Tom Rauch wrote:
>
>There is also a second problem that is almost always overlooked. Some
>rigs switch into transmit while the synthesizer is still moving to a new
>frequency, while others switch before the thing even moves! One popular
>high-end DSP rig does that, you can tell them in pile ups because they
>are the rigs that thump on top of the DX station when they are working
>split frequency.
>
Model numbers?
A similar problem used to happen with the old Yaesu FT-221. This was
notorious for key-clicks, yet it showed a very reasonable keying
waveform on a scope. It turned out to be the keyed IF stage, which burst
into oscillation each time the operating point was changing between on
and off.
The diagnostic was to connect a 10-50K pot across the key jack, and tune
around the signal at various settings of the pot, down to zero ohms. At
a few hundred ohms, it showed a burbling FMy signal which swept over
10kHz or more.
The point was, the scope showed nothing because the problem wasn't in
the time domain; but a second RX (or spectrum analyser) wouldn't show
the spurious either, until the problem was held in a steady state.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.com/g3sek
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