>vanishing contact at 6"

This should not happen imho. While I am not familiar with your brand of
Tx/Rx, if they are meant for data, then they will not pass DC signals. In
other words, you will have much better chances using them with a 555
oscillator set to blink a LED at 10 Hz or so than with a button.

The winking LED when no signal is present is normal for this type of
receiver (unless it has a squelch system, which most cheap modules don't).

One scheme that seems to work well to test these, is to use a pair of
encoder/decoder chips meant for infrared Tx/Rx. At the encoder connect
a low pass filter to the data output (RC with R = 10K and C = 0.01 uF will
work) and connect the resulting signal to the transmitter keying input. At
the receiver, feed the receiver output directly into the data input of the
decoder chip. This scheme allows much more realistical testing than with
buttons and things (always assuming you lack the skills to estimate BER
and other parameters of the data link).

Last, make sure that your trusted Pentium 300 MHz etc has its covers on if
it is running near your project (under the table ?). This can be a serious
source of noise and disrupt 300 and 400 MHz radio links in my experience.

hope this helps,

Peter

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