The call letters W6IWI were first used by Kauko Hallikainen in the 1930s. See the
1938 Amateur Radio Callbook. The 1930s QSL card was similar to that shown above
(I may still have one of the originals somewhere). I
acquired the call in 2016. Prior to that, I held the call WA6FDN, and prior to that, WN6FDN. The WA6FDN
license was probably first granted in 1967 or thereabouts, with WN6FDN a year earlier.
WN6FDN started with a Heathkit DX-60 transmitter and a National NC-300
receiver running CW on HF. WA6FDN used a Viking Ranger transmitter running AM, CW, and RTTY on HF. RTTY used a
Teletype model 15 printer, and a model 14 typing reperf and transmitter distributor.
W6IWI now uses an SEA 245
running CW and SSB into an inverted V antenna in Arvada CO. VHF and UHF
FM are covered with a Baofeng UV-5R and a Wouxun KG-UV-6X
W6IWI HF Activity
The plot below shows a historic plot of W6IWI HF CW activity.
Recent activity (in the past day or so) can be viewed here. These are both generated by the
Reverse Beacon Network.
Power Line Interference Noise
Notes on resolving power line noise have been moved here.
Receiver AGC vs Input
To get an idea of signal strength, data was gathered on AGC voltage (actually AGC count captured from the EIA 485 bus between the radio and the control head)
versus receiver input level at the center of each band. A SARK-110
(thanks to Jack, KE0VH for the loan of this excellent instrument) antenna analyzer
was used as a signal generator to drive the SEA 245. The raw data is shown here. A plot of the data for 40 meters, as generated by
https://mycurvefit.com/ is shown below. This was generated with an auto-smoothed spline fit. It is extended down to the measured noise level
on the receiver (AGC count of 10 corresponding to an input level of -118 dBm. From this curve, the 40 meter noise level measured above (AGC = 118.2) corresponds to a receiver
input level of about -92 dBm which is 26 dB above the receiver internal noise. S9 is defined as -73 dBm with each S unit being a change of 6 dB. On 40 meters, an input level of -73 dBm gave
an AGC count of 184. The power line noise of -92 dBm is 19 dB below -73 dBm or 3 S units below S9. The power line noise is, therefore, about S6.
Based on the data above, a 30 dB increase in the linear region results in an AGC count increase of 98. This indicates we have 0.306 dB/count.
HF Station Details
An analysis of the previous antenna is located here.
- HF Transceiver - Seacom SEA 245. This runs 150W CW or SSB between 1.6 MHz and 30 MHz.
- Transmission Line (Transceiver to Antenna Tuner) - 25 feet of RG218XATC 50 ohm coax.
- Antenna Tuner - Seacom SEA 1630. Microntroller-based remote antenna tuner. The microcontroller switches a set of binary weighted inductors and capacitors
in and out of a pi network to match the antenna impedance to the impedance of the transmission line to the transceiver (50 ohms). Measures frequency at start of transmission. If frequency used before, tunes to it
within 20 milliseconds. If this is a new frequency, it tunes within 5 seconds. A short copper braid connects the tuner to an 8 foot ground rod.
- Tuner to Balun Transmission Line - About 5 feet of RG218XATC 50 ohm coax. This will typically have a high SWR on it.
- Current Balun - DX Engineering DXE-BAL050H10AT. 50 ohms. 5 kW CW, 10 kW SSB. Located a few feet from the tuner and at the bottom of the mast.
On the coax side of the balun, a lightning arrestor with a short copper braid to the 8 foot ground rod.
- Ladder Line, Balun to Antenna - About 27 feet of DX Engineering DXE-LL450-CTL 450 ohm ladder line connects the balun to the antenna.
- Mast - About 27 feet (7 sections) of
4 foot fiberglass mast. More sections are available, but it is difficult to erect on my own and probably needs some guying beyond that provided by the antenna.
- Antenna Center Insulator - DX Engineering DXE-UWA-KIT
- Driven Element - 33.33 foot insulated 14AWG wire sloping down to about 10 feet above ground on each end. One side goes over the roof of our house. The other side goes through a tree. Not quite balanced, but
the best I can do while staying clear of power lines. The 33.33 foot length should be resonant somewhere around 7 MHz. It is non-resonant on other bands, presenting a variable impedance to the antenna tuner.
Until the power line interference issue is resolved, most HF receiving is done using Web SDR. A truly amazing project that lets you listen to receivers around the world.
See here for a history of early web SDR hardware. In its basic form, a web SDR is a high speed ADC (for example, the
LTC2216 16 bit ADC running at 77.76 MHz) driving an Ethernet interface to a server computer. The server provides a user interface
to multiple users, demodulates the user chosen frequency, streams the resulting audio, shows a waterfall plot of the surrounding spectrum, and many other features. To me, this
is truly amazing! The web SDR may also decrease the Ethernet bandwidth requirements between the ADC and the server by only sending selected frequency ranges (bands). In this
case, digital down converters are included in the FPGA between the ADC and the Ethernet PHY. Just as in analog, a digital down converter multiplies the incoming RF by a "local
oscillator" and filters the output to the desired spectrum (and removing the image). The local oscillator is a direct digital synthesis sine wave generator (a phase accumulator
determines the phase of the local oscillator at each clock edge. The phase is passed to a sine lookup table to generate the sine wave local oscillator signal). "Mixing" is just
multiplication of the sine wave local oscillator with the incoming RF. The resulting product is filtered (often just a low pass filter) to remove the image and define the
received band. Resulting samples can now be down-sampled since the highest sampled frequency is lower than with the incoming RF. This reduced bitrate signal is sent over
Ethernet to the server for further processing. Again, truly amazing!
Contact me with any comments at email@example.com.