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.
Inexpensive contstruction projects.
Inexpensive contstruction projects.
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Last edited by KX4QC on Sun Jun 25, 2023 1:30 pm, edited 1 time in total.
Re: Inexpensive contstruction projects.- T/R switch?
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:
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:
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Re: Inexpensive contstruction projects. - QRM Eliminator
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.
"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.
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