Below 30Mhz on LimeSDR Mini - Full of garbage

I’m in Hanover Park, sw of Schaumburg. Check out SARC NET Thursdays at 8 pm on 145.23 m. I talked to the VE yesterday , I need to cram to take my Tech and maybe General exam on June 6th. It’s a fairly active group.

Cool!. Might look into that to finally upgrade to Extra before the question pool changes… (So far I have took 2 tests trying to get extra.)

Your last chance is June 6th with SARC. Extra test is giving priority. Fill out this form…

Yep. Was just reading that. I am going to have to talk to my parents and see if they have anything planed. But as soon as I know I will fill that out. (Later today)

Anyways. Good luck!


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Speaking of garbage… See the lines in my gqrx waterfall almost like graph lines? That was my own power line Ethernet adapter which creates similar noise to DSL. Decommissioned, I guess I run CAT5. It made a 60 Mbps connection to the neighbor off the same step down service transformer, through both meter heads. (Controversial FCC Part 15 devices)

Another source of noise. Cheap LED lights. I already knew I had some others that cause FM radio and WiFi interference but these go to the recycle heap. In picture Lights on, Lights off, antenna is 30 feet away outside. The source of noise is often closer than you realize. A few people doing cw on 40! But i could have heard Spain ssb (from near Chicago) more clearly earlier. (No additional amplifier, just the Lime). Still on much clearer now. (ea1dlu nw spain , 150w ssb beam 27 m up)

I am going to try getting on 40m or 20m tomorrow. I have my band bass filters ready finally. (Had to re-order some parts. I hate back orders. (From literally 2 months before the pandemic hit.)

Hoping it works out. Want to get started on HF before field day for sure.

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@chibill - William,

I’m not sure if I’ve mentioned this or it’s been mentioned in other threads you’ve read, but the LimeSDR’s receive ports, once the HF Mod has been done, are VERY wideband - enough to pick up strong images of the FM band and translate those into the 20m band. Some of the ‘hash’ or noise you’ve been subject to with the Lime may have been just that - the receive not being Low Passed enough to make it sensitive in the HF Band. Generally I use a Kenwood LF-30A (they don’t make these anymore, but its a lowpass filter that has a knee at 30 MHz and generally passes the HF band wonderfully. You can, on occasion, find a LF-30A on EBay cheap, and if you do I would high recommend buying it. It makes a world of difference for receive with the Lime (either the Mini or the USB model) and you will never regret putting that in line with either the RxLB or RxWB ports - I use mine with the Wideband port.

Just thought I’d add that in - you can certainly use bandpass filters if they’re capable of knocking out FM images and has attenuation up to 80dB in the FM band within the filter response. The LF-30A I swept one time and it’s down 80dB in the FM Band, so I usually never see any images or hash anymore when I use it with my Kenwood filter. It would certainly do well for Field Day use on receive, too.

73 de Marty, KN0CK


I have AM and FM bandstop filters PLUS a 40m band pass filter. Also I am using the Mini which according to other threads does not need to be modified for HF. (And people say you should not modify it.)

The AM and FM filter are from nooelec and the band pass filter is based off an old ARRL article. (Tuned using my VNA). I figure out how to fix the hash. Just had to strap on an extra heat sink and also use a fan blowing on that heat sink. Seems the Mini has a noise floor the greatly increases with heat.

Didn’t get time to try TXing the other day. Hopefully I will this weekend. Going up to Michigan to check on the house up there and its alot quieter radio wise.

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