From: "Netgeek" on Sun, Mar 13 2005 4:42 pm

I'd like to build some homebrew VHF-AM receivers - specifically a
receiver
for
the VHF 108-118 Mhz band. I've found lots of great ideas and
reference
designs
out there but they're all constructed of parts made from "unobtainium"
(e.g.
old
MC13135/6, MC1350, etc., etc.)...

Can anyone on this group point me to some designs/ideas for how to
construct
something made from "actually available" components???

Firstly, 108 to 118 MHz is the international civil
aviation radionavigation band. It's not all that
interesting to listen to unless a local tower is
also repeating voice comms over a VOR or Localizer
radionav transmitter nearby on the ground. The
civil aviation voice band is 118 to 137 MHz.

Secondly, the MC1350 gain block is available from
Jameco (it is still made after buying all the masking
and stuff from Motorola). You can get MC1349s, a
slightly higher gain version from Dieter Gentzow at
Kitsandparts.com; I got 18 of them just before
Christmas along with some other good parts. Good
service from Kitsandparts, great source of toroid
cores.

There's still lots of legacy ICs available out there
but you may have to search for sources.

If you are trying to build something at VHF, you
will need some reasonably accurate signal sources
to check out the receiver. That's not a trivial
task unless all you want is to carbon-copy some
regen or super-regen tuned-by-a-single-variable
sort of receiver.

Jameco sells the MC145151 PLL IC (On Semiconductor
the Motorola spin-off still makes them) which, with
a prescaler, can make a good, stable LO that is
channelized at 50 KHz increments for precise tuning.
MC145151 is parallel-load for division, no extra
IC needed to get the right division ratio as in
some serial-input PLL or DDS chips.

Lots of inexpensive "all-band" radios off the shelf
include the aviation band, those in addition to all
the available VHF scanner receivers. Those all work
better and more reliably than simple regens and
super-regens in my observation.

Len,

Thanks for the input and observations! Comments follow:

wrote in message
oups.com...
Firstly, 108 to 118 MHz is the international civil
aviation radionavigation band. It's not all that
interesting to listen to unless a local tower is
also repeating voice comms over a VOR or Localizer
radionav transmitter nearby on the ground. The
civil aviation voice band is 118 to 137 MHz.

Agreed - not that interesting to listen to, but the NAV
channels are exactly what I'm interested in - (both VOR
and LOC). The "experiment" I have in mind is a processor
controlled scanner of sorts that tracks multiple VORs
and performs as a backup to GPS. Hence the need for
fast/agile tuning (either PLL or DDS). As you may have
gathered - I'm not an "RF guy" by any stretch - but I'm
attempting to learn (out of sheer necessity 8-).....

Secondly, the MC1350 gain block is available from
Jameco (it is still made after buying all the masking
and stuff from Motorola). You can get MC1349s, a
slightly higher gain version from Dieter Gentzow at
Kitsandparts.com

I'm not locked in to the MC1350 - it just happens to be
what's used in the "ultra-cheap" kit I ordered. As it turns
out, there's a company (Lansdale.com) that seems to be
forming a business model around buying "obsolete" IP
from Motorola et.al. and keeping the parts available.
Interesting idea. As it happens, NTE has a drop-in
replacement part for the MC1350 in their "NTE746" -
available from Mouser. May be of interest to some on
this group???

If you are trying to build something at VHF, you
will need some reasonably accurate signal sources
to check out the receiver. That's not a trivial
task unless all you want is to carbon-copy some
regen or super-regen tuned-by-a-single-variable
sort of receiver.

Well, even though (as I said) I'm not an RF-type I do
have quite a bit of test equipment laying around that I've
collected over the years. Among that stuff is an HP8654A
good to about 520 MHz that I've never used (and for the
life of me can't figure why I bought 8-)........

Jameco sells the MC145151 PLL IC (On Semiconductor
the Motorola spin-off still makes them) which, with
a prescaler, can make a good, stable LO that is
channelized at 50 KHz increments for precise tuning.
MC145151 is parallel-load for division, no extra
IC needed to get the right division ratio as in
some serial-input PLL or DDS chips.

