Philips FM-92-E (E-band) Conversion Mods for 6 metre Amateur band

Created 20th February 2003, last updated 14th December, 2012

Modifications to a Philips transceiver model FM-92 to convert its operation from commercial VHF low band (70-85 MHz) to 6 metre HAM band
There are several versions of the FM-92, for high Band VHF and UHF, this page primarily covers the 99 channel low Band VHF,
25 watt output ( E band, 66-88 Mhz model)
The FM-92 is part of the Philips FM-900 series, see also FM-91 and FM-93 models. It comes in E, A, T, U, W1 & W2 band versions.
This transceiver is EPROM programmable, normally a 2764 (8kbyte) EPROM.


The FM-92 is characterised as a mobile base unit, it comes into two variations, a "Local" unit, with front panel fixed to the base unit and
the "Remote" unit, which has the front, control panel connected to the main unit by a remote cable with DB-15 connectors at each end
approx 25cm L, 20cm W, 6cm D, with a diecast body with heatsink ribbing and sides and rear panel.
connectors are a 15 pin DB-15 for remote head connection, a BNC antenna socket and 13.8V DC power lead.
The remote Head and Local front panel, includes twin 7 segment displays for channel indication and several buttons for UP/DOWN channel
selection, SEND button, AUX button, POWER on/off button, plus Volume and Mute controls, Power, TX & RX indication LEDS.

I have the full set of photocopied FM-92 Service manuals.

I have now added mods for versions other than just E band

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MODIFICATIONS FOR PHILIPS FM92 E BAND (66-88MHz) TO THE AMATEUR 6 metre BAND (52-54 MHz)

For modification of the FM-92E down from 66-88 Mhz onto 52-54 Mhz amateur band requires a good deal of work, the modifications
have been documented by the Northern Corridor Radio Group Inc in Western Australia and was printed in Amateur Radio magazine
( see A.R. MAY 1997 ) and also on the NCRGI web pages (formerly found at http://www.faroc.com.au/~ncrgi ) which I have now listed below.



1.	Remove the PA board.

Rewind coils as per the attached list.

L122 & L114  If these coils are wound together with a common tap, then the list length applies. If these are Separate
coils, then the following measurements apply L122 - 31/2 turns, L114 6 1/2 turns.

General observation: All coils are 25 - 30 % more turns than originally manufactured by Philips.

Substitute Capacitors as per the attached list
NOTE: C122, 123&128 are added in parallel with existing capacitors
C127 & 144 are added in parallel beneath the board. Lay the capacitors flat.

There Is an 18k? Resistor on the right hand end, below the large coil and near the hairpin link between the choke and
another resistor. This should be replaced with a 33k resistor.

2.	 Remove the vco module.
NOTE: Ensure that all solder is removed prior to lifting the unit from the board.

Remove the side from the VCO.

The glue solder is ineffective.
Heat the VCO case to flow the solder on the hybrid board post.
Separate the board from the die cast housing.

Remove the offset frequency coil. This is the coil closest to the end of the board
NOTE: Use a sharp hobby knife or engraving tool to cut away the mounting cement from
the mounting legs.
Heat Glue for removal also.

Rewind the coil with 5 1/2 turns of the same diameter width 0.8 mm wire.
Space the coil to fit the existing hole centres
Resolder the coil to the board.
NOTE: Coat the offset coil with clear nail varnish after fitting and soldering
The offset coil slug is longer.
Ensure that both slugs move freely, Lubricate with silicon grease (Heat sink compound
will do) if necessary.
Insert 10 pF NPO Capacitors across both coils

Refit the board to the housing.
Refit the housing to the radio.
Resolder all of the connections.

3.	 Remove the front end tuning block.
NOTE: Ensure that all solder is removed from the pins prior to removal of the die cast housing.

Remove both sides of the housing. It may be necessary to heat the side panel with a soldering iron to achieve this.

