diy 40uHy inductor - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: December 03, 2023, 07:03:31 am
content: can anyone tell ne how to nake a 40uHy fixed inductor for an hf bias t ?.

author: fourfathom
author_rank: Super Contributor
timestamp: December 03, 2023, 07:20:34 am
content: That's a big inductor for a HF bias tee. Assuming a 50 Ohm system and a 3.5 MHz low-end, you can probably get away with something closer to 12uH (that's about 260 Ohms XL). But if you want 40uH, that's about 10 turns on a T37-43 ferrite toroid core. Seehttps://toroids.info/FT37-43.phpfor info on winding toroid inductors.

author: A.Z.
author_rank: Super Contributor
timestamp: December 03, 2023, 04:44:03 pm
content: or either he may wind thishttps://hackaday.com/wp-content/uploads/2017/06/800px-large_antenna_loading_coil.jpgand tap the coil

author: fourfathom
author_rank: Super Contributor
timestamp: December 03, 2023, 06:06:28 pm
content: That air-core inductor is much to too small to work with my bias-tee coupling capacitor:

author: A.Z.
author_rank: Super Contributor
timestamp: December 03, 2023, 06:51:36 pm
content: well, you may use two or more of them in series, but... are you going to build a replica of the Grimeton SAQ?Or maybe just an L match for an ELF antenna?!?

author: coppercone2
author_rank: Super Contributor
timestamp: December 04, 2023, 03:32:19 am
content: wtf is that picture of the hanging things? are those metal sheets?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: December 04, 2023, 04:56:02 am
content: Hi,Those hanging metal sheets are a capacitor.Jay_Diddy_B

author: Andy Chee
author_rank: Super Contributor
timestamp: December 04, 2023, 05:41:15 am
content: Quote from: coppercone2 on December 04, 2023, 03:32:19 amLooks like a building sized version of this:https://youtu.be/5Ji7RJxi4vc?t=789

author: coppercone2
author_rank: Super Contributor
timestamp: December 04, 2023, 06:16:59 am
content: is that for a high voltage discharge lab or a radio lab? the first is known to me, kind of, but if its part of a transmitter that is not just a pulse that would be interesting.I was hoping it was for a CW signal, not a impulse gen

author: fourfathom
author_rank: Super Contributor
timestamp: December 04, 2023, 06:34:26 am
content: Quote from: coppercone2 on December 04, 2023, 06:16:59 amThat is a tank capacitor for Marconi's spark-gap transmitter at Clifden Ireland (https://ewh.ieee.org/reg/7/millennium/radio/radio_differences.html).I've been doing multiband SDR receiver work at radio station KPH in Pt. Reyes, California, which was across the (Tomales) bay from the Original Marconi receiver site. KPH needed more area for their antennas, so they moved to the "new" location in 1929 (https://www.nps.gov/pore/planyourvisit/kph_treetunnel.htm#:~:text=The%20Historic%20KPH%20Maritime%20Radio,Tomales%20Bay%20in%201913%E2%80%9314.). This new site was chosen by Harold H. Beverage (inventor of the Beverage antenna). KPH is now a historical site, no longer used commercially but maintained by a Ham Radio organization and the US National Park Service.

author: p.larner
author_rank: Frequent Contributor
timestamp: December 04, 2023, 09:50:39 am
content: its for a bias t to use with an atu-100 atu kit built tuner,so i can sit the atu on the mast outside.100w tx max,about 300ma when the atu tunes.

author: A.Z.
author_rank: Super Contributor
timestamp: December 04, 2023, 11:19:19 am
content: Quote from: p.larner on December 04, 2023, 09:50:39 amsee the attached schematic (and infos) from Phil Salas (AD5X), that one should suffice, if not, you may look at thishttps://www.hayseed.net/~jpk5lad/K5LAD%20Memories/Vols%2031-35/Memories--Vol33.htmnotice that, willing a "belt and suspenders" approach, you may consider using "Y2" class capacitors for the two series caps on each unit, such capacitors have a "fail open" requisite, so in case the cap fails the DC won't reach the rig (or the antenna port)

author: LM21
author_rank: Regular Contributor
timestamp: December 04, 2023, 06:32:57 pm
content: I use this to calculate a bit smaller coilshttps://hamwaves.com/inductance/en/index.html#input

author: nali
author_rank: Frequent Contributor
timestamp: December 04, 2023, 06:43:57 pm
content: Quote from: p.larner on December 04, 2023, 09:50:39 amAren't you a M3 foundation licence holder? You're operating outside your licence power limit of 10W if so.

author: wilhe_jo
author_rank: Regular Contributor
timestamp: December 04, 2023, 08:45:03 pm
content: You could look into smd inductors.Coilcraft 4x 1812LS-123 should work.Another way is stacking inductors.So 33u up to maybe 10MHz.Another 10u up to 30MHz.And then maybe 1u up to 100MHz.That'll give you a relatively flat impedance.Many power inductors have their SFR (self resonance frequency) in heir datasheet.I did a 50uH air inductor for a LISN (EMC measurement).It's not easy to make good inductors up to 30-50MHz (ok, my was designed for 100A+..<1A will be easier).You'll fight resonances for sure... Using smd inductors is way easier.73

author: vk4ffab
author_rank: Frequent Contributor
timestamp: December 04, 2023, 09:14:10 pm
content: Quote from: nali on December 04, 2023, 06:43:57 pmI think you will find he is planning ahead for when he upgrades. We know he is currently not transmitting at all because his antenna install is a nightmare and causing issues he cannot currently solve. So lets not insinuate he is doing anything wrong. If it was me i would put a KW rated remote tuner there and design the bias t's to suit, might as well plan for the future even if you are running 1W.

author: A.Z.
author_rank: Super Contributor
timestamp: December 04, 2023, 09:20:17 pm
content: Quote from: vk4ffab on December 04, 2023, 09:14:10 pmyet, he's asking for help, his way sure. but he's trying, so instead of just hammering him, let's try and see...and then, if everything else fails, there are the rettysnitch, the wouff-hong and the one I won't dare to name

author: p.larner
author_rank: Frequent Contributor
timestamp: December 05, 2023, 04:11:47 am
content: firstly to nali because its an atu-100 does not mean you need to tx at 100watts,and how does that answer my question on an inductor,are you the radio pigs/police,if so get a life as the one you have looks broken!.

author: coppercone2
author_rank: Super Contributor
timestamp: December 05, 2023, 09:50:46 am
content: kinda sad because over rated parts bring some modicum of reliability instead of a spring loaded surface mount low power cracker with 46 awg wirejust put a fuse on it if you are worried about over transmitting

author: nali
author_rank: Frequent Contributor
timestamp: December 05, 2023, 09:52:43 am
content: Quote from: p.larner on December 05, 2023, 04:11:47 amOo... touched a nerve there?? No I'm not the radio police - we have Ofcom for that - but I'll concede it is a little bugbear of mine people abusing the privilege of their amateur radio licence. Just a hunch based on your general attitude, language and posting history e.g. the recent thread about ATU flashover. I get the feeling you've mentioned 100W before but frankly ICBA to check.I haven't bothered to answer your OP because you reject any answers which don't fit the tiny criteria of what you think the answer should be. TBH, I would expect anyone deemed competent enough to hold a AR licence to be able to do (or search) something as basic as winding an inductor but there you go, sign of the times I guess.Oh, and my life's just fine thanks. In fact I'm off to live it rather than waste any more time in this thread!