Monthly Archives: September 2015

Log: AM BCB, September 20th, more trans-Pacific reception

(7’x24′ Conti superloop pointed 320 degrees, RTL-SDR dongle with upconverter, coverage only up to around 1400kHz due to filtering)

This was an interesting morning as there was a strong geomagnetic storm overnight, although that usually doesn’t affect things this far south. The early peak just after Japanese sunset was decent with weak audio from 747 and 774 kHz already by 0913UT (2:13am MST). That continued off and on for another half-hour. The main peak before local sunrise started shortly after 12UT. I didn’t get the large number of carriers or as many frequencies with audio, but 774-JOUB (Akita, Japan, 500kW) delivered the best audio I’ve had this month.

1204UT – 747 audio being persistent and almost intelligible
This was followed by a fairly long period of only carriers
1242UT – 774 picked up a lot, and up to medium audio at 1243UT
1248UT – 774 medium audio again, a man talking
1258UT – 774 medium-good audio again, a man still talking, into the TOH 3+1 pips
1300UT – 774 a bit of a fade out, but stronger again for a bit

Here is a longish recording from 774 starting at 12:58:00UT. Just for perspective, the recording starts out before the audio became intelligible, but quickly rises up to a nice level. It fades out again after the TOH pips, but the recording continues and the signal comes back for a bit before dropping below intelligibility for good. If you don’t want to listen to the whole thing, the best audio is from about 0:30-2:00 in the file:

There were decent carriers at times on 594, 693, 828, 972, and 1053, but not much more than that.


Log: AM BCB, September 18th, strong trans-Pacific reception

(7’x24′ Conti superloop pointed 320 degrees, RTL-SDR dongle with upconverter, coverage up to around 1400kHz)

September has been quite good for trans-Pacific (TP) reception, and this was a particularly good morning. Although I never got any great audio, I had a lot of it for this location, and a plethora of carriers. The main action started after 1215UT (5:15am MST) and lasted until near local sunrise at 1314UT. Overall the best TP session out of 9 this month.

English lessons (not quite intelligible) from NHK peaking on 747 at 1232UT and on 774 peaking at 1220UT. 972-HLCA very briefly had the best signal of the morning at 1301UT. Also faint audio from 693 (including the 1300UT time pips), 828, 1053 (both the jammer and the jammed), 1116, 1134, and 1296. Another 40 9kHz frequencies with medium to strong carriers.

20-minute breakdowns:

Weak audio:
747 at 1231-1234 (English lessons)
774 at 1217-1222UT and 1226UT (English lessons; almost intelligible at 1220 through KKOB splatter)
972 at 1230-1231UT and 1234UT (very faint speech)
1053 at 1217-1218UT and 1226UT (speaking or singing?)
Strong carrier: 828, 972, 1134
Medium carrier: 594, 693, 747, 945, 954, 1044, 1089, 1116, 1143, 1323

Weak audio: 693 at 1254UT
747 at 1236UT
774 at 1243-1246UT and 1249-1253 UT (English lessons)
828 at 1252UT
972 at 1235-1237UT, 1243-1245UT, and 1254UT (music)
1053 at 1249UT and 1253UT (unsure of content)
1296 at 1254UT (unsure of content)
Strong carrier: 594, 603, 693, 1134, 1224, 1242, 1314
Medium carrier: 657, 729, 828, 873, 954, 1008, 1044, 1089, 1098, 1116, 1179, 1197, 1269, 1278, 1287, 1359, 1386, 1404, 1422

Medium audio: 972 at 1301UT (voice into music; additional weak audio at times)
Weak audio:
693 at 1300UT (heard 3+1 pips and then talking)
747 at 1255UT (very faint talking)
774 during much of the period (intermittent faint audio and last TOH pip, best at 1303)
1053 at 1259UT (jammer?)
1116 at 1259UT (brief very faint speech)
1134 at 1257-1258UT (faint female speech, then local 1130 went to full power)
Strong carrier: 594, 603, 693, 828, 1008, 1107, 1116, 1134, 1224, 1278, 1296, 1314
Medium carrier: 558, 612, 657, 666, 786, 864, 872, 893, 963, 954, 963, 1008, 1017, 1044, 1098, 1143, 1179, 1197, 1206, 1242, 1287, 1323, 1332, 1359, 1377, 1386, 1404, 1422 (the latter two even though my low pass filter for 1450/1490 is really kicking in by this point)


Log: AM BCB, September 15th, trans-Pacific reception

I’ve done SDR recordings on about half of the mornings this month with my 7’x24′ Conti superloop (corner-fed, corner terminated broadband loop), RTL-SDR dongle, and Ham It Up upconverter. This morning was the best so far, with audio from several stations, and fairly decent audio from 972 kHz out of Korea. It also exhibited a pattern I’ve been seeing where I get good Japanese reception shortly after their sunset, and another enhancement shortly before my sunrise. The latter is common, but the former has been quite noticeable this month. In the following log, I list all the 9kHz frequencies where I had at least a medium carrier within 20-minute intervals from 0935-1315UT (2:35-6:15am MST). Signals dramatically weakened around local sunrise of 1312UT (6:12am MST). My frequency coverage only went up to 1400 kHz due to filtering to remove strong locals at 1450 and 1490.

