ABF~125

VHF Air Band Filter for better strong

signal performance...

The ABF125 is a receive bandpass filter especially designed to improve the strong signal handling characteristics of receivers for VHF commercial Airband listening. The ABF125 is suitable for connection to most airband and wide range receivers on the market, it is not designed just for AOR branded products. The addition of this filter to the aerial signal path will provide additional selectivity which will enable the receiver's circuitry to cope much more easily with strong interfering signals such as Band-2 Stereo or Short wave broadcast transmissions which can be manifest in many ways such as ‘hissing’, mixing of many signals together, music breakthrough and desensitisation of the receiver.

The ABF125 will provide useful additional selectivity (in many situations) to any receiver's ‘front end’ by reducing the multitude of unwanted strong signals from reaching and saturating the receiver's first mixer stage... this results is less interference and improved reception.

Of course ‘stub filters’ can provide a degree of rejection to unwanted signals but tend to be bulky being suitable for base station applications and usually have to be hand-made. The ABF125 on the other hand is ready made and very compact measuring only 73.5mm and weighing a mere 52g yet offers excellent out of band attenuation typically of 25dB from 0.3 ~ 75 MHz and 20dB from 190 ~ 400 MHz. This makes the ABF125 suitable for connection to both external aerials and for connection directly under the whip aerial of a hand-held receiver. A BNC socket (female) is fitted to the top of the ABF125 and a BNC plug (male) to the other making connection to an aerial easy and straight forward.

The ABF125 is not an amplifier so will not ‘boost’ signals, however the additional selectivity offered can significantly improve reception in many situations by removing unwanted strong signals which may overload the receiver and reduce it's effectiveness. When any connection is fitted to the aerial signal path some reduction of signal is resulted (attenuation) however the ABF125 in band attenuation level is very small due to the excellent in band V.S.W.R. of 2:1 resulting in a loss of only about 4dB.

Note: Remember to remove the ABF125 from the aerial when monitoring signals other than VHF Airband or signal strength will be dramatically reduced.

Specification

Model ABF125

Bandpass coverage 108 ~ 136 MHz

Nominal impedance 50 OHM

Through attenuation in-band 4dB

Attenuation typically

0.3 ~ 75 MHz

190 ~ 400 MHz

25dB minimum

20 dB minimum

V.S.W.R. in-band 2:1

Aerial input BNC socket (J)

Aerial output BNC plug (P)

Size (length) 73.5mm

Weight 52g

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CT8200 optional CTCSS slot card

EM8200 optional external Extended Memory slot card

The EM8200 enables the whole 1,000 memory channels in 20 banks and 40

program search banks to be backed up to the EM8200. In fact the EM8200 can hold the entire contents of the AR8200 including environmental operating data and band scope FOUR times in EM8200 locations 0, 1, 2 & 3. It is not necessary to save ALL data, you can specifically choose what data is to be backed up and to which location.

VI8200 optional Voice Inverter slot card

The VI8200 enables the AR8200 to recover intelligible audio from certain types of analogue transmissions which would otherwise sound scrambled. They operate by splitting up the audio spectrum and "flipping" the upper and lower tones around a certain frequency point. The VI8200 enables 157 different "flip points" to be selected in the frequency range of 2.4kHz to 5.6kHz.

Note: Although principally designed to descramble Japanese cordless phones, various UK PMR services use simple inversion (such as PMR446). If you hear a transmission which sounds like a ‘speeded up tape recording of Donald-Duck’ but you can recognise the occasional word, it will probably be simple inversion. If however you cannot understand a single word, it is likely to be a more complex form of inversion. Several customers have e-mailed zipped WAV audio files to us so that we can try to confirm compatibility prior to purchase, if you do forward a file, keep the size to no more than 1MB