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Author Topic: Icom 740 CW filter upgrade  (Read 193 times)
VE3GNU
Member

Posts: 83




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« on: November 23, 2007, 09:56:16 AM »

Based on experience, what is the recommended CW crystal filter to replace the standard 300hz AF filter that comes supplied with the rig? An INRAD filter would be an option.
Thanks in advance---Ernie VE3GNU  
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K8WV
Member

Posts: 44


WWW

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« Reply #1 on: November 25, 2007, 08:05:35 PM »

The 740 accepts crystal filters in each of the two IF's 455 KHz and 9 MHz.

If you want to upgrade your filters, consider first what your operating style is.  If you operate casual CW, the 500 Hz filter options would be fine.  If you chase DX, or operate contests, consider the 250 Hz option.

I just finished the CQ WW CW contest and wouldn't have wanted to give up my 250 Hz filter.

Start with the 455 KHz IF, then add the 9 MHz filter.  Inrad is a fine choice.  You may also want to upgrade your SSB filter to an FL-44 (or FL-44A) or the Inrad equivalent.  None of these filters are inexpensive, but they are worth it.

Finally, after the filters, consider a good DSP audio accessory, such as Timewave.  I use the Icom/Inrad filters, then a Timewave DSP-9, then an Autek QF-1A.  I truly believe I can isolate any signal arriving at my antenna.

The 740 is a great radio. Enjoy!

73, Dan, K8WV
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