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IC-T7H Mods
Expand
frequncy
Disassembly instructions for IC-T7H
Transmitting AM with IC-T7H
Notice: We can not guarantee specification when expand frequency.
How to expand RX frequency
How to expand RX/TX frequency.
| Subject: T7H Mod
User comment |
After I performed the
mod (Hold Band and Moni keys down then turn power on) and it have me
TX and RX on the following bands:
50-199
300-399.9
400-500.9
600-999.9
I can Receve and Transmit on all of the above frequencies.
Cheers,
Jonathon
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| Subject: TX/RX
Expanding Mod
User comment |
| I just did the mod. It
is easier if you just lift one side of the diode and not remove the
whole thing. It still works. I now have RX and TX on the normaly
covered freq of the radio. 400-470 and 118-174. It does not RX or TX
on the freq's listed by "Jonathan" in his post. Just open the radio
(do not remove the board the diode is on) and use a pair of tweezers
to hold the diode. Then briefly touch your soldering iron to the
single leg of the diode and pull up with the tweezers. Repeat until
the leg is free from the board. Reassemble. Hold down MONI and BAND
and turn on the radio. RX/TX across the board. Enjoy. |
| Subject:
Experiences with this mod
User comment |
Two comments about this
mod:
a) RX works fine on 118-174, 400-470. The list Jonathan posted above
is nonsense; this radio does not cover those ranges.
b) TX also seems to be enabled for the entire range, but be careful!
The aircraft band is AM, *not* FM. This radio has an AM receiver,
but without further modifications, it transmits FM only.
Transmitting FM on the aircraft bands is a BAD idea. (Transmitting
anything on the aircraft bands is probably a bad idea, for that
matter.)
73 de KG4RUO
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Disassembly instructions for
IC-T7H |
Disassembling Panels
- Unscrew 4 screws, A from the rear
panel and 2 screws, B from the rear plate to separaye fron and
rear panels.
- Unscrfew 4 screws, C from the rear
plate to remove it.
Removing logic unit
- Unscrew 4 screws, D from the LOGIC
Unit.
- Unsolder jumper wires from the speaker as
shown below.
Removing 2F unit
- Unscrew 1 screws, E from the 2F Unit.
- Unsolder the point, F, then remove
the 2F unit with the contact base.
(Disconnect J1 on reverse side of the 2F unit to remove).
Removing 1F unit
- Pull the 2 knobs off and then unscrew the
unit.
- Unscrew 3 screws, G and 2 screws.
H from the 1F unit.
- Unsolder 2 points, J then remove the
1F unit.
Under the
new modle ic-t7h the 2 (2pin) diodes
that
replace the (3pin diode) get removed for
tx open.
David kc2dmc -works fine...
| Subject: mod
works fine
User comment |
my ic-t7h works fine
with the mod.. covers these freq's :
50-199
300-399.9
400-500.9
600-999.9
also my version is the E. i think that answers someones question
about that ..
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Transmitting AM with IC-T7H |
Presuming all mods for opening RX and TX
are made:
- Disassemble front and back as in the
disassembly instruction on this page.
- Dissassemble 2F unit from 1F unit. Unsolder
the ground clips as indicated.
- After opening srews unplug the 2F unit from
1F unit.
- Locate Pin 6 of PA board. This pin feeds the
gate voltage to the final. AF on this pin causes am on the tx signal.
- Solder a thin insulated wire (best wire
wrap) to this pin.
- Run the wire up to the volume/chanel knob.
- Replug 2F unit to 1F unit. Resolder and
fasten screw.
- Solder 10 uF /10V Tantalum as indicated on
Photo +side to the wire.
- Run thin wire from - to R310/315. This
connects directly to TX AF.
- Solder 1M2 resistor from whiper contacts of
R313/316 to ground.
This changes power dependant of supply voltage.
Alignment:
Now your trx should tx with abt. 450 mW AM at 5
Volts and 1 W AM at 10 Volts. Switching between AM and FM is done via
power: low means AM, high means FM. In FM the residual AM is abt. 5 to
10 percent, which makes no degradation in a FM receiver due to limiting
stages. The residual FM in AM mode only broadens the signal a little
bit.
To remove residual FM, a diode can be connected
from the H/L (Q305) line to the connection of R308/R310 with its
cathode. This blocks FM on low power. In trials with commercial am trx
this was not found necessary.
Good AM can only be achieved with an ample
matched antenna. A good solution is a 50 cm stiff steel wire (the inside
of a bike brake) directly attached to a BNC plug, and covered with a
shrink tube.
This antenna works well from 118 to 160 Mc and
420 to 450 Mc for transmitting.
The IC-T7H always opens the squelch in AM. To
get rid of that I found only one solution:
- Change R200 on logic board to 47K, unsolder
Pin7 of IC15 from board. Carefully bend Pin up a little, and run a
thin wire to R200 (not to the ground side).
- Now switch lock to lock. Turn on Radio.
Clear appears, then 0000. Switch lock open.
- Press MONI and adjust Squelch to AT (the
others close it completely!).
- Press MR, or enter frequency.
The trick is, that by closing lock the EEprom
is disabled, and the cpu can be cheated. The memories behave a little
strange, all memories can now be switched no matter of content.
Switching on unlocked resets this situation
again. Lock still works as before.
Donīt tx in aircraft band if you are not
allowed to!
Remember it is Illegal to transmit out
of band. This Modification is for Informational purposes ONLY.
Doing such modifications on your radio may void any warranty and damage
your equipment.
All mods found on this database are offered to me by other amateur radio
hams or captured by Packet system.
KB2LJJ take no responsibility or liability for any damage done
resulting from any modification.
ATTENTION
The KB2LJJ takes no responsibility for any damage during the modification or for
any wrong information made on this modification.
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