The hardware of the PI6ANH repeater

Mainly the antenna and the repeater-box itself belongs to the hardware of the system. As any other usual repeater the ATV repeater consists of a power pack, a receiver, a transmitter and the steering system. Compared to a phone-repeater there are a couple of main differences in the modules itself. For example identification is necessary by law in form of a testpicture and not only by CW-tones. Also, handling video compared with audio only (as with phone repeater) is quite different. Especially the bandwith of video and HF plays a much more important role.-


The repeater main-unit

The various modules are build into a waterproof box with two doors, which makes maintenance very easy. It took about two years until we have the hardware as it is.

Now lets take a closer look on the different modules in the opened repeater-box:

 
The PI6ANH repeater block

Left door from top to bottom:


Right door from top to bottom:


The antenna system

The antenna system is about to change at this very moment. The for the time being used antenna for reception on 1.2 GHz is the well-known Alford-Slot antenna. The horizontal polarized antenna has a gain of about 5 dBd,- the bandwith and the gain over the entire band from 1240 MHz to 1300 MHz (this is the allowed frequency range for 23cm in Germany and the Netherlands) is quite good.
For some detailed information on that antenna, visit the Brookdale ATV Repeater Home Page (WB3QCD Alford-Slot Antenna for 430-440 MHz).

Receiving 2.4 GHz FM-ATV signals on long distance makes it necessary to fight for any dB, which might be available anywhere in the system.
The easiest way is still a good high-gain antenna (semiconductors with more than 5W HF on 2.4 GHz are still too expensive for the average HAM).

The "11-Element-Slot" - Antenna (very similar to the DC0BV slot antenna) had been recalculated to the repeaters frequency and to a 180 degree (halfsided) radiation pattern. So far, we only could measure (with commercial help) the gain in 0 degree direction and the SWR over the whole band.-

The results were very satisfying for us: 13 dBd gain with a (-3 dBd) bandwith of 40 MHz and a return-loss of more than 20 dB (!). The raw aluminium block has the sizes of 80x40x3 cm and is standard and should therefore be available for only a little money. A sketch with all lenghts and impedance transformations is in work. (Has anyone else experience with such antenna types ?)
Compared to the dipol groups (ca. 7dBd gain) we used before, it is an additional gain of 6dB (= 4x times HF-Power).

On the picture: DL4EBJ (Johannes) with 11-Element-Slot Antenna.

One easy way to receive the repeaters 13cm-signals is described in "QRV on 13cm FM-ATV" (still in German only).



 

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J. Köring, Bahnstraße 3B, 47551 Bedburg-Hau, Germany
Copyright 1996 by Johannes Köring (DL4EBJ). All Rights Reserved.