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'[EE]: FM Transmitters'
2000\08\22@133614 by Mike

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I'm looking for primmers, faq's or introductions to FM transmitter. I have
seen that taxi driver's emitters have 45W power output and works in FM with
a license given by the mexican agency of communication.

I have been told that the walkie-talkies that work on FM too have a power
between 5 and 15 W. Is this true ?

What I'm looking for is that. Is it possible to do a FM emitter at low cost
with kits or IC's with lower prices than walkie talkies to inteface with a
modem ? or it is cheaper to built in only the modem and use external walkies ?.

The coverage I need its about half of a small city. (My city is small
considered with most of US cities that I consider the most readers are at).

Thanks for all your help, I've been posting and I always get good pointers
to the information need.

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2000\08\22@140318 by Dale Botkin

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On Tue, 22 Aug 2000, Mike wrote:

> I'm looking for primmers, faq's or introductions to FM transmitter. I have
> seen that taxi driver's emitters have 45W power output and works in FM with
> a license given by the mexican agency of communication.
>
> I have been told that the walkie-talkies that work on FM too have a power
> between 5 and 15 W. Is this true ?
>
> What I'm looking for is that. Is it possible to do a FM emitter at low cost
> with kits or IC's with lower prices than walkie talkies to inteface with a
> modem ? or it is cheaper to built in only the modem and use external walkies ?.
>
> The coverage I need its about half of a small city. (My city is small
> considered with most of US cities that I consider the most readers are at).
>
> Thanks for all your help, I've been posting and I always get good pointers
> to the information need.

Ramsey Electronics sells mobile FM transceiver kits running 4-6W output in
the 50, 144, and 220MHz bands.  You didn't mention what frequencies are
available for whatever it is you're doing.  There are manufacturers who
make compact, low-power data radios in the UHF 440-470MHz band also.

Of course, you can buy hand held VHF/UHF transceivers made by Icom,
Kenwood, Yaesu, Alinco, and others that put out anywhere from under 1W to
6W or so.  Most are availabel in several frequency ranges, both amateur
and commercial.  Most are easy to find used for much less than new price.
They are easy to use for data rates up to 1200, maybe 9600 with some work.
I have used my old Yaesu FT-470 dual band FM handheld for 1200BPS packet
radio.  A packet TNC (Kantronics KPC-3) connected via cable to the mic and
speaker jacks, five minutes of adjusting audio levels, and - Presto! -
instant data comunications.

As for coverage area, a lot depends on whether they will be talking to
each other or a base station, and how high the antenna is on the base
station.  That and how tall the buildings are, how much metal, type & size
of antenna used on the mobile end, etc.

Hope this helps a little.

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
               -- Isaac Asimov

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2000\08\22@160951 by pandersn

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Mike.....

More information needed to give you ideas:

1. What is your frequency of operation
2. What power do you wish to transmit with, need
3. What data baud rate are you anticipating

Low power - which may fit your need, lower frequencies such as VHF, and low baud rates for transmission are relatively easy.

4. How to you plan to receive at central site
5. Are you seeking a full-duplex, i.e. two-way, link (much harder and more cost)?

Phil Anderson




On Tuesday, August 22, 2000 1:32 PM, Mike [SMTP:spam_OUTtuxTakeThisOuTspamNETWEBCO.COM] wrote:
{Quote hidden}

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2000\08\22@162901 by Miguel Angel Heredia Moreno

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>Ramsey Electronics sells mobile FM transceiver kits running 4-6W output in
>the 50, 144, and 220MHz bands.  You didn't mention what frequencies are
>available for whatever it is you're doing.  There are manufacturers who
>make compact, low-power data radios in the UHF 440-470MHz band also.

I'll look into Ramsey, thanks, I hope 6 W its enough.
I dont know exactly wich are the frequencyes the goverment gives for
commercial FM private use.
is UHF called "marine band" or something ?