Carefully remove all the coil formers (Bobbins). The coil earth is soldered to the top of the housing.
NOTE:	Do not attempt to adjust the variable capacitor (I.F. injection). Ensure that all the slugs on each coil
(inside the bobbins) are fully in before removal of the bobbins.

Lay out the bobbins in the order of removal from the block.
Remove the aluminium coil partitions to match those on the opposite side at the top.
These locate the bobbins within the housing.
Grind off excess material to leave a smooth finish.

NB:	Wind the coils in the same direction.
The coils should be finished flush with the top of the bobbin, then secure with Cellotape and coat with nail varnish
to prevent any movement.

First Receiver Coil: (Next to the aerial input)

Cut off 30 mm of 0.125 mm Enamel coated wire and solder this to the main coil (which is around 125 mm long).
Insert the start, ie the end with the soldered join, into the bobbin and wind both wires in the same direction.
Wind 1.5 turns for the stub coil, then exit the bobbin (through 35) Wind the main length to 52 turns, starting
diagonally opposite the starting turn.

Second Receiver Coil:

Construct the main and the stub as per the previous coil.
Insert the tap at the start (through the side).
Wind 1.75 turns on the stub. Note: This exits at the same point on the bobbin. Leave the
tails at least 25 mm long.
Wind the main length to 52 turns.

Third Receiver Coil:

This is a 1.5 turn tapped coil, identical to the first receiver coil.

Fourth Receiver Coil: (First band pass coil)

This is a 52 turn coil, like the previous coils (but without a stub coil), however the wire must exit the bobbin
through the side and not the top. This is due to the way it is mounted in the housing.

Fifth Receiver Coil: (Second band pass coil)

This is identical to the fourth receiver coil.

Sixth Receiver Coil:

This is a main and stub, tapped coil as per the first, second and third receiver coils. Insert the common tap in
the bobbin, wind 2 turns and then exit.

---------------------------------------------------------------------------------------------------------------------

 Northern Corridor Radio Group (NCRG) FM-92-E "Remote" 6 metre EPROM channel scheme.

File :  rm9252.txt

Channels available in 6m EPROM image file rm9252.bin for 21.4 MHz I.F. (use 10r7f52.bin for 10.7 Mhz I.F.)
-----------------------------------------------------------
E Band 66-88MHz Remote control 25KHz channel space.

Hardware Code   9502922x0000
Software Code   110000200000000

Channel	Rx	Tx	Pwr	CTCSS	Options
1	52.000	52.000	H
2	52.025	52.025	H
3	52.050	52.050	H
4	52.075	52.075	H
5	52.100	52.100	H
6	52.125	52.125	H
7	52.150	52.150	H
8	52.175	52.175	H
9	52.200	52.200	H
10	52.225	52.225	H
11	52.250	52.250	H
12	52.275	52.275	H
13	52.300	52.300	H
14	52.325	52.325	H
15	52.350	52.350	H
16	52.375	52.375	H
17	52.400	52.400	H
18	52.425	52.425	H
19	52.450	52.450	H
20	52.475	52.475	H
21	52.500	52.500	H
22	52.525	52.525	H		2
23	53.000	53.000	H
24	53.025	53.025	H		2
25	53.050	53.050	H		2
26	53.075	53.075	H		2
27	53.100	53.100	H
28	53.125	53.125	H		2
29	53.150	53.150	H
30	53.175	53.175	H
31	53.200	53.200	H
32	53.225	53.225	H		2
33	53.250	53.250	H
34	53.275	53.275	H
35	53.300	53.300	H
36	53.325	53.325	H		2
37	53.350	53.350	H
38	53.375	53.375	H
39	53.400	53.400	H
40	53.425	53.425	H		2
41	53.450	53.450	H
42	53.475	53.475	H
43	53.500	53.500	H		2
44	53.525	53.525	H		2
45	53.550	52.550	H
46	53.575	52.575	H
47	53.600	52.600	H
48	53.625	52.625	H
49	53.650	52.650	H		1
50	53.675	52.675	H
51	53.700	52.700	H		1
52	53.725	52.725	H
53	53.750	52.750	H		1
54	53.775	52.775	H
55	53.800	52.800	H		1
56	53.825	52.825	H
57	53.850	52.850	H		1
58	53.875	52.875	H
59	53.900	52.900	H		1
60	53.925	52.925	H
61	53.950	52.950	H		1
62	53.975	52.975	H

