Subject: Re:Yeasu FT-470 mods?

Date: 6 Jan 93 00:26:26 GMT


>In article <9301041923.AA01850
>>  A few weeks ago, I purchased an FT-470 2m/70cm HT.  I've been monitoring

>>this newsletter for about 2 months, but so far have found no references to any

>>mods pertaining to this HT.  I do not have access to ftp, but would welcome e-

>>mail, or a posting here advising me of possible mods to increase receive

>>bandwidth, etc. --- or any other information of interest about this model.


  Yaesu FT-470 MODS

 Rev D (Aug 28, 1992)

This is a collection of hardware and software mods for the Yaesu 470.

I have collected every mod seen on the net (ie. Usenet) since the

introduction of the 470, so I think this list is fairly complete.  I

am interested in getting updates and corrections to this list, so

please send me e-mail if you find something that needs updating.

(This includes typos, wrong or missing attributions, caveats, warnings

about unmentioned side effects, serial numbers of radios that won't do

some of these mods, etc.)



This advice is free, so remember that you get what you pay for.

Brian McMinn (brian



Full Reset:

Effect:Severe! :-)

1) Make hard (paper) copy of all memory info

2) Turn radio off

3) Hold down VFO and MR and turn radio on

4) Replace all memory contents

Notes: This will reset the auto repeater offset function, so

you will need to re-enable it if you use it.  This will also

disable (mask) all memories except #1, so you will have to

enable each of them by hand.




Effect:Enable extended 2m receive, 2m transmit

1) Make hard (paper) copy of all memory info

2) Turn radio off

3) Hold down up-arrow and down-arrow and turn radio on

4) Replace all memory contents

Notes: This mod wipes all memory contents.  This is a "toggle"

mod in that it can be un-done by repeating the above steps.

The normal->MARS mod only wipes the memories.  The MARS->

normal mod not only wipes the memories, it appears to do a

complete controller reset (see above).

Result:Receive range 130-180 MHz, transmit 140-151MHz (I

think, I haven't tried it.)



Crossband Repeat:

Effect:Enable crossband repeat

1) Dial up two frequencies you want to crosslink (be sure to

   pay attention to transmit offsets, if any)

2) Turn radio off.

3) Hold down the RPT key and turn radio on

Result: The tone encode/decode flags and the -+ flags will be

flashing and the radio will be in low power mode.  When either

band's squelch opens, the other band is moved into the primary

frequency display and the transmitter keys.  Audio link

appears to be speaker to mike.

Attributed:Collier Chun (NM7B


Crossband Repeat Audio Cable:

Effect: Provide better audio for crossband repeat.

1) Parts:

 a) mini plug

 b) 100K ohm resistor

 c) sub-mini plug

2) Assemble cable with resistor connecting the tips of the two

   plugs.  The shield (ground) is not connected.

3) Plug it between the earphone jack and the mike jack.

Result: Very good crossband audio.  The level is controllable

with the volume control.

Bugs: You can't listen to what is being repeated.

Attributed:Keith McQueen (N7HMF


Clone Mode:

Effect: Allow editing of transmit and receive frequencies.

1) Turn radio off.

2) Hold down F key and turn radio on.

Result: All segments of display are turned on.  The radio

will send data out the microphone tip when up-arrow is

pressed.  The radio will receive data when the down-arrow is


Bugs: I have yet to hear of someone who has done this

successfully.  Please tell me if you know how it works!

Attributed: szarekw


Internal Jumper Mods:

Effect: Change radio from US to European to ???

  Wide band receive

I have located a total of eight straps, four to the left of

the lithium battery, and four others under the flat white

cable that interconnects the upper half with the lower half.

 Yeasu FT-470 Straps

R69  Vertical, at the 10 o'clock position by the lithium cell

R68  Horizontal, to the lower left of R69

R67  Horizontal, just below R68

R66  Horizontal, just below R67

R71  Vertical, the leftmost of three, to the left of the upper

     corner of the ribbon cable connector.

R70  Vertical, the center of three of which R71 is the leftmost

R72  Vertical, the rightmost of the three

R74  Vertical, to the left of the ribbon cable connector, below

     the three.  (Note that R74 is below an unpopulated capacitor

     that does not have a C number.

There is no R73, or at least it is not on the circuit board

and it is not in the schematic.  And, yes, the order of those

three is indeed R71, R70, R72, left-to-right.



