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Re: LF: IEEE488

To: [email protected]
Subject: Re: LF: IEEE488
From: Andy Talbot <[email protected]>
Date: Sat, 12 May 2012 20:41:59 +0100
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 A JFET switch is probably the simplest.   Uses a P Channel device
like a 2N3820 so it can be controlled with a positive voltage.     +V
is device  off, 0V is switched on.  Which sounds a bit weird to
visualise   Used in shunt means a +Ve voltage switching it off gives
RF is on.  0V attenuates RF.  Rds(on) is a good few ohms, so needs to
be run in a Hi-Z system.  There are no doubt better P-Chan FETs.

Andy
'jnt


On 12 May 2012 20:23, Graham <[email protected]> wrote:
> R Martin
>
> Well  that's  the  problem, we all  know  what the  kit  can do , but  there
> are  only a  few who  can tap the  keys  and  make it  perform ..
>
> Like  Jim mentioned , other  modes , now , I think  the  read/refresh rate
> of a  counter/timer   and  your  f-gen over the  ieee  would  be fast enough
> to  follow  a slow  qrss , mfsk opera  or  other  single carrier  mode , by
> reading  , process , output to the  f-gen
> a sort  of  eccentric cam  software mechano  chain drive .... with a  limit
> switch hihi ,must be  HP dev guy about  ??
>
> That's  the problem, software people , ( may be by default) are not
> pioneering  and the  hardware gang never  did  get the  idea of  a keyboard
> !   Everyone though the  Opera idea  was  crazy , (most  still  do:) ,  its
> far removed  from the  simple data  system that I envisaged , but I had  no
> idea , as to  how  advanced the  world of  DSP actually  was .. still  not
> quite  sure , but there a lot of  apples laying about  for  some  reason !!
>
> 807 6v6 ef50 cv138  still  got  boxes of those  in the  shed along  with all
>  the  other  big lumps of transformers  and things that  would probably go
> bang if powered up . as  kit  and  age advanced   retreated indoors  to the
>  warm !
>
> I think  your keying relay  would be  OK for  OP8  .as long  as  the pull in
> and  release  times  are well  matched to retain the  envelope shape .. this
> side of the  DSP  engine is a  bit  of a mystery , basically, the  closer to
> the original time envelope and  frequency stability , the  better  will  be
> the decode min s/n   (low % improvements )
>
> I think  pulse 'jitter'  would  be a  problem on the  higher (shorter)
> versions ......  could  you  not  use  blocking keying  or a  pin diode
> switch ?  ,,,,,,,,,Racal   use to  use TTL logic gate  chips to  switch
> oscillator  lines , by holding  one  side  of a  (and)  hi or low ..... or
> use a opp-amp  as linear  switch ...
>
> GL - 73 -G..
>
> --------------------------------------------------
> From: "Martin Evans" <[email protected]>
> Sent: Saturday, May 12, 2012 7:47 PM
> To: <[email protected]>
> Subject: Re: LF: IEEE488
>
>> Well, what you're saying could sound simple to you, Graham, but a nice
>> keyed relay sounds a lot simpler to a Silver Surfer brought up on 6V6s and
>> 807s!
>>
>> Martin  GW3UCJ.
>>
>> ~~~~~~~~~~~~~~~~~~~~
>>
>>
>>> It may  be possible ,  IEEE   cards for PC   are available  on ebay ,
>>> originally it  was  complimentary to  HP basic, and  used the HP range of
>>> PC's with  addressed  card slots .. allowed  you  to  construct a automated
>>> system from  discrete  items of  equipment ..HP unless you hacked your  own
>>> control  card , going  back to 1972 is the  first  I remember , linked to HP
>>>  neon nixie  tubed  DVM and Counter / timer , with a IEEE>GEC  re-hash on
>>> the back ,
>>>
>>> The IEEE   drivers  (Instrument set up frame)  should be downloadable
>>> from the  R&S  web  site , as to qrss  , you would need  to  interface with
>>> the HP-basic control  programme , read a  switch/button or line voltage , I
>>> dont think it would be simple  to  bridge .but  you could set up a  series
>>> of carrier on.off  timed commands in basic , but  its a big task  for a
>>>  task that is  covered  by other  software
>>>
>>> unless  for  example the  LCD  display has  finally  washed out  and the
>>> IEEE is the  only  way to  set the  instrument  up , in which case its quite
>>>  simple , just  run the  set-up  frame  and control  from the  pc in remote
>>>  mode , a useful  second life !
>>>
>>> 73 -G..
>>
>>
>>
>


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