[Elecraft] An idea for the K2

[Stewart Baker]

Any form of increasing the mic gain internally (eg rf speech clipper) needs to 
be carefully thought out. The microphone signal routing and earthing from the 
front panel socket thru the RF board and into the KSB2 is far from ideal.
Common mode, series mode - the lot - RF feedback is the likely result.

A groundplane board with the crystal filter laid out to reduce blow-by may be 
the way to go. A tin can over the whole assembly may help. The biggest hurdle to 
overcome in making changes to the KSB2 is interfacing with the existing firmware 
which is far from straightforward. 

73
Stewart G3RXQ

On Wed, 2 Mar 2005 08:11:54 -0000, Geoffrey Mackenzie-Kennedy wrote:
> Intersting ideas. If you did enlarge the SSB board to get all the bits in,
>
> in which directions would you enlarge the exixting board?
> IMHO it would be essential to contain the "new" board in a 'tin' box in turn
> mounted on metal, which raises the question of access to test points etc on
> the RF board, but a solution might be available.
>
> If you are considering some form of RF Clipping processing, you will need a
> second 'IF Filter' anyway. Although some people have got away with it, it is
> not a good idea to clip a DSB signal as produced by the balanced modulator.
> A lot of weird gurgles can result.
>
> As far as basic SSB 3db bandwidth is concerned, my personal preference when
> using small ladder filters, less than 8 crystals, is for a bandwidth between
> 2.0 kHz and 2.2 kHz. Although wider filters can sound nice, usually the
> filter's lower sideband skirt suffers to some degree (upper skirt if
> crystals in shunt connection). The result can be anti-social. Having said
> that, it is possible to build ladder filters with bandwidths around 5kHz at
> 5MHz, but various circuit trickery is involved and the skirts are a bit
> wide.
>
> Good luck with the project.
>
> 73,
> Geoff     GM4ESD
>
> ----- Original Message -----
> From: <WA2JJH at aol.com>
> To: <elecraft at mailman.qth.net>
> Sent: Tuesday, March 01, 2005 10:07 PM
> Subject: [Elecraft] An idea for the K2
>
>> For $89 the SSB board certainly gives you the most bang for the  buck.
>> I see a 2.6khz up grade option is offered.
>>
>> I noticed a larger SSB board would fit. I am going to experiment on the
> SSB
>> board.
>> I am trying to get an RF speech proc. AM mod/demod . perhaps a socket to
>> take an auxillary group of xtals. for a 2nd 7 pole filter, Perhaps even
> passband
>> or IF shift.
>>
>
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