Suggestions for a filter

[gmclam]

During the day I get quite a bit of interference from a paging signal on 152.840 MHz. I have not yet connected a meter to see how strong it is, but I can hear it mixing with many other frequencies I monitor.

I am open to suggestions to filter this signal. I do monitor frequencies very close to this, above (153.770) & below (151.475), so I'd want a fairly narrow filter. I don't have a spectrum analyzer, so winding my own might be tough, but I do have a RF meter.

Thanks in advance.

[mtindor]

I'd recommend a PAR filter, but you are really going to be hard pressed finding a reasonably priced filter that will (a) filter out that signal AND (b) do so without having a significantly adverse effect on performance on 153 Mhz.

The ~70 dollar PAR filter for 152 Mhz has a notch of 35 db with you still being down about 3 db at 2.29 Mhz +- 152.840.

So, at minimum you'd be 3 db down between 150.55 and 155.15. Of course, 3db down isn't much... but the attenulatioon increases much faster the closer you get to the center freq.

see: VHFSYM152HT Specifications and Plot

So you'll have to weigh just how much attenuation you are willing to incur at your listening frequencies. If they are strong repeater frequencies, then you likely will hvae no trouble continuing to hear them even with some attenuation.

Dale can center it on any freq you want. He can also create a filter with a narrower notch, but at a significantly increased cost (think commercial filter).

But I do recommend the PARs. He built one for me to wipe out TV Ch 9 . It works superbly.

Mike

[fineshot1]

or

you could purchase one of these or similar on ebay or some of the other ham radio web sites

NOS Decibel Products DB4140-1B Notch Filter 148-174 MHz - eBay (item 250454182586 end time Jul-05-09 19:00:00 PDT)

http://www.repeater-builder.com/db/d...structions.pdf

[gmclam]

Thank you for the information. I'll do some measurements tomorrow to see what my D/U ratio is and go from there.

I do think the 35dB filter will do the job without negatively impacting other frequencies I monitor, but I don't think I need that much attenuation either.