Post · bonfire.cafe

After a little more tuning and some really valuable help from @n8dmt (!) I have a working self-designed antenna amplifier. I learned a lot. I will make a second version that has better wideband matching and is better constructed (I hope), given what I've learned. Here's the amplifier showing FM broadcast and APRS signals before and after. #HamRadio #AmateurRadio

APRS signal before and after amplification. Without the amplifier, it's below the noise floor.

Waterfall display of FM Broadcast signal showing no amplification

Waterfall display of FM Broadcast signal showing dbFS with amplifier running

Karl Matthias 🇺🇦

@relistan@mstdn.social replied · last month

@n8dmt here’s the amplifier hooked to my 2m J-pole and RTL-SDR. Bowick text on impedance matching behind. 😀

RF amplifier with antenna and SDR attached.

Gary @N8DMT

@n8dmt@mastodon.radio replied · last month

@relistan This turned out very well! “Build a RF Amplifier” Achievement Unlocked!

Thoughts on RF DIY:
1. The first one is always the hardest (generally true, but sometimes following attempts fail spectacularly). Maybe the first 10 are the hardest? Gets easier from there…
2. Perfect is the enemy of good.
3. You can’t have enough RF amplifiers, test equipment, adapter, cables, probes, or test-doo-dads.

Thanks for sharing your project and journey with us!
#AmateurRadio #RFDesign

Karl Matthias 🇺🇦

@relistan@mstdn.social replied · last month

@n8dmt Thanks again for the troubleshooting help! Was fun to share what I've been up to, as well.

Those looks like good pieces of advice on RF 😊 . I'm already thinking about the next iteration of this amp. 10 might be right... I bet it stays kinda hard for awhile!

One other thing I learned... I will buy some small surface mount inductors. That will save a LOT of time.

Gary @N8DMT

@n8dmt@mastodon.radio replied · last month

@relistan You’re very welcome! Pleased to be a part of your journey…

Yes, L&C RF parts kits are really nice. Problem is they only cover a set range of part values, and then you’ll want the next kit covering the next (larger/smaller) range, and so it goes. Soon you’ll have stacks of these kits and will save a lot of time (but spending $) to just grab the right value for your board. Winding coils is part of the “fun” experience only to a point. DIY caps are far harder. :-)
1/2

Gary @N8DMT

@n8dmt@mastodon.radio replied · last month

@relistan Today’s small USB instrumentation really is a paradigm shift over yesterday’s larger/heavier bench gear. The NanoVNA is super useful for not just VSWR/return-loss (S11/S22) and Gain/loss (S21), but also useful as a TDR / impedance probe that helps quantify RF bypass/grounding and other helpful measurements. Far better than my older scalar analyzers (being able to know where you’re at on the Smith Chart is HUGE when matching antennas/other-loads). TinySA is surprisingly useful too! 2/2

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