As wrote on the previous page, "life is too short for QRP". And this motto is simply true... I am quite sure, that all of us, who still remember 144MHz PAs with OC170 transistors, would agree with me. Without QRO is not possible to complete any VHF connections across Alps, MS, EME, FAI & RS QSOs and not only them. Without QRO you can't imagine decent position in contests.

But QRO is not the slogan only. It is a lot of qualified work. And a lot of knowledge. Because without knowledge, experience and polite behaviour is not possible QRO transmitter construct and use. If some of this is missing, the result is trouble... And this trouble is not the QRO, but all relations, which may related to possible interference. And it can resulted even in problems in social relations...

But not only QRO may brings interference. Large area of possible difficulties may related to other circuits as well as on transmitting and receiving side. And sometimes it concerning to design, use and anticipation. For understanding and step by step movement to the better results and solution of interference between contest stations, we want to be focused to these questions, which are related mutually. Of course it is never ending story. And due to that, this page will be always "in the construction".

On the other side, ham radio community will be very curious to your experience. Please send us your message by email, or visit our discussion board.

Our HW Corner page is still under construction and many of our czech articles are not translated yet, unfortunately. Please be patient. If you have an interest to particular article, please let us know. We can arrange priority translation.


HW articles from:

2001       2002       2003       2004       2005       2006       2007       2008       2009       2010       2011       2012       2013       2014       2015


For translation from Czech use the Google translator please.         - EN version available

