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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>>
>>This message was checked by NOD32 antivirus system.
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