Re: [baa-rag] 19:00 UTC 20:00 BST: Inaugural BAA Meteor Detection meeting

[A. C.]

 In our discussion today regarding the use in N.A. of DTV station signals for meteor scatter illumination, in lieu of the lack of similar signals as the French GRAVES or the BAA 6M beacon network, this is the difficulty of what we are faced with here for available signals and also with the very relatively few TV stations transmitting in the desirable lower VHF range CHs 2~6 or so rather than the preferred UHF channels..

 

Details from Copilot query; 

ATSC 8‑VSB inserts a small DC offset into the constellation so that a continuous wave (CW) pilot appears 310 kHz above the lower band edge.The standard specifies the pilot amplitude as:

  Pilot amplitude=1/12 of the total VSB carrier amplitude  

But because the pilot is a single unmodulated tone, while the rest of the signal is spread across the 6 MHz channel, its power contribution is tiny..

  Converting amplitude ratio → power ratio: (1/12)^2 ~ .0069 ~ 0.7%

 But the standard normalizes differently, and the actual transmitted pilot power is 0.3% of total RF power.  

  Only a very small fraction — roughly 1–2% of all U.S. full‑power DTV stations — broadcast on VHF‑Low (channels 2–6).

VHF‑Low is widely documented as rare because digital signals perform poorly there (noise, interference, long wavelengths).

Most stations that were analog VHF‑Low moved to UHF or VHF‑High during the digital transition.

 Typically there are only 20–30 full‑power stations out of ~1760 total full‑power DTV stations transmitting in the VHF low channels.

Adrian

On Sun, Jun 28, 2026 at 12:37 AM Andrew Thornett via groups.io <andrew=thorne...@groups.io> wrote:

 

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Adrian

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