R71R70R72Rx and TxRx only


000430 to 440430 to 500

001430 to 450

010430 to 440

011432 to 438

100430 to 440**

101220 to 225

110430 to 440

111210 to 235


** This is the normal European configuration.



R66R67R68R69Rx and TxRx only


0000 144 to  146130 to 180

0001 144 to  146

00101260 to 1300

00111240 to 1300

0100 140 to  150*130 to 180

0101 140 to  174

0110 303 to  343

0111 8AL to  242

1000 144 to  148

1001 144 to  146**

10101240 to 1300

1011 404 to  444

1100 140 to  160

11011260 to 1300

1110 101 to  141

1111 1R3 to 158L


* This is the normal US configuration after MARS mod.

** This is the normal European configuration.

(Note:the receive only ranges are enabled by powering up the

unit with the up and down arrow buttons depressed...kjm)

When there is more than one combination which has the same

frequency range, the difference is the default step size

and/or the default repeater offset.  Of course, choices that

do not match the VCO and filters do not actually transmit or

receive on those frequencies.  A particularly strange example

is that the VHF side of the set can be set to tune from 404 to

444 MHz, but again, it won't actually lock.  Even in the

101-141 mode, the VHF VCO will not lock - this must be for use

with some other sort of VCO (It looks like this would cover

the aeronautical band rather nicely.)  There are two really

wierd VHF settings, those for 8AL-242 and 1R3-158L.  These

must be for use with some other LCD controller - it displays

truly unusual and non sequential thins when stepped through

the "bands".

R74 seems to have something to do with selecting the IF

frequency, or something similar.  When set, it really screws

up the VHF reception.

My technique for determining these straps is to remove the

straps that come in the unit, solder wires to each pad, run

the wires out of the unit to a bank of DIP switches, screw the

unit back together, and then go through all of the DIP switch

combinations.  I usually use a stereo microscope and 30 guage

wire for this.  Since I didn't try powering the unit on with

every combination of keys held down for each DIP switch

combination, there may still be other secrets possible.

I was looking for something like receive and transmit from

zero to infinity, but I didn't find it.  I determined, from

studying the schematic, that there should be a hiddem

strapping diode from CPU pin 2 to CPU pin 22.  I installed

one, but nothing changed.  In fact, changing it and powering

the unit up did not cause a reset.  Therefore, I concluded

that this really wasn't a mystery strap, afterall.  However,

there could be others.  I'm trying to get a data sheet for the

CPU, from Hitachi, to see if any of the grounded pins are

actually I/O pins -- they might be good candidates,

particularly if their traces are routed in such a way as to be

easily accessible for cutting.

I've learned that one of the ways to get some of the other,

new Yeasu handhelds to go out-of-band involves dumping data

out of the clone port, editing the data, and then dumping it

back in.  I called Yeasu and asked if the FT-470 could be

cloned.  They said no, so I ignored them.  I haven't figured

out how to get it to dump data, but I believe it will accept

data.  The clone mode is entered by powering up the unit with

the F key held down.  (It's also a neat way to see all of the

indicators on the LCD!)  The data must be presented in the

ring ("right channel") of a stereo 2.5 millimeter plug which

is placed into the mic jack.  This is cryptically marked on

the schematic, anyway.  However, I have no idea what the

format for the data should be.  If you come across this, I'd

love to know.  This may be the trap door to getting the rig to

receive and transmit in more interesting places.

Attributed:Ed Boakes (WB3FLD) att!hocpa!ewb


VHF Transmit mod:

Effect: Enables extended VHF transmit (this is exactly the

    same as one of the previously listed mods).

1) Open the radio such that the two halves openlike a sandwich.

2) Locate the internal lithium battery

3) Locate several solder pads to the left of the lithium battery.

4) Just to the top left of the lithium battery is ONE vertical

   solder pad (a.k.a. R69).  It is almost under the top left

   edge of the battery.

5) solder a jumper accross this pad.

Result: Extended VHF transmit

Bugs: The automatic repeater shift (- offset below 147,

+ above etc...) goes away with this mod.

Also attributed To: Bernie NU1S


Software UHF Receive Expansion:

Effect: extend UHF Rx to 500MHz without shrinking Tx range

How: Trick 470 into accepting big number in U register.

Caveat: This mod acts differently on different radios.

1) Turn the beep on.  (Some, perhaps all, 470's require that

   the key-press-beep function be on in order to do this.)

