G0KSC SC6-4-4DQ 4el 50Mhz/70Mhz Dual band OWA Quad Antenna with a 2.7 Metre Length Boom

About this Antenna

This is a dual band Quad for both 50Mhz and 70Mhz which has just 4 sets of spreaders which each hold a quad element for each band. There are two feed points too, one for each band.The spreaders have been spaced in order to bias the best front to back upon the 50Mhz band and more gain bias upon the 70Mhz band. 

As with most of my antennas, both driven elements provide a 50 Ohm impedance to direct coax connection with no matching unit (or 1/4 wave lengths of coax of another impedance).

This is a great performing antenna for such a short boom length. Very light weight too. Enjoy!

SWR and bandwidth

As we are using a common set of spreaders the SWR can not be as flat as with a single band 50 Ohm quad.

Sizing and spacing are as follows:

Dimensions in Metres

Element spacing:

• Ref      =     0
• Driven  =    1.198
• D1       =    1.758
• D2      =     2.752

Element sizes per element half:

• Ref 6     =      6.288
• Ref 4     =      4.492
• Driven 6 =      6.096
• Driven 4 =      4.412
• D1-6      =       5.552
• D1-4      =      4.332
• D2-6      =      6.016
• D2-4      =      4.232 

Performance figures @ 50.250Mhz:

• Froward Gain: 9.64dBi free space
• Front to Back: 21.08dB
• Radiation angle at 10 Metres above ground: 10 degrees

Performance figures @ 70.250Mhz:

• Froward Gain: 10.41dBi free space
• Front to Back: 12.04dB
• Radiation angle at 10 Metres above ground: 5 degrees

Element diameter:

This model is created with 2mm thick copper wire

For construction information see 'G0KSC insulators' and the UKSMG article from the main menu on the home page. 

G0KSC SC28-6DS 4el 28Mhz/50Mhz Dual band Mini Yagi Antenna with a 2.708 Metre Length Boom

About this Antenna

This is a dual band short Yagi for both 28Mhz and 50Mhz. The antenna consists of 2 elements (reflector and driven element) for 28Mhz and 2 elements (driven parrasitic and director) for 50Mhz. With only 2 elements on each band and being very short, the gian figure is low along with that of the frotn to back ratio. However, there is still good gain over a dipole on either band and a great starter project in this antenna for the novice.

There is only one feedpoint which is at the center of the smallest 28Mhz element which should maintain it's length but have a 10mm section cut out of the centre and the feed line connected at this point.

NO Matching Device is required for this antenna as it has been designed with a 50 Ohm impedance at the feed point for both bands.

All tubing is 1/2inch diameter aluminium tube.

Sizing and spacing are as follows:

Dimensions in Metres

Element spacing:

• Ref 28     =     0
• Driven 28 =     1.914
• Driven 6  =      2.007
• D1-6     =        2.708

Element sizes per element half:

• Ref 28     =       2.584
• Driven 28 =       2.446
• Driven 6   =       1.45
• D1-6      =         1.365

Performance figures @ 28.500Mhz:

• Froward Gain: 6.71dBi free space
• Front to Back: 9.35dB
• Radiation angle at 10 Metres above ground: 17 degrees

Performance figures @ 50.250Mhz:

• Froward Gain: 7.82dBi free space
• Front to Back: 12.72dB
• Radiation angle at 10 Metres above ground: 10 degrees

Element diameter:

Each element is made out of single piece 1/2 inch (12.7mm) aluminum tubing Each element half length needs to be doubled in order to gain your total element size. No difference is length needs to be calculated for the 1inch or 1,1/4 inch boom as the elements sit high enough above the boom for the boom to have no influence.

NOTE:

You can build this antenna with 13mm diameter tubing using the same parameters above. Slightly higher front to back ratio and forward gain will be seen along with a narrower SWR curve. 

For construction information see 'G0KSC insulators' and the UKSMG article from the main menu on the home page.