diy 40uHy inductor

[p.larner]

can anyone tell ne how to nake a 40uHy  fixed inductor for an hf bias t ?.

[fourfathom]

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 X_L).  But if you want 40uH, that's about 10 turns  on a T37-43 ferrite toroid core.  See https://toroids.info/FT37-43.php for info on winding toroid inductors.

[A.Z.]

or either he may wind this

https://hackaday.com/wp-content/uploads/2017/06/800px-large_antenna_loading_coil.jpg



and tap the coil

[fourfathom]

That air-core inductor is much to too small to work with my bias-tee coupling capacitor:

[A.Z.]

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 ?!?

[coppercone2]

wtf is that picture of the hanging things? are those metal sheets?

[Jay_Diddy_B]

Hi,

Those hanging metal sheets are a capacitor.

Jay_Diddy_B

[Andy Chee]

wtf is that picture of the hanging things? are those metal sheets?

Looks like a building sized version of this:

https://youtu.be/5Ji7RJxi4vc?t=789

[coppercone2]

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

[fourfathom]

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

That 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.

[p.larner]

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.

[A.Z.]

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.

see the attached schematic (and infos) from Phil Salas (AD5X), that one should suffice, if not, you may look at this

https://www.hayseed.net/~jpk5lad/K5LAD%20Memories/Vols%2031-35/Memories--Vol33.htm

notice 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)

[LM21]

I use this to calculate a bit smaller coils
https://hamwaves.com/inductance/en/index.html#input

[nali]

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.

Aren't you a M3 foundation licence holder? You're operating outside your licence power limit of 10W if so.

[wilhe_jo]

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

[vk4ffab]

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.

Aren't you a M3 foundation licence holder? You're operating outside your licence power limit of 10W if so.

I 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.

[A.Z.]

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.

Aren't you a M3 foundation licence holder? You're operating outside your licence power limit of 10W if so.

I 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.

yet, 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

[p.larner]

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!.

[coppercone2]

kinda sad because over rated parts bring some modicum of reliability instead of a spring loaded surface mount low power cracker with 46 awg wire

just put a fuse on it if you are worried about over transmitting

[nali]

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!.

Oo... 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!