Essential Amateur Radio Components - Page 1
Forum section: electronics / rf-microwave

author: DrMag
author_rank: Regular Contributor
timestamp: June 20, 2017, 01:34:24 pm
content: I'd like to start learning to design and build RF circuits. A lot of the tutorials and examples out there, unfortunately, use out of date and hard to find components; I plan to document what I do and try to "modernize" amateur radio homebrew tutorials a bit. To that end, I'm gathering the pieces I need to experiment and learn.Aside from the obvious passives, what components do you think are essential for learning RF circuits?Here are a few I've been considering:Si5351(a/b)SA612SA614MAX2605/MAX2606Are there specific transistors that are "jelly bean" enough for RF work?

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: June 20, 2017, 01:51:12 pm
content: For HF work the following transistors come up in numerous homebrew designs (in ascending power capability):BC548 or 2N39042N2222A (preferably the metal can type)2N3053BD139IRF510For upper HF or VHF you sometimes see the following specified (unfortunately more expensive and harder to find)2N51792N38662N44272N3553The MPF102 is a commonly used small signal FET. 2N3819 is another.Dual gate FETs are often used in RF converter or amplifier circuits. Eg BF981. Or older MFE131 or MPF121 or 3N201.

author: CJay
author_rank: Super Contributor
timestamp: June 20, 2017, 03:12:17 pm
content: Quote from: DrMag on June 20, 2017, 01:34:24 pmSA612, SA602, NE602 and NE612 are all equivalent apparently.Wot VK3YEDOTCOM said applies for transistors but the metal can ones are very long in the tooth even though they're easy to get hold of at the moment.Might be worth having a look at the GQRP club part sales spreadsheet and of course cross reference any parts you find for sale against places like Farnell, just to get an idea iof you're buying NOS or current production as well as potential EOL information.

author: medical-nerd
author_rank: Regular Contributor
timestamp: June 20, 2017, 10:17:45 pm
content: Spectrum Communications in the UK has a useful range of 10mm TOKO compatible coils that you will need if building older designs for shortwave radios.....Look up antonnaile-0 on ebay.I have no association, just a very happy customer.Cheers

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: June 21, 2017, 12:26:03 pm
content: Other useful components include:T50-2 and T50-6 toroids (red and yellow, yellow better for higher HF) Good for RF filtering and tuned circutsFt50-43 toroids. Good for broadband transformers and baluns and interstage coupling.Axial style RF chokes. Various values including 1, 2.2, 3.3, 4.7, 6.8, 10, 22, 100, 1000uH. Lower values are good for tuned circuits, higher values for RF chokes.Ceramic resonators, preferably in the amateur bands. Eg 3.58, 3.69, 7.16, 7.2 MHz etc. Allow frequency agility with acceptable stability.Crystals. Various combinations are good for SSB filters.Polystyrene capacitors (if you can get them). Good for pi network low pass filters in transmitters.60/160pF variable capacitor. Good for use with VXOs or receiver preselector tuned circuits.

author: DrMag
author_rank: Regular Contributor
timestamp: June 21, 2017, 06:58:07 pm
content: Thanks, everyone! Your comments have been very helpful.If I limit myself to VHF/UHF design (not really--I know HF will be a better (easier) place to start), does that change recommendations? Inductor/capacitor sizes at VHF start to get quite small; are there any secrets to that? What about at UHF?

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: June 21, 2017, 08:23:42 pm
content: Quote from: DrMag on June 21, 2017, 06:58:07 pmYes. Transistors will be different, rarer and more expensive. Possibly greater use of FETs. You'll need lots of small trimmer capacitors (say 5 - 40 pF and 2 - 20 pF). Iron powder toroids are less used, although you may still use ferrite baluns and small ferrites for RF chokes. Inductors will be air cored and self supporting so you'll need lots of enamelled copper wire. Though for UHF more use is made of them etched on circuit board. In addition one can never have too many low value disc ceramic capacitors (1 - 100pF) for tuned circuits and coupling. Diodes for RF mixers may be more specialised than the 1N4148 used on HF. Crystal oscillator modules are sometimes useful for RF converters. Something like an RTL2832 dongle can form a useful wide range VHF/UHF receiver for testing etc.Superregen FM receivers can be a bit temperamental but can be a good first VHF project.If you're too lazy to build a transmitter/receiver from scratch low powered UHF modules can be fun and give surprising range (especially if used with a better receiver).

author: cdev
author_rank: Super Contributor
timestamp: June 25, 2017, 03:57:31 pm
content: Its changing sooo quickly, it seems to me.