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Date: Sat, 12 May 2012 20:41:59 +0100
Message-ID: <CAA8k23RrSSyN6DtTFG7vUFjAu4Qua9hYWwr3_KafPRQY+0ZGNQ@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: IEEE488
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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 <g8fzk@g8fzk.fsnet.co.uk> wrote:
> R Martin
>
> Well =A0that's =A0the =A0problem, we all =A0know =A0what the =A0kit =A0ca=
n do , but =A0there
> are =A0only a =A0few who =A0can tap the =A0keys =A0and =A0make it =A0perf=
orm ..
>
> Like =A0Jim mentioned , other =A0modes , now , I think =A0the =A0read/ref=
resh rate
> of a =A0counter/timer =A0 and =A0your =A0f-gen over the =A0ieee =A0would =
=A0be fast enough
> to =A0follow =A0a slow =A0qrss , mfsk opera =A0or =A0other =A0single carr=
ier =A0mode , by
> reading =A0, process , output to the =A0f-gen
> a sort =A0of =A0eccentric cam =A0software mechano =A0chain drive .... wit=
h a =A0limit
> switch hihi ,must be =A0HP dev guy about =A0??
>
> That's =A0the problem, software people , ( may be by default) are not
> pioneering =A0and the =A0hardware gang never =A0did =A0get the =A0idea of=
 =A0a keyboard
> ! =A0 Everyone though the =A0Opera idea =A0was =A0crazy , (most =A0still =
=A0do:) , =A0its
> far removed =A0from the =A0simple data =A0system that I envisaged , but I=
 had =A0no
> idea , as to =A0how =A0advanced the =A0world of =A0DSP actually =A0was ..=
 still =A0not
> quite =A0sure , but there a lot of =A0apples laying about =A0for =A0some =
=A0reason !!
>
> 807 6v6 ef50 cv138 =A0still =A0got =A0boxes of those =A0in the =A0shed al=
ong =A0with all
> =A0the =A0other =A0big lumps of transformers =A0and things that =A0would =
probably go
> bang if powered up . as =A0kit =A0and =A0age advanced =A0 retreated indoo=
rs =A0to the
> =A0warm !
>
> I think =A0your keying relay =A0would be =A0OK for =A0OP8 =A0.as long =A0=
as =A0the pull in
> and =A0release =A0times =A0are well =A0matched to retain the =A0envelope =
shape .. this
> side of the =A0DSP =A0engine is a =A0bit =A0of a mystery , basically, the=
 =A0closer to
> the original time envelope and =A0frequency stability , the =A0better =A0=
will =A0be
> the decode min s/n =A0 (low % improvements )
>
> I think =A0pulse 'jitter' =A0would =A0be a =A0problem on the =A0higher (s=
horter)
> versions ...... =A0could =A0you =A0not =A0use =A0blocking keying =A0or a =
=A0pin diode
> switch ? =A0,,,,,,,,,Racal =A0 use to =A0use TTL logic gate =A0chips to =
=A0switch
> oscillator =A0lines , by holding =A0one =A0side =A0of a =A0(and) =A0hi or=
 low ..... or
> use a opp-amp =A0as linear =A0switch ...
>
> GL - 73 -G..
>
> --------------------------------------------------
> From: "Martin Evans" <books@mollies.freeserve.co.uk>
> Sent: Saturday, May 12, 2012 7:47 PM
> To: <rsgb_lf_group@blacksheep.org>
> 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 a=
nd
>> 807s!
>>
>> Martin =A0GW3UCJ.
>>
>> ~~~~~~~~~~~~~~~~~~~~
>>
>>
>>> It may =A0be possible , =A0IEEE =A0 cards for PC =A0 are available =A0o=
n ebay ,
>>> originally it =A0was =A0complimentary to =A0HP basic, and =A0used the H=
P range of
>>> PC's with =A0addressed =A0card slots .. allowed =A0you =A0to =A0constru=
ct a automated
>>> system from =A0discrete =A0items of =A0equipment ..HP unless you hacked=
 your =A0own
>>> control =A0card , going =A0back to 1972 is the =A0first =A0I remember ,=
 linked to HP
>>> =A0neon nixie =A0tubed =A0DVM and Counter / timer , with a IEEE>GEC =A0=
re-hash on
>>> the back ,
>>>
>>> The IEEE =A0 drivers =A0(Instrument set up frame) =A0should be download=
able
>>> from the =A0R&S =A0web =A0site , as to qrss =A0, you would need =A0to =
=A0interface with
>>> the HP-basic control =A0programme , read a =A0switch/button or line vol=
tage , I
>>> dont think it would be simple =A0to =A0bridge .but =A0you could set up =
a =A0series
>>> of carrier on.off =A0timed commands in basic , but =A0its a big task =
=A0for a
>>> =A0task that is =A0covered =A0by other =A0software
>>>
>>> unless =A0for =A0example the =A0LCD =A0display has =A0finally =A0washed=
 out =A0and the
>>> IEEE is the =A0only =A0way to =A0set the =A0instrument =A0up , in which=
 case its quite
>>> =A0simple , just =A0run the =A0set-up =A0frame =A0and control =A0from t=
he =A0pc in remote
>>> =A0mode , a useful =A0second life !
>>>
>>> 73 -G..
>>
>>
>>
>