ICOM IC-22S: modify VCO for 144 MHz operation?
 

Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz. I
already made the 10 KHz step modification, and now I need to make it cover
the lower part of the band, and this is where I get a problem:

If I set binary code "0" on diode matrix, I should get 144.390 MHz exactly,
but the VCO doesn't work at this low frequency (even if indector vco is
re-tuned). I see 2 possibilities:

1- Change X2 crystal 44.56333 MHz for a lower crystal. For exemple, a
44.250 MHz would make the rig start at 143.450 MHz, and binary code "94"
would generate 144.390 APRS frequency. Any crystal between 44.0 & 44.5 MHz
would be fine. Where could I find such a crystal? (Digi-Key has nothing
around 44.0 to 44.5 MHz Xtals)

2- Modify VCO circuit to make it work lower (changing D3 varicap, C40 or L7
probably?). Did someone try this before?

Thank you in advance.

-------------------------------------------
Daniel VE2BAP
Montréal (Roxboro), Québec, Canada

I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz.
I already made the 10 KHz step modification, and now I need to make
it cover the lower part of the band, and this is where I get a
problem:


I "dimly" recall the changing of that crystal as being one possibility
for moving that rig down, but geez, that's a pretty dated radio. I can't
really offer any other help, but wanted to know if you were interested in a
nice clean factory instruction manual on that radio?


Ed WB6SAT

I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz.
I already made the 10 KHz step modification, and now I need to make
it cover the lower part of the band, and this is where I get a
problem:


I "dimly" recall the changing of that crystal as being one possibility
for moving that rig down, but geez, that's a pretty dated radio. I can't
really offer any other help, but wanted to know if you were interested in a
nice clean factory instruction manual on that radio?


Ed WB6SAT

Hi, if this is a labor of love, or you just want to tinker to make it work with
this radio I understand. Been there myself, but you can get a good used radio
for not that much cash that covers 144-147.995MHz. And those "newer" radios
will put out around 25 to 45 watts. Example: Kenwood TR-7930/ 7950, TR-7400,
Yaesu Memorizer, FT-227R, Icom IC-27H, etc...
Good luck with your project.
73
====================
tirebouchon69 wrote:

Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz. I
already made the 10 KHz step modification, and now I need to make it cover
the lower part of the band, and this is where I get a problem:

If I set binary code "0" on diode matrix, I should get 144.390 MHz exactly,
but the VCO doesn't work at this low frequency (even if indector vco is
re-tuned). I see 2 possibilities:

1- Change X2 crystal 44.56333 MHz for a lower crystal. For exemple, a
44.250 MHz would make the rig start at 143.450 MHz, and binary code "94"
would generate 144.390 APRS frequency. Any crystal between 44.0 & 44.5 MHz
would be fine. Where could I find such a crystal? (Digi-Key has nothing
around 44.0 to 44.5 MHz Xtals)

2- Modify VCO circuit to make it work lower (changing D3 varicap, C40 or L7
probably?). Did someone try this before?

Thank you in advance.

-------------------------------------------
Daniel VE2BAP
Montréal (Roxboro), Québec, Canada

Hi, if this is a labor of love, or you just want to tinker to make it work with
this radio I understand. Been there myself, but you can get a good used radio
for not that much cash that covers 144-147.995MHz. And those "newer" radios
will put out around 25 to 45 watts. Example: Kenwood TR-7930/ 7950, TR-7400,
Yaesu Memorizer, FT-227R, Icom IC-27H, etc...
Good luck with your project.
73
====================
tirebouchon69 wrote:

Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz. I
already made the 10 KHz step modification, and now I need to make it cover
the lower part of the band, and this is where I get a problem:

If I set binary code "0" on diode matrix, I should get 144.390 MHz exactly,
but the VCO doesn't work at this low frequency (even if indector vco is
re-tuned). I see 2 possibilities:

1- Change X2 crystal 44.56333 MHz for a lower crystal. For exemple, a
44.250 MHz would make the rig start at 143.450 MHz, and binary code "94"
would generate 144.390 APRS frequency. Any crystal between 44.0 & 44.5 MHz
would be fine. Where could I find such a crystal? (Digi-Key has nothing
around 44.0 to 44.5 MHz Xtals)

2- Modify VCO circuit to make it work lower (changing D3 varicap, C40 or L7
probably?). Did someone try this before?

