Re: DCC occupancy detections false positives

On 5/17/2008 4:46 PM Charles Davis spake thus:

David Nebenzahl wrote:
>
On 5/17/2008 2:16 PM Charles Davis spake thus:

Charles Davis wrote:

The available DCC signal, can be loaded (some current drawn) by either capacitance or resistance.
Capacitance can be as simple as the two wires paralleling each other over a long distance.

This is so unlikely (capacitive loading from just the 2 rails) as to be outside the realm of possibility.

If you had a pair of insulated wires tightly twisted together for a long run, you *might* start to see some effects due to capacitive loading, but even this is unlikely.

Not that UNLIKELY at the frequencies (& harmonics) generated by a DCC signal. Remember, they TRY for a 'Square Wave' with DCC. You can't look at things as if you were working with Analog Sine-Wave RF, and draw conclusions based on that universe.

When I typed the above ----
">> Capacitance can be as simple as the two wires paralleling each other
>> over a long distance."
I wasn't thinking of a 10' run to a close block. more on the order of exceeding 75'.

Sorry, TYPING IN ALL CAPS still doesn't make it any more correct. Even taking harmonics into account, a DCC signal is still well down in the kilohertz region, nowhere near radio frequencies. Capacitance effects, if any, are negligible.


--
The best argument against democracy is a five-minute
conversation with the average voter.

- Attributed to Winston Churchill
.

Relevant Pages

  • Re: DCC occupancy detections false positives
    ... can be loaded by either capacitance or resistance. ... Capacitance can be as simple as the two wires paralleling each other over a long distance. ... Even taking harmonics into account, a DCC signal is still well down in the kilohertz region, nowhere near radio frequencies. ... Since freqquency is the reciprocal of bandwidth, that means the the highest frequency in a DCC signal *should* be about 10 kHz. ...
    (rec.models.railroad)
  • Re: DCC occupancy detections false positives
    ... can be loaded by either capacitance or resistance. ... Capacitance can be as simple as the two wires paralleling each other over a long distance. ... If you had a pair of insulated wires tightly twisted together for a long run, you *might* start to see some effects due to capacitive loading, but even this is unlikely. ...
    (rec.models.railroad)
  • Re: DCC occupancy detections false positives
    ... can be loaded by either capacitance or resistance. ... Even taking harmonics into account, a DCC signal is still well down in the kilohertz region, nowhere near radio frequencies. ... the fact of the 'Square Wave' signal wave form generates all sorts of higher frequency harmonics. ... Since freqquency is the reciprocal of bandwidth, that means the the highest frequency in a DCC signal *should* be about 10 kHz. ...
    (rec.models.railroad)
  • Re: DCC occupancy detections false positives
    ... can be loaded by either capacitance or resistance. ... If you had a pair of insulated wires tightly twisted together for a long run, you *might* start to see some effects due to capacitive loading, but even this is unlikely. ... Even taking harmonics into account, a DCC signal is still well down in the kilohertz region, nowhere near radio frequencies. ... the fact of the 'Square Wave' signal wave form generates all sorts of higher frequency harmonics. ...
    (rec.models.railroad)