---------------------------------------------------------------------------------------------------------------------

 Northern Corridor Radio Group (NCRG) FM-92-E "Local" 6 metre EPROM channel scheme.

File :  fm9252.txt

Channels available in 6m EPROM image file fm9252.bin for 21.4 MHz I.F. (use 10l7f52.bin for 10.7 Mhz I.F.)
-----------------------------------------------------------
E Band 66-88MHz Local Control 25KHz Channel space.

Hardware Code   9502922x0000
Software Code   110000200000000

Channel	Rx	Tx	Pwr	CTCSS	Options
1	52.000	52.000	H
2	52.025	52.025	H
3	52.050	52.050	H
4	52.075	52.075	H
5	52.100	52.100	H
6	52.125	52.125	H
7	52.150	52.150	H
8	52.175	52.175	H
9	52.200	52.200	H
10	52.225	52.225	H
11	52.250	52.250	H
12	52.275	52.275	H
13	52.300	52.300	H
14	52.325	52.325	H
15	52.350	52.350	H
16	52.375	52.375	H
17	52.400	52.400	H
18	52.425	52.425	H
19	52.450	52.450	H
20	52.475	52.475	H
21	52.500	52.500	H
22	52.525	52.525	H		2
23	53.000	53.000	H
24	53.025	53.025	H		2
25	53.050	53.050	H		2
26	53.075	53.075	H		2
27	53.100	53.100	H
28	53.125	53.125	H		2
29	53.150	53.150	H
30	53.175	53.175	H
31	53.200	53.200	H
32	53.225	53.225	H		2
33	53.250	53.250	H
34	53.275	53.275	H
35	53.300	53.300	H
36	53.325	53.325	H		2
37	53.350	53.350	H
38	53.375	53.375	H
39	53.400	53.400	H
40	53.425	53.425	H		2
41	53.450	53.450	H
42	53.475	53.475	H
43	53.500	53.500	H		2
44	53.525	53.525	H		2
45	53.550	52.550	H
46	53.575	52.575	H
47	53.600	52.600	H
48	53.625	52.625	H
49	53.650	52.650	H		1
50	53.675	52.675	H
51	53.700	52.700	H		1
52	53.725	52.725	H
53	53.750	52.750	H		1
54	53.775	52.775	H
55	53.800	52.800	H		1
56	53.825	52.825	H
57	53.850	52.850	H		1
58	53.875	52.875	H
59	53.900	52.900	H		1
60	53.925	52.925	H
61	53.950	52.950	H		1
62	53.975	52.975	H

---------------------------------------------------------------------------------------------------------------------

FM92-E Receiver conversion to the Amateur 6 metre band (52-54 Mhz)

This is an alternate method for converting the receiver of the FM92-E down to 6 metre band (52-54 Mhz),
which is provided by the WIA VK1 Technical Group, see attached WORD document, which provides description
and diagrams.


