I'm really not that interested in VLF, but you seem to be able to make any subject interesting. You have a real talent with communication, to a level that I seldom see on KZread.

@hobbified

4 жыл бұрын

VLF is 3 - 30 kHz. LF is 30 - 300 kHz. 630m (475 kHz) is MF.

@porkyfedwell

3 жыл бұрын

@Watson Orlando They have movies about the 630 meter band? Or are you just spamming?

Can't wait to see the on air test. Great project Kevin. These project's really make your Channel special. You really demonstrate your ingenuity and perseverance. 73, George K2WO

I think you struck Gold in your experience ,you have BROUGHT a better understanding to signal arrangement!!!

Have made three Magnetic loops so far, I think they are by far the best antennas for their size for portable operating, Yes, they have narrow bandwidth and take a little more time to deal with tuning, however, the super narrow notch bandwidth is great for reducing noise and not needing an antenna tuner, never have to worry about high vswr attached to your antenna as an analyzer gets you close before transmitting.The 5 to 6 ft diameter 3/4" soft copper loop is - 30 meter to 75 meter loop, has a 10 kv air variable that is very touchy, can handle roughly 300 watts max. The 20 meters to 10 meters 3 ft. diameter 1/2" soldered copper octagon uses surplus 5 kv vacuum variable cap. Can handle about 150 to 200 watts and uses a scrapped canon printer motor and belt & gear reduction with a cable to a 3 watt 1k potentiometer and a 3 position DPDT switch to change directions to tune remotely, I will continue making improved designs, totally worth the time to use as they break down and set up very quick, 3 to 4 minutes and are relatively not picky about what is near them. 73's great vid👍 and no my profile name is not my call sign.

Really interesting to see your progress through the project to get on 630 meters. Many thanks for the videos and good luck for some contacts on the band. 73

Wow... good job! That is quite a tuning capacitor. Looking forward to the actual "on air" test.

I made this back in the 1980's for my AM swl'ing and WOW you really could just turn the antenna and suddenly things disappeared and stations rang out. Was a game changer.

OK you've inspired me. Now I have a 5-turn 4m diameter magnetic loop in my attic. I've just used all available space. 1m coupling loop. SWR is 1.2. 73!

what can I say , your videos are always so good ..... KM4BAP

Extremely admire.

New ham here, been really enjoying your content lately :)

As I recall at one time a hot shot setup that didn't take up a lot of room for 160 meters was a mag loop for receiving and a base loaded vertical for TX. The loop being immune to a lot to qrm and qrn was a plus if you can't hear them you can't work them ; )

Fun video Kevin. Very interesting! Another way to reduce arcing in the loop tuning cap, when used with QRP, is to reduce your output power to QRP level: 5 watts. I couldn't resist, Kevin, given our past discussion on the topic! Haha. The all-knowing oracle known as Wikipedia correctly points out that it is generally accepted that with QRP, the transmitter output power will be 5 watts or less. No mention of ERP. Anyways, keep up the fun work down there Kevin!

@loughkb

6 жыл бұрын

Well, my TX is only driving 6 watts. I'm pretty sure the multiple turns on the outer loop is raising the RF voltage significantly.

fb WB5MZO loops are a learning experience...my big one is the 15 foot loop for WWVB :)

Years ago I built a 40” box loop for MW rx and with that it had 7 turns and the centre on had the pickup loop wrapped round it ... that worked well ... wonder if you tried that Kevin?

16 turns and what do you get?🎜 Another day older and deeper in debt.🎜 St. Peter don't tell me that I cant go🎜 I owe my soul to an old radio🎜

Any chance of putting up a loop that follows the outer perimeter of Ft. Wayne? :)

I have the same problem to disabled to keep the antenna working

Cool. Double sided board with a brass rod carrier?

if you have an old VEGA Selina that is totally broken then the variable capacitor from it should work well.

Hi Kevin, another great video. When you were playing with the position of the top-of-the-laundry-basket, did you also try to put it perpendicular over the top, so it like, balances, on the top of the antenna, to see if that might improve or is it then just getting worse? Curious about it, don't have a loop myself (yet), but who knows. Good luck with getting your first contact on 630m from PC4AD

@loughkb

6 жыл бұрын

No, that wouldn't work. The two coils have to be on the same plane so their magnetic fields can couple together.

Great video. Did you get to make any contacts ?

Have you given thought to inter turn capacitance? Could degrade TX efficiency. Spacing turns further apart could help. Also standard wire could lead to high resistive losses.

