Hi Group we did not mean to stir up anything over a simple queston, I
obtained alot of information from it but it seems it also caused a few
problems. We all have our own opinons thats what makes us human.
Randy
----- Original Message -----
From: "Doug Bade" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Sunday, April 23, 2006 3:52 PM
Subject: Re: [Repeater-Builder] Duplexer Wanted
> Mick;
> I would say that was way out of line.
>
> From an engineering standpoint your described system has
> little to do with a mobile environment which is what the original
> poster implied with asking for a mobile duplexer to which a split
> antenna system is impossible to make work on a mobile platform that
> most hams have available.
> While a split site environment with 25 feet of vertical AND
> horizontal spacing may work, it has little to do with the matter at
hand....
>
> I assumed until you last post that you were talking about
> the same thing as the rest of us and I raised my eyebrow as to if it
> was possible in a mobile environment. You have now qualified that
> with a station environment which make it a little more possible.... I
> still doubt if it is desense free however....I also questioned the
> credibility of your comments.... They are not based on engineering
> info readily available to the rest of us so promoting it as gospel is
> called junk science.....
>
> It also has nothing to do with the posters request so I
> think you have done little but cloud the matter with irrelevant data
> and should probably back off...especially on the comments to tell a
> moderator to shut up.... seems like a real bad idea......
>
> Doug
> KD8B
>
>
> At 03:24 PM 4/23/2006, you wrote:
>
> >Just do me and the group a favor and don't waste any more of our
> >time with your ignorance on this subject!
> >Mick - W7CAT
> >
> >Mike Morris wrote:
> >>At 08:33 PM 04/22/06, you wrote:
> >>>Okay, you know it all! I only have been using this for a year and
> >>>a half without any
> >>>problems, and I know others who also use this.
> >>
> >>OK, that proves you have a working system.
> >>
> >>>Of course you can run without the PL, just minimizes a chance of
> >>>getting into the receiver.
> >>
> >>Pray tell, how does it do that? Is PL a receiver preamplifier?
> >>
> >>Remember, PL is modulation, and your receiver has to hear the modulated
> >>signal before PL does any good. Any grunge on the input is
> >>something that your
> >>users signal has to overcome in order for the modulation to be
> >>heard. Yes, you
> >>can configure your receiver so that carrier OR the PL signal opens
> >>the squelch
> >>but that's pretty rare... users tend to not like the extended
> >>squelch tails that setup
> >>causes so most systems are set up so that the receiver unmutes when it
hears
> >>both carrier AND the PL tone.
> >>
> >>If you have any grunge or energy on the receive frequency it is
> >>going to reduce the
> >>effective sensitivity of your receiver, which will make it harder
> >>for your users to get
> >>into the receiver.
> >>
> >>You have measured the effective sensitivity of your system, right?
Because
> >>test bench sensitivity only matters when comparing receiver A vs
> >>receiver B when
> >>ON THE BENCH.
> >>
> >>In the real world your receiver is going to be hit with everything
> >>that your antenna
> >>hears and manages to get through your duplexer and pass cavities -
> >>which is a
> >>very different environment than the single signal generator on the
bench.
> >>
> >>Look at <
> >>http://www.repeater-builder.com/tech-info/effectivesens.html> - a
writeup
> >>from Chris Boone WB5ITT, who happens to be a pretty sharp guy.
> >>
> >>Back to your environment:
> >>
> >>>My transmitter and receiver use the same PL, so pretty much the
> >>>same as carrier squelch.
> >>
> >>How does that work? If you have a active PL decoder then it's not
> >>carrier squelch.
> >>The definition of carrier squelch is that the receiver squelch
> >>opens up (and thereby
> >>keys the transmitter) whenever the receiver quiets enough (from a
> >>carrier signal)
> >>to drop the channel noise below a threshold set by the squelch pot.
> >>
> >>So how does your receiver and transmitter using the same tone make
> >>it pretty much
> >>the same as carrier squelch. Your system either requires the user
> >>to send a tone
> >>or it doesn't.
> >>
> >>By the way, using the same tone just makes your receiver MORE
susceptible
> >>to hearing grunge and intermod, as your own transmitter now has the
correct
> >>tone to open the squelch or to keep it open.
> >>
> >>>Maybe you need to turn off your CD player and open your mind!
> >>
> >>If you will re-read my posting it wasn't my CD player.
> >>
> >>I was trying to make an example of the fact that when you are chasing
> >>desense, grunge or crud you will never hear the interfering signal if
you
> >>are hiding behind a PL decoder.
> >>
> >>Yes, PL is a good thing, but when you are trying to optimize a system
> >>(which in many cases means eliminating interference) you will find it
> >>much harder to identify the interference if there is a PL decoder
preventing
> >>you from hearing it.
> >>
> >>My comment of:
> >> >If you want good performance, you need to leave it in carrier squelch
> >> >mode and FIX IT.
> >>still stands - you can't fix a problem by ignoring it or turning on a PL
> >>decoder so you don't hear it, and let you pretend it's not there.
> >>
> >>Now the circumstances change once you know what the grunge is...
> >>then you enable the PL decoder and get some peace and quiet while...
> >>a) if it's your problem you get the tools, test gear and other
> >>stuff together
> >>for a hill trip, or
> >>b) you figure out how to tell the guys in the next rack over that they
need
> >>to install a circulator.
> >>
> >>>Mick - W7CAT
> >>
> >>Mike
> >>
> >>>Mike Morris wrote:
> >>>
> >>>>
> >>>>
> >>>>At 09:54 AM 04/22/06, you wrote:
> >>>>
> >>>>>
> >>>>>Hello Randy,
> >>>>>
> >>>>>With only 25 watts, the other option is to use two antennas with
> >>>>>some separation. And it is also helpful to add a filter to the
> >>>>>transmit line and another to the receiver. At least add one to the
> >>>>>transmit side. Adding a filter to the transmit side would help
> >>>>>eliminate the high power interference, and no loss for the receiver.
> >>>>>And of course PL on your receiver would help too.
> >>>>>
> >>>>
> >>>>NO IT WON'T.
> >>>>
> >>>>PL only hides a problem. It's like a lady down the block that had
> >>>>a
> >>>>squealing left front brake shoe (it was dragging) so she kept her
> >>>>window closed and turned up the volume on the CD player.
> >>>>
> >>>>If you want good performance, you need to leave it in carrier squelch
> >>>>mode and FIX IT.
> >>>>
> >>>>Mike WA6ILQ
> >>>>
> >>
> >>
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> >
> >
> >
> >
> >
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