RF Filters
How they work
In Use






2 meter filter bandwidth 4MHz

70cms filter bandidth 9.5MHz
1090 MHz SBS filter BW 22MHz 23cms filter bandwidth 20MHz
1433 MHz Filter bandwidth 50MHz  

Filter bandwidth is measured at the Ė3dB points.
 (-3dB is the point where the signal is attenuated by 50%).

Through loss is the loss of signal through the filter at its deigned frequency. All filters across the range have a through loss of no more than -1.6dB


This is what users of my filters have to say:  
Steve  G4TRA writes


  I have now had a chance of testing the filter which works fine. For the first time I am able to see the subtle changes that the transmit frequency does to the received signal being transmitted back to me from the repeater. Also I am able to adjust my camera for the best response out of the repeater as well. All in all an excellent ATV duplex filter. I cannot imagine anyone doing without one of these if they want to see their transmitted picture coming out of the repeater. Many thanks for the excellent service, you could teach the "big" boys a thing or two about customer communications and I have no trouble in recommending you to any other interested parties.
All I need now is a decent 1316MHz receive high gain beam. Cheers Steve

John Haddon of Exemplar-Associates:

I used the filter "in anger" on Sunday and it was just fine. Thanks for your help!

Bill MW1WEJ writes

 The filter that Brian made and tested for me is located in the roof space of my bungalow at the end of two metres of coaxial attached to my homemade 23cm 15-element antenna. This is in turn about 10 metres to the side and 3 metres behind my Tx antenna.  Before I fitted the filter a slipping ghost image was present on the Rx monitor when my Tx was on. With the filter in place and followed by a 20 db preamp the display produces P5 results from a MASPRO under favourable signal conditions.  73s Bill MW1WEJ  

Derek GW3FDZ  writes

 To enable me to observe my reradiated signal from GB3GW (which has a separation between send and receive of only thirty megahertz) I purchased one of Brianís filters. A separate antenna, which is located approximately fifty metres from my transmitting antenna, is used for receiving this signal. The filter proved to be highly effective due to its pass-band characteristics. A very slight tweaking of the tuning stubs whilst looking at a test card ensured that the filter was matched correctly to my particular antenna and receiver in use whilst retaining the required bandwidth for a good colour picture. No breakthrough has ever been observed during low signal conditions even though I am transmitting maximum allowed power output. A useful addition is the calibration chart, which is affixed to the filter case. This filter is excellent value for money and highly recommended.   GW3FDZ.   

Tim G7YGS writes

It is a good filter and I use it at home for watch through after retuning it to 1316mhz. If anyone asks me about filters then I would recommend them to you. Cheers for now.     Tim (g7ugs). 

Pat GW6IMS writes

 I work through GB3GW repeater. I have one of Brianís filters tuned to 1310 MHz on my receive system. This allows me to see my own signal from GB3GW when I am transmitting. I run an output power of 18 watts at 1280 MHz to a 35-element Tona antenna with 20dB gain. My receive antenna is a 19 element Sandpiper which is located 30 ft behind the tx antenna and 10ft to the side. The antennas are well separated, however without the filter I would not be able to see my own picture from GB3GW. With the filter in circuit I receive GB3GW at P5 at all times. I would certainly recommend this filter to anyone who wishes to be able to monitor their signal from a repeater. It also keeps the front end of my rx clean from other out of band transmissions. Pat, GW6IMS   

Dewi GW0ABL writes

 I operate through GB3TM ATV repeater on Anglesey, using a Maspro satrx, a pre-amplifier with 16dB gain. My tx is a Worthing Repeater group 1w transmitter with a 18w amplifier. Both my rx and tx antennas are also from the Worthing group, and located very close to each other. Before I purchased the band-pass filter from Brian, I could not receive my own signal back from GB3TM whilst my transmitter was operational. Now with the filter in circuit I am able to get a P5 signal from GB3TM, when my transmitter is operational. I would happy recommend this filter to anyone. Dewi GW0ABL.

  Email - filters@bvdavies.org.uk - email is not automated to avoid spam
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