@johnwest7993

2 жыл бұрын

The way to reduce inter-winding capacitance is to make the end caps with offset slots, deeper then shallower for each turn so that the windings beside one another aren't parallel. They form a 'tall' X. It's usually done with large loading coils and an odd number of wooden pegs to support the winding being wound in and out each turn and is called a 'basket-weave' wound coil. I'd say about an inch difference between every other slot would be about right. It would be easy to do on this crossed frame with 3D printed end plates for the staggered depth slots. But basically that allows you to take some of the capacitance out of the inductor so you can put it into the variable capacitor so you can tune the antenna over a wider range. I don't know how that would work out with SWR's and transmitting, but with the giant air-variable cap he sure has the right parts to find out. I'm jealous of that capacitor. It's gotta be worth more than my whole (tr)usdx QRP transceiver.

Hi Kevin, Ever thought of using ferrite sticks to reduce the size of the antenna? This material should work great for Rx at 630m, but I am not sure how it does for Tx. 73s OD5VLM

@loughkb

6 жыл бұрын

I've seen a couple of references to attempted ferrite rod transmitting antennas in the past. The impression I got was that it did not TX well at all, and had to be quite large (relatively) to work. Power was limited due to the core saturating and also heating. Here's an article on one. www.zs6wr.co.za/anode/AnodeSeptember2009.pdf

@lucienberton4538

6 жыл бұрын

Will do. Thank you. Great work, I'm a frequent visitor.

have you got an all band HF loop video?

What effect does the spacing between the windings have on the antenna? What would happen if they were packed together? I guess it would increase the capacity, but what are the consequences?

@hobbified

4 жыл бұрын

If you wind the turns close together, proximity effect will increase the loss resistance and hurt efficiency. You need the distance between turns to be several times the conductor diameter before proximity effect becomes negligible.

Hi Kevin, Nice build. I calculate 132 ft of wire. Have my FT450 set to 474KHz. 73 WB3BJU

@loughkb

6 жыл бұрын

35" per side, times 4 = 140 inches per turn. Times 16 turns = 2240 inches of wire total, divided by 12 = 186.66 feet. How'd you get 132? I'm confused.

@DonDegidio

6 жыл бұрын

Hi Kevin, Way I worked it out was you said 35" across divided by 2 will give you 4 isosceles triangles with 17.5" on two sides. Since 90° triangle, the hypotenuse will be 1.414 times 17.5" = 24.75" times four total triangles = 98.98 times 16 turns = 1583.68" divided by 12 = 131.97 ft. 73 WB3BJU

@loughkb

6 жыл бұрын

No, 35" per side, 4 ft across corner to corner.

@DonDegidio

6 жыл бұрын

OK, then my calculations were wrong. I thought the spreaders were 4 ft.

Some JT would be the go. Listen for yourself on the online SDR receivers.

@loughkb

6 жыл бұрын

I've been listening on the web SDR's around me. Nothing heard. No surprise though, it's probably only radiating a couple hundred milliwatts due to the very low efficiency. I have made one local contact so far though, working on the video tomorrow.

Kevin, did I hear you say your were operating CW at 700 "cycles"? What are you doing up there?

Kevin, how did you size your Faraday loop? Is it 1/5 or 20% of loop circumference?

@loughkb

5 жыл бұрын

I started with that but could not get the SWR down. I think I went with a larger Loop, sizing it up until I got a good match.

Great antena construction, can I copy that? I'm from poland, so, i don't thing that we have any chance of contact, but have luck! It's will be nice to hear about sukces of this project. While watching your series about 630m band, i thing, that i shoud do something with this band, before i start in 2200m. Good luck, 73! De SP5SIO And, sory about my english. I'm not an native spiker. :P

@loughkb

6 жыл бұрын

Sure, you can copy it. It's a really good receive antenna, but not very efficient for transmitting. I did make one contact so far, a local guy. Big loops at these low frequencies drop into the single digits in efficiency, so this loop might only be 2 or 3 percent efficient. It is radiating, but with 6 watts in, I'm probably only getting a few hundred milliwatts out. It's a tough band to get on.

What transverter did you use

Kevin, what do you think would happen if you used a 16 turn coupling loop (functional 1:1 transformer), in order to avoid stepping up the RF voltage and avoid capacitor arcing? Do you think that it might still work as an antenna?

@loughkb

6 жыл бұрын

That's an interesting idea. I think the multi-turn coupling loop would act like an inductor though and throw the whole thing out of whack.

@jakebrodskype

6 жыл бұрын

Kevin, I was thinking the same thing. It might be worth a try with a small diameter coupling loop, say about the size of what your original single turn loop was. And I know you probably don't want to hear about it, but... Seeing that you were only using half of that big EF Johnson capacitor, why use the whole thing and then lower the number of turns in your loop. Your Q might go up as would your radiation efficiency.