2) Program the frequency of 450.00 MHz simplex.

3) Set the repeater offset to zero (F/M RPT 0000) but DON'T

   get out of the set mode (don't hit RPT again).

4) Turn the radio off then back on.

5) Set a "+" offset (press RPT twice).

6) Press the REV button one time.

7) The radio should now display 1450 MHz.(The radio will not

   operate at these frequencies.  My service monitor shows

   that above 500 MHz the rx is very weak.)

8) Use the shifted down-arrow key to tune this frequency down to

   around 500 MHz (press F/M, press and hold down-arrow).  Yes,

   this takes a while.

9) Store this in the "U" memory.  (press and hold F/M until

   you hear two beeps, rotate tuning knob until "U" appears in

   upper left, press F/M again).

10) Reset the repeater offset to 5 MHz.  (F/M RPT 0500 RPT)

Result: By selecting the "U" memory and the using the memory

tune fuction (select "U" memory and then press MR), you can

tune to the desired frequency and then store it in another


Bugs: Above 500 MHz, some radios will let you tune up and

down in frequency, some won't (they jump back to the ham

band).  Some radios will let you enter a frequency above 500

MHz on the keyboard while in memory tune mode, some won't.

Attributed: Darrell Sego KM9S


Software Range Extention Tricks:

Effect: Force a non-standard frequency into a VFO, store this

as an upper limit in the "U" or "L" memory.

Caveat: For these steps to work properly, I had to have

"Beep" enabled and *NOT* have the "L" and "U" memories locked


Steps for setting the UPPER UHF limit to 500 MHz

1.  Program the frequency for 430.00 MHz *SIMPLEX*.

2.  Press F/M, then RPT for the offset.

3.  Enter the code 0000 into the keypad.

4.  Shut the transceiver off, then turn it back on.

5.  Press RPT key twice for a "+" (plus) offset indication.

6.  Press REV button once.

7.  The radio should now display 1430.00 MHz.

8.  Press F/M then hold the down-arrow key to lower the

    displayed frequency.  Stop when 500.00 MHz is displayed.

9.  Press RPT once to select simplex operation.

10. Press F/M and hold until you hear two beeps.

11. Rotate the (DIAL) knob until the channel "U" is displayed.

12. Press F/M again, you should hear a beep.

13. Press F/M then RPT then enter 0500 (5 MHz repeater offset)

    then press RPT again.

    - alternative procedure (faster but a little more complicated)

8.  Press RPT twice to select the "-" repeater offset.

9.  Press REV twice.  Frequency shown should be 630.00 MHz.

10. Press F/M then hold the down-arrow key to lower the

    displayed frequency.  Stop at 500.00 MHz.

11. Press RPT twice to select simplex operation.

12. Go back to #10 in previous list...


Steps for setting the LOWER UHF limit to 400 MHz.

1.  Program the frequency for 450.00 MHz *SIMPLEX*.

2.  Press the F/M, then RPT for the offset.

3.  Enter the code 0000 into the keypad.

4.  Shut the transceiver off, then turn it back on.

5.  Press RPT once (for a "-" (minus) indicated offset).

6.  Press REV *THREE* times.

7.  The radio should now display 050.00 MHz.

8.  Press F/M, then hold the up-arrow key to increase the

    displayed frequency.  Stop at 400 MHz.

9.  Store this in the "L" memory.  (See above steps...)

10. Press F/M then RPT then enter 0500 (5 MHz repeater offset)

    then press RPT again.

    - alternative procedure

    - note: this short-cut requires you to enter 430.00 MHz

      in step 1.

5.  Press RPT twice for a "+" (plus) indicated

    repeater offset.

6.  Press REV once.

7.  Press RPT twice to select the "-" (minus) repeater offset.

8.  Press REV once.  You should have 1030.00 MHz displayed.

9.  Press F/M and hold the down-arrow stopping at 999.00 MHz.

10. Press REV once.  You should have 399.00 MHz displayed.

11. Press F/M, then hold the up-arrow) key to increase the

    displayed frequency.  Stop at 400 MHz.

12. Press RPT twice to select simplex operation.

13. go back to #9 in previous list


Steps for setting the UPPER VHF limit to 200 MHz.

