FS-4 for the Drake R-4 and SPR-4 Receivers
article was published in the June, 2004 issue of QST.
available from the ARRL for a nominal charge
Search the ARRL
Website - at one time the article was posted for free
Picture of the Crystal
Eliminator mounted in a MS-4 Speaker Enclosure for my R-4B
Picture of the Crystal
Eliminator built in a small Hammond enclosure for my SPR-4
This is a
Do-It-Yourself project. All the information required to build one of
these on your own is in the article - please read the article first
to answer any questions you may have. At the present time I can
supply some small quantities of the MC145170 PLL chip and
pre-programmed PIC Microcontrollers just as a help to people (feel
free to contact me for availability information). The PIC code is
free to download on the ARRL Website. FAR Circuits did at one time
supply a partial kit of components - contact them directly to find
out their current status. I have no business connection with FAR
Circuits in any way so I cannot answer directly for them. Thanks for
your understanding and have fun with your "Full band" Drake
*** Below is
a current FAQ for the project as published in QST ***
Drake made a great series of
receivers over the years. The best were called the R-4 series and
even today some 35 years after their first release they are very fine
radios. My personal collection consists of a R-4B and a SPR-4 (The
solid state version). These radios were advertised as "Programmable"
-- That is by adding a crystal they could tune any 1/2 MHz segment of
the HF bands from 1.5 - 30 MHz. They came configured for the Ham
bands (80-10 meters) and always had extra crystal positions for
shortwave frequencies or utility bands, etc. But you could never add
enough crystals for full coverage of the HF bands. The SPR-4 had the
most bands available - 23, but even that allows only less than half
of the available HF tuning spectrum. Drake also had a synthesizer (I
call it a crystal eliminator) called the FS-4 that allowed full band
coverage from 1.5 - 30 MHz. These are still available today on places
like ebay, but they are very expensive. I decided to build a modern
version of the FS-4 that I could actually afford to own. My version
allows full HF band coverage but with the modern elements like a 2
line LCD or very pretty VFD display, single knob tuning, etc. This
project is fully documented in the June 2004 issue of QST. Reprints
of the article are available from the ARRL. Other sites on the web
have more information on the original Drake FS-4, so "Google"
1) Big Oops! The MC145170 part
number specified at Newark is for the WRONG package type. The proper
Newark part number is: 01C4669, for the proper Freescale (formerly
Motorola) part number MC145170D2R2. I'm really sorry about any
inconvenience this may have caused anyone, this was totally my fault.
For all the different package types check out the data sheet for the
MC145170 at www.freescale.com. If you bought the wrong part from
Newark - they will give you your money back on an exchange - they
want you to have the correct parts and be happy! :-)
The MC145170D2R2 part number
decodes as follows:
MC145170D2R2 = The base part number
MC145170D2R2 = The package type, SOIC here
MC145170D2R2 = Means revision 2 (or -2) of the part
MC145170D2R2 = Newark has this designator on their
website, but it means tape and reel. You will be buying the part as
bulk so this doesn't matter or really apply.
In April 2005 Motorola (Freescale) finally obsoleted the last part I
wanted to buy from them - yep the MC145170. There are still thousands
in the supply chain and I secured about 30 of them for this project.
If you are having problems finding the chip, feel free to contact me
and I can get you one of the ones I have for my cost plus shipping.
2) If you bought a kit from FAR
circuits and have not assembled it yet, please contact FAR Circuits
for updates since there were many 'Startup' problems getting this
project going. I believe that the problems were taken care of by July
3) The VCO can be bought from
www.minicircuits.com or you can purchase the short kit from FAR
circuits that contains this part. Contact FAR Circuits at:
http://www.farcircuits.net. Minicircuits has changed their minimum
order quantity to 5. This was done in the last six months and follows
years and years of being able to buy just one of anything. Things
just keep on changing! I was told however, that if you call your
local Mini-Circuits rep they would be able to let you place an order
for just one. Thanks for the info Jim.
