I do have rather a small uptake at the minute, about a month ago there was around 20 connected since the cab had been installed in September.
Hopefully not, but maybe a case of enjoy it while you can :-)
Since the install I have noticed lower SNRM at night. Normally goes down to 4.3/4 but it started hitting 3 some nights now since this install but could just be a coincidence...
Lower SNR at night is normally due to greater interference from electrical lighting circuits, especially 'noisy' street lighting.
Various images attached now, including the RF filter.
Is that the RF filter they removed? Or the one that's still in situ? If so, that's an RF2 dubbed the "ADSL Killer" !
I can see from the interference profile, that you're near the Postwick MW transmitter. For example, the interference on DMT#198 is due to AM Radio Norfolk station on 855kHz (198 * 4312.5 Hz) pounding out 1500 watts :-)
That RFI is evident in the QLN graph (check the spike at DMT #198). That noise lowers the SNR for that tone and surrounding tones, and consequently, the bit loading goes down for those affected tones.
Recall each subcarrier (or "tone") has its own SNR. These SNRs are then averaged across the upstream and across the downstream bands to give us a single SNR figure for up, and a single SNR figure for down. Those average SNR figures tend to mask frequency-specific interference.
I also have various dips on the BitLoading where that tone/bit isn't being used, there is probably about 15 max. About 7/8 on DS and the same on US, none on the other (blue).
At a guess from your proximity to Postwick, many of those dips are due to RFI from that transmitter.
That transmitter also belches out Radio Five Live on 693kHz (10kW), TalkSport on 1053 (18kW), Virgin Radio on 1215kHz (1.2kW)
See:
http://www.mediumwaveradio.com/uk.phpThe spikes and troughs look ugly but they're no biggie. Each tone carries at most 15 bits, so if you lose at maximum three tones per AM radio station, you're only losing a few tens of bits in throughput. Besides what can you do about it, short of cutting the guy ropes to the antenna and lopping the wretched thing :-)
From:
http://tx.mb21.co.uk/gallery/postwick.php- - - - - - - - - - - - - - - - - Cut here (and run!) - - - - - - - - - - - - - - - - -
cheers, a