Thanks for the tip - I'm concerned about how long
such a thing might be available though. For now the
safest bet seems to be the National LMX series (or
the Analog Devices equivalents) - and adding a
processor for control is not a problem.

Thanks again for your input - it is appreciated!!!
Regards,
Bill

Netgeek wrote:
Len,

Thanks for the input and observations! Comments follow:

wrote in message
oups.com...
Firstly, 108 to 118 MHz is the international civil
aviation radionavigation band. It's not all that
interesting to listen to unless a local tower is
also repeating voice comms over a VOR or Localizer
radionav transmitter nearby on the ground. The
civil aviation voice band is 118 to 137 MHz.

Agreed - not that interesting to listen to, but the NAV
channels are exactly what I'm interested in - (both VOR
and LOC). The "experiment" I have in mind is a processor
controlled scanner of sorts that tracks multiple VORs
and performs as a backup to GPS. Hence the need for
fast/agile tuning (either PLL or DDS). As you may have
gathered - I'm not an "RF guy" by any stretch - but I'm
attempting to learn (out of sheer necessity 8-).....

snip

Neither the range nor the accuracy of VORs is all that great on
the ground.

What do you intend to do with this doo-dad other than experiment if
I may ask?

--
Jim Pennino

Remove -spam-sux to reply.

wrote in message

Neither the range nor the accuracy of VORs is all that great on
the ground.

What do you intend to do with this doo-dad other than experiment if
I may ask?

For now it is strictly entertainment/education. If it works out, however,
I plan to use it as part of a complete FMS for something like this:

http://members.eaa.org/home/homebuil...ng%20flea.html

Good point about the range/accuracy on the ground - I'll do a special
version for Moeller and Bede products 8-).....

"Netgeek" writes:

Len,

Thanks for the input and observations! Comments follow:


Agreed - not that interesting to listen to, but the NAV
channels are exactly what I'm interested in - (both VOR
and LOC). The "experiment" I have in mind is a processor
controlled scanner of sorts that tracks multiple VORs
and performs as a backup to GPS. Hence the need for
fast/agile tuning (either PLL or DDS). As you may have
gathered - I'm not an "RF guy" by any stretch - but I'm
attempting to learn (out of sheer necessity 8-).....

HAH! I did **EXACTLY** that project back in 1996 or so.

Used the 145151 PLL that someone else reccomended.

The RX was the ... crud .. can't remember the part number ... That
motorola 3300 part that was so popular. 3356 maybe?

Used a cheap 567 to track the FM part of the signal, and a simple
envelope detector for the AM part. It was barely adequate for
close-in stuff, and for long range stations, the noise performance was
terrible.

The outputs of the two detectors went into a two-channel 8-bit ADC and
were read by the CPU.

Used a 68HC000 for the CPU, and had a database of VOR stations burned
into the ROM.

The cleverest piece of code was the CW decoder that was used to ID the
stations.

It would tune around, listening to IDs and take a
best-guess at where it was, then build a list of stations to scan,
stopping on each one for a second to get a RMI fix. (There was a
little crude LPF to help with the noise performance. Not that it did
much good... )

I found some nice 4-line x 20 char LCD displays at a local junque
shop, with ENORMOUS characters. 0.6" I Think .. Just HUGE for LCDs
.... It would do a scrolling display of the form

SJC 025 nm @ 036
OAK 044 nm @ xxx

etc.

All in all it was a fun project -- with lots of cool learning
experiences. In terms of practicality, the performance was never
spectacular, RF noise from the CPU section would get into the IF
(21.4 MHz)... it made a neat cockpit toy, but I would **NEVER** have
considered it even a backup aid to navigation.

Just writing about this is making lots of little details come back to
me. Feel free to e-mail and I'll bend your ear.

-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Lawrence Statton - m s/aba/c/g
Computer software consists of only two components: ones and
zeros, in roughly equal proportions. All that is required is to
sort them into the correct order.

