Friday, 17 May 2013

More 6m WSPR

50MHz conditions are getting better
Just as I'm posting this, I'm getting someone coming through at -90dBm on 50.293 but it's not WSPR because the transmission was only for one minute and not two. Could be some other JT65 type mode. The centre frequency was around 50.294610 MHz.

Monday, 6 May 2013

6m WSPR

GM4FVM and G7SKR (Warrington) received me on 50 MHz WSPR today. Also M0XSD (Frizington) and G7IEI (Westhoughton) on 28 MHz.
HF/6m at these distances is just as interesting as getting Italy etc.
Had a play with the JT9 data mode today too, getting to Japan on 21 MHz. I still prefer WSPR though.

Friday, 3 May 2013

Noise

The background noise level on HF (especially 28MHz) has dropped today, something must have been switched off nearby.
At 28.125 MHz, the noise is now -106dBm in a 2.5KHz bandwidth (Antron 99 on the back of the house), recently it was in the -90s which was making it impossible to receive any weak signals.
At 50.295 MHz it was -116dBm on the Comet GP15 tri-bander on the chimney, same bandwidth.
I tried WSPR on 50MHz today but got no transmit or receive reports.

On 14MHz, the Antron 99 and wire antennas are within 1dB of each other on receive (both tuned for minimum SWR with the LDG Z-11Pro II tuner) for a local signal. The background noise level is lower on the Antron though.
On 14MHz the Antron's SWR is very high but the tuner still handles it without any problems. The wire isn't designed for 14MHz either, it's acting more like a 10MHz half wave/20MHz full wave.

 Antron 99, all tuned for best SWR, 7:40pm local time. 2.5KHz bandwidth.
14.095 MHz = -102dBm
18.140 MHz = -94dBm
21.095 MHz = -91dBm
24.925 MHz = -96dBm
28.125 MHz = -105dBm
29.695 MHz = -107dBm





Mobile Antennas

Nagoya NL77B 2m/70cm mobile antenna. I've had this for over 3 years. It's not resonant on 2m, with the SWR not even going below 1.5:1 on any VHF frequency.
It's about 40cm long, so shorter than 1/4 wave on 145 MHz.

Last month I bought another compact 2m/70cm mobile antenna, the Moonraker MRQ525 which is slightly longer but still less than 1/4 wave at 145 MHz.
There isn't much of a difference between them in SWR readings, neither give a very good SWR when used on the same mag mount.
I compared them on receive along with a straight 145 MHz 1/4 wave whip, on the same mag mount.
In the 145 MHz amateur band, both were worse than the straight whip (they are shorter so expect them to be worse) by between 0 and 1 bar on the Yaesu FT-8900 meter.
At around 165 MHz, there was little or no difference between all 3 antennas, the 2 dual banders would be around 1/4 wavelength tall at this frequency. A straight whip cut for the exact frequency would be better but then it would not be a match for 145 MHz.
At around 455 MHz, the dual banders were very similar, but the straight 145 MHz 1/4 wave was down by around 3 signal bars (5 bars on the dual banders was 2 bars on the straight whip).
Without the centre phasing coil, the straight antenna acts as a 3/4 wavelength on UHF, with an uneven radiation pattern. That's fine if you have no interest in UHF at all.
There was nothing in the 430 - 440 MHz band to test it with at the time. The results would probably be around the same as on 455 MHz as they all seem quite wideband.
At 393 MHz, which none of them were designed to cover, the straight whip was still about 3 bars down and the Moonraker was slightly better than the others.
I also had a Watson W770 2m/70cm dual bander but this has developed a fault which made it worse than all 3 of the tested antennas.
A Watson W770 copy (by Sharmans) that I also have, is a bit worse than the 2 short dual banders around 165 MHz but better on 145 MHz.

Although the Nagoya is a 'cheap' brand, mine has had no faults after 3 years when it has been left on the car day and night, it is solidly built. I've had Moonraker antennas fail after a short time before, so it will be interesting to see what happens to this one. They are probably all built in the same factory in China anyway.
For everyday use where wideband reception is also important, these small dual banders are as good as anything else. Higher gain models will have smaller bandwidths.