[Elecraft] Comparing the K2 to other rigs: background noise

Thu Nov 28 21:17:01 2002

Yeah... even if those who claim no advantage... just more or less even
performance... are right, it's still fascinating.  73... Ed

----- Original Message -----
From: "Eddy Avila" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 28, 2002 11:50 AM
Subject: Re: [Elecraft] Comparing the K2 to other rigs: background noise

> To All....I find it absolutely fascinating that we're comparing a rig that
> sells for way less than $1,000 to those selling for around $3,000 (and
> that's without additional accessories, ie: the necessary additional
> filters!!!) .....and..... the rig for less than a grand keeps beating
> them!!!
>
> Who's getting their money's worth here, eh?
>
> 73's all....k6sdw
>
>
> >From: Wayne Burdick <[email protected]>
> >To: Christoph Rheker <[email protected]>
>
> >Christoph Rheker wrote:
> >
> > > ... My TS870 sounds in most cases like
> > > there is some kind of life on the bands. For example, during
> > > evenings on 15/20m there is always some kind of background noise.
> > > When I switch to my K2, there is no such thing!
> >
> >Chris, the K2 is quieter than the TS870 because it has a single I.F. and
> >less
> >overall gain. Because of this, really low-level band noise won't activate
> >the
> >K2's AGC. (The TS870 is probably "in the AGC" with normal band noise,
even
> >on 10
> >meters, because of all of the excess gain.)
> >
> >But I want to make sure I understand what you mean by "no such thing" in
> >reference to band noise. When you connect a resonant antenna to your K2
on
> >any
> >band, including the higest bands, you should hear an increase in
background
> >noise. This should be true even when there's no unusual atmospheric noise
> >on the
> >band. Of course the effect will be much more dramatic if you're using a
> >wide
> >filter bandwidth.
> >
> >I'll give you an example, using a test I just did on two different K2s:
> >
> >1. Switch to one of the highest bands (15 m up), USB (FL1 = OP1 = about
2.1
> >kHz bandwidth).
> >
> >2. Disconnect the antenna.
> >
> >3. Connect an AC voltmeter (DMM set to lowest AC volts scale) across the
> >headphone jack (use a plug only, no headphones)
> >
> >4. Turn AF GAIN and RF GAIN all the way up, and turn the preamp ON.
> >
> >5. The AC voltmeter should indicate around 20-30 mV RMS or higher. This
is
> >the
> >baseline (no antenna) noise, generated within the K2 itself. It will be
on
> >the
> >low end of this range if you have a KAF2 audio filter installed, or if
you
> >use
> >the CW filter rather than the filter on the KSB2. The narrower the filter
> >setting, the lower the voltmeter reading will be.
> >
> >6. Connect a resonant antenna, preferably the lowest-noise antenna
> >available for
> >the selected band.
> >
> >7. The AC RMS voltage should go up by a factor of two (6 dB) or more. (If
> >it
> >goes up a lot more than this, it could be because there's a signal on the
> >frequency you're tuned to, or because there's a lot of atmospheric
noise.)
> >
> >
> >I did this test on two different K2s. On the one with a KAF2 installed,
the
> >noise on 10 meters went from 20 mV to 50 mV RMS when the antenna was
> >connected.
> >On another K2 with no KAF2, and using the CW filter set for 2.20, the
noise
> >went
> >from 35 mV to 70 mV RMS.
> >
> >If you do this test and discover, for example, that both the antenna off
> >and
> >antenna on conditions show much lower AC voltages at the headphone jack,
> >you
> >could have a problem with your K2. Try turning AGC off (hold PRE/ATTN and
> >AGC
> >together) and see if the results differ significantly. If it turns out
that
> >the
> >AGC threshold is set too low, you can cure this by reducing the value of
R1
> >on
> >the Control board. If the signal amplitudes are too low even with the AGC
> >threshold set correctly, it could be due to excess loss in the band-pass
or
> >crystal filters.
> >
> >If you do the same test on the TS870 you'll no doubt see larger antenna
> >off/on
> >figures due to the much greater gain in the receive path. But this is to
be
> >expected; the K2 design aims for both good sensitivity and low current
> >drain, so
> >low-current devices are used at every stage, and there are far fewer
> >stages.
> >
> >
> > > One problem with I don't like is the S-Meter activation issue. With my
> > > antennas I often get S7 S-Meter readings without any "real" signal
> > > present. Yes, I have done the RFC11 mod. No, I have not done the mod
> > > to the front-end band pass filters. Another item on my list.
> >
> >The narrower filters should help quite a bit.
> >
> >73,
> >Wayne
> >N6KR
>
>
> _________________________________________________________________
> MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*.
> http://join.msn.com/?page=features/virus
>
> _______________________________________________
> Elecraft mailing list: [email protected]
> You must be a list member to post to the list.
> Postings must be plain text (no HTML or attachments).
> See: http://mailman.qth.net/mailman/listinfo/elecraft
> Elecraft Web Page: http://www.elecraft.com
>
>