1.  Program the frequency for 140.00 MHz *SIMPLEX*.

2.  Press F/M, then RPT for the offset.

3.  Enter the code 0000 into the keypad.

4.  Shut the transceiver off, then turn it back on.

5.  Press RPT twice (for a "+" (plus) indicated offset).

6.  Press REV *ONE* time.

7.  The radio should now display 1140.00 MHz.

8.  Press F/M, then hold the down-arrow key to decrease the

    displayed frequency.  Stop at 800 MHz.

9.  Press RPT twice to select the "-" (minus) repeater offset.

10. Press REV once.  You should have 200.000 MHz displayed.

11. Press RPT twice to select simplex.

12. Store this in the "U" memory.  (See above steps...)

13. Press F/M then RPT then enter 0060 (600 Khz repeater

    offset) then press RPT again.


Steps for setting the LOWER VHF limit to 100 MHz.

1.  Program the frequency for 140.00 MHz *SIMPLEX*.

2.  Press the F/M, then RPT for the offset.

3.  Enter the code 0000 into the keypad.

4.  Shut the transceiver off, then turn it back on.

5.  Press RPT twice (for a "+" (plus) indicated offset).

6.  Press REV *ONE* time.

7.  The radio should now display 1140.00 MHz.

8.  Press F/M, then hold the down-arrow key to decrease the

    displayed frequency.  Stop at 1100 MHz.

9.  Press RPT twice to select the "-" (minus) repeater offset.

10. Press REV twice.  You should have 100.000 MHz displayed.

11. Press RPT twice to select simplex.

12. Store this in the "L" memory.  (See above steps...)

13. Press F/M then RPT then enter 0060 (600 Khz repeater

    offset) then press RPT again.


Notes: To use the higher frequencies you have to select the "U"

channel and press MR.  This puts the handheld in the "MT" (memory

tune) mode.  From there you can scan down or use the (DIAL) knob to

go to a lower frequency.  ...Likewise for the lower frequency

memory.  Any frequency selected using this method can be stored in

any memory.

My radio will not let me go up in frequency, only down.  If I try, the

rig will default back to the original ham band.  I had to be careful

when doing these mods.

One trick I found when initially setting up the VFO with the

expanded upper and lower frequencies is that in steps 5 (and 9) if

you select "+", pressing REV adds 1000 MHz to the display or

subtracts 1000 MHz if it has already been added.  If you selected

the "-" (minus) repeater offset, pressing REV will subtract 400 MHz

if the displayed frequency is 1000 MHz or higher, or subtract 600

MHz if the displayed frequency is below 1000 MHz, until any more

subtractions would run the frequency negative, after which it

alternatively adds or subtracts 600.  You can mix the up-arrow

down-arrow method with the "+ -" offset/REV combination to reduce

the time getting to the desired frequency.  With these tricks, many

permutations can be found to get where you want to be very quickly.

I have discovered the code "5555" works as well as "0000" for the

enabling code.



Fix One-Way Tune Bug in Expanded Receive:

Effect:Allow tuning in both directions when software range extend

mods have been performed.

Due to a loophole in the tuning software, you may tune from the

current frequency towards the normal operating range (430.00 -

450.00), but not away.

Unfortunately, you are still subject to the "tune one way only"

syndrome.  To bypass it, you must store some frequency in the "L"

memory.  It doesn't matter what this frequency is, but it has to be

below the "U" memory and, preferably, below any other frequency you

want to use.  You may store a very low frequency here too


BUT, the software isn't that dumb.  To trick it, both the "L" and

"U" memories must be filled and active (not set for SKIP), AND you

must access the out of band frequencies from the MT (memory tune)

mode, AND you must start from either the "L" or the "U" memory.

To use MT:

1) Press MR and select either the L or U memory.

2) Press MR again, a small MT should appear on the left of the


3) You may now tune with the arrow keys, Dial knob, or directly

   enter frequencies with the numeric keypad.

[ed.  It looks like Pete may have been the first to discover some

of these neat tricks... any comments?]


Out of Band Sensitivity:

Effect: This is not a mod.  Just information.

I measured the sensitivity of my Yaesu FT-470 over frequency

to see how well it holds up outside of the ham bands.  I

wanted to see how useful the extended receive info being

handed out really was.

The measurement is a relative one.  I was using an HP8657

Signal Generator, with the internal FM modulation set to 5 KHz

deviation and a 400 Hz tone.  I input a signal with an

amplitude of -100 dBm directly into the RF input of the radio.

I noted the reading on the signal strength meter in the Yaesu.

