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???

Thanks for any help...

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???

The band in question is AM and the 13135 is an FM chip with discriminator. A
perfectly fine lineup for your needs is any of the DBM's from Mini Circuits
Labs or build you own with a few diodes and a couple of ferrite beads, the
MC 1496/1596 is still very much available, even made the transition to SSOP
if your tastes run to small and surface mount. Low side injection with an AD
9851 or high side with a 9951 DDS. With the channel spacing up there, a
selection of an inexpensive Murata filter will do your selectivity, and
audio is a VERY wide selection.

W4ZCB

Get youself an inexpensive collection of readily available parts from
rallies and car boot sales and then ask yourself what you can make out of
it.
----
Reg.

Netgeek wrote:
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???

Thanks for any help...



Kits:
http://www.hamtronics.com/r121.htm
http://www.vectronics.com/products.php?prodid=VEC-131K
http://www.hobbytron.net/R-AR-1.html
http://www.ramseyelectronics.com/cgi...ction&key=AR1C
schematic and other info on one of the kits:
http://www.uoguelph.ca/~antoon/circ/aviarx/aviarx.html

kits are an easy way to get those Unobtainium plated parts in small
quantities.

Thanks for the suggestions. I ordered the Ramsey kit as a way to have
something to play with for now.

Next step is to lash together either a PLL-VCO combo or DDS to
control the tuning from a cheapo processor (e.g. PIC). Any
suggested starting points for this would be much appreciated (for
example "National LMX2xxx plus Minicircuits xx" or "forget that,
AD DDS is better because.......")....8-).

The guts of the Ramsey widget consists of an SA602 and an
MC1350 (single conversion with 10.7 Mhz IF). Potential ways to
"improve" upon this???

Thanks again.
Bill (RF Newbie - but willing to learn 8-)...

"bigamps" wrote in message
...
Kits:
http://www.hamtronics.com/r121.htm
http://www.vectronics.com/products.php?prodid=VEC-131K
http://www.hobbytron.net/R-AR-1.html

http://www.ramseyelectronics.com/cgi...ction&key=AR1C
schematic and other info on one of the kits:
http://www.uoguelph.ca/~antoon/circ/aviarx/aviarx.html

kits are an easy way to get those Unobtainium plated parts in small
quantities.

It would be easier to convert an old AM/FM tuner or AM/FM stereo and you can
get them all over the place for a few bucks. Tube types are collector
items but the older SS ones with discreet components and ICs are considered
pretty much obsolete. Find one with an open tuning cap and remove a plate
or two, or rewind the coils (too much work) or replace the enclosed tuning
cap with an open one. Add an 11 mhz osc and use the 455Kc IF stage and AM
detector.

--

73
Hank WD5JFR

"Netgeek" wrote in message
...
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???

Thanks for any help...

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.

"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.