Photo 3 & Photo 4. The PCB assembled and tested. A suitable enclosure is the Hammond 1590TF.

1.8 MHZ HPF Complete Built & Tested in Hammond Box - EUR 120.57 + s&h

1.8 MHZ HPF PCB Built & Tested without box and connectors EUR 84.45 + s&h

1.8 MHZ HPF PCB, with factory soldered capacitors, DIY the inductors. Toroids and wire supplied - EUR 71.67 + s&h

Photo 6 . Consequences of a poor mechanical design (...mid-night engineering)!

The PCB needs a cut in order for someone to manage placing the bottom washers and nuts for the chassis connector. Because the PCB cannot be placed after placing the connectors. The PCB design is now corrected with an opening so the bottom nuts can be inserted using tweezers. Another solution could be threading the connector holes on the enclosure's wall but since the cables we use are heavy, and the wall thickness is only 2.5 mm, it is a better decision to place washers and nuts to secure the connector on the wall tight.

1.8 MHZ High-Pass Filter

   2.5 KV and 3KV NPO Capacitors

   High Current Toroids

   Good up to 54 MHZ

​   0.4 dB max loss on 160m band, -80 dBc @ 1 MHZ

    For the RX only version

    please see below

Fig. 2. The Return Loss over the frequency range of a prototype, including SWR plot  A .pdf plot is available by pressing the red button.

It is made with the same schematic like the high power version, but with low power components. It is capable only for RX. Sold with an aluminum enclosure with SMA connectors, fully tested. -3dB @ 1.8 MHZ, then minimum loss up to 54 MHZ and more.

The prices do not include 24% Greek VAT applicable only to individual buyers from European Union. 

The prices do not include 24% Greek VAT applicable only to individual buyers from European Union. 

LEFT:  The output caps failed. Maybe because of  slightly higher VSWR on 3.5MHZ. Power level 2100 W.

The shipping cost is EUR 3.99 for total value under EUR 9.99, EUR 7.99 for total value under 49.99, EUR 11.99 for total items value under 99.99, EUR 15.99 for total value under 199.99 and free for total value grater than EUR 200.00. The shipping is with registered mail with tracking info and delivers to USA, Australia in about a week to 12 days max, or less than a week for Europe. 

Inexpensive Rx-only version

Fig. 1. The frequency response of a prototype, but because of the poor dynamic range of the cheap VNA used,  the higher attenuation values under 1.3 MHZ cannot be measured.  A .pdf plot is available by pressing the red button.

​Fig. 1

​Fig. 3

Fig. 3. The Schematic Diagram of the filter showing part values.   A .pdf plot is available by pressing the red button.

​Fig. 2

Photo 5 .The PCB spacers are 18 mm in height with inner thread for M3 screws. The empty PCB can be used as a template for marking the holes. It should be centered vertically and horizontally on the bottom wall of the enclosure at first. The height of the center pin of the chassis connectors is 18 mm for the spacers  + 1.6 mm for the PCB thickness + 1.7 mm for the half of the center's pin dia, + 2.5 mm for the box wall thickness if you are measuring from outside. This way, the center pin will be found placed exactly on the PCB pad, ready for soldering without flying wires. If for high-power, avoid cheap connectors and get branded silver plated ones with PTFE insulator (Amphenol etc).

ABOVE: 1.5 KW at 3.5 MHZ 


This design is a 11th order Chebyshev high-pass filter with very low ripple.

It is offered in two variations, one low-power, for receive only applications and another capable of withstanding high power, i.e., capable to pass high power on all HF bands including 50 MHZ without the need to put it out of the line when transmitting up to 500 W or more.

A special enclosure, for each of the two variations, is also available and both PCBs are designed with those enclosures in mind.

There is no something high-tech on these filters, only, because many friends of mine were not satisfied from the performance of commercial low cost similar filters, asked me to develop a better one with more elements to give rapid attenuation of the MW BC band of 550 - 1600 KHZ, while to perform transparently on all of the rest of the HF spectrum with minimum loss. I have started the design thinking to sacrifice the 1.8 - 2.0 MHZ amateur band (or, at least don't care about this band) because I didn't know how to get minimal loss on 160 m and deep attenuation on the area of 550 - 1600 KHZ at the same time. One solution was to use an elliptic design which provides rapid attenuation curve but only up to around -40 dB minimum attenuation of the rejected band so to be practical and easily reproducible at home,  and another solution was to use high-order and  carefully selected good components with the Chebyshev coefficients. With the chosen topology, an attenuation curve of around 10 dB per 100 KHZ has been achieved, -16 dBc on 1600 KHZ, (-20 for some prototypes),  --26 dBc on 1500 KHZ,  - 37 dBc on 1400... <-100 dBc under 800 KHZ and even more on 550 KHZ., while its maximum loss over the 1.8 to 54 MHZ range is on the middle of the 160m band with 0.4 dB, which is quite acceptable at lower power levels.


ORDERS EUR 29.00 + S&H 

Photo 1 & Photo 2. The PCB is of highest quality, with 2-oz copper layers, gold plated and 1.6 mm thick in order to carry the heavy toroids without bending. The transmission line is straight from the input to the output and controlled to 50 Ohms, while thick enough to handle high power. The special capacitors are hand-picked for closest value of capacitance and factory soldered in place.



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