built/tuned for the UHF ham band. If you are interested, Bob, drop me a direct line.

Kevin

OK that's too low for my needs. When you run 2 TXs through
it the power rating needs to be higher than the sum of the
input powers due to the higher voltage peaks you get as
opposed to a single TX of the same (summed) power.

Bob NO6B

Bob,

RFS/PD used to make a compact notch-only UHF duplexer; I can't think of the
model number off the top of my head. They were constructed similiar to the
ubiqutous PD/RFS 633 series duplexers, but the resonators were about 50%
larger in height and width, or maybe about 2x the cross-section area. They
were rated for 100 watts. I think I have a few (somewhere). I can look for
one and see how it behaves splitting 440 Tx/Rx vs 420 if it will do you any
good.

--- Jeff WN3A

On 9/20/2018 9:41 PM, no6b@... [Repeater-Builder] wrote:

At 9/20/2018 01:14 PM, you wrote:

Bob,

If I recall its rated at 40watts.

OK that's too low for my needs. When you run 2 TXs through it the power rating needs to be higher than the sum of the input powers due to the higher voltage peaks you get as opposed to a single TX of the same (summed) power.
Bob NO6B

Yeah, nearly all flatpack/mobile duplexers I've seen are rated at 50 W or less...

At 9/20/2018 01:14 PM, you wrote:

Bob,

If I recall its rated at 40watts.

OK that's too low for my needs.? When you run 2 TXs through it the power rating needs to be higher than the sum of the input powers due to the higher voltage peaks you get as opposed to a single TX of the same (summed) power.

Bob NO6B

Ken, Or anyone that can help.

Bob,

If I recall its rated at 40watts.

-J

If you discuss the bare notch filter or cavity response without any
other tricks or compensation, by nature of electronics theory, it
will probably be non-symmetrical in most cases where the physical
hardware or construction actually adds some additional reactance
on one side of the notch.

If you look at it in the simplest sense, a 1/4 wave notch cavity is just an
open stub 1/4" long that is loosely coupled to the thru-line. In the same
manner as if you teed in the stub directly (rather than loosely coupling
it), it's going yield a shunt reactance across the line. In other words,
there's no such thing as a notch cavity that does NOT have some effect on
the thru-line at frequencies other than only at the notch frequency.

The tighter you couple the resonator to the line, the more pronounced the
deleterious off-channel effects will be. That should be obvious. Of
course, the tighter you couple, the more notch depth you get, so there's an
inherent tradeoff when designing/adjusting the coupling.

You can often correct for the adverse effects in the passband by adding a
reactance to compensate. You can also stand the resonator off the thru-line
with a length of cable to change the effect and/or to optimize the response
(either with or without stubs or other compensation) at the pass frequency.

Scroll down and select the:
Optimizing Notch Filter Matching DRAFT.pdf

Yahoo doesn't seem to be working at the moment (browser hangs and I get an
"Activity Timeout" page from Yahoo) when I click that link, but I think that
file you're referring to is something that I wrote while back to demonstrate
some of the effects we're talking about.

--- Jeff WN3A

At 9/19/2018 09:55 AM, you wrote:

For reference, here is the frequency response plot for both sides. At a 10Mhz split, the insertion loss is great, around 1.2dB. But look at this with 5Mhz split, pretty bad.

Actually it looks more like a 20 MHz split duplexer.

I might be interested in it if you want to get rid of it, as they make for a convenient way to triplex a 420 link TX with a 440 repeater.? What is its power rating?

Bob NO6B

Thank you I have contacted Matt

This was used for a period of time, so maybe it either got
damaged, or as someone else suggested, it was a 10Mhz split
model but was sold as a 5Mhz split with the idea that whoever

A 6-resonator notch duplexer like that should yield WAY more than 68 dB of
notch depth. Something is definitely wrong with it aside from the poor
passband performance.

--- Jeff WN3A

On 9/19/2018 9:02 PM, skipp025@... [Repeater-Builder] wrote:

If you discuss the bare notch filter or cavity response without any
other tricks or compensation, by nature of electronics theory, it
will probably be non-symmetrical in most cases where the physical
hardware or construction actually adds some additional reactance
on one side of the notch.

This is plainly seen in many band-pass cavities, and BPBR duplexer configurations because of the commonality of inductive coupling loops.? Many of these filter systems use a closed loop (inductive) coupling method.? This causes a defined difference in symmetry between the response of a cavity tuned to high-pass as compared to one tuned to low-pass.? The same happens with a band-pass cavity with two identical coupling loops.

In the band-pass cavity, if you trade one of the inductive coupling loops for a capacitive probe, a good bit of the asymmetry will be 'compensated' out.? In the case of a duplexer, some companies like TX-RX have added inductance on one 'side' which is placed somewhat out of the magnetic plane to minimize coupling.? This added inductance serves to balance the coupling method and attempts to make the duplexers response symmetrical.

Kevin

开云体育

I have modified a couple of "LM" (Linear Modulation) brand ACSB Repeater PAs for FM Use.? It is quite easy.? There is a switching transistor that gets removed and replaced with a jumper - that's it.? If I recall they are about 500mw in for 100W Out.? I did a bench test and made a chart that I put on the PA with the various input/output levels.? The other benefit is if you get the entire repeater you can remove or modify the Exciter and Receiver modules, replacing them with an FM Receiver and Exciter and have everything in the same chassis.? The power supply uses XLR connectors for 13.8VDC supply to the various modules - so just plug and play any 13.8V receiver/exciter.? I have had one of these on the air for close to 10 years with a pair of Alinco DR-235s and an attenuator on the transmit radio.? It works very well - so well that I found a spare and have kept it around.

Many notch filters are not symmetrical.

If you discuss the bare notch filter or cavity response without any
other tricks or compensation, by nature of electronics theory, it
will probably be non-symmetrical in most cases where the physical
hardware or construction actually adds some additional reactance
on one side of the notch.

It can be compensated for in many cases, but the basic animal
(notch cavity) will normally not have a truly symmetrical response.

If you look at some of them, one side will have just a T connector
between the cavities and the other side will have what looks about
like a 1/4 wave of coax(hardline) comming from the middle of the T
to the cavity.

To learn a little more about notch filter placement and operation...
based on a real world example. The below article in this Groups
Files Section can be very informative.



Scroll down and select the:

Optimizing Notch Filter Matching DRAFT.pdf

Enjoy...

cheers,

Hand me down shoes
(Burton Cummings)

Ed,if the software doesn't accept the freq,an IC can't help.
The IC on ebay is for alignment in the hm bands.

The Yahoo group/email messages out of sequence is really messing with me here...

#motarolla_docter
Yep, that is how I tuned it. But I tried both ways just to see. But yes, the Low is indeed Low pass and High is High pass as noted by the sticker.


So I decided to take it apart to see if there was anything obvious, like burn marks, etc. Other than a bad solder joint for one of the hardline feeds (the shield), it looks ok. Attached are the pictures for those that have never seen the inside of these...

-J