How Does One Improve Transmission Fidelity; Can The Ic-746 Transmit At Less Than 5 Watts; How Do I Turn On Both Hf Pre-Amps At The Same Time - Icom IC-746 Faq

8.12

How does one improve transmission fidelity?

Here is a checklist of several possible actions (not in any particular order).
• Using TCN, set the "SSB TX Tone" control to H. (SSB TX Tone affects all voice modes)
• Turn off COMP (compression).
• Use a higher quality microphone.
• Use microphone shock mountings and pop filters.
• Use external microphone equalization.
• Feed transmission audio directly via the ACC port, bypassing the microphone preamp.
(may not help the PRO as much as the CLASSIC).
• Make sure supply voltage is 13.5 V or higher.
• Lower RF output
• Adjust by monitoring signal on a second receiver.
8.13

Can the IC-746 transmit at less than 5 watts?

Yes, with the help of some external circuitry.
The IC-746 isn't really designed for QRP operation (the 2+ amp draw on receive should
prove that). The front panel control will only get you down to about 4-5 watts. However,
you can apply a voltage to the external ALC input to get even lower. 0 to -4Vdc input yields
0 to 100 Watts output. One ham even uses a simple voltage divider/pot arrangement powered
by 2 AA batteries.
K5UHF warns that there can be a minute moment of higher power output before the external
ALC level kicks in. Not normally a problem unless you're driving input sensitive equipment;
like transverters.
8.14

How do I turn on both HF pre-amps at the same time?

You can't. Nor would you really want to.
HF preamp 1 is transistor based and yields about 10db gain for the 1.8 - 54 Mhz range (160m
to 6m bands). HF preamp 2 is IC based (presumably an op-amp) and yields about 16db gain
for the 21 - 60 Mhz range (15m thru 6m bands.
In practice, each HF preamp will work on any HF band.
The sensitivity of the IC-746 is so high that neither of the HF preamps are rarely needed.
You'll need the attenuator more often than the preamps.
IC-746 FAQ
Page 95 of 113
2003-02-08