[Amps] ARD-230A

[R.Measures]

On Aug 12, 2005, at 4:48 AM, Fortra wrote:

> Hi Amperes,
>
> I am in process to make a difficult decision, whether to buy an 
> Advanced Radio Devices Amplifier ARD-230A. The amp is in apparently 
> good conditions, with quality parts, and operational. Does anyone of 
> you have had any experience with it??

I used to discuss, via mail and telephone, the ARD 230A  with the 
factory technician who repaired them.  He told me that some of units 
that came back under warranty for repair appeared to have been damaged 
by intermittent VHF or possibly UHF parasitic oscillations, which 
should probably not be surprising since the 3cx800A7 is rated for full 
input in "Amplifier and Oscillator Service" up to 500MHz.  After he 
read my articles in *QST* discussing parasites, he became more 
convinced that he was on the right track and he contacted me.  He 
subsequently informed the owner and designer of the repeated signs of 
such damage he was seeing and suggested that they try decreasing the Q 
of the VHF suppressors in order to decrease VHF and UHF gain.  The 
suggestion was rejected, the problems continued, and within a year ARD 
went under.  I still have the set of ARD 230A drawings he sent me 
during the discussions, so if you would like to have them I will mail 
them to you.

> Judging from Google search, most of the problems were with software 
> (run by Z-80 processor).

- - - Editorial opinion -- As I see it, unless the equipment is to be 
operated by a moderately retarded chimpanzee, trying to control a RF 
power amplifier with a microprocessor makes about as much sense as 
trying to control a lawnmower with one.

> Amp has otherwise quality parts as Alpha not to get into great 
> detail.But as it is fully remote, should I give in into it....Your 
> advices please!
>
> p.s.It has pair of 3cx800a7
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org