[Elecraft] Combo pre-amp

[Gary Gregory]

Hi ian,

Gee thanks for the insight to your attempts on an internal pre-amp.

I imagine that the lack of sensitivity on 12/15M has appeared after
production also so again the position would be the same from Elecraft.

It is a pity that to correct this can only be remedied with an external
device. If they ever produce a remote 10/12M preamp that could be sat a
foot or so away from the K3 this would help in my case but may not suit
home stations and others. I realise I am most likely in a small minority
here and I accept that without reservations.

I would rather pay for what I need rather than a combo including 6M which
is of no use to me.

73

Gary

On 26 May 2013 19:39, Ian White <gm3sek at ifwtech.co.uk> wrote:

> Joe, Gary and Joe again:
>
> >>>
> >>> I agree that an internal preamp (or premps) would be ideal.
> However,
> >>> in addition to the preamp(s) Elecraft would need to provide
> *another*
> >>> design for the KXV3A - one that switches the RX ANT IN/OUT
> >>> connections to internal jacks - as neither the original KXV3 or
> >>> current KXV3A have that capability.
> >>>
> >
> > > let's not let that technical inconvenience reduce in any
> > >way my hope for a cure to my sometimes demented desires....:-)
> >
> >I'm not saying it isn't possible ... takes one additional relay and two
> >connectors.  There are even couple unused control lines on the KXV3A
> that
> >could be used to control the added relay and switch bands (10/12 and 6
> M)
> >if necessary.
> >
>
> Been there, tried that.  I tried two different ways to retrofit an
> internal preamp for 6m, and neither of them worked well enough to keep.
>
> The problem is that any modification has to work within the very tight
> space behind the rear panel of the KXV3 module. There is >>barely<<
> enough space to install a tiny PC board behind the RX ANT IN and RX ANT
> OUT connectors, with very tight limits on what can be included on that
> board. The track layouts had to be designed with a step size of 0.025in
> and in some places the tolerances were even tighter than that.
>
> Board #1 used a single subminiature DPDT relay and included a very
> simple wideband preamp; but the single relay gave insufficient isolation
> to prevent the preamp from oscillating out-of-band. There wasn't enough
> space on the board for two relays, tuned circuits or any additional
> shielding and decoupling; and it was impossible to make any further
> tweaks without completely extracting the KXV3 module. Board #2 was
> simpler, this time with two DPDT relays for improved port-to-port
> isolation, and with two coax fly-leads that were long enough to reach
> into the space above the KRX3 module (which Elecraft had reserved for
> the 144MHz transverter). That allowed me to use a fully shielded 6m
> preamp which gave a dramatic improvement in sensitivity - but now the
> VFO encoder noise made it impossible to tune the band! I believe that
> new problem was due to the use of two different grounding points, at the
> KXV3 and on the top cover of the KRX3, and I couldn't see any way around
> that.
>
> At that point I gave up on the idea of retrofitting an internal 6m
> preamp. Elecraft could have included it at the initial design stage, of
> course; but if my reading of history is correct, the demand for greater
> sensitivity on 6m came >>after<< the K3 had been launched on the market.
> By that time the internal hardware design was already locked down, so I
> can fully understand why Elecraft were obliged to produce the PR6 as an
> external add-on.
>
> Wayne has acknowledged that the K3 can sometimes be lacking in
> sensitivity on 6m, and has stated that the external PR6 module is
> Elecraft's solution.  I wouldn't expect that position to change
> significantly.
>
>
> 73 from Ian GM3SEK
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>



-- 
*Gary - VK1ZZ
Skype: Gary.VK1ZZ
Motorhome Portable
The Shack*
*Elecraft K3
P3 Panadapter
KPA500FT
KAT500FT**
KX3-K
*