K7IYP - Mike

Sonoita, AZ

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LATEST DEVELOPMENT -- TS-530 Modified for Plate-modulated AM

Information on Power Supply Failure and Repairs

Shown here is the current K7IYP station.    Left to right are:  a Kenwood TS-530S, MODIFIED FOR PLATE-MODULATED AM OPERATION, a Behringer 1202 FX mixer and the  Kenwood KAC-714 100W audio amp/modulator (under spkr). The top voltmeter and ammeter monitor the solar-charged batteries; below those is the Heathkit 2140 A wattmeter, and then right, an IC-2000 2m rig, and an Icom IC-720A HF rig.  Microphone is a Shure SM-58.

The AM mods to the TS-530 are detailed here.

CLICK HERE for a larger picture (approx 800 K).



This was the previous K7IYP Command Set station covering 3 bands: 160, 80, and 40 meters.

Receiver utilized a BC-453 as a tunable IF with 3 HF Command Set receivers modified for use as tunable converters.

A Navy CBY-52232 ATA transmitter was used for the 160 meter band with freq. coverage modified to 1800-2000 KHz. The 80/75 meter band was handled by a BC-457-A modified to cover 3500-4000 KHz and a BC-459-A completed the trio for 40 meter duty.

The entire station was powered by 12V deep cycle batteries charged by solar panels.

CLICK HERE for the complete description and larger picture.

The following photos show more details of this unique, vintage station.

The station control box brings together the switching and metering functions for the command sets as well as the microphone preamp and screen modulator circuit boards.  The box was constructed from sheet metal and plywood found in a roadside ditch.  The vintage Heathkit counter monitors transmitted frequency.

Click on photo for hi-res image, or here.

This is an inside view of the control box showing the mic. preamp, power amp using TDA2030 IC and modulation transformer.  Modulation is applied to the 1625 screens as originally designed.  RFC is necessary to quash power supply switching noise from entering preamp Vcc.

Click on photo for hi-res image, or here.



The old station receiver was a revamped BC-348-Q.  It was modified for double-conversion operation by adding a second mixer driven by a 2nd local  oscillator that uses the 1000 kc crystal from a BC-221 frequency meter. Additional IF selectivity and gain was then provided by the 85 kc IF strip from a BC-453 LF receiver. It has a 4W solid-state audio section.

Next two photos are L-network with Command set antenna relay. "Scroller" inductor wound on 2" poly pipe, note "knuckle burner" lead from coil into relay below crank on tuning cap. Feed-through made from old utility pole insulators and alligator clip "lightning arrestor". Rat Shack meter nec. for tune-up 'cause RF ammeter inop- thermocouple apparently kaput.

Click on photo for hi-res image, or here.

Click on photo for hi-res image, or here.

Click for mp3 file of KF7IYP signal of 24 Oct 10 as heard at K7JEB (860KB)

(Rather noisy -- 75-meter band going out in late morning)

2-meter FM is the only 24/7 communication mode available from the K7IYP QTH, the surrounding terrain blocking all cellphone and WiFi signals.  The 2-meter antenna system consists of an omni-directional, half-wave groundplane and a 5-element yagi.  The groundplane antenna is termed "The Big Gulp" from the creative recycling of a beverage container from the local 7-11 soda fountain as an ultraviolet-ray shield for the plastic parts of impedance-matching components (shown below).

Click here for larger image

The impedance-matching network at the base of the Big Gulp groundplane antenna.

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