giovedì 22 agosto 2019

Club 72

Un club interessante: Club 72

 Credevo di essere già arrivato al limite della potenza utilizzabile per effettuare QSO con il CW: circa 1 watt (non stò parlando dei modi digitali, come FT8 ed altri). Ed invece ho scoperto che alcuni OM utilizzano potenze ancora inferiori, fino a qualche milliWatt.

Esiste un Club in cui si perseguono queste attività: il Club 72, fondato da Oleg Borodin, RX3G.
Il link è il seguente:

Sito del Club 72 

Qui ho imparato alcune sigle nuove, oltre a quelle conosciute del QRP e QRPp:

QRP:   potenza < 5 Watt
QRPp: potenza < 1 Watt
QRPx: potenza < 100 mW 
QRPu: potenza < 10 mW

Altre informazioni si possono trovare su QRP Vestnik ("Messaggero del QRP"), la rivista pubblicata sul sito del Club72.


venerdì 17 maggio 2019

QRPp: slowing down the power again

QRPp: using only 1 watt

Working conditions: 
Rig: microBITX
Ant: Off center feed dipole, 20 meters long, folded and linearly loaded (on a tree). 
Ant tuner: Kenwood AT-130
Power: 1,25 watt (1250 milliwatt)

QSO during last year of very soft activity on 21 MHz (almost some minutes during the weekends; never in the evening or during the night).






 I use the microBITX from about one year. On 15 meters, the power given is of about 1 watt (1250 milliwatt).  I thought the output power was of 5 watt, but when i measured the output power i realized that it was of only 1 watt (1,25 for the precision).
So, my QSO are almost QRPp. 
During the last year the band was often closed, so i worked mostly on 40 and on 20 meters. We are during the minimum of the solar cicle, and so this is what we can expect. But last week i extracted the data from my database, and elaborated them. The strange thing is that generally when i had the QSO, it was not difficult, may be for the low noise of the band.
My favorite mode is CW, but also USB is valid, during contests.

73 de IZ3AYQ







sabato 16 febbraio 2019

The 1 watt game






THE 1 WATT GAME.
I. OBJECTIVE: A short QRPP CW game on the 20 meterband. All radio amateurs and SWL's are cordially invited.
II. DATE : 31 March 2019 from 0900 to 1200 UTC.
III. BAND: 20 meter band only. 14.060 MHz +- 10 kHz.
IV. POWER: maximum 1 watt.
V. OPERATION: Only CW (A1A).
1. CALL: CQ 1W
2. EXCHANGE: RST report plus Maidenhead Locator. ie. 559 JO21LA. Additional info like power, RTX, antenna,... is welcome.
VI. SCORING:
Calculate the distance of each QSO.
ie. QSO between locator grids JO21LA and KO92SP is 2360km. This QSO counts for 2360 points.
TOTAL SCORE: Sum of all QSO points.
VII. LOG SUBMISSION:
Email your score to on6kz@skynet.be
Add the text: Me, (your call) , I declare that I managed a total of XXX QSOs, my total result is XXX points.
Please add your best DX (call and locator)station-info: locator, power, RTX, antenna. Pictures of your set-up are appreciated.
VIII. GAME REFEREE: Peter Kempenaers (ON6KZ/OO7Z). The Game Referee has the right to request full log in case of any doubt.
IX. DEADLINE: 14 april.
X: Nominees: award for the winner, the best DX, funiest location (if outdoor), original homebrew, lowest power QSO.
XI: Helpful links:
Determine your Maidenhead locator:
http://k7fry.com/grid/
Calculate the distance between 2 Maidenhead locators:
https://www.chris.org/cgi-bin/showdis


73 de IZ3AYQ


domenica 3 febbraio 2019

OFF CENTER FEED DIPOLE: A SIMULATION AND A TEST

OFF CENTER FEED DIPOLE:  testing unusual % dimensions

Total length: 21 meters; Off center feed at 25% of lenght (usually we can find 30%)
One leg: 5,25 meters; the other leg: 15,75 meters.
Why 5,25 m? This is not the best %; but for the moment i do not want to cut my vertical antenna aluminium tube. This is a test; if a will have good result i will try to optimize.



You can see minimum SWR at 7 MHz, 14,2 MHz, 21,1 MHz an 28,3 MHz. Using it with a balun and/or wiht an antenna tuner you can easily tune it for these band.
So, i am going to test this antenna with my RIG:

MicroBitx with antenna tuner Kenwood AT-130; the antenna has  a vertical 5,25 meters tube, and a wire of 15,75 meters that is over a tree in his final part.

Today easy contacts on 40 meters, and first contact on 60 meters (with SWR at 1:1.1)

73 de IZ3AYQ




sabato 12 gennaio 2019

Off Center Feed Dipole: some simulations

Here are some simulations for OCF (off center feed dipoles) of about 20 meters:



The original antenna was developed in 1929 by Lorenz Windom, W8GZ. The orignal antenna was worked against ground. During the years, similar antennas were developed and are generally called Off Center Feed Dipoles. They are simple to build: a simple wire and a balun 4:1 or 6:1, to convert the impedence of 200 - 300 ohm to 50 ohm.
Interesting to study in the Internet: windom, carolina windom, ocf dipole, double windom, balun.


A) L= 20.70 m, L2=6.70 m (L2/L=32%)
The OCF dipole can work (with balun 4:1 or balun 6:1 and tuner) on 7, 14, 28 MHz.


B) L= 20.74 m, L2=6.95 m (L2/L=33%)
Similar to case A): only 3 bands, 7, 14 and 28 MHz.


C) L= 20.1 m, L2=3.7 m (L2/L=18%)
 The OCF dipole can work (with balun 4:1 or balun 6:1 and tuner) on 7, 14, 21, 28 MHz.
We have 4 bands!


D) L= 20.2 m, L2=6.7 m (L2/L=33%)
 Similar to case A): only 3 bands, 7, 14 and 28 MHz.


E) L= 20.70 m, L2=3,8 m (L2/L=18,4%)
 The OCF dipole can work (with balun 4:1 or balun 6:1 and tuner) on 7, 14, 21, 28 MHz.We have 4 bands! This is the best result!



 73 de IZ3AYQ

martedì 8 gennaio 2019

QRP and QRPp schemas - part3

QRP and QRPp trasceivers: very simple RTX for great fun ! Why? Because we must build with our hands even simple things, with simple components that we can easiliy find.


Micro80 by Oleg Borodin: two similar versions with different transistors.




73 de IZ3AYQ


domenica 6 gennaio 2019

QRP - QRPp schemas part 2

Very simple QRP and QRPp schemas

 NOGAnaut by Georgia QRP Club



 The OXO by GM3OXO

Because it is better to build than to use!

73 de IZ3AYQ