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K0SF

Steven J Fraasch

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K0SF

Accepts QSL via:
LoTW: NO
e-qsl: YES
mail QSL:YES

lookups: 16296


The picture is of Nancy (XYL) and me in Chicago in 2010.

I am a RF/hardware/systems engineer. I design ablation generators at Atrial Fibrillation (AF) Solutions, Medtronic Cardiac Rhythm & Heart Failure, Mounds View, MN.

I was originally licensed as WN0DSJ in Feb 1971. I have been K0SF since 1977. I enjoy home-brewing, DXing, and some contesting. I paper QSLL 100%. I am also on EQSL.

My most recent DX QSL mailing was August 30th, 2016. If you want a QSL card and you're in a hurry, just request one via email; no QSL is necessary. As long as you're in the log, I will mail it out (US direct, DX via the ARRL outgoing QSL bureau). Please do not send $, stamps or IRCs.

73, Steve, K0SF

Antennas (My designs using K6STI "AO"):

6m: 6 el yagi, 20' boom, 90'

15m/10m: 4/6 el yagi, 30' boom, 83'

17m/12m: 4/4 el yagi, 20' boom, 71'

30m/20m: 2/6 el yagi, 44' boom, 124'

40m: Inverted vee, 123'

80m (2016): 2 phased (1a/0, 1a/115) inverted vees spaced 60' @ 96' height

160m (2017): 2 el phased array (tower shown & 2nd radiator)

Tower: Phillystran guyed Rohn 55G with K0XG rotating base and rings

Rotor Controller: CDE Ham-II modified w/ Idiom Press Rotor-EZ and "H" bridge (sans relays)

Rig:

Yaesu FT-1000MP Mark-V transceiver

Yaesu FTV-1000 6m transverter

SPE Expert 2K-FA amplifier

Electro-Voice 664 microphone

N3ZN ZN-5 cw paddle

N1MM logging software

Collins KWM-2 transceiver w/ DX Eng Speech Processor & D-104 Mic

Collins 30S-1 amplifier

2016: Collins 20V-3 AM Transmitter (see below)

75m 2 Element Inverted V Phasing Network (note grey box near top of tower) and schematic:

My software,K0SF_RFWare in Matlab (available on request w/ disclaimer) uses ABCD network parameters to find the values. The software performs the same RF analysis functions thatKeysight's Advanced Design System (http://www.keysight.com/en/pc-1297113/advanced-design-system-ads?cc=US&lc=eng) does, but in a clutzier, text driven way.

I start the design using NEC2 (or NEC4), and determine the basic topology for the phasing network. Yet, given differences between a real antenna and a model, in order to achieve the best array performance such as gain, F/B, and SWR, it is better to go outside with the network analyzer and measure the self and mutual impedances. For that I use a miniVNA PRO(http://miniradiosolutions.com/minivna-pro/) network analyzer atopthe tower (see below), along with terminations that effect opens and shorts at the inverted vee terminals (needed for coupled and uncoupled measurements).

miniVNA PRO connected to the east inverted vee feedline. Inductance (2.83 uH) used to effect an "open"at the west inverted vee terminal @ 3730 KHz. Capacitance (45.2 pF) used to effect a "short" at the west inverted vee terminal @ 3730 KHz.

The miniVNA has a distinct advantage over other portable analyzers: it can be used remotely with Bluetooth and an Android phone app written by YO3GGX. I have even dangled the miniVNA from coax 100' above ground so that I could get driven element data from my 6M beam ! Once back in front of the PC, I use RFWare to "rotate" or de-embed these results by the transmission line length and loss to reference the results at the inverted vee feedpoints. Last, given element currents and relative phase, I use this final set of data to tweak the values using RFWare. Refer to Antenna Theory:Analysis & Designby Balanis or Forrest Gehrke, K2BT's "Vertical Phased Arrays," a 6 part series appearing in Ham Radio Magazine in 1983 and 1984. I have the article series (available on request) in pdf format.

Here's my Collins 20V-3 or "KPIG" from a 1450 KHz station of the same call letters (now KMRY) in Cedar Rapids, IA. It's on the air in my workshop. According to Skip, K7YOO who recovered it, the whole thing was under water ! It was a victim of the 2008 Cedar Rapids flood. But, underneath the crud, there was a nice looking broadcasttransmitter (I have certainly seen worse neglected and stored away in barns). The first RF came out of it Sunday, 29 Jan 2017 and the first audio on Heavy Metal Night, 4 Feb. It was a 5 year on-again-off-again project (mostly off).

It is set up for 160 - 40m, but I want to add up to 15m. I will probably re-do the Pi-L as a Pi-net to make the tank coil relay switching simpler (2x relays required for Pi-L). The prototype controller is based on an Arduino UNO microcontroller and interface board (sitting on the workbench to the left). It handles the T/R cycle: Tx: Antenna -> FT-1K MP 5watt drive -> Plate HV - > Audio Unmute where the sequence is reversed going back to rx. It also has a rotary encoder to allow control of the 20V-3 from my desk; eventually I'll add stepper motors for the tuning caps and a relay controlled interstage coupler between the 807 and the 4-400 finals. Last, the UNO via the interface board can also read the meters and report that. Should a $5 UNO control a broadcast transmitter ? Hmmmm ... why not ? I have the code and schematicsfor those interested; drop me an email.

Otherwise, I am using my Yaesu FT-1K MP Mk V transceiver to provide the ~ 5W oscillator drive to the 807 driver and to perform rx functions (great rx AM). The audio gear is sitting to the right of the FT-1K MP: A Behringer T1953 hybrid pre-amp and a CRL Systems MBL-100 compresser/limiter from Robert, W0VMC. Thanks to Skip, K7YOO for a great find and a too-fair deal, as well as Dennis, K0EOO and W0VMC for advice along the way. If you have a chance at an old BCST transmitter, don't pass it up; a conversion is a super fun project although some work is involved. Let me know if you have a Collins 20V-2, 21E, or RCA BTA-1 collecting dust.

73,

Steve



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