[Elecraft] K3 6-meter Performance Question

[Stewart Baker]

I have just finished putting together, and testing a 6m preamp kit 
from Down East Microwave. As I use the RX Ant input on the lower 
bands, and not wanting to put in a relay, I have made up a 
Diplexer to separate out the 2 signal paths.

Although the arrangement is a bit of a lash up it has proved the 
concept, and it's worth during a short 6m opening the other 
evening.

Without the preamp I noticed no discernible different in the K3 
noise level when connecting the antenna. With the preamp I get 
about an S2-3 indication.

More importantly signals which were there but not readable, with 
the preamp they gave 100% copy.

I think that my present preamp gain at around 22dB  is a little 
excessive, so I will drop it back to about 15dB or so.

Before I get swamped with requests etc, I should stress that my 
arrangement is not really reproducible, and you should wait until 
Elecraft releases their preamp solution.

Y.M.M.V

73
Stewart G3RXQ


On Thu, 3 Jul 2008 08:50:03 +0100, Ian White GM3SEK wrote:
> On Tuesday, Dick K5AND wrote:
>
>> Ciao, from CY0X, Sable Island.....
> [...]
>
>> Since it is so easy to switch out the outboard preamp, we have 
frequently
>> done this on some of the weak sigs just to see if we could 
still hear them.
>> In many cases we could hear them Q5 with just the internal 
preamp. Ian,
>> GM3SEK, et al, have pointed out that the stock radio NF is 
somewhere in the
>> 8-10db range, which is not stellar as six meter radio specs go. 
Nonetheless,
>> you'd be surprised at how many weak sigs we can still hear with 
only the
>> internal preamp engaged.
>>
> That's not surprising at all, as the K3 is only slightly lacking 
in
> sensitivity on 6m. But contrary to other reports from users in 
very
> quiet sites, my stock K3 can NOT hear background noise at 50MHz.
>
> Before making that statement, I took a couple of days to confirm 
that
> nothing else is wrong with the system. Receiver sensitivity 
meets
> Elecraft's 'typical' specification with a few dB to spare. 
Feeder loss
> was re-measured. And above all, I re-confirmed that my old 
IC-746 CAN
> hear background noise from the same antenna/feedline with a 
comfortable
> 3-5dB margin.
>
> A good operator like Dick can often make up for a few dB lacking 
in
> signal/noise ratio... but only at the expense of greater 
operator
> fatigue, and with the knowledge that some marginal QSOs *will* 
be lost,
> when a more sensitive receiver could have pulled them through. 
That is
> precisely why the receiver at CY0X has a prototype Elecraft 
preamp.
>
> One small correction: Elecraft's specification for a typical MDS 
(noise
> floor) of -136dBm in a noise bandwidth of 500Hz corresponds to a 
noise
> figure of about 13dB (significantly more than 8-10dB). Cutting 
through
> the technicalities, at a genuinely quiet 6m site that deficit 
*is*
> noticeable - a gap in the K3's otherwise all-round excellence.