Long after looking on a decent loop antenna for external receptions with the PL330 and while looking on Youtube i found this interesting loop. it is intended to be used in my now primary house on the outskirts of the Mt Olympus . The reason is due to many reasons:
There are some significant local noises coming manly from a mobile cellphone antenna and another unknown source . The one is heard as ignition type while the other as as like a shift carrier mixed with some noise
Wishing to get better in the results of other vloggers i have made a playlist. this playlist has been watched a few times before making the order
I have also noticed that the circuit introduced some 'router noise' as i cal call it
It is a shifted or freq agile noise carrier. It sounds as shifting buzzer as heard before the 2018 when my main radio was a ICOM R75. In SDR spectral view it is shown as an unstable noise carrier. most people advised that this is the problem if the stepped transformer available in ALL routers of the trade . Here is a photo as grabbed by one remote kSDR:
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in just 25 days i have received the parcel with a box typical to this product
This is what is included into the carton box: the loop antenna , he active loop tuner on the left and three cables: BNC-BNC jumper for SDRs , BNC-3.9 for shortwave radios and a USB C type adaptor cable
Plus a mini guide to in both Chinese an English and several afrolex leafs
The usage is very simple IN just seconds you can connect the metal circle into the base via the BNC plug socket and use one of these two cables to connect into the radio receiver or SDR.
IN work!
Its usage is very simple : Just turn on the pot and tune to to the desired frequency. in contrast to what i expected the antenna starts from the higher parts of the SW band and gradually tuning lower. The inside of the pack includes an active tuner that produces a frequency dependent Q with peaks as high as 20db in he 5 MHz.And more important the battery was drained when i tested the loop fir the first time. I had to immediately charge it with the cable included in the package
After long usage in just two hours i found it having several flaws. Im sure that it has noe been passed for control quality otherwise the QC could to put ot in the junk
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IN short these are my findings
Using radios (list not noticed in the video )
-High noise is introduced with power on
-Circuit leaks at power off. Conveyed and audible via the cable to any radio
-Strong spurious signals adjustable by the potentiometer
-once switched on there is a strong annoying noise from the loop circuit
-The tuning SNR is lower than radio's telescopic antenna!
-Rotating the loop 15 degrees clockwise from the circuit box axis can remove most of tuner noise The female BNC base is a bit loose.
-I Prefer to rotate the whole system for removing the noise. this si the only part that works OK with this system !
-BY chance scanning on the MW band i found a typical 'router noise' existing on 15xx kHz with switch off
Also noticed with my SDR:
-Low Q in the top of the band Zoomed out can show hundreds of spikes most of them are from my PC .At least 3 meters far are needed to get rid of them.
-Two Image peaks while tuning the circuit in addition to the tuning peak-as i tuned below the 8 MHz or in 7-8 o clock
-Tunes only between 4.36 to 20 MHz .
-Harmonics up to 90MHz (!!)
Radios used : PL550 / PL330 and RSP1a SDR
And a few more screenshots :
Here si the SDR equivalent for the power leakage while the antenna tuner is turned off. I can find these 'noises' while using any radio with ATTenuator OFF These signals are quite low
Some closeup on the higher part with some test details
This is a scanner picture that shows the harmonics produced by the antenna tuner in the position of "6 o clock" Please Left Click for watching the full sized screenshot
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I have made a few videos posted in my Youtube account and also notified the seller for these problems. He responded that the company is off due to a national feast so i have to wait sometime.
https://youtube.com/playlist?list=PL9gILW4OYgSEU4bNWIGP-ULt9AMbTOT2v
The first 7 videos are my own 3 made on as 4/6/22 with SDR in mind on the centre of the city while 4 more added on 7/6 in a more clean place .
The above list was also posted before 4/6 in the comments under the remain vloggers pages for asking comparative results. After 5 days I received the first reply:
Hello My Radio Friend,
You should try your GA-450 antenna outdoors it is quite sensitive to QRM indoors.
I tried it on several Sony ICF-2001D, Tecsun PL-880 receivers outdoors with no problems.Indoors on my Vintage receivers it depends in which room of the apartment I am located.
I live in a building from the 1960s, in a small town and a trial in the countryside far from sources of electrical pollution would be worth trying.
Maybe also, look at the side of the computer power supply, sometimes switching power supplies create disturbances...
Try to put several ferrite cores on the coax of the antenna and on the cable of the PC...
Well, I'm really sorry that I can't give you more information about these problems.
Let me know if going outside solves these problems.
I wish you good luck, 73's, Friendships at the Household and see you soon.
Indeed he was right only for one : the sparks. Just putting the antenna around 3 m far from the laptop the sparks nearly diminished but all other 'flaws' remained. I can believe that the item didn'y pass the QC I will also follow his guidance to do the outdoor test
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Update:not so much later I have bought a new one from amazon de that form a Chinese seller but different from the above . It came in just 11 days . I immediately tested the battery before operating it. It was also drained as with the previous pack. I left the interface charged for around 15 minutes an immediately made my comparisons. The first was to check what happens with the interface in medium waves
In short the loop operates quite better with the same noise level as the first but:
- Q levels are quite lower than the first with up to 25 db of gain That means also that the tuned bandwidth is broader. (2.5/5)
- Noisy as the other after switching ON the interface (2/5) I think that they have replace the FETs with other model that has lower internal noise.
- Lowest frequency is roughly the same at 4300 kHZ (OK)
- The interface in off duty produces high noise on MW that covers all the MW band Once again the interface leaks unnecessary battery power and can drin it in short time (2/5)
- Does not tune on MW but as loop it can remove nearby noises, (4/5)
- The RSP spectrum analyzer shown NO harmonics above the 30 MHz! (5/5)
- In short the loop is quite better with minimal problems comparing to the previous. Objective Verdict 3/5 but comparing to the previous yields 4/5
- MY proposal is : (1) replace FETs with others with lower internal noise (2) recheck all stages for any power leakage.
Full visual report is here - no comments just tuning the SDRplay across the bands It is also added in the playlist mentioned above:
https://www.youtube.com/watch?v=cQcxIQz4mxM
I m now thinking to return the first loop for the quest of money.
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Two days after thinking to return the first loop i tested it once again. I fist charged the interface for around 15 minutes as the time passed and he inner system leakage drainer its battery. Immediately used the SDR uno as testing program
i was very well amused that the loop behaved exactly as the second! Checking if i used a wrong interface was mistake as in the firsrt loop i used a tape marker to separate from the other - no tape-
I really wonder what this can mean ... it that behaving as ...human??
the only minus is the strong noise introduced by the circuit
