Co-phase amplifiers?

[T23]

I wansn't expecting this kind of response, I thought the thread would be dead....

Good note on the correct terminology Kw, I thought the same as some others that the "Co" part just meant "2 or More". And who says this was in reference to a "C.B amp"? Those are just amps marketed for other simular purposes that just happen to work on 11m...

Heh... Heh..


T23

 

[dxhound]

When cutting coax lines for phasing purposes, don't forget take into consideration the velocity factor of the coax.

Velocity factor wont matter much as long as both leads of the T are of the same type and length.

 

[vo1ks]

Velocity factor wont matter much as long as both leads of the T are of the same type and length.

Cable impedance and length are both critical to make a phasing harness work properly.

Perhaps the easiest 4-way splitter uses 50 ohm cable and three Tee connectors. One Tee feeds the other two with quarter wave lines. With two 50 ohm loads on the output Tee, its impedance becomes 25 ohms. The quarter wave 50 ohm line transforms it to 100 ohms. Two parallel 100 ohms becomes 50 ohms at the input. The four outputs can then feed amplifiers, antennas, etc. On the other end, the same thing can be used to combine the signal. This type splitter is common on Sinclair 4-dipole VHF/UHF antennas. The lines to each antenna are usually equal length, but can be staggered to provide beam tilt if required.

A 'ratrace' splitter / combiner can be made with 50 ohm coaxial cable and four Tee connectors. Two inputs/outputs with better isolation. Check the 180 degree hybrid couplers on this web page.
Hybrid Couplers - Microwave Encyclopedia - Microwaves101.com

 

[dxhound]

Cable impedance and length are both critical to make a phasing harness work properly.

Perhaps the easiest 4-way splitter uses 50 ohm cable and three Tee connectors. One Tee feeds the other two with quarter wave lines. With two 50 ohm loads on the output Tee, its impedance becomes 25 ohms. The quarter wave 50 ohm line transforms it to 100 ohms. Two parallel 100 ohms becomes 50 ohms at the input. The four outputs can then feed amplifiers, antennas, etc. On the other end, the same thing can be used to combine the signal. This type splitter is common on Sinclair 4-dipole VHF/UHF antennas. The lines to each antenna are usually equal length, but can be staggered to provide beam tilt if required.

A 'ratrace' splitter / combiner can be made with 50 ohm coaxial cable and four Tee connectors. Two inputs/outputs with better isolation. Check the 180 degree hybrid couplers on this web page.
Hybrid Couplers - Microwave Encyclopedia - Microwaves101.com

Hes talking about combining two amplifiers. As long as the load equals 50 ohm for both amplifiers and both leads heading to the T are equal lengths (phase matched), then the velocity factor will not matter. Velocity factor would come into account if you were using different types of coax or feed and they were going to be different lengths. It doesnt matter at what point in time the signal arrives at the T, as long as they are the same Deg.

 

[vo1ks]

Hes talking about combining two amplifiers. As long as the load equals 50 ohm for both amplifiers and both leads heading to the T are equal lengths (phase matched), then the velocity factor will not matter. Velocity factor would come into account if you were using different types of coax or feed and they were going to be different lengths. It doesnt matter at what point in time the signal arrives at the T, as long as they are the same Deg.

Maintaining equal phase in the cables is only part of the problem. You also need to maintain proper impedances throughout.

Without proper length cables, the input impedance to the Tee connector will not be 50 ohms. You need to transform each 50 ohm input on the amplifiers to 100 ohms. To do this you will need two quarter wavelength 70.7 ohm cables. 75 ohm cable is often used instead. The two in parallel will become 50 ohms. Cable length is critical, and velocity factor is needed to calculate a quarter wavelength in the cable.

 

[dxhound]

Maintaining equal phase in the cables is only part of the problem. You also need to maintain proper impedances throughout.

Without proper length cables, the input impedance to the Tee connector will not be 50 ohms. You need to transform each 50 ohm input on the amplifiers to 100 ohms. To do this you will need two quarter wavelength 70.7 ohm cables. 75 ohm cable is often used instead. The two in parallel will become 50 ohms. Cable length is critical, and velocity factor is needed to calculate a quarter wavelength in the cable.

Yes we are on the same page, Thats why I said maintain proper load....hence each amplifier seeing a 50 ohm load