472kHz WSPR overnight

G0MGM (101km) has spotted my 472kHz WSPR (5mW ERP or less) several times. I think he is a new reporter and very welcome too. Tonight I may go back on the HF and 6m wire antennas (with loading coil) to see how results compare with the earth-electrode "antenna" currently in use.  
 .
G8HUH (250km) always seems to copy me.  He has a good system on RX.  He even copied me on 136kHz WSPR from the old QTH, before I had my cerebellum bleed. I have yet to try 136kHz WSPR from this QTH.

Worldwide 136/137kHz grabbers + a simple 2200m RX (kit or ready built)

This link to a very useful list of 2200m grabbers worldwide was found on the website of Yuki JA5FP.   If you are interested in 136/137kHz this list of grabbers may be very useful.  A grabber is a receiver that uploads what it receives to the internet, usually as a spectrograph.

For how to make your own grabber, see how I did it. My grabber is usually only active when I do experiments. See https://sites.google.com/site/sub9khz/vlf-grabbers/vlf-grabber-creation . I used a public folder in Dropbox and pointed my grabber website to this location. In my case I was monitoring 8.97kHz VLF,  or thereabouts, but the same idea will work at any frequency. I used Spectrum Lab or Spectran software to do the actual "grabbing". Other methods are equally valid.

Also on Yuri's site are details of his 136/137kHz receiver. See http://icas.to/lineup/idc-136ii-kit-eng.htm .  This simple, but very effective, receiver uses a divided down HF crystal to give a very stable LO frequency of 130kHz. The output feeds a PC using Spectrum Lab or Spectran software. The receiver is available as a kit or ready built. Ready built the cost (with enclosure and shipped to Europe) is currently $110.  I have no idea if duty is payable.  Kits (less enclosure) is $75 shipped to Europe.

WSPRing on other bands

Today I ventured onto 60m, 40m and 20m WSPR for a change. A few spots out to 448km on 5MHz and plenty of EU spots on both 40m and 20m.

I returned to 10m to see what was doing.  At this time of day 10m is THE place to find stateside DX in abundance. Conditions like this unfortunately cannot last.

I have now decided to take a look on 136kHz with the earth-electrode antenna and the VERY deaf  FT817ND.  I might JUST be able to copy DK7FC and possibly G8HUH but I do need to make a preamp.

UPDATE 2025z: absolutely nothing copied on 136kHz WSPR. I need a preamp!

A mag-mount as an E-field probe for 137kHz

Next week, assuming the snow has gone, I want to drive around the local area to plot the polar pattern of my earth-electrode antenna working on 137kHz.  My 7-8W beacon transmitter can send a range of QRSS and CW messages, so I want a way of driving to different places using my FT817 fed via a preamp and measuring the S/N using Spectran whilst remaining inside the car.

Portable RX loops are fine, but these are directional and need to be set up each time a measurement is taken outside of the car.  Ideally I need an omni-directional RX antenna like an E-field probe. So, I'm looking for a way to drive to a spot, take a quick measurement from inside the car, then move on; a loop works, but when it is -2 deg C outside and the ground is icy, it is not ideal.

Either I put the electronics for an E-field probe right at the base of the mag-mount (mechanically not ideal) or I have the electronics in the car and somehow tune out the coax cable capacitance.  At the moment I am still experimenting to find an arrangement that works with good sensitivity by checking the strong Greek commercial signal just outside the 137kHz band.

Based on 472kHz results, the earth-electrode antenna behaves like a loop with loop-like directionality. I 'd expect to see the same pattern on 137kHz.

Back on 137kHz TX

QRSS and CW beacon TX for 137.685 kHz

Today I went into the shack with the intention of making a new transverter for 137kHz based on my recent design for 472kHz.

Instead, I ended up building a new CW, QRSS3 and QRSS30 8W beacon transmitter using an IRF640 PA device. This evening and overnight the beacon will run QRSS3 on approximately 137.685kHz and I have requested reports and screenshots.

The antenna being used is my 20m spaced earth-electrode pair set-up used very successfully on 472kHz last weekend. On 137kHz signals are much weaker than on 472kHz, so I await reports with interest.

The whole unit runs quite cool when housed in a plastic box. Switches on the front of the boxed unit allow up to 7 pre-programmed messages to be beaconed at varying speeds. As normal, I use the K1EL beacon chip for the beacon message generation. The signal source is a 3.579MHz crystal in a divide by 26 circuit implemented in a PIC like device and kindly supplied to me by a French amateur Francis F6HSI a few years ago.

