SDR Tutorial

[N8XRE]

Thanks for the info though I forgot to include it in my post, I never thought to try filtering to reduce broadcast interference, good idea I'll have a play

The thought occurred to me when I was tuning to one of the NOAA weather forecast/warning radio transmitters we have here in the states. I have one fairly close to me, and it makes fir a good receiver test, if a VHF unit can't hear it, there's something really wrong with it or the antenna. So, as a Icom W32A owner (also know for having practically no front-end filtering), when I saw the NOAA station get buried in the waterfall by noise, I knew it probably was getting swamped. I also live close by several FM broadcast stations. So I tried the broadcast trap and lo and behold, it worked. The best part was being able to use the spectrum display to see the degree of attenuation that was occurring in the 88-108 Mhz band.

[G0CWA]

The widget I ordered thankfully came with a MCX connector for the antenna , so I rigged up an adapter chain to put an FM broadcast trap in-line with the 2m antenna I was using. Made a world of difference.

Hi

I tried a simple filter, series tuned LC across the co-ax and managed to tune out the broadcast band to no avail it didn't seem to increase the sensativity on 2m, what circuit of filter did you use please, obviously mine was just a simple notch and may not have been viscious enough with the broadcast band.

If you can post a copy it would be fantastic.

Thanks Nick G0CWA

[N8XRE]

Hi
If you can post a copy it would be fantastic.
Thanks Nick G0CWA

Sorry, OM, I wish I could. This was a "FM Broadcast Trap" from Radio Shack, which if I recall correctly is a high-pass filter over 120 MHz, I just happened to have one in my A/V parts junkbox.

[G0CWA]

Sorry, OM, I wish I could. This was a "FM Broadcast Trap" from Radio Shack, which if I recall correctly is a high-pass filter over 120 MHz, I just happened to have one in my A/V parts junkbox.

Hi no problem with your help (I used your description as a search string) and came up with this, How to make your own trap.


http://www.google.co.uk/url?sa=t&rct...5oK9m_1J_um8fw

Depending on the "Q" of your home made circuit two or thee stages in series should allow blocking of whole of VHF BB. I should have tried pll tuned circuit in line rather than series tuned across feed, both give notch reject function.

Thanks for your help Nick G0CWA