[hpsdr] Preselector schematic.

[Henry Vredegoor]

I got a "Waiting for moderator approval" message because they were too big
when I sent them all in one message.

There was no doubt by me that they were not viewable ... ;-)


Two observations:

- There must have been a design issue for using relays on the LOWER BANDS;
maybe also the lower (zero) resistance of the relay contacts
- The are having the relays switching a (small) current on purpose, I think
to keep the contacts clean, keep the resistance low



Henry.


> -----Original Message-----
> From: kd5nwa [mailto:kd5nwa at sbcglobal.net] 
> Sent: vrijdag 16 maart 2007 5:33
> To: Henry Vredegoor
> Subject: Re: [hpsdr] Preselector schematic.
> 
> 
> 
> 
> They look fine on my PC. A band pass filter using pin diodes from in 
> to out, then a low pass filter using relays from in to out.
> 
> 
> At 11:19 PM 3/15/2007, you wrote:
> >***** High Performance Software Defined Radio Discussion List *****
> >
> >
> >The pic's seem to be too big, will re-post them one by one
> >
> >Henry.
> >
> >
> >Hi All, Frank,
> >
> >Found the manual. (Nice radio!!) Thank you for your pointers.
> >Had a look at it, looks like a nice and straight forward switched 
> >bandpass filter setup.
> >
> >Also nice to see the antenna-input/receiver-protection circuit using 
> >the neon bulb solution discussed here, in addition to an RF 
> >detection/auto switch-off  circuit.
> >
> >Copied some parts of the schematics and edited them a little to have 
> >an idea of what the circuits are; just as examples for my own better 
> >understanding.
> >No intention to suggest this for Alex. (or infringe on any 
> IP rights!)
> >
> >Thought I'd share them. (if they come thru the reflector......)
> >
> >73's,
> >
> >Henry
> >_______________________________________________
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> 
> Cecil
> KD5NWA
> www.qrpradio.com www.hpsdr.com
> 
> Cum catapultae proscriptae erunt tum soli proscripti 
> catapultas habebunt.
> (When catapults are outlawed, only outlaws will have catapults!) 
> 


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