From: "Lawrence Statton N1GAK/XE2"

HAH! I did **EXACTLY** that project back in 1996 or so.
snip
Used a 68HC000 for the CPU, and had a database of VOR stations burned
into the ROM.
All in all it was a fun project -- with lots of cool learning
experiences.

Sounds like a cool project! *MANY* years ago (circa 1984 or so?)
I had a plan to tear off the front panel of an RST radio I built and
replace it with a display, some controls and a zillion parallel bits to
replace all the thumbwheels switches - all driven by a Z80. I
eventually decided it would take way too long and didn't
accomplish much, besides just being a generally stupid idea 8-)..
So I sold the radio...

Now, twenty years later I'm playing with *this* project! All of
which proves that I now have way too much time on my hands and
I'm getting more stupid as I age 8-)......

Would like to hear more about your experiences. So, what would
you do differently if you were starting over?

I'm thinking that something like a cheapo DSP (or one of the new
dsPIC widgets) might be real handy. But first - I have to get past
the part where I have a reasonable RF front end! I really doubt that
the $40 Ramsey kit is going to do much but I bet I'll learn a few
things 8-)........

I'm not locked in to the MC1350 - it just happens to be
what's used in the "ultra-cheap" kit I ordered. As it turns
out, there's a company (Lansdale.com) that seems to be
forming a business model around buying "obsolete" IP
from Motorola et.al. and keeping the parts available.
Interesting idea. As it happens, NTE has a drop-in
replacement part for the MC1350 in their "NTE746" -
available from Mouser. May be of interest to some on
this group???

The absolute minimum operating voltage for the MC1350 is 12 volts. Not
11.9, 12. If this is a mobile application, then figure on a switching power
supply to get you up to 15 volts or so.


Among that stuff is an HP8654A
good to about 520 MHz that I've never used (and for the
life of me can't figure why I bought 8-)........


Oh, I'll take it off your hands for $20 or so {;-)


Jim

"RST Engineering" wrote in message

The absolute minimum operating voltage for the MC1350 is 12 volts. Not
11.9, 12. If this is a mobile application, then figure on a switching
power
supply to get you up to 15 volts or so.

Thanks for that tip - it will be the first "improvement" to the cheapo
Ramsey receiver (which runs off 9 volts). The power supply is something
I *can* handle easily 8-)...

Among that stuff is an HP8654A
good to about 520 MHz that I've never used (and for the
life of me can't figure why I bought 8-)........

Oh, I'll take it off your hands for $20 or so {;-)
Jim

Well, give it a few weeks! Once the frustration level gets high
enough and I realize that I'm really a bit-banger and not a radio-head
I may be tempted to toss it (and anything else RF related) out the
window - in which case I'll pack it up and donate it to you 8-)...

In the meantime, any other suggested improvements or hints are
most appreciated (e.g. "up the IF from 10.7"?)...!

Thanks,
Bill (Who still thinks the universe *IS* digital - but infinite resolution
8-)

I'd probably jack the IF up to 45 MHz. (use TV parts; this is the TV IF
frequency) or 70 MHz. (satellite IF frequency), and then downconvert to
either 21.4 or 10.7...there are cheap crystal filters at both frequencies.

Jim


In the meantime, any other suggested improvements or hints are
most appreciated (e.g. "up the IF from 10.7"?)...!

Parts are on the way...

First IF = 45 MHz
Second IF = 10.7 MHz

Any point in going further to 455 KHz for a third IF or just stick
with the 10.7 - (MC1350 plus IF transformer) scheme?

Bill

"RST Engineering" wrote in message
...
I'd probably jack the IF up to 45 MHz. (use TV parts; this is the TV IF
frequency) or 70 MHz. (satellite IF frequency), and then downconvert to
either 21.4 or 10.7...there are cheap crystal filters at both frequencies.

Jim


In the meantime, any other suggested improvements or hints are
most appreciated (e.g. "up the IF from 10.7"?)...!