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ctx
10-03-2006, 14:47
Good day to all,

Looking at all the chat on DRM .. I'm not finding anything for Icom 706's or AOR AR3000a's ... Both are widely used ..

Also what about ability to transmit in DRM .. say with a Icom 706 .. Anyone tried building a add on for this rig ..

Any help ..??

Thanks

ctx

Aetheradio
07-01-2013, 03:15
The Icom 706 can interface for DReaM by 2 methods.

Easy way but technically compromised, is to install a capacitor approx. 100pF on the pins for the optional filter installation. Then it is a matter of doing the initial set menu to specify that an optional filter is installed.
When in ssb or RTTY mode, with option filter selected, the audio output is wideband (sufficient for 10 kHz DRM) and can be supplied directly to PC soundcard. There is a steep slope on this audio, both aux and headphone output,, but DRM software has no problem.
Using this method, there is no rejection of the unwanted ssb spectrum, therefore it does not work well with adjacent frequency transmissions present.

The method I now use, with excellent results, take a connection from the FM 455 kHz filter output pin, via a 473 (.047) cap. I ran the coax to the rear panel RTTY socket and cut the RTTY lines for this mod. looking from top, down onto the filter, near the front panel (facing downwards) the connection is the rightmost of the 3 pins. This pin goes to IC18 -5 on main board.

This signal requires use of an external 455 kHz convertor board, and only operates when the IC706 is selected to FM mode.

A comparison of the modified rx I have carried out, DRM from REE Noblejas 9780 kHz

IC706 455kHz IF tap 19.2dB
ICF7000 DSP IF direct tap 18.9dB
SONY SW1 455kHz IF tap 14.9dB (from the instructions on this site)
IC R100 455kHz IF tap 13.8dB
IC706 ssb w/b filter direct 12.5dB
Sony VX20S 455kHz IF tap 10.5dB

Ralph