15.2.2016: Construction unit for peak monitoring as a part of SSPA protections
1.12.2015: Start up unit for the High voltage Power supply of Tube PA here.
10.9.2015 BIAS circuit PCB consisting PTT time sequencer for tube PA here.
23.8.2015: Interface for LED bargraf for indication of the supply current of the SSPA module.
16.8.2015: Smith chart in the Amateur radio practise -  copy of the presentation made for Polish VHF Meeting Zieleniec 2015 PL, EN.
12.4.2015: PEP Wattmeter unit for installation into a PA here.
15.1.2015: LPF without coils for VHF TX.
14.1.2015: OM3W: design of transmitting route for high performance transverter 14/144MHz.
14.10.2014: Use of Smith chart for asymmetric splitter design II.
18.8.2014: About QRM in VHF contesting - conference paper for Polish VHF meeting Zieleniec 2014 (in PL).
21.7.2014: Sequencer "reloaded" here.
11.6.2014: Small 23cm driver with two RA18H1213G devices.
20.5.2014: FT847 switch ON troubles? Here is a modification.
14.4.2014: Redesigned controller of aerials switch for VHF Contests.
31.3.2014: Measurment procedures of Old hams: PA linearity check
25.3.2014: Short note to contest QRM issue in relation to the path loss.
28.1.2014 PCB directional coupler for SWR protection of SSPA up to 800W RF.
25.1.2014: Schema for consideration -  how to arrange better isolation of antenna relay.
22.12.2013: Thermal control of the BIAS for SSPA with LDMOS.
1.11.2013: Design of 13cm transverter by DJ6EP (Czech translation of the Polish article).
21.9.2013: SWR and return loss - consideration and terminology - for Czechs only.
17.8.2013: How to maintain secure operation of HI PWR SSPA. (in Polish)
27.7.2013: Matching microstrip line for 70cm DK7ZB antenna + more pics.
26.12.2012: How to operate safely "single output" VHF transceiver.
28.11.2012: How to make a coils for VHF gear. More.
11.11.2012: Design of  23cm driver here.
6.11.2012: PWM controller for cooling fan here.
5.11.2012: Attenuator up to 23cm here.
7.8.2012: Input tap & adjustable attenuator for 23cm PA here.
15.7.2012: How to prevent burn out of PTT relay contacts here.
21.6.2012: Splitter 40 / 60% for drive of two 144MHz PA here.
12.2.2012: Branchline quadruple splitter / combiner for small 23cm PA here.
2.12.2011: Step down switching power supply 13,8V / 10A for PA driver here.
17.6.2011: Small 1W attenuator up to 23cm band here.
15.4.2011: Bandpass (interdigital) filter for 23cm here.
15.1.2011: Current protection unit for SSPA modules here.
15.11.2010: TRX - PA - LNA - ANT interconnection schematics to prevent damaging of LNA
23.10.2010: LNA by OZ1PIF - experience & mods here.
20.9.2010: Unbalanced power splitter for drive of different 2m PAs here.
31.7.2010: Simple RF sensors performance for internal RF measurment in SSPA
17.7.2010: Mechanical design of solid state 800W PA for 70cm
16.6.2010: Very rare (?) PA failure in FT847 here
20.1.2010: Few more words to the 70cm PA instability, observed in FT847 transceiver from time to time
21.12.2009: OŠKOBRH - Remembrance of 70cm transvertor construction [1986]
29.11.2009: Directional coupler made from two semirigids for SWR protection.
25.11.2009: Power limits of coaxial connectors here.
09.9.2009: 20.years old OK1VPZ's article focused to contests interference on 144 MHz.
24.4.2009: Comments and additional circuit in the issue of ALC modification in FT847 here.
24.1.2009: SWR protection unit for solid state PAs. More in CZ here.
24.4.2008: RX antenna switch for multibeaming contest operation in 144MHz band here.
24.11.2007: DC amplifier for powering current measurment of solid state PA here.
24.9.2007: How it is with BIAS Circuits for Tube PA? More in Czech with EN links here.
31.8.2007: PEP Wattmeter offset compensation here.
31.8.2007: Usefull peripheral circuits related to Solid state PA cooling here.
24.6.2007: FT847 - ALC modification for transmitter splatters suppression here. More in Czech here.
2.5.2007: Notes to protection of LNA here and to LNA IMD characteristics in Cz here, here, here
4.4.2007: Table of resistors value as well as power dissipation for most used RF attenuators.
14.2.2007: Where you may acquire printed circuit board for our constructions .
10.1.2007: Simple circuit for control of PA cooling fan here.
30.9.2006 Old, but well proven PA 432 MHz utilize GI14b tube here.
14.7. 2006: Construction of equipment for use in VHF Contests without compromises. Is that feasible? More (CZ).
11.1. 2006 Technical data sheets and service manuals of some YAESU transceivers.
2.12.2005: Solutions of  FT847 70cm PA oscilations. More.
14.11.2005: Notch filter for local VHF station interference.
24.10.2005: New, sofisticated bias circuit for high power VHF PAs with  bipolar transistors.
5.10.2005: Neutralization of tube amplifiers for 23cm here.
18.6.2005: Schematics and data sheets of BMT226 - Allamat 88 transceiver here.
3.6. 2005: Update of VHF PEP Wattmeter design for contests here.
31.5.2005: Measurments of transceivers by DF9IC. Note to phase noise value.
18.4.2005: Design and construction of universal freq. synthesizer for microwave transverters and beacons here.
10.3.2005: Size of typical coax lines here.
10.3.2005: How to make a scale for measurment. Try this SW.
24.2.2005: Design of low pass filter for 432MHz PA.
14.2.2005: Design of low pass filter for 144MHz PA.
6.2. 2005: Calculator for design of suitable dividing ratio focused to PLL oscillators for UHF and SHF transvertors.
23.1.2005: Desing of automatic regulation circuit for cooling and Bias of tube amplifier.
16.1.2005: Design of HV power supply with starting automatics and current protection.
8.1. 2005: Time sequencer for instalation into PA - design here.
16.9.2004: Power supply for second grid of tetrode amplifier here.
26.8.2004: Nice transistor for 23cm, which can produce > 80 W PEP SSB, by Philips. 
26.8.2004: Schematic of well tried "roger beep" for contest operation - particularly for Yaesu here.
18.6.2004: Some links to czech and abroad  device suppliers here & here.
31.7.2003: 1W PA on 24 GHz gives you chance for Rainscatter DX. More here, here & here. (TNX DL2AM)
14.4.2003: Power dividers here.  Antenna combiners by LA0BY here.
29.3.2003: Relays for RF applications here & here
28.3.2003: Realization instructions for low noise amplifiers by YU1AW here
27.3.2003: Motorola released new transistor, which can deliver  200 W on 70cm.
26.3.2003: N2UO design of power hybrid 90° combiner for 23 cm here.
23.12.2002: Description of  R2CW transceiver (3.8MB) here.
30.10.2002: Useful SW here.
20.10.2002: Design of transistor LDMOS driver for > 100 W on 144 MHz here.
20.7.2002: Table - reflected power and SWR relations here.
18.7.2002: History, schematics and modifications of Czech TXR210 transceiver here.
7.4. 2002: Design of  23 cm QRO PA by KD5FZX with GS23b tube here.
18.3.2002: Design of simple circular rotator display here.
10.3.2002: Simple OK2KKW antenna for 1296 MHz here.
6.2. 2002: Third part of OK1VPZ interference article here.
4.2. 2002: Software for antenna design and practical designs here.
28.1.2002: Input match circuit for PA 144 MHz with 2xGS35b here.
22.1.2002: Motorola terminated production of many power RF transistors. Data sheets, replacement and info here.
6.1.  2002: Construction of  21 / 144 MHz transverter here.
22.12.2001: Second part of OK1VPZ interference article here.
6.12. 2001: Look into a history, where you can read valuable info of OK1DAK to phase noise of oscillators.
5.12. 2001: Notes of OK1VPZ from 1988 to tube PAs design here.
27.11. 2001: Old, but still valid article abou sideband noise of VHF transceivers you can find in DUBUS archive here & here.
25.11. 2001: Copy of VHF solid state PAs articles from OK VHF conventions Klínovec 87 and 88.
20.11.2001: First part of OK1VPZ interference article here.
20.11.2001: HF transceivers performance used for VHF Contests.
20.11.2001: Copy of correspondence to one interference causa here.
20.11.2001: OK1DAK article - about IMD of preamplifiers here.
20.11.2001: MUTEK parts for upgrade of your rig here.
20.11.2001: Additional filters for improvement of your receiver here.
20.11.2001: Software of Smith diagram for matching circuitry here and here..
01.12.1986: Home made antenna relay for QRO PA  here.