Log-Periodic Antenna from the Netherlands for 27 MHz to 100 MHz

GB Antennes is a company in the Netherlands that sells a wide range of antennas including a log-periodic antenna for the low VHF band. The model pictured above is the GB Log-Per 9elm TX 27-100MHz Custom made Antenna.

Specs...

Frequency: TX 27-100MHz
Frequency: RX 24-140MHz
Connection: 50-52 Ohm coax cable
Power: 1.5kw PEP
Gain: 5.5dbd- 7.8dBi
F / B: 15-20 dbd
Maximum SWR: 1.6: 1
Wind load: 125kph
Turning circle: 2.75m
Elements: 9
Boom: 2 x 4.65m
Boom in 3 pieces total 6 pieces
Boom connectors: 4 x
Elements: 20-16mm
Boom diameter: 30mm
Insulator pieces PVC: 7x
Pole mounting Isolator piece tree PVC: 1x
Pole mounting: 2 x 52mm pipe clamps
Mounting bolts: stainless steel
Element clamps: stainless steel
Shipping box: 1x 1.60mx0.30x0.30cm
Weight: 19kg with packaging 22kg

It seems to be a pretty rugged antenna with elements ranging from 16mm to 20mm. The antenna also weighs 19kgs!

The photo above shows where the coax cable attaches to the two parallel bars used for feeding the log periodic.

The photo above shows the choke balun that goes to the feed point. The coax is an unbalanced feeder whereas the log periodic has a balanced feed point.

This antenna should have the performance of a 3-element Yagi over most of the low VHF spectrum but that performance over tens of MHz comes at a cost. This antenna currently retails at €675.

More info on the GB Antennes website... https://www.gbantennes.com/nl/gb-log-per-antennes/253-gb-log-per-9elm-27-100mhz.html

Thanks to Rob, PE9PE for the above link.

For more information on the 8m band, visit my 40 MHz page... https://ei7gl.blogspot.com/p/40-mhz.html

SMC Transportable Log Periodic HF VHF Antenna 30-88MHz

Whenever I come across suitable antennas for the low VHF bands, I try to keep a record of them here. I spotted this Log-Periodic beam recently on eBay...

This antenna is described as a 250w Transportable Log Periodic HF VHF Antenna 30-88MHz and it was sold in the past by SMC in Southampton, England.

As the photo shows above, it was probably destined for the military market.

Tactical, Anodised Green. SMC Part Number - TLP3088.

The specs above say it was 4m from the rear to front element and the gain was in the region of 6dBd. I suspect it was probably a bit less at around 5dBd but it would still be a fine antenna for anyone  monitoring the low VHF spectrum from 30 to 88 MHz.

Keep an eye on the second hand market.

Link... https://www.ebay.co.uk/itm/143924931851?ViewItem=&item=143924931851

Low Band VHF Log-Periodic Aerials from Antenna Products Corporation

Thanks to some info from Rob PE9PE, I came across this commercial antenna website in the USA ... https://antennaproducts.com/

Part of their wide range of products includes log-periodic directional antennas for the low VHF band of about 30 to 80 MHz.

The general principle of a log-periodic antenna is that they give a modest amount of gain over a very wide bandwidth as opposed to a typical Yagi which has more gain but only a narrower bandwidth.

While these commercial products are perhaps outside the budget of the typical radio amateur or scanner enthusiast, they do give some idea on the performance to expect from this type of antenna.

Some models...

Model : TLP-20 (pictured above)
Range : 20 MHz - 1000 MHz
Boom Length : 5.1m
Gain : Approx 2 to 6dBd
Link : https://antennaproducts.com/wp-content/uploads/2014/09/TLP-20-1.pdf

Model : LP-102
Range : 30 MHz - 88 MHz
Boom Length : 4.5m
Gain : Approx 5.4 dBd
Link : https://antennaproducts.com/wp-content/uploads/2014/04/LP-102.pdf

Model : TLP-28 
Range : 28 MHz - 100 MHz
Boom Length : 4.1m
Gain : Approx 3dBd
Link : https://antennaproducts.com/wp-content/uploads/2014/04/TLP-28100225.pdf

The website of the company is https://antennaproducts.com/

Commercial Log-Periodic Antenna for 30 to 70 MHz

One of the challenges of listening to Low Band VHF signals is having an antenna that performs well on a wide range of frequencies. One solution is the Log-Periodic antenna.

This 7 element Log-Periodic from M2 Antenna Systems is very much a high product aimed at commercial, scientific and commercial agencies rather than the hobbyist and probably has a price to match. It does however give some insight into that is required to cover the whole spectrum from 30 to 70 MHz.

Some notes and observations...

1) Boom... The boom is 157 inches in length which is about 4 metres.

2) Gain... Even though the Log-Periodic has 7 elements, the gain is very modest at about 4dBd. Note that this is true gain in free space and is honest. They haven't inflated the figures by adding on ground gain to make the antenna look better.

3) Compromise... The modest gain is the price of having a wide band antenna. With a 7 element Yagi, all 7 elements are in use and the gain may be up around 10dbd. With a Log-Periodic, only about 2 to 3 of the 7 elements are active at any particular frequency in the 30-70 MHz range.

4) Phasing harness... Note the phasing harness above the boom which goes back and forth between elements. This is part of the additional complexity of a Log-Periodic as opposed to a Yagi with its parasitic elements.

5) Balun... This antenna has a 4 to 1 Balun at the front and this performs two functions...
a) This is to match a balanced antenna to an unbalanced coax feed
b) It also transforms the 200 Ohm feed impedance of the Log-Periodic down to about 50 Ohms.

More information on the antenna can be found at the following link...

1) 30-70LP7 on M2 Antenna Systems website