Antenna ferrite loopsticks verses air core?

Go read the original post. I clearly asked which was better, an air core inductor or a ferrite core of the same size . The answer should be yes this and not that, but you don't have any idea. You are just a bozo. .

Well, I'm directing the question to you since you seem to know everything. And BTW, I worked in a radio factory and adjusted maybe 1000 antenna loopsticks in transistor radios and peaked the trimmer caps at the top end and moved the coil winding on the ferrite rod at the low end to get best performance across the band. I'm not a novice. So, why don't you f*ck off? . .

Reply to
billbowden
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** Go f*ck yourself - moron.

** You just posted the DIRECT opposite.

You are pathetic moron and TROLL.

** But you ARE a complete MORON !!!

FFS - FOAD

..... Phil

Reply to
Phil Allison

Reasonable enough. The middle of the ferrite doesn't do you any good; in fact, after enough size, it's a complete drag on the system -- core losses, skin effect and dielectric loss take over!

Ferrite isn't as conductive as iron, but it still needs to be laminated if you want to use really thick sections of it at the same frequencies as usual.

This is the fundamental behind why different shapes of ferrite beads have different impedance plots, despite being the same material. Thicker and longer beads have an impedance peak at lower frequencies; the length and frequency correspond to the speed of light in the material.

Tim

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Reply to
Tim Williams

Good old Phil is not anyone you should worry with. He may know some stuff, but his manner is such that he is best killfiled. That's what I do. I see that he makes posts, but they are marked as having been read. I very, very seldom bother to read any of his crap, even when someone else quotes him.

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Rick C
Reply to
rickman

There's no comparison. That's because the two antenna designs have completely different impedances, and must feed entirely different frontend RF amps. At some frequency, with some particular input gain stage, you can't just swap those two antennas: you need to redesign the next stage as well.

Reply to
whit3rd

The gain ( = directivity x efficiency) for a typical loopstick is very bad in the order of -60 to -80 dB, due to the extremely low efficiency. But thanks to the extremely high band noise at LF and MF, you still get usable SNR with such designs.

Reply to
upsidedown

Or you simply couple the antenna to the receiver appropriately.

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Rick C
Reply to
rickman

** You have **over-snpped** and ruined the OP's question.

** The ferrite one will have a higher Q, but similar impedance.

..... Phil

Reply to
Phil Allison

** Compared to what ???

A half wave antenna 150 meters long?

** This is not right.

Whatever the inherent atmospheric noise at MF, the signal from the transmitter can over-ride it.

AM does not have inherently bad s/n unless you are DXing.

I have a hi-fi AM tuner that coupled with small frame antenna ( 40x40 cm) is capable of FM like results from good, local broadcasts.

It uses just 2 small valves.

.... Phil

Reply to
Phil Allison

I'll disagree with you on that Phil, I recently built 5 coils using 6" polystyrene pipe coupler as a form. I wound them with 660/46 wire with spacing's of 11 Turns Per Inch, 12 TPI, 13 TPI, 14 TPI and 15 TPI. All coils were between 232uh and 237uh. 10 TPI, 11 TPI and 12 TPI were pretty close, with Q at 500kHz of 1250, peaking at about 750kHz with a Q of 1450 and dropping to 950 at 1600kHz. I used a Boonton 260A Q meter and averaged 5 tests, I'll give the caveat that high Q's are elusive to measure. Your standard 61 material is to lossy to get this high, there is some lower loss material coming out of China that is performing well. The best I ever got with a #61 material was 550 Q. Now to defeat my argument, a Chinese radio amateur made a rod with 26 toroids with a Teflon core and Teflon spacers and two parallel 660/46 litz wires, measured peak Q just over 1812. Then another another duplicated his experiment and got peak Q of 2026. The material is coming from China and is R40C1. Details here,

Proving at least some of the human race, has a lot of free time.

Mikek Helmet and flak jacket in place.

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Reply to
amdx

Maybe I should have used shorter words?

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Reply to
John Larkin

I've got an AM radio that came with an air core antenna. (1990's vintage) ~4" (10 cm) squarish loop. Not sure how many turns. Works fine.

George H.

Reply to
George Herold

Yes. Gain is cheap now.

(sorry, Phil, one of those words has 5 letters.)

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Reply to
John Larkin

Please don't abuse Phil, he's our entertainment. Mikek

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Reply to
amdx

Is your real question , how do we optimize electrically-small 500KHz loop a ntennas?

:)

First, for electrically-small resonant antennas, increasing the Q will both narrow the bandwidth as well as increasing the total received microwatts. Between ferrite versus air-core loops, which one has more loss-ohms (incl uding ferrite losses, tuning capacitor slider resistance)?

Second, PHYSICAL SIZE makes a big difference. Wind your air-core antenna as a hoop-style, 5ft diameter! Or, use a 5ft ferrite rod with the winding s in the center. Both are roughly equivalent (where ideally you'd use 1/2 wavelength, 300 meters @500Khz, not 5ft.)

Reply to
Bill Beaty

Start by defining optimum.

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John Larkin         Highland Technology, Inc 
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Reply to
John Larkin

He did, as did the op, (capture the most signal) The next thing is to eliminate transmitted signals you don't want. You can reduce one lobe of the figure 8 by phasing with a vertical. Other than that not a lot you can do until you start getting a healthy part of a wavelength distance between antennas. Mikek

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Reply to
amdx

** So it's an external loop for a main powered receiver ?

You need to learn how to post unambiguously too.

IOW not smartarse style like Larkin.

.... Phil

Reply to
Phil Allison

I when the gain is worse than -60 dB, it doesn't matter if the reference is dBd or dBi, the difference is only 2 dB :-)

The effective hight for a short antenna /in this case strung into the trees) is only a few dBs below a full size antenna. For derivation, check John.D. Kraus: "Antennas"

Depending of the definition of DXing , much of the MF/HF stations in Europe has been shut down. Of course Russian propaganda stations are still going strong, but wants to listen to them :-).

You must be living very close to the transmitter.

- On SSB the SNR is the same as the RF SNR. To get 10 dB improvement in the audio SNR, you need 10 times more power-

- For strong (local) signals, this also applies to AM

- For FM transmissions the audio SNR is FM_gain + CNR (carrier to noise ratio). Above the FM threshold the cost of increasing the SNR is as costly as on AM

- for digital, going from 48 dB to 96 dB (8 to 16 bits) SNR only requires doubling the bandwidth and hence transmitter power.

Reply to
upsidedown

** Where was the over-sniping error?

Did you even think about it?

** That would be 6" diameter - right ?

The f****it OP was considering 6" *long* pipe that could enclose a ferrite rod.

The rest of you post was OT, tell me how do you get a 6" dia pipe inside a pocket size transistor radio ?

You are an idiot Mikek.

.... Phil

Reply to
Phil Allison

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