Luister op een afstandje mee naar de chaos op mijn stream van de Rode Kruis en Stadstoezicht frequenties. Klik op de volgende link of plak ‘em in je mediaspelert:

http://chelydra.dyndns.org:8000/trajectum

Veel luisterplezier!

-edit- Nog even een toevoeging: Ik zal kijken of ik in de toekomst meer structureel een online scanner van Utrecht kan opzetten welke gebruik zal maken van dit adres. Ook komt er misschien een centrale Online Scanners pagina voor alles wat ik heb lopen. Stay tuned dus!

Zo’n schakelaar heeft drie aansluitpunten. Twee schakelpunten zijn voor de daadwerkelijke schakelaar, en de derde is voor een neonlampje. Zie het onderstaande plaatje:

Zoals je ziet heb je alle draden nodig. Je kan dus niet de schakelaar in een fasedraad hangen en verwachten dat het lampje ook werkt. Daarvoor zou alle stroom door het lampje moeten en deze is daar niet geheel onverwacht tegen beschermd door weerstand R (Ne lampjes zeggen *poef* als je ze direct op netstroom aansluit). Deze weerstand is vaak 100 kiloOhm.  R = V/I,  100 * 10^3 = 230/ I = 0.0023 dus ongeveer 2 mA.

Om het lampje aan te laten gaan als het apparaat wordt ingeschakeld moet je de draden aansluiten zoals in het plaatje. Als de schakelaar contact maakt loopt de stroom via B door het apparaat, en door het neonlampje naar de nuldraad.

Je kan het lampje ook altijd laten branden. Dit is handig voor als je de schakelaar in het donker moet vinden. Daarvoor wissel je A en B gewoon om. De binnenkomende stroom zal via B altijd door het neonlampje kunnen naar de nuldraad kunnen lopen. Ook als het apparaat ingeschakeld is zal het lampje blijven branden omdat het dan parallel staat aan het gevoede apparaat. Aangezien een apparaat normaliter het net niet kortsluit blijft er altijd genoeg stroom over voor het lampje om te blijven branden.

Je zou denken, waarom zo’n heel artikel over zoiets simpels? Nou, zelfs op Circuits Online zaten ze ermee te harrewarren dus ik dacht, laat ik dit eens duidelijk uitleggen…

Recently I purchased a Sangean ATS-505 shortwave receiver. I had some money to spend and I figured I needed a portable receiver for the summer to monitor shortwave transmissions, especially amateur radio activity. That is also the reason why this review is geared towards SWL’s and radio amateurs.

I bought the receiver in an electronics shop in the center of the town where I live, Utrecht. It cost me about 90 euro’s. I think that is an acceptable price considering this receiver has full shortwave coverage and can receive SSB transmissions.

Specifications

• Coverage LW 153-279 kHz, MW 520-1,710 kHz, SW 1,711-29,999 kHz, FM 87.5-108 MHz
• Antenna: Built in telescopic aerial for SW and FM, ferrite antenna for MW and LW, or antenna connected to external antenna socket (impendance unknown), probably “just connect a wire”
• Modes: AM/WFM/SSB (BFO)
• Power 6 Volts DC (4 AA batteries). AC adaptor optional.
• Size 128 by 214 by 39 mm HWD
• Weight 840 g  without batteries
• Memory: 18 SW and 9 LW/FM/MW presets

Other features:

• Human Waking System alarm. (how can being waked  ever be a nice, humanly thing?)
• Dual timer for setting time “at home” or just UTC/GMT, nifty..

Contents of package

The ATS-505 comes in a small carton box containing the receiver, a (fake?) leather pouch, manuals and the obligatory warranty card. There is also a “set” available which contains an external antenna for improved sensivity.

General quality and build

The ATS-505 feels a little bit cheap. The tuning button feels fragile and the plastic of the housing could be a bit thicker. This is not a rugged radio and I think it is best to protect it from abuse.  The pouch seems to be supplied with the radio for a reason.

The buttons on the radio are large and placed with sufficient distance to eachother. The display is large and easy readable and has a proper backlight function.

The speaker is quite large and delivers good quality sound.

Experience with general use

The ATS-505 is an easy receiver to operate with some quirks, but we will get into that later.

The receiver has a big on/off button. I would have preferred it to be a switch. When the receiver is in its pouch, it can be turned on a little bit to easy.

Anyway, after turning it on you can press the BAND button to select a band, LW,MW, SW or FM. When the radio is in SW mode you quickly jump to the various SW bands using the SW SELECT button.

You can also enter frequencies directly by pressing the ENTER button and entering the frequency. On non FM bands, this is in the KHz  format. Tuning into non-broadcast (amateur) band is a matter of entering the frequency and pressing ENTER again.

The receiving mode can be changed between AM and SSB using the switch on the left side of the radio. SSB is only available on the SW bands between 1711 and 29999 KHz.

On SW, the tuning step is 5KHz by default. This is fine for normal SW receiving, but in the amateur bands you need finetuning. Pressing the tuning button enables a 1 KHz step. When listening to SSB, you can use the clarifier knob on the left side of the radio for tuning into stations. This knob is accurate enough for easy tuning into signals.

This radio has one quite annoying “feature” that is mentioned in any review of this radio. Pressing any button while using the 1 KHz causes the radio to revert to the 5 KHz step. You have to press the tuning button again to set it to 1 KHz, for example each time when changing bands or entering a different frequency.

Battery use is low. After some hours of listening, the battery indicator (showed when radio is turned off) still shows a full battery charge.

Sensivity and RX performance

This radio is sufficiently sensitive. LW/MW and FM receiving is as expected. However, the SW band occasionally suffers from cross modulation and overloading.  I was standing on the roof of my house during a contest on various bands, and the “big guns” were able to overload the radio causing distortion in the audio. However, this was easy counteracted by reducing the length of the telescopic antenna. Instant attenuator, HI.

The radio also has a LOCAL/DX switch wich is completely useless in my opinion. It seems to reduce the sensivity far too much. If loud stations are reduced to very small signals barely above the noise by using this switch something isn’t right.

As expected, receive filters are wide. When lots of stations are on the band, you will have to turn on “neurological filtering” in your head. For normal monitoring outside frantic contests the filters are sufficient.

Conclusion

This is a nice receiver for normal monitoring of SW transmissions and normal LW/MW/FM use. It allows easy SW RX when you are on the move outdoors. Even indoors with lots of interference I was able to pick up amateur stations.

However, the radio is cheaply built and has some annoyances like the fine tuning reverting to normal tuning when any buttons are pressed.

In short:

Pros

• price, recommended for beginning SW listeners
• ease of use
• large buttons and display
• dual timer for easy recording of UTC time
• low battery use

Cons

• annoying fine tune “feature”
• easy overloaded
• cheaply built
• wide filters

On a scale of 10 I would give this radio a 7. It is definitely a nice radio and the disadvantages of this receiver are more than tolerable.