472kHz update

With nearly 2 weeks of operation on the new band with very low EIRP levels (varying from typically 5-10mW with 100mW on just one occasion) perhaps it is time to summarise how things have been going. A check of the WSPR database shows almost 70 unique reports across Europe of my signals from just a few km away to 1736km. I have still not managed to be copied by TF3HZ in Iceland at just over 2000km and this is my next target. To achieve this will need me to re-erect and better optimise my Marconi vertical. With some optimisation it should just about be possible achieve 200mW EIRP.

Unique WSPR spots in the last 2 weeks on 472kHz

On CW I have received a report from over 160km away when I was calling CQ. A JT9-1 QSO with G3ZJO at 79km is still my best 2-way QSO, although I believe it should be possible to work much further with this mode (I worked OR7T in Belgium with it on 500kHz).

So, pretty satisfying results so far. This has been helped by the huge number of stations currently monitoring WSPR on the new band - frequently over 40 people at any one time. Right now there are 59 stations monitoring!

On 136kHz the challenge with small antennas and low power is considerably harder on WSPR as there are too few stations monitoring: even if the signal was getting several hundred km, one can only tell if someone is at the far end and reporting it.

Thoughts turning to 136kHz again

After a few weeks on the new 472-479kHz band, my thoughts are again turning to 136kHz, a band that I experimented with a year or more ago now. This band is MUCH harder work than 472 or 500kHz with around 20-30dB more of everything (!) needed.  By this I mean that for the same power, the "effort" to get a contact or report seems to be about 20-30dB more. This is partly because the short antennas I use have a very low radiation resistance at 136kHz so losses become more significant. Also, noise can be even more of an issue.  Despite all of this, I plan to make a 136kHz version of the transverter I did for 472kHz, but maybe with a bit more RF output (in the 20-30W region). Most of the design is ready done (in my head) so it should only take a few days to do. The plan is to TX using my earth-electrode antenna.

On 136/137kHz there are fewer stations using WSPR, so I will probably use QRSS more. In the past I have made QRSS crystal controlled beacons for this band, but with a transverter and my FT817 I will be able to generate a QRSS signal wherever I want in the band and also be able to have QRSS QSOs.

Does anyone have recommendations for SIMPLE PC program that will allow me to generate QRSS (various speeds) as an audio tone? 

This way I can use my SignaLink USB interface and VOX to send QRSS (or DFCW) using audio tones. Please don't suggest Spectrum Lab unless you can give me a "Noddy guide" on how to use it for QRSS! This is a very good program, but to a simple soul like me it seems like you need a PhD to drive it. In the past I've used it for VLF reception, but it took me weeks to work out how to drive it and every time I go back to it I need to learn it all again. I just want a simple QRSS tone generator.

New LF Yahoo Group

After some debate, the old RSGB LF-reflector is now migrating to a new Yahoo group at http://uk.groups.yahoo.com/group/rsgb_lf_group/ . If you have an interest in the VLF/LF/MF amateur bands such as 8.97kHz, 136kHz, 472kHz and 500kHz then you may want to join. It is sure to become one of the most useful resources on the web for up-to-date information as well as a valuable archive of schematics, photos and ideas.

136kHz grabbers and a DC receiver for the band

A list of all the known LF grabbers (on-line to the internet LF receivers) in the world is available at http://icas.to/argo/grabbers-list.htm . A receiver to use with a 136kHz grabber is available as a kit or ready built from http://icas.to/e/ . This is a simple, but effective, direct conversion design which is already in use at several grabbers around the world.

Germany- Venezuela on 136kHz

DK7FC has been helping YV7MAE set up a grabber for 136kHz and over the last month they have been improving the system day by day. Last night Stefan's DFCW signal was copied quite well for the first time over a distance of 7818km. This is the first time a European station has been copied in South America I believe on this band. The grabber can be seen at http://dl.dropbox.com/u/74746618/LF/YV7MAE_LF_Grabber.html .

OPERA - new weak signal beaconing mode

There is a new very weak signal beaconing mode being trialled currently on 136 and 500kHz called OPERA. The current version is available as a zip download at http://www.mediafire.com/?w74a061m48nv806 but this is a beta version and updates are happening quite fast at the moment, so best check the RSGB's LF reflector for the most recent version from Graham G4WGT.

Initial indications are this is even better than WSPR, which as we all know is an excellent QRP beaconing mode. I managed to decode SM6BHZ (just under 1000km) and PA0A tonight when using just my 20m separated earth electrodes (no antenna in the air here at all) on 136kHz.

Over the weekend I may give this a go with a few mW ERP on 500kHz and, when I get my vertical loop re-erected, on 136kHz too.