>Of course, you can buy hand held VHF/UHF transceivers made by Icom,
>Kenwood, Yaesu, Alinco, and others that put out anywhere from under 1W to
>6W or so.  Most are availabel in several frequency ranges, both amateur
>and commercial.  Most are easy to find used for much less than new price.
>They are easy to use for data rates up to 1200, maybe 9600 with some work.
>I have used my old Yaesu FT-470 dual band FM handheld for 1200BPS packet
>radio.  A packet TNC (Kantronics KPC-3) connected via cable to the mic and
>speaker jacks, five minutes of adjusting audio levels, and - Presto! -
>instant data comunications.

Are these around 300 dollars ? I have been told thats the average price
around here, I can order from USA.
You mean, are these ready to use with at his ratios with external modems,
right ? or are they with modem included ?
These kantronics equipment seems to be just for cars or indoors use only
(big cases) , am I wrong ? maybe these are used in the other-end.




>As for coverage area, a lot depends on whether they will be talking to
>each other or a base station, and how high the antenna is on the base
>station.  That and how tall the buildings are, how much metal, type & size
>of antenna used on the mobile end, etc.

They will be all talking back and forth to a base station, about the base
antena, it will be as large as it have to be (no limitations on the base
side). The mobile antena has to be something very handy, very mobile.
Mexican cities are not so industrialized as USA ones and there are just a
few tall buildings per city.


>Hope this helps a little.
>
>Dale


Yes, a lot, thank you! :)

BTW : I'm considering to buy the kit showed at
http://www.tapr.org/tapr/html/pice.html for the modem phase, what do you
think ?







At 01:01 p.m. 22/08/00 -0500, you wrote:
{Quote hidden}

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2000\08\22@170257 by Dale Botkin

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On Tue, 22 Aug 2000, Miguel Angel Heredia Moreno wrote:

>  >Ramsey Electronics sells mobile FM transceiver kits running 4-6W output in
>  >the 50, 144, and 220MHz bands.  You didn't mention what frequencies are
>  >available for whatever it is you're doing.  There are manufacturers who
>  >make compact, low-power data radios in the UHF 440-470MHz band also.
>
> I'll look into Ramsey, thanks, I hope 6 W its enough.
> I dont know exactly wich are the frequencyes the goverment gives for
> commercial FM private use.
> is UHF called "marine band" or something ?

No, that's a harmonica...  8-)  Wrong marine band, bad joke, sorry.  I
think marine frequencies are VHF.  In the US, there are commercial bands
all over the spectrum, including 29, 50-something, VHF & UHF.  The UHF
freqs are, I think, up around 450MHz. It all depends on what your
regulatory people will allow.

{Quote hidden}

$300 or so on up, or less for used equipment.  The KPC-3 is about 4" x 4"
x 1/2", very compact and low power.

{Quote hidden}

The mobile antenna can be a 5/8 wave vertical or whatever.  Will these be
vehicle mounted, or hand carried?  If hand carried, you'll need a good
flexible antenna, the longer the better.  The base antenna can be as
elaborate as you want, you'll want a low-angle omnidirectional vertical.
You can buy or build both the base and mobile antennas, there are several
excellent books on the subject available from ARRL, and it's easier than
you would think, especially at VHF frequencies.  I'm fond of J-pole
antennas for V/UHF local work.

> Yes, a lot, thank you! :)
>
> BTW : I'm considering to buy the kit showed at
> http://www.tapr.org/tapr/html/pice.html for the modem phase, what do you
> think ?

Looks good, this looks like pretty much what you need.  Serial data to
AX.25 packets with audio to connect to the radio.  Bascially does the same
job as the KPC-3, but uses a PIC instead of the KPC-3's Z80 (I think).
You could probably change the code to meet your exact requirements if you
needed to.

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
               -- Isaac Asimov

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2000\08\22@170714 by Severson, Rob

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> No, that's a harmonica...  8-)  Wrong marine band, bad joke, sorry.  I

If you're gonna make obscure references, then you should say "an harmonica,
that's right AN HARMONICA" in a bad Boston accent.

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2000\08\22@172344 by pandersn

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Dale....

The KPC-3 Plus uses an HC11, not a Z80 (which would be old TAPR code). It
includes a second serial port for GPS attachment, such as Garmin et al.
Also includes a packet mailbox, not found in old TNC-2 design (now more
than ten years old).

More?