  • download the VK1 Technical group FM92-E conversion to 6 metres, (MS WORD file) --------------------------------------------------------------------------------------------------------------------- FM92-E conversion to the Amateur 6 metre band (52-54 Mhz) by CCARC These are the main two documents relating to the conversion procedures developed by CCARC, very detailed with colour photos and looks to be the best approach (not that I have started yet)
  • download Part 1 CCARC FM92-E Conversion to 6 metres procedure (PDF format)
  • download Part 2 CCARC FM92-E Conversion to 6 metres procedure (PDF format) or
  • check Rod VK2DOT's site for latest updates to his documentation and EPROM files --------------------------------------------------------------------------------------------------------------------- MODIFICATIONS FOR PHILIPS FM92 A BAND (148-174MHz) TO THE AMATEUR 2 metre BAND (144-148 MHz) First :- BE GENTLE - DO NOT FORCE TUNING SLUGS - they break easily. If this happens, try removing them by unscrewing from the other end of the former. Use a PROPER plastic tuning tool or they WILL break !!! 1. check to see radio works on original frequencies (printed on label inside cover), with dummy load! Should get noise on open squelch, and 25 watts out. 2. replace EPROM. If creating a job with FM900 software, change the hardware ID number to the lower frequency range (135-148Mhz ?), otherwise it won't accept our frequencies. 3. tune VCO slugs - (2 slugs located inside a large can, nearest the side of the set. Early versions can only be adjusted from the component side, later ones from the track side as well.) Pick a mid frequency channel, tune slugs - one for VCO transmit freq., one for VCO Receive freq.. Monitor the VCO control voltage at TP201 on the receive PCB (just near the Audio amp IC with the heat sink tag). It will be stuck at maximum voltage before the adjustment. When adjusted it should come down to about 8 to10 volts. Adjust the Rx slug first, then pushing the PTT adjust the TX slug. Try to adjust both so that you get the same voltage (about 10 volts ?) when switching between RX and TX mode on a simplex channel. Check that no channels give a voltage outside the 4 - 10 volt range - they may go out of PLL lock. 4. TX should now transmit on frequency - tweak the only trimmer cap on the PA PCB for maximum power out (usually fully meshed). 5. With a weak signal source attached to antenna socket, adjust the 8 slugs in the receiver front end (in the big can located in the center of the RX PCB). Start by winding each slug in about 3 turns. Adjust for minimum noise. Local the 'S' signal level test point and adjust slugs again several times for maximum level. You may want to 'stager' tune the front end for broad band operation (tune some for a mid-high channel , some for a mid-low channel). Notes: A. Modulation on some sets is not good - very 'tinny' - too much high frequency pre-emphasis. (see fixes below) B. Scanning (push the AUX button) only works when the microphone is in it's cradle (magnet activates reed switch in mic.). C. Changing appropriate link on the synth PCB gives 12.5KHz frequency steps(but still 25Khz bandwidth) but requires appropriate EPROM. FPP/FM900 software assumes the links have been changed if you accidently enter a channel with a 12.5K step and doesn't warn you (and wont work until the link is changed ! ). --------------------------------------------------------------------------------------------------------------------- FM900 12 Digit Hardware codes A 12-Digit Product Code Is Derived From The Chart Below The Firs 4 Digits (9502) Denote Austrilia And Are Fixed. The Remaining 8 Digits of the code detail the type of Equipment And Frequency Band (center 3 Digits- Colums 5,6,7), And Optional HardWare Facilities (last 5 Digits - Colums 8 Thru 12) 1 2 3 4 9 5 0 2 5 6 7 8 9 10 11 12 Series Model Freq/Band Local/Remote Temp/Range Signaling Selcall Option Spacing Stability Hardware System -------------------------------------------------------------------------------------- 0 10 ppm STD STD STD Standard (none) No S/Call -------------------------------------------------------------------------------------- 1 5ppm CTSS CCIR Rev/Tone Xtal/Heater Enc Only Burst -------------------------------------------------------------------------------------- 2 SimPlex E CTSS ZVIE ENC/DEC -------------------------------------------------------------------------------------- 3 B Local SelCall EEA Type 1 20/25/30 No CTSS -------------------------------------------------------------------------------------- 