QRP Magnetic Loop Antenna on CB radio. (Have a problem) Part 1

[@Delta_Dave_UK-]

Thank You Fred for all your work for the fantastic C.B Radio community.

[@CB-RADIO-UK]

Thank you too!

[@RingwayManchester]

Thanks for this Fred!

[@PaulTaylor1]

It looks more like a receiving antenna, as it doesn't have the little coupling loop that transmitting mag loops normally use. Anyhow, you might find that you have to retune for each CB channel if you QSY - not a problem for the 305 net etc. that you go on. Looking forward to Part 2! 😊

[@CB-RADIO-UK]

Thanks Paul. Yes it does lack a coupling loop which ive seen on other designs.

[@bill-2018]

There are various ways of matching a loop. G4GHB.

[@antenaseinterfacescb]

Very interesting video, with a nice magloop. I home made one Mag Loop with 1,21 meter. Tunning from 40 meters till 10 meters. the way that I have put this antenna on, is: put my old cobra 148 GTL on AM achieve que maximum receiving, then ptt on, in AM and turn fine tunning until the SWR 1:1 or 1:2. Then change to SSB, could use it in js8call, and voice, in voice, the high QRB was 5600 Klm with 10W, inside my attic. The MAG loop is very sensitive, and change SWR up 3 channels or down. So when you acchiev que maximum rx, make a TX and turn you fine tunning to achiev the minimum SWR. 7351 an good contacts.

[@alanbond1269]

Thanks for sharing Fred it's great to play and try new things. Your doing a real world test. That's how we learn. It could be the tripod acting as a antenna. Always enjoy your radio videos

[@CB-RADIO-UK]

Thanks. Not really sure about the tripod effecting the SWR. I did use the loop up a fibreglass pole and the SWR was about the same.

[@alanslade2319]

Cheers Fred love watching your show, most interesting stuff cheers for that, looking forward to seeing the next show cheers 👍

[@CB-RADIO-UK]

Thanks. Really appreciate that. 👍

[@SimonBlandford]

I have a similar magloop except mine didn't come with a balun, just some RG58 coax with a torroid at one end, which kinda sortof acts like a balun. Being on a 4th floor flat I can only use it indoors but have still managed to get HAM contacts with the USA and all over Europe on 10W using FT4/8. No voice contacts yet. I found the best way to tune it is to put the bottom (load) control in centre and tune the top control while listening on SSB for the background noise peak. Then transmit on low power and tweak the top then the bottom controls recursively until the SWR is sane, usually less than 1.5:1, with a bit of practice. Then raise the power and check again and fine tune if necessary. I probably wouldn't use it outdoors for transmit because I know a straight vertical or wire would do so much better, but for listening or indoors/balcony its great. Also good for listening to the CB band on an SDR because it will attenuate the strong, local MW stations out of the box, since they are so far away from where it will be tuned.

[@CB-RADIO-UK]

Thanks for the info. The best feature of the loop is how it rejects noise. Once i got the SWR 1-1 its receive on 11m was very sharp esp on FM. SSB was trickier and although height improved its range it brought in a lot of noise so really needs to be used out in the open.

[@ianwalker1182]

The loop looks like Heleax co-ax with PL259 plugs on the ends, with the inner unused.

[@bill-2018]

To those who say it's not a proper mag loop because it doesn't have the smaller loop, be aware they can be fed inductively with a smaller loop, capacitively like this one or by tapping up the loop. I made a loop and tried inductive and tapping up the loop for matching, so that must be a Gamma match. I'll go to part 2 to see how you go on with it. G4GHB.

[@billmorrison4746]

Will follow with interest

[@stoatrepublic]

Wow, what a cliff hanger, I need to see the rest of this...

[@CB-RADIO-UK]

Just stay tuned. It will be across a few weeks though.

[@321CatboxWA]

Looks like a two person tune up . Good luck . I expect the dip is going to be very narrow in range on the dial . 73

[@CB-RADIO-UK]

Yes very narrow indeed.

[@Legend813a]

Oh man... those SWR recalibration times... That poor final.

[@CB-RADIO-UK]

Yeah i know :-(. I used an older CB radio for the testing.

[@W4TRI_Ronny]

The feed looks nothing like a classic loop with the 1/5 ratio feed loop. I'd love to find out how this is being fed.

[@CB-RADIO-UK]

Yes i did wonder about the smaller induction loop missing. More like a receive antenna.

[@Tobinindustrial]

Hello Fred. This is a very interesting issue. I am really looking forward to the next installment. Hopefully, the company can suggest a remedy for this.

[@CB-RADIO-UK]

Thanks Andy. They dont respond and its left up to me to work the problem.

[@thestonerguy5276]

This is similar to a few low end MFJ loop antennas boxes I've seen, but I don't believe they are true magnetic loops. It appears to have either 2 adjustable capacitors, or more likely, one adjustable capacitor and one adjustable inductor, along with a Balun. The MLA's I'm familiar with have the large loop, the smaller pickup/transfer loop, and an adjustable capacitor (no Balun). I have my MLA indoors on the first floor and generally have decent performance on 11 meters. 5 - 15 miles local (SSB) and when the skip conditions are strong, I get my fair share of contacts, using only 5-10 watts. At that power level, and if sitting parallel to the null of the loop, there aren't any worries about my body absorbing too much RF, even with it only sitting) 3 feet away (on a Tripod as well). With two knobs and the Balun, it seems much harder than it should be to tune the loop. I have only 1 knob to adjust (capacitor), and depending on the band, get 1:1 to 2:1 readings on my both my SWR meter and antenna analyzer. I'm really looking forward to Part 2, and hope you crack the boxes open so we can see what's inside. The one MFJ model I picked up at a hamfest had 2 knobs as well. When I cracked it open, I saw one knob controlling a capacitor and the other one adjusting a coil. Thanks again for carrying the torch onward for 11m folks like myself.