Phil Anderson

On Tuesday, August 22, 2000 3:57 PM, Dale Botkin [SMTP:.....daleKILLspamspam@spam@BOTKIN.ORG]
wrote:
> On Tue, 22 Aug 2000, Miguel Angel Heredia Moreno wrote:
>
> >  >Ramsey Electronics sells mobile FM transceiver kits running 4-6W
output in
> >  >the 50, 144, and 220MHz bands.  You didn't mention what frequencies
are
> >  >available for whatever it is you're doing.  There are manufacturers
who
{Quote hidden}

1W to
> >  >6W or so.  Most are availabel in several frequency ranges, both
amateur
> >  >and commercial.  Most are easy to find used for much less than new
price.
> >  >They are easy to use for data rates up to 1200, maybe 9600 with some
work.
> >  >I have used my old Yaesu FT-470 dual band FM handheld for 1200BPS
packet
> >  >radio.  A packet TNC (Kantronics KPC-3) connected via cable to the
mic and
> >  >speaker jacks, five minutes of adjusting audio levels, and - Presto!
-
> >  >instant data comunications.
> >
> > Are these around 300 dollars ? I have been told thats the average price
> > around here, I can order from USA.
> > You mean, are these ready to use with at his ratios with external
modems,
> > right ? or are they with modem included ?
> > These kantronics equipment seems to be just for cars or indoors use
only
> > (big cases) , am I wrong ? maybe these are used in the other-end.
>
> $300 or so on up, or less for used equipment.  The KPC-3 is about 4" x 4"
> x 1/2", very compact and low power.
>
> > >As for coverage area, a lot depends on whether they will be talking to
> > >each other or a base station, and how high the antenna is on the base
> > >station.  That and how tall the buildings are, how much metal, type &
size
> > >of antenna used on the mobile end, etc.
> >
> > They will be all talking back and forth to a base station, about the
base
> > antena, it will be as large as it have to be (no limitations on the
base
{Quote hidden}

you
> > think ?
>
> Looks good, this looks like pretty much what you need.  Serial data to
> AX.25 packets with audio to connect to the radio.  Bascially does the
same
{Quote hidden}

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2000\08\22@202301 by Dale Botkin

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On Tue, 22 Aug 2000, Phil Anderson wrote:

> The KPC-3 Plus uses an HC11, not a Z80 (which would be old TAPR code). It
> includes a second serial port for GPS attachment, such as Garmin et al.
> Also includes a packet mailbox, not found in old TNC-2 design (now more
> than ten years old).

You're right, of course.  It's not a Z80, but it's been a couple of years
since I was inside mine.  In fact, I don't know that the 3+ was even in
production last time I played with packet.  I used to use an MFJ TNC based
on the old TNC-2, but it did have a PBBS, if I recall correctly.  MFJ
1272, I think it was.

Wish I had the time for radio still...  <<sigh>>.

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
               -- Isaac Asimov

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2000\08\23@070254 by J.Feldhaar

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Hello Mike,

I recommend to make use of the Motorola RF amplifier modules. They come in all
useful frequency ranges (V/UHF), give up to 50+ Watts, and need abt. 100mWatts at
the input, and only 13,6 / 26Volts for operation. Also a heatsink...;-)

This way you can use almost any homemade TX, and save on cost for a complete unit.

Best regards,

Jochen Feldhaar DH6FAZ
Telejet GmbH

"If it starts to work, it's no fun any more..."

Mike schrieb:

{Quote hidden}

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2000\08\23@142246 by Peter L. Peres

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>questions

Since you are asking, I think that you should buy a ready made Tx/Rx
system that is well proven and that even so you will have serious problems
because of the effect of the strong transmitter field on your electronics
(which you apparently do not know how to shield/immunize well). 45Watts
VHF with a so-so assymetrical "balanced" antenna (aka car radio antenna)
is something that will make most 'homemade' electronic projects jump up
and down and every which other way ;) I don't know how much power taxis
use here but I am almost sure it is less than 45 Watts (more like 15-20),
but a DVM of a certain (cheap) make used inside the cab while the driver
keys PTT will misread by up to 300% ;).

Peter

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