On the VHF band the number nine was on steadily, on the UHF

band the number nine was blinking.  As I changed frequencies I

adjusted the amplitude of the signal generator to keep the

signal strength meter on the Yaesu at the same level.  The

amount I had to crank up the output of the signal generator is

the reduced sensitivity, here is the data:


freq:relative sensitivity:

136-14 dB

140 -3 dB

144 +1 dB

146  0 dB  reference point

148 -1 dB

155 -6 dB

160-22 dB

165-29 dB

170-38 dB

174-44 dB


freq:relative sensitivity:

400no reading, nothing, -infinity dB 

401-40 dB

402-38 dB

405-34 dB

410-27 dB

420 -9 dB

430 +1 dB

440  0 dB

450  0 dB

460-17 dB

470-26 dB

Results: The radio is good outside the ham bands, but the

sensitivity really starts to suffer.  I hear the local police

at 460.375 quite well, so -17 dB is still usable, but not as

good as a scanner would probably be.  VHF down to 100 MHz or

UHF down to 400 MHz is a fantasy.  As I mentioned in another

post, if the frequency ranges are extended too far, you start

picking up signals at the wrong frequencies.  National weather

service (162.4) received at 119 MHz, coast guard channel 12

(156.8) received at 200 MHz, 2 meter repeaters received around

190 MHz and again around 182 MHz.  Its hard to say just what

the usable ranges are, but something like 136-165 MHz in VHF

and 410-470 MHz in UHF, and even then its not great at the

ends of these ranges.




Effect:faster memory scan rate.

1) Go into Alt mode by pressing [F] 2 (Alt).

2) Press the Up or Down Arrow to activate the Memory Scan.

3) When the Scans stops on a VHF frequency on the Left Display (The

           Main Band), Hit [F] VFO.

4) Press the Up or Down Arrow to activate the HyperScan.

5) To Stop the Function, Press [F] Alt.

Result:Faster scan rate.  (Mod is non-permanent)

Attributed:KB2JFI ???


Extended RCV side effect #1:

     I have found what I would consider an interesting side

effect with my FT-470 now that I have performed the UHF

extended receive modification.  [not sure which UHF mod this

is, ed.]

     After I had done this mod, I found out that if I was

scanning (in either Memory Tune mode or band-scan mode(between

U & L)) the VHF side of the radio in the sub-band, and

listening to an extended frequency in the UHF main band, the

scanning would stop and revert back to whatever frequency it

started from whenever a signal was received on the UHF side.

(I don't know what frequency it reverts back to if you are

scanning a VFO, but I do know that a similar thing happens).



1750Hz tone burst:

     FT470's in the UK come with the 1750 Hz tone burst option

built in.  It is on a tiny sub card that is wedged in down the

bottom at one side.  I bought one from the UK distributors and

figured out how to connect it when I got back to the US.  As

far as I can tell my mod is the same as would be done if it

was officially installed although the service manual doesn't

show where to connect it.  It has just 3 wires, power, ground

and audio out. It is activated by applying power using the

small button above the PTT so you can press both at once to

call and then slide your thumb down to release the tone


     The board consists of a 2*color burst freq xtal and a

74HC4060 CMOS oscillator divider giving 7.16MHz divided by

4096 = 1748 Hz.  The chip is surface mounted so they can get

the whole thing down to less than 0.5" square.



Battery latch R&R:

     To replace the battery latch simply remove the battery

pack.  Looking at the bottom of the transceiver you will see

the battery retainer plate.  Remove the 4 screws from each

connor and lift the plate out.  The battery latch will come

with it.  Part of the retainer plate is used as a spring for

the latch.  Stick the new catch on the end of the spring and

reinstall in reverse order.

     I have broken mine twice so far.  The rest of the radio

seems to be pretty rugged and I have given mine a lot of

punishment so far and it seems to have taken it well.



Extended RCV side effect #1:

     After doing the software receive mod, the radio will pick

up 2m frequencies when the display is in the 180-190MHz range.

     Also, the ARS (Automatic Repeater Shift) will turn on

once in a while when scanning from 100 MHz to 200 MHz.

Attributed: plkorhon


TNC wiring:

The FT470 is wired like an Icom.  You connect the audio from

the TNC to the tip of the mike plug through a capacitor and

connect the PTT to the tip with a resistor.  The Icoms and

Yaesus use a "leaky ground" to generate PTT.  The problem with

this approach is there is a tradeoff between rapid PTT and

audio level and response.  Typical values are .1 ufd and 2.2 k

ohms.  The RC time constant limits TR turnaround.

