FIX Baofengs? Build A Bandpass Filter

[@KeepEvery1Guessing]

Nice talk. But, notes: 1. If you don't have small enough capacitors, two is series gives a lower value. But if you limit yourself to two in series, the smallest you can get is half of you smallest descrete value. 2. You can measure components starting with one accurately known component, by looking at the resonant frequency of a parallel LC circuit. But you don't need super accurate values, because you should trim the filter after construction anyway. 3. Filter response is effected by termination impedance, and with a rubber duck, or even a whip, it won't be 50 ohms resistive. The harmonic suppression may not be as good as it looks on the SA. 4. Component values will be effected by the board and the enclosure. (Another reason to trim afterwards.) 5. Magnetic coupling between the inductors will mess things up, particularly ultimate rejection. Fancy filters are built with the sections each in its own box (mu metal preferred, but any conductive wall, like blank PCB material will help). 6. Having the inductors in series and the capacitors in parallel may have better high side slope. 7. You might add additional band reject sections for the frequencies of the most egregious harmonics

[@yakovdavidovich7943]

36:44 -- you lost your low pass filter because of coupling through the breadboard and stray coupling bretween the air core inductors. Capacitance between strips on the breadboard is potentially tens of pF, so the shunting elements are almost invisible to VHF and UHF. The air core inductors don't contain the flux well, and interact with each other, becoming transformers between stages. The VNA can measure inductors *quite accurately*, so use that instead of the silly LCR meter. You're using a Model T with a Corvette sitting right there on your bench.

[@jannoswanepoel2506]

Probably my favourite HRCC stream - would love to see more RF tinkering content. Never use breadboards for RF tinkering though as the parasitics of the breadboard are within the order of magnitude of the caps of the filter - I'd recommend two sided FR4 which can be obtained pretty easily, but you'll have to dip your toes into acid etching. Build the filter on the top side, and connect the bottom to ground. You can also route out traces using a dremel on low RPM and some patience. Those capacitors are also likely very lossy with a low SRF - its worth purchasing surface mount caps (1206 footprint or larger for easy soldering) with a C0G temperature coefficient. These will give you a much more ideal response. Coupling between the air core inductors can have a negative effect, however I've found this to be an acceptable trade off for the high Q of air core inductors as long as you keep the inductors far enough apart. Programs such as Coil64 can be used to design all kinds of inductors. Higher inductor Q = better filter. You can measure the inductance of an inductor by measuring its impedance at a specific frequency -> XL = 2*pi*f*L, where L is the inductance, f is the frequency, and XL is the magnitude of the impedance.

[@crazyham]

Nice, I am glad to see someone addressing this ⚡🙏⚡ Many Great Comments below too 👌

[@Daklon17]

Just today I had a failed sota activation, everybody was able to hear me, but I only could hear a couple of stations that where really close. My baofeng was completely deaf, but as soon as a I get back to the car the reception was fine again. So probably will build a 2m bandpass filter for my next activation.

[@gaylecoombs5510]

Will we need to be present during the livestream to win? Thank you for the giveaway and all you do, I've found your channel to be very informative and inspiring and it's because of you and the tech prepper that I've decided to go an actually get my license. Thank you again sir and hopefully I'll be able to hear you on the air before the end of the year

[@TheRetiredtech]

To tune your coils use a wand. Heat shrink with ferite bead on one end small brass rod or screw in the other end. Instead in coil one end at a time. If it's bette 40:19 r with ferite then compress coil. Better with brass spread coil turns.

[@frankfoduw-ci8rr]

SWL contest 2023 welcome you, we have many sponsors

[@Dusty_Ham]

Just wanted to say congrats on 300k and good luck everyone in the giveaway. Very awesome of you to give so much to the community.

[@HamRadioCrashCourse]

Thanks!

[@tomKZ8TOM]

@hamradiocrashcourse Josh, The drawing date in the official sweepstakes rules, paragraphs #5, needs to be updated as the drawing date refers to a past date of: July 13, 2023 9:00pm PST. 73

[@mozee06]

I wanted to leave a joke about the incorrect contest date in the rules, but you're even taking a beating in the regular comments outside of the live chat, so I'll give you a break! Glad I was finally able to work you on FT8 during the after chat stream!

[@TMS5100]

Baofeng sells compliant radios that are only like $20 more than a noncompliant UV-5R that splatters all over the place. And compliance means more than just dBc, look at the FCC regs - you need to be

[@requited2568]

Think the BFTech ones are FCC compliant with some newer settings.

[@HamRadioCrashCourse]

Actually, MANY baofengs exist that easily meet fcc standards.

[@TMS5100]

@@HamRadioCrashCourse many of the baofengs you said meet the fcc standards on this channel actually dont. they fail the

[@haxwithaxe]

An audio queue of some kind when you show the code would be nice. Anyone who is mostly just listening (or can't see) can miss it pretty easily.

[@DonzLockz]

Awfully generous Josh!😮 It will be the best Xmas present for some lucky HAM's!😊👍

[@11ccom]

pythagorean theorem right triangle a^2 + b^2 = c^2

[@TheRetiredtech]

Your cna is the best LC meter you can buy.

[@juanpabloish1]

Not all attenuators are bidirectional, some of them are unidirectional

[@aquilafasciata5781]

Hey Josh, looks like you may need to update the language on the Winners Selection part of the form. It states the drawing is happening in July 2023 💀

[@johntorta9758]

good job

[@johnwest7993]

While I find your video and what you are attempting to determine to be a bit confusing, at about 44:00 minutes you are comparing a receiver with no antenna to one with a filter that appears to be in a plastic box. In other words, a poor antenna, but an antenna nonetheless. The interconnecting lead from the filter going into the radio at the chassis is more antenna than the first test with none, causing the filter to appear not to work. Do the test at a distance with weak signals and with an antenna and the filter will show the harmonic attenuation depicted on the NanoVNA.

[@sissys6284]

Just discovered your channel and I love it. You have great information. Can't wait to tear into the exam cram. Thank you so much for all the great information. Cheers! 🎉❤

[@HamRadioCrashCourse]

You can do it!

[@alsanderson4917]

How do I build a "sad ham" filter?

[@HamRadioCrashCourse]

Don’t read the KZbin comments. Boom filtered out the sad hams

[@davidmckayii752]

Cool

[@Jimbo_Conn]

So I was wondering why my uniden hand held scanner can pick up local repeaters and local activity that my UV 5R picks up NOTHING AT ALL! Even with better antennas... So just yesterday I come across a forum post where a guy is complaining about the same issue with boofwaangs ...he seems to think he actually gets better receiving with a worse or smaller antenna and also seems to find that an "FM inline filter" got it to work to pick up his local repeater.....hmmm And woollah...now I'm here on your recent upload...cause I know nothing about filters or FM inline filters.... Is this really an answer? Is it odd that my feng can't even pick up a local repeater? Is it a problem with the radio possibly? 🤙

[@bringinghomethebananas]

Try a helical notch filter. I built a helical notch filter in a cookie tin for 2M that made all the difference in my stupid Baofeng in the city with tons of RF. The curve on the VNA is textbook. The helical filter is physically large, but my goodness the performance is excellent.

[@jamesmartin5306]

Hey Josh I’m still studying for my tech test but I have someone trying to tell me that I can use a baufung to transmit a test emission with out having my license I told them to fly a kite 🪁 😂