Monday, June 03, 2013

ILER 20 QRP MODS

 


My Iler 20 is finally oparational. The IF has changed to 4.000 MHz and the vxo has 10.250 MHz crystals.(Ebay)  The VXO coil now holds 64 turns no.26 (0.31mm) magnet wire and the tuning range with the polyvaricon is 14.129 - 14.246.4 MHz  with a stable signal .  C15-C18 in the 4 MHz cristal filter  are replaced by10 pF  to give a clear audio on rx and tx. As you can see, even the microphone was to bulky and was replaced by a home made model. Audio sounds verry good and the rf power is 6 Watts PEP at 13.8V. Also C28 was lowered to 33nF to get more high tones in the audio output, but that's a question of personal taste. I found a perfect little speaker named : Visaton K 50 WP , 3 Watt 8 Ohm art.nr.:2915 that gives a real boost to the audio. In order to lift the microphone  input, R6 was changed to 470K. The mini counter comes from Hendricks QRP and was chosen for it's low power consumption and small size . Some humming interference can be caused by the display multiplexer of the counter but a small filter takes care of that:

The cabinet was ordered from Qrp Project in Berlin http://www.qrp-shop.biz/epages/qrp-shop.sf/de_DE/?ObjectPath=/Shops/qrp-shop/Products/Kuehlr168x110x54  It fits the board like a glove . For smooth tuning a 1:10 ball drive is added. Because of the 180 degree tuning range of the polyvaricon, only a 1:5 reduction remains. Ball drive reductors:
 http://www.ebay.com/sch/Radio-Communication-/1500/i.html?_from=R40&_nkw=ball+drives




The latest boards have a litle bug causing a shortcut to ground of C37 and R22 .This prevents the noisefilter from doing his job.  Before installing C37, take a  4mm drill and make a smal cone in the board surface to remove the ground connection . The new Iler kits have a new pcb without this problem.
I noticed that the noise filter even causes the noise levell to rise , so i desided to remove C37 and R22 permanently.
The BD135 driver heats up at long qso's . This heat can cause the standard vfo to drift ,especially in vertical use.  Connect the transistor to the cabinet  by means of a u-shape alluminium strip for better cooling.

The Iler kits  represent a modern and compact, easy to build alternative, to the Bitx and Taurus.
More info about this nice kit :  http://ea3gcy.blogspot.nl/

Update 25/11/2014
 Today i installed the Iler DDS generator. I expected some digital noise but surprisingly the audio stayed verry  clean after a small mod. without any spurs or birdies. I kept the old counter for this made the DDS unit smaller and easyer to mount. At trials the new counter was only atached for the DDS setup in the generator mode , from 10.000 - 10.350 MHz without IF ofset . The IF ofset is already programmed in the Hendricks counter. Once the DDS was programmed the bleu Iler counter was removed.
Tuning is verry smooth and accurate with the provided step levells.
Next mod wil be a simple NE 555 tone generator to generate a carrier for swr readings.

POPPING AUDIO MOD.
Despite of a reasonably good working lf AGC, verry strong signals can produce a loud popping sound due to a massive overload of the LM-386 input. 2 Bat-85 Skottky diodes in anti-parallel over the 10K-B volume potentiometer and a 10K resistor between C32 and the potentiometer cure most of the problem.
The extra parts can be mounted directly on to the potentiometer.

DDS POWER MOD
The DDS adds some noise to the audio. A small 100uH choke and a capacitor to ground at the DDS power pin are the solution 


Iler base station 20m.  70 Watt

Disclaimer:I'm not responsable for any damage due to improper reproduction of my projects.

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