Joe Subich, W4TV-3 wrote:
>
> No, you are asking for a lower MDS than on HF without regard to
> the overall performance of the radio in terms of dynamic range.
> There are many K3 users who rely on dynamic range and freedom
> from interference on HF that blows away any of the radios you
> list. Even on six meters they K3 dynamic range far exceeds that
> of the YaeComWood radios you cite.
>
> Above all, your information concerning sensitivity is just plain
> wrong. The ARRL Lab data shows the FT-2000 sensitivity (MDS) on
> 50 MHz (preamp off) at -122 dBm ... and measures the K3 MDS at
> -128 dBm (preamp off). Similarly, with "preamp 1" the FT-2000
> measured at -131 dBm vs. -135 dBm for the K3 (internal preamp).
> If you want to compare the TS-2000, its MDS (preamp off) is -127
> dBm rising to -142 dBm with preamp on but with a dynamic range
> of only 66dB (worse than a 30 year old FT-101!). To complete
> your comparisons, the Icom has the same -136 dBm MDS with
> "preamp 1" and a dynamic range of only 74 dB. I would say
> that Eric and Wayne made exactly the right design decisions
> with a -136 dBm MDS and 100 dB dynamic range.
>
> Yes, the K3's MDS is slightly worse on 50 MHz than on 14 MHz
> due to the additional filtering in the front end. However, even
> with a lousy vertical antenna, my receiver noise always increases
> by at least 2 dB when switching from a dummy load to the antenna.
> A second higher gain, preamplifier would be of no value to the
> vast majority of K3 users ... in fact it would likely be counter-
> productive as it would harm the excellent dynamic range of the
> radio. Why should those who have no need for the ultra high
> sensitivity on a band they rarely use subsidize performance that
> benefits only a limited few?
>
>
Because the K3 is advertised as a "high performance 160-6m transceiver", not
a "high performance 160-10m transceiver with 6m coverage at a lower level of
performance."
I don't see why good 6m receive performance is necessarily incompatible with
good HF dynamic range. Preamps can be switched out, and some Japanese made
radios I believe have separate preamps for their VHF bands. Wayne has
explained why the sensitivity on 6m is not as good as on other bands and it
is clear that this is as a result of a design compromise made on the basis
that HF performance was paramount. As someone else in this thread pointed
out, this compromise is not something that is widely publicised, and it
might have affected some people's purchase decisions. I might not have sold
the 6m transverter I used with my K2 if I had known that the K3 was not
going to have the superior performance on all bands that I thought it was
going to have.
Still, I'm glad to hear from other contributors to this thread who have said
that they have found the stock K3 just fine. Given that I'm in a fairly
noisy urban environment, perhaps the preamp would have been a waste of money
for me anyway.
-----
Julian, G4ILO. K2 #392 K3 #222.
http://www.g4ilo.com/ G4ILO's Shack http://www.ham-directory.com/ Ham
Directory http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3
--
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