Propagation... why do I miss some signals?
#12
There are some 'Hidden' "Gotchas"  that may result in 'missed signals'... when looking at your stats..

The 'trigger' threshold level must be at least twice your noise level... any triggered channel signal failing that will be ignored by the server.  That sometimes may change, but most of the time the baseline is 'twice the noise level'. The 'best' channel for any given station, for any given impulse, will be selected, and compared with others, beginning with the timestamp and trigger point... (TOA) then such tricky things as 'Zero Crossings' i, etc...(TOGA)

Both H channels and E channels have KNOWN inherent time delays.  Each Filter setting has KNOWN time delays.  Each antennas type has expected or computed time delays.... This is why it is extremely important to configure your station properly on your owner's page on BT... especially as regards antenna type, and dimensions.

as an example,
We are going to use the RED's E channels to illustrate delays, because they're much more obvious than H channel Antenna differences... :
Here would be the KNOWN and EXPECTED time delays and frequency responses of a System RED which has three E channels available:
Filters:
     The coax and it's shielding is effectively part of a High Pass filter network  >5 KHz System RED)
(preamp, coax, amp combined) (This is also true for system BLUE expect ± 8 KHz )
These numbers are specific to RED, but basic principle is similar for Blue:    
First stage HP filter is in Pre-Amp, third stage in amp.
     50,100,150,200,250 Hz is effectively attenuated
     Similar with 60Hz and harmonics
This is specific to RED channel design:
18 KHz cutoff
44 KHz cutoff
>50 KHz
± effective channel selectivity
A =    5KHz ±  ——  23KHz ±
B =  18KHz ±  ——  44KHz ±
C =    5KHz ±  —— > 50KHz ±

Again the below is a RED's  E channels signal.
[Image: REDEChannelExpecteddelays.png]

On E channels, the 'Probe delay' is virtually 'zero', but the surface area of the probe (from dimensions) affects both the 'type of charge' content, it's amplitude, and the 'capacitance' value of the 'circuit'... In effect, a primary component of the above mentioned 'high pass' filter. Therefore it's 'response'  can affect both BW and delay, especially in the TOGA chain computations. The Server Knows this 'designed' delay, for each selected channel, and that is factored into the 'TOA and TOGA computations. 
The exact same thing is true for BLUE, except there is only ONE wide band E channel with optional filtering variations....  The delays in the designed and optional filter settings are KNOWN by the server. And computed 'surface area' of the probe can be factored in if the station's configuration data is correct

APPLY SIMILAR LOGIC to H channels on either system, RED or BLUE... but equate the E Channels Above to different antenna types and construction, That info must be entered correctly in your station configuration,... otherwise you may 'miss out' on best effectivity and efficiency.

example: Here are two identical FERRITE core antennas... with one difference: the faster response has an experimental core wrap modification... Rolleyes  (which I now use as my 'standard' H antenna, in two build designs.)
[Image: csstSigTimeDif.png]
A 2 to 4 Microsecond time difference can refine a 'deviation' error by 0.5 to 1.2 kilometers!
(600-1200 meters)


So ensure your station antenna and probe configurations are correct... Yes, the 'dimensions' should be metric.
System BLUE.. and tick the  shielded, or transformer boxes as appropriate. E SHOULD HAVE NO Ticks.. Tongue
[Image: AntennConfigBlue.png]
0-2 are for H field antennas
The server and the rest of us Rolleyes  would expect HA=0, HB=1
If using HC = 2, if not, undefined, skip it...
E Field ALWAYS begins at 3 regardless of system - undefined if NO E connected
4,5 ALWAYS undefined for BLUE's single channel.  Red has 3 channels which should be defined if E is utilized.

Stations: 689, 791, 1439
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RE: Propagation... why do I miss some signals? - by cutty - 2018-11-07, 16:43



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