MAGNETIC LOOPS: WELL OVER PRICED?

JUST BUILDING/COMPARING THEM FOR FUN: TESTS NOW FINISHED SO CLEARING THE LOT, TEST/COLLECT ONLY FROM SOUTHAMPTON:

CHAMELEON LOOP PICTURE AS BELOW:

ALEX LOOP LOOP PICTURE AS BELOW:

AND A FEW OTHER HF LOOPS:

Some years ago RFCOMMS designed a loop which was helically wound and was matched with Ni/Zn cores that needed no matcher or tuner. It was designed for overseas HF commercial users for in Country use for up to 2000 kms and could be used with 125 watt pep ssb ALE commercial transceivers and could operate between 4 and 18MHz for day/night operations. After many months of ALE tests the unit was accepted as a good replacement for the TF2D wideband 0 > 30MHz antenna system which including the masts for mounting was in the region of $2500. The Helical Loop was a fraction of the price of the TF2D and is now made overseas for commercial HF users.

Some years later and now we see several manufacturers producing various loop antennas for Amateur Radio use. We have a selection of 7 to 30MHz units by “Alex Loops”, “Chameleon”, “Alpha” and a Chinese variant. These units are rated at a maximum power rating of 25w pep. The cost of the big 3 above are astronomical for a unit that can only be used at 25w MAX.

EG: USA prices and UK prices

CHAMELEON ANTENNA CHA P-LOOP 2.0

Antenna, Loop, Portable, 3.5-29.7 MHz, 25W SSB, 36 in, Upgraded Tuning Box, Duffel Bag, Part Number: CHA- P LOOP 2 including tripod

$649.99 + UK  VAT @ 20% = $780 for a 25 watt antenna!


ALEX LOOP A HamPack Portable Magnetic Loop Antenna System 

Alex Loop, Portable Small Magnetic Loop with Bag for Antenna, Tuning Scale, AlexTune LED Indicator, 40-10M, 25W SSB, Tripod extra.

$599.00 + UK VAT @ 20% = $718 for a 25 watt antenna!


So why are these units so expensive? there is certainly nothing in the build that warrants the retail price.

Above is the Chinese QRP loop, 25w pep max, a solid loop possibly like Andrews LDF?, 0.625 inch or about 16mm dia, loop dia 28 inches (70cms), lightweight. Retail cost around £100 > £150 + shipping and plus tripod cost.

Chinese loop on the Wifes’ “Lazy Suzy” so it can be rotated for best S/N ratio/directivity

A QRP 7 TO 28MHz LOOP

So here is my homebrew version HF TX/RX QRP, 7 to 28MHz 10 watts pep and the TRUE cost, built in a couple of hours and superb for general HF receiving as well. It is a little critical for TX tuning/vswr as this build has no slow motion drives fitted. By using cable glands (replaced with metal versions) on the side of the enclosure the loop can be tilted to a vertical position rendering it useable on a table top. A great bit of kit for approx £35 (build it yourself)

Below: New metal cable glands fitted for more rigidity and waterproofing

Drop the loop into a tripod or fold it up for indoor table use

BOM (Bill Of Materials re-costed) Approx prices  in GBP:

10 mm copper tube 7 feet long: 28″ dia (70cms) or use coax cable £8.00:

Enclosure £3.50:

2 x 10 mm Cable Glands £8.00: Replaced plastic glands with heavy duty copper versions

2 x 280+280 pf Poly-varicon capacitors £7.50: or buy from Spectrum communications UK

Double pole toggle switch £1.50:

2 x Knobs £2.00:

SO239 socket/screws etc £2.50:

Total Approx £30.00 – £35: 

Above: SO239 input (Right): Switch is down for 14/18/21/28MHz and up for 7 to 10 MHz: Bottom tuning cap is input matching and top cap is tuning.

True sweeps below of 7/14/21/28MHz Amateur Bands 22/9/2022:


THE 100 WATT 7 – 28 MHz MAG LOOP

Now building the 100 watt version with a wide-spaced Butterfly capacitor

TA1LSX CAPACITOR KITS “CLICK THIS LINK”


A QRP 50MHz MAG LOOP

A 50MHz Mag loop for QRP (20w pep) This was made in a couple of hours, it uses a butterfly capacitor, the loop is again mounted through 2 cable glands and the Faraday loop uses velcro to the main loop, a slow motion drive is fitted and an RF monitor meter. Total cost excluding tripod and RF meter is about £35 (the capacitor is the most expensive item) THIS IS SO SIMPLE TO BUILD YOURSELF

Super sweep and can be tuned anywhere on 50MHz: Best dx so far is 60 miles as we have no “ES” (Sept 2022)

UPDATE: 2023: MAY/JUNE: 50MHz dx now wkd includes 9H1(Malta), 9A (Croatia) EA/I/IT9/IS0/C3/YO/HG/EA6/EA9 and lots more


THE 100 WATT 50MHz MAG LOOP

Now building the 100 watt version with a wide-spaced 25pf Butterfly capacitor rated at 6.5kv, now in the enclosure and fitted with vernier slow motion drive.

Faraday loop fitted

Good sweep but just a few mods to do and then test outside

MAY/JUNE 2023: Wkg superbly with just 20w all over Eu no problem at all

ALEX LOOP AND CHAMELEON P LOOP: £100 ea COLLECT ONLY: BOTH SOLD AND COLLECTED: