Re: 630 MHz transmit and receive using the K3s or modified K3

[Edward R Cole]

Thanks Wayne.

I have been using my K3 (SN 4043) purchased in 2010 on 495 to 502 KHz
from 2012 as part of the ARRL Experimental 500-KHz Group using
experimental license WD2XSH/45.  Primarily using std CW or WSPR at
about 4w ERP.  Our experimental license specified using power up to
20w ERP so one had to calculate from EIRP.

New ham regs now use EIRP which is typically shown if modeling an
antenna using EZNEC.  I modeled my 43-foot high by 122-foot long
inverted-L which results in impedance at 503-KHz of Z = 0.83 -
j886.5.  I measured the antenna using my modified MFJ-269B at 18 - j0
after adjusting the base loading coil for resonance.

Then get total radiated power from TPR = 0.83/18 * 100 = 4.6w  (note
my amplifier is running 100w into 50-ohm load).
 From EZNEC-5 antenna gain = 1.48 , EIRP = 4.6 * 1.48 = 6.8w
ERP = 6.8/1.64 = 4.15w.  Thus my antenna efficiency is only 4%.

My unmodified K3 will only operate down to 490-KHz but I have the new
synth board and mod kit for the KBPF3 to install which will extend
operation to the new 630m band (472-479 KHz).  I was able to get 1mw
output with my unmodified K3 in TEST which I drove a modified NDB
transmitter to 100w.  The NDB is an aircraft CW beacon with dual xtal
LO separated by 400-Hz.  By CW keying that shift it produced a mcw
signal.  I removed he LO and simply capacitively couple about 0.1 mw
to fully drive the three stage amplifier.  I was able to pick up the
NDB surplus for $40 which is self-contained with 55v PS.  I expect
them to quickly be snatched up by 630 ops.

I home made a 10-inch by 11-inch base coil wound 1/4 inch spacing on
a plastic form to provide loading.  I have two taps which are moved
between winter and summer soil conditions which shift the ground
resistance enough to shift resonant frequency.  I got about 5-Hz SWR bandwidth.

Previous to the new mods, I ran a SDR-IQ receiver and only
transmitted with the K3.  I have picked up the CW signal from an
Oregon station and my signal has been detected as far as Buffalo, NY.

AFAIK only two commercial radio will operate on our new ham
band:  K3s (and mod K3) or theTS590.  This opens a market for
entrepreneurs to provide preamps, amplifiers and transverters.  Puts
Elecraft ahead of the "crowd", again!

NOTE:  FCC requires pre-registering with UTC before operating on
630m.  Its a 30-day process.  I'm waiting for my approval.



73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   [hidden email]

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[wayne burdick]

Thanks for the info, Ed. I'm going to have to figure out my own antenna for this band.

Wayne
N6KR

----
http://www.elecraft.com

> On Sep 17, 2017, at 12:01 PM, Edward R Cole <[hidden email]> wrote:
>
> Thanks Wayne.
>
> I have been using my K3 (SN 4043) purchased in 2010 on 495 to 502 KHz from 2012 as part of the ARRL Experimental 500-KHz Group using experimental license WD2XSH/45.  Primarily using std CW or WSPR at about 4w ERP.  Our experimental license specified using power up to 20w ERP so one had to calculate from EIRP.
>
> New ham regs now use EIRP which is typically shown if modeling an antenna using EZNEC.  I modeled my 43-foot high by 122-foot long inverted-L which results in impedance at 503-KHz of Z = 0.83 - j886.5.  I measured the antenna using my modified MFJ-269B at 18 - j0 after adjusting the base loading coil for resonance.
>
> Then get total radiated power from TPR = 0.83/18 * 100 = 4.6w  (note my amplifier is running 100w into 50-ohm load).
> From EZNEC-5 antenna gain = 1.48 , EIRP = 4.6 * 1.48 = 6.8w
> ERP = 6.8/1.64 = 4.15w.  Thus my antenna efficiency is only 4%.
>
> My unmodified K3 will only operate down to 490-KHz but I have the new synth board and mod kit for the KBPF3 to install which will extend operation to the new 630m band (472-479 KHz).  I was able to get 1mw output with my unmodified K3 in TEST which I drove a modified NDB transmitter to 100w.  The NDB is an aircraft CW beacon with dual xtal LO separated by 400-Hz.  By CW keying that shift it produced a mcw signal.  I removed he LO and simply capacitively couple about 0.1 mw to fully drive the three stage amplifier.  I was able to pick up the NDB surplus for $40 which is self-contained with 55v PS.  I expect them to quickly be snatched up by 630 ops.
>
> I home made a 10-inch by 11-inch base coil wound 1/4 inch spacing on a plastic form to provide loading.  I have two taps which are moved between winter and summer soil conditions which shift the ground resistance enough to shift resonant frequency.  I got about 5-Hz SWR bandwidth.
>
> Previous to the new mods, I ran a SDR-IQ receiver and only transmitted with the K3.  I have picked up the CW signal from an Oregon station and my signal has been detected as far as Buffalo, NY.
>
> AFAIK only two commercial radio will operate on our new ham band:  K3s (and mod K3) or theTS590.  This opens a market for entrepreneurs to provide preamps, amplifiers and transverters.  Puts Elecraft ahead of the "crowd", again!
>
> NOTE:  FCC requires pre-registering with UTC before operating on 630m.  Its a 30-day process.  I'm waiting for my approval.
>
>
>
> 73, Ed - KL7UW
>  http://www.kl7uw.com
> Dubus-NA Business mail:
>  [hidden email]
> ______________________________________________________________
> 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.html
> Message delivered to [hidden email]

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