I recently purchased a Go Devil 54 from Madcow rocketry. It comes with a black filament-wound 5:1 von Karman nosecone
The question arose, “What is the RF attenuation of the nosecone?”. The black color is produced by additives which can sometimes include carbon and other products that make the composite more “RF translucent”, rather than transparent like the uncolored mix.
I have an RF Beacon (25mW, 433.9MHz) that RocketStar made up a while back, and used that as the signal source:
So I took the parts to work and put them in the EMC test chamber. The results on the Spectrum Analyser showed a 1dB attenuation when the NC was added around the TX.
Keep in mind that this result is for the Madcow 54mm black f/w f/g NC only, tested at 433.9MHz, with a sample size of n=1. Other black NC’s or frequencies I can’t comment on with authority!
Some Perspectives on 1dB
- Decibels are on a logarithmic scale. Usually peoples' brains don't instinctively handle logs well. In human terms your ear will barely be able to tell if something is 1dB louder or softer. 3dB is double or half volume.
The effect of 1dB actually depends on how much signal level you have to spare in your system, which includes things like antenna gain, feedline losses, noise margin on the Rx, humidity, etc...
The same loss would possibly be achieved by two or three connectors in the antenna feedlines (Tx or Rx).
25% more Tx power will negate 1dB of loss.
As a system example, my TeleMega system at 21k' currently has a remaining margin of about 5-6dB. 1dB will not affect the link. If I want more range, I can build an antenna with more gain.
1dB higher signal is usually not worth worrying about
2dB higher signal is worth having if you can get it
3dB higher signal is definitely worth the effort to get
I will be fitting the TeleMega to my black NC and not losing any sleep over it