Early days yet, but a most interesting mode that does NOT need critical PC timing (unlike WSPR) and that can use the PTT line or VOX control to key the TX i.e. it is simple to interface rig to PC.

500kHz

With the autumn season not too far off I am turning my thoughts to 500kHz and 136kHz again. This weekend I hope to return to 500kHz WSPR as GM4SLV is testing his new 500kHz antenna and ATU. After that it will be my turn to improve the ERP on 136kHz with a new PA, ATU and antenna.

137kHz transverter update

Breadboarded 137kHz 8W transverter (ERP 50uW from antenna)

Simple 137kHz QRP transverter - click for larger image

Today I combined the RX and TX parts of my 137kHz QRP transverter for the first time and all is working although I'm losing a few dB in RX sensitivity at the moment. Copying DL, SM, PA and G stations on WSPR RX. Best DX being 148km on WSPR TX.  Who says LF has to be hard? HI.

136kHz RX activity

In the last few weeks I've received 136kHz signals from several different countries and stations:

DK7FC/P     CW/QRSS
DF6NM     QRSS
G8IMR      WSPR
M0BMU    WSPR
PA0A    WSPR
SM6BHZ     WSPR

Certainly my receiving system is now up with the best since adding the tuned preamp. My main drawback is the TX/RX loop's directionality which reduces signal levels in a N-S direction. We just need a lot more stations active on the band, especially on WSPR.

Short Marconi vertical on 136kHz - forget it!

ATU for 136kHz. Antenna connected to top of ferrite rod

Disappointing results yesterday with a very short Marconi vertical tuned using a ferrite rod loading coil and variable capacitor. ERP was calculated as around 200uW, but in reality the ERP was around 10dB down on the vertical loop (based on WSPR reports locally), so the ERP was around 5uW only. Most of this can be put down to the coil losses and to tiny current actually flowing in the antenna part actually radiating. A much more efficient antenna for the band will require a BIG loading coil outside and more wire in the air with some top loading. I could erect a 6m vertical antenna with a sloping top capacity hat horizontal section with an overall vertical rise of 10-12m. Antenna improvement could increase ERP by >6dB. TX power could be raised by 6dB. Taken together this would make a difference, but it would not meet my QRP ethos.

My conclusions are that an ultra-simple QRP approach to 136kHz TX is just not possible if one is to achieve useful results consistently.

ERP with the loop on 136kHz

Today I did a recalculation of my 136kHz ERP using the loop antenna with my WSPR transverter. I have a small RF ammeter in series with the loop wire and I measured the current as 1.3A.

For 136kHz the ERP of a loop is = (I^2 * A^2) / (205 * 10^6)
where I = loop current and A = loop area (see "LF Today" RSGB book p101)

Putting in the numbers ERP = 1.3^2 * 80^2 (205 * 10^6)

So my ERP = 52uW on 136kHz.

A further 3dB could be obtained by thickening up the wire used in the loop taking the ERP up to around 100uW. Other improvements could come from increasing the TX power output from the present 5W. Later today I will work on a small ATU to resonate my 5m feeder to the 28MHz halo as a Marconi vertical. First I will work out the antenna current needed to beat the ERP of the loop. At least a Marconi will not be directional, which is a drawback of the loop.

DK7FC/P on 136.8kHz normal CW

DK7FC/P very strong on 136.8kHz CW today

Stefan has been out /P with his 100m long kite antenna, this time on 136.8kHz CW. He was excellent copy here in the UK (JO02dg) with a signal some 20-30dB over the noise floor even when sending fast CW. Attached is a screen shot from Spectran showing him working DF6NM at 1715 this evening. Distance is around 649km.

136kHz WSPR DX reception

Today there were several stations active on 136kHz WSPR with best DX heard the 50mW ERP beacon of SM6BHZ. Also copied PA0A and G8IMR. So far this evening no-one has heard my own modest (10-20uW ERP) WSPR beacon on 137.5kHz though. I'll keep trying.....

G3XDV on 136kHz QRSS

Getting a very strong signal this evening from G3XDV on 136.177kHz QRSS60 receiving Mike on the earth electrodes fed straight into the deaf (at 136kHz) FT817. He is sending "XDV" preceded by G3XDV in normal speed CW.

Vertical loop versus earth electrodes antenna

Just done an interesting test comparing my vertical wire loop with an earth electrode antenna. I removed the lower part of the loop and connected the ends to ground. Matching was totally different (low Q antenna) but the performance was only 5dB down on the loop, based on reports from 2 local and one DX station. A similar test on 136kHz as the only station on in range (M0BMU 69km) was unable to copy my signal on the earth electrode antenna suggesting at least 5dB down on that band too.