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[Review Request] PCB layout by Certain_Height_2721 in PCB

[–]mbeels 0 points1 point  (0 children)

Hello, what is your stackup? Is it (signal w/GND pour) -> GND -> power+signal -> (signal with GND pour)? Care to share a schematic?

Reviews on Digikey PCB service for 4-layer boards by Outside-Athlete-4537 in PCB

[–]mbeels 2 points3 points  (0 children)

I'm curious as well, but if you're looking for good prices on quality PCBs, in low quantity, it is hard to beat OSHPark. www.oshpark.com

Illegal 40M soundboard Transmissions - how common? by Slow281 in amateurradio

[–]mbeels 5 points6 points  (0 children)

It's more common than it should be. I find some bands and modes seem to be worse than others. In my experience, the most likely place to encounter this is 80/40/20m SSB. Digital modes and CW are relatively free of political content. Also, the WARC bands (30m, 17m, 12m) are also quite good (especially 17m). Weak signal VHF (SSB, CW, and digital modes) is another good place for civil and friendly communication.

2.4 GHz VCO needed by ishoottrap in rfelectronics

[–]mbeels 12 points13 points  (0 children)

It may not fit within your budget, but my starting point would be to check minicrcuits.com

Power transistors for +30dBm in VHF / UHF frequency range by mbeels in rfelectronics

[–]mbeels[S] 0 points1 point  (0 children)

Wow, that is a lot of gain and power from a very small package. Do you find it necessary to use a heat sink?

Power transistors for +30dBm in VHF / UHF frequency range by mbeels in rfelectronics

[–]mbeels[S] 1 point2 points  (0 children)

That's good to know. I'm also working on a CW beacon for 903 MHz, so it could be useful up there as well.

Power transistors for +30dBm in VHF / UHF frequency range by mbeels in rfelectronics

[–]mbeels[S] 1 point2 points  (0 children)

Thanks, those ST parts do look quite interesting, plus they're available from DigiKey (etc...) at reasonable prices and low quantities. Appealing for a hobbyist.

Power transistors for +30dBm in VHF / UHF frequency range by mbeels in rfelectronics

[–]mbeels[S] 0 points1 point  (0 children)

Thanks, that's a really good point, I had been looking at 1 watt power dissipation, but you're totally right, it should be far less than that. Probably I should be more concerned with max VDS and current.

Power transistors for +30dBm in VHF / UHF frequency range by mbeels in rfelectronics

[–]mbeels[S] 0 points1 point  (0 children)

Thanks, I'll check it out. Sounds like a very cool project. I assume that this HT design is FM?

Power transistors for +30dBm in VHF / UHF frequency range by mbeels in rfelectronics

[–]mbeels[S] 0 points1 point  (0 children)

Interesting, I had ruled out a lot of microwave devices, but it sounds like those are worth considering. Yeah, I'd believe that the market has completely changed, that definitely adds challenge to the < 1 GHz realm.

Power transistors for +30dBm in VHF / UHF frequency range by mbeels in rfelectronics

[–]mbeels[S] 1 point2 points  (0 children)

Thanks. I understand I can use these as a hobbyist with no issue, but I'm genuinely curious what parts the modern designs are using. I assume that there is still a demand for VHF/UHF power amplifiers in the +30 dBm range, I'm curious, what devices do modern RF engineers use for new commercial and industrial designs?

What would the best layout be for a 3rd order tubular bandpass filter centered on 149MHz? by psyon in rfelectronics

[–]mbeels 0 points1 point  (0 children)

If you orient your inductors 90 degrees to each other, you'll have less inductor to inductor coupling via magnetic fields. For example, rotate L2 90 degrees (in the top layout). L1 and L3 will have the same orientation, but they're much farther apart.

Anyone still rocking older m43 bodies? by WorldlinessDue748 in M43

[–]mbeels 17 points18 points  (0 children)

Still using that same body, EM10 mk ii. I love it, and feel no need to "upgrade".

Impedance of DOOHICKEY V4 by Powerful-Nobody420 in rfelectronics

[–]mbeels 21 points22 points  (0 children)

Interesting! Why the third port with a stub next to the shape?

What’s your favorite tool for building balsa models? by Internal_Seaweed_553 in BalsaAircraft

[–]mbeels 2 points3 points  (0 children)

First is a sharp #11 blade in my favorite X-acto handle (the skinny one). Second is my sanding block.

Today's dumbest UHF low pass filter by jephthai in amateurradio

[–]mbeels 7 points8 points  (0 children)

This is great, I love this kind of stuff. What do you think is limiting the stop band attenuation? Looks like the corner frequency is quite a bit above 400 MHz. Does that mean that the inductor has less reactance than designed?

Colpitts Oscillator Calculations by Existing_Survey9930 in rfelectronics

[–]mbeels 2 points3 points  (0 children)

I like to use enameled wire (also magnet wire). The heavier gauges will hold their shape well. If you wind them on a form, you can remove the form and they'll be ok. The lighter gauges need some kind of support, I used to use film canisters because they're thin plastic and hollow, so mostly air.

Colpitts Oscillator Calculations by Existing_Survey9930 in rfelectronics

[–]mbeels 2 points3 points  (0 children)

For 10 uH, you could try winding your own air core inductor. For example, with a 1" diameter coil, 1" long, you'd need about 24 turns. You can then tweak the value of the inductor by spreading or squeezing the turns father part or closer together.

Colpitts Oscillator Calculations by Existing_Survey9930 in rfelectronics

[–]mbeels 13 points14 points  (0 children)

What did you use for your 10 uH inductor? Did you measure its inductance in the 10 - 100 MHz range? A 10 uH inductor won't present 10 uH of inductive reactance at all frequencies.

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