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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