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
>
>
>
>
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