First, for the IRCA mailing list members who have already seen this log, here is the audio sample at 12:57:30UT from 972-HLCA with some splatter from 970:

And, the 20-minute log:
Weak audio: 747 and 774 around 0936-0938
Strong carriers: 594, 693
Medium carriers: 828, 1053, 1134

Strong carriers: 693, 774, 1053
Medium carriers: 594, 747, 828, 1134

Medium carriers: 594, 693, 747, 774, 828

Medium carriers: 693, 774, 828

Medium carriers: 594, 693, 774, 828, 1053

Medium carriers: 693, 774, 828, 1053

Strong carriers: 774
Medium carriers: 693, 828, 972, 1053, 1134

Weak audio: 972 from 1215-1219UT
Strong carriers: 774, 828
Medium carriers: 747, 1053, 1134

Medium audio: 972 from 1247-1250UT (other bursts of weak audio)
Weak audio: 774 at 1251UT, 828 at 1239UT
Strong carriers: 747, 972 (near audio at 1254UT)

Medium audio: 972 from 1255-1301UT, quite decent around 1258UT, mix of talking and music
Weak audio: 774 at 1258UT, 972 continuing until 1304UT
Strong carriers: 693, 1053
Medium carriers: 594, 747, 828, 864, 936, 945, 954, 963, 1008, 1044

A few lingering medium carriers after local sunset, inc. 828, 974

How-to: Aluminum case for new RTL-SDR blog brand TCXO dongle

The RTL-SDR Blog posts articles and links related to software defined radio. They also sell RTL-SDR dongles and accessories. Last month they introduced a dongle with a temperature compensated oscillator (TCXO). This virtually eliminates the well-known offset and frequency drift of “standard” dongles as they heat up or the ambient temperature changes. NooElec also makes a model like this, but if you don’t like the MCX connector on the latter, the RTL-SDR Blog version uses an SMA connector (and is a bit cheaper at the moment). Both brands are good products in my experience.

The RTL-SDR Blog does not sell an aluminum case for this dongle (yet), but once you get past your first RTL-SDR experimentations, this is a must have. A metal case shields the dongle from RF interference and provides a better ground plane. It is a fairly straightforward mod to get the RTL-SDR blog dongle to fit in the RTL-SDR case sold by NooElec.

Disclaimer: you can potentially ruin your RTL-SDR dongle, so attempt this at your own risk.

Tools needed: sandpaper, small metal file, small phillips screwdriver, power drill, hammer and hole punch (optional)

Here is a picture of a modified case and an unmodified case, plus the file I used, and the dongle removed from the plastic case it comes with:

I did not take a picture of an unmodified dongle, but you want to sand down the long edges of the PCB just enough so that it fits on the rails in the case. Normal fine grit paper works fine. Also, you can sand down the PCB that sticks out from where the USB plug is mounted. Do not sand too much or you can hit conductive traces and/or solder points.

Using the file, etch smaller slots on the short sides of the existing USB slot in the case. You might also need to file down one of the long sides of the main slot to allow the plug to vertically fit. You want to do this fairly precisely to avoid creating a large hole for RF interference to leak in, so trial and error is the best method.

On the other end cap, you will drill a 1/4″ hole for the SMA plug. Note that a commercial case might have a square hole to accommodate the lip of the plug, but that it not necessary. It just means that the USB plug will stick out a couple millimeters more than usual on the other end. Use the slot end of the case as a template to determine where to drill the hole. A hole punch can be very helpful here to mark the hole location to keep it in the same vertical plane as the rest of the dongle and USB plug.

Some people claim that the paint on the case can cause electrical problems, i.e., the case will not be a unified ground plane. So, before you put the case together, use the file or sandpaper to strategically remove paint where the case pieces fit together. This does not have to be precise.

You can fill the MCX hole in the case with a short screw and nut to prevent possible RF interference from entering here.

Here are a couple shots of the end product (a little blurry, but you get the point):


I’ve had this running for about 20 hours total since I made the mod and it works fine.