Design ideas for a QRSS/WSPR 30m TX/RTX

The presence of a strong local QRSS 30m beacon nulls out my chances of successful DX in that portion of the band. So to enjoy these narrowband techniques, including WSPR, I started thinking of a homebrew transmitter.

WSPR support requires:

• SSB-like modulation
• linear RF amplification
• stability

but the design is simplified by the fact that:

• output sits in max 300 Hz (threehundred hertz)
• no need for >0.5 W for satisfactory results
  

Given the above, combined with the fact that I have a 40.5504 MHz canned oscillator (10.1375 MHz * 4), I imagined three solution as depicted in the following picture:

Option 1 should be an SDR transmitter. Not much different in the TX chain from a simpler NE602 Gilbert cell mixer, but has an intrinsic bidirectionality that allows building a transceiver without duplicating stuff. The single XTAL filter removes the unwanted sideband (both on option 1 and 3).
Option 2 should generate an USB signal but requires a I+Q WSPR signal, that should be possible to produce software-wise.

Ah, one more thing: driving a QRPp transmitter with a QRO computer is complete nonsense. I would record WSJT signal in a WAVe file and send it to the TX with a simple mp3 player.

A good Monday morning on 30m

Before retracting the antenna in >50 mph winds (and going to work), this morning I tried some calls on 30m. Managed 3 contacts, including one 2xQRP: me 5W, RA3 with 1W.

I do not complain about dead HF bands. HI.

My first WhiSPeR

Intrigued by a simple TX for WSPR mode I came across while surfing the net, I wanted to give it a try. Since at the present time I own only a 30m antenna, it was very easy.

I plugged the laptop input to the DATA socket output of my FT-817. Please note: the laptop was battery powered so to avoid ground loops. Proper radio-computer connection requires an insulated interface!

Tuned to 10138600 Hz USB and listened while the WSPR software was silently running on its own (What is it doing? I wondered...). I have a local S9 QRSS beacon just below 10140000 Hz and a lot of RTTY activity was going on (weird for a Tuesday night on a no-contest band).

On the receiver I used the variable PBT to exclude the local beacon and after few minutes the software reported:

090303 2134  16 -12  0.8  10.140133  NJ0U EN71 37            1 12556   -1
090303 2134  12 -18 -0.5  10.140146  F6BIA JN18 33           0 16341    2
090303 2134  18 -13  1.9  10.140206  W1XP FN42 37            0     1    0
090303 2134  24  -5  0.3  10.140267  F4EMV JN18 37           0     1    0
090303 2140  11 -22  0.3  10.140167  N9KCQ EN62 37           0  4180    0
090303 2140  19 -14  1.0  10.140193  F4DTL JN18 40           0     1    0
090303 2140  21  -8  1.9  10.140203  IZ1ERR JN35 37         -1     1    0
090303 2142  21 -11  2.0  10.140206  W1XP FN42 37            0     1    0
090303 2142  23  -9  0.8  10.140245  F5WK JN18 40            0     8    0

Stations were running between 2W (33 dBm) and 10W (40 dBm). I was surprised to receive French stations, that I've never heard on 30m! They were probably backscattering over the Atlantic ocean.

Nice, technically advanced system. A bit cryptic software. I am considering to build a QRSS/WSPR TX out of commonly available parts. Either DSB with a single-XTAL filter or SSB with I/Q generation.

Two new US States on 30m

Did not have much energy and time this weekend for the radio, but a late Sunday night session brought in Vermont and Tennessee. The latter had a KG4 callsign, which I initially located in Guantanamo Bay. Never mind.

I was pretty tired and my CW copying skills were down to the bottom. I remembered what Hans UPL wrote me when my first child was born: sleep deprivation equals lousy CW op.

I need to build an interface to a tape recorder for my FT-817 so I can record contacts and enjoy them afterwards.

In the meantime I have drilled the shack wall to let the coax in. Antenna is still the horizontal base loaded monopole.

30m update

Two new countries on my 2009 30m CW QRP challenge this weekend. The band was incredibly open on Saturday night, with many stations chasing K5 DX-pedition not minding a normal QSO. Was not so lucky on Sunday night nor Monday morning.

Statistics so far: 23 DXCC entries, 4 continents.

CU next weekend on 30m!

Replacing your car radio

The cheap radio I got with an used car broke. Actually a small hook holding the detachable front panel broke, so it became useless. Not a bad news since the FM receiver was extremely poor, it played only original CDs and had a PTO tuning mechanism begging for inspection (see previous posts).
I had kept aside an old MW/FM/cassette device from 90's, that is now approximately 14 years old. It had a very good receiver, so it was time to put it back into service!

First thing to know about car radios: they have a standard outer size. So, even if they probably have different hooking mechanism to the supporting frame, they fit interchangeably. I also discovered that mine was only inserted into an existing frame, and the radio body could be pulled out with a simple movement.

Connections were worrying me. Almost two decades had passed, both for car audio industry and car manufacturers. Moreover the two cars were of different makers (Rover vs FIAT).

The antenna connector is the same. I don't know the name of that sort of plug, but I was happy with it.

Rear panel connections looked very similar indeed! Good news: those connectors are standardized, ISO 10487! Moreover both devices carried a label showing cables and their functions, so I could match them side by side and make sure no rewiring was needed.

Newer device had only A and B parts (powering and loudspeakers respectively), while older had also C. Since "C" connector is for extensions, not used in my case.

So I just plugged the antenna and the ISO connector ... et voilà ... the job was done while waiting for a couple of semaphores to turn green.

You may try this at home only if you understand the risks of playing around high capacity batteries. Take your time to make sure both connections are wired exactly the same!

I am now enjoying medium wave reception in a small city car, whose emissions render unpleasant the band:

• below 1000 kHz, with ignition noise on weak signals
  
• during rain with windscreen wiper motors noise
  
• in Summer with A/C pump noise

Have fun.

Crossing the Atlantic, QRP

On Saturday Feb 7th at night I got a 559 report from Maryland, USA. This is the first transatlantic QRP QSO on my homebrew balcony antenna. 30m CW, of course. TU Bill, good ears!

On Sunday night I worked Russia and Ukraine, with good signals. I was surprised to find the band so crowded after two weeks of QRT. 2xQRP was possible too.

FT817 keypad - PTT for the lazy and Timed Tuning

While developing a custom firmware for the keypad, I came up with three more possible functions.

The first is a review of the Quick Tune. Rather than sending a carrier for 5 seconds, the operator controls the duration. One key press sets the radio in FM mode and TX, then another key press returns your trusty Yaesu back to the original mode, in RX. This allows to have shorter and longer tuning times. Let's call it Manual Tune.

In between this new function and the original 5 seconds Quick Tune, lies Timed Tuning. 15 levels of delay are preset, so you can chose whether to tune for 1 second, 2s, 5s ... up to 15 seconds. It requires two key presses.

Finally, the Lazy PTT is for heavy ragchewers , those operators that speak for minutes before listening back for comments. Press a button, your radio goes into TX. Press again and the PTT is electronically released. No timeout, so watch out! This is a good substitute to VOX operation.

These functions should work on 817, 857 and 897.