The
ICOM IC-7800 on 50 Mhz EME
On June 20th 2004 I completed with Lance W7GJ my first EME QSO on 50 Mhz band using the IC-7800. I guess that was the first ever EME QSO made by an IC-7800 in the world.
The transceiver immediatly seemed to be really sentive and efficient with very weak EME signals, but I still had to discover all its powerful capability!
The CW DSP 24 bit filter is astonishing and during EME skeds I usually set it to 80 Khz without degradation at all, running NR filter also.
At that time I was running the rig connected to my computer via standard wire cables, decoding signals with my old sound card Sound Blaster 16 bit. Using that set up, I sometime experimented some RF loop between PC and transceiver and noise, as often happens in that circumstances. More over, I was running the IC-7800 with standard internal set up, without any menu change.
As soon as I became more expert in the rig, I realized that it could be a very useful instrument to improve my EME receiving capability. The IC-7800 menu has a lot of menu settings and many of them are really useful to get a perfectly flat audio spectrum, indispensable to have good decoding on digital modes.
Following picture shows how flat is the spectrum on JT6M and JT65A mode.
JT6M filter set JT65A filter set Voice filter set
Typical JT6M bandwith settings
I obtained that result modifying the receiving treble and bass audio tone.
Another very interesting thing, is the roofing filter wich can be set up to 6 Khz to get better signal-noise ratio. I personally experimented about 3db better SNR compared to my Kenwood TS-2000 running same filter bandwidth.
The filter setting permit to reduce bandwidth during JT65A trafik and to improve SNR withouth any kind of distortion or signal degradation. I usually run JT65A EME skeds using 1.3 Khz bandwidth, roofing filter set to 6 Khz, sharp filter.
I got wonderful results when I replaced my old PC sound card with new "Sound Blaster Audigy 2 Platinum". This card has optical input/output and it works great with IC-7800!
"Sound Blaster Audigy 2 Platinum" is a 24 bit card and it has 106 db SNR, a very great improvement on old 16 bit sound boards. I connected it to my IC-7800 by TosLink fiber optic cables and immediatly all RF loops disappeared! Moreover, the audio quality is incredibly elevated and I also noticed an average reduction of EME signals width, expecially during my WSJT EME echo tests: now I always get 0.7 Hz instead of 1.3 Hz I usually got with old SB 16 board.
Another very useful thing is the rear connectors for external preamplifier. On 50 Mhz EME I use a SP-6 preamp. by SSB Electronics, with a declared noise figure of 0,6 db. I connected it directly to my IC-7800 and I don't have anymore to worry about coaxial cable loss or preamplifier damages caused by external relay failure: IC-7800 makes all work for me!
Finally, I fould very interesting and confortable the use of internal compact flash card to store settings. Infact, I saved different settings depending by mode I use: voice, CW, JT6M, JT65 etc.
Every mode has very different settings (filter, audio tones, roofing, bandwith...) and it could be very hard and complicated to remember them every time I change mode.
So, I stored all mode settings in the compact flash card and I only have to recall the mode I want to use in that moment to have in one second the correct settings on line.
In conclusion, the ICOM IC-7800 is a very nice transceiver even for 50 Mhz EME trafik and so far, using it, I completed several EME qso with single yagi stations by digital mode and on CW mode.