A better scheme is to use a tiny audio transformer sideways

like so,

TNC PTT----------))))))))))))-------------> radio tip (audio)


TNC AF OUT-------))))))))))))----X--------> radio sleeve (gnd)


TNC GND--------------------------|

You can rip a suitable transformer out of an old transistor

radio or buy one from Radio Shack.

You should carefully set the audio level so you wind up with a

3 khz deviation for your tones.  Don't exceed that level or

many units will have trouble decoding your packets.  Make sure

you have the power saver on the 470 turned off when you run

packet or you'll miss the first part of every packet.  This

can drive you nuts because everything seems to be working but

nothing prints.

One last note: put some distance between the antenna and the

radio and use shielded cables on your TNC.  Otherwise the RFI

and RF feedback will ruin your packet operation.

Attributed: gary


DC power:

The 2 meter only model does have a power jack under the rubber

plug, but the 470 doesn't.  There's a place on the board for

one, but Yaesu recomends that you use a PA-6 module instead.

This is a module that mounts in place of the battery and

contains regulators for running the radio and charging a

battery connected to the bottom of the PA-6.  This is a really

nice accessory and well worth the price.

Attributed: gary


Power Consumption:

Here are some measurements on the Yaesu FT470.  Measurements

made with regulated 7.2 volt supply.  Power output measured

with Bird and appropriate slugs.

2 Meter Transmit



70cm Transmit




 As used below, "standby" means squelch closed, no

 signal received.

 Note: "PRIORITY" disables "APO", but not "SAVE"

 Note: Scanning disables both "SAVE" and "APO"

 Note: Open squelch disables "SAVE"

 SCAN or STANDBY, one band:  53 ma

 SCAN or STANDBY, two bands: 90 ma

 STANDBY, "SAVE", one band:  10 ma (53 ma active)

 STANDBY, "SAVE", two bands: 10 ma (90 ma active)

 "APO" does not change above.

Audio: 50 - 150 ma

WARNING: The FT470 shuts down and display goes blank when

supply voltage drops to about 4.8 volts.  BUT DRAIN CONTINUES

AT ABOUT 10 ma.  So, there is a danger of over-discharging

nicads.  Shut your equipment off to prevent this.

Attributed: WA2NQL


Intermod Cure:

I sent my Yaesu 470 in to Yaesu U.S.A. almost a month ago for

them to perform the modification to cure the intermod problem

and got it back yesterday.  They did cure the problem.  There

is no intermod at all on one repeater that I was previously

getting killed on.  There is also a noticeable improvement in

the sensitivity out of band on the weather frequencies.

Though my radio is almost 2 years old they did the work free

of charge.  I tried to have them send me the parts to do it

myself but I couldn't talk them into it.


Attributed: rogerm


Intermod Cure -- Affected Lot numbers:

There is a free factory upgrade for the FT-470 that applies to

models from certain lot numbers.  I believe lot #19 and lower

have terrible intermod problems.  Mods are made (supposedly)

to IF stages etc... and sensitivity as well as selectivity are

increased after the mod.  There may be other lots that have

problems as well (I know lot #30 has quite a number of

problems ie. batt saver not functioning correctly, low output

power, mushy squelch etc...).  The lot number is usually the

first two digits of the serial.

Attributed:Craig Lemon VE3XCL


More About Intermod:

The u2AT uses a varactor tuned front end filter to reduce

intermod.  It is able to knock out a lot of out of band

signals while still maintaining a wideband receive capability.

The tune voltage for the varactors is developed from the VCO

tune line.

There is a difference between intermod and spurious.

Intermods are developed when two out of channel signals mix to

produce an in channel response.  Third order intermod occurs

when the second harmonic of one of these signals mixes with

the other to produce an in channel response.  For example say

there are two repeaters on 146.88 and 146.82.  These two

frequencies will develop 3rd order products at 146.76 and

146.94.  Tuning the receiver to either of these frequencies

you would hear both conversations at the same time (assuming

their signal levels were high enough to cause the intermod).

