Ron Spencer wrote:
Anyone else notice (and I know this will be difficult with hardly any
openings) that the sensitivity of the K3 on 6 is down? Compared to the
746 I
have it seems down quite a bit (even with the K3 preamp on).
Ron,
The K3 is optimized for high dynamic range. For example, it has 40 dB
higher blocking dynamic range and 25 to 30 dB higher IMDDR3 than the
IC746. It also has narrow ham-band filters, and the one for 6 meters is
triple-tuned, having about 1 to 2 dB higher loss than a double-tuned
filter.
The IC746 *does* have a low-noise second preamp that is often used on 6
meters, improving MDS to around -142 dBm (from the QST review). To
achieve an MDS this good on 6 meters in the K3 -- with its narrow
band-pass filters -- requires a preamp at a different point in the
signal path: inserted between RX ANT IN and OUT. This bypasses other
loss sources including the KAT3, low-pass filters, and T-R switch.
We've designed a dedicated 6-m preamp for this purpose. It's very
small, and has its connectors spaced so it can be directly connected to
RX ANT IN/OUT. Measured MDS on 6-m with the preamp patched in is around
-142 to -143 dBm. It can be switched in automatically on 6 m only by
the K3. It also includes a bypass relay so you can still use a receive
antenna for other bands.
I'm not sure when the new preamp will available. But if you're
interested in field testing one, please send me an e-mail.
tnx
Wayne
N6KR
---
http://www.elecraft.com
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