I meant to say +_ 2.5khz deviation limits or 12.5 khz channel spacing limits...
Doug
KD8B
At 04:52 PM 4/1/2005, you wrote:
>Dave;
> It sounds like you may be able to use the GTX for a receive end,
>but some suitable continuous duty transmitter will be required. There are
>plenty of paging station type exciters which run 2 watts type power levels
>and can run from now until the end of time if you want.. I just would not
>recommend the GTX for that power level, dead key forever....
> Not that I would take it for book, the ARRL publishes a bandplan
>which is utilized in most places who do not have their own bandplan. In
>general there are provisions for linking freq's in each area as well as
>duplex pairs for duplex needs.
> The deaf rx on the site end should be achievable with mid band
>freq selection on 915-920 ish.... The rx will be 10-15db down from nominal
>at that point, maybe 20db with the normal helical bricks used in most of
>the commercial 900 mobiles. Like about ~-90dbm -> -100dbm area.
> An additional though that these are all narrowband mobiles, so
>that means +-12.5khz deviation limits which tend to sound skinny when
>applied to a wideband system. Sig/noise is out of whack at vol hi, so
>better to couple at speaker level where it is all more or less equal after
>post processing...
> Most 900 mobiles do not come with DTMF pads, so some provision
>will be needed if you choose to control there too...
> If you want wideband audio at 900, I would recommend paging and
>converted 800 gear for the rx side, as they are capable of +_5khz, unlike
>commercial trunking/conventional mobiles.
> 800 Maxtracs can be readily converted to 900 RX if they have a
>talkaround VCO. 16 pin accy jack version is better.. It will need a rom and
>some tweaking. Probably cheaper than the 900 GTX and it will be +_5khz...
>
>Doug
>KD8B
>
>
>
>
>At 12:19 PM 4/1/2005, you wrote:
>
> >At 12:04 PM 4/1/2005, Doug Bade wrote:
> >
> > >Dave;
> > > What kind of erp do you need on the link? Is it close/Line of
> > >Sight? You may be able to operate at exciter levels in which case any of
> > >the mobile options will work great.
> >
> >About 3-5 miles, with yagis. I would figure 1W or less, absolutely,
> >though I am expecting some attempts at tampering so I might want to
> >make the receiver "deaf as a post" and yell at it.
> >
> >
> > >What is your expected TX time on the link?
> >
> >For thermal concerns, I would assume continuous.
> >The control link wouldn't be up unless I needed to change something,
> >and then only for a minute or so, but I would want to use the same
> >radios throughout, in case I need to swap something.
> >
> > >Are you running it simplex or full duplex?
> >
> >Control link will be one-way, intermittent.
> >IRLP will be half-duplex AFAIK. Might go full dup later.
> >
> > >A remote base is easier to set up than a full duplex link and
> > >requires a lot less equipment.
> >
> >My priorities are 1: Control link, 2: IRLP, 3: removing the
> >controller from the repeater site, and operating just with links.
> >
> > >What part of the 900 band you can link in per your coordinator body
> > >would dictate some equipment choices...
> >
> >Ok, I wasn't aware that there was a local plan. I'll check with them.
> >
> > >I guess we need a little more info to answer.. We can go to private email
> > >if it would be easier.... I will be glad to help you figure some options.
> >
> >Might as well let others learn/kibitz :)
> >
> > >A control link could be done easily with GTXor eq., although you
> > >still likely need to change the front end filters...
> >
> >Unless I WANT it "deaf as a post" :)
> >
> >
> > > That application is low duty cycle in the TX dept.... A remote
> > > base config for IRLP is another matter entirely..
> >
> >Well, I do need to get to both.
> >I could do IRLP on 440 as well, I'm less concerned for security there.
> >
> >
> >
> >
> >
> >
> >
> >Yahoo! Groups Links
> >
> >
> >
> >
>
>
>
>
>
>
>
>Yahoo! Groups Links
>
>
>
>
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