RE: [amsat-bb] Ultra portable AO-40 RX system

["Howard Long" <howard@xxxxxxxxxxxxxx>]

Hi Pedro

> I would like to make an "ultra-portable" RX-only system in order to hear
the
> AO-40 this summer holidays in my boat. I have the following rigs:
>
> - DB6NT MKU-24 OSCAR Converter (0,6 dbNF and 26 db gain)
> -Kenwood TH-F7E (European version of TH-F6A)
> -Icom IC-R10
>
> I think I should use the TH-F7 instead of the IC-R10 because it is more
> sensitive (at least in VHF/UHF ) and the bandwidth is better for SSB use
(I
> know that the handheld scanners have bandwidth problems in SSB, but I need
a
> truly portable system).

You have hit the nail on the head! The SSB filters are rather wide on these
radios (~6kHz) and this makes the signal more noisy, plus you get
interference from adjacent QSOs. They also have rather bad LSB rejection. A
proper Ham SSB resolver such as that in the FT-817 really is far far better.
Either are great radios if you're just trying to receive the beacon.

> My doubt is about the antenna. I would like to use a helix because it is
the
> most portable antenna that I know (I think that a 2.4 linear Yagi is worse
> due to the polarization).
> I would like to know the minimal antenna gain that I need with this setup.

I have used a 15ele linear Yagi to resolve SSB signals, but it is very hard
work. So far for reliability, portability and performance my umbrella dish
II has been very useful indeed http://www.g6lvb.com/brollydish2.htm.

73 Howard G6LVB


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