4) The VFD specified at Digikey
is obsolete - Digikey now carries the Noritake CU16025ECPB-W6J. This
new part is a drop in electrical replacement. However the replacement
VFD draws a bit more power than the original and to keep R100 cooler
you can fashion a small clip-on heatsink as shown
here. Use a small piece
of scrap aluminum and make the fins as long as will fit in your
enclosure or you can wrap them over and attach them to the die cast
metal shielding box or your chassis. Even the short 1" fins shown
here will sink off quite a bit of excess heat.
Hey guess what? The LCD
specified at Digi-Key is now obsolete as of August 2004. Mouser has
P/N HDM16216H-B-S00S, which is a drop in replacement - Same with the
Jameco # 171715 It will also work fine, although it is slightly
smaller that the pictures of my units show.
5) The PIC16F876A may be
getting easier to find than the non A version. The same bits work for
either part - BUT your programmer must know the difference from an A
to a non A part. This is because the programming algorithm is
different between the two parts. You may be able to get samples of
this part for free from Microchip. Try them at
6) Many suppliers and
distributors sell the other parts so check around.
Jameco, Allied, Radio
Mouser, Newark, Ocean State
TI, Analog devices, Maxim,
National, Microchip and others also offer free samples in many
If you have any trouble with a
specific part - call the manufacturer. They don't care who you are or
who you work for - really! All they want is for you to be able to get
their parts and be happy! They will sample parts in many instances
and they can tell who has stock of the particular part instantly -
over the phone.
7) Digikey may not have the
original OP27 that was specified, but recently they had over 3000
OP27GP and OP27EP devices. These will also work in the
8) The Grayhill rotary encoder
specified was a 25LB45-Q. Other substitutes that will work are
These are the same switches,
except they have a different number of detents than the original.
Newark carries several of the others.
9) Please note that we are
coming out of the worst technology downturn ever. Approximately 25%
of the worldwide manufacturing capability was taken off line in the
last 4 years. Now that the economy has improved - lead times are
increasing. This has resulted in 8-12 week lead times on many parts
in the industry, perhaps even some of the ones specified for this
project. If you let me know what you are having trouble finding, I
will do my best to help you out.
10) A number of folks have
asked how I make the front panels and labels for my projects - I make
them basically the same way Neil does at AADE, in fact he has some
good ideas I didn't even think of -> So check out his site at:
http://www.aade.com/sexypnls.htm. Scott Edwards also makes some
really clever little stick on bezels (great when you can't cut a
straight, square hole - like me!) Look for them at www.seetron.com.
Digikey also sells plastic, stick on bezels (That's what's on my
SPR-4 version face plate as shown above).
11) Where's Waldo part 1 - Jim
let me know that C23 was mislabeled on the ARRL schematic. The parts
list is correct however and C23 is really a 120 pF capacitor. To tell
you the truth - I looked at a simulation of the filter with a 82 pF
capacitor like the schematic says and I believe the unit will work
just fine either way.
12) A chap asked about using
sockets for the IC's. You should not need sockets for any of the
parts. I only use sockets for the PIC when I am developing code as
this allows me to remove the part for programming. So a socket for
the PIC is optional.
13) Where's Waldo part 2 -
Somehow I mistyped "Orion" instead of "Omron" for the relay
manufacturer ( www.omron.com ). My typo...
14) Where's Waldo part 3 - The
parts list printed in QST lists C31-C36 for 0.1 uF capacitors.
However C33 and C35 are not used. It should have said C31, C32, C34,
15) Apparently FAR circuits has
substituted a "House Numbered" device for U6. I have no idea what
this device originally was, however the one I saw appeared to have a
1985 Date Code on it. I have seen one case where there were huge 4-5
kHz sidebands on the output which manifested itself as an AM
modulated tone on the receiver audio output. The cause of these
sidebands was because the substituted regulator was oscillating. If
you have this problem, replace U6 with the specified part. Radio
Shack, DigiKey, Mouser and Jameco carry suitable 7805 regulators. You
can spot this problem with a DVM: Set the DVM to AC RMS, 200 mV Full
Scale and measure the output pin of U6 and compare this reading to
the reading of the other two regulators. If U6 measures appreciably
more ripple on it's output than the other regulators - it is probably
16) I saw a unit with a 74AS74
substituted for the 74AC74 part specified. It worked amazingly well -
however the AS part draws considerably more power than the AC part
specified and causes the PLL to loose lock at the higher frequencies.
