PW has done a new review of my 2 models of antennas. click here to see the review
The following email had some questions.
I provided answers in red
I felt the quetions and answers might be useful
A few answers below in red
Just wanted to let you know I assembled the ML40 and it indeed "hears" well, and SWR is (as promised) very flat across the band (less than 1.2:1 for the entire 40m CW portion and most of the phone portion, and
not more than 1.3 even at the upper end of the phone portion. That's really excellent behavior--very well done on the matching unit! Thanks for these comments
Too early to tell how well it's working as a radiator: initial QSOs have given me weak sig reports, but this may be due to poor band conditions. 40 m conditions here have been very poor lately. Will keep experimenting.
The following table from a Computer programme may help to understand the efficiency of Magloops (as compared to a frequency cut dipole) (I have never been able to test or prove/disprove these figures so only taken as a guide)
Band No. Rails efficiency Loop Size
40m 10 22% 1.275 m
20m 10 76% 1.275 m
20m 7 53% 900mm
10m 7 94% .900mm
As you can see the size of the loop is very important in the performance so on 40m performance can not expect to be as good as a dipole.
To have 92% on 40m would require a loop with a 4.5 m diameter
To that end, a few more questions if I may (sorry to pester):
a. Are the Tune and Load units "weatherproof" (ie.., can I leave them outside in rain or snow), or do I need to seal the units in some way? The instructions weren't clear on this point... (I'm already sealing the coax connection to the Load unit...) Not really designed as a permanent antenna but as a portable, Best to silicon all joints and clean rails connections periodically.
b. Your instructions say to mount the loop with the lower edge "one foot above ground". I've read posts from other hams who've used mag loops (not necessarily *yours*) who raised their loop higher--as much as 2 meters above ground. Have you (or your other customers) had any experience with this--any insight on whether additional height improves or hurts performance? Of course I can experiment on my own but I'm curious if you have any reports on this point. Height does not make any difference when hung Vertically. If hung horizontal then height may help. (I hang horizontal in my 2nd floor apartment in Spain)
c. Similarly, I've read some posts where loop owners added ground radials or a counterpoise in an effort to reduce ground losses and improve performance. This de-tunes the antenna and although I have tried this it has no effect on improving the performance. Also there is a misconception about ground losses in a Magloop. Magloops radiate magnetic energy which is reflected by the ground thus improving performance. Electrical energy as from a dipole is absorbed thus height helps with non loop antennas. Dipoles need to be high to offset ground absorption but being close to the ground enhances the radiation of magloops. Again I can experiment, but I'm curious if you have any experience or customer reports on this point.
In short, your unit is a GREAT receive antenna/listener, and you advertised truthfully: once tuned, the SWR is indeed low across the band. Now I'm trying to understand how to get it to put out the strongest possible signal, so any thoughts on height and ground plane would be appreciated. The development I have done with the load unit makes the antenna broad band and also reduces the electrostatic energy across the capacitor thus I am able to use such a small air spaced capacitor and handle 100 watts SSB
Many of the these things I have explained go against current antenna theory so you may find people think this is crazy,. The proof is in the log book of contacts made with a G4TPH Magloop
In any case, thanks for your good service and great product design. That's all part of this great hobby
Frequently Asked Questions
Why are the G4TPH Magloops able to cover a Ham band without re-tuning?
I have spent a great deal of time and money experimenting with the inductive loading units.The new designs act a bit like a unun bringing down the inductance of the resonant circuit.This allows a wider tuning range with a low SWR across the band.The tuning is still very sharp at the actual resonant frequency.The results is a very low SWR at the resonant frequency (1:1 to 1) and a reasonable SWR across the whole of the band (usually around 1:5 to 1, band edge to band edge).
Do I need a tuner?
No need to use an ATU with the G4TPH Magloops. The Magloops is a tuned resonant circuit once tuned for the frequency of operation. A ground or counterpoise is not needed for the same reason.
How do I tune the Magloop?
To tune the Magloops for the frequency you move the tuning unit knob to the position where the noise on receive is the greatest. Once this is done, check the SWR and adjust the tuning knob for best SWR. Moving the tuning knob just a very small bit will make the SWR worse or better so use very very small adjustments until you get the best SWR. I usually tune for the middle of the band and get an SWR of about 1:1 to 1. This will provide an SWR of usually 1:5 to 1 across the whole of the band without having to retune. This is one of the major features of the G4TPH Magloop antennas.
Can I use the Magloops in the loft?
The new Remote tune ML40 can now be fitted in the loft and tuned remotely. the ML40 MK11 manual tune is not recommended for use in the loft since to change bands requires access to the manual tuning unit. The antennas was designed to be portable, and fold down for convenient travel and to keep the price down has manual tuning.
Can I use the Magloops in a horizontal position?
The Magloops will work in an Omni-Direction if placed in a horizontal position and will work fine. I quite frequently use one hung horizontally from the ceiling of my workshop
How high off the ground should the Magloop be placed?
In a vertical position place the bottom of the antenna about 1 foot (400mm) above the ground. Height doesn’t really make much difference but position to other objects such as metal pipes or metal support will affect the SWR.
Will the Magloop work inside a house or apartment?
The antennas will work placed in front of a window providing the building does not have a large amount of steel beams in its construction. I have used the antennas lying on the bed in a hotel room since there was not a suitable curtain rail to hang it on. It worked fine. I have also tried to demonstrate the antennas at the RSGB’s National Hamfest but the building had so much steel in its construction I couldn’t receive hardly anything let alone work any stations. Be aware of “faraday cages”
Will the Magloop work as well as a dipole or Yagi?
Magloops antennas are known to be very good especially for their size. However: any antenna smaller than a dipole will not perform as well as the dipole cut for the frequency of operation. Some very high percentages for Magloops compared to a dipole are achievable. Obviously Magloops will not work as well as a directional multi-element antenna such as a yagi or quad antenna.
I have heard that Magloops are quiet. Is this true?
Magloop antennas are receiving magnetic RF not electrical and magnetic RF thus electrical inference can be a couple S points down on other types of antennas. At times I have not been able to hear a station with a dipole and have switched to the Magloop showing 2 S units down thus the noise was less and I was able to copy the station better.
Is the length of the feed cable critical?
I have used various lengths during development but have not noticed any problems with all of the different lengths used.
Does the tuning unit have to be at the top or can it be on the side or at the bottom?
The Magloop will work with the tuning unit top, bottom or on the side. Just remember to mount the Load unit directly opposite the tuning unit.
What power will the Magloop antennas handle?
The ML 40HP Mk2 and ML20HP Mk 2 models will handle 100 watts SSB, 50watts CW and 35 Watts Data modes. Any more than this may cause arcing in the capacitor and possibly damage the output of your rig.
How do the G4TPH Magloop antennas handle such high power when the capacitor tuning unit is so small?
The capacitor although small has adequate plate spacing to handle the higher power. The only other limiting factor is the inductive loading which can saturate and become hot if too much power is used. Should this happen reduce power and let the loading unit cool down. If you continue to operate when the load unit saturates the SWR will soar and may damage you rig. (this will usually only occur when the Antenna is not tuned to the operating frequency thus a High SWR. Always tune for best SWR on the frequency of operation.