4 A Remote CTSS ENC+ EIA Ignition 20/25/30 SelCall T1 Blanker -------------------------------------------------------------------------------------- 5 T 2.5ppm CTSS ENC/DEC I/O Exp TXCO Kit SelCall T1 No S/Call -------------------------------------------------------------------------------------- 6 U SelCall CCIR T2 Type 2 ENC Only No CTSS -------------------------------------------------------------------------------------- 7 W1 12.5 Local CTSS ENC ZVEI T2 SelCall T2 ENC Only --------------------------------------------------------------------------------------- 8 W2 12.5 Remote CTSS ENC/DEC EEA T2 SelCall T2 Enc Only --------------------------------------------------------------------------------------- 9 Mobile EIA T2 ENC Only --------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------- FM-900 noisy VCO fault Below is an extract from APCNews 16 August 2000, regarding the FM900 noisy VCO fault repair procedure... Dear Dr Fixit, I have just bought an FM900 at the local Hamfest, and when transmitting, other amateurs report low audio and a rumbling or rushing noise on my transmission, also a rumbling can be heard in Receive mode, can you please help? Answer: Well, Rumbling old chap, it seems that you have the common "Noisy VCO" found in many of the FM900 series radios. The best way to test this is to listen to a fully quieting signal in receive mode, with no modulation, then turn up the volume, and tap the main body of the radio with your knuckle, screwdriver handle or similar and listen to the received signal. You should not hear any significance sound from the speaker. If you do , it's likely that you have a noisy or microphonic VCO. This is caused by the ceramic substrate in the VCO de-laminating from the metal housing, any small vibrations cause capacitance changes within the VCO module, and so you "hear" these vibrations in the receiver as audio. On the TX side its basically the same problem, symptoms and cure. Using the same tapping technique as before, listen to your Transmitted signal without modulation, on another receiver and tap the radio as before. If you hear a loud noise on your TX signal, the TX side of the vco is also microphonic. The other sure way to check, is to measure the voltage on the VCO output control voltage pin. Whilst tapping, check to see that the voltage is stable. If it varies with the tapping, then the VCO is microphonic. The only cure is to re fix the substrate to the metal housing, either by resoldering it yourself, (good luck), or you can try this with a hot air gun if your game. By far the better option though Mr.Rumbling, is to take it to a competent technician who is experienced at these type of repairs. The result will be a wonderfully performing radio once again, which even today, is still pretty pager free, and basically bullet proof; and remember, these repairs work on all the 900 series radios, regardless of the band. (Lee VK3GK & Dr.Fixit) --------------------------------------------------------------------------------------------------------------------- Subject: Making my FM92 sound better. (transmit audio) Date: Sat Jan 18, 2003 OK, after some fiddling about I think I now have a nice (well OK at least) sounding FM92. I modelled the preamp in Electronics Workbench and ran some bode plots with and without the 4.7uF electrolytic capacitor (c3) in the mic preamp. With the electo, the preamp boosts treble and cuts base. ASCII art time... | | / | __- | _---- | / |/ +-----+------+ 100 1kHz 10kHz at 100Hz, the gain is about 8db at 1kHz, the gain is about 12db at 10kHz, the gain is about 21db the -3db point (9db gain) is at about 110Hz the +3db point (15db gain) is at about 3.6kHz This explains the 'tinny' sound Without the electro, you get a reasonably flat response with 12db gain. | | ___------ | / |/ | +-----+------+ 100 1kHz 10kHz at 100Hz, the gain is 8.7db at 1kHz, the gain is 12db at 10kHz, the gain is 12db the -3db point (9db) is at about 110Hz So to make an FM92 sound better... 1. Remove the 4.7uF electrolytic capacitor from the mic preamp. 2. adjust R365 (mic sensitivity) on the synthesiser board about 90 degrees, or until it sounds about right anticlockwise with the PCB in place, or clockwise from the component side. Good luck. 73s Mal VK2TMF ---------------------------------------------------------------------------------------------------------------


  • NOTE: only licensed Amateur Radio operators can operate this modified equipment on assigned Amateur frequencies/bands.

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