The AS part is also not nearly as well behaved driving the LC filters
as the AC part is. I suggest that the originally specified AC part
only be used. Also ACT parts are not the same as AC and I don't
recommend them either, please stick to the parts specified.
(www.crystalfontz.com) makes some wonderful LCD displays in many
colors for very reasonable prices. If you are looking to make a
'fashion' statement with your unit you should check them out. Their
16x2 character modules work just fine with the Crystal Eliminator
code as is. You may find that some of their displays need to have a
contrast adjustment. This is not to fault their displays as they are
excellent - however you may want to connect a 10 k trimpot between
pins 1 and 2 with the wiper going to pin 3. This will allow the
contrast to be adjusted - see their data sheet if this doesn't make
18) I found a few errors on the
schematic as published by the ARRL. I have attached the original
schematic here for your download. The original schematic was in the ARRL
download package also. As far as I know the PCB's have always been
correct, these were transcription errors from my schematic to the
- On U2, the + and - symbols
are reversed, however the pin numbers are correct.
- On U4B - Pin 10 really goes
to pin 14 of U4A, not pin 3 as shown.
- The value of C101 on my
original schematic is not really an error - between the original
design and the ARRL publication I changed part values and types to
a more obtainable type. Use the part
specified on the ARRL material list.
19) I have seen people with PLL
problems, mostly these problems have been solder joints at the PLL
IC. Use a microscope and be very careful. A short or an open here and
the PLL won’t work.
20) As the article stated - the
FAR circuit boards do not have plated through holes, so everywhere
there is a trace on the bottom side and the top side there needs to
be a solder joint on BOTH sides! Use an ohm-meter to trace the
circuits. I have seen many instances of this around the 74AC74 flip
flop. It is hard to see the traces on the top side the way I laid
them out (sorry 'bout that) put a jumper on the backside if you need
to. If the 74AC74 is not working then the PLL will not work. Use an
ohm-meter to trace the circuits.
21) People seem to be getting
confused by the negative supply to the OP-27 not being regulated.
Here is the full story on this. As long as the negative supply is
below about -4 volts AND the total supply voltage across the OP-27 is
less than 40 volts, the OP-27 will work. The OP-27 has more than 80
dB power supply rejection ratio at 120 Hz. So ripple on these lines
does not affect the PLL at all. If the PLL is tuning and stable, then
these power supply voltages are probably OK.
22) The PIC must have a clock
signal to run. If the PIC appears not to run, then check to be sure
that it is getting a clock. The clock to the PIC initially starts out
at 10 MHz / 8 = 1.25 MHz - this is the way the PLL IC defaults to on
power up. One of the first things the PIC does is program the PLL IC
to make this 10 MHz. If the PIC clock never changes to 10 MHz, then
the PLL IC is not getting programmed.
23) All of the errors I have
seen so far are with the wrong parts being used (one even had a
7905.2 negative regulator where there should have been a 7805
positive regulator - also see above) and
soldering. After 35 years or so of soldering I know how frustrating
this can be so have someone else check your work if possible and keep
at it you can figure it out. It might be best to only work on a
section at a time and carefully checking with an ohm meter. Too much
time spent looking for a problem is counter productive, take a break
and try again tomorrow.
24) People seem to be getting
confused about the 10 MHz clock needing to be right on - while that
is a worthy goal, step back and think how the Drake originally
worked. The crystals weren't specified to be exactly on frequency,
nor were they trimmed. The R4 series had a slip calibration on a knob
and the cross hair was movable to make up for this error. Once the
dial has calibrated out any PLL error the error tracks to the other
bands because the PLL is locked to the same crystal. The accuracy of
the synthesizer between bands is better than the Drake originally had
with it's many crystals. Certainly better than the PTO accuracy which
on my drakes is about +/- 500 to 800 Hz across a single band.