@YinYangDPW

6 жыл бұрын

Really enjoy KB9RLW's videos - especially seems to be a mag loop guru - regarding the RF transformer effect issue between the main and coupling loop, my initial off-the-cuff observations are as follows: Main loop turns > coupling loop turns = a voltage step up, current step down RF transformer in main loop secondary Main loop turns = coupling loop turns = a 1:1 ratio transformer as Braden said, main and secondary equal voltage and current Main loop turns It is said that "current flow" in an antenna is what generates the emitted field, (at least for antennas that primarily work off of the "electric field" component of a radio wave, but have seen claims that the same is true for "mag loop" antennas as well, ie, MAXIMIZE current flow throughout the entire loop, end to end), so it seems to me that a RF transformer voltage step down - current step up ( where the number of turns in matching loop EXCEEDS number of turns in main loop would be desirable - this will lower the voltage on the cap as already suggested, and increase the current in the main loop generating a stronger field. This implementation also uses less conductor (wire, copper tube, whatever) to reduce costs. Main loop should be heavier gauge to handle larger current RF amps, while matching loop is smaller gauge just large enough to handle feed current / voltage. The reason for so many turns (16) in main loop seems to be to generate inductance (inductance always electrically shortens an antenna), but this inductance could be added to a single or just a few main loop turns with inductance coils embedded in the length of main loop turns, or at one end. I suppose as inductance coils are added, one gets the "lossy" effect as seen in multi-band trap antennas. 73 K0DPW

@loughkb

6 жыл бұрын

OK guys, I tried it. Wound a 16 turn coupling loop to match the turns on the outer loop. Results were mixed. I was able to get the SWR down from 1.3:1 to 1:13:1 so I was hopeful. Transmitted and radiated power according to the field strength meter was just a tad over half what it was with the single turn loop. Sooooo, not an improvement in radiated power. It may have reduced the RF voltage, but I didn't try the smaller cap after seeing the power go down. Went back to the single turn loop. I've got one contact on it so far, we'll see what tonight brings.

@YinYangDPW

6 жыл бұрын

With 16 turns in matching loop and 16 turns in main (secondary) loop, the ratio has been reduced to 1:1 - voltage and current in both loops should be about equal (assuming a good magnetic transformer coupling between the two coils), differing only due to resistance losses from difference in conductor lengths. While the following statement seems to contradict transformer accepted theory, it is true that as voltage increases, current increases according to ohms law, given all other things being equal, ie, resistance and inductance. "Since the current is set by the values of the voltage and resistance, the Ohm's law formula can show that: If we increase the voltage, the current will increase. If we increase the resistance, the current will reduce." So, with more turns in main loop and less (one) turn in matching loop, a "voltage step-up" RF transformer is created, and this increase in voltage will cause more current to flow in main loop (this is what seems contradictory to transformer law even though it is consistent with ohms law); but when you reduced the ratio to 1:1, now voltage is reduced in main loop to approximate voltage in matching loop, therefore according to ohms law, current also decreases to approximate current in matching loop, which is why measured field strength is much lower; ie, no amplification of any type is present. To really get the "transformer" effect of a voltage step-down, current step-up result, the matching loop must have MORE turns than the main radiating loop - try doubling to 32 turns in the matching loop - according to transformer theory that should reduce the voltage in the main loop to about half the voltage in the matching loop, but double the current in the main loop to be twice the current in the matching loop. Again, this seems to contradict ohms law, that basically says as voltage increases, current also increases; but, transformer theory has been proven over and over again. As said before, flowing current in an antenna is what generates the radiated field, more current, stronger field, therefore the goal is to maximize current. In a mag loop, there is vast difference in inductance (therefore inductance reactance) between the two coils, due to size issue alone ( 1:5 ratio), which surely has an effect on the over all system. circuitglobe.com/difference-between-step-up-and-step-down-transformer.html#ComparisonChart circuitglobe.com/difference-between-step-up-and-step-down-transformer.html#KeyDifferences www.allaboutcircuits.com/textbook/alternating-current/chpt-9/step-up-and-step-down-transformers/ 73 - K0DPW

I think you need to make your own cap.

@loughkb

6 жыл бұрын

Exactly what I've started doing. Cutting up PCB material for the plates and 3D printing the frame.

Hi Kevin, Missed it tonight at 02:00. Was helping my dad get ready for sleep. Will you be trying it again tomorrow night? 73 WB3BJU

@loughkb

6 жыл бұрын

Every night for a couple of weeks.

Can you show your transmitter? Did you build one?

@loughkb

3 жыл бұрын

Yes. Search my channel for 630 and you'll find a series of three or four videos on my 630 meter CW transmitter.

Back pains are the worst. Sorry. I feel that my legs are gone. Lumbar troubles

Kevin: While I can not TX on 630 M, I will try to find and record your signal. I am also going to post your video link and request for others to monitor and perhaps try to make contact on our club's Yahoo user group page. 73 John-KB3SVJ