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Sensitivity

Page history last edited by David-Taylor 11 years, 2 months ago Saved with comment

Why is my FCD is deaf?

 

RF Overload

 

The original FCD was a broadband device, with little or no filtering in the front-end.  This meant that a strong signal could block out reception even for frequencies well away from the interference.  Use a filter to either notch out the one interfering signal (e.g. a quarter-wave stub), or to pass the wanted signal.  Using a broad-band antenna may exacerbate this problem - try and stick to a single-band antenna if you have this problem. Reducing the RF gain can reduce the susceptibility of the device to interference.

 

The newer FCDPP should be less of a problem, particularly in the amateur bands, as it has much better filtering built in.

 

RF Interference

 

PCs can be prolific generators of RF energy over a wide spectrum, so putting your FCD directly into the USB socket may not be the best placing.  Try an USB extension cable (3 - 5 m long) and see if that reduces the problem by placing the FCD well away from the PC.  Oh, and be sure to use a USB extension cable which works!  At least one person with a fault using a stick on an extension cable found that the fault went away when plugging the stick directly into the PC.  Do check your cables - likely they are made down top a price rather than up to a quality level!  Personally (djt) I have found Belkin cables to be reliable.

 

Low-frequency problems - Long-wave and Medium wave

 

Although the FCDPP is advertised as working down to 150 kHz, my (djt) experience is that sensitivity can be low on the medium wave band, and very low on the long-wave band.  It is not currently know whether this problem can be resolved.

 

Band conditions

 

Do be aware that on HF, the propagation conditions can vary - so you won't hear long-distance signals all the time, and you may even have difficulty with local signals.  On the VHF bands, outside the main cities you may find activity sparse especially on CW and SSB.

 

Add an Antenna!

 

This sounds terribly obvious but sticking a little piece of wire into the SMA connector just won't do.  I [Elwood Downey] used a calibrated signal source and was able to just hear a 1 uV signal at 14 MHz, so you'll need some sort of antenna to hear anything more than strong local stations.  The FCDPP is so wonderfully broadband that no one antenna will work well but a single wire about 30 feet long as high as possible should at least let you start hearing more signals.  Be sure to disconnect it when not in use to prevent damage from static discharges.

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