The HamBone

Just a random thought for a few inexpensive projects to chew on...
DIY KITS QRM Eliminator X-Phase 1MHz - 30MHz. $17.10. Same principle as ANC-4 from TimeWave, but PTT relay not inc. Also diversity reception. https://www.aliexpress.us/item/2255800804953692.html
FM bcast radio. Few parts. Outreach project? $18.43 Many similar at this site. https://www.aliexpress.us/item/3256805422591363.html
RTL dongle HF+ receiver kit. $24.75. Uses OS free software. https://www.aliexpress.us/item/2251832623715373.html
Also apropos RasPi shortage, I've just completed two projects replacing RasPi B and 2 with Amazon [url]https://www.amazon.com[/url] ASIN B074P6BNGZ $35 and ‎B0BQG668P6 $40. I used same GPIO header connections as RPi, but found these boards need boot code which differs from standard RPi. https://jamesachambers.com/enable-rasp ... rs-boards/ and https://www.armbian.com/lepotato/ Otherwise, all binaries were straight from RasPi. Just about as close as you can get to RasPi?


</ramble> 73, John KX4QC.

Thank you W4BRU for the suggestion to improve the QRM phaser: a T/R switch. There's a piece about diode switching at https://www.digikey.co.th/th/articles/h ... eive-modes Also includes how a PIN diode works inside.



Maybe better to do it with a relay, remembering that diode across the winding, or to heck with it just buy one of the many fine ready-made solutions, such as:

i did the first kit from the previous post, the QRM Eliminator.
"Eliminate" means "all gone", right? Hmmm....
So it was just a little project, and i built it with no problems, well one actually: "Does the darned thing work????"

Well, bearing in mind that there is not necessarily a complete answer to "The Maiden's Prayer" for noise, I hooked up my main dipole, and a really bad antenna to catch most noise. I deliberately broke all the rules: I put it in indoors, not too long, close to power and digital cables... That should be good and dirty!

Well, the unit powered up first time, no smoke, and a friendly blue LED. Next, I tuned every every band from 160 - 6m on my 7610, with wide filter and no preselector to find maximum QRM on the audio and waterfall. Then with the "QRM Eliminator". Well, did it work? Yes, and it's is a useful thing -if you dont't pay too much. There are expensive ones that work much the same, take a noise antenna and combine this signal in opposite phase with the main antenna, leaving the wanted signal uncancelled. If the interference has a greatly different phase from the wanted signal, then it mostly works well. Mine works better on 80 - 10m.

On balance, the "QRM Eliminator" is useful, even if it doesn't "eliminate all of all interfence sources, it helps with much of it.