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 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:
> dubus...@gmail.com
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