25) Pin 21 of the PIC is
labeled "Debug PLL". Normal operation is to leave this pin open. If
you ground this pin and power-up the crystal eliminator the PLL IC is
programmed to make three pins active (See article page 29, 2nd
column). The reference frequency (Fr) to the phase detector is put
out on Pin 9 - should always be 200 kHz for a R4 version or 20 kHz
for a SPR-4 version. The output of the N counter (Fn) is output on
Pin 10. If the PLL is locked this should be the same frequency as pin
9. If the VCO frequency is too high then Pin 10 would have a
frequency that is greater than Pin 9, etc. In Debug operation The
Lock detector output is also active. When the PLL is locked this pin
will be at a high level with negative going pulses if the PLL is
locked. If the PLL is unlocked (Fr and Fn are at different
frequencies) then this pin will be low. More information on these
pins can be found on the MC145170-2 Data sheet which can be found via
a Google search of the web.
26) On the schematic: Pin 26 of
U101 it says: "VFD OFF... No Function with LCD" Actually this pin
will blank the LCD also. This will manifest itself with the display
going blank after a power on message. So if your display works for a
second, then goes blank make sure that this pin is open.
Here is a list of some
of the units I have fixed and the problem found...
Symptom: Works fine, then just
stops after a few minutes to a few hours.
Problem: Bad solder joint on a
topside trace - component was not soldered on top - intermittent.
(This was one of my units! - Very embarrassing....)
Symptom: Multiple parts get red
Problem: Multiple PCB shorts.
7905.2 installed where a 7805 should have been. That's a negative
regulator! Pull all the regulators and put them back in one at a time
until the problems (shorts) are resolved.
Symptom: PLL doesn't seem to
lock. Looks like PLL loop is oscillating.
Problem: Voltage regulator
oscillating. Unknown regulator part type installed where a 7805
should have been. Who knows what that part really was?
Symptom: PLL won't lock at
Problem: 74AS74 installed where
74AC74 was specified. "AS" part does not work at high VCO
frequencies, also draws too much supply current causing V+ on OP-27
to get below minimum for operation.
Symptom: PLL does not work.
Problem: Pins at PLL IC are
shorted with solder, clean pins - unit works.
Symptom: OP-27 output is at -6
volts or so, never moves.
Problem: Pin 7 of OP-27 is at
-6 volts (should be +17 volts or so). Bad solder joint on capacitor
C31 and C36, no positive supply on OP-27.
Symptom: U5 is hotter than the
Problem: Using my highly
calibrated finger I found that Tantalum capacitor C14 was hotter than
the sun too! Ouch that hurts! C14 was found to be backwards. Fix C14
and what do you know? U5 is now cool as the morning air in
Symptom: Unit does nothing.
Problem: Crystal not soldered
(bad solder joint), resulting in no clock at PIC. The PIC must have a
clock to run. This is one of the first things to look for if the LCD
display does not light up - check the PIC clock.
Symptom: Unit works, but The
OP-27 Seems to be stuck at the positive rail most of the time. The
PLL seems to sortta lock at the lower frequencies - but then get's
Problem: 74HC74 used where
74AC74 was specified. The HC part is only rated to 30 MHz! Also a 20
MHz crystal was used where a 10 MHz unit was specified. Both these
errors make the PLL operation very iffy. Troubleshooting consisted of
first looking at all the parts for proper values. This unit took
about 15 minutes to fix because the problems were all in plain sight.
A general tip: If the unit
doesn't work, check all the IC's voltages right on their pins. This
will show where the bad solder joints are.
A general tip: If one of the
regulators or an inductor in the power supply lines gets hot - feel
around to see if some component is hot - if it is in backwards it
will likely get hot too (like a Tantalum capacitor). If nothing else
gets hot then there is a solder short to ground somewhere on the
output of that regulator. You can trace this out with a
This is what the
engineering prototype looked like. Fully functional breadboard used
to verify PLL operation, spurious levels and to develop the PIC
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