WSPR - Turning off MW Band Attenuation for 630m

About three weeks ago I decided to turn off the MW band attenuation (MF Band ATT) in the Icom IC-7300 - this is a sub menu option in the settings that is on by default (Menu > Set > Function > MF Band ATT), this adds 16 dB attenuation per the manual. Wow what a difference! I started spotting stations much further away from Australia, Hawaii, Alaska, midwest to the east coast.

I've been spotting these stations semi-individually on and off, finally got a good selection of them in one night:

• VK4YB - Roger's 630m antenna is something else.
• K9FD - on a former AM broadcast site with radials intact on an Island, dream location!
• K3MF
• K5DNL - holds the distance record for a QSO on 630m with VK4YB!
• KL7L

The antenna I'm using on receive is the ZS6BKW with no additional matching, just an HF 1:1 current choke at the bottom of the ladder line, remote ATU (bypassed) then 10ft coax drop to ground where it runs around to the other side of the house. The other RX settings I configure when running WSPR with the IC-7300 are NB and NR off, notch filter off, AGC fast set to 0.3 seconds.

Since turning off the MW band attenuation, I would start spotting the closer stations in California as soon as it got dark through until sunrise like clockwork. First I thought it was propagation changing with the D layer absorption which quickly disappears at sunset and quickly returns at sunrise.

Turns out it's more than the D layer at work, there are several strong AM broadcast stations in my area, during the daytime they are very strong and overload the receiver in the IC-7300. At night these stations lower output power and/or change their antenna pattern, this reduces signal levels at my location to a level where the receiver can cope.


Screen capture of the strong signal on 850 kHz during daytime, S meter maxed out at +60dB. There are several more at +40 to +50dB.


630m band WSPR frequency during daytime, the S meter hovers around S9 +15dB. Band scope shows the "mess" these strong AM broadcast stations create in the receiver.


630m band WSPR frequency at night, the S meter hovers around S1 when AM broadcast stations reduce power and/or switch their antenna patterns.

Note: The time displayed on the IC-7300 clock top right is UTC.


Update 04 Dec 2019:

Since switching back to using an OCFD a few days ago, I no longer have the receiver overloading issue during the day on 630m. It seems to have knocked back the signal levels from the AM broadcast stations enough but with out appearing to adversely affect the WSPR receive performance.

WSPR - 40m, ZL5A Scott Base Antarctica

WSPR pulls out another surprise.

Adam Campbell / ZL5A from Scott Base Antartica:

WSPR - 40m, 1 Watt, 16441 km

Distance wise, this is the 2nd best spot I've reported yet at 16441 km / 10216 mi, from ZS1LCD in Cape Town South Africa who was running 1 watt on 40m [7MHz]. ZS1OA remains king at 16511 km / 10259 mi on 30m [10MHz], and ZS3D is a regular in 3rd place at 16233 km / 10087 mi on 40m.

After running WSPR for about three months, I took a break from it about a week ago having built up a good feel for what I can expect with the current antenna configuration. Last night I had it running again after adding a 20 ft horizontal wire to the top of the 43 ft vertical turning it into a 1/4 wave inverted L on 80m.

With the exception of 60m, Remote ATU has no problem finding 1:1 match 80 thru 10m, 40m was the surprise since the antenna is close to a 1/2 wave. Hard to know with out an antenna analyzer to see what is really going on. I'll soon have a better idea, ordered a RigExpert AA-55 analyzer, and another 40 x 32 ft radials for the vertical / inverted L to bring the total to 60.

Getting Started with Digital Modes (WSPR)

Weak Signal Propagation Reporter

Discovering digital modes for the first time, I found WSPR is a great mode to start with as you can simply start listening for and decoding beacons right away, and have your mind blown at how far away these weak signals can be received when you cant hear anything audibly out of the speaker!

This doesn't cover how to configure the software and radio. There are plenty of guides and docs around on how to get WSJT-X communicating with your rig.

My hope is to capture enough data from the WSPRnet.org database to start building a picture of how well my station transmits and receives signals on HF compared to others by looking at distance per watt stats etc.

I have spotted ZS3D several times over the last few days on 40m at a distance of 16, 233km / 10, 087 miles, and today ZS1OA on 30m, slightly further at 16, 511 km / 10, 259 miles! These stations are probably about as close as I'll get to hearing something from my antipode.

A surprise when I spotted beacons from stations on 630m (472kHz) in Northern California and BC!

After a few email exchanges with Joe NU6O, I learned that 630m propagates best with vertical polarization. Joe is using a 43ft vertical near salt water, 100W transmit power to radiate 1W EiRP [Antenna is 1% efficient], his beacons are regularly decoded in Japan across the Pacific.

I'm only spotting stations nearby on 630m because I'm using a Carolina Windom 80, less than ideal for this band being a horizontal wire with out any matching / loading for 630m, its kinda surprising I heard anything at all.

WSPR can also be used to indicate the possibility of using other modes based on the reported SNR, see https://www.qsl.net/kp4md/wsprmodes.htm

Update Jan 03 2019:

Transmitting beacons yesterday..




Heard by DP0GVN in Antarctica on 30m [10Mhz]!

Heard by ZL3003SWL in New Zealand on 15m [21MHz]!

Since posting this I've had some fun with WSPR including 630m, several more posts here.

I've since tried and liked JS8Call, similar to FT8 but enables keyboard to keyboard QSOs, message relaying, APRS and more.