Marc PA1O has produced two documents, covering his analysis and simulation of the RX and TX band-pass filters, and the PA output and low-pass filter circuits.
His analysis highlights errors in some of the previously published component values, and suggests corrected values.
Marc's documents also include photographs of the PCB modifications, and his measurements of efficiency and reflection coefficient.
For some considerable time a number of 4m enthusiasts including myself have been trying to encourage the Sysop at DX Summit (oh2w.kolumbus.com) to install 4m in the database search dropdown to no avail.
Late in June, I approached EA6VQ, the Sysop of "DX Sherlock 1.4 V-UHF QSO real time maps" and asked him if it was a realistic request to have a 70MHz map installed along with the existing 6m, 2m and 70cms maps. For a long while now DX Sherlock has had a 70MHz searchable database of spots. EA6VQ's response was positive and he asked for patience and time to undertake the changes.
I am happy to announce that DX Sherlock now has a 70MHz realtime map, fully operational. Now for the first time, we have a visual representation of the 70MHz spots appearing on cluster, with interconnecting lines which will graphically show where the propagation center is.
In order for the map to work correctly, one only need submit a spot to the clx, formatted in a particular way with the required basic information. Alternatively one can enter the spot directly on the DX Sherlock website.
The format required in the comment field to make the map work is:- [4/6digit locator]
The square brackets are NOT required but shown to illustrate the format in this article.
The web address for the map is :- http://www.vhfdx.net/spots/map.php?Frec=70
Paul GW8IZR adds: "the users of the Livemuf website and downloadable Livemuf application have had this facility for several years. All of these reporting tools are excellent and each author should receive due credit.
As with any of the tools "path centre" is only part of the story and the images require some interpretation. Looking at filtered output from the dx cluster limits the ability of a user to interpret the data."
Following a request of Luca Ferrara IK0YYY, the Italian Ministry of Communications, in coordination with the Ministry of Defense, has reportedly authorized on July 12th 2007 an amateur radio experimental campaign on the 70-MHz band (4 meters) up to December 31st 2007 (news to be officially disclosed by the recipients of the formal authorization) . Such campaign is being carried out under the technical coordination of Piero Tognolatti I0KPT, Full Professor of the Electromagnetic Fields Group and Director of the Electrical Engineering and Information Theory Department of the University of l’Aquila.
The experimental campaign, whose results will be published after its conclusion, is reportedly open to all Italian radioamateurs.
A beacon transmitting on frequency 70.088 MHz (mark) with FSK modulation (500-Hz upward shift) has already been activated. This is at the very low edge of the authorized band.
We wish to express our warm thanks to the Italian Ministry of Communications (Ing. F. Troisi and Dr. A. Cascio) and to the Italian Ministry of Defense, who, despite the administrative and operational hurdles, have once more given the Italian radioamateurs a clear sign of esteem and credibility. Sincere thanks are also given to the Università of L'Aquila (Prof. P. Tognolatti) for its exquisite and effective cooperation.Luca Ferrara IK0YYY – Antonio Vernucci I0JX
Budapest, 29 June, 2007.
An experimental radio licence was signed and issued today for Haros Radioklub that permits radio usage of the 70 MHz band for the first time in Hungary for 30 radio amateurs.
The licence is valid for a period of 30 days starting 1 July 2007. The aim of the experiment is to study propagation of radio waves in the 70 MHz band where all FM broadcasting was stopped in February. The frequency range permitted for the experiment is 70.000 - 70.500 MHz, and the licence is valid for all operating modes, CW, SSB, narrow band FM and digital modes like JT6M. Maximum effective radiated power (ERP) is limited to 1kW.
The original request was submitted in April. In spite of lack of Radioamateur service allocation of the band the National Communications Authority responded quickly and cooperatively. In the experiment we have to identify ourselves by “call name” beside our ham radio callsign. The call name is composed by a prefix “70m” and a suffix of amateur radio callsign.
70M1BVC HG1BVC 70012.5kHz JN87FI beaconWe hope that these radio amateurs, with their experience, international reputation and the geographical location of their stations mean guarantee to the success and professionalism of the experiment. Our long term goal is to contribute to the joint efforts of 70MHz allocation for amateur radio service in Hungary and worldwide.
70M7BVB HG7BVB 70037.5kHz JN97QK beacon
The Coulsdon Amateur Transmitting Society Weekly Net operates on Wednesday evenings on 70.425 MHz from 2100hrs local time. Listen for club station M1FUR operated by myself, G0KZT. If you hear us, please call in.Details of other regular net activity may be found here: www.70mhz.org/nets.htm