AT&T U-verse Observations

I got AT&T U-verse installed on 12/3/09, with 2 TVs and 2 PCs connected. Because of an older analog modem in my monitored home alarm system, I declined the U-voice VoIP portion of the service bundle, keeping the voice phone service on its existing arrangement. The alarm company's solution for using VoIP is to avoid it by using a cellular data connection. This would have involved an equipment upgrade of about $150 plus an $8 increase in the monthly alarm monitoring fee.

Click here to access a captioned photo set showing the U-verse equipment and a few selected (standard definition) TV screen photos.


I captured some connection data from the 2Wire 3800HGV-B which serves as a residential gateway for the three U-verse services. Here is a portion of the DSL Connection Detail screen:

A speed test from one of the PCs gave the results shown below. Since I ordered the same Internet speed bracket that I was previously using on ADSL, the download speed is limited to 3 Mb/s max. The upload speed is significantly better than what I had on ADSL.

This morning I tested for VDSL noise impacts on amateur radio reception. I noted a high level of white noise near the top of the 75 m band, but nothing noticeable on 40 m. I powered off the gateway and observed that the noise on 75 m disappeared. Next I unplugged all devices that connected to the LAN side of the gateway and powered it up. The white noise returned on 75 m at the following levels:

• 3.9 - 4.0 MHz -- S9
• 3.85 to about 3.9 MHz -- S6
• 3.80 to about 3.85 MHz -- S4
• 3.75 MHz -- below S2

Since no LAN cables were connected, I concluded that the noise pickup is via the 75 m leg of my fan dipole that crosses about 6' above the aerial drop wire at about a 30º angle. The 40 m leg of the dipole does not pass near the aerial drop. Rearranging the 75 m leg would probably reduce the interference.

Update 12/9/09: This morning I see only S2 noise floor on 75 m. I'll need to check this on multiple days, cycling power to the gateway, to be sure about the noise origin.

Update 12/11/09: Additional testing on multiple days failed to confirm a correlation between presence of white noise on 75 m and the state of my gateway. Generally the white noise is very low or absent in early morning and late afternoon or night, but seems to rise mid-morning thru mid-afternoon.

In the past I experienced occasional interference to my ADSL connection when transmitting on 75 m. This was later resolved when the drop wire and inside wiring connections were cleaned and reterminated at the network interface. There was no recurrence of this problem to ADSL, or to VDSL while transmitting around 3.74 MHz. However, transmitting on 3.97 MHz caused the VDSL gateway to loose sync. This condition is probably related to the proximity of antenna and aerial drop as discussed above.

I need to do more (online) reading as I explore the service performance and impacts further. Some resources are:

• U-talk Peer-to-Peer Forums
• DSL Reports U-verse Forum 
• eHam.net forum
• QRZ.COM forum 
• ARRL TIS - Possible Impact of VDSL on Stations Operating in the Amateur Radio Service
  

JK

Frequency Analysis of W4BXI Keying

Here are two views of the audio recording of W4BXI's keying. (Click on the image to magnify.) The first shows amplitude vs frequency for a portion of the initial dit. A fairly sharp peak is seen near 622 Hz. The amplitude above the peak rolls off more slowly than I expected, and this shape is also seen when I analyze just the noise waveform between CW characters. It might relate to the audio filter mode or some other noise entering the recording.



The second figure shows the amplitude and frequency content vs time as in the previous post for the recording of keying from KB4XX. Except for some brief additional high-frequency content near the beginning and end of each CW character, the tone is steady for the duration of each character.

Many, many other views can be obtained by choosing the time portion of a waveform to be analyzed.

-- John

Key chirp -- another view

I selected another view in the Cool Edit 2000 program to help illustrate what the ear easily tells us about chirp in the CW sample from KB4XX. Above is a spectral view showing the initial dah and the following dit sent in the semi-break-in mode. Click on the image to magnify.

This graph plots frequency on the vertical axis, in a limited set of discrete bands, and time on the horizontal axis. Intensity is represented by color, with light colors on the high end of the range, and dark colors on the low end. A steady tone is seen by the solid horizontal bar in the 700 - 1000 Hz range for most of the dah and the dit. The early part of the initial dah shows instability represented by the bright spots above and below the 700 - 1000 Hz band.

Next I'll post corresponding views of the keying sample from W4BXI. All analysis views are based on the audio waveforms recorded from W4UOA's receiver.

-- John