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Since almost 30 years, for my portable VHF activities, I used a F9FT 9el yagi. This one was the best available for this purpose, it was leigthweight, relatively cumbersome and performed quite well. Unfortunately, it broke during a contest when falling down from 7m high...
To replace my beloved antenna, I decided to build something and not to buy one. After searching some design on internet, I finally adopted DK7ZB's one. He offers several designs, and iIchosed a 7 element yagi in 28 Ohms technology.
The advantages of DK7Zbs antennas are :
- Computer optimized
- Great reproductibility
- Easily assembled and dismantled. Ideal for portable operations.
- Excellent electrical characteristics, gain, pattern, F/B ratio.
The original version described on DK7ZB's page has a 3.26 m boomlength. So, I asked him if he could calculate it for a 3m boom. Aluminium tubing are sold in 6m length, and with 3m booms i would be able to build 2 antennas. The new calculated antennas have a small gain drop (about 0.35 dB)
Another advantage of this 7el is that with a 6m long alu tubing, you have enough for all elements and build 2 antennas.
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To be finished...
Some years ago, i developed my own rotator interface with a PIC 18F452. In a need of another interface, i was unable to find my software sources of this project, lost somewhere in the computer Walhalla ! So, i looked for a finished project to build, and found the K3NG Arduino rotator project.
It looked very complete and having some recent experiences with the Arduino, i decided to give it a try.
What i needed :
- Only azimuth drive
- 2 lines LCD display (as i had several of them)
- Eventualy 2 buttons CW + CCW to drive the rotator
- Running on an Arduino Uno (as i had several)
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Lilygo LoRa modules from Lilygo are advertised to provide a power output of +20dBm (100mW). I found that none of my modules reached the advertised power, which was more like +17dBm. |
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This page is a short description of the four phased verticals system i've build and used. It is primarily intendend to be used on the lower bands 160m, 80m, 40m. All the principles stated here are of course valid for any other bands, but you can achieve the same game with yagi antennas easily. It is mainly built around the Collins hybrid phasing system wound on toroids.
Other feeding methods are possible and certainly better, but this one is rather simple to build and use on the battlefield. (contests, fieldays, expeditions)
Many stations use this system all around the world and it has proven his effectiveness.
Four phased verticals on 80m (click to enlarge)
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At first glance, measuring a voltage with an Arduino UNO seems to be a simple task. You only need to use the builtin A/D converter and the analogRead() function. But if you want to do this and get good results, you need to take some precautions and understand what you are doing !
Here my experience, and at the end i got very good results !
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To protect my SDR UHF receivers on hilltop sites, I needed some filtering to reject local FM broadcast and repeaters.
I looked on Aliexpress what bandpass filters were available. Most of them are SAW filters.
Here are the results of my findings and testings.
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Having recently acquired this small VHF/UHF UV-998 dual-band mobile transceiver from LEIXEN, here are some informations. Measurements Usage Programming Links This radio is sometimes also named VV-998 ! Please share your own experience with me, so I can improve this page. |
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This article is essentially a personal memo, but may be useful to others. AllStarLink is a network of Amateur Radio repeaters, remote base stations and hot spots accessible to each other via Voice over Internet Protocol. It is the software we use on our private TKNet network. Acronyms TX timings RX & TX audio levels settings Language change Sound files GPS.conf for APRS Beacon via crontab |
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For one of my projects, I recently bought on Aliexpress (see links at end of article) a Chinese fan speed controller board.
I was struggling to understand how this board can be set, the instructions found on Aliexpress being nearly of no help. The Chinese to English translation is.... :-)
Here is what I found ... 
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During my SOTA activities, I often raged on the fact that the builtin CW keyer in my QRP SW-3B transceiver only had one memory ... It is indeed very practical to have several of them in order to free your hands to do something else such as finishing writing the last QSO on the logbook or making a somewhat specific call. The idea therefore sprouted to produce a CW memory manipulator that would meet the following conditions |
- 3 on the fly programmable memories
- low power consumption
- easy battery supplying
- reduced size
- easily reproducible
Having already built a prototype of the fabulous K3NG keyer, I decided to use this project by adapting it to my needs.
Subcategories
Test equipements Article Count: 5
Antennas Article Count: 8
TS850 Article Count: 4
TS590 Article Count: 3
Cartes Article Count: 2
Radiosondes Article Count: 1
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