A spurious response results when a single input signal, at a

frequency other than the desired receive frequency, mixes with

the first LO to produce an output at the first IF.  For

instance suppose that I am tuned to 145.21 MHz and my first IF

is at 21.7 MHz (as is the case in the 470).  My first LO is

21.7 MHz above 145.21 MHz or at 166.91 MHz.  A signal at

156.06 MHz will generate a spurious response at 21.7 MHz since

2*166.91-2*156.06=21.7 .  Thus the second harmonic of the LO

mixing with the second harmonic of the spur frequency ends up

in the IF.  Just how susceptable the receiver is to this spur

product depends upon the design of the first mixer and the

gain and linearity of the preamplifer, as well as the ability

of the input filter to reject 156.06 MHz.  Since the VHF front

end is fairly broad, the filter will do little good.

I suspect the IF frequency change in the 470 occured as a

result of spurious problems, since the IF frequency should not

affect the intermod dynamic range.  In fact, another ham in

the area brought his 470 over and we checked it for its

intermod performance and it was identical to mine, however his

had the original 17.3 MHz VHF IF.  Thus I guess my performance

is typical.  From email I have received since my original

posting, it appears that this type of performance is typical

for dual band radios made by all of the major manufacturers.

Attributed:Jim Summers, KD7F


Finding the IF:

The Yaesu intermod fix changes both the first IF and second LO

frequencies.  The following changes are made:


RF Unit - XF200117N15AU 21R15AU

        - XF200245N15A1 47M15AU

        - L2007 4.7uH 3.3uH

        - L2008 4.7uH 3.3uH

IF Unit - X3001 16.845MHz21.245MHz

        - X3002 44.615MHz47.265MHz

IF Frequency 17.3MHz 21.7MHz

Second LO 16.845MHz21.245MHz

You can hear the second LO frequency with a general coverage

receiver in SSB mode.  As suggested by Al Rabassa, wrap the

FT-470 with several turns of insulated wire and connect the

wire to the antenna connector of the GC receiver.  The 2nd LO

frequency should be received.

You can also hear the first LO with a scanner.  The first LO

will be at a frequency equal to the FT-470's displayed

frequency plus the IF frequency.

Another way to tell is to hook up a spectrum analyzer to the

antenna input (Be careful not to transmit!!!) and look at the

first LO leakage.  It is very easy to see on my radio (about

-50 dBm).  The first LO will be offset from the receive

frequency by the first IF frequency.  At 144 MHz the LO will

be at 165.7 MHz.  For receive frequencies above 157 MHz, low

side injection is used.

Attributed:Jim Summers, KD7F


Opening Battery Cases:

I`ve opened several FNB-x cases in order to replace the cell

pack.  The procedure that I've used is very simple, but does

require patience to prevent damage to the case:

1.  Cut the white label with a sharp knife by following the

    case separation line. DO NOT remove the nut on the

    charging connector.

2.  Pry the case halves apart by placing a thin wide bladed

    screwdriver into the case line on the label end.

    It may be necessary to separate the black band from

    one case half with a knife tip when it is evident that

    glue has penetrated the joint.  NOTE:The black band is

    permanently attached to one case half.

3.  Use continuous pressure, not excessive force, to separate

    the case halves.  Concentrate the separation procedure on

    the label end of the case.  The steady pressure will allow

    the glue to cold flow and release its grip.

4.  Yes, a frustration level will occur, but then success will

    appear as the glue gives up after a few minutes.

5.  Make a note of where the wires attach to the battery and

    thermal switch.  Also note the pack orientation.

6.  Connect the replacement pack into the case and attach the

    wires per your note in step 5.

7.  Close the pack, charge the cells, attach to the radio for

    a test.

8.  If satisfied, place a spot (1/2 inch dia) of clear RTV on

    each side of the cell pack and press the case together and

    place it under a weight for a short time until the RTV

    cures.  Because of the reduced amount of glue, the case

    will have a more flimsy feel than previous to replacement,

    but will perform like the original.

9.  For the next replacement, the RTV will give up much easier

    than the original glue.

Attributed:Hugh Wells, W6WTU


UHF Transmit Extend:

Since I always get about a dozen requests for ANY information

on extended UHF transmit, I'll try to head them off by saying

that I have NEVER heard of one.  Rest assured that I will add

any such mod to this list and IMMEDIATELY repost it!



end of Rev D mod list...




Randall Rhea                                        Informix Software, Inc.

Project Manager, MIS Sales/Marketing Systems    uunet!pyramid!infmx!randall

SOURCE: The QRZ Windows Ham Radio CDROM

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