Posted by
Edward R Cole on
Jul 08, 2012; 5:36pm
URL: http://elecraft.85.s1.nabble.com/KX3-Receive-Performance-Below-1500-kHz-tp7558831p7558856.html
Wayne,
Thanks for the quick reply. I have also determined that there is
reception down to 310-KHz when I use an antenna cut for 500-KHz. My
first test was quick and used my 80m inverted-V which resulted in
nothing being heard (maybe I did not have a good connection; it was
just a quick look). I saw useful receive levels which would lead me
to think use of my Clifton BC band reject filter ahead of a preamp
tuned for 470-KHz would probably restore good sensitivity without
subjecting the KX3 to overloading signals from the BC band (based on
what I see using this filter with the K3 and the SDR-IQ).
+10 dBm is quite sufficient for my transmit amplifier (a converted
100w NDB transmitter). I drive it with under 1mw direct from the K3
running in TEST mode output of the transverter output jack. I have
built a low-pass filter for 510-KHz which can be used for
transmitting (rated several hundred watts). WRC-12 stipulates ham
output on the 630m band will not exceed 1w ERP (and no more than 5w
ERP if permitted by certain national regulatory agencies). The ARRL
Experimental Group was licensed to run up to ERP=20w; my 100w
transmitter produces 4.15w ERP with my inverted-L antenna. So
considering the low efficiency of antennas that hams would use one
may only need something like 20w RF output. That is +43 dBm implying
the need for about 30-dB transmit amplifier for the KX3. Relatively
easy to do at this frequency (even a tube-type amp ckt drug out of an
old 1960-70 manual would work). Some of our experimenters have had
success converting stereo audio amplifiers into 500-KHz amplifiers
with suitable change of input/output transformers and bypassing changes.
Of course using a transverter is an option but that is a
builder-experimenter option, at present. I actually built one for
translating 10.4xx to 4xx KHz by use of a SBL-1 mixer and my 10-MHz
OCXO station freq. reference source. The K3 will operate in test
mode for running at 10.472-10.478 KHz. For other radios one would
chose a ham band such as 80m or 40m to translate down.
I will do some testing with my KX3 on transmitting at 470-KHz and
have in mind a transistor amp to provide 25w (which I may eventually
make if there is a market). Ham radio use of 472-478 KHz will
require FCC action to happen in the USA. WRC-12 approves use after
Jan 1, 2013.
73, Ed - KL7UW
At 07:49 AM 7/8/2012, Wayne Burdick wrote:
>Hi Ed,
>
>The KX3's spec also says, "Note: Sensitivity decreases gradually below
>1.5 MHz due to protective high-pass filtering...." We did this to
>ensure that the PIN diodes in the T/R switch are protected. A fairly
>large amount of attenuation is required by the time you get down to
>500 kHz or lower.
>
>We did do some transmit tests in the 470 kHz range. We can easily get
>+10 or possibly +20 dBm output at these frequencies, but you'd need an
>external filter/amplifier to obtain useful transmit power output.
>Given that, I would think that an external receiving converter that
>shifted the 0-1 MHz range up to 7-8 MHz on the KX3 would also be a
>good solution. The KX3 has transverter bands that can be set up for
>this application, allowing the VFO to read correctly when on this
>band. The ACC2 GPIO pin could be used to turn the external converter
>on/off.
>
>The K3 has the same high-pass filtering in the main antenna path as
>the KX3. But the K3 also provides a way to bypass the filter, by using
>the KXV3's RX ANT input (or the XVTR input).
>
>73,
>Wayne
>N6KR
>
>
>On Jul 8, 2012, at 12:22 AM, Edward R. Cole wrote:
>
>>If this is true then the spec on page 51 of the KX3 manual is very
>>misleading where is states:
>>"310 kHz - 32 MHz and 44-54 MHz..."
>>
>>I was looking forward to using the KX3 on the new 630m Ham Band
>>recently approved by WRC-2012:
>>472-478 KHz. The K3 operates down to 490 KHz but no lower so
>>unusable on the new ham band. The KX3 "appeared" to be the first
>>commercially mfd radio able to operate down there. If not then this
>>is a BIG missed opportunity.
>>
>>I use a Clifton Labs Z-10020 MW BC Band Reject filter (540-1700 KHz)
>>which rejects signals inside that band. Signals seen at -50 dBm are
>>reduced to the the -110 dBm noise floor, whereas the signals below
>>540-KHz are unaffected below about 515 KHz. I have used it with the
>>K3 and my SDR-IQ (which tunes to 500-Hz).
>>
>>There was discussion last fall that the KX3 might be capable of
>>transmitting on 630m.
>>I would like the official word on this before publishing my paper
>>reviewing the KX3 at MUD-2012.
>>
>>630m will remain the province of the "experimenter" if no commercial
>>"shelf-ready" equipment is available.
>>
>>
>>73, Ed - KL7UW
>>I run 100w into a 43x122 foot inverted-L on 600m under the license
>>WD2XSH/45.
>>------------------
>>Date: Sat, 7 Jul 2012 08:15:31 -0500 (GMT-05:00)
>>From: Mike Morrow <
[hidden email]>
>>Subject: [Elecraft] KX3 Receive Performance Below 1500 kHz
>>To:
[hidden email]
>>Message-ID:
>>
>><
[hidden email] >
>>
>>Content-Type: text/plain; charset=UTF-8
>>
>>A discussion of KX3 MF lack of sensitivity recently took place
>>on the KX3 list. The KX3 should not be considered really
>>usable below about 1500 kHz, as Wayne explsined:
>>
>>---- Original Message (from KX3 list)
>>
>>>I thought there was some advantage to AM BCB reception
>>>to be had with the KXAT3.
>>
>>If a KXAT3 is installed, harmonic images are attenuated,
>>but this has little effect on signal strength.
>>
>>>Why wouldn't the T/R PIN diodes be as well protected by
>>>high pass filtering that rolled off below 400 kHz rather
>>>than 1500 kHz
>>
>>The carrier lifetime of the diodes is roughly 1.5 microseconds.
>>This means that strong signals at the low end of the broadcast band
>>could cause IMD (IP2) if not attenuated. The HPF provides
>>about 20-30 dB of rolloff by this frequency, ensuring that
>>this isn't a problem. The KX3 is optimized for ham-band use
>>so this is entirely appropriate.
>>
>>Wayne
>>
>>
>>73, Ed - KL7UW, WD2XSH/45
>>======================================
>>BP40IQ 500 KHz - 10-GHz www.kl7uw.com
>>EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
>>DUBUS Magazine USA Rep
[hidden email]
>>"Kits made by KL7UW"
http://www.kl7uw.com/kits.htm>>======================================
>>______________________________________________________________
>>Elecraft mailing list
>>Home:
http://mailman.qth.net/mailman/listinfo/elecraft>>Help:
http://mailman.qth.net/mmfaq.htm>>Post: mailto:
[hidden email]
>>
>>This list hosted by:
http://www.qsl.net>>Please help support this email list:
http://www.qsl.net/donate.html73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
DUBUS Magazine USA Rep
[hidden email]
"Kits made by KL7UW"
http://www.kl7uw.com/kits.htm======================================
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html