I recently noticed a fundamental design issue with the Tascam DR40. When using the internal microphones the DR40 is extremely susceptible to mobile cell phone interference. Even at distances of 5ft as illustrated in this video, where as the Zoom H4n and Zoom H1 + Lav which do not suffer from this issue.

This is really unfortunate as it's a great unit with some amazing features, however it's susceptibly to mobile cell phone interference makes it useless. This is the 2nd Tascam DR40 I have tested from different retailers and both have the same issue. Would have been nice if Tascam could have put better screening/shielding and filters on the internal microphone signal path.

First 2 minutes of this video detail the setup used to illustrate the issue. You can here the Tascam DR40 at 2:03, next the Zoom H4n at 2:39 and finally a Zoom H1 with a Lav at 3:15. Notice the Tascam audio has an unacceptable level of mobile cell interference.

Mobile cell used for this instance was an iPhone 5, on GiffGaff network which is O2 UK. Typically in the UK this is 900MHz, 1800MHz and 2100MHz bands for 2G/3G services.

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