23cm propagation



12 July 2013 -  heard beacons HB9EME (824km) and EA2TZ (877km).

6 July 2013 at home - very good tropo conditions - worked EA2TZ/P (863km), TM7G (877km), DF0MU (694km).

3 Mar 2013 - portable contest operation from IO91RF with some good tropo to DJ5BV (531km), PI4GN (547km), DK2ZF/P (748km), DF0MU (549km)  and GM4CXM (582km).

Another nice tropo duct on 15 November 2012 gave me contacts with DC8UG (731km) and OK1MAC at 1238km.  HB9EME beacon was again audible at up to 529.  Stations in south east England heard or worked OE5VRL/5, but there was no trace here - would have been 1248km.

HB9EME beacon heard on 6 Sept 2012 at 2058z.  (mp3, 57sec, 449kB).    The beacon transmits a ramp of 4 second tones separated by –6dB steps from 12W down to 12mW (0 to –30dB); and is audible here to -24dB level (or better?).

Rain scatter

I noted an interesting effect on 20 Dec 2011 whilst listening to the Bristol beacon GB3USK on 1296.875 (about 32km but direct path is obstructed - see below).  The signal had been quite good a couple of days previously, but on this evening (of the UKAC contest), the strength had dropped by 18dB, and the signal was auroral sounding, presumably due to rain scatter.  It certainly was raining at the time.  You can hear the effect here, and the spectrum shows a spread of about 80Hz LF of the carrier, as shown below.  The drift is probably due to my transverter.

GB3USK rain scatter spectrum
GB3USK to G3TCT path
Terrain plot of my direct path to GB3USK, where there's a much reduced signal on 23cm. The recording and spectrum above was taken beaming about 35 degrees NE of the direct path.

PS.  18 July 2012

More rain scatter, only this time in the "summer"!  The following was recorded on 18 July 2012 at about 1456z.  It is of GB3USK (nominally due north) whilst I am beaming between 065 and 075 degrees.  Scatter is evident around 90 to 170Hz LF of the carrier.  Surface temperature at my QTH was 19.2C, max wind speed 30kph.  A sound clip is here (.mp3 format, 410kB, 52 sec).
Rain scatter July 2012 Click on image for full size
The image is of spectrumlab showing the scatter signal LF of the carrier, both of which are audible.

My 23cm system

K3 transceiver driving a homebrew 2m transverter driving a DB6NT 23cm transverter (MKU13G3) running about 3W.

DB6NT transverter2m transverter

Homebrew 2m transverter.                                                                                                 DB6NT transverter

This drives a PE1RKI module amp which then drives a linear to 150W output.  About 33W reaches the antenna, a Wimo 44ele yagi at 13m agl.

PE1RKI 23cm amp

PE1RKI amplifier

I have built a masthead preamp, details as follows:-.
Circuit is due to OZ2OE
PCB supply is from rfextra
SMA connectors and adaptors are from chinarf
Layout diagrams are here and here

The completed PCB is shown here.  I bought a cheap microscope to help put the SMD components in. 

After several disasters I have ditched the 24V coax relays in the preamp box (see picture here) as they seem unreliable, indeed some of them have a tendency to stick on receive when powered for transmit - the preamp does not survive this.  The new layout (here) uses a 12v Ducommun 2N1B11 relay with a separate feeder for transmit.  The relay is specified as handling 270W at 1.3GHz and has measured isolation of about 70dB.

I have modified my sequencer (based on the W6PQL design) to accommodate both 12v and 24v relays.  My sequencer drives the relays and the 12v bias supply to the PA.  Schematic is here.

The complete transverter is shown here:
Transverter exteriorTransverter interior
The interior view shows (left to right) 28V 13A PSU, 23cm filter, DB6NT transverter, relay drive circuit (now replaced with sequencer), PE1RKI module amplifier, PE1RKI PA and fan.