Thank you in advance.

-------------------------------------------
Daniel VE2BAP
Montréal (Roxboro), Québec, Canada

tirebouchon69 wrote:
Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz. I
already made the 10 KHz step modification, and now I need to make it cover
the lower part of the band, and this is where I get a problem:

If I set binary code "0" on diode matrix, I should get 144.390 MHz exactly,
but the VCO doesn't work at this low frequency (even if indector vco is
re-tuned). I see 2 possibilities:

1- Change X2 crystal 44.56333 MHz for a lower crystal. For exemple, a
44.250 MHz would make the rig start at 143.450 MHz, and binary code "94"
would generate 144.390 APRS frequency. Any crystal between 44.0 & 44.5 MHz
would be fine. Where could I find such a crystal? (Digi-Key has nothing
around 44.0 to 44.5 MHz Xtals)

2- Modify VCO circuit to make it work lower (changing D3 varicap, C40 or L7
probably?). Did someone try this before?

Thank you in advance.

-------------------------------------------
Daniel VE2BAP
Montréal (Roxboro), Québec, Canada




It's been a while, but I'm sure I didn't change any xtals.
mike


--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
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Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

tirebouchon69 wrote:
Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz. I
already made the 10 KHz step modification, and now I need to make it cover
the lower part of the band, and this is where I get a problem:

If I set binary code "0" on diode matrix, I should get 144.390 MHz exactly,
but the VCO doesn't work at this low frequency (even if indector vco is
re-tuned). I see 2 possibilities:

1- Change X2 crystal 44.56333 MHz for a lower crystal. For exemple, a
44.250 MHz would make the rig start at 143.450 MHz, and binary code "94"
would generate 144.390 APRS frequency. Any crystal between 44.0 & 44.5 MHz
would be fine. Where could I find such a crystal? (Digi-Key has nothing
around 44.0 to 44.5 MHz Xtals)

2- Modify VCO circuit to make it work lower (changing D3 varicap, C40 or L7
probably?). Did someone try this before?

Thank you in advance.

-------------------------------------------
Daniel VE2BAP
Montréal (Roxboro), Québec, Canada




It's been a while, but I'm sure I didn't change any xtals.
mike


--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

IIRC I was able to move mine down by retuning coil in the VCO. Of course
the rig lost vco lock a few weeks later and never worked again .... a common
problem I was told )c:
73, K3DWW

"tirebouchon69" wrote in message
...
Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz.
......

IIRC I was able to move mine down by retuning coil in the VCO. Of course
the rig lost vco lock a few weeks later and never worked again .... a common
problem I was told )c:
73, K3DWW

"tirebouchon69" wrote in message
...
Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz.
......

Hi folks,
I finally decided to change X2 crystal (normally 44.563333 MHz). I found a
company that sells the appropriate crystal:
http://www.surplussales.com
They are located in Nebraska and sell on line. They have 44.083333 and
44.125 MHz crystals, both suitable for 144.390 MHz modification (after step
modification with X1, of course). Each crystal is $ 4.00 US.

Hope this could help.

Daniel VE2BAP


"tirebouchon69" wrote in message
...
Hi,
I want to modify an old ICOM IC-22s vhf radio for APRS at 144.390 MHz. I
already made the 10 KHz step modification, and now I need to make it cover
the lower part of the band, and this is where I get a problem:

If I set binary code "0" on diode matrix, I should get 144.390 MHz
exactly,
but the VCO doesn't work at this low frequency (even if indector vco is
re-tuned). I see 2 possibilities:

1- Change X2 crystal 44.56333 MHz for a lower crystal. For exemple, a
44.250 MHz would make the rig start at 143.450 MHz, and binary code "94"
would generate 144.390 APRS frequency. Any crystal between 44.0 & 44.5
MHz
would be fine. Where could I find such a crystal? (Digi-Key has nothing
around 44.0 to 44.5 MHz Xtals)