SV: [AMPS] IMDs

[sm5ki]

On what band?
----------
>Från: "G0MJW" <mike@g0mjw.freeserve.co.uk>
>Till: <amps@contesting.com>
>Ämne: [AMPS] IMDs
>Datum: mån 6 mar 2000 12.14
>

>
>I happened to have an FT690R on the bench and the posts regarding IMDs
>prompted me to look at the results from a "typical" solid state driver. The
>FT690R is not renound for its quality output but I expect many older solid
>state rigs are similar. The test involved a 2-tone test at 1.2 kHz and
>2.2kHz, with adjustments made to make both tones equal in level. The values
>in the tables are levels of IMDs relative to one of the tones. They are 6dB
>better relative to PEP. The ALC was used to set the output.
>
>Here are some results.
>
>12.5V supply.
>
>Power    3rd    5th    7th    9th    11th    13th    15th    17th
>2.5W    -28    -29    -41    -47    -49    -53    -62
>3.0W    -24    -30    -37    -48    -53    -53    -57    -64
>4.0W    -16    -30    -35    -37    -43    -53    -58    -61
>
>At 5W I only measured the 3rd order, as it was only -13dB !
>
>13.8V Supply
>Power    3rd    5th    7th    9th    11th    13th    15th    17th
>2.5W    -30    -32    -41    -47    -51    -57    -64    -68
>
>10.1V Supply (I.e. NIMH battery)
>Power    3rd    5th    7th    9th    11th    13th    15th    17th    19th
>2.5W    -18    -29    -31    -40    -51    -53    -54    -55    -59
>
>
>The results show two things.
>
>1. It is only sensible to extract 2.5W from the FT690. 2.5W set on FM
>measures an average power of 1.5W under 2 tone testing, that is 3W PEP.
>Under these conditions, the rig is really not all that bad and could be used
>to drive a good quality linear amplifier without offending the locals too
>much.
>
>2. When running of the internal battery, the IMDs are poor. This is OK as
>long as there is no big amplifier following the rig but is a strong warning
>for those intending to go out portable with a car battery and a small linear
>as the signal will be awful once the battery starts to go flat.
>
>
>
>
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>

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