[@CB-RADIO-UK]

Thank you for the information. Interesting subject.

[@ronleblanc9832]

looked on banggood $116.66 canadien going to read the 6 reviews

[@W4TRI_Ronny]

Is your tripod part of the antenna where it could be isolated?

[@CB-RADIO-UK]

The loop control box attaches via a nylon collar but it could be effecting the loop yes.

[@Davejazz]

Are u ok.😊?? Havent seen any new videos of late

[@CB-RADIO-UK]

Hi. Yeah all good. Been uploading once a week as per usual.

[@befree2771]

You would benefit from a nano-vna. You could see your tuning progress in realtime.

[@CB-RADIO-UK]

Spot on.

[@gtretroworld]

I was waiting for this to show it’s face again Fred.I’m guessing you will have to internally tune those Caps to get this on 11m.

[@CB-RADIO-UK]

Hi Yes. Out of the box it tunes to 23 MHz or 12m. Adjustment was required. Interesting little antenna.

[@alecsimages1]

Interesting! You would love my setup:- Thunderpole 1.55mtr HD springer (Orbito HD) on a Tunderpole truck mirror mount with ground plane on a aluminium pole horizontally fixed off the house eves. swr is tuned perfectly, less than a needle width of movement, near enough 1.1. I"ll email you a photo if thats possible?

[@CB-RADIO-UK]

I think with radio its whatever works. Not everyone can put up a 18 foot antenna. Ive seen some great wire antennas hidden inside trees.

[@GordonHudson]

​@@CB-RADIO-UKI make intercontinental contacts on 12m using a dipole in the loft and 10w of power. I have an Amateur Radio licence but that example isn't far off CB in frequency and power. Look forward to seeing the next part. By the way, those capacitors would be too low voltage for even a QRP mag loop if it was fed by the normal method. This looks like a different arrangement.

[@CB-RADIO-UK]

Hi. Yes those caps are very small just am/fm radio tuning caps. I think 10w is the upmost (just) you can run through it. I dont know where they get 20 watts from.

[@davidbrowne1588]

Hi the small box is not a balun it is a choke to stop common mode current on the outside of the coax going to the radio To stop rfi, and misreading swr, Dave, these loops do work as a i have used one with 5w on 20m to spain, and the loop was in my upstairs radio lab, Try tunning it like you would with a tunner, if you have AM on that radio it would be best to switch to that and peak for max noise Dave 2E0DMB

[@kishascape]

I used a magic loop on the back of my CB before and it worked great.

[@bertcb1gwn909]

I don't have a loop. I think Set the channel Tune in to max peak.(with Smeter) Then set the swr. Now waiting for part 2 and 3 if i am right.

[@CB-RADIO-UK]

Yes spot on with the tuning. There will be 3 parts to this series over the coming weeks.

[@ammocraft]

Can you open up the other box so we can see what it is? Would be good to see the internals and the windings. 👍

[@CB-RADIO-UK]

Yes i could on a future video. It was opened on another video and is just a small doughnut ferrite.

[@ammocraft]

@@CB-RADIO-UK Just interested in seeing the windings to see what it is.

[@19TC504]

I think you need a tuner for this one not sure tho i dont know this one

[@CB-RADIO-UK]

See part 2.

[@sudberceni257]

A radio station from Romania is heard, I think it is Radio Romania Actualitati

[@mikebolton5577]

Hi Fred Love your informative videos. Do you have a web site or Facebook page?

[@CB-RADIO-UK]

Hi. No sorry Iam only on KZbin with 2 channels.

[@manofkentcatapultsgunsando5069]

Interesting 👍

[@CB-RADIO-UK]

Thanks for the visit

[@SX939]

This type of antenna is very narrow band. You are not tuning it correctly, these work perfectly fine in the Amateur Radio Bands and 11 meters. 73 KV4WM, Dennis An Amateur Radio Extra Class Operator and US Navy Nuclear Submarine Veteran.

[@CB-RADIO-UK]

Yes they are very narrow. This model needs some adjustment to work 11m. You will see this in the next video.

[@mariusz9333]

use low-loss cables. The RG -174 and RG -58 cables are not suitable for this antenna. 73

[@rttakezo2000]

Army loop

[@CB-RADIO-UK]

Not sure. Different design than a normal loop design.

[@grahamrdyer6322]

Thats Not a proper Mag Loop.

[@CB-RADIO-UK]

Its different as it does not have a 2nd induction loop. More like a receive antenna but it does transmit.

[@bill-2018]

There's various ways of feeding a loop, inductively, capacitively or tapping up the loop. G4GHB.

[@bill-2018]

Why would you not transmit and calibrate into a 50 Ω dummy load? You know then the calibration is correct for 50 Ω. You could be trying to tune and calibrate into a 100 Ω or any impedance. G4GHB.